1. An LED lamp including a pair of input terminal parts; a rectifier circuit unit rectifying an AC, inputted from the outside to the 5 pair of input terminal parts, to a DC; and an LED unit emitting light by electr5cation of the DC outputted from the rectifier circuit unit; the LED lamp having: a variable inductance unit, in a circuit between the pair of input terminal parts and the rectifier circuit unit, for causing the AC to flow 10 from one of the pair of input terminal parts to the other input terminal part through the rectifier circuit unit; a current detection unit, in a circuit between the rectifier circuit unit and ' the LED unit, for detecting a magnitude of the DC flowing through the LED unit; 15 . an inductance variable control unit for making an inductance value of the variable inductance unit variable according to the magnitude of the DC detected by the current detection unit; and a PWM control unit, in a circuit between the rectifier circuit unit and the LED unit, capable of PWM control of a current flowing through 20 the LED unit according to a duty ratio; wherein the PWM control unit is switchable between a case where the PWM control of the current flowing through the LED unit is performed, and a case where PWM control of the current flowing through the LED unit is not performed, according to a frequency of the 25 external AC inputted to the pair of input terminal parts; and .wherein, in the case where the PWM control unit does not performs PWM control, the current detection unit detects the magnitude of the DC flowing through the LED unit, and the inductance variable control unit makes the inductance value of the variable inductance unit variable according to the magnitude of the DC.

2. An LED lamp according to claim 1, further comprising a threshold element, in a circuit between the pair of input terminal parts and the rectifier circuit unit, for causing the AC to flow from one of the pair of input terminal parts to the other input terminal part through the rectifier circuit unit; wherein the threshold element is adapted to short-circuit both ends thereof after a lapse of a predetermined time from when the AC exceeding a predetermined threshold is inputted to the pair of input terminal parts from the outside; and where'in the inductance variable control unit makes the inductance value of the variable inductance unit variable according to the magnitude of the DC detected after the both ends of the threshold element are short-circuited.

3. An LED lamp according to claim 1 or 2, further comprising a circuit interrupt unit, in a circuit between the pair of input terminal parts and the rectifier circuit unit, capable of interrupting the AC flowing from one of the pair of input terminal parts to the other input terminal part through the rectifier circuit unit; wherein the circuit interrupt unit interrupts the AC when the magnitude of the DC detected by the current detection unit is higher than a predetermined upper limit or lower than a predetermined lower limit.

4. An illumination device including the LED lamp according to any one of claims 1 to 3.

5. A current control method of an LED lamp including a pair of 5 input terminal parts; a rectifier circuit unit rectrfying an AC, inputted from the outside to the pair of input terminal parts, to a DC; and an LED unit emitting light by electrification of the DC outputted from the rectifier circuit unit, the method comprising the steps of: causing the AC, in a circuit between the pair of input terminal parts and the rectifier circuit unit, to flow from one of the pair of input terminal parts to the other input terminal part by way of the rectifier circuit unit through a variable inductance unit; switching between a case where the PWM control of the current flowing through the LED unit is performed, and a case where PWM control of the current flowing through the LED. unit is not performed, according to a frequency of the,external AC inputted to the pair of input terminal parts, wherein the switching is performed by a PWM control unit, in a circuit between the rectifier circuit unit and the LED unit, capable of PWM control of a current flowing through the LED unit according to a duty ratio; detecting, in the case where the PWM control unit does not perform PWM control, a magnitude of the DC flowing through the LED unit in a circuit between the rectifier circuit unit and the LED unit; and making an inductance value of the variable inductance unit variable according to the detected magnitude of the DC in the case where the PWM control unit does not perform PWM control; wherein the magnitude of the DC flowing through the LED unit is controlled so as to fall within a predetermined range. Dated this 22" day of July, 2014. (Dev ~obinson) of Amarchand & Mangaldas & Swesh A. Shroff & Co. Attorneys for the Applicant

Title of Invention
LED LAMP, XLLUMINATION DEVICE INCLUDING THE LED
5 LAMP AND CURRENT CONTROL METHOD OF THE LED LAMP
Technical Field
[0001] The present invention relates to an LED lamp which can
stabilize the magnitude of a current flowing through an LED unit so as
to make it fall within a pxedetermihed range even when mounted in
place of a fluorescent lamp of a constant power regulation inverter type
lighting device distributed on the market, an illumination device
including the LED lamp and a current control method of the LED lamp.
Background Art
[0002] As typical lighting devices for fluorescent lamps (usually
referred to as fluorescent lights) used in general, there have
conventionally been lighting devices for various fluorescent lamps such
as those of the glow starter and rapid start types, which are also known
as magnetic ballasts, or the inverter type, also known as an electronic
ballast.
[0003] The inverter type fluorescent lamp lighting devices, which have
rapidly been becoming widespread in recent years in particular, are
devices which convert an AC into a DC and then cause an inverter
circuit constituted by a transistor, a capacitor, a choke coil and the like
to generate a high voltage at a high frequency (20 kHz to 100 kEb) near
a resonance fiequency.
[0004] The high voltage switches on the fluorescent lamp, and
thereafter a current flowing through the fluorescent lamp stably lights
the fluorescent lamp at a lower voltage.
[0005] This is superior to the conventional magnetic ballasts of the
glow starter and rapid start types using choke coils in terms of such
5 characteristics as lower power, higher efficiency, usability at both 50 Hz
or 60 Elk, lower noise and indiscernibility of flicker.
[0006] These will.now be explained with reference to the drawings.
[0007] Fig. 15(a) is a diagram illustrating an example of glow starter
type ballasts, Fig. 15(b) is a diagram illustrating an example of rapid
10 start type ballasts, and Fig. 15(c) is a diagram illustrating an example of
inverter type ballasts.
[0008] The glow starter type ballast illustrated in Fig. 15 (a), which is
the most popular type, preheats electrodes (also referred to as flaments;
the same hereinafter) of a fluorescent lamp with a starting device using
15 a glow starter (G), so as Yo enable lighting in a few seconds after
switching on.
[0009] The rapid start type ballast illustrated in Fig. IS@), which is
used in combination with a rapid start type lamp, is lit instantaneously
and simultaneously with preheating when switched on.
20 [0010] On the other hand, the ballast of the inverter type lighting device
illustrated in Fig. 15(c) converts an AC within the AC input voltage
range of 85 to 450 V into a DC and then causes an integrated circuit to
drive an LED Imp at a high frequency such as that mentioned above
(e.g. see page 4 and Fig. 2 of Patent Literature 1).
25 [00111 While a choke coil L is inserted in series.with the LED lamp in
order to smooth the current flowing though the LED lamp in this case,
an electrolytic capacitor (not depicted) is typically inserted in parallel
with the LED lamp.
[0012] Fig. 16 is a diagram illustrating an example in which two
fluorescent lamps are connected in series to a series rapid ballast.
[0013] This configuration, in which two fluorescent lamps are
connected in series and lit by a single ballast, is simpler and less
expensive than one using two single-lamp ballasts or a flickerless
ballast.
[OOLQ] When powered, the electrodes of each of fluorescent lamps A
and B are preheated, and the secondary voltage does not shift to normal
discharging but attains a weakly discharging state due to a starting
capacitor having a high impedance. The lowered voltage at both ends
of the starting capacitor caused by the weak discharge current is applied
to the fluorescent lamp B, and starts to discharge the fluorescent lamp
B.
[0015] When discharging occurs in both fluorescent lamps, the starting
capacitor at the high impedance is placed into a substantially
non-operating state, so that normal discharging is generated in both
fluorescent lamps, and a lit state is maintained.
[0016] Thus discharging lamps one by one in such a series connection
can light two fluorescent lamps in series at a relatively low secondary
voltage, but is disadvantageous in that both of the fluorescent lamps fail
to light when one of them is removed for power saving or has burnt out.
[0017l Meanwhile, as the above-mentioned ballast of the inverter type
lighting device (hereinafter also referred to as inverter type ballast or
electronic ballast), which is applied not only to LED lamps but also to
conventional fluorescent lamps, a constant current regulation type in
which the current flowing through the fluorescent lamp is controlled so
as to have a fixed magnitude and a constant power regulation type in
which the power supplied to the fluorescent lamp is controlled so as to
5 have a fijred magnitude have widely been known (see, for example,
Patent Literatures 2 and 3).
Citation List
Patent Literature
[OOPS] Patent Literature 1 : Japanese Laid-Open Patent Application No.
10 2010-34012
Patent Literature 2: Japanese Laid-Open Patent Application No.
2010-218961
Patent Literature 3 : Japanese Laid-Open Patent Application No.
2002-1 5886
15 Summary of Invention
Technical Problem
[0019] h recent years, for saving power, lengthening the life of lamps
and so forth, more and more LED lamps have been seen in use as being
mounted to various types of ballasts mentioned above in place of the
20 conventional fluorescent lamps.
[0020] In this case, the peak value and frequency of the AC inputted to
a pair of input terminal parts of an LED lamp greatly vary depending on
types of ballasts of lighting devices to be mounted therewith, which
makes it necessary to use respective LED lamps corresponding to the
25 ballasts.
[0021] Zn a glow starter or rapid start type fluorescent lamp lighting
device, for example, the output (secondary output) of the ballast is
controlled at about 200 V AC so as to correspond to the
power-supply-side input of 100 V to 240 V AC (50 Hz or 60 Hz), but
since the frequency is not controlled so as to become a high fiequency,
5 the frequency is the same as that of the power-supply-side input.
[0022] Therefore, in the LED lamp, an inner rectifier circuit rectifies
the AC to a DC, so as to enable use as an AC coinciding with the
hquency of the power-supply-side input, and then the circuit
configuration of m LED unit of the LED lamp (the configuration of a
10 circuit in which a plurality of LEDs are connected; the same hereinafter)
is fixed so as to yield a desirable illuminance, and the current flowing
tlirough each LED is made .to have a magnitude falhg within a
predetermined range.
[0023] Hence, when the ballast of the fluorescent lamp lighting device
15 is of the glow starter or rapid start type, it has conventionally been
possible for each LED incorporated therein to be lit by using a dedicated
LED lamp attachable to a lamp socket for a fluorescent lamp.
[O024] On the other hand, as mentioned above, even when the
power-supply-side input is 100 V to 240 V AC (50 IEEz or 60 Hz) in the
20 fluorescent lamp lighting device of the inverter type, the output
(secondary output) of the ballast has been controlled so as to become a
fixed voltage of about 280 V AC (under no load), and since the
firequency is under constant-current or constant-power control to faU
within the range of 20 kHz to 100 Eli, the circuit configuration of the
25 LED unit of the LED lamp is fixed so as to yield a desirable
illuminance, and the current flowing through each LED is made to have
a magnitude falling within a predetermined range.
[(I0251 Therefore, when the .ballast of the fluorescent lamp lighting
device is of the inverter type, it has been necessary to take
commensurate measures on the lighting device or LED lamp side that
5 involve changing the circuit construction on the lighting device side,
employ a conversion adaptor necessary for direct connection, or the
like, in order that the power on the power supply side can directly be
supplied to an AC/DC converter (rectifier circuit) incorporated in the
LED lamp bypassing (not driving) the inverter type ballast.
10 [0026] Furthennore, when lighting an LED lamp in the inverter type, it
has been necessary to replace the existing lamp with a set of a lighting
device, incorporating an inverter type ballast therein, and a dedicated
LED lamp.
[0027) As shown above, the need for selecting and deselecting
15 (verifying compatibility of) LED lamps according to types of lighting
devices, or performing additional operations such as circuit construction
and direct connection on the lighting device side, has caused users to
investigate the current state for implementation and construction, adjust
the construction period, and so forth, which are troublesome and
20 increase the implementation cost.
[0028] That is, these factors have been hindering LED lamps fiom
being employed in conventional fluorescent lamp lighting devices in
homes and offices.
