Title:
Integrated Circuit using Sequential Linear Technology for Driving LED Light

Background:
The present invention is directed to the integrated circuits. More particularly the system provide^ a system
and a method for driving a parallel switch device. Merely by the way of example, the invention, has been
applied to the power converter. But it would be recognized that the invention has a much broader range of
applicability. For example, the present invention can be applied to the driving circuit of Light Emitting
Diodes (LEDs),
The LEDs are made of compound such as the gallium (Ga), arsenic (As), and phosphorus (P) in which the
recombination of the electron and hole can radiate visible light. LED dnvers are widely used for consumer
electronics such as tube light and other portable devices. The LED drivers convert power supply from
alternate current (AC) to direct current (DC). Additionally, LED drivers can also convert electric power
from one voltage level to another voltage level.
FIG. 1 is simplified traditional flyback LED driver circuit with a power switch. The flyback LED driver
100 includes a transformer 110 including a primary winding 111, secondary winding 112 and ati auxiliary
winding 113. Additionally, the flyback LED driver 100 includes a controllerunit 120, LEDs 130, a power
switch 140 and an electrolytic capacitor 150. The power switch 140 is a field effect transistor such a highvoltage
power MOSFET and is used to control power delivered to the secondary side of the flyback LED
driver 100. For example , if the current of primary winding 111 is greater than a limiting level, the
controller unit 120 turns off the power switch 140 and shuts down the flyback LED driver 100.
As secondary side feedback eliminates the optocoupler and regulators from the LED driver. Its circuit
designing application is complex and difficult to achieve miniaturization. Furthermore, the flyback LED
driver 100 cannot be directly used for triac dimmer, it must be achieved by adding additional circuits.
As large electrolytic capacitor 150 and transformer 110 increases the cost and decreases the life time of the
flyback LED driver lOO.For example, the LEDs 150 used have longer lifetime but large electrolytic
capacitor 150 has shorter lifetime which leads to the limited lifetime of the flyback LED driver 100.
The conventional techniques of the flyback LED driver 100 may be costly and large in size. Hence it is
highly desirable to improve the techniques that are related to LED driver.
BRIEF SUMMARY OF THE INVENTION
The present invention is directed to the integrated circuits. More particularly the system provides a system
and a method for driving a parallel switch device. Merely by the way of example, the invention has been
applied to the power converter. But it would be recognized that the invention has a much broader range of
applicability. For example, the present invention can be applied to the driving circuit of Light Emitting
Diodes (LEDs).
According to one embodiment of the present invention, a system and method for driving a paraJlel switch
device is provided. The present invention is basically to solve the existing circuit's problem of high cost,
low efficiency and low power factor. The system includes a control module (1), a feedback module (2), a
rectifier bridge (3) and a load networkZ;,N>i>l.Positive terminal and negative terminal of the rectifier
bridge (3) are connected to the input terminal of the load network Zi and ground respectively. The rectifier
bridge (3) rectifies an AC full-wave supply. The entire load network Zjis connected across the rectifier
bridge (3) and the feedback module (2). The loads are connected in series andcommon networks of two
adjacent loads are connected to the control module (1). The feedback module (2) samples the output load
current flowing through the control module (1). The feedback module (2) adjusts the currerit flowing
through the control module (1) by adjusting the load size. Because few peripheral devices of the invention,
it can be directly integrated on top of the network load containing LED light board, LED effectively
reduces the size and manufacturing costs, improve efficiency and power factor circuit.
