CN102905443B - Linear constant-current and current-sharing LED drive circuit and circuit board structure thereof - Google Patents
Linear constant-current and current-sharing LED drive circuit and circuit board structure thereof Download PDFInfo
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Abstract
The invention discloses a linear constant-current and current-sharing LED drive circuit and a circuit board structure thereof, relating to a drive circuit of a vehicle LED illuminating device and configuration of elements of the drive circuit. The linear constant-current and current-sharing LED drive circuit comprises a reference voltage unit, a constant current feedback unit and a multi-channel sampling and current sharing unit, wherein the multi-channel sampling and current sharing unit is correspondingly connected to all channels of LED strings of the multi-channel LED light emitting module; all channels of current sampling feedback ends are connected in parallel to the feedback signal input end of the constant current feedback unit; and LED currents are automatically regulated according to an LED gear resistor arranged on an LED circuit board, one constant current feedback unit is used for controlling the currents of the multiple channels of LED strings, has multiple functions of constant current, current sharing, LED gear and PWM (Pulse Width Modulation) dimming, and can meet various practical demands in electronic illumination of automobile; and the complexity of design and production of the LED drive circuit is greatly lowered, and error probability is lowered. Any parameter of any element on the control circuit board is not needed to be changed in a production or maintenance process, high interchangeability of the circuit board can be realized, and the production efficiency is increased.
Description
Technical field
The present invention relates to the layout for general vehicle illumination or signalling, relate in particular to the layout for drive circuit and the element thereof of LED lighting device.
Background technology
The remarkable advantages such as LED has fast response time, low-power consumption, energy-conservation, the life-span is long.Due to the rapid response speed of LED, be specially adapted to the application of automobile brake lamp and direction indicator lamp, can reduce the probability of happening of the traffic accidents such as rear-end collision.Along with the raising of semi-conducting material and packaging technology, luminous flux and the light extraction efficiency of LED light source improve gradually, and LED light source has been widely used in the special lighting fields such as traffic lights, automotive lighting, billboard.LED Driving technique is also progressively developed along with the development of LED application technology.
Therefore LED is a kind of along with the variation by LED current value changes the well-illuminated light emitting source of light, if need LED luminous constant, must control that to flow through the current value of LED constant.Conventionally the LED adopting drives constant current method to have linear adjustable type and two kinds of methods of switch regulating type.The core technology of linear regulation formula is to utilize the switching tube that works in the range of linearity to carry out control load as a dynamic adjustable resistance, to guarantee in the situation that input voltage changes, the switching tube different power consumption of loading, thus the electric current that flows through LED load is remained unchanged substantially.But this Driving technique is subject to the restriction of input voltage range, load LED number is restricted, and for Vehicular lamp, limited by vehicle power supply voltage, and the LED being connected in series is generally below 3.When having, be greater than the LED of 3 and need when driven, conventionally to need multi-channel linear adjustable type circuit to drive LED multi-path string, to guarantee that the number in every paths of LEDs string is less than or equal to 3.Chinese invention patent application " a kind of multichannel constant-current control circuit that is applicable to LED driver " (application for a patent for invention number: 200910153405.8 publication numbers: CN101674693A) disclose a kind of multichannel constant-current control circuit that is applicable to LED driver, comprise single output constant current source and multiplex output circuit, it is characterized in that each described output circuit comprises a constant current branch road, an equalizing control circuit and the load being formed by a plurality of LED lamps, the input of described every way equalizing control circuit is from the sampled signal of this road sample resistance to output current, after this road constant current branch road conversion, become public connecting line, link together with other each road, become current-sharing bus, every road current sampling signal and current-sharing bus voltage compare after adjusting in equalizing control circuit inside, the output signal of equalizing control circuit can be controlled the linear impedance magnitude of adjusting pipe of corresponding constant current branch road, then control the size of every road electric current, realize current-sharing.Although the technical scheme of this invention has solved the problem that multiple constant current is controlled, but each road output circuit of this technical scheme comprises a constant current branch road and an equalizing control circuit, circuit structure is complicated, not only improved cost, the increase of circuit elements device also can reduce reliability.
