CN106604472B - LED drive circuit - Google Patents
LED drive circuit Download PDFInfo
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- CN106604472B CN106604472B CN201611270924.9A CN201611270924A CN106604472B CN 106604472 B CN106604472 B CN 106604472B CN 201611270924 A CN201611270924 A CN 201611270924A CN 106604472 B CN106604472 B CN 106604472B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
Abstract
The present invention discloses a kind of LED drive circuit, which is based on the design of UC3842 chip and realizes, has constant current output, output over-voltage protection, light modulation, the functions such as output current switching.Technical solution of the present invention has the characteristics that at low cost, versatile.
Description
Technical field
The present invention relates to field of LED drive technology, in particular to a kind of LED drive circuit.
Background technique
UC3842 is a kind of single-ended Switching Power Supply control integrated circuit of common current mode, is mainly used for reverse excitation circuit
In.The most commonly used is BOOST circuits for LED backlight in LCD TV, and for the needs of light modulation, the control integrated circuit of exploitation
All be it is dedicated, not only expensive, there are no versatility, the integrated circuit of each producer exploitation cannot be exchanged, once and IC
Damage, is difficult to buy this dedicated integrated circuit.Therefore, factory and duration have been highly desirable to set using universal integrated circuit
The backlight LED of meter production, which drives, to be occurred.In view of UC3842 is a kind of common in the market and very cheap Switching Power Supply control
Integrated circuit processed, and the performance of integrated circuits is stablized, and function is very complete, and peripheral circuit is suitble to flexibly collocation, therefore is set with this IC
A kind of LED driving is counted.
Summary of the invention
The main object of the present invention is to provide a kind of LED drive circuit, it is intended to improve the versatility of the LED drive circuit.
To achieve the above object, LED drive circuit proposed by the present invention includes UC3842 chip, first resistor, the second electricity
Resistance, 3rd resistor, the 4th resistance, the 5th resistance, the 6th resistance, the 7th resistance, the 8th resistance, the 9th resistance, the tenth resistance,
11 resistance, the 19th resistance, first capacitor, the second capacitor, the first transistor, second transistor, third transistor, the 4th crystalline substance
Body pipe, the 5th transistor, the 6th transistor, first diode, power output circuit and auxiliary power circuit；The UC3842 core
The reference voltage foot of piece, the first end of the 5th resistance, the first end of the tenth resistance and the eleventh resistor
The first end of one end interconnection, the second end of the 5th resistance, the oscillation foot of the UC3842 chip and the first capacitor is mutual
Even, the second end ground connection of the first capacitor；The cathode, described of the second end of the eleventh resistor, the first diode
The interconnection of the input terminal of the first end of second capacitor and the 6th transistor, the anode of the first diode, the UC3842
The input terminal interconnection of the compensation foot and the first transistor of chip, the second end ground connection of second capacitor；Described first is brilliant
The output end of body pipe is grounded, the controlled end of the first transistor, the second end of the first resistor and the second resistance
First end interconnection, the anode of the first end of the first resistor, the output end of the power output circuit and LED light bar to be driven
Interconnection, the second end ground connection of the second resistance；The output end of 6th transistor is grounded, the 6th transistor it is controlled
The input terminal interconnection at end, the second end of the tenth resistance and the 5th transistor, the output termination of the 5th transistor
The controlled end on ground, the 5th transistor is connect with the first end of the 9th resistance, the second end of the 9th resistance and institute
State the second end connection of the 6th resistance, connecting node for inputting dim signal, the first end of the 6th resistance with it is described
The controlled end of 4th transistor connects, the output end ground connection of the 4th transistor, the input terminal of the 4th transistor and institute
The second end connection of the 7th resistance is stated, the first end of the 7th resistance is connect with the controlled end of the third transistor, described
The output end of third transistor is connect with the first end of the 8th resistance, the input terminal of the third transistor, the auxiliary
The interconnection of the supply pin of the output end of power circuit and the UC3842 chip；The second end of 8th resistance and second crystalline substance
The controlled end of body pipe connects, and the input terminal of the second transistor is connect with the cathode of LED light bar to be driven；Second transistor
The second end of output end, the first end of 3rd resistor and the 4th resistance interconnects, the second end ground connection of the 3rd resistor, and described the
The first end of four resistance is connect with the second end of the 19th resistance, the first end of the 19th resistance and the UC3842
The Voltage Feedback foot of chip connects；The current sampling foot of the feedback end of the power output circuit and the UC3842 chip connects
It connects, the controlled end of the power output circuit is connect with the output pin of the UC3842 chip.