According to another embodiment of the present invention, a system and method for driving a parallel
switch device is provided. The present invention is basically to solve the existing circuit's problem of high
cost, low efficiency and low power factor. The system includes a control module (1 )including N-MOSFET
switchesSNj, N>i>l,a feedback module (2) includingcomparator Q,N>i>l,a reference voltage unitV-rHi,
N>i>l and a resistance R, a rectifier bridge (3) anda load networkZj, N>i>l.Positive terminal ani>l, a feedback module (2) includinga comparator Q,N>i>l, a reference voltage
unit VTHiN>i>l anda resistance R j ^ j > l , a rectifier bridge (3) anda load network^ N>i> 1 .Positive
terminal and negative terminal of the rectifier bridge (3) are connected to the input terminal of the load
network Z\ and ground respectively.The rectifier bridge (3) rectifies an AC full-wave supply. The load
network Z\ is connected across the rectifier bridge (3) and one of the terminals of the resistance RN. The
other terminal of the resistance Ris connected to the ground. The loads are connected in series andcommon
networksof two adjacent loads are connected to the respective drain terminal of the N-MOSFET switch
SNj.The source terminal of the N-MOSFET switch SNjis connected to the respective non-grounded end of
the resistance R;. The gate terminal of the N-MOSFET switch SNiis connected to the output terminals of
the respective comparator Q. First input terminal of the comparator Qis connected to the non-grounded
end of the respective resistance Ri+!. The feedback module (2) samples the output load current flowing
through the control module (1). The reference voltage unit VTHiis connected across other input terminal of
the respective comparator Q and the grounded end of the resistance Rj. The feedback module (2) adjusts
the current flowing through the control module (1) by adjusting the size of the load. Because few
peripheral devices of the invention, it can be directly integrated on top of the network load containing LED
light board, LED effectively reduces the size and manufacturing costs, improve efficiency and power
factor circuit.
Many benefits are achieved by way of the present invention over conventional techniques. For example,
some embodiments of the present invention provide a system and method to improve power factor,
increase the service life of the entire circuit. Some embodiments of the present invention significantly
simplify the circuit designing application.
Depending upon the embodiment, one and more of these benefits may be achieved. These benefits and
various additional objects, features and advantages of the present invention can be fully appreciated with
the reference to the detailed description and accompanying.
BRIERDESCRIPTION OFTHE DRAWING
FIG. 1 is a simplified diagram showing a conventional flyback LED driver with power switch.
FIG. 2 is a simplified diagram according to the first embodiment of the present invention.
FIG. 3 is a simplified diagram according to the second embodiment of the present invention.
FIG. 4 is a simplified diagram according to the third embodiment of the present invention.
FIG. 5is a simplified diagram showing an external AC input of the present invention after the rectifier
bridge and a current waveform diagram of a voltage period.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to the integrated circuits. More particularly the system provides a system
and method for driving a switch device. Merely by the way of example, the invention has been applied to
the power converter. But it would be recognized that the invention has a much broader range of
applicability.
For example, the present invention can be applied to the driving circuit of Light Emitting Diodes (LEDs).
FIG. 2 is the simplified system for the non-isolated LED driver circuit according to an embodiment of the
present invention. This diagram is merely an example, which should not unduly limit the scope of the
claims. One of ordinary skill in the art would recognize many variations, alternatives and modifications.
The System 200 includes the control module (1), the feedback module (2), the rectifier bridge (3) and a
load network Z(N>i>l.Although the above has been shown using a select group of components for the
system 200, there can be many alternatives, modifications and variations. For example, some of the
components may be expanded and/or combined. Other components may be inserted to those noted above.
For example, the system includes a comparator component.Depending upon the embodiment, the
arrangement of the components may be interchanged with others replaced.For example, the system 200 is
used to regulate the current through the load network Z,. Further details of the component are found
throughout the present specification ana; more particularly below.
As shown in FIG. 2, the rectifier bridge(3) has two input terminals connected to positive and negative
terminal of the AC voltage V^, two output terminals are connected to the input terminal of the load
network Zi and to the ground respectively. The rectifier bridge (3) rectifies an AC full-wave supply. The
load network Z, is connected across the rectifier bridge (3) and the feedback module (2). The loads are
connected in series and two adjacent load common networks are connected to the control module (1). For
Example, inside each load Zj, M number of LED strings are connected in parallel whereas each string is
having L number of LEDs connected in series, 100>M>1, L>1. The output terminal of the control
module (1) is connected to the feedback module (2). For example, the feedback module (2) samples the
output load current flowing through the control module (1). The feedback module (2) adjusts the signal
flowing through the control module (1) by adjusting the size of the load.
