CN208046962U - L ED drive circuit - Google Patents

Abstract

The utility model discloses an L ED drive circuit, including constant-current boost module, L ED control chip, dimmer switch and be used for providing overvoltage protection's overvoltage protection module for dimmer switch, constant-current boost module has the input that steps up, step up output and the controlled end that steps up, dimmer switch has dimming control end, dimming current output and dimming current input, L ED control chip has dimming sampling end and enabling signal output part, overvoltage protection module has overvoltage detection end and overvoltage control end, dimming current output with dimming sampling end connects, enabling signal output part with the controlled end that steps up is connected, dimming current input with overvoltage detection end connects, overvoltage control end with the dimmer control end is connected the utility model discloses appear the short-circuit problem in L ED working circuit, can protect dimmer switch's MOS pipe, avoid unnecessary resource waste effectively, and improved the reliability of power.

Description

LED drive circuit

Technical field

The utility model is related to electronic technology field more particularly to a kind of LED drive circuits.

Background technology

LED light modulations have many modes, according to the different demands that system is applied, have different selections, according to LED output current waves Difference, divide into pulse bandwidth light modulation (PWM Dimming) with simulation light modulation two kinds of (Analog Dimming), so-called pulse wave Width light modulation refers to just that the output current of LED is a LED conducting and the periodic square wave output that LED is not turned on, by change The turn-on time width of square-wave waveform adjusts the average current size of LED, to reach the function of light modulation, preferable in order to reach Pulse wave exports, and is usually all to increase a dimmer switch on the concatenated paths LED.

At present factory repeatedly occurred board without output phenomenon, it is confirmed be dimmer switch damage cause.It is existing shown in Fig. 1 There is a kind of partial structural diagram of LED drive power in technology.Factory is tested using electronic load instead of LED light bar, It will appear the phenomenon of similar LED+ and LED- short circuits when booting, can also carry out LED+ in the test of board physical fault and LED- is short Road.After LED+ and LED- short circuits, square wave control signal PWM_DIM exists, the voltage that VBL is tens volts, because of entire circuit Impedance very little will produce tens amperes of high current and damage dimmer switch.The general way of the prior art is adjusted by increasing The heat-resisting and heat-sinking capability of photoswitch makes it not damage to bear high current.

However, the present inventor when implementing the utility model, it is found that the prior art at least has the following disadvantages, only merely The high current formed after LED operation circuit output short circuit is undertaken using the device of the more preferable heat dissipation performance of bigger, effect difference is not Reliably, it after LED+ and LED- short circuits, has periodic tens amperes of electric current and flows through dimmer switch, need big encapsulation and big Radiator can just it be made not damage, it is of high cost；The electric current that the difference of VBL setting voltages flows through dimmer switch is different, light modulation The heat resistant requirements of switch are different, and the dimmer switch and radiator of selection are different, and the development efficiency thus brought is low, does not sound feasible Border, and the dimmer switch and radiator encapsulated greatly occupies PCB surface product greatly, is unfavorable for PCB arrangements.

Utility model content

Technical problem to be solved by the utility model is to provide a kind of LED drive circuits, can be in LED operation electricity When the output short-circuit of road, control square wave signal-off so that dimmer switch disconnects, and avoids the waste of resource, and improve circuit can By property.

In order to solve the above-mentioned technical problem, the utility model proposes a kind of LED drive circuits, including constant current boost mould Block, LED controls chip, dimmer switch and the overvoltage protective module for providing overvoltage protection for dimmer switch；

The constant current boost module has the boosting input terminal of the supply current for receiving power supply input, for defeated Go out to carry out the supply current electric current after constant current boost to the boosting output end of LED operation circuit and described for receiving LED controls the boosting controlled end of the enable signal of chip；The dimmer switch have brightness adjustment control end, light modulation current output terminal and Light modulation current input terminal for the load outputs for connecting the LED operation circuit；There is the LED controls chip light modulation to adopt Sample end and enable signal output end；The overvoltage protective module has over-pressed test side and over-pressed control terminal；

The light modulation current output terminal is connect with the light modulation sampling end, the enable signal output end with it is described boosting by Control end connection；The light modulation current input terminal is connect with the over-pressed test side, the overvoltage control terminal and the brightness adjustment control End connection.

