1. An LED lamp including a pair of input tenninal parts, a rectifier circuit unit rectifying an AC inputted from the outside to the pair of input terminal parts to a DC, and an LED unit emitting light by 5 electrification of the DC outputted from the rectifier circuit unit; wherein a PWM control unit capable of performing PWM control of a current to flow through the LED unit according to a duty ratio is provided in a circuit between the rectifier circuit unit and the LED unit; and 10 . 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 the 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. 15 2. An LED lamp according to claim 1, wherein the PWM control unit performs the PWM control of the current flowing through the LED unit by driving a pulse at a frequency higher than a predetermined fiequency when a fi-equency of external AC inputted to the pair of input terminal parts is lower than the predetermined fiequency, and does 20 not perform the PWM control of the current flowing through the LED unit when the frequency of the external AC inputted to the pair of input terriinal parts is higher than the predetermined frequency. I

3. An LED lamp according to claim 2, wherein a bypass circuit unit is provided between a cathode-side terminal of the LED unit and a 25 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 fiom the cathode-side terminal of the LED ' unit to the ground-side 5 output terminal of the rectifier circuit unit when the AC inputted to the pair of input terminal parts has a fiequency lower than the predetermined fiequency, and allows a current to flow fiom the . cathode-side terminal of the LED unit to the ground-side output terminal of the rectifier circuit unit when the AC inputted fiom the pair 10 of input terminal parts has a frequency higher than the predetermined . - frequency.

4. An LED lamp according to claim 3, 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 15 . 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 tenninal of the rectifier circuit unit; 20 wherein the gate terminal is connected to any one of 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 tenninal driven so as to allow a current to flow from the drain 25 terminal to the source terminal when the AC inputted to the pair of input terminal parts has a fiequency higher than the predetermined frequency, and outputs a gate voltage to the gate terminal driven so as not to allow a current to flow from the drain terrninal to the source terminal when the AC inputted to the pair of input terminal parts has a fiequency lower than the predetermined fiequency.

5. An LED lamp according to claim 4, wherein the high-pass filter circuit includes: a first capacitor; a first resistor connected in series to the first capacitor so as to have one terminal connected to one terminal of the first capacitor; a first diode comeded in a forward direction from the other terminal of the fxst resistor to the gate terminal; a second capacitor connected between the source and gate terminals; a second resistor connected between the source and gate tenninals; a Zener diode connected a forward direction fiorn the source terminal to the gate terminal; and a second diode connected a forward direction fkom the source terminal to the other terminal of the first resistor; wherein the other terminal of the first capacitor is connected to any one of the input tenninals of the rectifier circuit unit.

6. An LED lamp according to any one of claims 2 to 5, wherein the predetermined frequency is a frequency higher than 65 Hz but lower than 20 kHz.

7. An illumination device including the LED lamp according to any one of claims 1 to 6. Dated this 24m day of July, 20 14.

Title of Invention
LED LAMP AND ILLUMINATION DEVICE INCLUDING THE LED
LAMP
~ichnicaFl ield
[0001] The present invention relates to an LED lamp, and an
illumination device including the LED, capable of driving an LED unit
incorporated therein at a high fiequency to light even when mounted in
place of fluorescent lamps of various glow starter, rapid start and
inverter lighting device types distributed on the market.
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 kHz) near
a resonance frequency.
[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.
[0005J This is superior to the conventional magnetic ballasts of the
glow starter and rapid start trpes using choke coils in terms of such
characteristics as lower power, higher efficiency, usability at both 50 Hz .
5 or 60 Hz, lower noise and indiscernibility of flicker.
j0006) These will now be explained with reference to the drawings.
[0007] Fig. 8(a) iS a diagram illustrating an example of glow starter
type ballasts, Fig. 8(b) is a diagram illustrating an example of rapid start
type ballasts, and Fig. 8(c) is a diagram. illustrating an example of
10 inverter type ballasts.
[0008] The glow starter type ballast illustrated in Fig. 8(a), which is the
most popular type, preheats electrodes (also referred to as filaments; the
same hereinafter) of a fluorescent imp with a starting device using a
glow starter (G), so as to enable lighting in a few seconds after
15 switching on.
[0009] The rapid start type ballast illustrated in Fig. 8(b), which is used
in combination with a rapid start type lamp, is lit instantaneously and
simultaneously with preheating when switched on.
[0060] On the other hand, the ballast of the inverter type lighting device
20 illustrated in Fig. 8(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 lamp at a high frequency such as that mentioned above (e.g. see
page 4 and Fig. 2 of Patent Literature 1).
[00111] While a choke coil L is inserted in series with the LED lamp in
25 order to smooth the current flowing through the LED lamp in this case,
an electrolytic capacitor (not depicted) is typically inserted in parallel
with the LED lamp.
[0012] Fig. 9 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
5 connected in series and lit by a single ballast, is simpler and less
expensive than one using two single-lamp ballasts or a flickerless
bdlast.
[Om41 When powered, the electrodes of each of fluorescent lamps A
and I3 are preheated, and the secondary voltage does not shift to normal
10 discharging but attains a weakly discharging state due to a starting
capacitor having a high impedance. The lowered voltage at both ends
of the starring capacitor caused by the weak discharge current is applied
to the fluorescent lamp B, and starts to discharge the fluorescent lamp
B.
15 [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
20 can light two fluorescent lamps in series at a relatively low secondary
voltage, but is disadvantageous in that both of the fluorescent lamps fqil
to light when one of them is removed for power saving or has burnt out.
Citation List
Patent Literature
25 [0017] Patent Literature 1 : Japanese Laid-Open Patent Application No.
201 0-34012
Summary of Invention
Technical Problem
[QQl8]F or saving power, lengthening the life of lamps and so forth,
more and more LED lamps have been seen in use as being mounted to
5 various types of ballasts mentioned above in place of the conventional
fluorescent lamps.
[0019] In this case, the peak value and fiequency 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
10 makes it necessary to use respective LED lamps corresponding to the
ballasts.
[0020] In 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
15 power-supply-side input of 100 V to 240 V AC (50 Hz or 60 Hi), but
since the fiequency is not controlled so as to become a high frequency,
the fiequency is the same as that of the power-supply-side input.