As discussed above and further emphasized here FIG. 2, is merely an example, which should not unduly
limit the scope of the claims. One of ordinary skill in the art would recognize many variation, alternatives,
and modification.
FIG. 3 is the simplified system for the non-isolated LED driver circuit according to an embodiment of the
present invention. This diagram is merely an example, which should not unduly limit the scope of the
claims. One of ordinary skill in the art Would recognize many variations, alternatives and modifications.
The system 300 includes N-MOSFET switches SNiN>i>l, comparator Q, N>i>l, the reference voltage unit
V-rai, N>i>l and the resistance R, the rectifier bridge (3) and the load network Zj, N>i>l. Although the
above has been shown using a select group of components for the system 300, there can be many
alternatives, modifications and variatioris. For example, some of the components may be expanded and/or
combined. Other components may be inserted to those noted above. For example, the system 300 includes
N-l comparator component Q.In another example, traditional band gap structure is used in the reference
voltage VTHi to generate N-l zero temperature reference voltage signals where VTHi>VTHj,N>i>j>l.
Depending upon the embodiment, the arrangement of the components may be interchanged with others
replaced. For example, the system 300 is used to regulate the N-MOSFET switches SNi. In another
example, the N-MOSFET switches SNi are used as a power switch for a LED driver. Further details of the
component are found throughout the present specification and more particularly below.
The positive terminal and negative terminal of the rectifier bridge (3)are connected to the input terminal of
the load network Zi and ground respectively. For example, the rectifier bridge (3) rectifies an AC fullwave
supply. The load network Z: is connected across the rectifier bridge (3) and one of the terminals of
the resistance R. The other terminal of resistance R is connected to the ground.For Example, inside each
load Zj, M number of LED strings are connected in parallel whereas each string is having L number of
LEDs connected in series, 100>M>l.The loads are connected in series and two adjacent load
common networks are connected to the drain terminal of the respective N-MOSFET switch SNi. In another
example, all high-voltage N-MOSFEET switches SNi are connected in parallel. The source terminal of NMOSFET
switches SNJ are connected to the non-grounded terminal of the resistance R. In another example,
the feedback voltage VFB is generated at the non-grounded terminal of the resistance R.The gate terminal
of the N-MOSFET switchesSN; is connected to the output terminal of the respective comparator Q. First
input terminal of all the comparators Ci are connected to the non-grounded end of the resistance R.The
reference voltage unit VTHi is connected across another input terminal of the respective comparator Q and
the grounded end of the resistance R. In another example, the output signal of comparator Q controls the
load size by adjusting the state of high voltage switches.
In one embodiment, if theoutput signals of the comparators Qcarry a logic high voltage, the N-MOSFET
switches S^are turned on. For example, for the already turned on N-MOSFET switches Sm, the feedback
signal VFB should be less than the reference voltageV™. In another example, for the already turned off NMOSFET
switches SNi, the feedback signal VFB should be more than reference voltageVTHi. In initial time,
the input voltage V^ is close to zero.In response, small load current ILflows from the positive terminal of
rectifier bridge(3) through the load network Zi and the resistance R to the negative terminal of the rectifier
bridge (3).Additionally, all the high-voltage parallel switches SJJJ are turned on. Hence, the load network
Z2ZN is short-circuited. The load current ILis flowing through the minimum load of the circuit.The load
current IL rises with the input voltage V^ which is increasing rapidly. The load current IL flowing through
the feedback module (2) generates a feedback voltage VFB which is increasing rapidly.As feedback voltage
VFB becomes greater than reference voltage VTHi, the first comparator Ci output signals reverse and the
first high-voltage switch SN] is turned off The current IL starts flowing through the load network Ziand Z2
and increase in the load current iLgets suppressed. As the input voltage V^T continues to raise, the load
current ILcontinues to rise andthe feedback voltage VFB continues to increase.When the feedback voltage
VFBbecomes greater than the second reference voltage V-rm, the second comparator C2 output signals
reverse and the second high-voltage parallel switch SN2 is turned off. The current IL starts flowing through
the load network Zj, Z2and Z^and increase in the load current IL gets suppressed again and so on. When the
input voltage V^ reaches in the vicinity of the highest point, the feedback voltage VFB becomes greater
than the N-l reference voltage VTHN-i-The N-l comparator CN.j output signals reverse and finally the N-l
high-voltage parallel switch SN-I is turned off. The load current IL starts flowing through the complete load
network ZIZN and remains constant to its peak value.