Enter Chinese PCT application for a patent for invention " for the integrated LED drive unit of a plurality of LED string current sharings " (Chinese invention patent application number: 02815162.3 publication number: CN1537403A) disclose a kind of integrated LED drive unit for a plurality of LED strings, this drive unit uses single linear adjuster or other controller and a multi-output current mirror, and this multi-output current mirror depends on hardly DC input voltage source, depends on hardly the variation of the transistor that causes due to semiconductor integrated technique or MOSFET, and depend on hardly variations in temperature.Multi-output current mirror comprises a plurality of transistors or MOSFET, and each in them is integrated on identical substrate, has identical wide-long raceway groove ratio and identical source electrode connection and is connected with grid.This integrated LED drive unit provides automatic current to share under DC pattern, and or under PWM pattern, has minimum phase delay.This mirror image current mirror output comprises a plurality of mirror images-common grid common source transistor pair.Yet, the technical scheme of this invention is that utilization is integrated on identical substrate, a plurality of transistors or the MOSFET of same structure, form multi-output current mirror and realize flow equalizing function, this technical scheme is the sampling resistor of connecting again after the parallel connection of multi-path flow equalizing metal-oxide-semiconductor source electrode, can only change by changing the value of sampling resistor the electric current sum of LED multi-path string so simultaneously, lack flexibility, can not adapt to the coupling of the LED of different brightness shelves.
In addition, there is gear problem in LED, and LED manufacturer can not only supply the LED of same brightness shelves, and the LED of different brightness gears must mate the different luminous consistency of LED electric current guarantee.And in producing, if the LED of every kind of brightness gear is removed to design the control board of different electric currents, not only waste time and energy and easily make mistakes, and can cause product to lack interchangeability, make troubles to the after-sale service of product.
Summary of the invention
The object of this invention is to provide a kind of linear constant current current-sharing LED drive circuit, there is constant current, current-sharing, LED and divide the multi-functional of gear, PWM light modulation, meet the every actual demand in automotive electronics illumination, reduce complexity and wrong probability in design and production, enhance productivity.
The present invention solves the problems of the technologies described above adopted technical scheme:
A kind of linear constant current current-sharing LED drive circuit, be used to LED multi-path light emitting module that the drive current of equalization stable is provided, described LED multi-path light emitting module comprises at least 2 paths of LEDs strings, and each paths of LEDs string comprises respectively at least 1 LED element being connected in series, and it is characterized in that:
Described LED drive circuit comprises reference voltage unit, constant current feedback unit and multi-channel sampling current-sharing unit;
The reference voltage output terminal of described reference voltage unit, is connected to the reference voltage input terminal of constant current feedback unit, institute
State the output of constant current feedback unit, be connected to the input of described multi-channel sampling current-sharing unit;
Described LED drive circuit also comprises that the LED that is connected to reference voltage unit divides gear resistance, and described LED divides the resistance of gear resistance, is to match according to the brightness gear of the LED element of described LED multi-path light emitting module;
Corresponding to each paths of LEDs string of LED multi-path light emitting module, described multi-channel sampling current-sharing unit arranges a road constant current branch road; Described constant current branch road comprises that one with constant flow element and a sampling resistor being connected in series with constant flow element of controlling the utmost point, and the constant current output end of each branch road constant flow element is connected respectively to a corresponding paths of LEDs string; The control utmost point of all each branch road constant flow elements links together, and forms the input of multi-channel sampling current-sharing unit; Being connected in series a little of each branch road constant flow element and sampling resistor, links together by a feedback resistance respectively, is connected to the feedback signal input of described constant current feedback unit; The constant current control output end of constant current feedback unit, is connected to the input of described multi-channel sampling current-sharing unit, forms Closed-loop Constant-current control loop.
A kind of preferably technical scheme of linear constant current current-sharing LED drive circuit of the present invention, is characterized in that described reference voltage unit comprises the voltage stabilizing circuit that current-limiting resistance R2, voltage-stabiliser tube Z1 and diode D2 form; The output end of pressure-stabilizing of described voltage stabilizing circuit, be connected to the bleeder circuit that divider resistance R3 and R4 form, the dividing point of bleeder circuit forms the reference voltage output terminal of described reference voltage unit, by the low pass filter being formed by resistance R 5 and capacitor C 3, be connected to the reference voltage input terminal of described constant current feedback unit.