Preferably, the overvoltage protective module includes first resistor, second resistance, the first capacitance, switching tube and third electricity Resistance；

The over-pressed test side of the overvoltage protective module connects the control terminal of the switching tube by the first resistor, institute It states second resistance to be connected between the control terminal and output end of the switching tube, first capacitance connection is in the switching tube Between control terminal and output end, the output end of the switching tube is grounded, and the input terminal of the switching tube is connected by 3rd resistor The over-pressed control terminal of the overvoltage protective module.

Preferably, the switching tube is N-channel MOS pipe；Wherein, the control terminal of the switching tube is the grid of N-type metal-oxide-semiconductor Pole, the input terminal of the switching tube are the drain electrode of N-type metal-oxide-semiconductor, and the output end of the switching tube is the source electrode of N-type metal-oxide-semiconductor.

Preferably, the dimmer switch includes N-channel MOS pipe；

The brightness adjustment control end of the dimmer switch connects the grid of the N-channel MOS pipe, the light modulation electricity of the dimmer switch Stream output end connects the source electrode of the N-channel MOS pipe, and the light modulation current input terminal of the dimmer switch connects the N-channel MOS The drain electrode of pipe.

Preferably, the dimmer switch further includes：The dimmer switch further includes：First NPN triode, the 2nd NPN tri- Pole pipe, first resistor, second resistance, 3rd resistor, the 4th resistance, the 5th resistance, the 6th resistance, the 7th resistance and the 8th electricity Resistance；

The over-pressed control terminal of the overvoltage protective module connects the base of first NPN triode by the first resistor Pole；The second resistance is connected between the base stage and emitter of first NPN triode, first NPN triode Emitter is grounded；The 3rd resistor is connected between the base stage and emitter of second NPN triode；2nd NPN The base stage of triode connects the collector of first NPN triode, the emitter ground connection of second NPN triode；It is described The collector of first NPN triode is connected for providing the feeder ear of DC voltage by the 4th resistance；It is described to be used to carry The collector of second NPN triode is connected by the 5th resistance for the feeder ear of DC voltage；The 6th resistance connection Between the collector and the grid of the N-channel MOS pipe of second NPN triode；7th resistance is connected to the N Between the source electrode and ground of channel MOS tube；8th resistance is connected between the source electrode and grid of the N-channel MOS pipe.

The utility model embodiment provides a kind of LED drive system, including：LED drive circuit and LED operation circuit；

The LED drive circuit is LED drive circuit as described above；

The up voltage output end of the LED drive circuit connects the power input of the LED operation circuit；

The voltage output end of the LED operation circuit connects the light modulation current input terminal.

Further include the power supply powered for the LED operation circuit as the improvement of said program；The feeder ear of the power supply It is connect with the boosting input terminal of the LED drive circuit.

Implement the utility model, has the advantages that：

The LED drive circuit that the utility model embodiment provides, by setting for providing overvoltage protection for dimmer switch Overvoltage protective module, and overvoltage protective module over-pressed test side connection it is defeated for connecting the load of the LED operation circuit The light modulation current input terminal of outlet, the brightness adjustment control of over-pressed control terminal connection dimmer switch；Specifically, when the electricity at load supplying end When pressure increases, the over-pressed test side of the overvoltage protective module samples the voltage, is more than in the sample voltage value When higher than preset detection voltage value, the over-pressed control terminal of the overvoltage protective module drags down pulse-width signal, to drag down Dimmer switch grid and source voltage close the dimmer switch, are disconnected the access of the LED operation circuit, the pulsewidth Modulated current signal disappears, and the dimmer switch is flowed through with regard to no high current, when efficiently solving the LED operation short circuit The problem of damaging the dimmer switch, and the unnecessary wasting of resources is avoided, improve the reliability of circuit.