Preferably, the auxiliary power circuit includes twelfth resistor, the 7th transistor and zener diode, and the described tenth
The input terminal of the first end of two resistance and the 7th transistor is all connected with the first power supply, the second end of the twelfth resistor,
The cathode interconnection of the controlled end and the zener diode of 7th transistor, the plus earth of the zener diode, institute
The output end for stating the 7th transistor is the output end of the auxiliary power circuit.
Preferably, the power output circuit include boosting unit, thirteenth resistor, the 14th resistance, the 15th resistance,
The input terminal of 16th resistance, third capacitor and the 8th transistor, the boosting unit connects input power, the boosting unit
The first output end be the power output circuit output end, the second output terminal of the boosting unit and the 8th crystal
The input terminal of pipe connects, and the controlled end of the 8th transistor is connect with the second end of the 16th resistance, and the described 16th
The first end of resistance is the controlled end of the power output circuit, the output end of the 8th transistor, the thirteenth resistor
Second end and the 14th resistance first end interconnection, the 14th resistance second end ground connection, it is described 13rd electricity
The first end of the first end of resistance, the first end of the third capacitor and the 15th resistance interconnects, and connecting node is described
The feedback end of power output circuit, the third capacitor second end ground connection, the second end of the 15th resistance with it is described
The reference voltage foot of UC3842 chip connects.
Preferably, the LED drive circuit further includes the second diode, the anode of second diode, the described tenth
The second end of one resistance and the interconnection of the first end of second capacitor, the cathode of two diode, the eleventh resistor
The interconnection of the reference voltage foot of first end and the UC3842 chip.
Preferably, the LED drive circuit further includes the 17th resistance, the 18th resistance and the 9th transistor, and described
The second end of 17 resistance is for receiving switch-over control signal, first end and the 9th transistor of the 17th resistance
Controlled end connection, the output end ground connection of the 9th transistor, the input terminal and the 18th resistance of the 9th transistor
Second end connection, the of the first end of the 18th resistance, the second end of the 19th resistance and the 4th resistance
One end interconnection.
Preferably, the LED drive circuit further includes the 20th resistance, the first end of the 20th resistance with it is described
The reference voltage foot of UC3842 chip connects, the second end of the 20th resistance, the first end of the 19th resistance and institute
State the Voltage Feedback foot interconnection of UC3842 chip.
Preferably, the LED drive circuit further includes the 21st resistance, the first end of the 21st resistance, institute
The second end of the 8th resistance and the controlled end interconnection of the second transistor are stated, it is the second end of the 21st resistance, described
The second end of the output end of second transistor, the first end of the 3rd resistor and the 4th resistance interconnects.
Preferably, the LED drive circuit further includes the 22nd resistance, the 4th capacitor and the 5th capacitor, and the described 5th
The first end of capacitor is connect with the compensation foot of the UC3842 chip, the second end of the 5th capacitor, the 4th capacitor
First end and the interconnection of the first end of the 22nd resistance, the second end of the 4th capacitor, the 22nd resistance
The interconnection of the Voltage Feedback foot of second end and the UC3842 chip.
Preferably, the UC3842 chip can also derive from cake core, improvement cake core or homologous series chip with it and replace
Generation.
This driving LED drive circuit on the basis of UC3842 chip by increasing the electricity such as resistance, capacitor and transistor
Sub- component realizes the constant current output of LED drive circuit, output over-voltage protection, light modulation, the functions such as output current switching, energy
Enough meet the power demands of most of LED light bars.Due to this LED drive circuit be based on UC3842 chip design realize, and
UC3842 chip is a kind of common in the market and very cheap Switching Power Supply control integrated circuit, and the performance of integrated circuits
Stablize, function is very complete, and peripheral circuit is suitble to flexible.Therefore, corresponding, this LED drive circuit at least has versatile, cost
Low feature.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
The structure shown according to these attached drawings obtains other attached drawings.
Fig. 1 is the electrical block diagram of one embodiment of LED drive circuit of the present invention.