A kind of better technical scheme of linear constant current current-sharing LED drive circuit of the present invention, it is characterized in that described constant current feedback unit comprises operational amplifier A R1A, the in-phase input end of described operational amplifier A R1A, as the reference voltage input terminal of constant current feedback unit, be connected to described reference voltage unit; Each road current sample feedback end of described multi-channel sampling current-sharing unit, respectively by described feedback resistance, is parallel-connected to the inverting input of described operational amplifier A R1A, forms the feedback signal input of described constant current feedback unit; The output of described operational amplifier A R1A, connects the low pass filter being comprised of resistance R 8 and capacitor C 5, forms the output of constant current feedback unit, is connected to the input of described multi-channel sampling current-sharing unit.
A kind of improved technical scheme of linear constant current current-sharing LED drive circuit of the present invention, is characterized in that the described constant flow element with controlling the utmost point is power stage triode; The described control utmost point is the base stage of power stage triode, and the base stage of the power stage triode of each constant current branch road is connected in parallel, and forms the input of described multi-channel sampling current-sharing unit; The collector electrode of each road power stage triode, forms Yi road, multi-channel sampling current-sharing unit constant current output end, is connected to a paths of LEDs string of LED multi-path light emitting module; The emitter of each road power stage triode is by described sampling resistor ground connection, being connected in series a little of the emitter of power stage triode and sampling resistor, by a feedback resistance, link together respectively, be connected to the feedback signal input of described constant current feedback unit.
The improved technical scheme of another kind of linear constant current current-sharing LED drive circuit of the present invention, is characterized in that the described constant flow element with controlling the utmost point is power stage metal-oxide-semiconductor; The described control utmost point is the grid of power stage metal-oxide-semiconductor, and the grid of the power stage metal-oxide-semiconductor of each constant current branch road is connected in parallel, and forms the input of described multi-channel sampling current-sharing unit; The drain electrode of each road power stage metal-oxide-semiconductor, forms Yi road, multi-channel sampling current-sharing unit constant current output end, is connected to a paths of LEDs string of LED multi-path light emitting module; The source electrode of each road power stage metal-oxide-semiconductor is by described sampling resistor ground connection, being connected in series a little of the source electrode of power stage metal-oxide-semiconductor and sampling resistor, by a feedback resistance, link together respectively, be connected to the feedback signal input of described constant current feedback unit.
A kind of further improved technical scheme of linear constant current current-sharing LED drive circuit of the present invention, it is characterized in that described constant current branch road is provided with the shunt resistance in parallel with constant flow element, one end of described shunt resistance is connected to described constant current output end, the other end of described shunt resistance be connected to constant flow element and sampling resistor be connected in series a little on.
A kind of preferred technical scheme of linear constant current current-sharing LED drive circuit of the present invention, it is characterized in that described LED drive circuit also comprises PWM light modulation metal-oxide-semiconductor Q4, external PWM signal input is connected to the grid of metal-oxide-semiconductor Q4, the source electrode pin ground connection of metal-oxide-semiconductor Q4, the drain electrode of metal-oxide-semiconductor Q4 is connected to the dividing point of divider resistance R3 and R4, by the pwm signal of light modulation metal-oxide-semiconductor Q4 grid, control the reference voltage of constant current feedback unit, the conduction ratio that changes each road power component of multi-channel sampling current-sharing unit, carries out PWM light modulation to LED multi-path light emitting module.
The preferred technical scheme of another kind of linear constant current current-sharing LED drive circuit of the present invention, after it is characterized in that described LED divides gear resistance to connect with resistance R 15, is connected in parallel with the divider resistance R3 of described reference voltage unit.
Another object of the present invention is to provide a kind of circuit board structure of linear constant current current-sharing LED drive circuit, can distinguish voluntarily LED brightness gear according to the circuit element parameter of LED wiring board, thereby do not need to change any parameter of any element on control board, can automatically regulate LED electric current according to the brightness gear of LED circuit onboard led, realize the height interchangeability of wiring board product.
