CN100566482C - Light emitting diode drive device - Google Patents

Abstract

The present invention relates to a kind of light emitting diode drive device, in order to the brightness of control light-emitting diode.The present invention includes an energy conversion component and and switch the switch series connection and be coupled to light-emitting diode, be used for control to adjust led current.The diode coupled in parallel is in this energy conversion component, and diode has wheel action, and the energy that is stored on the energy conversion component is discharged through light-emitting diode.A reflected signal and led current that control circuit produces according to energy conversion component are in order to export a control signal control its switch.The amplitude of reflected signal and the temperature correlation of light-emitting diode can be used for adjusting led current.Therefore, the temperature of light-emitting diode can be adjusted led current.

Description

Light emitting diode drive device

Technical field

The present invention relates to a kind of light emitting diode drive device, especially relate to the device of a kind of control circuit in order to the brightness of control light-emitting diode.

Background technology

Light-emitting component is as light-emitting diode (light emission diode; LED) illumination effect is decided by the size that flows through led current, and high-current flow is crossed the illumination effect that light-emitting diode will obtain high brightness, otherwise, flow through led current if reduce, then the brightness of light-emitting diode is with relative weakening.But continue to provide high electric current can reduce the useful life of light-emitting diode, and waste many electric power.Fig. 1 is first embodiment of existing LED driving circuit.Adjustable voltage source 10 flows through light- emitting diode 20,21 by resistor 15 in order to provide ... 25 led current I _LED, and can learn by following formula (1):

$I_{\mathrm{LED}}=\frac{V_{10}-V_{F20}-V_{F21}-..-V_{F25}}{R_{15}}---\left(1\right)$

V wherein _F20, V _F21V _F25Be respectively light- emitting diode 20,21 ... 25 forward pressure drop; R ₁₅Resistance value for resistor 15.

In first embodiment, the major defect of existing LED driving circuit is light- emitting diode 20,21 ... 25 forward pressure drop is not a fixed value, and can be subjected to a large amount of production with the variation of temperature influences led current I _LEDResistor 15 can cause the power loss of circuit simultaneously.

Fig. 2 is second embodiment of existing LED driving circuit.Among second embodiment voltage source 30 in order to provide one fixedly electric power to those light- emitting diodes 20,21 ... 25 use.And light- emitting diode 20,21 ... 25 illumination effect can be adjusted by current source 35.Yet, under this kind control mode, because voltage source 30 is a high pressure, light- emitting diode 20,21 ... 25 pressure drop is a low pressure, so current source 35 can produce great power loss.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of light emitting diode drive device of suitching type to control the brightness of a light-emitting diode, utilizes temperature adjustment to flow through led current, with the colourity and the lumen degree of compensation light-emitting diode.

To achieve these goals, the invention provides a kind of light emitting diode drive device, be used for driving a light-emitting diode, its characteristics are, comprise: an inductor, have one first coil and one second coil, this first coil coupled in series is in this light-emitting diode; One switches switch, and coupled in series is in this light-emitting diode and this first coil, and this diverter switch is controlled a led current, and this led current is the electric current that flows through this light-emitting diode; One first resistance, coupled in series are in this diverter switch, and this this led current of first resistance detection is in order to export a current signal; One control circuit is coupled to this second coil, this first resistance and this diverter switch, and this control circuit is obtained a reflected signal and obtained this current signal from this first resistance from this inductor, in order to export a control signal to this diverter switch; One diode, coupled in parallel, discharge in order to the storage power to this inductor by this light-emitting diode in this inductor and this light-emitting diode; And one second resistance, be coupled to this control circuit, adjust slope in order to determine one, this adjustment slope is represented the relativeness of the variation of the variation of one first critical value of this control circuit and this reflected signal; Wherein, this control signal is controlled this diverter switch and this led current, and when this current signal during greater than this first critical value, this diverter switch is ended; When the storage power of this inductor is discharged fully, again through an adjustable delay after the time, this diverter switch conducting.

Above-mentioned light emitting diode drive device, its characteristics are that this first critical value changes according to this reflected signal.

