CN102026439B - Driving device and driving method for light emitting diode - Google Patents
Driving device and driving method for light emitting diode Download PDFInfo
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- CN102026439B CN102026439B CN200910175152.4A CN200910175152A CN102026439B CN 102026439 B CN102026439 B CN 102026439B CN 200910175152 A CN200910175152 A CN 200910175152A CN 102026439 B CN102026439 B CN 102026439B
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a driving device and a driving method for a light emitting diode. The driving method comprises the following steps of: when the driving device performs dimming and the duty factor of a dimming signal is less than a preset value, evenly distributing every driving current to output times in a cycle, and correspondingly adjusting the size of each driving current; and when the driving device performs dimming and the duty factor of the dimming signal is larger than or equal to the preset value, outputting the driving current simultaneously in the cycle and adjusting the size of the driving currents according to the dimming signal. By using the driving device and the driving method for the light emitting diode, audio frequency noise and electromagnetic interference caused by overlarge change of the sum 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 LCD) field such as backlight.
With light emitting diode drive device, one of conventional dimming mode is for utilizing PM (pulse-width modulation, hereinafter to be referred as the PWM) duty factor of technological adjustment pulse (duty), with this, adjust the equivalent current that output stage exports light-emitting diode to and adjust light-emitting diode luminance.Yet when using PM to carry out light modulation, the current switching action of its output stage output is 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 to the inductance in circuit great changes of magnetic field, and the electric capacity in circuit can, because excessive the causing of the change in voltage of moment vibrated (sharply vibrate) generation deformation (shape-changing) tempestuously, 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 comprised 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 operating voltage V of coordination standard not
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 carry out the switching of switch according to dim signal simultaneously, with this, carries out the action of light modulation.
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.Yet, when using PM to carry out light modulation, the load current i that the switching action of switch S 1～Sn causes
1～i
nvariation.Above-mentioned load current i
1～i
nvariation can make operating voltage V
cChave to take out greatly to carry to change, cause the operating voltage V of electric pressure converter 110 outputs
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 therefore vibration and produce deformation tempestuously produces audio-frequency noise because transient voltage changes excessive to allow electric capacity of voltage regulation in electric pressure converter 110.In addition,, with drive unit 100, when 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: receive dim signal; When drive unit carries out light modulation according to dim signal, the output time of a plurality of drive currents of uniform distribution in the cycle; Export each drive current to drive respectively a plurality of light-emitting diodes.The step of the output time of each drive current of above-mentioned uniform distribution in the cycle comprises: when the duty factor of carrying out light modulation and dim signal at drive unit is less than preset value, the output time of each drive current of uniform distribution in the cycle, and adjust accordingly the size of current of each drive current.
The present invention proposes a kind of driving method of light-emitting diode, is applicable to drive unit, and drive unit receives dim signal, and exports respectively a plurality of drive currents to drive respectively a plurality of light-emitting diodes, and this driving method comprises whether detecting drive unit carries out light modulation; When the duty factor of carrying out light modulation and dim signal when drive unit is less than a preset value, the output time of each drive current of uniform distribution in the 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, in the cycle, exports these drive currents simultaneously, and according to dim signal, adjust the size of current of each drive current.
The present invention proposes a kind of drive unit of light-emitting diode, and it comprises current drives unit, a plurality of switch, light modulation detector and current control unit.A plurality of drive currents are exported to drive respectively a plurality of light-emitting diodes in current drives unit.Each switch is respectively coupled between current drives unit and described light-emitting diode, in order to control each drive current, whether exports described light-emitting diode to.Light modulation detector receives dim signal, according to dim signal detecting drive unit, whether carries out light modulation and exports accordingly light-modulating mode signal.Current control unit couples light modulation detector and these switches.When drive unit carries out light modulation, according to these switches of light-modulating mode signal controlling, the ON time in a cycle is impartial and divides equally this cycle current control unit.