The present invention solves the problems of the technologies described above adopted technical scheme:
A kind of printed circuit board structure for above-mentioned linear constant current current-sharing LED drive circuit, described printed substrate comprises LED wiring board and control circuit board, described in it is characterized in that, be connected in series the LED element of channeling LED light emitting module, be arranged on described LED wiring board; The circuit element of described reference voltage unit, constant current feedback unit and multi-channel sampling current-sharing unit, is arranged on described control circuit board, connects to form described LED drive circuit; Described LED divides the resistance of gear resistance, is to match according to the brightness gear of the LED element of installing on LED wiring board; Described LED divides gear resistance to be arranged on LED wiring board, by step resistance link, is connected to the reference voltage unit on control circuit board; Multi-channel sampling current-sharing unit on control circuit board, by constant current output end, is connected to each paths of LEDs string on LED wiring board.
The invention has the beneficial effects as follows:
1. linear constant current current-sharing LED drive circuit of the present invention, only use a constant current feedback unit to control the electric current of LED multi-path string, there is constant current, current-sharing, LED and divide the multi-functional of gear, PWM light modulation, can adapt to the inside and outside LED illumination of car and the alarm function requirement of various different automobile types, different purposes, meet the every actual demand in automotive electronics illumination, the complexity that can greatly reduce LED drive circuit design and produce, reduces wrong probability.
2. linear constant current current-sharing LED drive circuit of the present invention, no matter whether LED number on every string LED string equates, by setting, be connected on the sampling resistor in each road sampling constant current branch road, just the drive current that flows through this paths of LEDs string can be set, and keep constant current to drive, the short circuit of any paths of LEDs string or wherein any one LED element or open circuit, can not affect the drive current of other each paths of LEDs string; By shunt resistance in parallel on constant flow element, can in high input voltage situation, to constant flow element, shunt, reduce power consumption and the heat of constant flow element, thereby can significantly improve the reliability of product and the flexibility of control.
3. linear constant current current-sharing LED drive circuit of the present invention, by the LED being arranged on LED wiring board, divide gear resistance, distinguish voluntarily LED brightness gear, can automatically regulate LED electric current according to the brightness gear of LED circuit onboard led, therefore, in production or maintenance process, do not need to change any parameter of any element on control circuit board, can realize the height interchangeability of wiring board product, enhance productivity.
Accompanying drawing explanation
Fig. 1 is the electrical schematic diagram of the linear constant current current-sharing of the present invention LED drive circuit.
In figure, 100-LED multi-path light emitting module, 200-reference voltage unit, 300-constant current feedback unit, 400-multi-channel sampling current-sharing unit, solid wire frame PCB1 represents LED wiring board, solid wire frame PCB2 represents control circuit board.
Embodiment
In order to understand better technique scheme of the present invention, below in conjunction with drawings and Examples, describe in detail further.
Linear constant current current-sharing LED drive circuit of the present invention, is used to LED multi-path light emitting module 100 that the drive current of equalization stable is provided, and LED multi-path light emitting module 100 comprises at least 2 paths of LEDs strings, and each paths of LEDs string comprises respectively at least 1 LED element being connected in series.Be subject to the restriction of operating voltage, LED number≤3 of conventionally connecting in each paths of LEDs string.In the embodiment shown in fig. 1, LED multi-path light emitting module 100 comprises 3 paths of LEDs strings, input voltage Vcc, through Anti-surging and the filter circuit of TVS pipe or transient voltage suppressor diode T1, capacitor C 1 and resistance R 1 composition, holds via anti-reverse diode D1 the positive pole that is connected to each paths of LEDs string by LED+.In figure, the first paths of LEDs string is composed in series by LED element LED1, LED2 and LED3, and its negative pole is connected to LED-1 end; The second paths of LEDs string is composed in series by LED element LED4 and LED5, and its negative pole is connected to LED-2 end; Third Road LED string only comprises LED element LED6, and its negative pole is connected to LED-3 end.
LED drive circuit of the present invention comprises reference voltage unit 200, constant current feedback unit 300 and multi-channel sampling current-sharing unit 400; In Fig. 1 with the above-mentioned unit of empty wire frame representation.
The reference voltage output terminal of reference voltage unit 200 (A point in Fig. 1), by the low pass filter being formed by resistance R 5 and capacitor C 3, be connected to the reference voltage input terminal (A1 point in Fig. 1) of constant current feedback unit 300, the output of constant current feedback unit 300, is connected to the input (B point in Fig. 1) of multi-channel sampling current-sharing unit 400.