Description of the drawings

Fig. 1 is a kind of partial structural diagram of LED drive circuit in the prior art；

Fig. 2 is the structural schematic diagram for the LED drive circuit that the utility model one embodiment provides；

Fig. 3 is the structural representation of the overvoltage protective module for the LED drive circuit that second embodiment of the utility model provides Figure；

Fig. 4 is the structural schematic diagram for the LED drive system that the utility model third embodiment provides.

Specific implementation mode

The following will be combined with the drawings in the embodiments of the present invention, carries out the technical scheme in the embodiment of the utility model Clearly and completely describe, it is clear that the described embodiments are only a part of the embodiments of the utility model, rather than whole Embodiment.Based on the embodiments of the present invention, those of ordinary skill in the art are without creative efforts The every other embodiment obtained, shall fall within the protection scope of the present invention.

In actual application, the load supplying end of LED drive circuit, which is used to connect, to be born by Constant Electric Current is signal-powered It carries, such as LED load.Factory uses electronic load that LED light bar is replaced to test more at present, will appear in booting similar LED+ with The phenomenon of LED- short circuits, and LED+ and LED- short circuits can be also carried out in the test of board physical fault, in LED operation circuit When LED+ and LED- short circuits, it will the high current for generating dozens of Ann times damages the metal-oxide-semiconductor of dimmer switch, in the dimmer switch Metal-oxide-semiconductor damage after, board there have been without output phenomenon.

Fig. 2 is referred to, is the structural schematic diagram for the LED drive circuit that the utility model one embodiment provides,.

LED drive circuit provided in this embodiment includes constant current boost module 10, LED controls chip 20, dimmer switch 30 With the overvoltage protective module 40 for providing overvoltage protection for dimmer switch；

The constant current boost module 10 has the boosting input terminal of the supply current for receiving the input of power supply 50, uses In export to the supply current carry out constant current boost after electric current to the boosting output end of LED operation circuit 60 and for receiving The boosting controlled end of the enable signal of the LED controls chip 20；The dimmer switch 30 has brightness adjustment control end, light modulation electric current The light modulation current input terminal of output end and load outputs for connecting the LED operation circuit 50；The LED controls chip 20 have light modulation sampling end and enable signal output end；There is the overvoltage protective module 40 over-pressed test side and overvoltage to control End.

The light modulation sampling end that the light modulation current output terminal of the dimmer switch 30 controls chip 20 with the LED is connect, institute The enable signal output end for stating LED control chips 20 is connect with the boosting controlled end of the constant current boost module 10；The light modulation The light modulation current input terminal of switch 30 is connect with the over-pressed test side of the overvoltage protective module 40, the overvoltage protective module 40 Over-pressed control terminal connect with the brightness adjustment control end of the dimmer switch 30.

In the present embodiment, the power supply 50 is 10 He of constant current boost module for realizing the conversion of voltage Dimmer switch 30 provides DC voltage.The supply current that the power supply 50 inputs is the electric current exported by AC-DC converter, The AC-DC converter output voltage terminal VBL connects the boosting input terminal of the constant current boost module 10.

In the present embodiment, the voltage signal that the constant current boost module 10 is used to export the power supply 50 converts Constant current voltage signal simultaneously boosts, and gives LED works for exporting the electric current after carrying out constant current boost to the supply current through described Make the load outputs output of circuit 60.The boosting input terminal of the constant current boost module 10 is exported with the AC-DC converter Voltage end VBL connections, the boosting output end of the constant current boost module 10 connect with the load input terminal of the LED operation circuit 60 It connects, the enable signal output end of the boosting controlled end and LED control chips 20 of the constant current boost module 10 is receiving The LED controls chip 20 sends the supply current that enable signal inputs the power supply 50 and controls, including, in institute When to state input signal that constant current boost module 10 receives be high levle, the boosting controlled end is triggered by constant current boost module 10 In switching tube conducting, carry out energy storage and release can, bring the voltage up to be enough to make in the LED operation circuit 60 LED string lead It is logical；When the input signal that the constant current boost module 10 receives is low level, the boosting controlled end is triggered by constant current liter Switching tube cut-off in die block 10, the undertension that the constant current boost module 10 exports is so that the LED operation circuit 60 In LED string conducting.

