CN103957643A - Driving device of light emitting diode and driving method thereof - Google Patents
Driving device of light emitting diode and driving method thereof Download PDFInfo
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- CN103957643A CN103957643A CN201410203222.3A CN201410203222A CN103957643A CN 103957643 A CN103957643 A CN 103957643A CN 201410203222 A CN201410203222 A CN 201410203222A CN 103957643 A CN103957643 A CN 103957643A
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Abstract
The invention discloses a driving device of a light emitting diode and a driving method thereof. In the driving method, it is detected whether the driving device performs dimming or not. If detected that the driving device performs dimming, it is judged whether the duty factor of a dimming signal is smaller than a preset value or not. When the duty factor of the dimming signal is larger than the preset value, multiple driving currents are adjusted and output within a period, and the output time of the driving currents is equal to the period. When the duty factor of the dimming signal is smaller than the preset value, the driving currents are respectively output within the period, and the output time of the driving currents is smaller than the period. Therefore, voice frequency noise and electromagnetic interference caused by overlarge sum variation of the driving currents can be inhibited.
Description
Technical field
The present invention relates to a kind of driving method, and be particularly related to a kind of Drive And Its Driving Method of light-emitting diode.
Background technology
Light-emitting diode (Light Emitting Diode, hereinafter to be referred as: volume LED) is little, power saving and durable, and along with the maturation of processing procedure, prices, recently more and more general as the product of light source with light-emitting diode.In addition, light-emitting diode operating voltage low (only 1.5-3V), can active illuminating and have certain brightness, brightness voltage available or electric current regulate, possess shock-resistant, anti-vibration, the feature in life-span long (100,000 hours) simultaneously, so, light-emitting diode is widely used in various terminal equipments, from car headlamp, traffic lights, indicator by character, billboard and large screen video display, to common and architectural lighting and liquid crystal display, (Liquid Crystal Display, hereinafter to be referred as the field such as backlight LCD).
With light emitting diode drive device, one of conventional dimming mode is for utilizing PM (pulse-width modulation, hereinafter to be referred as the duty factor of technological adjustment pulse (duty) PWM), adjust with this equivalent current that output stage exports light-emitting diode to and adjust light-emitting diode luminance.But in the time using PM to carry out light modulation, the current switching of its output stage output moves as switch.And this current switching action meeting is taken out a year variation greatly to the voltage of output stage, cause voltage to have the generation of excessive ripple (ripple).Simultaneously, excessive ripple can cause great changes of magnetic field to the inductance in circuit, and electric capacity in circuit can cause vibration (sharply vibrate) tempestuously to produce deformation (shape-changing) because the change in voltage of moment is excessive, therefore produce audio-frequency noise (audio noise).
Figure 1A is the system schematic of the drive unit of a traditional light-emitting diode.Please refer to Figure 1A, drive unit 100 comprises electric pressure converter 110, conversion loop control unit 120, amplifier 130, voltage selector 140 and the current drives unit 150 being made up of a plurality of current driving elements.Electric pressure converter 110 receives supply voltage V
dD, and electric pressure converter 110 is according to output generation and the supply voltage V of conversion loop control unit 120
dDthe not operating voltage V of coordination standard
cC.The positive input terminal of amplifier 130 receives reference voltage Vref, and the voltage exported of its negative input end receiver voltage selector 140, and output voltage is to control conversion loop control unit 120 according to this, and wherein reference voltage Vref is a fixed value.Voltage selector 140 is in order to select the voltage of output light emitting diode tandem 50_1～50_n negative pole end wherein.The positive terminal of LED serial 50_1～50_n receives operating voltage V
cC, the negative pole end utmost point of LED serial 50_1～50_n couples by switch S 1～Sn and current drives unit 150 respectively, and by load current i
1～i
ndrive LED serial 50_1～50_n luminous, and switch S 1～Sn carries out the switching of switch according to dim signal simultaneously, carry out the action of light modulation with this.