Corresponding to each paths of LEDs string of LED multi-path light emitting module 100, multi-channel sampling current-sharing unit 400 arranges a road constant current branch road; Described constant current branch road comprises that one with constant flow element Q1, the Q2 and Q3 and sampling resistor Rs1, Rs2 or the Rs3 who is connected in series with constant flow element that control the utmost point, the constant current output end of each branch road constant flow element (F1 in Fig. 1, F2 and F3 point), is connected to a corresponding paths of LEDs string by LED-1, LED-2 and LED-3 end respectively; The control utmost point of all each branch road constant flow elements links together, and forms the input (B point in Fig. 1) of multi-channel sampling current-sharing unit 400; Being connected in series a little of each branch road constant flow element and sampling resistor, links together by feedback resistance Rf1, a Rf2 or Rf3 respectively, is connected to the feedback signal input (C point in Fig. 1) of described constant current feedback unit 300; The constant current control output end of constant current feedback unit 300, is connected to the input (B point in Fig. 1) of described multi-channel sampling current-sharing unit 400, forms Closed-loop Constant-current control loop.
By sampling resistor Rs1, Rs2 or the Rs3 of each constant current branch road are set, the present invention can control respectively the electric current of each paths of LEDs string, take the embodiment shown in Fig. 1 as example, Rs1=Rs2=Rs3 can be set, make the electric current of 3 paths of LEDs strings identical, also Rs1 ≠ Rs2 ≠ Rs3 can be set, make to flow through different electric currents in 3 paths of LEDs strings, therefore linear constant current current-sharing LED drive circuit of the present invention is compared with existing technical scheme, has greater flexibility.
In the embodiment of the of the present invention linear constant current current-sharing LED drive circuit shown in Fig. 1, reference voltage unit 200 comprises the voltage stabilizing circuit that current-limiting resistance R2, voltage-stabiliser tube Z1 and diode D2 form; Input voltage Vcc is connected to current-limiting resistance R2 through anti-reverse diode D1, current-limiting resistance R2 is connected with the negative pole of voltage-stabiliser tube Z1, the output end of pressure-stabilizing D that forms voltage stabilizing circuit, the positive pole of voltage-stabiliser tube Z1 is connected with the positive pole of diode D2, and the negative pole of diode D2 is connected to ground.By the series connection of voltage-stabiliser tube Z1 and diode D2, can offset temperature under different temperatures and float the impact on reference voltage.The output end of pressure-stabilizing D of voltage stabilizing circuit, be connected to the bleeder circuit that divider resistance R3 and R4 form, the dividing point of bleeder circuit (A point in Fig. 1) forms the reference voltage output terminal of reference voltage unit 200, by the low pass filter being formed by resistance R 5 and capacitor C 3, be connected to the reference voltage input terminal (A1 point in Fig. 1) of constant current feedback unit 300.
In the embodiment of the of the present invention linear constant current current-sharing LED drive circuit shown in Fig. 1, constant current feedback unit 300 comprises operational amplifier A R1A, the in-phase input end of operational amplifier A R1A, reference voltage input terminal (A1 point in Fig. 1) as constant current feedback unit, is connected to reference voltage unit 200; Each road current sample feedback end of multi-channel sampling current-sharing unit 400, respectively by feedback resistance Rf1, Rf2, Rf3, is parallel-connected to the inverting input of described operational amplifier A R1A, forms the feedback signal input of constant current feedback unit 300; The output of operational amplifier A R1A, connects the low pass filter being comprised of resistance R 8 and capacitor C 5, forms the output of constant current feedback unit 300, is connected to the input (B point in Fig. 1) of multi-channel sampling current-sharing unit 400.
In the embodiment of the of the present invention linear constant current current-sharing LED drive circuit shown in Fig. 1, with the constant flow element of controlling the utmost point, be power stage triode Q1, Q2 and Q3; The described control utmost point is the base stage of power stage triode, and power stage triode Q1, the Q2 of each constant current branch road and the base stage of Q3 are connected in parallel, and forms the input of described multi-channel sampling current-sharing unit 400; The collector electrode of each road power stage triode Q1, Q2 or Q3, form multi-channel sampling current-sharing unit 400 mono-road constant current output end (F1 in Fig. 1, F2 and F3 point), by LED-1, LED-2 and LED-3, hold, be connected to a paths of LEDs string of LED multi-path light emitting module 100; The emitter of each road power stage triode Q1, Q2, Q3, by described sampling resistor Rs1, Rs2, Rs3 ground connection, the emitter of power stage triode Q1, Q2, Q3 and sampling resistor Rs1, Rs2, Rs3 are connected in series a little, by feedback resistance Rf1, Rf2, Rf3, link together respectively, be connected to the feedback signal input of described constant current feedback unit 300, namely the inverting input of operational amplifier A R1A (C point in Fig. 1).This circuit structure of the present invention has been realized the constant current feedback unit 300 forming with an operational amplifier, controls the electric current flowing through on LED multi-path electric current string simultaneously, no matter whether LED the number of connecting in each paths of LEDs string equates.