The present invention proposes a kind of drive unit of light-emitting diode, and it comprises current drives unit, a plurality of switch, light modulation detector and current control unit.A plurality of drive currents are exported to drive respectively a plurality of light-emitting diodes in current drives unit.Each switch is respectively coupled between current drives unit and described light-emitting diode, in order to control a little drive currents, whether exports described light-emitting diode to.Light modulation detector receives dim signal, and whether the duty factor of whether carrying out light modulation and dim signal according to dim signal detecting drive unit is less than preset value, and exports accordingly light-modulating mode signal.Current control unit couples light modulation detector, these switches and current drives unit.When the duty factor of carrying out light modulation and dim signal when drive unit is less than preset value, the ON time according to a little switches of light-modulating mode signal controlling in the cycle is for impartial and divide equally this cycle, and controls the size of current of a little drive currents of current drives unit adjustment.When the duty factor of carrying out light modulation and dim signal when drive unit is more than or equal to preset value, according to a little switches of light-modulating mode signal controlling, in the cycle, keep conducting simultaneously, and according to dim signal, control the size of current of a little drive currents of current drives unit adjustment.
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 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 according to dim signal, adjust the size of drive current.Excessive caused audio-frequency noise and the electromagnetic interference of summation change that can suppress by this, 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.
Accompanying drawing explanation
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 interrupteur 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 a plurality of 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 control current drives unit 250 adjustment drive current I by controlling voltage Vcol
1～I
nsize.
Electric pressure converter 210 receives supply voltage V
dD, and produce and supply voltage V according to the adjustment signal of conversion loop control unit 220 outputs
dDthe operating voltage V of coordination standard not
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 interrupteur SW 1～SWn and current drives unit 250 respectively, and by drive current I
1～I
ndrive LED serial 50_1～50_n luminous.
When 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.When 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 be take the ON time of control switch SW1～SWn in a cycle as equal or impartial, and by control voltage Vcol, controls current drives unit 250 and adjust drive current I
1～I
nsize, wherein current drives unit 250 can be comprised of a plurality of 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 a plurality of 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 interrupteur 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 for cycle T be divided by drive current I
1～I
nnumber n, for example the number n of 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 a plurality of 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, for example the quantity of 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 duty factor and the preset value of dim signal Sdim, 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 interrupteur 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 certain value haply, significantly reduce operating voltage V
cCtake out and carry to change, even except disappearing, with audio-frequency noise and the electromagnetic interference that suppresses so 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, interrupteur 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 upper current limit value H half (1/2), 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 audio-frequency noise and the electromagnetic interference that suppresses so 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 by its first output, export duty factor to and turn electric pressure converter 273, controls the size of voltage Vcol with the duty factor adjustment 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 after receiving dim signal Sdim, the control signal Scol of its generation meeting control switch SW1～SWn conducting respectively in a cycle, and the ON time of interrupteur SW 1～SWn can be identical.Generally speaking, these control signals Scol can transmit pulse so that interrupteur SW 1～SWn conducting in the time of difference in the time of difference.And but the ON time of interrupteur 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 a plurality of 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 the size that electric pressure converter 273 is controlled voltage Vcol according to duty factor and the gain signal GN adjustment of dim signal Sdim, 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 take 8 as example, gain signal GN transmit gain number be 8.For instance, when 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 after adjusting according to gain signal GN again, 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 when 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 when not receiving gain signal GN, and the duty factor according to dim signal Sdim produces corresponding control voltage Vcol.
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 comprised of resistance R 1 and capacitor C 1, but with this, does not limit other embodiment.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.The DC level that analog multiplier ML1 can export according to gain signal GN amplification low pass circuit LPF1 is 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 according to gain signal GN, amplify after output 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.In the situation that disperse the gain signal GN that delay cell 274 output gain numbers are 1, 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 take 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 to take the transducer of 4 bits be example to analog-digital converter 261.If the duty factor of dim signal Sdim is 1/4 o'clock, analog-digital converter 261 can be exported " 0100 ", with digital kenel, shows to be exactly " 0,100 0000 ".Preset value shows to be exactly " 0,010 0000 " with digital kenel.