Figure 1B is the sequential chart of the drive current of Figure 1A.Please refer to Figure 1A and Figure 1B, in light emitting diode drive device 100, conventional PM technology is adjusted offered load current i
1～i
ntime t
1adjust the luminous brightness of light-emitting diode.In other words, in fixing cycle T, time t
1the brightness meeting of longer light-emitting diode is higher; Otherwise, time t
1the brightness meeting of shorter light-emitting diode is lower.But using PM while carrying out light modulation, the load current i causing is moved in the switching of switch S 1～Sn
1～i
nvariation.Above-mentioned load current i
1～i
nvariation can make operating voltage V
cCthere is to take out greatly to carry to change the operating voltage V that causes electric pressure converter 110 to be exported
cChave the generation of excessive ripple.Simultaneously, electric pressure converter 110 input currents also have great instantaneous variation, except allowing the inductance in electric pressure converter 110 cause great changes of magnetic field, also allow the electric capacity of voltage regulation in electric pressure converter 110 vibrate tempestuously and produce deformation because transient voltage changes excessive, therefore produce audio-frequency noise.In addition,, with drive unit 100, in the time carrying out light modulation, its switch S 1～Sn can switch simultaneously, to make load current i simultaneously
1～i
nswitching action, and current switching action can cause serious electromagnetic interference (Electromagnetic Disturbance, hereinafter to be referred as: EMI).
Summary of the invention
The invention provides a kind of Drive And Its Driving Method of light-emitting diode, can suppress audio-frequency noise and electromagnetic interference.
The present invention proposes a kind of driving method of light-emitting diode, is applicable to a drive unit.This driving method comprises: whether detecting drive unit carries out light modulation; Carry out light modulation if drive unit is detected, judge whether the duty factor of a dim signal is less than a preset value; In the time that the duty factor of dim signal is more than or equal to preset value, adjust the size of current of multiple drive currents, and export these drive currents in a cycle, wherein the output time of these drive currents equals the cycle; And, in the time that the duty factor of dim signal is less than preset value, in the cycle, export respectively these drive currents, wherein the output time of these drive currents is less than the cycle.
The present invention proposes a kind of driving method of light-emitting diode, is applicable to a drive unit.Driving method comprises: receive a dim signal; Whether detecting drive unit carries out light modulation; And, if being detected, drive unit carries out light modulation, adjust other size of current in multiple drive currents according to a duty factor of dim signal, so that the summation of these drive currents in the cycle is proportional to the duty factor of dim signal.
The present invention proposes a kind ofly to comprise multiple switches in order to drive the drive circuit of multiple light-emitting diodes, a light modulation detector, and a current control unit.These switches are in order to couple these light-emitting diodes.Light modulation detector is in order to receive a dim signal and to export a light-modulating mode signal according to dim signal.Current control unit is in order to export multiple control signals according to light-modulating mode signal and dim signal, and wherein these control signals are controlled respectively the conducting state of these switches.
Based on above-mentioned, the Drive And Its Driving Method of light-emitting diode of the present invention, when the duty factor of carrying out light modulation and dim signal when drive unit is less than preset value, the output time of the each drive current of uniform distribution in a cycle, and adjust accordingly the size of current of each drive current.When the duty factor of carrying out light modulation and dim signal when drive unit is more than or equal to preset value, output driving current simultaneously in the cycle, and adjust the size of drive current according to dim signal.By this, can suppress excessive caused audio-frequency noise and the electromagnetic interference of summation variation of drive current.
For above-mentioned feature and advantage of the present invention can be become apparent, special embodiment below, and coordinate accompanying drawing to be described in detail below.
Brief description of the drawings
Figure 1A is the system schematic of the drive unit of a traditional light-emitting diode.
Figure 1B is the sequential chart of the drive current of Figure 1A.
Fig. 2 A is the circuit diagram of the drive unit of one embodiment of the invention.
Fig. 2 B is the current waveform schematic diagram of the LED serial of Fig. 2 A.
Fig. 2 C is another current waveform schematic diagram of the LED serial of Fig. 2 A.
Fig. 2 D is the drive unit of Fig. 2 A and the waveform schematic diagram of LED serial.
Fig. 2 E is the circuit diagram that the current control unit of Fig. 2 A couples light modulation detector.
Fig. 2 F is the circuit diagram that the duty factor of Fig. 2 E turns electric pressure converter.
Fig. 2 G is another circuit diagram that the duty factor of Fig. 2 E turns electric pressure converter.