Although constant flow element Q1, Q2 and Q3 with controlling the utmost point in the embodiment shown in Fig. 1 are power stage triodes, linear constant current current-sharing LED drive circuit of the present invention equally also can adopt power MOS pipe to form sampling constant current branch road.In the situation that adopting power MOS pipe, the control utmost point of constant flow element is the grid of power stage metal-oxide-semiconductor, and the grid of the power stage metal-oxide-semiconductor of each constant current branch road is connected in parallel, and forms the input of described multi-channel sampling current-sharing unit; The drain electrode of each road power stage metal-oxide-semiconductor, forms Yi road, multi-channel sampling current-sharing unit constant current output end, is connected to a paths of LEDs string of LED multi-path light emitting module 100; The source electrode of each road power stage metal-oxide-semiconductor is by described sampling resistor Rs1, Rs2, Rs3 ground connection, the source electrode of power stage metal-oxide-semiconductor and sampling resistor Rs1, Rs2, Rs3 are connected in series a little, by feedback resistance Rf1, Rf2, Rf3, link together respectively, be connected to the feedback signal input of described constant current feedback unit 300, namely the inverting input of operational amplifier A R1A (C point in Fig. 1).
In the embodiment of the of the present invention linear constant current current-sharing LED drive circuit shown in Fig. 1, each constant current branch road is provided with the shunt resistance R41 in parallel with constant flow element, R42, R43, constant flow element is power stage triode Q1 in this embodiment, Q2, Q3, shunt resistance R41, one end of R42 or R43 is connected to the described constant current output end (F1 in Fig. 1, F2 and F3 point), be namely power stage triode Q1, Q2, the collector electrode of Q3, shunt resistance R41, the other end of R42 or R43, be connected to constant flow element and sampling resistor be connected in series a little on, be namely power stage triode Q1, Q2, the emitter of Q3.Shunt resistance R41, R42, the R43 of parallel connection between the collector and emitter of power stage triode, its effect is in high input voltage situation, power stage triode as constant flow element is shunted, thereby reduced power consumption and the heat of constant flow element in high input voltage situation.
In the embodiment of the of the present invention linear constant current current-sharing LED drive circuit shown in Fig. 1, LED drive circuit also comprises PWM light modulation metal-oxide-semiconductor Q4, external PWM signal input is connected to the grid of metal-oxide-semiconductor Q4, the source electrode pin ground connection of metal-oxide-semiconductor Q4, the drain electrode of metal-oxide-semiconductor Q4 is connected to the dividing point A of divider resistance R3 and R4.Existing PWM light regulating technology adopts the direct power ratio control output element of pwm signal to realize PWM light modulation conventionally, be different from existing PWM light regulating technology, LED drive circuit of the present invention is by the pwm signal of light modulation metal-oxide-semiconductor Q4 grid, control the reference voltage of constant current feedback unit 300, thereby change the conduction ratio of 400Ge road, multi-channel sampling current-sharing unit power component simultaneously, each paths of LEDs string of LED multi-path light emitting module 100 is realized to PWM light modulation simultaneously.