Drawing reference numeral explanation:
| Label | Title | Label | Title | Label | Title |
| 10 | Auxiliary power circuit | R1 | First resistor | R16 | 16th resistance |
| 20 | Power output circuit | R2 | Second resistance | R17 | 17th resistance |
| 21 | Boosting unit | R3 | 3rd resistor | R18 | 18th resistance |
| Q1 | The first transistor | R4 | 4th resistance | R19 | 19th resistance |
| Q2 | Second transistor | R5 | 5th resistance | R20 | 20th resistance |
| Q3 | Third transistor | R6 | 6th resistance | R21 | 21st resistance |
| Q4 | 4th transistor | R7 | 7th resistance | R22 | 22nd resistance |
| Q5 | 5th transistor | R8 | 8th resistance | C1 | First capacitor |
| Q6 | 6th transistor | R9 | 9th resistance | C2 | Second capacitor |
| Q7 | 7th transistor | R10 | Tenth resistance | C3 | Third capacitor |
| Q8 | 8th transistor | R11 | Eleventh resistor | C4 | 4th capacitor |
| Q9 | 9th transistor | R12 | Twelfth resistor | C5 | 5th capacitor |
| DZ | Zener diode | R13 | Thirteenth resistor | U1 | UC3842 chip |
| D1 | First diode | R14 | 14th resistance | ||
| D2 | Second diode | R15 | 15th resistance |
The embodiments will be further described with reference to the accompanying drawings for the realization, the function and the advantages of the object of the present invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiment is only a part of the embodiments of the present invention, instead of all the embodiments.Base
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts it is all its
His embodiment, shall fall within the protection scope of the present invention.
It is to be appreciated that if the directional instruction (such as up, down, left, right, before and after ...) of institute in the embodiment of the present invention,
It is only used for explaining in relative positional relationship, the motion conditions etc. under a certain particular pose (as shown in the picture) between each component, such as
The fruit particular pose changes, then directionality instruction also correspondingly changes correspondingly.
In addition, the description for being related to " first ", " second " etc. in the present invention is used for description purposes only, and should not be understood as referring to
Show or imply its relative importance or implicitly indicates the quantity of indicated technical characteristic." first ", " are defined as a result,
Two " feature can explicitly or implicitly include at least one of the features.In addition, the technical solution between each embodiment can
It to be combined with each other, but must be based on can be realized by those of ordinary skill in the art, when the combination of technical solution occurs
Conflicting or cannot achieve when, will be understood that the combination of this technical solution is not present, also not the present invention claims protection model
Within enclosing.
The present invention proposes a kind of LED drive circuit, can be realized constant current output, output over-voltage protection, and light modulation exports electric current
The functions such as switching.It is realized further, since the LED drive circuit is based on UC3842 chip U1 design, and UC3842 chip U1 is one
Kind in the market common and very cheap Switching Power Supply controls integrated circuit, and the performance of integrated circuits is stablized, and function is very complete,
Peripheral circuit is suitble to flexible.Therefore, corresponding, this LED drive circuit at least has the characteristics that versatile, at low cost.Wherein,
UC3842 chip U1 can also with its derive from cake core (for example, UC3843, UC3844, UC3845), improve cake core (for example,
UC3842A, UC3843A, UC3845A) or homologous series chip (for example, UC1842, UC2842) substitution.Specifically, it please refers to
Following the description.
In one embodiment, above-mentioned LED drive circuit includes UC3842 chip U1, first resistor R1, second resistance R2,
Three resistance R3, the 4th resistance R4, the 5th resistance R5, the 6th resistance R6, the 7th resistance R7, the 8th resistance R8, the 9th resistance R9,
Ten resistance R10, eleventh resistor R11, the 19th resistance R19, first capacitor C1, the second capacitor C2, the first transistor Q1, second
Transistor Q2, third transistor Q3, the 4th transistor Q4, the 5th transistor Q5, the 6th transistor Q6, power output circuit 20 and
Auxiliary power circuit 10.