[0021] 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
20 fkequency of the power-supply-side input, and then the circuit
configuration of an LED unit of the LED lamp (the configuration of a
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
through each LED is made to fall within a desirable range.
25 [0022] Hence, when the ballast of the fluorescent lamp lighting device
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.
COO231 On the other hand, as mentioned above, even when the
power-supply-side input is 100 V to 240 V AC (50 %.or 60 Hz) in the
5 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
frequency is under constant-current or constant-power control to fall
within the range of 20 kHz. to 100 kHz, the circuit configuration of the
10 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 fd
within a desirable range,
[0024] Therefore, when the ballast of the fluorescent lamp lighting
device is of the inverter type, it has been necessary to take
15 commensurate measures on the lighting device or LED lamp side that
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 ACDC converter (rectifier circuit) incorporated in the
20 LED lamp bypassing (not driving) the inverter type ballast.
[0025] 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.
25 [0026] As shown above, the need for selecting and deselecting
(verifymg 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, have caused users to
investigate the current state for implementation and construction, adjust
the construction period, and so forth, which are troublesome and
5 increase the implementation cost.
[0027l That is, these factors have been hindering LED lamps f?om
being employed in conventional fluorescent lamp lighting devices in
homes and offices,
[0028] As a result, previous fluorescent lamps continue to be used as
10 they are, thereby greatly obstructing market diffusion of LED lamps,
which can greatly contribute to saving power and lengthening the life of
lamps.
[0029] It is an object of the present invention to provide an LED lamp,
and an illumination device including the LED lamp, capable of being lit
15 by .driving pulses at a high frequency, by replacing the previously
mounted fluorescent lamp (or LED lamp), regardless of whether a
ballast of an illumination device is of a glow starter, rapid start or
inverter lighting type.
Solution to Problem
20 [0030] For solving the conventional problems mentioned above, the
LED lamp according to the present invention is an LED lamp including
a pair of input terminal parts, a rectifier circuit unit rectifjing 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
25 fiom the rectifier circuit unit; wherein a PWM control unit capable of
performing PWM control of a current flowing through the LED unit
according to a duty ratio is provided in a circuit between the rectifier
circuit unit and the LED unit; and 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 the PWM
5 co&l of the current flowing through the LED unit is not performed,
according to a frequency of the external AC fed to the pair of input
terminal parts.
[8031] This makes it possible to light the LED lamp for illumination, '
which is capable of being lit by pulse-driven PWM, by replacing a
10 previously mounted fluorescent lamp (or LED lamp), regardless of
whether a ballast of the fluorescent lamp lighting device is of the glow
starter, rapid start or inverter lighting type.
[0032] Furthermore, in addition to the foregoing configuration, the
LED lamp of the present invention is one wherein preferably the PWM
15 controleunit performs the PWM control of the current flowing through
the LED unit by driving a pulse at a fiequency higher than a
predetermined fiequency when a fiequency of an external AC inputted
to the pair of input terminal parts is lower than the predetermined
frequency, and does not perfonn the PWM control of the current
20 flowing through the LED unit when the frequency of the external AC
inputted to the pair of input terminal parts is higher than the
predetermined fiequency.
[0033] This configuration makes it possible to light the LED lamp for
illumination, which is capable of being lit by driving a pulse at a
25 frequency higher than the predetermined fi-equency, by replacing the
previously mounted fluorescent lamp (or LED lamp), regardless of
whether the ballast of the fluorescent lamp lighting device is of the glow
starter, rapid start or inverter lighting type.
[0834] Therefore, this can easily eliminate the need for selecting and
deselecting (verifying compatibility of) LED lamps according to types
5 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 the implementation cost.
10 [00351 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.
[0036] This makes it possible for LED lamps, which can greatly
contribute to saving power and lengthening the life of lamps, to become
15 widespread in the market.
[0037 When the ballast of a fluorescent lamp lighting device is of the
glow starter or rapid start type, for example, the frequency of the AC
inputted from the pair of input terminal parts is a utility power
fkequency of 50 Hz or 60 Hz.
20 [0038] Therefore, the current flowing through the LED unit is
PWM-controlled by driving pulses at a frequency higher than at least a
predetermined fkequency (e.g. 5 kHz), thus enabling the PWM control
unit to repeatedly switch the current flowing through the LED unit
on/off at high speed, and a flicker-fi-ee, stable effective value (RMS
25 value) to be obtained.
[0039] 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 Eequency of 20 kHz to 100 kHz, and thus the
PmZWI control unit does not perform PWM control, the frequency
rectified by the rectifier circuit unit is used as is (a ripple voltage
5 waveform part superposed on the DC having a double fkequency in the
case of fill-wave rectification), and thus the current flowing through the
LED unit can obtain a flicker-free, stable effective value (RMS value)
by control (e.g. PWM control) of the external inverter type ballast.
[0040] This reliably prevents the same kind of control systems from
10 being superposed outside and inside of the LED lamp, and eliminates
causes giving rise to inconsistencies such as instability in the current
flowing through the LED unit.
[004I] Furthermore, in addition to the foregoing configuration, the
LED lamp of the present invention is one wherein preferably a bypass
15 circuit unit is provided bemeen 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 dow a current to flow from the
20 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 fkequency lower than the predetermined
frequency, and allows a current to flow fkom the cathode-side terminal
of the LED unit to the ground-side output terminal of the rectifier circuit
25 unit when the AC inputted to the pair of input terminal parts has a
frequency higher than the predetermined frequency.
I00421 This configuration allows the AC inputted fiom the input
terminal of the rectifier circuit, when higher than the predetermined
frequency, to bypass (circumvent) the switching device of the PWM
control unit for performing PWM control of the current flowing through
5 the LED unit, thereby preventing the PWM control unit incorporated in
the LED lamp fiom performing the PWM control.