Above-mentioned light emitting diode drive device, its characteristics are that this control circuit comprises: a delay circuit, according to ending of this control signal, in order to export an inhibit signal, this inhibit signal has the adjustable delay time, and this control signal is to stop using in this adjustable delay time; One comparison circuit, according to this reflected signal less than one second critical value, in order to export an activation signal; One first control circuit is according to this inhibit signal and this enable signal, in order to this control signal of activation; One second control circuit, according to this current signal greater than this first critical value, in order to stop using this control signal; Reach a sample circuit, be coupled to this second coil of this inductor, this sample circuit is according to this reflected signal, in order to export one first sampled signal and one second sampled signal; Wherein, this first sampled signal and this second sampled signal are used for adjusting this first critical value.

Above-mentioned light emitting diode drive device, its characteristics are, this first sampled signal and this second sampled signal be according to first electric current of this light-emitting diode and second electric current of this light-emitting diode, and represent one first one second voltage forward of voltage and this light-emitting diode forward of this light-emitting diode respectively.

Above-mentioned light emitting diode drive device, its characteristics are that this inductor is a transformer.

The present invention also provides a kind of light emitting diode drive device, is used for driving a light-emitting diode, and its characteristics are, comprising: a transformer, have first coil and second coil, and this first coil coupled in series is in this light-emitting diode; One switches switch, and coupled in series is in this light-emitting diode and this first coil, and this diverter switch is used for controlling the electric current of this light-emitting diode; One first resistance, coupled in series are in this diverter switch, and the electric current of this this light-emitting diode of first resistance detection is to export a current signal; One control circuit is coupled to this second coil, this diverter switch and this first resistance, and this control circuit is obtained a reflected signal and this current signal of obtaining from this first resistance to produce a control signal from this second coil; And a diode, coupled in parallel, is discharged in order to the storage power to this transformer by this light-emitting diode in this first coil and this light-emitting diode; Wherein, this control signal of this control circuit output is controlled this diverter switch and this led current, and when this current signal during greater than one first critical value, this diverter switch is ended.

Above-mentioned light emitting diode drive device, its characteristics are that this first critical value changes according to this reflected signal.

Above-mentioned light emitting diode drive device, its characteristics are, also comprise: one second resistance is coupled to this control circuit, in order to determining one to adjust slope, this adjustment slope is represented the relativeness of the variation of the variation of this first critical value of this control circuit and this reflected signal.

Above-mentioned light emitting diode drive device, its characteristics are that this control circuit comprises: a delay circuit, according to ending of this control signal, in order to export an inhibit signal, this inhibit signal has the adjustable delay time, and this control signal is to stop using in the time in this adjustable delay; One comparison circuit, according to this reflected signal less than one second critical value, in order to export an activation signal; One first control circuit is according to this inhibit signal and this enable signal, in order to this control signal of activation; One second control circuit, according to this current signal greater than this first critical value, in order to stop using this control signal; And a sample circuit, being coupled to this energy conversion component, this sample circuit is according to this reflected signal, in order to export one first sampled signal and one second sampled signal; Wherein, this first sampled signal and this second sampled signal are used for adjusting this first critical value.

Above-mentioned light emitting diode drive device, its characteristics are, this first sampled signal and this second sampled signal be according to first electric current of this light-emitting diode and second electric current of this light-emitting diode, and represent one first one second voltage forward of voltage and this light-emitting diode forward of this light-emitting diode respectively.

Effect of the present invention is by reflected signal V _DCan accurately obtain the temperature of light-emitting diode, and utilize temperature adjustment to flow through led current, with the colourity and the lumen degree of compensation light-emitting diode.

Describe the present invention below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.

Description of drawings

Fig. 1 is first embodiment of existing LED control circuit;

Fig. 2 is second embodiment of existing LED control circuit;

Fig. 3 is the circuit diagram of the light emitting diode drive device of suitching type of the present invention;

Fig. 4 A and Fig. 4 B flow through the current waveform schematic diagram of light-emitting diode for the present invention;

Fig. 5 is a control circuit circuit diagram of the present invention;

Fig. 6 is the circuit diagram of delay circuit of the present invention;

Fig. 7 is the circuit diagram of sample circuit of the present invention;

Fig. 8 is the signal waveform schematic diagram of control circuit of the present invention;

Fig. 9 is the circuit diagram of watchdog timer of the present invention; And

Figure 10 is the circuit diagram of matrix current adjustment circuit of the present invention.