In the present embodiment, skilled person will appreciate that, the light modulation sampling end of the LED controls chip 20 is for receiving The sample information of the light modulation current output terminal output current, so that the LED controls chip 20 and adjusts drive according to sample information The output of dynamic boosting controlled end, achievees the purpose that constant current boost.Wherein, the working frequency of the boosting controlled end is 100KHz, The pulse-width modulation circuit of the duty ratio of the enable signal is adjusted according to the electric current received from the light modulation current output terminal, and Enable signal is exported to constant current boost module 10 by the enable signal output end, including, from light modulation current output terminal When the input signal received is low level, the pulse-width modulation circuit of the duty ratio of the enable signal is adjusted, exports low level Signal gives the constant current boost module 10；When the input signal received from light modulation current output terminal is high levle, institute is adjusted The pulse-width modulation circuit for stating the duty ratio of enable signal exports high levle signal to the constant current boost module 10.

In the present embodiment, the dimmer switch 30 passes through for being dimmed on pulse bandwidth dimmer application circuit Control the square wave that 30 output current of the dimmer switch is 200Hz.The brightness adjustment control end receives described for being dimmer switch There is provided the over-pressed pulse-width signal controlled that the overvoltage protective module 40 of overvoltage protection is sent, wherein the pulsewidth modulation letter Number working frequency be 200Hz, when it is high levle to receive the input signal of the transmission of the overvoltage protective module 40, output is high Level current signal controls chip 20 to the LED, while the dimmer switch 30 is connected；Receiving the overvoltage protection mould When the input signal that block 40 is sent is low level, exports low level current signal and control chip 20, while the tune to the LED Photoswitch 30 is not turned on.

In the present embodiment, the overvoltage protective module 40 for providing overvoltage protection for dimmer switch is used for basis The working condition of LED operation circuit 60 carries out overvoltage protection.Detect the LED in the over-pressed test side of the overvoltage protective module 40 The voltage of operating circuit 60, according to the voltage by over-pressed control terminal output pulse width modulated signal, including, in over-pressed test side The voltage for receiving the LED operation circuit 60, is detected the voltage, is detecting inspection of the voltage higher than setting When surveying voltage value, the pulse-width signal is dragged down, output pulse width modulated signal is low level signal.

The operation principle of LED drive circuit provided in this embodiment is as follows：

In short circuit, the overvoltage protective module 40 detects inspection of the voltage higher than setting of the LED operation circuit 60 When surveying voltage value, the pulse-width signal is dragged down, output pulse width modulated signal is low level signal, and the LED controls chip It is described when the signal that 20 light modulation sampling end samples the light modulation current output terminal of the dimmer switch 30 is low level signal LED controls the exporting as low level signal to the constant current boost mould according to sample information adjustment driving boosting controlled end of chip 20 The boosting controlled end of block 10, when the input signal that receives of boosting controlled end is low level, then the constant current boost module Switching tube cut-off in 10 passes through the undertension of the boosting output end output of the constant current boost module 10 without boosting So that the LED string conductings in the LED operation circuit 60, while the low level pulse-width signal is closed by over-pressed control terminal The dimmer switch 30 is closed, the electric current of the LED operation circuit 60 is ended, and then can be in short circuit by LED operation circuit electricity Stream cut-off, then the metal-oxide-semiconductor on the dimmer application circuit in dimmer switch is protected.

Advantageous effect：Overvoltage is added between the light modulation light modulation current input terminal to open the light and brightness adjustment control end because using Protection module, so overcome in LED operation short circuit, high current is by dimmer switch by the metal-oxide-semiconductor in dimmer switch The technological deficiency of damage, and then when having reached short-circuit, high efficient and reliable protects dimmer switch technique effect.