[0043J Furthennore, in addition to the foregoing configuration, the
LED lamp of the present invention is one wherein preferably the
switching device of the bypass circuit unit is an N-channel MOSFET
10 controlling a current flow between drain and source terminals according
to a gate voltage inputted to a gate terminal, wherein the drain tenninal
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 tenninal is connected to any one
15 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 terminal parts has a frequency higher than the
20 predetermined frequency, and outputs a gate voltage to the gate terminal
driven so as not to allow a current to flow from the drain tenninal to the
source terminal when the AC inputted to the pair of input terminal parts
has a frequency lower than the predetermined frequency.
[0044] According to this configuration, the N-channel MOSFET
25 hctions 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.
[0045] That is, since the PWM control uait is bypassed (circumvented)
when the AC inputted fjrom the input terminals of the rectifier circuit '
unit has a fjrequency higher than the predetermined fiequency, the
5 current flowing through the LED unit can be prevented fiom flowing
into the PWM control unit, and prevents the PWM control u3lit fiom
performing PWM control.
[0046] Furthermore, in addition to the foregoing configuration, the
LED lamp of the present invention is one wherein preferably the
10 high-pass filter circuit includes a h t capacitor, a &st resistor
connected in series to the first capacitor so as to have one terminal
connected to one terminal of the first capacitor, a first diode connected
in a fonvard direction fiom the other terminal of the first resistor to the
gate terminal, a second capacitor connected between the source and gate
15 terminals, a second resistor connected between the source and gate
terminals, a zener diode connected in a forward direction fiom the
source tenninal to the gate terminal, and a second diode connected in a
forward direction fiom the source terminal to the other terminal of the
first resistor, wherein the other terminal of the first capacitor is
20 connected to any one of the input terminals of the rectifier circuit unit.
[0047J 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.
25 [0048] 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 PPSrM control of the current flowing through
the LED unit.
5 100491 Furthermore, in addition to the configurations mentioned above,
the LED lamp of the present invention is one wherein preferably the
predetermined frequency is a frequency higher than 65 Hz but lower
than 20 kHz.
[0050] This configuration makes it possible to clearly distinguish
10 between a frequency (60 1 Hz) 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
15 control is perform.e d, . 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.
[0051] Since the predetermined fkequency to be distinguished is a
20 frequency which is lower than 20 kHz and falls within an audible region
(a frequency band which can be sensed by humans as sound), a
frequency in a higher fiequency band used for driving pulses for PWM
control is less likely to be felt as uncomfortable noise.
[0052] Furthermore, the illumination device of the present invention is
25 one including the LED lamp having any of the configurations
mentioned above.
[0053J According to this configuration, the illumination device of the
present invention is mounted with the LED lamp according to the
present invention, and thus it is not necessary to newly provide a ballast
for modulating the 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.
[0054] 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 (verify'ing
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
the implementation cost.
Advantageous Effects of Invention
[0055] According to the LED lamp and the illumination device
including the LED lamp of the present invention, it is possible to
provide an LED lamp, and an illumination device including the LED
lamp, capable of being lit by driving a pulse at a high frequency,
regardless of whether the ballast of the fluorescent lamp lighting device
is of the glow starter, rapid start or inverter lighting type.
Brief Description of Drawings
[0056) Fig. 1 is a block diagram illustrating 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 an embodiment of
the present invention.
Fig. 3 is a block diagram illustrating the inside of an integrated
circuit IC 1.
5 Figs. 4(a), 4(b), 4(c), 4(d) and 4(e), respectively, are waveforms
of an input voltage Vin, a voltage Vgl at a gate terminal of a switching
device Q1, a current sensor terminal voltage Vcs of an integrated circuit
ICl, a voltage Vg2 at a gate terminal of a switching device Q2, and a
current i flowing through an LED unit 24.
10 Figs. 5(a), S(b), 5(c), 5(d) and 5(e), respectively, are waveforms
of an input voltage Vim, a voltage Vgl at a gate terminal of a switching
device Q1, a current sensor terminal voltage Vcs of an integrated circuit
ICl, a voltage Vg2 at a gate terminal of a switching device 42, and a
current i flowing through an LED unit 24.
15 Figs. 6(a), 6(b), 6(c), 6(d) and 6(e), respectively, are 'waveforms
of an input voltage Vim, a voltage Vgl at a gate terminal of a switching
device Q1, a current sensor tenninal voltage Vcs of an integrated circuit
ICl, a voltage Vg2 at a gate tenninal of a switching device 42, and a
current i flowing through an LED unit 24.
20 Fig. 7(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. 7(b) is an overall block diagram in which an
LED lamp in an embodiment is connected in series to a series rapid type
ballast.
25 Figs. 8(a), 8@) and 8(c) are diagrams illustrating examples of
ballasts of glow starter, rapid start and inverter types, respectively.
Fig. 9 is a diagram illustrating an example of a series rapid type
ballast.
Description of Embodiments
[0057] Embodiments of the present invention will be explained in detail
below with reference to the drawings.
Embodiments
[0058] Fig. 1 is a block diagram illustrating 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 IC1; Figs. 4(a) to 4(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. 5(a) to 5(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 ofthe present invention; Figs. 6(a) to 6(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; and Fig, 7(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.
7@) is an overall block diagram in which LED lamps in an embodiment
are connected in series to a series rapid type ballast.
25 [0059] First, as illustrated in Fig. 1, an illumination device 10 according
to an embodiment of the present invention comprises a plug 11 that is
connected in order to sqply power fkom 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 '
5 voltage is inputted between a pair of input terminal parts (between input
terminad parts 20a, 20c) according to the type of the ballast 12.
[0060] Here, the ballast 12 may be any know glow starter, rapid start
or inverter type for lighting existing fluorescent lamps.
[0061] Since the LED lamp 20 operates normally as long as the external
10 power supply has an AC of 100 to 240 V (50 Hz or 60 Hi), the external
power may be directly inputted to the LED lamp 20, bypassing the
ballast 12.
[0062] Here, a line outputting an AC fkom the ballast 12 is connected so
as to enable inputting between either one or both of the pair of input
15 terminal parts (between input terminal parts 20a, 20c) andlor a pair of
input terminal parts (between input terminal parts 20b, 20d).
[0063] 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
20 a terminal T1 (see Fig. 2).
[0064] Similarly, an input circuit unit 210 constituted by an RC parallel
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
tenninal T1 (see Fig. 2).