Wherein, Reference numeral:

20,21 to 25: light-emitting diode 10: voltage source

15: resistor I _LED: led current

30: voltage source 35: current source

50: energy conversion component N ₁: first coil

N ₂: second coil

70: diverter switch I _LED: led current

75: the first resistance V _S: current signal

V _G: control signal V _D: reflected signal

100: control circuit 57,58: resistor

55: diode V _CC: power supply

V _CNT: control voltage 60: electric current I _LEDWaveform

65: the first critical value V _RMaximum

V _TH: second critical value

180: with door 131: inverter

140: flip-flop INH: inhibit signal

V _F: enable signal 115: second circuit

200: delay circuit V _H1: first sampled signal

V _H2: the second sampled signal OVP: overvoltage signal

600: adjust circuit I _R: decide electric current

500: watchdog timer RST: reset signal

110: comparison circuit V _F: enable signal

V _R: first critical value 300: sample circuit

250: constant current source 210: operational amplifier

205: 59: the second resistance of resistor

220,230,231,270: transistor

260: capacitor 280: inverter

350: pulse generator SMP1: first pulse wave

SMP2: the second pulse wave T _D1: first time of delay

T _D2: second time of delay 310,311: diverter switch

315,317: capacitor 316: transistor

320: comparison circuit 562: capacitor

561: transistor 560: current source

525: inverter 531,532: resistor

510: timer 520: inverter

580: with door

610,611: operational amplifier

620,621: resistor 615: operational amplifier

630 to 635: transistor

I ₆₃₃, I ₆₃₅: electric current 650: resistor

Embodiment

Please refer to Fig. 3, be the circuit diagram of the light emitting diode drive device of suitching type of the present invention.The light emitting diode drive device of suitching type of the present invention uses one first coil N of an energy conversion component 50 ₁Coupled in series is in light-emitting diode 20～25, this first coil N ₁Be an inductor, energy conversion component 50 can be a transformer.One switches switch 70 coupled in series in the first coil N of light-emitting diode 20～25 with energy conversion component 50 ₁, diverter switch 70 is used for controlling led current I _LEDOne first resistance, 75 coupled in series are in this diverter switch 70, and this first resistance 75 detects this led current I _LED, export a current signal V _STo a control circuit 100.As current signal V _SBe higher than one first critical value V in the control circuit 100 _RThe time, diverter switch 70 is ended, and is limited led current I _LEDLed current I _LEDMaximum can learn by following formula (2):

$I_{\mathrm{LED}}\left({\mathrm{}}_{\mathrm{MAX}}\right)=\frac{V_{\mathrm{IN}}-V_{F20}-...-V_{F25}}{{\mathrm{<figure-callout\; id="50"\; label="L"\; filenames="C2005100230580016H1.png"\; state="\{\{state\}\}">L</figure-callout>}}_{50}}\&times;T_{\mathrm{ON}}---\left(2\right)$

In the above-mentioned formula (2), L ₅₀The inductance value of expression energy conversion component 50; T _ONThe ON time of expression diverter switch 70; V _F20, V _F21V _F25Be respectively light-emitting diode 20,21 ... 25 forward pressure drop.

Control circuit 100 also is couple to one second coil N of energy conversion component 50 by resistor 57,58 ₂, in order to receive a reflected signal V _DOne diode, 55 coupled in parallel are in this energy conversion component 50 and light-emitting diode 20～25.When diverter switch 70 is ended, be stored in the energy on the energy conversion component 50, can discharge through light-emitting diode 20～25 and diode 55.Between 70 off periods, the forward voltage of light-emitting diode 20～25 can be from the first coil N of energy conversion component 50 in diverter switch ₁Reflex to the second coil N of energy conversion component 50 ₂

Therefore, the second coil N of energy conversion component 50 ₂Resulting reflected signal V _DCan present the forward voltage of light-emitting diode 20～25.At this, the forward voltage of light-emitting diode 20～25 and the temperature correlation of light-emitting diode 20～25, when voltage forward reduces then increase in temperature, otherwise forward voltage increases then that temperature descends.Therefore, reflected signal V _DCan present the variation of temperature of light-emitting diode 20～25.In addition, when be stored on the energy conversion component 50 energy fully the discharge after, reflected signal V _DCan drop to zero.