According to above-mentioned, at this, 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.And " 0,100 0000 " of analog-digital converter 261 output through or 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, multiplexer 271 exports duty factor according to light-modulating mode signal Smod to by " 0,100 0000 " of analog-digital converter 261 outputs and turns electric pressure converter 276, " 0,100 0000 " of digital kenel is converted to the output of simulation kenel, 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 " 0,100 0000 " is converted to simulation kenel.And, disperse delay cell 275 when not receiving the output of analog-digital converter 261, a plurality of 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, " 0,001 0000 " 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 " 0,001 0000 " 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 a plurality of control signal Scol of generation of delay cell with control switch SW1～SWn conducting respectively in a cycle.And, disperse delay cell 275 according to preset value, to adjust " 0,001 0000 " of analog-digital converter 261 outputs, be also about to " 0,001 0000 " and be multiplied by for 8 (being equal to three bits that move to left) and become " 1,000 0000 ".Using these " 100 00000 " output as gain signal, duty factor turns electric pressure converter 276 " 1,000 0000 " is converted to the output of simulation kenel as control 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 when carrying out light modulation, uniform distribution drive current I
1～I
noutput time in a cycle (step S302), 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 when 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 when carrying out light modulation, judge whether the duty factor of dim signal is less than preset value (step S311).When the duty factor of dim signal is not less than preset value, output driving current simultaneously in a cycle, and according to dim signal, adjust the size of current (step S312) of drive current.When 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 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 according to dim signal, adjust the size of drive current.Excessive caused audio-frequency noise and the electromagnetic interference of summation change that can suppress by this, 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 modifications 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 (20)
1. a driving method for light-emitting diode, is applicable to a drive unit, and described driving method comprises:
Receive a dim signal;
When described drive unit carries out light modulation according to described dim signal, the output time of a plurality of drive currents of uniform distribution in a cycle, and the described dim signal of foundation is adjusted the size of current of described a plurality of drive currents, no matter wherein whether the duty factor of described dim signal is more than or equal to or is less than a preset value, the size of current of described a plurality of drive currents is relevant to the duty factor of described dim signal, and when the duty factor of described dim signal is more than or equal to described preset value, in the described cycle, export described a plurality of drive current simultaneously, and the described dim signal of foundation is adjusted the size of current of described a plurality of drive currents, when the duty factor of described dim signal is less than described preset value, distributing the output time of described a plurality of drive current in the described cycle is non-output simultaneously, and adjust accordingly the size of current of described a plurality of drive currents, and
Export described a plurality of drive current to drive respectively a plurality of light-emitting diodes.
2. the driving method of light-emitting diode according to claim 1, wherein described in uniform distribution, the step of the output time of a plurality of drive currents in the described cycle comprises:
When the duty factor of carrying out light modulation and described dim signal at described drive unit is less than described preset value, the size of current of described a plurality of drive currents equals duty factor that a upper current limit value is multiplied by described dim signal again divided by described preset value.
3. the driving method of light-emitting diode according to claim 2, also comprises:
When the duty factor of carrying out light modulation and described dim signal at described drive unit is more than or equal to described preset value, the size of current of described a plurality of drive currents equals the duty factor that described upper current limit value is multiplied by described dim signal.
4. the driving method of light-emitting diode according to claim 1, wherein said preset value is the ratio of the number of described cycle and described a plurality of drive currents.
5. the driving method of light-emitting diode according to claim 1, wherein said a plurality of drive currents are sequentially output in turn.
6. the driving method of light-emitting diode according to claim 1, wherein said a plurality of drive currents are that random sequence is exported in turn.
7. a drive unit for light-emitting diode, comprising:
One current drives unit, in order to export a plurality of drive currents to drive respectively a plurality of light-emitting diodes;
A plurality of switches, are respectively coupled between described current drives unit and described a plurality of light-emitting diode, in order to control described a plurality of drive current, whether export described a plurality of light-emitting diode to;
One light modulation detector, receives a dim signal, detects described drive unit whether carry out light modulation and export accordingly a light-modulating mode signal according to described dim signal; And
One current control unit, couple described light modulation detector and described a plurality of switch, when described drive unit carries out light modulation, according to the ON time of a plurality of switches in a cycle described in described light-modulating mode signal controlling, be impartial and divide equally the described cycle, and described current control unit also couples described current drives unit to control the size of current of described a plurality of drive currents, no matter wherein whether the duty factor of described dim signal is more than or equal to or is less than a preset value, the size of current of described a plurality of drive currents is relevant to the duty factor of described dim signal, and when the duty factor of described dim signal is more than or equal to described preset value, according to a plurality of switches described in described light-modulating mode signal controlling, in the described cycle, keep conducting simultaneously, and control described current drives unit and according to described dim signal, adjust the size of current of described a plurality of drive currents, when the duty factor of described dim signal is less than described preset value, current control unit is non-while conducting and divides equally the described cycle according to the ON time of a plurality of switches in the described cycle described in described light-modulating mode signal controlling, and control the size of current that described a plurality of drive currents are adjusted in described current drives unit.