25 [0065] Similarly, an input circuit ~t 21 1 constituted by an RC parallel
circuit composed of a resistor R11 and a capacitor C11 is connected
between the input terminal part 20c of the LED lamp 20 and a terminal
T2 (see Fig. 2).
[OQQq Similarly, an input circuit unit 212 constituted by an RC parallel
circuit composed .of a resistor R12 and a capacitor C12 is connected
5 between the input terminal part 20d of the LED lamp 20 and the
terminal T2 (see Fig. 2).
[0867] Therefore, a resistance value of about several C2 to about 100 SZ
is selected. for each of the resistors R9, R10 between the input terminal
parts 20a, 20b so as to conespond to the resistance component of a
10 . filament of the fluorescent lamp.
100681 Similarly, a resistance value of about several C2 to about 100 LI
is selected for each of the resistors R11, R12 between the input terminal
parts 20c, 20d so as to correspond to the resistance component of the
filament of the fluorescent lamp.
15 [0069] When the resistance values of' the resistors R9 to R12 are
selected as mentioned above, these resistors R9 to R12 can act as
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 fdament
20 resistance) and outputs no power when the fluorescent lamp is not
mounted (case where no fluorescent lamp is mounted), and thus power
is normally supplied to the LED lamp 20.
[0070] Furthermore, a protection circuit unit 21 (see Fig. 2) is inserted
between the terminals T 1, T2.
25 [0071] In the protection circuit uait 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.
[0072] 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 TI and T2 fiom the power supply side to a peak value of
about 400 V or lower. Furthermore, combining the two-eleckrode
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.
[0073] 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 fiom advancing into a
rectifier circuit unit 22 side.
[0074] Hence, electronic components such as diodes and capacitors
constituting the rectifier circuit unit 22 and LED unit 24 can be
protected.
[0075] A coil L5 is inserted between the terminal TI and a terminal T3
on one input side of the rectifier circuit unit 22, and a coil L6 is
similarly inserted between the terminal T2 and a tenninal T6 on the
other input side of the rectifier circuit unit 22.
[007q As a consequence, the coils L5, L6 act as impedances against
high-fkequency pulses.
[0077] Therefore, when the ballast 12 is of the glow starter or rapid
start type, for example, a switching device Q1 switches on/off, and thus
prevents switching noises (high-eequency noise pulses) thereof fi-om
flowing out to the external AC (input power supply) side through any of
the input terminal parts 20a to 20d
[0078] 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 lcHz is inputted,
5 and thus the coils L5, L6 act as (reactive power loss) loads without
effective power loss.
[0079] This allows power to be stably outputted fiom 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
10 the pair of input terminal parts (between the input terminal parts 20a,
20c) andor the pair of input terminal parts (between the input terminal
parts 20b, 20d).
[0080] Furthermore, the rectifier circuit unit 22 is constituted by a bridge diode composed of four diodes D4 to D7, and electrolytic
15 capacitors C4, C5 connected in parallel so as to smooth a fdl-wave
rectified waveform in the output stage of the bridge diode (see Fig. 2).
[0081] In output-side terminals of the rectifier circuit unit 22, a DC
voltage is outputted between a high-voltage (HV)-side output terminal
T7 and a ground-side output terminal T5.
20 [0082] 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
unit 23;and a cathode-side tenninal TK of the LED unit 24 is connected
to a PWM control unit 25 through the smoothing circuit unit 23.
[0083] Here, the LED unit 24 is constituted by a circuit in which three
25 LED circuit groups, each comprising 30 LEDs (light-emitting diodes)
having a forward voltage of about 3 V each and connected in series, are
connected in parallel, and a current i flows in a direction (direction of
the arrow) fiom the anode-side terminal TA to the cathode-side terminal
TK.
[0084] Additionally, a GND terminal TG of -the PWM control unit 25 is
5 connected to the ground-side output terminal T5 on the output side of
the rectifier circuit unit 22.
[0085] According to the circuit configuration mentioned above, the
current i flowing through the LED unit 24 is PWM controlled by the
PWM control unit 25 driving pulses at a fiequency higher than a
10 p-edetermined' &equency, and falls within a predetermined current value
range.
I00861 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 terminal T5 of the rectifier circuit unit 22.
15 [0087] As a result, in the case where the frequency of the AC inputted
to one terminal T3 of the rectifier circuit unit 22 is higher than the
predetermined fiequency, resistors R3, R4 and R5 are connected in
parallel between the terminals T9 and TG even when the switching
device Q1 is in the on state (the state where a current flows fiom the
20 drain terminal to the source terminal; the same hereinafter), and thus the
cment i, which bypasses (circumvents) the PWM control unit 25 and
flows through the LED unit 24, flows directly from 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.
25 [0088] Hence, the current i hardly flows through the PWM control unit
25, and thus is not PWM controlled.
[0089] In the foregoing and following explanations, performing PWM
(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
5 onloff according to the duty ratio (the ratio of pulse width to pulse
period, which has the same meaning as "on duty"; the same hereinafter)
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%
10 but smaller than 100%.
[0090] This can stabilize the magnitude of the current i flowing through
the LED unit 24.
[0091] 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
is controlling the current i so as to switch odoff according to the duty
ratio; in addition to the case where the current i hardly flows through the
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
20 the driving pulses have a duty ratio of 100% so that the switching
device Q1 is always in the on state during operation.
[0092] Individual constituent parts will now be explained in fiuther
detail with reference to Figs. 2 and 3.
[0093] While the resistor R9 between the input terminal unit 20a and
25 terminal T1 acts as a dummy resistor corresponding to the filament of
the fluorescent 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).
[0094] This can shunt the AC in inverse proportion to the ratio between
the capacitive reactance, determined by the frequency of the AC and the
5 capacity of the capacitor C9, and the resistance value of the resistor R9,
and thus proportionally suppresses the heat of the resistor R9.
[0095] SimilarIy, 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
10 normal operation state, and thus suppress the heat of the resistor Rll.
[0096] Furthermore, a h e Fl 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 tenninal parts 20% 20c) and/or
the pair of input terminal parts (between input tenninal parts 20b, 20d).