In case be stored in energy on the energy conversion component 50 fully after the discharge, control circuit 100 detects and drops to zero reflected signal V _D, can through one time of delay T _DAnd conducting diverter switch 70.Please refer to Fig. 4 A and Fig. 4 B, be led current waveform schematic diagram of the present invention.Wherein, the first critical value V _RMaximum 65 limited led current I _LEDThe peak value of waveform 60, the first critical value V _RMaximum 65 can determine led current I _LEDMean value.Therefore, led current I _LEDMean value be controlled, be a fixed value, and can not change along with the inductance value of energy conversion component 50.Yet, time of delay T _DCan adjust, be used for controlling led current I _LEDAmplitude and the luminosity of light-emitting diode 20～25.

Control circuit 100 is to obtain led current I _LED, and, obtain reflected signal V from this energy conversion component 50 _D, simultaneously, control circuit 100 is according to this reflected signal V _DWith led current I _LEDTo produce a control signal V _G, control signal V _GBe used for the change action of control its switch 70, and then adjust led current I _LEDStable for the colourity that keeps light-emitting diode 20～25 and lumen degree, light-emitting diode 20～25 essential Temperature Influence of considering light-emitting diodes 20～25, and need along with temperature is adjusted led current I _LEDSize.

Among the present invention, the first critical value V _RWith reflected signal V _DRespectively with led current I _LEDAnd temperature correlation.The first critical value V _RChange according to reflected signal V _D, the first critical value V _RColourity and lumen degree in order to compensation light-emitting diode 20～25.In addition, the present invention can further use one second resistance 59 to be coupled to this control circuit 100 in order to adapt to the characteristic of various light-emitting diodes, adjusts slope (slope) in order to determine one, and this adjustment slope is represented the first critical value V _RVariation and this reflected signal V _DThe relativeness of variation.

Please refer to Fig. 5, be the circuit diagram of control circuit of the present invention.In control circuit 100, as this current signal V _SGreater than the first critical value V _RThe time, control signal V _GCan be deactivated, and then this diverter switch 70 is ended.In control circuit 100, as reflected signal V _DLess than one second critical value V _TH, control signal V then _GCan be enabled, thus these diverter switch 70 conductings.One first control circuit include one with door 180, one inverter 131 and a flip-flop 140, first control circuit is according to an inhibit signal INH and an activation signal V _FIn order to export this control signal V _GBe coupled to flip-flop 140 with the output of door 180, and this control signal V _GProduce from the output of flip-flop 140.One second control circuit 115 is coupled to flip-flop 140, as current signal V _SGreater than the first critical value V _RThe time, second control circuit 115 is promptly by flip-flop 140 inactive this control signal V _G

One delay circuit 200 is coupled to and door 180 first input end by inverter 131, and delay circuit 200 is at control signal V _GUnder the dead status, output one has T time of delay _DInhibit signal INH to this and door 180 first input end.So, control signal V _GAt T time of delay _DBe deactivated in during this section.One sample circuit 300 is couple to the second coil N of energy conversion component 50 by resistance 57,58 ₂, this sample circuit 300 is according to this reflected signal V _D, in order to export one first sampled signal V _H1, one second sampled signal V _H2An and overvoltage signal OVP.Overvoltage signal OVP is sent to second input with door 180, in order to the control signal V that stops using _G, make the overvoltage protection of light-emitting diode 20～25.One adjusts circuit 600 is coupled to sample circuit 300 and certain electric current I _R, adjust circuit 600 and receive the first sampled signal V _H1, the second sampled signal V _H2Reach and decide electric current I _R, in order to adjust the first critical value V _RAmplitude.