Wherein, the reference voltage foot VREF of UC3842 chip U1, the first end of the 5th resistance R5, the tenth resistance R10
The interconnection of the first end of one end and eleventh resistor R11, the oscillation foot RT/CT of the second end of the 5th resistance R5, UC3842 chip U1
And the first end interconnection of first capacitor C1, the second end ground connection of first capacitor C1；The second end of eleventh resistor R11, UC3842
Chip U1's compensates the defeated of foot COMP, the first end of the second capacitor C2, the input terminal of the 6th transistor Q6 and the first transistor Q1
Enter end interconnection, the second end ground connection of the second capacitor C2；The output end of the first transistor Q1 is grounded, and the first transistor Q1's is controlled
The first end interconnection at end, the second end of first resistor R1 and second resistance R2, the first end of first resistor R1, power output circuit
The anode interconnection of 20 output end and LED light bar LB to be driven, the second end ground connection of second resistance R2；6th transistor Q6's is defeated
Outlet ground connection, the input terminal interconnection of the controlled end of the 6th transistor Q6, the second end of the tenth resistance R10 and the 5th transistor Q5,
The output end of 5th transistor Q5 is grounded, and the controlled end of the 5th transistor Q5 is connect with the first end of the 9th resistance R9, the 9th electricity
The second end of resistance R9 is connect with the second end of the 6th resistance R6, and connecting node is for inputting dim signal DIM, the 6th resistance R6
First end connect with the controlled end of the 4th transistor Q4, the output end of the 4th transistor Q4 ground connection, the 4th transistor Q4's is defeated
Entering end to connect with the second end of the 7th resistance R7, the first end of the 7th resistance R7 is connect with the controlled end of third transistor Q3, the
The output end of three transistor Q3 is connect with the first end of the 8th resistance R8, input terminal, the auxiliary power circuit of third transistor Q3
The supply pin VCC interconnection of 10 output end and UC3842 chip U1；The second end of 8th resistance R8 and second transistor Q2 by
End connection is controlled, the input terminal of second transistor Q2 is connect with the cathode of LED light bar LB to be driven；The output of second transistor Q2
The second end interconnection at end, the first end of 3rd resistor R3 and the 4th resistance R4, the second end ground connection of 3rd resistor R3, the 4th resistance
The first end of R4 is connect with the second end of the 19th resistance R19, the first end of the 19th resistance R19 and the electricity of UC3842 chip U1
Pressure feedback foot VFB connection；The feedback end of power output circuit 20 is connect with the current sampling foot Isense of UC3842 chip U1, electricity
The controlled end of source follower circuit 20 is connect with the output pin OUT of UC3842 chip U1.
Here, 3rd resistor R3 and the 4th resistance R4, the 19th resistance R19 form constant current feed circuit (figure does not mark).
Specifically, the electric current for flowing through LED light bar LB forms sampled voltage at the both ends 3rd resistor R3, and passes through the 4th resistance R4, and the tenth
Nine resistance R19 feed back to the Voltage Feedback foot VFB of UC3842 chip U1.UC3842 chip U1 can be according to falling in its Voltage Feedback foot
The voltage swing of VFB accordingly controls the electric current for flowing through LED light bar LB, permanent with the size of current for flowing through LED light bar LB
It is fixed.
First resistor R1, second resistance R2 and the first transistor Q1 form output overvoltage protection circuit (figure does not mark).Tool
Body, when the output voltage of power output circuit 20 is greater than preset threshold voltage, fall in the first end of second resistance R2
Voltage is greater than the cut-in voltage of the first transistor Q1, and the first transistor Q1 conducting falls in the compensation foot COMP of UC3842 chip U1
Voltage be pulled low, the output pin OUT of UC3842 chip U1 stops output, achievees the purpose that overvoltage protection.
6th resistance R6, the 7th resistance R7, the 8th resistance R8, the 9th resistance R9, the tenth resistance R10, second transistor Q2,
Third transistor Q3, the 4th transistor Q4, the 5th transistor Q5 and the 6th transistor Q6 composition light adjusting circuit (figure does not mark).Tool
Body, when dim signal DIM is high level, the 4th transistor Q4 conducting, the voltage of the controlled end of third transistor Q3 is drawn
Low, the voltage of the controlled end of second transistor Q2 is elevated, and second transistor Q2 conducting, LED drive circuit drives LED light bar LB
Work.At the same time, the 5th transistor Q5 is connected, and the voltage of the 6th transistor Q6 controlled end is pulled low, and the 6th transistor Q6 is cut
Only, therefore the voltage for falling in the compensation foot COMP of UC3842 chip U1 will not be pulled low, LED drive circuit keeps power supply output.
When dim signal DIM is low level, the 4th transistor Q4 cut-off, third transistor Q3 cut-off, second transistor Q2 cut-off,
The supply access of LED light bar LB is cut off.At the same time, the 5th transistor Q5 ends, the 6th transistor Q6 conducting, UC3842 core
The voltage of the compensation foot COMP of piece U1 is pulled low, and the output pin OUT of UC3842 chip U1 stops output, LED drive circuit cutting
Power supply output.Adjust the duty ratio of dim signal DIM, so that it may achieve the purpose that light modulation.
Preferably, above-mentioned auxiliary power circuit 10 includes twelfth resistor R12, the 7th transistor Q7 and zener diode
The input terminal of DZ, the first end of twelfth resistor R12 and the 7th transistor Q7 are all connected with the first power supply VCC, twelfth resistor R12
Second end, the 7th transistor Q7 controlled end and zener diode DZ cathode interconnection, the plus earth of zener diode DZ,
The output end of 7th transistor Q7 is the output end of auxiliary power circuit 10.