15 [0097] Next, the rectifier circuit Mit 22 has, in an upstream stage, the
. bridge diode constituted by the diode D4 whose anode and cathode are
connected to the terminal T3 and the high-voltage 0 - s i d e output
terminal T7, respectively, the diode D5 whose anode and cathode are
connected to the temxha.1 T6 and the high-voltage 0 - s i d e output
20 tennind T7, respectively, the diode D6 whose anode and cathode are
connected to the terminal T6 and a terminal T4 at the same potential as
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.
25 [OQ98] Furthermore, in a stage downstream of the bridge diode, the
111-wave rectified waveform is smoothed, and thus the electrolytic
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
5 terminal T5 side.
[0099] 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.
[OlOO] The pulsating component (ripple component) of the high DC
10 voltage outputted to the .high-voltage (HV)-side output terminal T7 is
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.
15 [OlOq Additionally, the current i, fiom which the pulsating component
has been removed by having passed through the smoothing circuit unit
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.
20 [0102] The current i having passed through the smoothing circuit unit
23 fiom the LED unit 24 is PWM controlled by driving pulses at a
predetermined oscillation period tosc (ps) by the resistors R1 to R8,
capacitors Cl, C2, a zener diode Dl, a diode D2 and the switching
device Q1, which constitute the PWM control unit 25 and are connected
25 to the integrated circuit IC1 and pins (#1 to #8).
[0103] When a commercially available model HV9910B (see Fig. 3)
manufactured by Supertex, Inc. is used as the integrated circuit IC 1, the
oscillation period tosc (ps) is controlled by the time obtained according
to the following Fomula 1 depending on the resistance value RT (kn)
of the resistor R1 connected to the pin #8.
5 Formula 11
[0104] When the resistor R1 is set to about 499 m), for example, in
the present embodiment, about 20.84 (ps) is determined as the
oscillation period tosc (ps) according to the above-mentioned Fomula
10 1.
[0105] Therefore, if the oscillation period is about 20.84 (ps) as
calculated, pulses can be driven at a high frequency of about 48 kJih.
[0106] Furthermore, the switching device Q1 controlling the on/off of
the current i flowing through the LED unit 24 is an N-channel MOSFET
15 which can control a current flow between drain and source terminals
according to the input voltage at a gate terminal.
[01071 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 source terminal is connected
20 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 from the pin #4 of the integrated circuit IC1 has
been divided by the resistors RZ, R7, is inputted to the gate terminal.
[0108] Furthermore, the pin #1 of the integrated circuit IC1 is
connected to the high-voltage (HV)-side output terminal T7 through the
resistor R8 and Zener diode Dl, and thus is supplied with the high DC
voltage outputted fiom the rectifier circuit unit 22.
5 [0109] As a consequence, the voltage (about 8 V DC to about 450 V
DC) supplied fiom the pin #1 is lowered, rectified and stabilized by an
internal regulator to a predetermined VDD voltage (about 12 V DC),
hctions as a power supply for driving the h e r circuit of the
integrated circuit ICl, and the VDD voltage is outputted to the pin #6
10 (see Fig. 3).
[OllO] 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
15 outputted to the gate tenninal 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 Ql, switching it off (a state where no current flows
20 from the drain terminal to the source terminal; the same hereinafter).
[0111] In this way, the integrated circuit ICI 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
25 of the voltage (current sensor terminal voltage Vcs) detected at the pin
#2, and the current i flowing through the LED unit is controlled.
[0112] That is, the current i is PWM controlled by the high-frequency
driven pulses of the PWM control unit, .and thus repeatedly increases
and decreases in pulses (in triangle waves) at the oscillation period tosc
(ys) obtained by the above-mentioned Formula 1 according to the
switching device Q1 that is repeatedly switched odoff.
[Ull3] Xn 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).
[0114] 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).
[0115] 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 fkther be made variable in a downward
direction.
[OX161 This can lower the effective value (RMS value) of the current i
flowing through the LED lmit 24, thereby modulating (dimming) light.
[6)117] Here, when the switching device Q1 is switched off, the series
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 Ll to the anode-side terminal TA of the LED unit 24.
[0118] On the other hand, as mentioned above, the bypass circuit unit
26 is disposed between the cathode-side terminal TK of the LED unit 24
and the ground-side output terminal T5 of the rectifier circuit unit 22.
5 [0119] The bypass circuit unit 26 includes a switching device 42 and a
high-pass filter circuit outputting a drive voltage (gate terminal voltage)
to the switching device 42.
[0120] Here, the switching device Q2 of the bypass circuit unit 26 is an
N-channel MOSFET which controls a current flow between drain and
10 source terminals according to a voltage inputted to a gate terminal, the
drain terminal is connected to the cathode-side terminal TK of the LED
unit 24, the source terminal is connected to the ground-side output
tenninal T5 of the rectifier circuit unit 22, and the gate terminal is
connected to the terminal T4 of the rectifier circuit unit 22 through the
15 high-pass filter circuit.
[0121] The high-pass filter circuit includes a first capacitor C6, a first
resistor R13 connected in series to the first 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
20 first resistor R13 to the gate terminal of the switching device Q2, a
second capacitor C7 connected between the source and gate terminals of
the switching device Q2, a second resistor R14 connected between the
source and gate terminals, a Zener diode Dl0 connected in a forward
direction f?om the source terminal to the gate terminal, and a second
25 diode D8 connected a forward direction fi-om the source terminal to the
other terminal of the first resistor R13.
[0122] The other terminal of the first capacitor C6 .is connected to any l
one of the input terminals (the terminal T3 or T6 through the terminal
T4) of the rectifier circuit unit 22.
I01231 When c;cuit constants of the first capacitor C6, first resistor
5 R13 and second resistor R14 are selected so as to cut off the AC
inputted to the terminal T3 at a predetermined fkequency or below, a CR I
circuit composed of the capacitor and resistors acts as ahigll-pass filter l
and thus only allows the AC having a fkequency exceeding the
predetermined frequency to pass therethrough to a stage downstream
10 thereof.