One watchdog timer (watchdog timer) 500 is coupled to the output and the sample circuit 300 of flip-flop 140, and watchdog timer 500 is according to control signal V _G, in order to exporting a reset signal RST, and reset signal RST is sent to sample circuit 300, in order to replacement sample circuit 300.One comparison circuit 110 is coupled to the 3rd input with door 180, according to this reflected signal V _DLess than the second critical value V _TH, in order to export an activation signal V _F, this enable signal V _FBe coupled to and door 180 the 3rd input, can this control signal of activation V _G

Please refer to Fig. 6, be the circuit diagram of delay circuit of the present invention.In delay circuit 200, one constant current source 250 is coupled to the input IN of control circuit 100, control circuit 100 is coupled to an end of a resistor (not indicating) by this input IN, the other end of this resistor can be couple to a ground connection reference edge, or this input IN also can be coupled to a control voltage V _CNT, can be used for adjusting T time of delay _DThereby, the brightness of control light-emitting diode 20～25.

One voltage includes an operational amplifier 210, a resistor 205 and a transistor 220,230,231.Voltage produces a charging current according to the voltage on the resistor that is coupled to input IN on transistor 231.Also use a capacitor 260 to be coupled to a transistor 231 and a transistor 270 in the delay circuit 200, this transistor 270 is controlled by control signal V _GAs control signal V _GStopping using makes when transistor 270 ends, and the charging current that produces on the transistor 231 is immediately to these capacitor 260 chargings, yet when transistor 270 conductings, the voltage on the capacitor 260 promptly discharges by transistor 270.The input of one inverter 280 is coupled to capacitor 260, and inverter 280 produces this inhibit signal INH according to the voltage of setting up on the capacitor 260 in output.

Please refer to Fig. 7, be the circuit diagram of sample circuit of the present invention.In sample circuit 300, a pulse generator 350 is according to control signal V _GStop using and reflected signal V _DIn order to produce one first pulse wave SMP1 and one second pulse wave SMP2.Cooperate Fig. 8, be the signal waveform schematic diagram of control circuit of the present invention.Wherein, the first pulse wave SMP1 is at control signal V _GAfter stopping using through one first time of delay T _D1And produce.This first time of delay T _D1Can guarantee before the activation first pulse wave SMP1 reflected signal V _DIt is stable state.The second pulse wave SMP2 is at reflected signal V _DDrop to before the null value and produce, and second time of delay T _D2Can guarantee reflected signal V _DDrop to before the null value, produce the second pulse wave SMP2.The first pulse wave SMP1 and the second pulse wave SMP2 respectively control its switch 310,311 conducting or end.Diverter switch 310,311 is respectively to reflected signal V _DTake a sample, and on capacitor 315,317, set up one first sampled signal V respectively _H1With one second sampled signal V _H2Therefore, the first sampled signal V _H1With the second sampled signal V _H2According to one first electric current that flows through light-emitting diode 20～25 and one second electric current, and represent one first voltage and one second voltage forward forward of light-emitting diode 20～25 respectively.

In the sample circuit 300, comprise that also a transistor 316 is coupled to capacitor 315, transistor 316 is controlled by a reset signal RST and this capacitor 315 is discharged.One comparison circuit 320 is coupled to capacitor 315, and comparison circuit 320 is the first sampling voltage V relatively _H1With a critical voltage V _R2, as the first sampling voltage V _H1Greater than critical voltage V _R2Then produce overvoltage signal OVP.

Please refer to Fig. 9, be the circuit diagram of watchdog timer of the present invention.In watchdog timer 500, a reset circuit comprises a capacitor 562, a transistor 561, a current source 560, an inverter 525 and resistor 531,532.Reset circuit is according to power supply V _CCEnable and produce an activating power (power-on reset) signal of resetting.One timer 510 receives control signal V by an inverter 520 _G, as control signal V _GStopping using surpasses all after dates of an overtime (time-out), and timer 510 promptly produces overtime signal output.One 580 is coupled to reset circuit and timer 510 with door, receives with door 580 to start power supply reset signal and overtime signals, exports to produce this reset signal RST.