Fig. 2 H is another circuit diagram that the current control unit of Fig. 2 A couples light modulation detector.
Fig. 2 I is the circuit diagram again that the current control unit of Fig. 2 A couples light modulation detector.
Fig. 3 A is the flow chart of the driving method of one embodiment of the invention.
Fig. 3 B is the flow chart of the driving method of another embodiment of the present invention.
Main element symbol description:
50_1～50_n: LED serial 100,200: drive unit
110,210: electric pressure converter 120,220: conversion loop control unit
130,230: amplifier 140,240: voltage selector
150,250: current drives unit 260: light modulation detector
261: analog-digital converter 262: or door
270: current control unit 271, mux1: multiplexer
272,274,275: disperse delay cell 273,276: duty factor turns electric pressure converter
D: size of current S1～Sn, SW1～SWn: switch
Scol: control signal Smod: light-modulating mode signal
Sdim: dim signal t
1, t
2: the time
T: cycle GN: gain signal
I
1～i
n: load current V
r: reference voltage
V
dD: supply voltage V
cC: operating voltage
Vref: reference voltage I
1～I
n: drive current
Vcol: control voltage LPF1, LPF2: low-pass filter circuit
R1, R2: resistance C1, C2: electric capacity
ML1: analog multiplier S301, S302, S311～S313: according to this
Invent the step of the driving method of all embodiment
Embodiment
Fig. 2 A is the circuit diagram of the drive unit of one embodiment of the invention.Please refer to Fig. 2 A, drive unit 200 comprises electric pressure converter 210, conversion loop control unit 220, amplifier 230, voltage selector 240, current drives unit 250, light modulation detector 260, current control unit 270 and switch SW 1～SWn.Light modulation detector 260 receives dim signal Sdim, whether to carry out light modulation and to export accordingly light-modulating mode signal Smod according to dim signal Sdim detecting drive unit 200.Current control unit 270 is exported multiple control signal Scol and is controlled voltage Vcol according to light-modulating mode signal Smod and dim signal Sdim, whether to utilize these control signals Scol difference control switch SW1～SWn conducting, and adjust drive current I by controlling voltage Vcol control current drives unit 250
1～I
nsize.
Electric pressure converter 210 receives supply voltage V
dD, and the adjustment signal of exporting according to conversion loop control unit 220 produces and supply voltage V
dDthe not operating voltage V of coordination standard
cC.The voltage that conversion loop control unit 220 receives according to it produces adjusts signal.The positive input terminal of amplifier 230 receives reference voltage V
r, and the voltage exported of its negative input end receiver voltage selector 240, and output voltage is to changing loop control unit 220 according to this, wherein reference voltage Vref can be a fixed value.Voltage selector 240 is in order to select the voltage of output light emitting diode tandem 50_1～50_n negative pole end wherein.The positive terminal of LED serial 50_1～50_n receives operating voltage V
cC, the negative pole end utmost point of LED serial 50_1～50_n couples by switch SW 1～SWn and current drives unit 250 respectively, and by drive current I
1～I
ndrive LED serial 50_1～50_n luminous.
In the time that the duty factor of dim signal Sdim is 100%, represent that drive unit 200 can not carry out light modulation.Now, current control unit 270 can produce control signal Scol control switch SW1～SWn conducting simultaneously in a cycle according to light-modulating mode signal Smod, and is adjusted and controlled drive current I by control voltage Vcol
1～I
nsize of current D be upper current limit value.In the time that the duty factor of dim signal Sdim is not 100%, represent that drive unit 200 can carry out light modulation.Now, the control signal Scol that current control unit 270 produces according to light-modulating mode signal Smod equally taking control switch SW1～SWn the ON time in a cycle for equating or impartial, and adjust drive current I by controlling voltage Vcol control current drives unit 250
1～I
nsize, wherein current drives unit 250 can be made up of multiple voltage-controlled current source, simultaneously to adjust drive current I according to controlling voltage Vcol
1～I
nsize.It is worth mentioning that, the pass whether duty factor of dim signal Sdim and drive unit 200 carry out light modulation is in order to explanation, and visual actual demand and changing.