[0124] That is, the AC having a fkequency higher than the I
predetermined frequency inputted to the terminal T3 generates a DC I
voltage on the high voltage side of the second capacitor C7, second
resistor R14 and zener diode D10, and a voltage capable of switching on
15 the switching device 42 is outputted to the gate tennhal.
[0125] The voltage at the gate terminal can appropriately be set I
according to the potential division ratio between the first and second
resistors R13, R14, and the zener voltage of the zener diode Dl0
limiting the voltage inputted to the gate terminal, but may be set sa as to I
f d within a high-level gate terminal voltage range which can switch on
the switching device Q2.
[012q The high-pass filter circuit is an input circuit for a filter allowing
an AC having a fiequency higher than a predetermined fiequency to
pass therethrough, so as to set the gate terminal 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 180'-difference in
phase) is inputted as with the ground-side terminal T5 of the rectifier
circuit unit 22.
[0127] According to the foregoing contiguration, the high-pass filter
outputs a predetermined gate voltage allowing a current to flow fiom
5 the drain terminal to the source termind when the AC inputted to the
input terminal of the rectifier circuit unit 22 has a fkequency higher than
a predetermined fiequency (in the present embodiment, a cutoff
fiequency in actual measurement being set to about 5 kE& by choosing a
capacity of 100 pF for fhe first capacitor C6, a resistance value of 5 1 WZ
10 for the fist resistor R13, and a resistance value of 5 1 kil for the second
resistor R14; the same hereinafter), and outputs a gate voltage that does
not allow a current to flow fioni the drain terminal to the source
terminal when the AC has a fkequency lower than a predetermined
fiequency.
15 [0128] 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
fiequency lower than the predetermined frequency (about 5 kW), and
20 makes it possible for a current to flow 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 PTNM
control unit 25 when the AC has a fkequency higher than the
predetermined fiequency (hereinafter referred to as cutoff fiequency;
25 about 5 a).
[0129] As a result, when the external AC inputted to a pair of input
terminal parts has a fiequency lower than the predetermined fiequency
(e.g. when inputted fkom a ballast of the glow starter type or rapid start
type), the current i flowing through the LED unit 24 is PWM codrolled
by the PWM control unit 25 driving pulses at a frequency higher than
the predetermined fiequency, producing pulse waves (triangle waves).
[0130] On the other hand, when the external AC inputted to a pair of
input terminal parts has a frequency higher than the predetermined
fiequency (e.g. when inputted h m 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
unit 22 without PWM control being performed by the PWM control unit
[0131] Therefore, the AC having a high f?equency 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
fill-wave rectification (e.g. see Fig. 6(e)).
(01321 Observed waveforms of the input voltage Vin at the pair of input
terminal parts (between the input terminal parts 20% 20c), voltage Vgl
at the gate terminal of the switching device Q1, current sensor terminal
voltage Vcs at the pin #2 of the integrated circuit IC1, voltage Vg2 at
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. 4 to 6.
[0133] Here, each of the gate tenninal voltages Vgl, Vg2 and current
sensor tenninal voltage Vcs are measured while taking the GND
terminal TG of the PWM control unit 25 as a reference (ground level).
[0134] The current i flowing through the LED unit 24 illustrated in
5 Figs. 4(e), 5(e) and 6(e) is observed as a voltage drop on an inserted
resistance (I a) 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
Figs. 4(e) and 5(e) corresponds to 500 mAldiv, and the ordinate in Fig.
6(e) corresponds to 200 mA/div.
10 [0135] Figs. 4(a), 4(b), 4(c), 4(d) and 4(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
integrated circuit IC1, voltage Vg2 at the gate terminal of the switching
device 42 and current i flowing through the LED unit 24, when the
15 ballast 12 used is of the glow starter type (with a secondary voltage of
200 V and a secondary current of 0.42 A).
[OP3q First, as illustrated in Fig. 4(a), a utility power frequency of 60.1
Hz is observed as a waveform firequency of the input voltage Vin.
[0137l Since this frequency is lower than the cutoff fkequency set to
20 aboii; 5 Eli, 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 bc (ps) is about 22.78
(ps) in actual measurement as illustrated in Fig. 4(b).
[0138] Here, the switching device Q1 is pulse-driven at a frequency of .
25 about 43.9 lcHz 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%.
[0139] As illustrated in Fig. 4(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
switching device Ql after the current sensor terminal voltage Vcs
reaches about 250 mV DC.
[0140] When the voltage at the high level (about 7.5 V DC) is inputted
to the gate terminal of the switching device Ql, 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
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).
[014P] On the other hand, since the frequency of the waveform of the
input voltage Vin 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
terrninal of the switching device 42 through the above-mentioned
high-pass filter circuit as illustrated in Fig. 4(d), switching off the
switching device 42, and thus a current does not flow fi-om the drain
terminal to the source terminal.
101421 Hence, as illustrated in Fig. 4(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 from immediately dropping to 0 A).
[8143] That is, the current i flowing through the LED unit 24 is PWM
controlled by the PWM control unit 25 driving pulses at afiequency of
about 43.9 kHz, as illustrated in Fig. 4(b).
[0144] As a result, as illustrated in Fig. 4(e), the current i flowing
through the LED unit 24 is outputted as pulses (triangle waves) at a
fiequency of 43.7 kHz, which is higher than the cutoff fiequency of 5
kHz in the fiequency measurement, and was observed as about 192.2
rnA in effective value (EMS value) measurement.
[0143 Figs. 5(a); 5(b), 5(c), 5(d) and 5(e), respectively, illustrate
wavef&s of the input voltage Vi voltage Vgl at the gate terminal of
the switching device Q1, current sensor terminal voltage Vcs of the
integrated circuit ICl, voltage Vg2 at the gate terminal of the switching
device 42 and current i flowing through the LED'unit 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).
[014q First, as illustrated in Fig. 5(a), a fiequency of 60.1 HZ is
observed as a waveform fiequency of the input voltage Vim.
I01471 Since this frequency is lower than the cutoff fiequency that was
set to about 5 kHz, the integrated circuit IC 1 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. 5(b).
[0148] Here, the switching device Q1 is pulse-driven at a fiequency of
about 43.9 IsHz 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.