[(I0291 As aresult,previous fluorescentlampscontinue to beusedas .
25 they are, thereby greatly obstructing market diffusion of LED lamps,
which can greatly contribute to saving power and lengthening the life of
lamps.
[0030] When an LED lamp is mounted to a constant power regulation
inverter type ballast, for example, the value of load impedance limiting
the current value flowing through the LED unit of the LED lamp may
5 be lower than that of the fluorescent lamp, thereby causing the inverter
type ballast to yield a lower output voltage and a higher output current.
As a result, the magnitude of the current flowing through the LED lamp
may exceed the predetermined range, thereby failing. to yield an
appropriate quantity of light.
10 [0031] For driving fluorescent lamps with various rated powers, there
are inverter type ballasts with various output voltage settings; depending
on kinds of these inverter type ballasts, the magnitude of the current
flowing through the LED lamp may fail to stabilize within the
predetermined range, whereby an appropriate quantity of light may not
15 be obtained. More specifically, the output voltage of the inverter type
ballast is fixed so as to be substantially proportional to the magnitude of
the load impedance of the LED lamp, while the output current fluctuates
in response to the magnitude of the output voltage. As a result, the
magnitude of the current flowing through the LED lamp may fluctuate
20 beyond the predetermined range, thereby failing to yield an appropriate
quantity of light.
[0032] It is therefore an object of the present invention to provide an
LED lamp, an illumination device including the LED lamp and a
current control method of the LED lamp which can stabilize the
25 magnitude of a current flowing through an' LED unit so as to make it fall
within a predetermined range by replacing a previously mounted
fluorescent lmp (or LED lamp) even when a ballast of a fluorescent
lamp lighting device is of a constant power regulation type.
Solution to ~roblem
[0033] The LED lamp according to the present invention is an LED
lamp including a pair of input terminal parts; a rectifier circuit unit
recmng an AC, inputted fiom the outside to the pair of input terminal
parts, to a DC; and an LED unit emitting fight by electrification of the
DC outputted from the rectifier circuit unit; the LED lamp having a
variable inductance unit, in a circuit between the pair of input terminal
parts and the rectifier circuit unit, for causing the AC to flow fiom one
of the pair of input terminal parts to the other input terminal part
through the rectifier circuit unit; a current detection unit, in a circuit
between the rectifier circuit unit and the LED unit, for detecting a
magnitude of the DC flowing through the LED unit; and an inductance
variable control unit for making an inductance value of the variable
inductance unit variable according to the magnitude of the DC detected
by the current detection unit.
[0034] This LED lamp can make the inductance value of the variable
inductance unit variable according to the magnitude of the DC detected
by the current detection unit by replacing a previously mounted
fluorescent lamp (or LED lamp) even when the ballast of the fluorescent
lamp lighting device is a constant power regulation inverter type ballast,
whereby the output voltage is fixed so as to be substantially
proportional to the value. As a result, the magnitude of the current
flowing through the LED unit can be stabilized so as to fall within a
predetermined range.
[0035] When the magnitude of the current flowing through the LED
unit is lower than a predetermined range, for example, the magnitude of
the current flowing through the LED unit can be stabilized so as to fall
within the predetermined range by utilizing the fact that lowering the
5 inductance value of the variable inductance unit decreases the output
voltage and increases the output cunent of the constant power control
inverter type ballast. When the magnitude of the current flowing
through the LED unit is higher than a predetermined range, on the other
hand, the magnitude of the cwrent flowing through the LED unit can be
10 stabilized so as to fall within the predetermined range by utilizing the
fact that enhancing the inductance value of the variable inductance unit
increases the output voltage and decreases the output current of the
constant power control inverter type ballast. That is, desirable effects
can be obtained by utilizing such a characteristic of the control system
15 as to supply a constant power to the LED lamp in the constant power .
control inverter type ballast.
[0036] In addition to the foregoing configuration, the LED lamp of the
present invention may further include a threshold element, in a circuit
between the pair of input terminal parts and the rectifier circuit unit, for
20 causing the AC to flow fi-om one of the pair of input terminal parts to
the other input terminal part through the rectifier circuit unit; wherein
the threshold element is adapted to short-circuit both ends thereof after a
lapse of a predetermined time &om when the AC exceeding a
predetermined threshold is inputted to the pair of input terminal parts
25 fiom the outside; and wherein the inductance variable control unit
makes the inductance value of the variable inductance unit variable
according to the magnitude of the DC detected after the both ends of the
threshold element are short-circuited
[0037] For example, there are some kinds of constant power control
inverter type ballasts which, in order to grasp states of fluorescent lamps
5 (e.g. to check whether or not the fluorescent lamps are attached to the
load side) at the time of starting outputs, set the output voltage lower
than the rated value beforehand, cause a low slight current to flow that
is unable to obtain an appropriate quantity of light, and monitor the'
magnitude of the output current at that time, subsequently raise the
10 output voltage to a predetermined range, and then perform constant
power regulation.
[0038] In the foregoing configuration, however, both ends of the
threshold element are short-circuited after a lapse of a predetermined
time fiom when inputting the AC exceeding a predetermined threshold
15 to the pair of input terminal parts fiom the outside, and the inductance
value of the variable inductance unit is made variable according to the
magnitude of the DC flowing tkugh the LED unit after
short-circuiting both ends of the threshold element, so that, even in such
kinds of inverter type ballasts, only the current flowing through the LED
unit to be detected (the current in a normal lighting state) is detected,
without performing erroneous control.
[0039] In addition to the foregoing configuration, the LED lamp of the
present invention may further include a circuit interrupt unit, in a circuit
between the pair of input terminal parts and the rectifier circuit unit,
capable of interrupting the AC flowing firom one of the pair of input
terminal parts to the other input terminal part through the rectifier circuit
unit; wherein the circuit interrupt unit interrupts the AC when the
magnitude of the DC detected by the current detection unit is higher
than a predetermined upper limit or lower than a predetermined lower
limit.
[0040] Even when an overcurrent flows through the LED lamp because
of changes over time or some abnormalities on the ballast side, for
example, this configuration can block the AC inputted to the pair of
input terminal parts fiom the outside fiom flowing to the rectifier circuit
unit on the safe side. When the detected magnitude of the DC is very
low due to some abnormalities such as those in the state of mounting the
LED lamp to the ballast and electric connection failures, on the other
hand, the AC inputted to the pair of input terminal parts fiom the outside
can be blocked fiom flowing to the rectifier circuit unit on the safe side.
[0041] In addition to the foregoing configuration, the LED lamp of the
present invention may W e r include a PWM control unit, in a circuit
between the rectifier circuit unit and the LED unit, capable of PWM
control of a current flowing through the LED unit according to a duty
ratio; wherein the PWM control unit is switchable between a case where
the PWM control of the current flowing through the LED unit is
performed, and a case where PWM control of the current flowing
through the LED unit is not performed, according to a fiequency of the
external AC inputted to the pair of input terminal parts; and wherein, in
the case where the PWM control unit does not perform PWM control,
the current detection unit detects the magnitude of the DC flowing
through the LED unit, and the inductance variable control unit makes
the inductance value of the variable inductance unit variable according
---.. . . . . - .... ..-I----------' '- . , I ..-.. I... ..-.. --"---.A ------, ------..,.-. -.-----a -.-----.-.-.----.. .-I ---.... ... ....,.
to the magnitude of the DC.
100421 This configuration makes it possible to light the LED lamp for
iIlumination, which is capable of being lit by pulse-driven PWM
control, by replacing a previously mounted fluorescent lamp (or LED
5 lamp), regardless of whether a ballast of the fluorescent lamp lighting
device is of the glow starter, rapid start or inverter lighting type. When
mounted to the inverter type ballast, i.e. when the PWM control unit
does not perform PWM control, this configuration can stabilize the .
magnitude of the current flowing through the LED unit so as to make it
10 fall within a predetermined range.
[0043] In other words, when the frequency of the AC inpuaed from the
pair of input terminal parts is low, e.g. a utility power frequency of 50
Hz or 60 Hz, as in the case where the ballast of a fluorescent lamp
lighting device is of the glow starter or rapid start type, the PWL control
15 unit in the LED lamp acts to stabilize the current flowing through the
LED unit. When the frequency of the AC inputted from the pair of
input terminal parts is high, e.g. 20 kHz to 100 kHz as in the case where
the ballast is of the inverter type, on the other hand, the inductance value
of the variable inductance unit is made variable according to the
20 magnitude of the DC flowing through the LED unit, so as to act to
stabilize the current flowing through the LED unit.
[0044] Furthermore, in addition to the foregoing configuration, the
LED lamp may be one wherein the PWM control unit performs the
PWM control of the current flowing through the LED unit by driving a
25 pulse at a frequency higher than a predetermined frequency when a
frequency of an external AC inputted to the pair of input terminal parts
is lower than the predetermined fiequency, and does not perform the
PWM control of the current flowing through the LED unit when the
fiequency of the external AC inputted to the pair of input terminal parts
is higher than the predetermined fiequency.
[0045] This configuration makes it possible to light the LED lamp for
illumination, which is capable of being lit by driving a pulse at a
ftequency higher than the predetermined fiequency, by replacing the
previously mounted fluorescent lamp (or LED lamp), regardless of
whether the ballast of the fluorescent l a . lighting device is of the glow
starter, rapid start or inverter lighting type.
[0046] Therefore, this can easily eliminate the need for selecting and
deselecting (verifying compatibility of) LED lamps according to types
of lighting devices, or performing additional operations such as circuit
constnrction and direct connection on the lighting device side, that
cause users to investigate the current state for implementation and
construction, adjust the construction period, and so forth, yvhich are
troublesome and increase the implementation cost.
[0047] As a result, the obstacles to LED lamps being employed in
conventional fluorescent lamp lighting devices (or LED lighting
devices) in homes and offices are overcome.
[0048] This makes it possible for LED lamps, which can greatly
contribute to saving power and lengthening the life of lamps, to become
widespread inthe market.
[0049] When the ballast of a fluorescent lamp lighting device is of the
glow starter or rapid start type, for example, the fiequency of the AC
inputted from the pair of input terminal parts is a utility power
fkequency of 50 Hz or 60 Hz.
[0050] Therefore, the current flowing through the LED unit is P W
controlled by driving pulses at a fiequency higher than at least a
predetermined fiequency (e-g. 5 kHz), thus enabling the PWM control
unit to repeatedly switch the current flowing through the LED unit
odoff at high speed, and a nicker-fkee, stable effective value (RMS
value) to be obtained.
[00511 When the ballast of the fluorescent lamp lighting device is of the
inverter type, on the other hand., the AC inputted fiom the pair of input
terminal parts has a high fiequency of 20 kHz to 100 a, and thus the
PWM control unit does not perform PWM control, the frequency
rectified by the rectifier circuit unit is used' as is (a ripple voltage
waveform part superposed on the DC having a double fiequency in the
case of fill-wave rectification), and thus the current flowing through the
LED hit can obtain a flicker-fiee, stable effective value (RMS value)
by control (e.g. PWM control) of the external inverter type ballast.
[0052] This reliably prevents the same kind of control systems fiom
being superposed outside and inside of the LED lamp, and eliminates
causes giving rise to inconsistencies such as instability in the magnitude
of the cwrrent flowing through the LED unit.
[0053] Furthermore, in addition to the foregoing configuration, the
LED lamp may be one wherein a bypass circuit unit is provided
between a cathode-side terminal of the LED unit and a ground-side
output terminal of the rectifier circuit unit, wherein the bypass circuit
unit includes a switching device and a high-pass filter circuit outputting
a drive voltage for the switching device, and wherein the switching
device does not allow a current to flow from the cathode-side terminal
of the LED unit to the ground-side output terminal of the rectifier circuit
unit when the AC inputted to the pair of input terminal parts has a
frequency lower than the predetermined frequency, and allows a current
to £low fiom the cathode-side terminal of the LED unit to the
ground-side output terminal of the rectifier circuit unit when the AC
inputted to the pair of input terminal parts has a fiequency higher than
the predetermined frequency.