Furthermore bright drive unit 200 carries out the action of light modulation, and Fig. 2 B is the current waveform schematic diagram of the LED serial of Fig. 2 A.Please refer to Fig. 2 A and Fig. 2 B, when the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is more than or equal to preset value, current control unit 270 produces multiple control signal Scol and controls voltage Vcol according to light-modulating mode signal Smod and light-modulating mode signal Sdim.These control signals Scol can keep conducting by control switch SW1～SWn in cycle T simultaneously, so that drive current I to be provided simultaneously
1～I
nto LED serial 50_1～50_n.Electric current on LED serial 50_1～50_n can present direct current shape but not pulse type because switch SW 1～SWn keeps conducting.And drive current I is adjusted according to controlling voltage Vcol in current drives unit 250
1～I
nsize of current D, wherein size of current D can be relevant to the duty factor of dim signal Sdim, for example duty factor is 1/8, size of current D can equal 1/8 of upper current limit value.And above-mentioned preset value can be that cycle T is divided by drive current I
1～I
nnumber n, the number n of for example drive current is 8,1/8 (being T/8) that preset value is the cycle.
Fig. 2 C is another current waveform schematic diagram of the LED serial of Fig. 2 A.Please refer to Fig. 2 A and Fig. 2 C, when the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is less than preset value, current control unit 270 produces multiple control signal Scol and controls voltage Vcol according to light-modulating mode signal Smod and dim signal Sdim equally.These control signals Scol can the ON time t of control switch SW1～SWn in cycle T
2for equalization, with difference output driving current I
1～I
nto LED serial 50_1～50_n, the quantity of for example switch is 8, ON time t
2it was 1/8 cycle.Drive current I is adjusted according to controlling voltage Vcol in current drives unit 250
1～I
nsize of current D, wherein size of current D can be relevant to the duty factor of dim signal Sdim and preset value, for example duty factor is 1/16, size of current D can equal 1/2 of upper current limit value, that is duty factor (1/16) is multiplied by upper current limit value again divided by preset value (1/8).And drive current I
1～I
noutput order can be sequentially or random sequence.
By this, no matter switch SW 1～SWn is according to duty factor conducting simultaneously or the conducting respectively in cycle T of light-modulating mode signal Sdim, its drive current I
1～I
nelectric current summation can be held in haply certain value, significantly reduce operating voltage V
cCtake out to carry and change, even except disappearing, with the audio-frequency noise and the electromagnetic interference that suppress therefore to produce.
Fig. 2 D is the drive unit of Fig. 2 A and the waveform schematic diagram of LED serial.Please refer to Fig. 2 A and Fig. 2 D, in the present embodiment, 200, hypothesis driven device drives LED serial 50_1 and 50_2, and the duty factor of received dim signal Sdim is 1/4.Now, switch SW 1 and SW2 are controlled by received control signal Scol conducting and ON time are respectively T/2 respectively.And current drives unit 250 is controlled by controls voltage Vcol adjustment drive current I
1～I
nsize of current D be the half (1/2) of upper current limit value H, wherein upper current limit value H can correspond to the high level V of voltage signal.By this, drive unit 200 can be realized 1/4 dimming effect, and size of current D can roughly be maintained at 1/2 of upper current limit value H, with the audio-frequency noise and the electromagnetic interference that suppress therefore to produce.
Fig. 2 E is the circuit diagram that the current control unit of Fig. 2 A couples light modulation detector.Please refer to Fig. 2 E, in the present embodiment, current control unit 270 comprises multiplexer 271, disperses delay cell 272 and duty factor to turn electric pressure converter 273.When the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is more than or equal to preset value, the light-modulating mode signal Smod of light modulation detector 260 can control dim signal Sdim that multiplexer 271 receives its input and export duty factor to by its first output and turn electric pressure converter 273, with the size of the duty factor adjustment control voltage Vcol according to dim signal Sdim.Drive current I is synchronously adjusted according to the size of controlling voltage Vcol in 250 of current drives unit
1～I
nsize of current.Meanwhile, owing to disperseing delay cell 272 not receive dim signal Sdim, thus disperse control signal Scol meeting control switch SW1～SWn conducting simultaneously of delay cell 272, to allow drive current I
1～I
nexport LED serial 50_1～50_n to simultaneously.