. _ * ac-peak ~ "f-atl
h ~ R
Where Va,..,^ represents the peak value of the AC mains voltage, which equals to its RMS value square;
Vf-aii represents the total forward voltage of the entire LED string Zi~ZN.
In another embodiment, if the comparator Cj output signals carry a logic low voltage, the N-MOSFET
switches SNiare turned off. For example, for the already turned off N-MOSFET switches SNi, the feedback
signal Vr e should be more than the reference voltage VxHi- hi another example, for the already turned on
N-MOSFET switches SNJ, the feedback signal VFB should be less than reference voltage V-r^In initial
time, the input voltage V^. is close to its highest value.In response, constant load current II flows from the
positive terminal of .rectifier bridge (3) through the Joad network Z/Zjv, the resistance R to the negative
terminal of the rectifier bridge (3).Additionally, all the high-voltage parallel switches SNi are turned off.
When the input voltage V^-begins to fall from the highest point, the load current IL decreases and the
feedback voltage VFB also decreases.When the feedback voltage VFB becomes smaller than the N-l
reference voltage VTHN.i, the N-1 comparator Cy.\ output signal reverses. N-1 high-voltage parallel switch
SN.i is turned on and the load network ZN is short-circuited. The load current IL starts flowing through the
load network Z\Za.\ and decrease in the load current IL gets suppressed.As decline of the input voltage
V^icontinues the load current IL continues to decrease and the feedback voltage VFB also keeps
decreasing,the feedback voltage VFBwiU become smaller than the reference voltage VTHN.2VTHN^VTH>M..so
on sequentially and the high-voltage parallel switches SN^SMJSN^-SO on are turned on sequentially. The
circuit load is decreased gradually. When the input voltage drops to near zero, the high-voltage parallel
switches SNISKN-I are all turned on. Therefore, the load current starts flowing again from the first load
network Z\.
As shown in the FIG. 3, the system 300 is used to regulate the high-voltage parallel N-MOSFET switches
SNi, which is used as a power switch for the LED driver according to an embodiment of the present
invention. The high-voltage parallel N-MOSFET switches SNiare turned on and off by the gate voltage in
order to control the power delivered to the load network Z(. The gate voltage of the high-voltage parallel
N-MOSFET switches SNi is determined by the signal generated by the comparator Q.
The comparator Cj receives the feedback voltage signal VF8 and the reference voltage signals V™ from
the voltage reference unit. The comparator C, determines the turn-on and turn-off time of the high-voltage
parallel N-MOSFET switches SNi based on the information associated with the feedback voltage V^. In
response, the comparator Cj adjusts thi>l, comparator QN>i>l, reference voltage unit
VTH» N>i>l and N number of resistance R„ a rectifier bridge (3) and a load network Z„ N>i>l.Although
the above has been shown using a select group of components for the system 400, there can be many
alternatives, modifications and variations. For example, some of the components may be expanded and/or
combined. Other components may be inserted to those noted above. For example, the system 400 includes
N-1 comparator component Q.In another example, traditional band gap structure is used in the reference
voltage VTHi to generate N-1 zero temperature reference voltage signals where VTHi>VTHj,N>i>j>l.