It is appreciated that in 10 course of work of auxiliary power circuit, since the voltage for being added in the both ends zener diode DZ is permanent
The fixed and pressure drop between the controlled end and output end of the 7th transistor Q7 is fixed, therefore, 10 output end pair of auxiliary power circuit
Ground voltage is also fixed.So, it is ensured that UC3842 chip U1 obtains stable supply voltage, electric relative to directlying adopt first
Source VCC provides the scheme of supply voltage for UC3842 chip U1, enhances the reliability of LED drive circuit.
Preferably, above-mentioned power output circuit 20 include boosting unit 21, thirteenth resistor R13, the 14th resistance R14,
The input terminal connection of 15th resistance R15, the 16th resistance R16, third capacitor C3 and the 8th transistor Q8, boosting unit 21 are defeated
Enter power supply VI, the first output end of boosting unit 21 is the output end of power output circuit 20, the second output of boosting unit 21
End is connect with the input terminal of the 8th transistor Q8, and the controlled end of the 8th transistor Q8 is connect with the second end of the 16th resistance R16,
The first end of 16th resistance R16 is the controlled end of power output circuit 20, the output end of the 8th transistor Q8, thirteenth resistor
The second end of R13 and the interconnection of the first end of the 14th resistance R14, the second end ground connection of the 14th resistance R14, thirteenth resistor
The first end of the first end of R13, the first end of third capacitor C3 and the 15th resistance R15 interconnects, and connecting node is that power supply is defeated
The feedback end of circuit 20 out, the second end ground connection of third capacitor C3, the second end of the 15th resistance R15 is with UC3842 chip U1's
The VREF connection of reference voltage foot.
Here, boosting unit 21 can use BOOST Boost topology framework, other topological structures can also be used.
It is noted that the compensation foot COMP of UC3842 chip U1 needs simultaneously in the LED drive circuit course of work
Receive the feedback signal of overvoltage crowbar and the feedback signal of light adjusting circuit.The feedback of overvoltage crowbar output in order to prevent
The feedback signal that signal is exported with light adjusting circuit interferes with each other, and in the present embodiment, is also additionally arranged first diode D1, specifically,
The input terminal interconnection of the anode, the compensation foot COMP and the first transistor Q1 of UC3842 chip U1 of first diode D1, the one or two
The cathode of pole pipe D1, the input terminal of the 6th transistor Q6, the first end of the second end of eleventh resistor R11 and the second capacitor C2 are mutual
Even.
In addition, the second capacitor C2 is charged by eleventh resistor R11 when above-mentioned UC3842 chip U1 is powered on, and
When UC3842 chip U1 power down, the second capacitor C2 does not have discharge loop.Based on this, in the present embodiment, it is also additionally arranged the two or two pole
Pipe D2, specifically, the first end of the anode of the second diode D2, the second end of eleventh resistor R11 and the second capacitor C2 are interconnected,
The reference voltage foot VREF of the cathode of second diode D2, the first end of eleventh resistor R11 and UC3842 chip U1 is interconnected.
Further, in this embodiment LED drive circuit further includes the 17th resistance R17, the 18th resistance R18 and
Nine transistor Q9, to realize the function of output current switching.Wherein, the second end of the 17th resistance R17 is for receiving switching control
Signal 2D/3D processed, the first end of the 17th resistance R17 are connect with the controlled end of the 9th transistor Q9, and the 9th transistor Q9's is defeated
Outlet ground connection, the input terminal of the 9th transistor Q9 are connect with the second end of the 18th resistance R18, and the first of the 18th resistance R18
The first end interconnection at end, the second end of the 19th resistance R19 and the 4th resistance R4.
Specifically, when the switch-over control signal 2D/3D of input is low level, the 9th transistor Q9 cut-off is fallen in
The voltage of the Voltage Feedback foot VFB of UC3842 chip U1 is the voltage for falling in 3rd resistor R3 first end；When the switching control of input
When signal 2D/3D processed is high level, the 9th transistor Q9 conducting falls in the voltage of the Voltage Feedback foot VFB of UC3842 chip U1
To fall in voltage of the voltage of 3rd resistor R3 first end after the 4th resistance R4 and the 8th resistance R8 partial pressure.That is, working as
When the switch-over control signal 2D/3D of input is low level, it is desirable that fall in the voltage of the first end of 3rd resistor R3 and fall in
The voltage swing of the Voltage Feedback foot VFB of UC3842 chip U1 is equal, when the switch-over control signal 2D/3D of input is high level
When, it is desirable that the voltage for falling in the first end of 3rd resistor R3 is higher than the voltage for falling in the Voltage Feedback foot VFB of UC3842 chip U1.