[0649] As illustrated in Fig. 5(c), this is due to a PWM control action of
the integrated circGt IC1, which outputs voltages at the high level
5 (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
reaches about 250 mV DC.
10 [0150] 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
level (about 0 V) is inputted to the gate terminal of the switching device
15 Q1, the switching device Q1 switches off, and thus the current sensor
terminal voltage Vcs drops to the ground level (0 V).
[015B] On the other hand, since the fiequency of the waveform of the
input voltage Vin is lower than the cutoff fiequency that was set to
about 5 icHz, only a voltage of about 50 mV DC is inputted to the gate
20 terminal of the switching device 42 through the above-mentioned
high-pass filter circuit as illustrated in Fig. 5(d), switching off the
switching device Q2, and thus a current does not flow from the drain
terminal to the source terminal.
[0152] Hence, as illustrated in Fig. 5(e), the current i flowing through
25 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, am$ 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 fkom immediately dropping to 0 A).
[0153] That is, the current i flowing through the LED unit 24 is PWM
5 controlled by the PWM control unit 25 driving pulses at a frequency of .
about 43.9 kJ3z, as illustrated in Fig. 5(b).
[0154] Consequently, as illustrated in Fig. S(e), the current i flowing
through the LED unit 24 is outputted as pulses (triangle waves) at a
fiequency of 43.6 kHz, which is higher than the cutoff ftequency of 5
10 k-Hz in the frequency measurement, and was observed as .about 195.7
mA in effective value (RMS value) measurement.
[0155l Figs. 6(a), 6(b), 6(c), 6(d) and 6(e), respectively, illustrate
waveforms of the input voltage Vi, voltage Vgl at the gate terminal of
the switching device Q1, current sensor terminal voltage Vcs of the
15 integrated circuit IC1, voltage Vg2 at the gate terminal af the switching
device Q2 and cunent i flowing through the LED unit 24, when the
ballast 12 used is of the inverter type (with a secondary voltage of 280 V
and a secondary current of 0.225 A under no load). I
[Ql5q First, as illustrated in Fig. 6(a), in the waveform of the input
20 voltage Vm, the period tl is about 13.7 (ps), and a frequency of 73.0
kJ3i is observed.
[0157] Since this fiequency is higher than the cutoff fiequency that was
set to about 5 kHz, the gate terminal of the switching device 42 is
inputted with the voltage Vg2 at a high level (about 14 V DC) as
25 illustrated in Fig. 6(d), and thus the switching device 42 is always in the
on state.
[OB58] However, the resistors R3, R4, lR5 are connected in parallel
between the terminals T9, TG as mentioned above, and thus the current
i having flowed through the LED unit 24 hardly flows through the
PWM control unit 25, and flows directly fkom the cathode-side terminal
5 TK of the LED d t 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.
[0159] As a result, the current i does not flow through the resistors R3
to R5, and thus the current sensor tenninal voltage Vcs is stable at the
10 ground level (0 V) as illustrated in Fig. 6(c), the duty ratio of the driving
pulses becomes 100% as illustrated in Fig. 6@), the voltage Vgl at the
gate terminal of the switchhig device Q1 in the PWM control unit 25 is.
always at the high level (about 7.5 V DC), and the switching device Q1
is ,in the on state.
15 [0160] Hence, the PWM control unit 25 does not perform PWM control
of the current i flowing through the LED unit 24.
[0161] As illustrated in Fig. 6(e), the current i flowing through the LED
unit 24 attains a waveform in which the input voltage Vim is full-wave
rectified without PWM control by the PWM control unit 25, and was
20 observed as about 199.3 mA in effective value (RMS value)
measurement.
[0162] Furthermore, without the PWM control by the driving pulses of
the PWM control U& 25, the period t2 of the ripple voltage waveform
part superposed on the DC becomes about 6.9 (ps), and the frequency of
25 the current i flowing through the LED unit 24 was observed as about
145.4 kHz, which is twice as high as that of the input voltage Vin.
[Qd63] Therefore, it could be confirmed that the frequency 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 Vi through M-wave
rectification.
5 [0164] 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
10 lighting type.
[OX651 It was also confirmed that, when the ballast 12 is of the glow
starter or rapid start type, the current i flowing through the LED unit 24
is PWM controlled by the PWM control unit 25 driving pulses at a
fkequency of about 43.6 to 43.7 kHz, which is higher than the cutoff
15 frequency of 5 kHz, since the frequency of the input voltage Vim is
about 60 Hz.
101661 When the ballast 12 is of the invexter type, on the other hand, it
was confirmed that the fiequency of the input voltage Vin is about 73.0
kHz, which is higher than the cutoff fiequency of 5 kHz, and thus the
20 current i flowing throu&, the LED unit 24 is about 145.4 kHi and is not
PWM controlled by the PWM control unit 25 driving pulses.
[0167l The technical scope of the present invention is not limited to any
of the embodiments mentioned above but may be modified in various
ways within the scope set forth in the claims, and includes modified
25 examples of the embodiments which can be obtained by appropriately
combining technical means respectively disclosed in different
embodiments .
[0168] For example, a pair of input terminal parts is meant to include at
least one pair of input tenninal 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 suflicient for an external AC
to be inputted to at least two of the input terminal parts (two terminals
fiom one side or both sides).
(01691 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.
[0170] Furthermore, the predetermined frequency distinguishing the
fiequency of the AC inputted to the pair of input terminal parts is
preferably about 5 kHz (cutoff frequency) which can distinguish
between a utility power fiequency (50 Hz or 60 Hz) in the case of the
glow starter or rapid start type ballast, and a high frequency (about 20
kHz to 100 kHz) in the case of the inverter type, but may appropriately
be set so as to become a desirable fiequency within the fiequency range
of higher than 65 Hi but lower than 20 kHi by changing circuit
constants in the high-pass filter circuit.
[0171] Similarly, the frequency and duty ratio of pulses driven by the
PWM control unit may be set by appropriately configuring resistors
connected to pins, drive voltage and the like within the spec range of the
integrated circuit ICl 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.
I01721 In particular, circuit configurations and circuit constants in the
circuit diagrams used for reference may appropriately be selected within
a range included in the technical scope of the present invention as long
5 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.