When the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is less than preset value, the light-modulating mode signal Smod of light modulation detector 260 can control the dim signal Sdim that multiplexer 271 receives its input and be exported to and disperseed delay cell 272 by its second output.Disperse delay cell 272 receiving after dim signal Sdim, control signal Scol meeting control switch SW1～SWn conducting respectively in a cycle of its generation, and the ON time of switch SW 1～SWn can be identical.Generally speaking, these control signals Scol can transmit pulse so that switch SW 1～SWn conducting in the time of difference in the time of difference.And but the ON time of switch SW 1～SWn can be separated mutually continued, that is the pulse meeting of actuating switch is in the output that continued of end points corresponding to these control signals Scol, and this continues the effect exported as pulse carried out to displacement.Wherein, the function of pulse displacement can complete by displacement buffer, that is the function that these control signals Scol transmits pulse in the time of difference can be carried out displacement having exported by multiple displacement buffer paired pulses.
Meanwhile, disperse delay cell 272 received dim signal Sdim can be sent to duty factor and turn electric pressure converter 273, and export a gain signal GN to turn electric pressure converter 273 to duty factor simultaneously.Duty factor turns electric pressure converter 273 and adjusts according to duty factor and the gain signal GN of dim signal Sdim the size of controlling voltage Vcol, synchronously to adjust drive current I
1～I
nsize of current.Wherein, gain signal GN can transmit gain number, and it can be drive current I that gain signal GN transmits gain number
1～I
nelectric current number, drive current I
1～I
nelectric current number taking 8 as example, gain signal GN transmit gain number be 8.For instance, in the time that the duty factor of dim signal Sdim is 1/16, drive current I
1～I
nsize of current should be 1/16 of upper current limit value, but again according to gain signal GN adjust after, drive current I
1～I
nsize of current be adjusted to 1/2 of upper current limit value, then coordinate drive current I
1～I
noutput time be the cycle 1/8, can reach 1/16 dimming effect.
It is worth mentioning that, disperse delay cell 272 in the time not receiving dim signal Sdim, the gain signal GN that it can output gain number is 1 or not output gain signal GN.In addition, duty factor turns electric pressure converter 273 in the time not receiving gain signal GN, produces corresponding control voltage Vcol according to the duty factor of dim signal Sdim.
Fig. 2 F is the circuit diagram that the duty factor of Fig. 2 E turns electric pressure converter.Please refer to Fig. 2 F, in the present embodiment, duty factor turns electric pressure converter 273 and comprises low-pass filter circuit LPF1 and analog multiplier ML1, and wherein low-pass filter circuit LPF1 can be made up of resistance R 1 and capacitor C 1, but does not limit other embodiment with this.Low-pass filter circuit LPF1 can be converted to a DC level by received dim signal Sdim, that is low-pass filter circuit LPF1 can export different DC level according to the difference of the duty factor of dim signal Sdim.Analog multiplier ML1 can be according to the DC level of gain signal GN amplification low pass circuit LPF1 output as controlling voltage Vcol.When the gain number transmitting as gain signal GN is 1, the level of controlling voltage Vcol can be same as the DC level of low-pass filter circuit LPF1 output.When the gain number transmitting as gain signal GN is 2, control the level of voltage Vcol can 2 times to the DC level of low-pass filter circuit LPF1 output, all the other are by that analogy.
Fig. 2 G is another circuit diagram that the duty factor of Fig. 2 E turns electric pressure converter.Please refer to Fig. 2 F and Fig. 2 G, its difference is multiplexer mux1.The DC level that multiplexer mux1 can determine low-pass filter circuit LPF1 output according to light-modulating mode signal Smod is for being sent to analog multiplier ML1 or directly output.In other words,, when the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is more than or equal to preset value, the DC level that directly output low-pass filter circuit LPF1 exports is as controlling voltage Vcol.When the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is less than preset value, the DC level of low-pass filter circuit LPF1 output is for being sent to analog multiplier ML1, using output after amplifying according to gain signal GN as control voltage Vcol.