Please refer to Figure 10, be the circuit diagram of matrix current adjustment circuit of the present invention.In the matrix current adjustment circuit 600, a differential circuit includes operational amplifier 610,611 and resistor 620,621.Differential circuit receives the first sampled signal V _H1With the second sampled signal V _H2, and export a voltage difference in the output of differential circuit.The output of differential circuit is the input that the output of operational amplifier 610 is coupled to an operational amplifier 615.Operational amplifier 615, transistor 630～635 and a resistor 650 form another voltage.This another voltage produces electric current I according to the resistance value of the voltage difference and second resistance 59 ₆₃₃, I ₆₃₅Resistor 650 is coupled to decides electric current I _R, electric current I ₆₃₃And I ₆₃₅, and produce the first critical value V _RBy adjusting electric current I ₆₃₃, I ₆₃₅Current value can adjust the first critical value V effectively _RValue.

The first sampled signal V _H1With the second sampled signal V _H2System gets it by following formula (3), (4) respectively:

$V_{H1}=\frac{R_{58}}{{\mathrm{<figure-callout\; id="57"\; label="R"\; filenames="C2005100230580016H1.png"\; state="\{\{state\}\}">R</figure-callout>}}_{57}+{\mathrm{<figure-callout\; id="58"\; label="R"\; filenames="C2005100230580016H1.png"\; state="\{\{state\}\}">R</figure-callout>}}_{58}}\&times;\frac{N_{T2}}{N_{T1}}\&times;V1---\left(3\right)$

${\mathrm{<figure-callout\; id="2"\; label="V\; H"\; filenames="C2005100230580016H1.png"\; state="\{\{state\}\}">V</figure-callout>}}_H=\frac{R_{58}}{{\mathrm{<figure-callout\; id="57"\; label="R"\; filenames="C2005100230580016H1.png"\; state="\{\{state\}\}">R</figure-callout>}}_{57}+{\mathrm{<figure-callout\; id="58"\; label="R"\; filenames="C2005100230580016H1.png"\; state="\{\{state\}\}">R</figure-callout>}}_{58}}\&times;\frac{N_{T2}}{N_{T1}}\&times;V2---\left(4\right)$

In top formula (3), (4), N _T1, N _T2Represent the first coil N respectively ₁With the second coil N ₂Coil turn; R ₅₇, R ₅₈Be respectively the resistance value of resistor 57,58; V1, V2 are respectively first voltage and second voltage forward forward.

First forward voltage V1 and second forward voltage V2 corresponding to the first led current I ₁With the second led current I ₂, the first led current I ₁With the second led current I ₂Learn by following formula (5), (6) respectively:

I ₁＝I _O×e ^V1/VT (5)

I ₂＝I _O×e ^V2/VT (6)

In formula (5), (6), VT can be learnt by formula (7):

$\mathrm{VT}=\frac{k\&times;\mathrm{Temp}}{q}---\left(7\right)$

In formula (7), Temp can be learnt by formula (8):

$\mathrm{Temp}=\frac{q}{k}\&times;\frac{V1-\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="C2005100230580016H1.png"\; state="\{\{state\}\}">V</figure-callout>}2}{\mathrm{in}\left(\frac{I_1}{I_2}\right)}---\left(8\right)$

Above-mentioned formula (5) is in (8), and k is the graceful now constant of Bao Er (Boltzmann ' s constant); Q is an electronic charge; Temp is an absolute temperature.

In sum, light emitting diode drive device of the present invention is by reflected signal V _DCan accurately obtain the temperature of light-emitting diode 20～25, and utilize temperature adjustment to flow through light-emitting diode 20～25 electric currents, with the colourity and the lumen degree of compensation light-emitting diode 20～25.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of claim of the present invention.

Claims (10)

1, a kind of light emitting diode drive device is used for driving a light-emitting diode, it is characterized in that, comprising:

One inductor has one first coil and one second coil, and this first coil coupled in series is in this light-emitting diode;

One switches switch, and coupled in series is in this light-emitting diode and this first coil, and this diverter switch is controlled a led current, and this led current is the electric current that flows through this light-emitting diode;

One first resistance, coupled in series are in this diverter switch, and this this led current of first resistance detection is in order to export a current signal;

One control circuit is coupled to this second coil, this first resistance and this diverter switch, and this control circuit is obtained a reflected signal and obtained this current signal from this first resistance from this inductor, in order to export a control signal to this diverter switch;

One diode, coupled in parallel, discharge in order to the storage power to this inductor by this light-emitting diode in this inductor and this light-emitting diode; And

One second resistance is coupled to this control circuit, adjusts slope in order to determine one, and this adjustment slope is represented the relativeness of the variation of the variation of one first critical value of this control circuit and this reflected signal;

Wherein, this control signal is controlled this diverter switch and this led current, and when this current signal during greater than this first critical value, this diverter switch is ended; When the storage power of this inductor is discharged fully, again through an adjustable delay after the time, this diverter switch conducting.