According to the embodiment shown in Fig. 1, linear constant current current-sharing LED drive circuit of the present invention also comprises that LED divides gear resistance R bin, after LED divides gear resistance R bin to connect with resistance R 15, is connected in parallel with the divider resistance R3 of reference voltage unit 200.In the embodiment shown in fig. 1, use solid wire frame to schematically illustrate the printed circuit board structure for above-mentioned linear constant current current-sharing LED drive circuit, in this embodiment, printed substrate is divided into LED wiring board PCB1 and control circuit board PCB2, the solid wire frame representation LED wiring board PCB1 on Fig. 1 top, the LED element of LED multi-path light emitting module 100, is arranged on LED wiring board PCB1 upper, is connected in series and forms 3 paths of LEDs strings; The solid wire frame representation control circuit board PCB2 on Fig. 1 top, the circuit element of reference voltage unit 200, constant current feedback unit 300 and multi-channel sampling current-sharing unit 400, is arranged on control circuit board PCB2 upper, connects to form LED drive circuit of the present invention; Described LED divides the resistance of gear resistance, is to match according to the brightness gear of the upper LED element of installing of LED wiring board PCB1; It is upper that LED divides gear resistance R bin to be arranged on LED wiring board PCB1, and by step resistance link Rbin+ and Rbin-, LED divides gear resistance R bin to be connected to the reference voltage unit 200 on control circuit board PCB2; Multi-channel sampling current-sharing unit 400 on control circuit board PCB2, by constant current output end LED-1, LED-2 and LED-3, is connected to each paths of LEDs string on LED wiring board PCB1.So, the present invention can be by changing the circuit board structure of linear constant current current-sharing LED drive circuit, realization is distinguished LED brightness gear voluntarily according to the circuit element parameter of LED wiring board PCB1, thereby do not need to change any parameter of the upper any element of control circuit board PCB2, can automatically regulate LED electric current according to the brightness gear of the upper LED of LED wiring board PCB1, realize the height interchangeability of wiring board product.
Those of ordinary skill in the art will be appreciated that; above embodiment is only for technical scheme of the present invention is described; and be not used as limitation of the invention; any variation of the above embodiment being done based on connotation of the present invention, modification, all will drop in the protection range of claim of the present invention.
Claims (9)
1. a linear constant current current-sharing LED drive circuit, be used to LED multi-path light emitting module that the drive current of equalization stable is provided, described LED multi-path light emitting module comprises at least 2 paths of LEDs strings, and each paths of LEDs string comprises respectively at least 1 LED element being connected in series, and it is characterized in that:
Described LED drive circuit comprises reference voltage unit, constant current feedback unit and multi-channel sampling current-sharing unit;
The reference voltage output terminal of described reference voltage unit, is connected to the reference voltage input terminal of constant current feedback unit, and the output of described constant current feedback unit is connected to the input of described multi-channel sampling current-sharing unit;
Described LED drive circuit also comprises that the LED that is connected to reference voltage unit divides gear resistance, and described LED divides the resistance of gear resistance, is to match according to the brightness gear of the LED element of described LED multi-path light emitting module;
Corresponding to each paths of LEDs string of LED multi-path light emitting module, described multi-channel sampling current-sharing unit arranges a road constant current branch road; Described constant current branch road comprises that one with constant flow element and a sampling resistor being connected in series with constant flow element of controlling the utmost point, and the constant current output end of each branch road constant flow element is connected respectively to a corresponding paths of LEDs string; The control utmost point of all each branch road constant flow elements links together, and forms the input of multi-channel sampling current-sharing unit; Being connected in series a little of each branch road constant flow element and sampling resistor, links together by a feedback resistance respectively, is connected to the feedback signal input of described constant current feedback unit; The constant current control output end of constant current feedback unit, is connected to the input of described multi-channel sampling current-sharing unit, forms Closed-loop Constant-current control loop.
2. linear constant current current-sharing LED drive circuit according to claim 1, is characterized in that described reference voltage unit comprises the voltage stabilizing circuit that current-limiting resistance R2, voltage-stabiliser tube Z1 and diode D2 form; The output end of pressure-stabilizing of described voltage stabilizing circuit, be connected to the bleeder circuit that divider resistance R3 and R4 form, the dividing point of bleeder circuit forms the reference voltage output terminal of described reference voltage unit, by the low pass filter being formed by resistance R 5 and capacitor C 3, be connected to the reference voltage input terminal of described constant current feedback unit.
3. linear constant current current-sharing LED drive circuit according to claim 1, it is characterized in that described constant current feedback unit comprises operational amplifier A R1A, the in-phase input end of described operational amplifier A R1A, as the reference voltage input terminal of constant current feedback unit, be connected to described reference voltage unit; Each road current sample feedback end of described multi-channel sampling current-sharing unit, respectively by described feedback resistance, is parallel-connected to the inverting input of described operational amplifier A R1A, forms the feedback signal input of described constant current feedback unit; The output of described operational amplifier A R1A, connects the low pass filter being comprised of resistance R 8 and capacitor C 5, forms the output of constant current feedback unit, is connected to the input of described multi-channel sampling current-sharing unit.