[0054] This configuration allows the AC inputted fiom the input
terminal of the rectifier circuit, when higher than the predetermined
fiequency, to bypass (circumvent) the switching device of the PWM
control unit for performing PWM control of the current flowing through
the LED unit, thereby preventing the PWM control unit incorporated in
the LED lamp fkom performing the PWM control.
[005q Furthermore, in addition to the foregoing configuration, the
LED lamp may be one wherein the switching device of the bypass
circuit unit is an N-channel MOSFET controlling a current flow
between drain and source terminals according to a gate voltage inputted
to a gate terminal, wherein the drain terminal is connected to the
cathode-side terminal of the LED unit, wherein the source terminal is
connected to the ground-side output terminal of the rectifier circuit unit,
wherein the gate terminal is connected to any one of the input terminals
of the rectifier circuit unit through the high-pass filter circuit, and
wherein the high-pass filter circuit outputs a gate voltage to the gate
terminal driven so as to allow a current to flow fiom the drain terminal
to the source terminal when the AC inputted to the pair of input tenninal
parts has a frequency higher than the predetermined fkequency, and
outputs a gate voltage to the gate terminal driven so as not to allow a
current to flow fiom the drain terminal to the source terminal when the
AC inputted to the pair of input tenninal parts has a fkequency lower
than the predetermined frequency.
[0056] According to this configuration, the N-channel MOSFET
functions as the switching device of the bypass circuit, thus enabling a
current to flow to the LED unit with sufficient margin, and the current
can be inhibited fiom flowing into the PWM control unit.
[0057] That is, since the PWM control unit is bypassed (circumvented)
when the AC inputted from the input terminals of the rectifier circuit
unit has a frequency higher than the predetermined frequency, the
current flowing through the LED unit can be prevented from flowing
into the PWM control unit, and prevents the PWM control unit from
performing PWM control.
[0058] Furthermore, in addition to the foregoing configuration, the
LED lamp may be one wherein the high-pass filter circuit includes a
&st capacitor, a first resistor connected in series to the fust capacitor so
as to have one terminal connected to one terminal of the first capacitor,
a first diode connected in a forward direction from the other tenmind of
the first resistor to the gate terminal, a second capacitor connected
between the source and gate terminals, a second resistor connected
between the source and gate terminals, a Zener diode connected in a
forward direction fiom the source terminal to the gate terminal, and a
second diode connected in a forward direction from the source terminal
to the other terminal of the fnst resistor, wherein the other terminal of
the first capacitor is connected to any one of the input terminals of the
rectifier circuit unit.
[0059] This configuration enables a filter function that allows only a
current having a fiequency higher than the predetermined fiequency to
pass to the next stage, and causes the switching device of the bypass
circuit reliably to switch onloff according to the frequency.
[0060] As a result, the current flows to the subsequent stage only when
the AC inputted fiom the input terminals of the rectifier circuit unit is
higher than the predetermined fiequency, thus enabling the N-channel
MOSFET serving as the switching device to be reliably switched on,
and enabling prevention of PWM control of the current flowing through
the LED unit.
[Q061] Furthermore, in addition to the configurations mentioned above,
the LED la& may be one wherein the predetermined frequency is a
frequency higher than 65 Hi but lower than 20 kHz.
[0062] This configuration makes it possible to clearly distinguish
between a fiequency (60 k 1 &) in the case where the ballast is of the
glow starter or rapid start type, and a fiequency (20 kHz to 100 kHz) in
the case of the inverter type distributed on the market, even when taking
account variations including precision of power supply frequency, thus
enabling switching between the case where the pulse-driven PWM
control is performed, and the case where it is not performed, according
to the results of distinguishing, and enabling lighting of the LED lamp
for illumination capable of being lit by driving a pulse at a high
frequency.
[0063] Since the predetermined fiequency to be distinguished is a
fiequency which is lower than 20 klh and falls within an audible region
(a fiequency band which can be sensed by humans as sound), a
fiequency in a higher fiequency band used for driving pulses for PWM
control is less likely to be felt as uncomfortable noise.
5 [0064] Furthermore, the illumination device of the present invention is
one including the LED lamp having any of the configurations
mentioned above.
[0065] This illumination device includes the foregoing LED lamp and
thus can stabilize the magnitude of the current flowing through the LED
10 unit so as to make it fall within a predetermined range by simply
replacing a previously mounted fluorescent lamp (or LED lamp) even
when the ballast .of the fluorescent lamp lighting device is a constant
power regulation inverter type ballast.
[0066J It is not necessary to newly provide a ballast for modulating the
15 LED unit on the illumination device side, and simply supplying an
external AC to a pair of input terminal parts can light it as illumination.
[0067] Furthermore, the illumination device itself is mounted with no
ballast and thus has a simplified configuration, thereby easily
eliminating the need for selecting and deselecting (verifying
20 compatibility of) LED lamps according to types of lighting devices, or
performing additional operations such as circuit construction and direct
connection on the lighting device side, that cause users to investigate the
current state for implementation and construction, adjust the
construction period, and so forth, which are troublesome and increase
25 the implementation cost.
[0068] The current control method of the LED lamp accordmg to the
present invention is a current control method of an LED lamp including
a pair of input terminal parts; a rectifier circuit wit rectifying an AC,
inputted fiom the outside to the pair of input terminal parts, to a DC;
and an LED unit emitting light by electrification of the DC outputted
5 fkom the rectifier circuit unit, the method including the steps of causing
the AC, in a circuit between the pair of' input terminal parts and the
rectifier circuit unit, to flow from one of the pair of input terminal parts
to the other input terminal part by way of the rectifier circuit unit
through a variable inductance unit; detecting, in a circuit between the
10 rectifier circuit unit and the LED uoit, a magnitude of the DC flowing
through the LED unit; and making an inductance value of the variable
inductance unit variable according to the detected magnitude of the DC;
wherein the magnitude of the DC flowing through the LED unit is
controlled so as to fall within a predetermined range.
15 [0069] This current control method of the LED lamp can make the
inductance value of the variable inductance unit variable according to
the magnitude of the DC detected by the current detection unit by
replacing a previously mounted fluorescent lamp (or LED lamp) even
when the ballast of the fluorescent lamp lighting device is a constant
20 power regulation inverter type ballast, whereby the output voltage is
fixed so as to be substantially proportional to the value. As a result,
the magnitude of the current flowing through the LED unit can be
stabilized so as to fall within a predetermined range.
Advantageous Effects of Invention
25 [0070] According to the LED lamp, the illumination device including
the LED lamp and the current control method of the LED lamp of the
present invention, it is possible to stabilize the magnitude of a current
flowing through an LED unit so as to make it fd.l within a
predetermined range by replacing a previously mounted fluorescent
lamp (or LED lamp) even when a ballast of a fluorescent lamp lighting
5 device is of a constant power regulation Inverter type.
Brief Description of Drawings
[0071] Fig. 1 is a block diagram illustrating the whole circuit of the -
illumination device according to an embodiment of the present
invention.
10 Fig. 2 is a circuit diagram of the LED lamp in an embodiment of
the present invention.
Fig. 3 is a block diagram illustrating the inside of an integrated
circuit IC 1.
Figs. 4(a) and 4(b) are circuit diagrams illustrating variable
15 inductance wnits.
Fig. 5 is a chart illustrating variable control patterns of the
variable inductance units.
Fig. 6 is a diagram illustrating variable regions and circuit
interrupt regions of an inductance value with respect to a detected
20 current.
Fig. 7 is a flowchart illustrating a current control method of an
LED lamp in an embodiment of the present invention.
Figs. 8(a) and 8(b), respectively, are waveforms of an input
voltage and a current flowing through an LED unit at an inductance
25 value of 100 pH when the LED lamp is lit by a constant power
regulation inverter type ballast, while Figs. 8(c) and 8(d), respectively,
are waveforms of the input voltage and the current flowing through the
LED unit at an inductance value of 400 pH when the LED lamp is lit by
the constant power regulation inverter type ballast.
Figs. 9(a) and 9(b), respectively, are waveforms of an input
5 voltage and a current flowing through an LED unit at an inductance
value of 100 pH when the LED lamp is lit by a constant power
regulation inverter type ballast, while Figs. 9(c) and 9(d), respectively,
are waveforms of an input voltage and a current flowing through an
LED unit at aninductance value of 400 pH when the LED lamp is lit by
10 the constant power regulation inverter type ballast.
Figs.' 10(a), lo@), 10(c), 10(d) and 10(e), respectively, are
waveforms of an input voltage Vm, a voltage Vgl at a gate terminal of a
switching device Q1, a current sensor terminal voltage Vcs of an
integrated circuit IC1, a voltage Vg2 at a gate terminal of a switching
15 device 42, and a current i flowing through an LED u'nit 24.
Figs. 11 (a), 1 I@), 11 (c), ' 1 l(d) and 1 1 (e), respectively, are
waveforms of the input voltage Vin, the voltag6 Vgl at the gate terminal
of the switching device Q1, the current sensor terminal voltage Vcs of
the integrated circuit IC1, the voltage Vg2 at the gate terminal of the
20 switching device 42, and the current i flowing through the LED unit 24.
Figs. 12(a), 12(b), 12(c), 12(d) and 12(e), respectively, are
waveforms of the input voltage Vin, the voltage Vgl at the gate terminal
of the switching device Q1, the current sensor terminal voltage Vcs of
the integrated circuit IC1, the voltage Vg2 at the gate terminal of the
25 switching device 42, and the current i flowing through the LED unit 24.
Fig. 13 is a block diagram illustrating the whole circuit of the
illumination device in a modified example of the present invention.
Fig. 14(a) is a diagram illustrating a part of a circuit which
makes a threshold voltage variable according to the magnitude of a high
voltage 0w,hile F ig. 14(b) is an overall block diagram in which an
LED lamp in an embodiment is connected in series to a series rapid type
ballast.
Figs. 15(a), IS@) and 15(c) are diagrams illustrating examples
of ballasts of glow starter, rapid start and inverter types, respectively.
Fig. 16 is a diagram illustrating an example of a series rapid type
ballast.
Description of ~mbodiments
[0072] Embodiments of the present invention will be explained in detail
below with reference to the drawings.
Embodiments . +
[0073] Fig. 1 is a block diagram illus'trating the whole circuit of the
illumination device according to an embodiment of the present
invention; Fig. 2 is a circuit diagram of the LED lamp in the
embodiment of the present invention; Fig. 3 is a block diagram
illustrating the inside of an integrated circuit IC 1; Figs. 4(a) and 4@) are
circuit diagrams illustrating variable inductance units; Fig. 5 is a chart
illustrating variable control patterns of the variable inductance units;
Fig. 6 is a diagram illustrating variable ,regions and circuit interrupt
regions of an inductance value with respect to a detected current; Fig. 7
is a flowchart illustrating a current control method of an LED lamp in
an embodiment of the present invention; Figs. 8(a) to 8(d) and 9(a) to
9(d) are waveforms of input voltages of the LED lamp and currents
flowing through an LED unit when the LED lamp is lit by a constant
power regulation inverter type ballast in the embodiments of the present
invention; Figs. lO(a) to lO(e) are voltage waveform charts at respective
measurement points in a case where a glow starter type is adopted for a
ballast of the illumination device in the embodiment of the present
invention; Figs. I l(a) to 11 (e) are voltage waveform charts at respective
measurement points in a case where a rapid start type is adopted for the
ballast of the illumination device in. the embodiment of the present
invention; Figs. 12(a) to 12(e) are voltage waveform charts at respective
measurement points in a case where an inverter type is adopted for the
ballast of the illumination device in the embodiment of the present
invention; Fig. 13 is a block diagram illustsating the whole circuit of the
illumination device in a modified example of the present invention; and
Fig. 14(a) is a diagram illustrating a part of a circuit which makes a
threshold voltage variable according to the magnitude of a high voltage
(HV), while Fig. 14(b) is an overall block diagram in which LED lamps
in an embodiment are connected in series to a series rapid type ballast.