2, light emitting diode drive device according to claim 1 is characterized in that, this first critical value changes according to this reflected signal.

3, light emitting diode drive device according to claim 1 is characterized in that, this control circuit comprises:

One delay circuit, according to ending of this control signal, in order to export an inhibit signal, this inhibit signal has the adjustable delay time, and this control signal is to stop using in this adjustable delay time;

One comparison circuit, according to this reflected signal less than one second critical value, in order to export an activation signal;

One first control circuit is according to this inhibit signal and this enable signal, in order to this control signal of activation;

One second control circuit, according to this current signal greater than this first critical value, in order to stop using this control signal: and

One sample circuit is coupled to this second coil of this inductor, and this sample circuit is according to this reflected signal, in order to export one first sampled signal and one second sampled signal;

Wherein, this first sampled signal and this second sampled signal are used for adjusting this first critical value.

4, light emitting diode drive device according to claim 3, it is characterized in that, this first sampled signal and this second sampled signal be according to first electric current of this light-emitting diode and second electric current of this light-emitting diode, and represent one first one second voltage forward of voltage and this light-emitting diode forward of this light-emitting diode respectively.

5, light emitting diode drive device according to claim 1 is characterized in that, this inductor is a transformer.

6, a kind of light emitting diode drive device is used for driving a light-emitting diode, it is characterized in that, comprising:

One transformer has first coil and second coil, and this first coil coupled in series is in this light-emitting diode;

One switches switch, and coupled in series is in this light-emitting diode and this first coil, and this diverter switch is used for controlling the electric current of this light-emitting diode;

One first resistance, coupled in series are in this diverter switch, and the electric current of this this light-emitting diode of first resistance detection is to export a current signal;

One control circuit is coupled to this second coil, this diverter switch and this first resistance, and this control circuit is obtained a reflected signal and obtained this current signal from this first resistance from this second coil, to produce a control signal; And

One diode, coupled in parallel are in this first coil and this light-emitting diode, by this light-emitting diode, in order to this transformer storage power is discharged;

Wherein, this control signal of this control circuit output is controlled the electric current of this diverter switch and this light-emitting diode, and when this current signal during greater than one first critical value, this diverter switch is ended.

7, light emitting diode drive device according to claim 6 is characterized in that, this first critical value changes according to this reflected signal.

8, light emitting diode drive device according to claim 6 is characterized in that, also comprises:

One second resistance is coupled to this control circuit, adjusts slope in order to determine one, and this adjustment slope is represented the relativeness of the variation of the variation of this first critical value of this control circuit and this reflected signal.

9, light emitting diode drive device according to claim 6 is characterized in that, this control circuit comprises:

One delay circuit, according to ending of this control signal, in order to export an inhibit signal, this inhibit signal has the adjustable delay time, and this control signal is to stop using in the time in this adjustable delay;

One comparison circuit, according to this reflected signal less than one second critical value, in order to export an activation signal;

One first control circuit is according to this inhibit signal and this enable signal, in order to this control signal of activation;

One second control circuit, according to this current signal greater than this first critical value, in order to stop using this control signal; And

One sample circuit is coupled to this transformer, and this sample circuit is according to this reflected signal, in order to export one first sampled signal and one second sampled signal;

Wherein, this first sampled signal and this second sampled signal are used for adjusting this first critical value.

10, light emitting diode drive device according to claim 9, it is characterized in that, this first sampled signal and this second sampled signal be according to first electric current of this light-emitting diode and second electric current of this light-emitting diode, and represent one first one second voltage forward of voltage and this light-emitting diode forward of this light-emitting diode respectively.

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