In this way, the electric current for flowing through LED light bar LB is relatively small when the switch-over control signal 2D/3D of input is low level；When input
When switch-over control signal 2D/3D is high level, the electric current for flowing through LED light bar LB is relatively large, i.e. switch-over control signal 2D/3D can
So that LED drive circuit switching exports different electric currents.
Further, in this embodiment LED drive circuit further includes the 20th electricity for reducing 3rd resistor R3 power consumption
Hinder R20.Specifically, the first end of the 20th resistance R20 is connect with the reference voltage foot VREF of UC3842 chip U1, the 20th electricity
Hinder the Voltage Feedback foot VFB interconnection of the second end of R20, the first end of the 19th resistance R19 and UC3842 chip U1.
Further, in this embodiment LED drive circuit further includes the 21st electricity for protecting second transistor Q2
Hinder R21.Specifically, the first end, the second end of the 8th resistance R8 and the controlled end of second transistor Q2 of the 21st resistance R21
Interconnection, the second end of the 21st resistance R21, the output end of second transistor Q2, the first end of 3rd resistor R3 and the 4th electricity
Hinder the second end interconnection of R4.
Further, in this embodiment LED drive circuit further includes for anti-to the voltage for being input to UC3842 chip U1
The corrected 22nd resistance R22 of the feedback signal of feed pin VFB, the 4th capacitor C4 and the 5th capacitor C5.Specifically, the 5th
The first end of capacitor C5 is connect with the compensation foot COMP of UC3842 chip U1, the second end of the 5th capacitor C5, the 4th capacitor C4
First end and the interconnection of the first end of the 22nd resistance R22, the second of the second end of the 4th capacitor C4, the 22nd resistance R22
The Voltage Feedback foot VFB of end and UC3842 chip U1 interconnection.
Hereinafter, illustrating the working principle of LED drive circuit of the present invention in conjunction with Fig. 1:
This LED drive circuit controls the 8th transistor Q8 work by the output pin OUT of UC3842 chip U1, to realize
Constant current output.In the LED drive circuit course of work:
If the output voltage of power output circuit 20 is greater than preset threshold voltage, the first end of second resistance R2 is fallen in
Voltage be greater than the first transistor Q1 cut-in voltage, the first transistor Q1 conducting, fall in the compensation foot of UC3842 chip U1
The voltage of COMP is pulled low, and the output pin OUT of UC3842 chip U1 stops output, achievees the purpose that overvoltage protection.
If the dim signal DIM of input is high level, the 4th transistor Q4 is connected, the controlled end of third transistor Q3
Voltage is pulled low, and the voltage of the controlled end of second transistor Q2 is elevated, second transistor Q2 conducting, LED drive circuit driving
LED light bar LB work.At the same time, the 5th transistor Q5 is connected, and the voltage of the 6th transistor Q6 controlled end is pulled low, and the 6th is brilliant
Therefore body pipe Q6 cut-off, the voltage for falling in the compensation foot COMP of UC3842 chip U1 will not be pulled low, LED drive circuit keeps electricity
Source output.If the dim signal DIM of input is low level, the 4th transistor Q4 cut-off, third transistor Q3 cut-off, second is brilliant
The supply access of body pipe Q2 cut-off, LED light bar LB is cut off.At the same time, the 5th transistor Q5 ends, and the 6th transistor Q6 is led
Logical, the voltage of the compensation foot COMP of UC3842 chip U1 is pulled low, and the output pin OUT of UC3842 chip U1 stops output, and LED drives
Dynamic circuitry cuts power supply output.Adjust the duty ratio of dim signal DIM, so that it may achieve the purpose that light modulation.
If the switch-over control signal 2D/3D of input is low level, fall in the Voltage Feedback foot VFB's of UC3842 chip U1
Voltage is the voltage for falling in 3rd resistor R3 first end；If the switch-over control signal 2D/3D of input is high level, fall in
The voltage of the Voltage Feedback foot VFB of UC3842 chip U1 is to fall in the voltage of 3rd resistor R3 first end through the 4th resistance R4 and
Voltage after 18 resistance R18 partial pressure.Adjust the switch-over control signal 2D/3D of input, so that it may so that LED drive circuit switching is defeated
Different electric current out.