Fig. 3 is referred to, is the overvoltage protective module for the LED drive circuit that second embodiment of the utility model provides Structural schematic diagram；The specific knot of the overvoltage protective module of LED drive circuit provided by the utility model is described below with reference to Fig. 3 Structure：

The overvoltage protective module 40 includes first resistor R1, second resistance R2, the first capacitance C1, switching tube Q1 and third Resistance R3；

The over-pressed test side of the overvoltage protective module 40 connects the control of the switching tube Q1 by the first resistor R1 End processed, the second resistance R2 are connected between the control terminal and output end of the switching tube Q1, the first capacitance C1 connections Between the control terminal and output end of the switching tube, the output end of the switching tube Q1 is grounded, the input of the switching tube Q1 End connects the over-pressed control terminal of the overvoltage protective module by 3rd resistor R3.

Further, the switching tube Q1 is N-channel MOS pipe；Wherein, the control terminal of the switching tube Q1 is N-type metal-oxide-semiconductor Grid, the input terminal of the switching tube Q1 is the drain electrode of N-type metal-oxide-semiconductor, and the output end of the switching tube Q1 is N-type metal-oxide-semiconductor Source electrode.

The operation principle of overvoltage protective module 40 is described so that switching tube Q1 is N-channel MOS pipe as an example：

The output voltage of the LED operation circuit 60 flows through first resistor by the over-pressed test side of overvoltage protective module 40 R1 and second resistance R2, wherein the ends LED- of the overvoltage test side access LED operation circuit, the first resistor R1 and the The output voltage of the LED- is carried out partial pressure sampling by two resistance R2, and the first capacitance C1 is connected to the both ends the second resistance R2, Interference signal is eliminated, sampled voltage after first resistor R1 and second resistance R2 is divided the output voltage, which is higher than, to be set When fixed detection voltage value, that is, when being higher than the conducting voltage Vgs of the switching tube Q1, the switching tube Q1 conductings, the overvoltage The over-pressed control terminal of protection module connects the input terminal of the switching tube Q1 by 3rd resistor R3, wherein the overvoltage detection It terminates into pulse width modulation controlled end PWM_DIM, the port PWM_DIM realizing that pulsewidth dims depending on the user's operation； Then the pulse-width signal is grounded by the 3rd resistor R3 and switching tube Q1, and then the pulse-width signal is drawn It is low.

It should be noted that the switching tube Q1 is only described by taking N-type metal-oxide-semiconductor as an example, may be replaced by triode, The three ports for control such as field-effect tube, IGBT, thyristor device or its derivation device.

Advantageous effect：Because using sampling resistor carries out voltage sample, pulse-width signal is controlled by control circuit Output, so overcome in LED operation short circuit, the pulse-width signal is there are still in circuit, power supply side Tens volts of voltages dimmer switch is reached by LED operation circuit, entire LED operation circuit loop impedance very little, and then generate The technological deficiency that the high current of dozens of Ann times damages MOS in dimmer switch, and then when having reached short-circuit, drag down pulsewidth modulation letter Number, the MOS technology effect from high efficient and reliable protection dimmer switch on source.

LED drive circuit provided by the utility model, by the way that overvoltage protective module, the overvoltage of the overvoltage protective module is arranged Test side is connect with the voltage output end of LED operation circuit, that is, is connect with the light modulation current input terminal of dimmer switch, in institute When stating LED operation short circuit, the overvoltage protective module detects high voltage, and exports the pulsewidth modulation letter of low level Number, control LED control chips are failure to actuate, and then are controlled constant current boost module and do not boosted, and are exported to the LED operation circuit Undertension so that LED operation circuit LED string conducting, simultaneously closed off the dimmer switch, be disconnected it is described light modulation open The metal-oxide-semiconductor of pass, then current cut-off can be effectively so as to the protective effect of metal-oxide-semiconductor in realizing in short circuit to dimmer switch The unnecessary wasting of resources is avoided, and improves the reliability of power supply.

Fig. 4 is the structural schematic diagram for the LED drive system that the utility model third embodiment provides；

LED drive system provided in this embodiment includes：LED drive circuit and LED operation circuit 60；

The LED drive circuit 60 is the LED drive circuit 20 that first embodiment described above applies example to second；

The up voltage output end of the LED drive circuit connects the power input of the LED operation circuit 60；

The voltage output end of the LED operation circuit 50 connects the light modulation current input terminal.