4. linear constant current current-sharing LED drive circuit according to claim 1, is characterized in that the described constant flow element with controlling the utmost point is power stage triode; The described control utmost point is the base stage of power stage triode, and the base stage of the power stage triode of each constant current branch road is connected in parallel, and forms the input of described multi-channel sampling current-sharing unit; The collector electrode of each road power stage triode, forms Yi road, multi-channel sampling current-sharing unit constant current output end, is connected to a paths of LEDs string of LED multi-path light emitting module; The emitter of each road power stage triode is by described sampling resistor ground connection, being connected in series a little of the emitter of power stage triode and sampling resistor, by a feedback resistance, link together respectively, be connected to the feedback signal input of described constant current feedback unit.
5. linear constant current current-sharing LED drive circuit according to claim 1, is characterized in that the described constant flow element with controlling the utmost point is power stage metal-oxide-semiconductor; The described control utmost point is the grid of power stage metal-oxide-semiconductor, and the grid of the power stage metal-oxide-semiconductor of each constant current branch road is connected in parallel, and forms the input of described multi-channel sampling current-sharing unit; The drain electrode of each road power stage metal-oxide-semiconductor, forms Yi road, multi-channel sampling current-sharing unit constant current output end, is connected to a paths of LEDs string of LED multi-path light emitting module; The source electrode of each road power stage metal-oxide-semiconductor is by described sampling resistor ground connection, being connected in series a little of the source electrode of power stage metal-oxide-semiconductor and sampling resistor, by a feedback resistance, link together respectively, be connected to the feedback signal input of described constant current feedback unit.
6. linear constant current current-sharing LED drive circuit according to claim 1, it is characterized in that described constant current branch road is provided with the shunt resistance of constant flow element parallel connection, one end of described shunt resistance is connected to described constant current output end, the other end of described shunt resistance be connected to constant flow element and sampling resistor be connected in series a little on.
7. linear constant current current-sharing LED drive circuit according to claim 1, it is characterized in that described LED drive circuit also comprises PWM light modulation metal-oxide-semiconductor Q4, external PWM signal input is connected to the grid of metal-oxide-semiconductor Q4, the source electrode pin ground connection of metal-oxide-semiconductor Q4, the drain electrode of metal-oxide-semiconductor Q4 is connected to the dividing point of divider resistance R3 and R4, by the pwm signal of light modulation metal-oxide-semiconductor Q4 grid, control the reference voltage of constant current feedback unit, the conduction ratio that changes each road power component of multi-channel sampling current-sharing unit, carries out PWM light modulation to LED multi-path light emitting module.
8. linear constant current current-sharing LED drive circuit according to claim 2, after it is characterized in that described LED divides gear resistance to connect with resistance R 15, is connected in parallel with the divider resistance R3 of described reference voltage unit.
9. the printed circuit board structure for the linear constant current current-sharing LED drive circuit described in arbitrary claim of claim 1 to 8, described printed substrate comprises LED wiring board and control circuit board, described in it is characterized in that, be connected in series the LED element of channeling LED light emitting module, be arranged on described LED wiring board; The circuit element of described reference voltage unit, constant current feedback unit and multi-channel sampling current-sharing unit, is arranged on described control circuit board, connects to form described LED drive circuit; Described LED divides the resistance of gear resistance, is to match according to the brightness gear of the LED element of installing on LED wiring board; Described LED divides gear resistance to be arranged on LED wiring board, by step resistance link, is connected to the reference voltage unit on control circuit board; Multi-channel sampling current-sharing unit on control circuit board, by constant current output end, is connected to each paths of LEDs string on LED wiring board.
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Address after: 201800 Yecheng Road, Jiading District, Jiading District, Shanghai Patentee after: Hua Yu vision technology (Shanghai) Co., Ltd. Address before: 201800 Yecheng Road, Jiading District, Jiading District, Shanghai Patentee before: Xiaoxi Car Lights Co., Ltd., Shanghai |