[0074] First, as illustrated in Fig. 1, an illumination device 10 according
to an embodiment of the present invention includes a plug 11 that is
connected in order to supply power from an external power supply of a
household AC of 100 to 240 V (50 Hz or 60 Hz), for example, a ballast
12 controlling the power inputted from the plug 11 in order to light a
fluorescent lamp, and an LED lamp 20 to which a predetermined
voltage is inputted between a pair of input terminal parts (between input
terminal parts 20a, 20c) according to the type of the ballast 12.
[0075] Here, the ballast 12 may be any known glow starter, rapid start
or inverter type for lighting existing fluorescent lamps.
[0076] Since the LED lamp 20 operates normally as long as the external
power supply has an AC of 100 to 240 V (50 Hz or 60 Hz), the external
power may .be directly inputted to the LED lamp 20, bypassing the
5 ballast 12.
[0077] Here, a h e outputting an AC fiom the ballast 12 is connected so
as to enable inputting between either one or both of the pair of input
terminal parts (between input terminal parts 20% 20c) and/or a pair of
trput terminal parts (between input terminal parts 20b, 20d).
10 [0078] On the other hand, an input circuit unit Z9 constituted by an RC
parallel circuit composed of a resistor R9 and a capacitor C9 is
connected between the input terminal part 20a of the LED lamp 20 and
a terminal T1 (see Fig. 2).
[Q079] Similarly, an input circuit unit Z10 constituted by an RC parallel
15 circuit composed of a resistor R10 and a capacitor C10 is connected
between the input terminal part 20b of the LED lamp 20 and the
terminal T1 (see Fig. 2).
[OOSO] Similarly, an input circuit unit Z11 constituted by an RC parallel
circuit composed of a resistor R11 and a capacitor C11 is connected
20 between the input terminal part 20c of the LED lamp 20 and a terminal
T2 (see Fig. 2).
[0081] Similarly, an input circuit unit Z12 constituted by an RC parallel
circuit composed of a resistor R12 and a capacitor C12 is connected
between the input terminal part 20d of the LED lamp 20 and the
25 terminal T2 (see Fig. 2).
[0082] Therefore, a resistance value of about several 0 to about 100 f2
is selected for each of the resistors R9, R10 between the input terminal
parts 20a, 20b so as to correspond to the resistance component of a
flament of the fluorescent lamp.
[0(683] Similarly, a resistance value of about several i2 to about 100 51
5 is selected for each of the resistors Rl 1, R12 between the input tenninal
parts 20c, 20d so as to correspond to the resistance component of the
filament of the fluorescent lamp.
[0084] When the resistance values of the resistors R9 to 1112 are
selected 'as mentioned above, these resistors R9 to R12 can ad as
10 dummy resistors even if the ballast 12 is of the inverter type adapted to
automatically detect whether or not a fluorescent lamp is mounted on
the load side (whether there is conduction through the ' filament
resistance) and outputs no power when the fluorescent lamp is not
mounted (case where no fluorescent lamp is mounted), and thus power
15 'is normally supplied to the LED lamp 20.
[OO85] A circuit interrupt unit 33 is connected between the terminals
TI, T11, while a circuit intempt unit 33 is similarly connected between
the terminals T2, T12. Each circuit interrupt unit 33 includes a relay of
a Form B contact type, for example, and is adapted to interrupt an AC
20 fkorn a pair of input terminal parts when the magnitude of a current i
flowing through the LED unit 24 is abnormal. The circuit interrupt
unit 33 will be explained later in detail.
[0086] Furthermore, a protection circuit unit 21 (see Fig. 2) is inserted
between the terminals T11, T12.
25 [0087] In the protection circuit unit 21, a two-electrode discharge tube
SAl, within which an inert gas such as neon or argon is enclosed, and a
varistor 'SA2 are connected in series.
[0088] Appropriately setting the discharge starting voltage of the
two-electrode discharge tube SA1 and the clamping voltage of the
varistor SA2 can suppress the surge voltage entering between the
terminals T1 and T2 fiom the power supply side to a peak value of
about 400 V or lower. Furthermore, combining the two-electrode
discharge tube SA1 and the varistor SA2 in series allows the varistor
SA2 to effectively prevent a follow current fiom being caused by the
two-electrode discharge tube SA1 continuously discharging after the
surge voltage ends.
[0089] This absorbs a surge current, even when a lightning surge or
lightning-induced surge, for example, enters from the external input
power supply side, and inhibits the surge current from advancing into a
rectifier circuit unit 22 side.
[0090] Hence, electronic components such as diodes and capacitors .
constituting the rectifier circuit unit 22 and LED unit 24 can be
protected.
[0091] A threshold element 34 is connected in series on the terminal
TI2 side. The threshold element 34 includes two zener diodes D34a,
D34b connected in series in directions opposite to each other
(bi-directionally) and a relay RY34 connected in parallel to the zener
diodes (see Fig. 2), for example. The relay RY34 is driven by an
output voltage fiom a delay circuit (not depicted) which outputs a
predetermined voltage after a lapse of a predetermined time fiom when
a current flows through the LED unit 24, so as to short-circuit both ends
of the two zener diodes D34a, D34b. The delay circuit is set such as to
output a predetermined voltage after the lapse of the predetermined time
from when an AC surpasses a predetermined threshold of the threshold
element 34 and begins to flow through the rectifier circuit unit 22,
thereby driving the relay RY34. As a consequence, after the lapse of
the predetermined time fkom when the AC exceeding the predetermined
threshold is inputted to a pair of input terminal parts fiom the outside,
both ends of the threshold element are short-circuited by the relay
RY34. The threshold element is defined as an element which starts
electrification therewithin when a voltage at a predetermined threshold
or higher is applied between both terminals thereof. As the threshold
element 34, a SlDAC (registered trademark), which is a gateless
two-terminal thyristor, a two-electrode discharge tube and the like are
employable in place of the Zener diodes D34a, 1)34b, for example.
The threshold element 34 will be explained later in detail.
15 [0092] A variable inductance unit L50 is inserted between the terminal
TI1 and a terminal T3 on one input side of the rectifier circuit unit 22,
and a variable inductance unit L60 is similarly inserted in series with the
threshold element 34 between the terminal ~ 1an2d a terminal T6 on the
other input side of the rectifier circuit unit 22. Inductance values
20 (hereinafter also referred to as L values) of the variable inductance units
L50, L60 are controlled by an inductance variable control unit 32.
Making inductances variable in the variable inductance units L50, L60
will be explained later in detail.
[0093] As a consequence, the variable inductance units L50, L60 act as
25 impedances for restricting flowing currents with respect to
high- frequency pulses.
[OW41 Therefore, when the ballast 12 is of the glow starter or rapid
start type, for example, a switching device Q1 switches odoff, and thus
prevents switching noises (high-frequency noise pulses) thereof fiom
flowing out to the external AC (input power supply) side through any of
5 the input terminal parts 20a to 20d.
[0095] Furthermore, when the ballast 12 is of the inverter type, on the
other hand, an AC at a high frequency of 20 kHz to 100 kHz is inputted,
and thus the variable inductance units L50, L60 act as (reactive power
loss) loads without effective power loss.
10 [0096] This allows power to be stably outputted fkom the inverter type
ballast 12 by ensuring that the load impedance of the LED lamp 20 falls
within a predetermined range, in terms of between either one or both of
the pair of input terminal parts (between the input terminal parts 2Oa,
20c) and the pair of input terminal parts (between the input terminal
15 parts 20b, 20d).
[0897] Furthermore, the rectifier circuit unit 22 is constituted by a
bridge diode composed of four diodes D4 to D7, and electrolytic
capacitors C4, C5 connected in parallel so as to smooth a Ill-wave
rectified waveform in the output stage of the bridge diode (see Fig. 2).
20 [0098] Tn output-side terminals of the rectifier circuit unit 22, a DC
voltage is outputted between a high-voltage o - s i d e output terminal
T7 and a ground-side output terminal T5.
[0099] A high-voltage (HV)-side output terminal T7 is connected to an
anode-side terminal TA of the LED unit 24 through a smoothing circuit
25 unit 23, and a cathode-side terminal TK of the LED unit 24 is connected
to a PWM control unit 25 through the smoothing circuit unit 23.
[OIOO] Here, the LED unit 24 is constituted by a circuit in which three
LED circuit groups, each including 30 LEDs (light-emitting diodes)
having a forward voltage of about 3 V each and connected in series, are
connected in parallel, and the current i flows in a direction (direction of
5 the arrow) fiom the anode-side terminal TA to the cathode-side terminal
TK.
[01011[ Additionally, a GND terminal TG of the PWM control unit 25 is
connected to the ground-side output terminal T5 on the output side of
the rectifier circuit unit 22.
10 [01102] According to the circuit configuration mentioned above, the
current i flowing through the LED unit 24 is P.WM controlled by the
PWM control unit 25 driving pulses at a fkequency higher than a
predetermined fiequency, and falls within a predetermined current value
range.
15 [0103]1 On the other hand, a bypass circuit unit 26 is connected between
the cathode-side terminal TK of the LED unit 24 and the ground-side
output tenninal T5 of the rectifier circuit unit 22.
[0104] As a result, in the case where the fiequency of the AC inputted
to one terminal T3 of the rectifier circuit unit 22 is higher than the
20 predetermined frequency, resistors R3, R4 and R5 are connected in
parallel between the termiqals T9 and TG even when the switching
device Q1 is in the on state (the state where a current flows fiom the
drain terminal to the source terminal; the same hereinafter), and thus the
current i, which bypasses (circumvents) the PWM control unit 25 and
25 flows through the LED unit 24, flows directly fiom the cathode-side
terminal TK to the ground-side output terminal T5 of the rectifier circuit
unit 22 though the GND terminal TG of the PWM control unit 25.
[0105] Hence, the current i hardly flows through the PWM control unit
25, and thus is not PWM controlled.
[OlOq In the foregoing and following explanations, performing PWM
5 (which is short for Pulse Width Modulation; the same hereinafter)
control of the current i according to a duty ratio is defined as a period of
a driving pulse that is fixed and controls the current i so as to switch
ordoff according to the duty ratio (the ratio of pulse width to pulse
period, which has the same meaning as "on duty"; the same hereinafter)
10 depending on the magnitude of an input signal (the magnitude of the
voltage detected by a pin #2 which is a current sensor terminal in the
present embodiment); the duty ratio at that moment is greater than 0%
but smaller than 100%.
[0107l This can stabilize the magnitude of the current i flowing bough
15 the LED unit 24.
[OlOB] On the other hand, not performing PWM control of the current i
according to a duty ratio is defined as the PWM control unit not
controlling the current i so as to switch on/off according to the duty
ratio; in addition to the case where the current i hardly flows through the
20 PWM control unit as mentioned above, this encompasses both a case
where the driving pulses have a duty ratio of 0% so that the switching
device Q1 is always in the off state during operation, and a case where
the driving pulses have a duty ratio of 100% so that the switching
device Q1 is always in the on state during operation.
25 [0109] A current detection unit 3 1 is connected in series with the bypass
circuit unit 26 between the cathode-side terminal TK of the LED unit 24
and the ground-side output terminal T5 of the rectifier circuit unit 22.
When the bypass circuit unit 26 bypasses the current i flowing through
the LED unit 24 (when the ballast is of the inverter type), the current
detection unit 31 detects the magnitude of this DC and outputs thus
detected signal @C voltage) to the inductance variable control unit 32.