Depending upon the embodiment, the arrangement of the components may be interchanged with others
replaced. For example, the system 4Qo is used to regulate the N-MOSFET switches SNi. In another
example, the N-MOSFET switches SNi are used as a power switch for a LED driver. Further details of the
component are found throughout the present specification and more particularly below.
The positive terminal and negative terminal of the rectifier bridge (3) are connected to the input terminal of
the load network Zi and ground respectively. For example, the rectifier bridge (3) rectifies an AC fullwave
supply. The load network Z; is connected across the rectifier bridge (3) and one of the terminals of
the resistance RN. The other terminal of the entire resistance R; of the feedback module (2) is connected to
the ground.For Example, inside each load Z„ M number of LED strings are connected in parallel whereas
each string is having L number of LEDs connected in series, 100>MXN>1, L>l.The loads are connected in
series and two adjacent load common networks are connected to the drain terminal of the respective NMOSFET
switch Sx*. In another example, all N-l high-voltage parallel N-MOSFEET switches SN; are
connected in parallel. The source terminal of N-MOSFET switches S^is connected to the non-grounded
terminal of the resistance Rj. In another example, N number of the feedback voltage VFBi is generated at
the non-grounded terminal of the resistance Rj.The gate terminal of the N-MOSFET switchesS,vjis
connected to the output of the respective comparator C;. First input terminal of all the comparator Ci is
connected to the non-grounded end of the resistance Rj+j.The reference voltage unit VTHj is connected
across another input terminal of the respective comparator C, and the grounded end of the resistance Rj. In
another example, the output signal of comparator Q controls the load size by adjusting the state of high
voltage switches.
In one embodiment, if the comparator Ci output signals carry a logic high voltage, the N-MOSFET
switches S^are turned on. For example, for the already turned on N-MOSFET switches Sjui, the feedback
signal VFBiH.i,Vj:Bi>VpBj,N>i>j>l should be less than the reference voltage VTHi. In another example, for the
already turned off N-MOSFET switches SNJ, the feedback signal VFBi+i should be more than reference
voltage VTHi. In initial time, the input voltage V^ is close to zero.In response, a small load current IL flows
from the positive terminal of rectifier bridge (3) through the load network Z\, the resistance R, to the
negative terminal of the rectifier bridge (3).Additionally, all the high-voltage parallel switches Sui are
turned on and hence the load network Z2ZN is short-circuited. Therefore,the load current IL is flowing
through the minimum load of the circuit.The load current IL rises with the input voltage V^, which is
increasing rapidly. The load current IL flowing through the feedback module (2) generates a feedback
voltage VFB2 which is increasing rapidly.As feedback voltage VFB2 becomes greater than the reference
voltage VTH1 the first comparator Q output signal reverses and the first high-voltage switch SNI is turned
off. The current II starts flowing through the load network Z\ and Z2 and increase in the load current I[_ gets
suppressed. As the input voltage VJN continues to raise, the load current II continues to rise and the
feedback voltage VFB3 continues to increase.When the feedback voltage VFB3becomes greater than the
second reference voltage VTH2, the second comparator C2 output signalreverses and the second highvoltage
parallel switch SJQ is turned off. The current IL starts flowing through the load network Zb Z2and
Zx and increase in the load current IL get suppressed again and so on.When the input voltage Vw reaches in
the vicinity of the highest point, the feedback voltage VFBN becomes greater than the N-l reference voltage
VXHN-IJ the N-l comparator CN.J output signal reverses and finally the N-1 high-voltage parallel switch S^.
1 is turned off. The load current IL starts flowing through the complete load network Z[ZN and remains
constant at its peak value.
. _ * ac-peak ~ " f-all
RN
Where V ^ . , ^ represents the peak value of the AC mains voltage, which equals to its RMS value square;
Vf.aii represents the total forward voltage of the entire LED string Zi~Zjv>.