8. the drive unit of light-emitting diode according to claim 7, whether wherein said light modulation detector is also less than described preset value according to the duty factor of described dim signal and produces described light-modulating mode signal.
9. the drive unit of light-emitting diode according to claim 8, wherein said preset value is the ratio of the electric current number of described cycle and described a plurality of drive currents.
10. the drive unit of light-emitting diode according to claim 8, when wherein said current control unit is less than described preset value in order to carry out the duty factor of light modulation and described dim signal when described drive unit, controls described current drives unit and adjust the size of current of described a plurality of drive currents and equal duty factor that a upper current limit value is multiplied by described dim signal again divided by described preset value; When the duty factor of carrying out light modulation and described dim signal when described drive unit is more than or equal to described preset value, controls the size of current of adjusting described a plurality of drive currents according to described dim signal in described current drives unit and equal the duty factor that described upper current limit value is multiplied by described dim signal.
The drive unit of 11. light-emitting diodes according to claim 7, wherein said current control unit comprises:
One multiplexer, couple described light modulation detector to receive described light-modulating mode signal, the input of described multiplexer receives described dim signal, according to dim signal described in described light-modulating mode signal deciding, by the first output of described multiplexer or the second output of described multiplexer, is exported;
One disperses delay cell, couple the first output and described a plurality of switch of described multiplexer, when receiving described dim signal, described dispersion delay cell is controlled the ON time of described a plurality of switches in the described cycle for equalization and is divided equally the described cycle, and exports described dim signal and a gain signal; When not receiving described dim signal, described dispersion delay cell is controlled described a plurality of switches and in the described cycle, is kept conducting simultaneously; And
One duty factor turns electric pressure converter, couple the second output of described multiplexer, described dispersion delay cell and described current drives unit, when not receiving described dim signal, described duty factor turns electric pressure converter and according to described dim signal, adjusts the size of current of described drive current; When receiving described dim signal and described gain signal, described duty factor turns electric pressure converter and according to described dim signal and described gain signal, adjusts the size of current of described drive current.
The drive unit of 12. light-emitting diodes according to claim 11, wherein said duty factor turns electric pressure converter and comprises:
One low pass filter, couples described multiplexer and described dispersion delay cell;
One analog multiplier, couples described low pass filter, described dispersion delay cell and described current drives unit, in order to adjust the output voltage of received described low pass filter according to described gain signal, and exports described current drives unit to.
The drive unit of 13. light-emitting diodes according to claim 10, wherein said current drives unit comprises:
A plurality of voltage-controlled current sources, couple described current control unit jointly.
The driving method of 14. 1 kinds of light-emitting diodes, is applicable to a drive unit, and described drive unit receives a dim signal, and exports respectively a plurality of drive currents to drive respectively a plurality of light-emitting diodes, and described driving method comprises:
Detect described drive unit and whether carry out light modulation;
When the duty factor of carrying out light modulation and described dim signal when described drive unit is less than a preset value, distributing the output time of described a plurality of drive current in the cycle is non-output simultaneously, and adjusts accordingly the size of current of described a plurality of drive currents; And
When the duty factor of carrying out light modulation and described dim signal when described drive unit is more than or equal to described preset value, in the described cycle, exports described a plurality of drive current simultaneously, and according to described dim signal, adjust the size of current of described a plurality of drive currents,
No matter wherein whether the duty factor of described dim signal is more than or equal to or is less than described preset value, the size of current of described a plurality of drive currents is relevant to the duty factor of described dim signal, and described preset value is the ratio of the number of described cycle and described a plurality of drive currents.
The driving method of 15. light-emitting diodes according to claim 14, wherein said a plurality of drive currents are sequentially output in turn.
The driving method of 16. light-emitting diodes according to claim 14, wherein said a plurality of drive currents are that random sequence is exported in turn.