[QIlO] Then, the inductance variable control unit 32 controls the
inductance values of the variable inductance units L50, L60 according
to the magnitude of the current detected by the current detection unit 3 1.
~he.induct.ancev ariable control unit 32 will be explained later in detail.
[0111] Individual constituent parts will now be explained in further
detail with reference to Figs. 2 to 6.
p112] While the resistor R9 between the input terminal part 20a and
terminl T1 acts as a dummy resistor corresponding to the filament of
the fluotescent lamp as mentioned above, the capacitor C9 allows an AC
to pass therethrough in a normal operation state (when the LED unit 24
is lit).
[0113] This can shunt the AC in inverse proportion to the ratio between
the capacitive reactance, determined by the frequency of the AC and the
capacity of the capacitor C9, and the resistance value of the resistor R9,
and thus proportionally suppresses the heat of the resistor R9.
[Q114] Similarly, while the resistor R11 between the input terminal part
20c and the terminal T2 acts as a dummy resistor corresponding to the
filament, the capacitor C11 allows the AC to pass therethrough in the
normal operation state, and thus suppress the heat of the resistor R11.
[0115] Furthermore, a fuse F1 is used for overcurrent protection against
the power supply current inputted between either one or both of the pair
of input terminal parts (between input terminal parts 20a, 20c) and the
pair of input terminal parts (between input terminal park 20b, 20d).
[Olld] Next, the rectifier circuit unit 22 has, in an upstream stage, the
bridge diode constituted by the diode D4 whose anode and cathode are
5 connected to the terminal T3 and the high-voltage (HV)-side output
terminal T7, respectively, the diode D5 whose anode and cathode are
connected to the terminal T6 and the high-voltage (HV)-side output
terminal T7, respectively, the diode D6 whose anode and cathode are
connected to the terminal T6 and a terminal T4 at the same potential as
10 with the terminal T3, respectively, and the diode D7 whose anode and
cathode are connected to the ground-side output terminal T5 and the
terminal T6, respectively.
[0117] Furthermore, in a stage downstream of the bridge diode, the
full-wave rectified waveform is smoothed, and thus the electrolytic
15 capacitors C4, C5 are connected in parallel between the high-voltage
(HV)-side output terminal T7 and the ground-side output terminal T5 so
as to have plus (+) terminals on the high-voltage (HV)-side output
terminal T7 side, and minus (-) terminals on the ground-side output
terminal T5 side.
20 [0118] According to this, the smoothed DC-converted output voltage is
outputted to the high-voltage (HV)-side output terminal T7, and the
lower voltage part is outputted to the ground-side output terminal T5.
[0119] The pulsating component (ripple component) of the high DC
voltage outputted to the high-voltage (HV)-side output terminal T7 is
25 removed by the smoothing circuit unit 23, and this is called a choke coil
input type smoothing circuit and is constituted by a series circuit of
choke coils L1 to L4 and a parallel circuit of an electrolytic capacitor
C3 with respect to the LED unit 24.
[0120] Additionally, the current i, from which the pulsating component
has been removed by having passed through the smoothing circuit unit
5 23, flows fiom the anode-side terminal TA of the LED unit 24 to the
cathode-side terminal TK, and functions to light a total of 90 LEDs
(light-emitting diodes) constituting the LED unit 24 mentioned above.
[0121] The current i having passed through the smoothing circuit unit
23 from the LED unit 24 is PWM controlled by driving pulses at a
10 predetermined oscillation period tosc (ps) by the resistors R1 to R8,
capacitors C1, C2, a Zener diode Dl, a diode D2 and the switching
device Q1, which constitute the PWM control unit 25 and are connected
to the integrated circuit IC1 and pins (#1 to #8).
[On21 When a commercially available model HV9910B (see Fig. 3)
15 manufactured by Supertex, Ind. is used as the integrated circuit ICl, the
oscillation period tosc (ps) is controlled by the time obtained according
to the following Formula 1 depending on the resistance value RT Qd2)
of the resistor R1 connected to the pin #8.
[Formula 1 ]
[On31 When the resistor Rl is set to about 499 (kR), for example, in
the present embodiment, about 20.84 (ps) is determined as the
oscillation period tosc (ps) according to the above-mentioned Formula
1.
[0124] Therefore, if the oscillation period is about ,20.84 (ps) as
calculated, can be driven at a high frequency of about 48 kHz.
[012§J Fu-therrnore, the switching device Ql controlling the onloff of
the current i flowing through the LED unit 24 is an N-channel MOSFET
5 which can control a current flow between drain and source terminals
according to the input voltage at a gate terminal.
[0126] In the integrated circuit ICl, the drain terminal of the switching
device Q1 is connected to the anode terminal. of a diode D3 constituting
a part of the smoothing circuit unit 23, the soiuce terminal is connected
10 to the terminal T9 connected to the pin #2, which is a current sensor
terminal of the integrated circuit IC1, through the resistor R6, and a
voltage of a proportion corresponding to that of the resistor R7, where
the voltage outputted fiom the pin ##4 of the integrated circuit IC1 has
been divided by the resistors R2, R7, is inputted to the gate terminal.
15 [0127j ~urthemore, the pin #1 of the integrated circuit IC1 is
connected to the high-voltage 0 - s i d e output terminal T7 through the
resistor R8 and zener diode Dl, and thus is supplied with the high DC
voltage outputted fiom the rectifier c u t unit 22.
[0128] As a consequence, the voltage (about 8 V DC to about 450 V
20 DC) supplied fiomthe pin #1 is lowered, rectified and stabilized by an
internal regulator to a predetermined VDD voltage (about 12 V DC),
functions as a power supply for driving the inner circuit of the
integrated circuit ICl, and the VDD voltage is outputted to the pin #6
(see Fig. 3).
25 [0129] According to such connections as described above, when the
voltage detected at the pin #2, which is the current sensor terminal, does
not exceed a threshold voltage of about 250 mV DC by driving pulses
of the integrated circuit IC1, a high-level voltage (about 7.5 V DC) is
outputted to the gate terminal of the switching device Q1, switching it
on, whereas when the voltage detected at the pin #2, which is the
current sensor terminal, reaches the threshold voltage of about 250 mV
DC, a low-level voltage (about 0 V) is outputted to the gate terminal of
the switching device Q1, switching it off (a state where no current flows
from the drain terminal to the source terminal; the same hereinafter).
[0130] In this way, the integrated circuit IC1 acts such that driving
pulses outputting the voltage Vgl at the gate terminal of the switching
device Q1 have a fixed period, the duty ratio of the pulse width of the
voltage Vgl at the gate terminal is made variable according to the level
of the, voltage (current sensor terminal voltage Vcs) detected at the pin
#2, and the current i flowing through the LED unit is controlled.
[0131] That is, the current i is PWM controlled by the high-frequency
driven pulses of the PWM control unit 25, and thus repeatedly increases
and decreases in pulses (in triangle waves) at the oscillation period tosc
(ps) obtained by the above-mentioned Formula 1 according to the
switching device Q1 that is repeatedly switched onloff.
[0132] In the present embodiment, the pin #7 is connected to (has the
same potential as) the pin #6, and thus the pin #7 is inputted with the
voltage VDD (about 12 V DC) exceeding the above-mentioned
threshold voltage (about 250 mV DC).
[0133] Furthermore, in the present embodiment, the threshold voltage
to be compared with the voltage detected at the pin #2, which is the
current sensor terminal, is set to about 250 mV DC generated within the
integrated circuit IC 1 (see Fig. 3).
[0134] On the other hand, when the voltage inputted to the pin #7 in the
integrated circuit IC1 is set to a voltage within a range not exceeding
about 250 mV DC, this can be set as a threshold voltage to be compared
with the voltage detected by the current sensor terminal (pin #2), and .
thus the duty ratio can further be made variable in a downward
direction.
[0135] This can lower the effective value (RMS value) of the current i
flowing through the LED unit 24, thereby modulating (dimming) light.
[013q Here, when the switching device Q1 is switched off, the sees
circuit of choke coils L1 to L4 generates a counter-electromotive force
in such a direction as to allow the current i to flow, while the diode D3
for absorbing the current caused by the counter-electromotive force is
connected in a forward direction fiom a terminal T8 at a terminal end of
the choke coil L1 to the anode-side terminal TA of the LED unit 24.
[013q On the other hand, as mentioned above, the bypass circuit unit
26 and current detection unit 3 1 are disposed between the cathode-side
terminal TK of the LED unit 24 and the ground-side output tenninal T5
of the rectifier circuit unit 22.
[0138] The bypass circuit unit 26 includes a switching device Q2 and a
high-pass filter circuit outputting a drive voltage (gate terminal voltage)
to the switching device 42.
[0139] Here, the switching device 42 of the bypass circuit unit 26 is an
N-channel MOSFET which controls a current flow between drain and
source terminals according to a voltage inputted to a gate terminal, the
drain terminal is connected to the cathode-side tenninal TK of the LED
unit 24, the source terminal is (electrically) connected to the
ground-side output terminal T5 of the rectifier circuit unit ,22 through
the current detection unit 3 1, and the gate terminal is connected to the
tenninal T4 of the rectifier circuit unit 22 through the high-pass filter
circuit.
[014Q] The high-pass filter circuit includes a first capacitor C6, a first
resistor R13 connected in series to the fist capacitor C6 so as to have
one terminal connected to one terminal of the first capacitor, a first
diode D9 connected in'a forward direction from the other terminal of the
first resistor R13 to the gate terminal of the switching device 42, a
second capacitor C7 electrically connected between the source i d gate
terminals of the switching device Q2, a second resistor R14 electrically
connected between the source and gate terminals, a zener diode Dl0
electrically connected in a forward direction fiom the source terminal to
the gate terminal, and a second diode D8 electrically connected in a
forward direction fiom the source tenninal to the other terminal of the
first resistor R13.
[014X] The other terminal of the first capacitor C6 is connected to any
one of the input terminals (the terminal T3 or T6 through the terminal
T4) of the rectifier circuit unit 22.
[OX421 When circuit constants of the first capacitor C6, first resistor
R13 and second resistor R14 are selected so as to cut off the AC
inputted to the terminal T3 at a predetermined frequency or below, a CR
circuit composed of the capacitor and resistors acts as a high-pass filter
and thus only allows the AC having a frequency exceeding the
predetermined fiequency to pass therethrough to a stage downstream
thereof.
[0143] That is, the AC having a fiequency higher than the
predetermined frequency inputted to the terminal T3 generates a DC
voltage on the high voltage side of the second capacitor C7, second
5 resistor R14 and Zener diode D10, and a voltage capable of switching on
the switching device 42 is outputted to the gate terminal.
[0144] The voltage at the gate terminal can appropriately be set
according to the potential division ratio between the first and second
resistors R13, R14, and the zener voltage of the zener diode Dl0
10 limiting the voltage inputted to the gate terminal, but may be set so as to
fall within a high-level gate terminal voltage range which can switch on
the switching device 42.
[0145] The high-pass filter circuit is an input circuit for a filter allowing
an AC having a fiequency higher than a predetermined fiequency to
15 pass therethrough, so as to set the gate terniinal of the switching device
, 42 to a high level (e:g. about 14 V DC), and thus may be connected to
the terminal T6 to which the same AC (except for a 1800-difference in
phase) is inputted as with the ground-side terminal T5 of the rectifier
circuit unit 22.
20 101461 According to the foregoing configuration, the high-pass filter
outputs a predetermined gate voltage allowing a current to flow fiom
the drain terminal to the source terminal when the AC inputted to the
input terminal of the rectifier circuit unit 22 has a fiequency higher than
a predetermined fiequency (in the present embodiment, a cutoff
25 frequency in actual measurement being set to about 5 kHi by choosing a
capacity of 100 pF for the first capacitor C6, a resistance value of 51 kC2
for the first resistor R13, and a resistance value of 5 1 kQ for the second
resistor R14; the same hereinafter), and outputs a gate voltage that does
not allow a current to flow f?om the drain terminal to the source
tenninal when the AC has a frequency lower than a predetermined
5 frequency.