In another embodiment, if the comparator Q output signals carry a logic low voltage, the N-MOSFET
switches S^are turned off. For example, for the already turned off N-MOSFET switches SN» the feedback
signal VFBi+1 should be more than the reference voltage VTHi. In another example, for the already turned on
N-MOSFET switches Sj*;, the feedback signal VFBH-I should be less than reference voltage VxHj.In initial
time, the input voltage V^ is close to its highest value.In response, constant load current II flows from the
positive terminal of rectifier bridge(3) through the load network ZJZN, the resistance RN to the negative
terminal of the rectifier bridge (3).Additionally, all the high-voltage parallel switches Sni are turned off.
When the input voltage V^-begins to fall from the highest point, the load current IL decreases and the
feedback voltage VFBNalso decreases.When the feedback voltage VPBN becomes smaller than the N-l
reference voltage VTHN.I, the N-l comparator CN_I output signal reverses, N-l high-voltage parallel switch
S.v.i is turned on and the load network ZN is short-circuited. The load current IL starts flowing through the
load network Z;ZN-I and decrease in the load current IL gets suppressed. As decline of the input voltage V)N:
continues, the .load current IL continues to decrease, the feedback voltage VFBi+i also keeps decreasing. The
feedback voltage VFBl>1will become smaller than reference voltage VTHK.2VTHN.3VTHNJ,..so on sequentially,
the high-voltage parallel switches SN.2SN.JS>M..SO on are turned on sequentially. The circuit load is
decreased gradually. When the input voltage drops to near zero, the high-voltage parallel switches SNISNN-I
are all turned on. Therefore, the load current starts flowing again from the first load network Zj.
As shown in the FIG. 4, the system 400 is used to regulate the high-voltage parallel N-MOSFET switches
S\!j, which is used as a power switch for the LED driver according to an embodiment of the present
invention. The high-voltage parallel N-MOSFET switches SNiare turned on and off by the gate voltage in
order to control the power delivered to the load network Z;. The gate voltage of the high-voltage parallel
N-MOSFET switches SNi is determined by the signal generated by the comparator Q.
The comparator Ci receives the feedback voltage signal VFBi+1, the reference voltage signals VTHi from the
voltage reference unit. The comparator Q determines the turn-on and the turn-off time of the high-voltage
parallel N-MOSFET switches SNi based on the information associated with the feedback voltage VFBix,. In
response, the comparator Cj adjusts the value of its output signal. Accordingly, the output voltage of the
comparator Cj determines the gate voltage of the high-voltage parallel N-MOSFET switches S»j. For
example, the gate voltage of the high-v0ltage parallel N-MOSFET switches SNi controls the load current
ILand the power delivered to the load network Zj.
As discussed above and further emphasized here, FIG.4 is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications.
FIG. 5 is a simplified diagram showing an external AC input of die present invention after passing through a rectifier and a current waveform diagram of a voltage period. The switching device operates in a particular voltage range. For example, if the feedback voltage is higher or equal to the reference voltage of the corresponding switch then the switch turns off and the current will be restricted to mat point and if the feedback voltage is lower than the reference voltage of the corresponding switch then the switch turns on and the current will start following through that switch.

CLAIM
What is claimed is:
1. An non-isolated LED driver comprising:
a rectifier bridge whose positive terminal and negative terminals are connected to the input terminal of
the load network.and ground, respectively, for the rectification of an AC full-wave supply;
aload network connected across th^ rectifier bridge and the feedback module,and two adjacent load
common networks are connected to the control module, to serve as die luminance component and to
provide current information to the feedback module;
a feedback module whose input terminal is connected to the load network,to sample the output load
current flowing through the control module, the output terminal of the feedback module is connected
to the control module, to provide control signals for the switches of the control module to operate
properly;
a control module connected across the load network and the feedback module, to adjusts the current
flowing through the load network by adjusting the load size.
2. The non-isolated LED driver of claim 1, wherein the load network includes N loads connected in
series, each load includes M number of LED strings are connected in parallel whereas each string is
having L number of LEDs connected in series, 100>M*N>1, L>1.