Further, further include the power supply 50 powered for the LED operation circuit 60；The feeder ear VBL of the power supply with The boosting input terminal of the LED drive circuit connects.

Further, the dimmer switch 30 includes N-channel MOS pipe Q2；

The brightness adjustment control end of the dimmer switch 30 connects the grid of the N-channel MOS pipe Q2, the dimmer switch 30 Light modulation current output terminal connects the source electrode of the N-channel MOS pipe Q2, and the light modulation current input terminal of the dimmer switch 30 connects institute State the drain electrode of N-channel MOS pipe Q2.

Still further, the dimmer switch 30 further includes：First NPN triode Q3, the second NPN triode Q4, first Resistance R4, second resistance R5,3rd resistor R6, the 4th resistance R7, the 5th resistance R8, the 6th resistance R9, the 7th resistance R10 and Eight resistance R11；

The over-pressed control terminal of the overvoltage protective module passes through first resistor R4 connections the first NPN triode Q3 Base stage；The second resistance R5 is connected between the base stage and emitter of the first NPN triode Q3, the first NPN The emitter of triode Q3 is grounded；The 3rd resistor R6 be connected to the base stage of the second NPN triode Q4 and emitter it Between；The base stage of the second NPN triode Q4 connects the collector of the first NPN triode Q3, second NPN triode The emitter of Q4 is grounded；The feeder ear LED_VIN for providing DC voltage passes through the 4th resistance R7 connections described first The collector of NPN triode Q3；The feeder ear LED_VIN for providing DC voltage passes through described in the 5th resistance R8 connections The collector of second NPN triode Q4；The 6th resistance R9 is connected to the collector of the second NPN triode Q4 and described Between the grid of N-channel MOS pipe Q2；The 7th resistance R10 is connected between the source electrode and ground of the N-channel MOS pipe Q2；Institute The 8th resistance R11 is stated to be connected between the source electrode and grid of the N-channel MOS pipe Q2.

The operation principle of LED drive system provided in this embodiment is as follows：

In short circuit, the voltage of the LED- of LED operation circuit 60 will be high, and the overvoltage protective module 40 is by sampling electricity The voltages that sample of resistance R1 and R2 higher than setting detection voltage value when, then switching tube Q1 is connected, then by switching tube Q1 and rises The pulse-width signal accessed to the R3 of metering function will flow to ground, and then the pulse-width signal is pulled low, pulsewidth tune Signal end PWM_DIM processed has accessed dimmer switch 30 by resistance R4, and the pulse-width signal passes through resistance R9 access switches Pipe Q2, the pulse-width signal voltage are less than the switching tube Q2 turn-on voltages, then the switching tube Q2 cut-offs.And it is described Tenth resistance R10 limitations flow through the electric current of dimmer switch 30, and the pulse-width signal accesses the LED by resistance R9 and controls The light modulation sampling end LED_FB of chip 20, the light modulation sampling end receive the light modulation current output terminal and sample output current value When less than preset current value, the LED control chips 20 adjust driving boosting controlled end LED_GATE's according to sample information Output exports low level signal, when the input signal that the constant current boost circuit 10 receives is low level, triggers the liter Controlled end is pressed to end the switching tube in constant current boost module 10, the undertension that the constant current boost module 10 exports is so that institute State the LED string conductings in LED operation circuit 60.

Advantageous effect：Overvoltage is added between the light modulation light modulation current input terminal to open the light and brightness adjustment control end because using Protection module, in short circuit, closing needs switching tube to be protected, and resistance current limliting, the energy supply of control circuit, so overcoming is arranged In LED operation short circuit, high current by dimmer switch by the technological deficiency of the metal-oxide-semiconductor damage in dimmer switch, with Reach the technique effect of protection dimmer switch.

The above is preferred embodiments of the present invention, it is noted that for the ordinary skill of the art For personnel, without departing from the principle of this utility model, several improvement and deformations can also be made, these improve and become Shape is also considered as the scope of protection of the utility model.