[0147] That is, the switching device 42 prevents flowing of a current
from the cathode-side terminal TK of the LED unit 24 to the
ground-side output terminal T5 of the rectifier circuit unit 22 through
the GND terminal TG of the PWM control unit 25 when the AC has a
10 frequency lower than the predetermined frequency (about 5 IrHz), and
makes it possible for a current to flow fiom the cathode-side terminal
TK of the LED unit 24 to the ground-side output terminal T5 of the
rectifier circuit unit 22 through the GND tenninal TG of the PWM
control unit 25 when the AC has a frequency higher than the
15 predetermined frequency (hereinafter referred to as cutoff frequency;
about 5 M-Iz).
[0148] As a result, when the external AC inputted to a pair of input
terminal parts has a fi-equency lower than the predetermined frequency
(e.g. when inputted fiom a ballast of the glow starter type or rapid start
20 type), the current i flowing through the LED unit 24 is PWM controlled
by the PWM control unit 25 driving pulses at a frequency higher than
the predetermined fiequency, producing pulse waves (triangle waves).
[0149] On the other hand, when the external AC inputted to a pair of
input terminal parts has a fiequency higher than the predetermined
25 frequency (e.g. when inputted fiom a ballast of the inverter type), the
PWM control unit 25 is bypassed (circumvented) through the bypass
circuit unit 26, and thus the current i flowing through the LED unit 24
flows as is to the ground-side output terminal T5 of the rectifier circuit
~t 22 without PWM control being performed by the PWM control unit
25.
5 [0150] Therefore, the AC having a high frequency inputted to a pair of
input terminal parts only passes through the rectifier circuit 22,
smoothing circuit unit 23 and LED unit 24, and thus the current i
flowing through the LED unit 24 attains a waveform in which the AC
inputted to the pair of input terminal parts is converted to a DC by
10 I11-wave rectification (e.g. see Fig. 12(e)).
[0151] The current detection unit 3 1 is constructed by an RC parallel
circuit composed of a resistor R3 1 and a capacitor C3 1. The current
detection unit 3 1 detects the magnitude of the current flowing from the
drain terminal to source terminal of the switching device 42 in the
15 bypass circuit unit 26 when the switching device 42 is in the on state. *
That is, the current detection unit 31 detects the current i flowing
through the LED unit 24 when the fiequency of the external AC
inputted to its pair of input terminal parts is higher than a predetermined
frequency, e.g. when the ballast is of the inverter type. In this
20 embodiment, the current detection unit 3 1 outputs a detected signal @C
voltage) corresponding to the current value flowing therethrough to the
inductance variable control unit 3 2.
[0152] The inductance variable control unit 32, which includes a
microprocessor, controls the induchce values of the variable
25 inductance units L50, L60 according to the magnitude of the current
detected by the current detection unit 31 (i.e. the magnitude of the DC
.voltage from the current detection unit 3 1).
[0653] For example, as illustrated in Fig. 4(a), the variable inductance
unit L50 has inductors L51, L52 connected in series and switch
elements 32% 32b connected in p d e l with the respective inductors
L51, L52. On the other hand, as illustrated in Fig. 4(b), the variable
inductance unit L60 has inductors L5 1, L52 connected in series and a
switch element 32c connected in parallel with the series circuit of the
inductors L5 1, L52. For example, . sliding d c t o r s and, magnetic
amplifiers may be employed for the variable inductance units L50, L6O.
[0154] By controlling the on/off of the switch elements 32a, 32b, 32c,
the inductance variable control unit 32 can make the total inductance
value of the variable inductance units L50, L60 variable. When the
magnitude of the current i flowing through the LED unit 24 is within a
predetermined range (L-value invariable region) as illustrated in Figs. 5
and 6, for example, the inductance variable control unit 32 sviritches the
switch element 32a on and the switch elements 32b, 32c off as in pattern
2, so as to set the inductance value of the variable inductance units L50,
L60 to the total inductance value of the inductors L52, L61, L62.
[01551[ When the magnitude of the current i flowing through the LED
unit 24 is lower than the predetermined range (within an L-value
variable (drop) region), on the other hand, all the switch elements 32a to
32c switch on as in pattern 3, so as to lower the total inductance value of
the variable inductance units L50, L60. This causes the output voltage
to decrease and output current to increase in the constant power
regulation inverter type ballast. That is, the current i flowing through
the LED unit 24 can be enhanced, so that the magnitude of the current i
can be stabilized so as to f d within the predetermined range.
[0156j When the magnitude of the current i flowing through the LED
unit 24 is higher than the predetermined range (within an L-value
variable (rise) region), all the switch elements 32a to 32c switch off as
in pattern 1, so as to enhance the total inductance value of the variable
inductance units L50, L60. This causes the output voltage to increase
and output current to decrease in the constant power regulation inverter
type ballast. That is, the curre11t i flowing through the LED qnit 24. can
be lowered, so that the magnitude of the current i can be stabilized so as
to fall within the predetermined range.
[0157] On the other hand, when the magnitude of the current detected
by the current detection unit 31 exceeds a predetermined upper limit
(falls within a circuit interrupt region), the inductance variable control
unit 32 controls the circuit interrupt units 33, so as to intermpt the AC
flowing from the pair of input terminal parts to the rectifier circuit unit
22 (protection against overcurrent). When the magnitude of the
current detected by the current detection unit 3 1 is below a
predetermined lower limit (falls within a circuit interrupt region), the
inductance variable control unit 32 controls the circuit interrupt units
33, so as to intempt the AC flowing fiom the pair of input terminal
parts to the rectifier circuit unit 22 (protection against some
abnormalities in the current).
[0158] h this embodiment, the current detection unit 31 detects the
current after both ends of the threshold element 34 are short-circuited.
For example, there are some kinds of constant power control inverter
type ballasts which, in order to grasp states of fluorescent lamps (e.g. to
check whether or not the fluorescent lamps are attached to the load side)
at the time of starting outputs, set the output voltage lower than the rated
value beforehand, cause a low slight current to flow that is unable to
obtain an appropriate quantity of light, and monitor the magnitude of the
5 output current at that time, subsequently raise the output voltage to a
predetermined range, and then perfom constant power regulation. In
the present embodiment, however, both ends of the threshold element
. 34 are short-circuited after a lapse of a predetermined time . fro.m when
inputting the AC exceeding a predetermined threshold to the pair of
'10 input terminal parts fkom the outside, and the inductance value of the
variable inductance unit is made variable according to the magnitude of
the DC flowing through the LED unit aRer both ends of the threshold
element 34 are short-circuited, so that, even in such kinds of inverter
type ballasts, only the current flowing through the LED unit to be
15 detected (the current in a normal lighting state) is detected without
performing erroneous control.
[0159] A current control method of an LED lamp in the case where the
ballast is of a constant power regulation inverter type will now be
explained with reference to Fig. 7.
20 [0160] First, the inductance variable control unit 32 sets the inductance
values of the variable inductance units L50, L60 to pattern 2 as an initial
setting (step Sol).
[0161] Subsequently, after a lapse of a predetermined time fiom when
inputting an AC exceeding a predetermined threshold from the ballast of
25 the constant power regulation inverter type to the pair of input terminal
parts, both ends of the threshold element 34 are short-circuited, whereby
the AC enabling normal lighting flows through the variable inductance
units L50, L60 and rectifier circuit 22. Since the ballast is of the
inverter type, while the frequency of the AC is higher than a
predetermined frequency, the switching device Q2 in the bypass circuit
5 unit 26 switches on, so that the LED unit 24 is supplied with the current
rectified by the rectifier circuit unit 22 after flowing thereto through the
variable inductance units L50, L60 (step ,302). Here, the current i
flowing through the LED unit 24 is neither PWM controlled by the
P W control unit 25 nor smoothed by the smoothing circuitunit 23
10 (both units are bypassed).
[0162] Next, the current detection unit 3 1 detects the magnitude of the
current i flowing through the LED unit 24 (step S03). When the
magnitude of the current detected by the current detection unit 31 is
within a predetermined range (the L-value invariable region illustrated
15 in Fig. 6), the inductance variable control unit 32 keeps the inductance
values of the variable inductance units L50, L60 unchanged in pattern 2
(step S04).
[0163] When the magnitude of the current detected by the current
. . detection unit 31 is lower than the predetermined range (within the
20 L-value variable (drop) region illustrated in Fig. 6), however, the
inductance variable control unit 32 sets the inductance values of the
variable inductance units L50, L60 to pattern 3, so as to lower the total
inductance value. This causes the output voltage to decrease and the
output current to increase in the ballast of the constant power regulation
25 inverter type. That is, the current i flowing through the LED unit 24
can be enhanced, whereby the magnitude of the current i flowing
through the LED unit 24 can be stabilized so as to fall within the
predetermined range (step S04).
[0164] When the magnitude of the current detected by the current
detection unit 31 is higher than the predetermined range (within the
5 L-value variable (rise) region illustrated in Fig. 6), on the other hand,
the inductance variable control unit 32 sets the inductance values of the
variable inductance units L50, L60 to pattern 1, so as to enhance the
total inductance value. This causes the output voltage to increase and
the output current to decrease in the ballast of the constant power
10 regulation inverter type. That is, the current i flowing through the
LED unit 24 can be lowered, whereby the magnitude of the current i
flowing through the LED unit 24 can be stabilized so as to f d within
the predetermined range (step S04).
[0165] When the magnitude of the current detected by the current
15 detectionunit 31 is higher than the predetermined upper limit (within
the circuit interrupt region illustrated in Fig. 6), the inductance variable
control unit 32 controls the circuit interrupt unit 33, so as to intempt the
AC flowing fiom the pair of input terminal parts to the rectifier circuit
unit 22 (protection against overcurrent). When the magnitude of the
20 current detected by the current detection unit 3 1 is lower than the
predetermined lower Limit (within the circuit interrupt region illustrated
in Fig. 6), the inductance variable control unit 32 controls the circuit
interrupt unit 33, so as to interrupt the AC flowing fiom the pair of input
terminal parts to the rectifier circuit unit 22 (protection against some
25 abnormalities in the current).
' [0166] Waveforms of the input voltage Vim and the current i flowing
through the LED unit 24 observed when the LED lamp 20 is lit by the
ballast 12 of the constant power regulation inverter type while the
inductance values of the variable inductance units L50, L60 are changed
according to the magnitude of the current i flowing through the LED
5 unit 24 will now be explained with reference to Figs. 8 and 9.
[0167l In Figs. 8 and 9, similar observations are performed with
different kinds of ballasts of the constant power regulation inverter type.
Figs. 8(a) and 9(a) observe the input voltage Vm of the LED lamp 20
when the total inductance value of the variable inductance units L50,
10 L60 is 100 pH, while their ordinates correspond to 50 Vldiv. Figs.
8(b) and 9@) observe the current i flowing through the LED unit 24
when the total inductance value of the variable inductance units L50,
L60 is 100 pH, while their ordinates correspond to 200 mA/div. Figs.
8(c) and 9(c) observe the input voltage Vm of the LED lamp 20 when
15 ' the total inductance value of the variable inductance uaits L50, L60 is
400 pH, while their ordinates correspond to 50 V/div. Figs. 8(d) and
9(d) observe the current i flowing through the LED unit 24 when the
totd inductance value of the variable inductance units L50, L60 is 400
pH, while their ordinates correspond to 200 d d i v .
20 [0168] The resistance value of the resistor R31 in the current detection
L& 31 is 1 a. When the voltage at their both ends is 390 mV, i.e.
when the current flowing through the LED unit 24 is 390 mA, it is taken
as a threshold. When the threshold is exceeded, the total inductance
value of the variable inductance units L50, L60 is switched ftom 100
25 pH (pattern 2) to 400 pH (pattern 1).