3. The non-isolated LED driver of claim 1, wherein the feedback module includes N-1 comparator
component Q and a current sense resistor R. The positive input terminals of the comparators are
connected to the reference voltages generated by a voltage reference module, and negative terminals
are connected to the non-grounded terminal of the current sense resistor R, The other terminal of the
current sense resistor R is connected to the ground.
4. The non-isolated LED driver of claim 1, wherein the control module includes N-1 N-MOSFET
switches SNj, the source terminals of the N-MOSFET switches SNJ are connected to the non-grounded
end of the resistor R, the drain terminals of the NMOSFET switches SNJ are connected to the two
adjacent network of the load from the load network, each gate terminal of the N-MOSFET switch SNJ
is connected to the output terminal of the respective comparator Q.
5. The non-isolated LED driver of claim 1, wherein the load network provides the load current
information for the feedback module to process, and serves as luminance components.
6. The non-isolated LED driver of claim 1, wherein the feedback module controls the on/off operation of
the N-MOSFET from the control module according to the load current information, if the load current
is small than the reference value, the feedback module controls the control module to close a certain
N-MOSFET switch to reduce the load connected to the current path, otherwise, the feedback module
controls the control module to open a certain N-MOSFET switch to increase the load connected to the
current path, in order to achieve high power factor and high efficiency.
7. The non-isolated LED driver of claim 1, wherein the control module controls the connection and
disconnection of a certain load of the load network from rectified AC mains to the feedback module, in
order to change the load connected into the current path according to the rectified AC mains volage.
8. An non-isolated LED driver comprising:
a rectifier bridge whose positive terminal and negative terminals are connected to the input terminal of
the load network and ground, respectively, for the rectification of an AC full-wave supply;
aload network connected across the rectifier bridge and the feedback module,and two adjacent load
common networks are connected to the control module, to serve as the luminance component and to
provide current information to the feedback module;
a feedback module whose input terminal is connected to the load network, to sample the output load
current flowing through the control module, the output terminal of the feedback module is connected
to the control module, to provide control signals for the switches of the control module to operate
properly;
a control module connected across the load network and the feedback module, to adjusts the current
flowing through the load network by adjusting the load size.
9. The non-isolated LED driver of claim 8,. wherein the load network includes N loads connected in
• series, each load includes M number of LED strings are connected in parallel whereas each string is
having L number of LEDs connected in series, 100>M*N>1, L>1.
10. The non-isolated LED driver of claim 8, wherein the feedback module includes N-1 comparator
component Q and N current sense resistors Rj. The positive input terminals of the comparators are
connected to the reference voltages generated by a voltage reference module, and negative terminals
are connected to the non-grounded terminals of the current sense resistors R, The other terminals of
the current sense resistorsR; are connected to the ground.
11. The non-isolated LED driver of claim 1, wherein the control module includes (N-1) N-MOSFET
switches S^, the source terminals of the N-MOSFET switches SNJ are connected to the non-grounded
end of the resistorsRj, the drain terminals of the NMOSFET switches Sm are connected to the two
adjacent network of the load from the load network, each gate terminal of the N-MOSFET switch SNJ
is connected to the output terminal of the respective comparator Q.
12. The non-isoiated LED driver of claim I, wherein the load network provides the load current
information for the feedback module to process, and serves as luminance components.
13. The non-isolated LED driver of claim 1. wherein the feedback module controls the on/off operation of
the N-MOSFET from the control module according to the control module current information, if the
current flowing through one N-MOSFET switch of the control module is smaller than the reference
value, the feedback module controls the control module to close the N-MOSFET switch ahead of that
N-MOSFET switch to reduce the load connected to the current path, otherwise, the feedback module
. controls the control module to the N-MOSFET switch after that N-MOSFET switch to increase the
load connected to the current path, in order to achieve high power factor and high efficiency.
14. The non-isolated LED driver of claim 1, wherein the control module controis the connection and
disconnection of a certain load of the load network from rectified AC mains to the feedback module, in
order to change the load connected into the current path according to the rectified AC mains volage.