Claims (7)

1. a kind of LED drive circuit, which is characterized in that including：Constant current boost module, LED control chip, dimmer switch and are used for The overvoltage protective module of overvoltage protection is provided for dimmer switch；

The constant current boost module has the boosting input terminal of the supply current for receiving power supply input, for output pair Electric current after the supply current progress constant current boost is controlled to the boosting output end of LED operation circuit and for receiving the LED The boosting controlled end of the enable signal of coremaking piece；The dimmer switch has brightness adjustment control end, light modulation current output terminal and is used for Connect the light modulation current input terminal of the load outputs of the LED operation circuit；The LED controls chip has light modulation sampling end With enable signal output end；The overvoltage protective module has over-pressed test side and over-pressed control terminal；

The light modulation current output terminal is connect with the light modulation sampling end, the enable signal output end and the boosting controlled end Connection；The light modulation current input terminal is connect with the over-pressed test side, and the overvoltage control terminal connects with the brightness adjustment control end It connects.

2. LED drive circuit as described in claim 1, which is characterized in that the overvoltage protective module includes first resistor, Two resistance, the first capacitance, switching tube and 3rd resistor；

The over-pressed test side of the overvoltage protective module connects the control terminal of the switching tube by the first resistor, and described Two resistance are connected between the control terminal and output end of the switching tube, control of first capacitance connection in the switching tube Between end and output end, the output end of the switching tube is grounded, described in the input terminal of the switching tube is connected by 3rd resistor The over-pressed control terminal of overvoltage protective module.

3. LED drive circuit as claimed in claim 2, which is characterized in that the switching tube is N-channel MOS pipe；Wherein, institute The control terminal for stating switching tube is the grid of N-type metal-oxide-semiconductor, and the input terminal of the switching tube is the drain electrode of N-type metal-oxide-semiconductor, the switch The output end of pipe is the source electrode of N-type metal-oxide-semiconductor.

4. LED drive circuit as described in claim 1, which is characterized in that the dimmer switch includes N-channel MOS pipe；

The brightness adjustment control end of the dimmer switch connects the grid of the N-channel MOS pipe, and the light modulation electric current of the dimmer switch is defeated Outlet connects the source electrode of the N-channel MOS pipe, and the light modulation current input terminal of the dimmer switch connects the N-channel MOS pipe Drain electrode.

5. LED drive circuit as claimed in claim 4, which is characterized in that the dimmer switch further includes：Tri- poles first NPN Pipe, the second NPN triode, first resistor, second resistance, 3rd resistor, the 4th resistance, the 5th resistance, the 6th resistance, the 7th electricity Resistance and the 8th resistance；

The over-pressed control terminal of the overvoltage protective module connects the base stage of first NPN triode by the first resistor； The second resistance is connected between the base stage and emitter of first NPN triode, the transmitting of first NPN triode Pole is grounded；The 3rd resistor is connected between the base stage and emitter of second NPN triode；Tri- poles 2nd NPN The base stage of pipe connects the collector of first NPN triode, the emitter ground connection of second NPN triode；For providing The feeder ear of DC voltage connects the collector of first NPN triode by the 4th resistance；It is described to be used to provide direct current The feeder ear of pressure connects the collector of second NPN triode by the 5th resistance；6th resistance is connected to described Between the collector of two NPN triodes and the grid of the N-channel MOS pipe；7th resistance is connected to the N-channel MOS Between the source electrode and ground of pipe；8th resistance is connected between the source electrode and grid of the N-channel MOS pipe.

6. a kind of LED drive system, which is characterized in that including：LED drive circuit and LED operation circuit；

The LED drive circuit is such as LED drive circuit described in any one of claim 1 to 5；

The up voltage output end of the LED drive circuit connects the power input of the LED operation circuit；

The voltage output end of the LED operation circuit connects the light modulation current input terminal.

7. LED drive system as claimed in claim 6, which is characterized in that further include the electricity powered for the LED operation circuit Source；The feeder ear of the power supply is connect with the boosting input terminal of the LED drive circuit.