[0169] According to Figs. 8 and 9, it was observed that dr&atically
changing the total inductance value of the variable inductance units
L50, L6O fkom 100 pH to 400 pH increased the output voltage of the
inverter type ballast, and the output current was controlled so as to
decrease and stabilized within the predetermined range (L-value
5 invariable region) at 390m.A or less.
[0170] Observed waveforms of the input voltage Vi at the pair of input
terminal parts (between the input terminal parts 20a, 20c), voltage Vgl
at the gate terminal of the switching d e ~ cQe1 , current sensor terminal
voltage Vcs at the pin #2 of the integrated circuit IC1, voltage Vg2 at
10 the gate terminal of the switching device. 42 and current i flowing
through the LED unit 24 will now be explained according to types of
the ballast 12, with reference to Figs. 10 to 12.
[8171] Here, each of the gate terminal voltages Vgl, Vg2 and current
sensor terminal voltage Vcs are measured while taking the G m
15 terminal TG of the PWM control unit 25 as a reference (ground level).
[0172] The current i flowing through the LED unit 24 illustrated in
Figs. 10(e), 1 l(e) and 12(e) is observed as a voltage drop on an inserted
resistance (1 $2) when a total current flowing through the LED unit 24 (a
total of 90 LEDs) is inputted to the resistance; the ordinate in each of
20 Figs. 10(e) and .l l(e) corresponds to 500 d d i v , and the ordinate in
Fig. 12(e) corresponds to 200 mA/div.
[0173] Figs. 1 0(a), 1 O(b), 1 0(c), 10(d) and 1 O(e), respectively, illustrate
waveforms of the input voltage Vin, voltage Vgl at the gate terminal of
the switching device Q1, current sensor terminal voltage Vcs of the
25 integrated circuit IC 1, voltage Vg2 at the gate terminal of the switching
device Q2 and current i flowing through the LED unit 24, when the
ballast 12 used is of the glow starter type (with a secondary voltage of
200 V and a secondary current of 0.42 A).
[0174] First, as illustrated in Fig. 10(a), a utility power fkequency of
60.1 is observed as a waveform fkequency of the input voltage Vim.
5 [0175) Since this frequency is lower than the cutoff frequency set to
about 5 kHz, the integrated circuit IC1 of the PWM control unit 25
drives pulses so as to output the voltage Vgl at the gate terminal of the
switching device Q1 whose oscillation period tosc (ps) is about 22.78
(ps) in actual measurement as illustrated in Fig. 1 O(b).
10 [0176J Here, the switching device Q1 is pulse-driven at a frequency of
about 43.9 HZ by alternately inputting the gate terminal with voltages
at a high level (about 7.5 V DC) and a low level (about 0 V) with a duty
ratio of about 33%.
[0177] As illustrated in Fig. 10(c), this is due to a PWM control action
15 of the integrated circuit IC1, which outputs voltages at the high level
(about 7.5 V DC) to the gate terminal of the switching device Q1 until
the current sensor terminal voltage Vcs reaches about 250 mV DC, and
outputs voltages at the low level (about 0 V) to the gate terminal of the
switching device Q1 after the current sensor terminal voltage Vcs
20 reaches about 250 mV DC.
[0178] When the voltage at the high level (about 7.5 V DC) is inputted
to the gate terminal of the switching device Q1, switching it on, a
. current flows through the resistors R3 to R5, thereby linearly raising the
current i flowing through the LED unit 24; when the voltage at the low
25 level (about 0 V) is inputted to the gate terminal of the switching device
Ql, the switching device Q1 switches off, and thus the current sensor
terminal voltage Vcs drops to the ground level (0 V).
[0179] On the other hand, since the firequency of the waveform of the
input voltage Vin is lower than the cutoff fiequency that was set to
about 5 kHz, only a voltage of about 50 mV DC is inputted to the gate
5 terminal of the switching device 42 through the above-mentioned
high-pass filter circuit as illustrated in Fig. 10(d), switching off the
switching device 42, and thus a current does not flow &om the drain
terminal, to the source terminal.
[0180] Hence, as flustrated in Fig. 10(e), the current i flowing through
10 the LED unit 24 flows in synchronization with the voltage Vgl at the
gate terminal of the switching device Q1, rises when the switching
device Q1 is switched on, and begins to fd1 when the switching device
Q1 is switched off (the counter-electromotive force caused by the choke
coils L1 to L4 keeps the current i fiom immediately dropping to 0 A).
15 [0181] That is, the current i flowing through the LED unit 24 is PWM
controlled by the PWM control unit 25 driving pulses at a fiequency of
about 43.9 kHz, as illustrated in Fig. 10(b).
[0182] As a result, as illustrated in Fig. 10(e), the current i flowing
through the LED unit 24 is outputted as pulses (triangle waves) at a
20 kequency of 43.7 &, which is higher than the cutoff &equency of 5
Eli in the fkequency measurement, and was observed as about 192.2
mA in effective value (RMS value) measurement.
[0183] Figs. 1 l(a), 1 l(b), 1 l(c), 1 l(d) and 1 l(e), respectively, illustrate
waveforms of the input voltage Vin, voltage Vgl at the gate terminal of
25 the switching device Q1, current sensor terminal voltage Vcs of the
integrated circuit IC1, voltage Vg2 at the gate terminal of the switching
device Q2 and current i flowing through the LED wnit 24, when the
ballast 12 used is of the rapid start type (with a secondary voltage of 190
V and a secondary current of 0.42 A).
[0184] First, as illustrated in Fig. ll(a), a fiequency of 60.1 Hz is
5 observed as a waveform frequency of the input voltage Vin.
[0185] Since this frequency is lower than the cutoff frequency that was
set to about 5 kHz, the integrated circuit IC1 of the PWM control unit
25 drives pulses so as to output the voltage Vgl at the gate terminal of
the switching device Q1 whose oscillation period tosc (ps) is about
10 22.7 8 (ps) in actual measurement, as illustrated in Fig. 1 1 (b).
[0186] Here, the switching device Q1 is pulse-driven at a fiequency of
about 43.9 kHz by alternately inputting voltages at a high level (about
7.5 V DC) and a low level (about 0 V) with a duty ratio of about 43% to
the gate terminal.
15 [018q As illustrated in Fig. ll(c), this is due to a PWM control action
of the integrated circuit IC1, which outputs voltages at the high level
(about 7.5 V DC) to the gate terminal of the switching device Q1 until
the current sensor terminal voltage Vcs reaches about 250 mV DC, and
outputs voltages at the low level (about 0 V) to the gate terminal of the
20 switching device Q1 after the current sensor terminal voltage Vcs
reaches about 250 mV DC.
[0188] When the voltage at the high level (about 7.5 V DC) is inputted
to the gate terminal of the switching device Q1, switching it on, a
current flows through the resistors R3 to R5, thereby Linearly raising the
25 current i flowing through the LED unit 24; when the voltage at the low
level (about 0 V) is inputted to the gate terminal of the switching device
Q1, the switching device Q1 switches off; and thus the current sensor
terminal voltage Vcs drops to the ground level (0 V).
[OBS9] On the other hand, since the fiequency of the waveform of the
input voltage Vi is lower than the cutoff fkequency that was set to
about 5 kHz, only a voltage of about 50 mV DC is inputted to the gate
terminal of the switching device 42 through the above-mentioned
high-pass filter circuit as illustrated in Fig. ll(d), switching off the
switching device Q2, and thus a current does not flow fiom the drain
terminal to the source terminal.
[0190] Hence, as illustrated in Fig. 1 l(e), the current i flowing through
the LED unit 24 flows in synchronization' with the voltage Vgl at the
gate terminal of the switching device Q1, rises when the switching
device Q1 is switched on, and begins to fall when the switching device
Q1 is switched off (the counter-electromotive force caused by the choke ,
coils L1 to L4 keeps the current i fbm immediately dropping to 0 A).
[0191] That is, the current i flowing through the LED unit 24 is PWM
controlled by the PWM control unit 25 driving pulses at a fiequency of
about 43.9 kHz, as illustrated in Fig. 11 (b).
[0192] Consequently, as illustrated in Fig. ll(e), the current i flowing
through the LED unit 24 is outputted as pulses (triangle waves) at a
fiequency of 43.6 k-Hz, which is higher than the cutoff fiequency of 5
kHz in the fiequency measurement, and was observed as about 195.7
nA in effective value (RMS value) measurement.
[0193] Figs. 12(a), 12(b), 12(c), 12(d) and 12(e), respectively, illustrate
waveforms of the input voltage Vim, voltage Vgl at the gate terminal of
the switching device Q1, current sensor terminal voltage Vcs of the
integrated circuit IC1, voltage VgZ at the gate terminal of the switching
device Q2 and current i flowing through the LED unit 24, when the
balIast 12 used is ofthe inverter type (with a secondary voltage of 280 V
and a secondary current of 0.225 A under no load).
5 [0194] First, as illustrated in Pig. 12(a), in the waveform of the input
voltage Vin, the period tl is about 13.7 (ps), and a fiequency of 73.0
kHz is observed.
[0195] Since this fiequency is higher than the cutoff fiequency that was ,
set to about 5 the gate terminal of the switching device Q2 is
10 inputted with the voltage Vg2 at a high level (about 14 V DC) as
illustrated in Fig. 12(d), and thus the switching device 42 is always in
the on state.
[0196] However, the resistors R3, R4, R5 are connected in parallel
between the terminals T9, TG as mentioned above, and thus .the current
15 i having flowed thrbugh the LED unit 24 hardly £lows through the
PWM control unit 25, and flows directly fiom the cathode-side terminal
TK of the LED unit 24 to the ground-side output terminal T5 of the
rectifier circuit unit 22 through the GND terminal TG of the P W
control unit 25.
20 [01197] As a result, the current i does not flow through the resistors R3
to R5, and thus the current sensor terminal voltage Vcs is stable at the .
ground level (0 V) as illustrated in Fig. 12(c), the duty ratio of the
driving pulses becomes 100% as illustrated in Fig. 12@), the voltage
Vgl at the gate terminal of the switching device Q1 in the PWM control
25 unit 25 is always at the high level (about 7.5 V DC), and the switching
device Q1 is in the on state.
[0198] Hence, the PWM control init 25 does not perform PWh4 control
of tbe current i flowing through the LED unit 24.
[0199] As illustrated in Fig. 12(e), the current i flowing through the
LED unit 24 attains a waveform in which the input voltage Vin is
full-wave rectified without PWM control by the PWM control unit 25,
and was observed as about 199.3 mA in effective value (RMS value)
measurement.
[0200] Furtheemore, without the PWM control by the driving pulses of
the PWM control unit 25, the period t2 of the ripple voltage waveform
part superposed on the DC becomes about 6.9 (ys), and the fiequency of
the current i flowing through the LED unit 24 was observed as about
145.4 Id3, which is twice as high as that of the input voltage Vin. .
[0201] Therefore, it could be confirmed that the fiequency of the ripple
voltage waveform part of the current i flowing through the LED unit 24
becomes'twice as high as that of the input voltage Vin through full-wave
rectification.
I02021 From the foregoing observations, it was confirmed that 190 mA
to 200 mA can be obtained in actual measurement as an effective value
(RMS value) of the current i flowing through the LED unit 24, and the
latter can be lit for illumination, regardless of whether the ballast 12 of
the illumination device 10 is of the glow starter, rapid start or inverter
lighting type.
[0203] It was also confirmed that, when the ballast 12 is of the glow
starter or rapid start type, the cwent i flowing through the LED unit 24
is PWM controlled by the PWM control unit 25 driving pulses at a
fiequency of about 43.6 to 43.7 kHz, which is higher than the cutoff
fiequency of 5 kHz, since the fiequency of the input voltage Vin is
about 60 Hz.