The above description is only a preferred embodiment of the present invention, is not intended to limit the scope of the invention, all at this
Under the inventive concept of invention, using equivalent structure transformation made by description of the invention and accompanying drawing content, or directly/use indirectly
It is included in other related technical areas in scope of patent protection of the invention.
Claims (8)
1. a kind of LED drive circuit, which is characterized in that including UC3842 chip, first resistor, second resistance, 3rd resistor,
Four resistance, the 5th resistance, the 6th resistance, the 7th resistance, the 8th resistance, the 9th resistance, the tenth resistance, eleventh resistor, the tenth
Nine resistance, first capacitor, the second capacitor, the first transistor, second transistor, third transistor, the 4th transistor, the 5th crystal
Pipe, the 6th transistor, first diode, power output circuit and auxiliary power circuit；
The reference voltage foot of the UC3842 chip, the first end of the 5th resistance, the first end of the tenth resistance and institute
State the first end interconnection of eleventh resistor, the second end of the 5th resistance, the oscillation foot of the UC3842 chip and described the
The first end of one capacitor interconnects, the second end ground connection of the first capacitor；The second end of the eleventh resistor, the described 1st
The input terminal of the cathode of pole pipe, the first end of second capacitor and the 6th transistor interconnects, the first diode
The input terminal interconnection of anode, the compensation foot of the UC3842 chip and the first transistor, the second end of second capacitor
Ground connection；The output end of the first transistor is grounded, the controlled end of the first transistor, the first resistor second end and
The first end of the second resistance interconnects, the first end of the first resistor, the output end of the power output circuit and wait drive
The anode interconnection of dynamic LED light bar, the second end ground connection of the second resistance；The output end of 6th transistor is grounded, described
The input terminal of the controlled end of 6th transistor, the second end of the tenth resistance and the 5th transistor interconnects, and the described 5th
The output end of transistor is grounded, and the controlled end of the 5th transistor is connect with the first end of the 9th resistance, and the described 9th
The second end of resistance is connect with the second end of the 6th resistance, and connecting node is for inputting dim signal, the 6th electricity
The first end of resistance is connect with the controlled end of the 4th transistor, and the output end ground connection of the 4th transistor, the described 4th is brilliant
The input terminal of body pipe is connect with the second end of the 7th resistance, first end and the third transistor of the 7th resistance
Controlled end connection, the output end of the third transistor are connect with the first end of the 8th resistance, the third transistor
The supply pin of input terminal, the output end of the auxiliary power circuit and the UC3842 chip interconnects；The of 8th resistance
Two ends are connect with the controlled end of the second transistor, the cathode of the input terminal of the second transistor and LED light bar to be driven
Connection；The second end of the output end of second transistor, the first end of 3rd resistor and the 4th resistance interconnects, the 3rd resistor
Second end ground connection, the first end of the 4th resistance are connect with the second end of the 19th resistance, the 19th resistance
First end is connect with the Voltage Feedback foot of the UC3842 chip；The feedback end of the power output circuit and the UC3842 core
The current sampling foot of piece connects, and the controlled end of the power output circuit is connect with the output pin of the UC3842 chip.
2. LED drive circuit as described in claim 1, which is characterized in that the auxiliary power circuit include twelfth resistor,
The input terminal of 7th transistor and zener diode, the first end of the twelfth resistor and the 7th transistor is all connected with
The cathode of one power supply, the second end of the twelfth resistor, the controlled end of the 7th transistor and the zener diode is mutual
Even, the plus earth of the zener diode, the output end of the 7th transistor are the output end of the auxiliary power circuit.
3. LED drive circuit as described in claim 1, which is characterized in that the power output circuit includes boosting unit,
13 resistance, the 14th resistance, the 15th resistance, the 16th resistance, third capacitor and the 8th transistor, the boosting unit
Input terminal connects input power, and the first output end of the boosting unit is the output end of the power output circuit, the liter
The second output terminal of pressure unit is connect with the input terminal of the 8th transistor, the controlled end of the 8th transistor and described the
The second ends of 16 resistance connects, and the first end of the 16th resistance is the controlled end of the power output circuit, and described the
The first end of the output end of eight transistors, the second end of the thirteenth resistor and the 14th resistance interconnects, and the described tenth
The second end of four resistance is grounded, the first end of the thirteenth resistor, the first end of the third capacitor and the 15th electricity
The first end of resistance interconnects, and connecting node is the feedback end of the power output circuit, and the second end of the third capacitor is grounded,
The second end of 15th resistance is connect with the reference voltage foot of the UC3842 chip.