The drive unit of 17. 1 kinds of light-emitting diodes, comprising:
One current drives unit, in order to export a plurality of drive currents to drive respectively a plurality of light-emitting diodes;
A plurality of switches, are respectively coupled between described current drives unit and described light-emitting diode, in order to control described a plurality of drive current, whether export described light-emitting diode to;
One light modulation detector, receives a dim signal, detects the duty factor whether described drive unit carry out light modulation and described dim signal and whether is less than a preset value, and export accordingly a light-modulating mode signal according to described dim signal; And
One current control unit, couple described light modulation detector, described a plurality of switch and described current drives unit, when the duty factor of carrying out light modulation and described dim signal when described drive unit is less than described preset value, according to the ON time of a plurality of switches in a cycle described in described light-modulating mode signal controlling, be non-while conducting and divide equally the described cycle, and control the size of current that described a plurality of drive currents are adjusted in described current drives unit, when the duty factor of carrying out light modulation and described dim signal when described drive unit is more than or equal to described preset value, according to a plurality of switches described in described light-modulating mode signal controlling, in the described cycle, keep conducting simultaneously, and control according to described dim signal the size of current that described a plurality of drive currents are adjusted in described current drives unit, no matter wherein whether the duty factor of described dim signal is more than or equal to or is less than described preset value, the size of current of described a plurality of drive currents is relevant to the duty factor of described dim signal, and described preset value is the ratio of the number of described cycle and described a plurality of drive currents.
The drive unit of 18. light-emitting diodes according to claim 17, wherein said current control unit comprises:
One multiplexer, couple described light modulation detector to receive described light-modulating mode signal, the input of described multiplexer receives described dim signal, according to dim signal described in described light-modulating mode signal deciding, by the first output of described multiplexer or the second output of described multiplexer, is exported;
One disperses delay cell, couple the first output and described a plurality of switch of described multiplexer, when receiving described dim signal, control the ON time of described a plurality of switch in the described cycle for impartial, and export described dim signal and a gain signal, when not receiving described dim signal, control described a plurality of switch and in the described cycle, keep conducting simultaneously; And
One duty factor turns electric pressure converter, couple the second output of described multiplexer, described dispersion delay cell and described current drives unit, when not receiving described dim signal, according to described dim signal, adjust the size of current of described drive current, when receiving described dim signal and described gain signal, according to described dim signal and described gain signal, adjust the size of current of described drive current.
The drive unit of 19. light-emitting diodes according to claim 18, wherein said duty factor turns electric pressure converter and comprises:
One low pass filter, couples described multiplexer and described dispersion delay cell;
One analog multiplier, couples described low pass filter, described dispersion delay cell and described current drives unit, in order to adjust the output voltage of received described low pass filter according to described gain signal, and exports described current drives unit to.
The drive unit of 20. light-emitting diodes according to claim 18, wherein said current drives unit comprises:
A plurality of voltage-controlled current sources, jointly couple described duty factor and turn electric pressure converter.
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| CN200910175152.4A CN102026439B (en) | 2009-09-23 | 2009-09-23 | Driving device and driving method for light emitting diode |
| CN201410203222.3A CN103957643B (en) | 2009-09-23 | 2009-09-23 | Driving device of light emitting diode and driving method thereof |
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| CN200910175152.4A CN102026439B (en) | 2009-09-23 | 2009-09-23 | Driving device and driving method for light emitting diode |
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| TWI483652B (en) * | 2012-12-21 | 2015-05-01 | Upi Semiconductor Corp | Led driving circuit and protection method thereof |
| CN103440848B (en) * | 2013-09-02 | 2016-01-20 | 深圳市华星光电技术有限公司 | Backlight drive circuit |
| CN104902610B (en) * | 2014-03-04 | 2017-07-21 | 通嘉科技股份有限公司 | Dimming controlling method and related backlight controller |
| CN109041340B (en) * | 2018-08-01 | 2019-08-27 | 广州市浩洋电子股份有限公司 | A kind of electric current when LED multi-path dims distributes control method |
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| CN1515037A (en) * | 2002-05-07 | 2004-07-21 | ��ķ�ɷ�����˾ | Light emitting element driving device and electronic apparatus having light emitting element |
| CN101122697A (en) * | 2007-09-04 | 2008-02-13 | 友达光电股份有限公司 | Double sided grid drive type liquid crystal display and its driving method |
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| CN1515037A (en) * | 2002-05-07 | 2004-07-21 | ��ķ�ɷ�����˾ | Light emitting element driving device and electronic apparatus having light emitting element |
| CN101179883A (en) * | 2006-11-06 | 2008-05-14 | 台湾类比科技股份有限公司 | Light modulation method of LED |
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