[0204] When the ballast 12 is of the inverter type, on the other hand, it
was confirmed that the fiequency of the input voltage Vin is about 73.0
5 kHz, which is higher than the cutoff frequency of 5 kHz, and thus the
current i flowing through the LED unit 24 is about 145.4 kHz and is not
PWM controlled by the PWM control unit 25 driving pulses.
[0205l The technical scope of the present invention is not limited to any .
. .
of the embodiments mentioned above but may be modified in various
10 ways within the scope set forth in the claims, and includes modified
examples of the embodiments which can be obtained by appropriately
combining technical means respectively disclosed in different
embodiments.
[020q For example, the present embodiment exemplified a mode
15 ' including the PWM control unit 25, the smoothing circuit unit 23 and
the bypass circuit unit 26, so as to enable lighting for ill-tion which
can be lit under PWM control by driving pulses by replacing a
previously mounted fluorescent lamp (or LED lamp), regardless of
whether a ballast of a fluorescent lamp lighting device is of the glow
20 starter, rapid start or inverter lighting type. However, as illustrated in
Fig. 13, which is one of modified examples, the LED lamp 200 may be
a mode that does not include the PWM control unit 25, the smoothing
circuit unit 23 and the bypass circuit unit 26 illustrated in Fig. 1. In
Fig. 13, constituent elements having the same bctions as those
25 illustrated in Fig. 1 are referred to with the same signs.
[0207 Here, since the LED lamp 200 is a mode that does not include
the PWM control unit 25, the smoothing circuit unit 23 and the bypass
circuit unit 26, it is unable to perform PWM control by driving pulses
according to the fiequency of the AC inputted to the pair of input
terminal parts, and thereby cannot perform PWM control by driving
pulses at a high fiequency when mounted to a ballast of the glow starter
or rapid start type, but can stabilize the magnitude of the current i
flowing through the LED unit 24 to fall within a predetermined range as
mentioned above when mounted to the ballast of the inverter type.
[0208] Furthermore, a pair of input terminal parts is meant to include at
least one pair of input terminal parts; when there are four input terminal
parts (two on each side), i.e. as in terminals on both end parts of a
straight tube fluorescent lamp, it would be sufficient for an external AC
to be inputted to at least two of the input terminal parts (two terminals
from one side or both sides).
[Q209] When two terminals are connected to each other simply with a
lead through another terminal, the above-mentioned description of
embodiments assumes that the two terminals are directly connected to
each other (at the same potential), and ignores the wiring resistance and
the like.
[0260] Furthermore, the predetermined fiequency distinguishing the
frequency of the AC inputted to the pair of input terminal parts is
preferably about 5 kHz (cutoff fiequency) which can distinguish
between a utility power frequency (50 Hz or 60 Hz) in the case of the
glow starter or rapid start type ballast, and a high flequency (about 20
k%z to 100 kHz) in the case of the inverter type, but may appropriately
be set so as to become a desirable Grequency within the frequency range
of higher than 65 Hz but lower than 20 kIJz by changing circuit
constants in the high-pass filter circuit.
[0211] Similarly, the frequency and duty ratio of pulses driven by the
PWM control unit may be set by appropriately configuring resistors
5 connected to pins, drive voltage and the like within the spec range of the
integrated circuit IC1 in view of the current flowing through the LED
unit (illuminance), the heat of the switching device in the PWM control
unit, and the like.
[0212] In particular, circuit configurations and circuit constants in the
10 circuit diagrams used for reference may appropriately be selected within
a range included in the technical scope of the present invention as long
as they achieve the intended objective of the present invention and yield
desired effects, even when not clearly specified in the above-mentioned
description of embodiments.
15 [0213] With reference to Figs. 14(a) and 14(b), a case where LED
lamps 50,60, each having the same configuration as with the LED lamp
20, are connected in series, mounted to a series rapid type ballast and lit
will be explained.
[0214]1 First, as illustrated in Fig. 14(a), connecting a plurality of
20 resistors R20, R21, a zener diode D20 and a resistor R22 in series
between the high-voltage (HV)-side output terminal T7 and the
ground-side output terminal T5, and inputting a DC voltage (a voltage
which is lower than about 250 mV DC and proportional to the
magnitude of the high voltage (HV)), which has been divided at the
25 resistor R22,. to the pin #7 of the integrated circuit IC1, enables the
threshold voltage to be made variable in proportion to the magnitude of
the voltage inputted to the pair of input terminal parts.
[0215] For example, selecting 1 MC2 as the resistance value of the
resistor R20, 1 MS2 as the resistance value of the resistor R21, 51 V as
the zener voltage of the zener diode D20, 3.65 kQ as the resistance
5 value of the resistor R22 and 1 pF as the capacitance of the capacitor
C20 inputs about 215 mV in actual measurement to the pin #7 of the
integrated circuit IC1 when 165 V is outputted through the high-voltage
0 - s i d e output terminal T7.
[0216] In this way, the voltage inputted to the pair of input terminal
10 : parts, and the current flowing through the LED unit that is P W
controlled, increase and decrease in proportion to each other, and thus
the input impedance of the whole LED lamp in terms of the pair of input
terminal parts is made positive (the flowing current increases
proportionally as the input voltage becomes higher).
15 ' [0217] Hence, even when the LED lamps 50, 60 having the same
configuration as with the LED lamp 20 according to the embodiment
are connected in series in a series rapid type ballast as illustrated in Fig.
14(b), the voltage inputted fiom the series rapid type ballast is
proportionally distributed according to their respective input
20 impedances, thus facilitating the flow of the same drive current through
both, and also enabling the LED lamps in the present embodiment to be
connected in series.
Industrial Applicability
[Q218] As in the foregoing, the LED lamp, illumination device
25 including the LED lamp and crnrent control method of the LED lamp of
the present invention can be applied for use as an LED lamp, an
illumination device including the LED lamp and a current control
method of an LED lamp, capable of stabilizing the magnitude of the
current flowing through an LED unit within a predetermined range, by
replacing a previously mounted fluorescent lamp (or LED lamp),
regardless of whether a ballast of a fluorescent Imp lighting device is
of the glow starter, rapid start or inverter lighting type.
Reference Signs List
[02119] 10, 100 illumination device
11 plug
12 ballast
20,50,60,200 LED lamp
20a, 20b, 20c, 20d input terminal part
21 protection circuit unit
22 rectifier circuit unit
23 smoothing circuit unit
24 LEDunit
25 PWM control unit
26 bypass circuit unit
31 current detection unit
R3 1 resistor
C3 1 capacitor
32 inductance variable control unit
33 circuit interrupt unit
34 threshold element
D34a, D34b zener diode
RY34 relay
L50, L60 variable inductance unit
L5 1, L52, L61, L62 inductor
32a, 32b, 32c switch element
Cl,C2,C9,ClO,Cll,C12,C20 capacitor
C3, C4, C5 electrolytic capacitor
C6 first capacitor
C7 second capacitor
D2, D3, D4, D5, D6, D7 diode
D8 second diode
D9 first diode
D 1, D 10, D20 Zener diode
Z9,ZlO,Zll,Z12 inputcircuitunit
HV high voltage
F1 fuse
IC 1 integrated circuit
L1, L2, L3, L4 choke coil
QLQ2 switching device
Rl, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R20, R21,
R22 resistor
R13 first resistor
R14 second resistor
RT resistance value
SA1 two-electrode discharge tube
SA2 varistor
Sol, S02, S03, SO4 step
T 1, T2, T3, T4, T6, T8, T9, T11, T 12 terminal
T5
T7
TA
TK
TG
Vin
vcs
Vgl
vg2
i
tosc
tl, t2
ground-side output tenninal
high-voltage (KV)-side output terminal
anode-side terminal
cathode-side terminal
GND tenninal
input voltage
current sensor terminal voltage
voltage at the. gate terminal of the switching device Q1
. . .. voltage at the gate terminal of the switching device Q2 '
current flowing through the LED unit
oscillation period
period
We claim:
1. An LED lamp including a pair of input terminal parts; a
rectifier circuit unit rectifying an AC, inputted from the outside to the
5 pair of input terminal parts, to a DC; and an LED unit emitting light
by electr5cation of the DC outputted from the rectifier circuit unit; the
LED lamp having:
a variable inductance unit, in a circuit between the pair of input
terminal parts and the rectifier circuit unit, for causing the AC to flow
10 from one of the pair of input terminal parts to the other input terminal
part through the rectifier circuit unit;
a current detection unit, in a circuit between the rectifier circuit
unit and ' the LED unit, for detecting a magnitude of the DC flowing
through the LED unit;
15 . an inductance variable control unit for making an inductance
value of the variable inductance unit variable according to the
magnitude of the DC detected by the current detection unit; and
a PWM control unit, in a circuit between the rectifier circuit unit
and the LED unit, capable of PWM control of a current flowing through
20 the LED unit according to a duty ratio;
wherein the PWM control unit is switchable between a case
where the PWM control of the current flowing through the LED unit is
performed, and a case where PWM control of the current flowing
through the LED unit is not performed, according to a frequency of the
25 external AC inputted to the pair of input terminal parts; and
.wherein, in the case where the PWM control unit does not
performs PWM control, the current detection unit detects the magnitude
of the DC flowing through the LED unit, and the inductance variable
control unit makes the inductance value of the variable inductance unit
variable according to the magnitude of the DC.
2. An LED lamp according to claim 1, further comprising a
threshold element, in a circuit between the pair of input terminal parts
and the rectifier circuit unit, for causing the AC to flow from one of the
pair of input terminal parts to the other input terminal part through the
rectifier circuit unit;
wherein the threshold element is adapted to short-circuit both
ends thereof after a lapse of a predetermined time from when the AC
exceeding a predetermined threshold is inputted to the pair of input
terminal parts from the outside; and
where'in the inductance variable control unit makes the
inductance value of the variable inductance unit variable according to
the magnitude of the DC detected after the both ends of the threshold
element are short-circuited.
3. An LED lamp according to claim 1 or 2, further comprising a
circuit interrupt unit, in a circuit between the pair of input terminal parts
and the rectifier circuit unit, capable of interrupting the AC flowing
from one of the pair of input terminal parts to the other input terminal
part through the rectifier circuit unit;
wherein the circuit interrupt unit interrupts the AC when the
magnitude of the DC detected by the current detection unit is higher
than a predetermined upper limit or lower than a predetermined lower
limit.
4. An illumination device including the LED lamp according to
any one of claims 1 to 3.
5. A current control method of an LED lamp including a pair of
5 input terminal parts; a rectifier circuit unit rectrfying an AC, inputted
from the outside to the pair of input terminal parts, to a DC; and an
LED unit emitting light by electrification of the DC outputted from
the rectifier circuit unit, the method comprising the steps of:
causing the AC, in a circuit between the pair of input terminal
parts and the rectifier circuit unit, to flow from one of the pair of
input terminal parts to the other input terminal part by way of the
rectifier circuit unit through a variable inductance unit;
switching between a case where the PWM control of the current
flowing through the LED unit is performed, and a case where PWM
control of the current flowing through the LED. unit is not performed,
according to a frequency of the,external AC inputted to the pair of input
terminal parts, wherein the switching is performed by a PWM control
unit, in a circuit between the rectifier circuit unit and the LED unit,
capable of PWM control of a current flowing through the LED unit
according to a duty ratio;
detecting, in the case where the PWM control unit does not
perform PWM control, a magnitude of the DC flowing through the LED
unit in a circuit between the rectifier circuit unit and the LED unit; and
making an inductance value of the variable inductance unit
variable according to the detected magnitude of the DC in the case
where the PWM control unit does not perform PWM control;
wherein the magnitude of the DC flowing through the LED unit
is controlled so as to fall within a predetermined range.
Dated this 22" day of July, 2014.
(Dev ~obinson)
of Amarchand & Mangaldas &
Swesh A. Shroff & Co.
Attorneys for the Applicant