4. LED drive circuit as described in claim 1, which is characterized in that the LED drive circuit further includes the two or two pole
Pipe, the first end interconnection of the anode of second diode, the second end of the eleventh resistor and second capacitor are described
The reference voltage foot of the cathode of two diodes, the first end of the eleventh resistor and the UC3842 chip interconnects.
5. LED drive circuit as described in claim 1, which is characterized in that the LED drive circuit further includes the 17th electricity
Resistance, the 18th resistance and the 9th transistor, the second end of the 17th resistance is for receiving switch-over control signal, and the described tenth
The first end of seven resistance is connect with the controlled end of the 9th transistor, the output end of the 9th transistor ground connection, and described the
The input terminal of nine transistors is connect with the second end of the 18th resistance, the first end of the 18th resistance, the described tenth
The second end of nine resistance and the interconnection of the first end of the 4th resistance.
6. LED drive circuit as claimed in claim 5, which is characterized in that the LED drive circuit further includes the 20th electricity
Resistance, the first end of the 20th resistance connect with the reference voltage foot of the UC3842 chip, and the of the 20th resistance
The Voltage Feedback foot at two ends, the first end of the 19th resistance and the UC3842 chip interconnects.
7. LED drive circuit as described in claim 1, which is characterized in that the LED drive circuit further includes the 21st electricity
Resistance, the controlled end interconnection of the first end of the 21st resistance, the second end of the 8th resistance and the second transistor,
Second end, the output end of the second transistor, the first end of the 3rd resistor and described of 21st resistance
The second end of four resistance interconnects.
8. LED drive circuit as described in claim 1, which is characterized in that the LED drive circuit further includes the 22nd electricity
Resistance, the 4th capacitor and the 5th capacitor, the first end of the 5th capacitor are connect with the compensation foot of the UC3842 chip, and described the
The first end of the second end of five capacitors, the first end of the 4th capacitor and the 22nd resistance interconnects, the 4th electricity
The Voltage Feedback foot of the second end of appearance, the second end of the 22nd resistance and the UC3842 chip interconnects.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201611270924.9A CN106604472B (en) | 2016-12-30 | 2016-12-30 | LED drive circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201611270924.9A CN106604472B (en) | 2016-12-30 | 2016-12-30 | LED drive circuit |
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| CN106604472A CN106604472A (en) | 2017-04-26 |
| CN106604472B true CN106604472B (en) | 2019-05-31 |
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| CN201611270924.9A Active CN106604472B (en) | 2016-12-30 | 2016-12-30 | LED drive circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110662323B (en) | 2018-06-28 | 2022-04-12 | 朗德万斯公司 | Driver, method for controlling driver, and lighting module |
| CN113608567B (en) * | 2021-08-04 | 2023-03-24 | 北京控制工程研究所 | UC 1843-based programmable constant current source system |
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| CN201204722Y (en) * | 2007-12-28 | 2009-03-04 | 王元成 | Automatic light-adjusting LED illumination driver |
| CN201854484U (en) * | 2010-11-04 | 2011-06-01 | 新视野光电（郑州）有限公司 | High-power LED constant-current driving power circuit |
| CN205319949U (en) * | 2015-12-31 | 2016-06-15 | 重庆川仪速达机电有限公司 | Novel simple and easy switching power supply |
| CN105934044A (en) * | 2016-07-01 | 2016-09-07 | 成都白描网络科技有限公司 | Multi-way output voltage stabilized power supply for LED based on snubber circuit |
| CN106211421A (en) * | 2016-07-01 | 2016-12-07 | 成都白描网络科技有限公司 | A kind of LED multiple-channel output regulated power supply based on overvoltage crowbar |
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|---|---|---|---|---|
| CN201204722Y (en) * | 2007-12-28 | 2009-03-04 | 王元成 | Automatic light-adjusting LED illumination driver |
| CN201854484U (en) * | 2010-11-04 | 2011-06-01 | 新视野光电（郑州）有限公司 | High-power LED constant-current driving power circuit |
| CN205319949U (en) * | 2015-12-31 | 2016-06-15 | 重庆川仪速达机电有限公司 | Novel simple and easy switching power supply |
| CN105934044A (en) * | 2016-07-01 | 2016-09-07 | 成都白描网络科技有限公司 | Multi-way output voltage stabilized power supply for LED based on snubber circuit |
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| CN106604472A (en) | 2017-04-26 |
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