Fig. 2 H is another circuit diagram that the current control unit of Fig. 2 A couples light modulation detector.Please refer to Fig. 2 E, Fig. 2 H, its difference is to disperse delay cell 274, and omits multiplexer 271.When the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is more than or equal to preset value, disperse the delay cell 274 can control switch SW1～SWn conducting simultaneously according to the control signal Scol of light-modulating mode signal Smod, and can output gain signal GN or the output gain number gain signal GN that is 1.Disperseing delay cell 274 not output gain signal GN in the situation that, duty factor turns electric pressure converter 273 and can produce and control voltage Vcol according to received dim signal Sdim.The gain signal GN that is 1 at dispersion delay cell 274 output gain numbers, duty factor turns electric pressure converter 273 and can produce and control voltage Vcol according to received dim signal Sdim and gain signal GN.
When the duty factor of carrying out light modulation and dim signal Sdim when drive unit 200 is less than preset value, disperse delay cell 272 to produce corresponding control signal Scol with control switch SW1～SWn conducting respectively in a cycle according to light-modulating mode signal Smod, and export corresponding drive current I
1～I
nthe gain signal GN of electric current number.Duty factor turns electric pressure converter 273 and can produce and control voltage Vcol according to received dim signal Sdim and gain signal GN.
Fig. 2 I is the circuit diagram again that the current control unit of Fig. 2 A couples light modulation detector.Please refer to Fig. 2 I, the drive current I of the present embodiment
1～I
nelectric current number taking 8 as example, that is preset value is 1/8.Light modulation detector 260 comprise low-pass filter circuit LPF2, analog-digital converter 261 (analog-to-digital converter, hereinafter to be referred as: ADC) with or door 262, wherein analog-digital converter 261 is taking the transducer of 4 bits as example.If the duty factor of dim signal Sdim is 1/4 o'clock, analog-digital converter 261 can be exported " 0100 ", shows to be exactly " 01000000 " with digital kenel.Preset value shows to be exactly " 00100000 " with digital kenel.
According to above-mentioned, as long as first three highest order unit occurs that " 1 " is greater than in preset value, therefore first three highest order unit can be produced to light-modulating mode signal Smod with exclusive disjunction at this.And " 01000000 " that analog-digital converter 261 is exported through or door 262 to first three highest order n ary operation after, can produce the light-modulating mode signal Smod of high logic level, represent that the duty factor of dim signal Sdim is greater than preset value.Then, " 01000000 " that multiplexer 271 is exported analog-digital converter 261 according to light-modulating mode signal Smod exports duty factor to and turns electric pressure converter 276, " 01000000 " of digital kenel is converted to simulation kenel output using as controlling voltage Vcol, wherein duty factor turn electric pressure converter 276 can comprise digital analog converter (digital-to-analog converter, hereinafter to be referred as: DAC) so that digital kenel " 01000000 " is converted to simulation kenel.And, disperse delay cell 275 in the time not receiving the output of analog-digital converter 261, the multiple control signal Scol of corresponding generation are with control switch SW1～SWn conducting simultaneously.
If the duty factor of dim signal Sdim is 1/16 o'clock, " 00010000 " that analog-digital converter 261 can output, and or lock 262 first three highest order unit is carried out after computing, can produce the light-modulating mode signal Smod of low logic level.Then " 00010000 " that, multiplexer 271 is exported analog-digital converter 261 according to light-modulating mode signal Smod exports duty factor to and turns electric pressure converter 276.Now, disperse 275 corresponding multiple control signal Scol of generation of delay cell with control switch SW1～SWn conducting respectively in a cycle.And, disperse delay cell 275 to adjust according to preset value " 00010000 " that analog-digital converter 261 is exported, be also about to " 00010000 " and be multiplied by for 8 (being equal to three bits that move to left) and become " 10000000 ".These " 10000000 " are exported as gain signal, and duty factor turns electric pressure converter 276 " 10000000 " is converted to simulation kenel output as controlling voltage Vcol.It should be noted that in the present embodiment, duty factor turns electric pressure converter 276 can not receive dim signal Sdim, to simplify the degree of difficulty of circuit design.