[0173] Furthermore, as illustrated in Fig. 7(a), connecting a plurality of
resistors R20, R21, a zener diode D20 and a resistor R22 in series
10 between the high-voltage (HV)-side output terminal T7 and the
ground-side output terminal TS, 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
resistor R22, to the pin #7 of the integrated circuit ICl, . enables the
15 threshold voltage to be made variable in proportion to the magnitude of
the voltage inputted to the pair of input terminal parts.
[0174] For example, selecting 1 MI2 as the resistance value of the
resistor R20, 1 MX2 as the resistance value of the resistor R21, 5 1 V as
the Zener voltage of the zener diode D20, 3.65 WZ as the resistance
20 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
(HV)-side output terminal T7.
[0175] In this way, the voltage inputted to the pair of input terminal
25 parts, and the current flowing through the LED unit that is P\NM
controlled, increase and decrease in proportion to each other, and thus
the input impedance of the whole LED lamp in terns of the pair of input
terminal parts is made positive (the flowing current increases
proportionally as the input voltage becomes higher).
[0176] Hence, even when LED lamps 50, 60 according to the
5 embodiment are connected in series in a series rapid type ballast as
illustrated in Fig. 7@), the voltage inputted fiom the series rapid type
ballast is proportionally distributed according to their respective input
impedances, thus facilitating the flow of the same drive current through
both, and also enabling the LED lamps b the present embodiment to be
10 connected in series.
Industrial Applicability
[0177] As in the foregoing, the LED lamp and the illumination device
. including the LED lamp of the present invention can be applied for use
as an LED lamp, and an illumination device including the LED lamp,
15 capable of being .lit by driving pulses at a high frequency, 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
starter, rapid start or inverter lighting type.
Reference Signs List
20 [0178] 10 illumination device
11 plug
12 ballast
20, ,50,60 LED lamp
20a, 20b, 20c, 20d input terminal part
25 21 protection circuit unit
22 rectifier circuit unit
23 smoothing circuit unit
24 LEDunit
25 PWM control unit
26 bypass circuit unit
C1, C2, C9, C10, C11, C12, C20 capacitor
C3, C4, C5 electrolyhc capacitor
C6 first capacitor
C7 second capacitor
D2, D3, D4, D5, D6, D7 diode
D8 second diode
D9 &st diode
D 1, D 10, D2 0 Zener diode
29, Z10, Zl 1,212 input circuit unit
HV high voltage
F1 fuse
IC 1 integrated circuit
L1, L2, L3, L4 choke coil
L5 coil
L6 coil
QlyQ2 switching device
R22 resistor
R13 first resistor
R14 second resistor
SAl two-electrode discharge tube
SA2 varistor
TI, T2, T3, T4, T6, T8, T9 terminal
T5 ground-side output tenninal
T7 high-voltage (HV)-side output terminal
TA anode-side terminal
TK cathode-side terminal
TG GNDtenninal
Vin input voltage
VCS current sensor terminal voltage
Vgl voltage at the gate terminal of the switching device Q1
Vg2 voltage at the gate terminal of the switching device Q2
1 current flowing tbro- the LED unit
bsc oscillation period
We claim:
1. An LED lamp including a pair of input tenninal parts, a rectifier
circuit unit rectifying an AC inputted from the outside to the pair of
input terminal parts to a DC, and an LED unit emitting light by
5 electrification of the DC outputted from the rectifier circuit unit;
wherein a PWM control unit capable of performing PWM
control of a current to flow through the LED unit according to a duty
ratio is provided in a circuit between the rectifier circuit unit and the
LED unit; and
10 . 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 the 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.
15 2. An LED lamp according to claim 1, wherein the PWM control
unit performs the PWM control of the current flowing through the LED
unit by driving a pulse at a frequency higher than a predetermined
fiequency when a fi-equency of external AC inputted to the pair of
input terminal parts is lower than the predetermined fiequency, and does
20 not perform the PWM control of the current flowing through the LED
unit when the frequency of the external AC inputted to the pair of input
terriinal parts is higher than the predetermined frequency. I
3. An LED lamp according to claim 2, wherein a bypass circuit
unit is provided between a cathode-side terminal of the LED unit and a
25 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
fiom the cathode-side terminal of the LED ' unit to the ground-side
5 output terminal of the rectifier circuit unit when the AC inputted to the
pair of input terminal parts has a fiequency lower than the
predetermined fiequency, and allows a current to flow fiom the .
cathode-side terminal of the LED unit to the ground-side output
terminal of the rectifier circuit unit when the AC inputted fiom the pair
10 of input terminal parts has a frequency higher than the predetermined
. -
frequency.
4. An LED lamp according to claim 3, 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
15 . 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 tenninal of the rectifier circuit unit;
20 wherein the gate terminal is connected to any one of 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 tenninal driven so as to allow a current to flow from the drain
25 terminal to the source terminal when the AC inputted to the pair of input
terminal parts has a fiequency higher than the predetermined frequency,
and outputs a gate voltage to the gate terminal driven so as not to allow
a current to flow from the drain terrninal to the source terminal when the
AC inputted to the pair of input terminal parts has a fiequency lower
than the predetermined fiequency.
5. An LED lamp according to claim 4, wherein the high-pass filter
circuit includes:
a first capacitor;
a first resistor connected in series to the first capacitor so as to
have one terminal connected to one terminal of the first capacitor;
a first diode comeded in a forward direction from the other
terminal of the fxst resistor to the gate terminal;
a second capacitor connected between the source and gate
terminals;
a second resistor connected between the source and gate
tenninals;
a Zener diode connected a forward direction fiorn the source
terminal to the gate terminal; and
a second diode connected a forward direction fkom the source
terminal to the other terminal of the first resistor;
wherein the other terminal of the first capacitor is connected to
any one of the input tenninals of the rectifier circuit unit.
6. An LED lamp according to any one of claims 2 to 5, wherein the
predetermined frequency is a frequency higher than 65 Hz but lower
than 20 kHz.
7. An illumination device including the LED lamp according to
any one of claims 1 to 6.
Dated this 24m day of July, 20 14.