According to above-mentioned explanation, above-mentioned action can be converged whole for method is to be applied to drive unit 200.Fig. 3 A is the flow chart of driving method according to an embodiment of the invention.Please refer to Fig. 2 A and Fig. 3 A, drive unit 200 can receive dim signal Sdim, can detect drive unit 200 whether carrying out light modulation (step S301) according to dim signal Sdim.When drive unit 200 is in the time carrying out light modulation, uniform distribution drive current I
1～I
noutput time (step S302) in a cycle, and drive unit 200 can output driving current I
1～I
nto drive respectively LED serial 50_1～50_n.When drive unit 200 is not or not the time carrying out light modulation, finish this driving method.
Fig. 3 B is the flow chart of the driving method of another embodiment of the present invention.Please refer to Fig. 3 A and Fig. 3 B, its difference is step S311, S312 and S313.When drive unit is in the time carrying out light modulation, judge whether the duty factor of dim signal is less than preset value (step S311).In the time that the duty factor of dim signal is not less than preset value, output driving current simultaneously in a cycle, and adjust the size of current (step S312) of drive current according to dim signal.In the time that the duty factor of dim signal is less than preset value, the output time of uniform distribution drive current in a cycle, and adjust accordingly the size of current (step S313) of drive current.Wherein, step 312 and 313 can, with reference to the explanation of above-described embodiment, not repeated at this.
In sum, the Drive And Its Driving Method of the light-emitting diode of all embodiment of the present invention, when the duty factor of carrying out light modulation and dim signal when drive unit is less than preset value, the output time of the each drive current of uniform distribution in a cycle, and adjust accordingly the size of current of each drive current.When the duty factor of carrying out light modulation and dim signal when drive unit is more than or equal to preset value, output driving current simultaneously in the cycle, and adjust the size of drive current according to dim signal.By this, can suppress excessive caused audio-frequency noise and the electromagnetic interference of summation variation of drive current.
Finally it should be noted that: above embodiment is only in order to technical scheme of the present invention to be described but not be limited, although the present invention is had been described in detail with reference to preferred embodiment, those of ordinary skill in the art is to be understood that: it still can be modified or be equal to replacement technical scheme of the present invention, and these amendments or be equal to replacement and also can not make amended technical scheme depart from the spirit and scope of technical solution of the present invention.
Claims (21)
1. a driving method for light-emitting diode, is applicable to a drive unit, it is characterized in that, this driving method comprises:
Detect this drive unit and whether carry out light modulation;
Carry out light modulation if this drive unit is detected, judge whether the duty factor of a dim signal is less than a preset value;
In the time that this duty factor of this dim signal is more than or equal to this preset value, adjust the size of current of multiple drive currents, and in a cycle, export those drive currents, wherein the output time of those drive currents equals this cycle; And
In the time that this duty factor of this dim signal is less than this preset value, in this cycle, export respectively those drive currents, wherein the output time of those drive currents is less than this cycle.
2. the driving method of light-emitting diode according to claim 1, is characterized in that, more comprises:
In the time that the duty factor of this dim signal is more than or equal to this preset value, adjust those drive currents other size of current according to this dim signal.
3. the driving method of light-emitting diode according to claim 2, is characterized in that, in the time that the duty factor of this dim signal is more than or equal to this preset value, according to whole those drive currents of this duty factor other size of current of this dim signal.
4. the driving method of light-emitting diode according to claim 1, is characterized in that, more comprises:
In the time that the duty factor of this dim signal is less than this preset value, those drive currents other size of current is set and other output time in this cycle according to this dim signal.
5. the driving method of light-emitting diode according to claim 4, it is characterized in that, when this duty factor of this dim signal is less than this preset value, those drive currents other size of current is set and other output time in this cycle according to this duty factor of this dim signal.
6. the driving method of light-emitting diode according to claim 1, is characterized in that, more comprises:
No matter whether the output time of those drive currents equals this cycle, in the time that this dim signal is identical duty factor, the summation of those drive currents in this cycle is a fixed value.
7. a driving method for light-emitting diode, is applicable to a drive unit, it is characterized in that, this driving method comprises:
Receive a dim signal;
Detect this drive unit and whether carry out light modulation; And
Carry out light modulation if this drive unit is detected, adjust other size of current in multiple drive currents according to a duty factor of this dim signal, so that the summation of those drive currents in this cycle is proportional to this duty factor of this dim signal.
8. the driving method of light-emitting diode according to claim 7, is characterized in that, carries out light modulation if this drive unit is detected, and adjusts size of current and the output time of those drive currents according to this duty factor of this dim signal.
9. the driving method of light-emitting diode according to claim 7, is characterized in that, carries out light modulation if this drive unit is detected, and the output time of those drive currents equals this cycle, or is less than in this cycle at those drive currents.
10. the driving method of light-emitting diode according to claim 9, is characterized in that, those drive electric output time to be less than or equal to this cycle is whether to be less than a preset value according to this duty factor of this dim signal to decide.
The driving method of 11. light-emitting diodes according to claim 9, it is characterized in that, in the time that this dim signal is identical duty factor, no matter those drive electric output time to be less than or equal to this cycle, the summation of those drive currents in this cycle is maintained at a fixed value.
12. 1 kinds in order to drive the drive circuit of multiple light-emitting diodes, it is characterized in that, comprising:
Multiple switches, in order to couple those light-emitting diodes;
One light modulation detector, in order to receive a dim signal and to export a light-modulating mode signal according to this dim signal; And
One current control unit, in order to export multiple control signals according to this light-modulating mode signal and this dim signal, wherein those control signals are controlled respectively the conducting state of those switches.
13. drive circuits according to claim 12, it is characterized in that, more comprise a current drives unit, couple those switches and this current control unit, and this current control unit is more controlled voltage according to this light-modulating mode signal and this dim signal output one, and wherein multiple drive currents are adjusted to drive those light-emitting diodes in this current drives unit of this control voltage control.
14. drive circuits according to claim 12, is characterized in that, whether this light modulation detector carries out according to this dim signal detecting light modulation, and according to detecting result output light-modulating mode signal.
15. drive circuits according to claim 14, is characterized in that, whether this light modulation detector detecting is carried out according to a duty factor detecting light modulation of this dim signal.
16. drive circuits according to claim 14, it is characterized in that, whether the duty factor that this light modulation detector is more detected this dim signal is less than a preset value, and export this light-modulating mode signal to this current control unit so that the conducting state of those switches to be set.
17. drive circuits according to claim 16, it is characterized in that, whether this duty factor that this light modulation detector is detected this dim signal is less than this preset value, to export this light-modulating mode signal to this current control unit, so that this current control unit is adjusted those drive currents to drive those light-emitting diodes.
18. drive circuits according to claim 16, it is characterized in that, detect at this light modulation detector that light modulation is carried out and this duty factor of this dim signal is less than this preset value, this current control unit is exported those control signals to control the ON time of those switches in a cycle as impartial and divide equally this cycle.
19. drive circuits according to claim 16, it is characterized in that, detect at this light modulation detector that light modulation is carried out and this duty factor of this dim signal is more than or equal to this preset value, this current control unit is exported those control signals to control the ON time of those switches in a cycle for equaling this cycle.
20. drive circuits according to claim 17, it is characterized in that, detect at this light modulation detector that light modulation is carried out and this duty factor of this dim signal is less than this preset value, this current control unit is exported those control signals to control the conducting respectively in a cycle of each those switches.
21. drive circuits according to claim 17, it is characterized in that, no matter whether this duty factor of this dim signal is less than this preset value, those drive currents are to adjust so that the summation of those drive currents in this cycle is proportional to this duty factor of this dim signal.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201410203222.3A CN103957643B (en) | 2009-09-23 | 2009-09-23 | Driving device of light emitting diode and driving method thereof |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201410203222.3A CN103957643B (en) | 2009-09-23 | 2009-09-23 | Driving device of light emitting diode and driving method thereof |
| CN200910175152.4A CN102026439B (en) | 2009-09-23 | 2009-09-23 | Driving device and driving method for light emitting diode |
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| CN200910175152.4A Division CN102026439B (en) | 2009-09-23 | 2009-09-23 | Driving device and driving method for light emitting diode |
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| CN103957643B CN103957643B (en) | 2017-04-12 |
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| CN112219131A (en) * | 2018-06-06 | 2021-01-12 | 株式会社电装 | Optical distance measuring device and method thereof |
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| CN103957643B (en) | 2017-04-12 |
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