CN103957643B - Light-emitting diode driving device and driving method thereof - Google Patents

Abstract

The invention discloses a driving device and a driving method of a light emitting diode. In the driving method, whether the driving device performs dimming is detected. If the driving device is detected to perform dimming, whether the duty factor of a dimming signal is smaller than a preset value is judged. When the duty cycle of the dimming signal is larger than or equal to a preset value, the current magnitude of a plurality of driving currents is adjusted, and the driving currents are output in a period, wherein the output time of the driving currents is equal to the period. And when the duty cycle of the dimming signal is smaller than a preset value, the driving currents are respectively output in a period, wherein the output time of the driving currents is smaller than the period. Thus, audio noise and electromagnetic interference caused by excessive variation of the total sum of the driving currents can be suppressed.

Description

Light-emitting diode driving device and driving method thereof

technical field

The invention relates to a driving method, and in particular to a driving device of a light emitting diode and a driving method thereof.

Background technique

Light Emitting Diodes (hereinafter referred to as LEDs) are small in size, power-saving and durable, and with the maturity of the manufacturing process, the price has dropped. Recently, products using light emitting diodes as light sources have become more and more popular. In addition, light-emitting diodes have a low working voltage (only 1.5-3V), can actively emit light and have a certain brightness, and the brightness can be adjusted by voltage or current. Diodes are widely used in a variety of terminal equipment, from automotive headlights, traffic lights, text displays, billboards and large-screen video displays, to general and architectural lighting and Liquid Crystal Display (hereinafter referred to as: LCD) backlighting and other fields.

As far as the light-emitting diode driving device is concerned, one of the commonly used dimming methods is to use pulse-width modulation (hereinafter referred to as: PWM) technology to adjust the duty factor of the pulse, so as to adjust the output stage output to the light-emitting diode. The equivalent current to adjust the brightness of the LED. However, when using pulse modulation for dimming, the current switching action of its output stage output is like a switch. The current switching action will greatly change the voltage of the output stage, resulting in the generation of excessive ripple in the voltage. At the same time, excessive ripple will cause a huge change in the magnetic field of the inductance in the circuit, and the capacitance in the circuit will cause sharp vibration (sharply vibrate) and deformation (shape-changing) due to the excessive instantaneous voltage change, so Generate audio noise.

FIG. 1A is a system schematic diagram of a conventional LED driving device. Referring to FIG. 1A , the driving device 100 includes a voltage converter 110 , a conversion loop controller 120 , an amplifier 130 , a voltage selector 140 and a current driving unit 150 composed of a plurality of current driving elements. The voltage converter 110 receives the power voltage V _DD , and the voltage converter 110 generates an operating voltage V _CC at a level different from the power voltage V _DD according to the output of the conversion loop controller 120 . The positive input terminal of the amplifier 130 receives the reference voltage Vref, and the negative input terminal receives the voltage output from the voltage selector 140, and outputs the voltage accordingly to control the conversion loop controller 120, wherein the reference voltage Vref is a fixed value. The voltage selector 140 is used to select and output the voltage of a negative terminal of the LED series 50_1˜50_n. The positive terminals of the LED series 50_1-50_n receive the operating voltage V _CC , the negative terminals of the LED series 50_1-50_n are respectively coupled to the current driving unit 150 through the switches S1-Sn, and the load currents _{i 1} -in pass through The light-emitting diode series 50_1-50_n are driven to emit light, and the switches S1-Sn are switched according to the dimming signal at the same time, so as to perform a dimming operation.

FIG. 1B is a timing diagram of the driving current in FIG. 1A . Referring to FIG. 1A and FIG. 1B , in the LED driving device 100 , the pulse modulation technique is commonly used to adjust the time t ₁ of supplying the load currents _{i 1} -in to adjust the brightness of the LEDs. In other words, in the fixed period T, the longer the time _t1 is, the higher the brightness of the LED will be; conversely, the shorter the time _t1 , the lower the brightness of the LED. However, when the pulse modulation is used for dimming, the changes of the load currents _{i 1} -in are caused by the switching actions of the switches S1 -Sn. The change of the above load currents _{i 1} ˜in will cause the operating voltage V _CC to have a large load variation, resulting in the generation of excessive ripple in the operating voltage V _CC output by the voltage converter 110 . At the same time, the input current of the voltage converter 110 will also have a huge instantaneous change, which not only causes the inductance in the voltage converter 110 to cause a huge magnetic field change, but also causes the voltage stabilizing capacitor in the voltage converter 110 to change too much due to the instantaneous voltage change. However, it vibrates violently and deforms, thus generating audio noise. In addition, as far as the driving device 100 is concerned, when performing dimming, its switches S1-Sn will be switched at the same time, so as to perform the switching action of the load current _{i 1} -in at the same time, and the current switching action will cause serious electromagnetic interference ( Electromagnetic Disturbance, hereinafter referred to as: EMI).

Contents of the invention

The invention provides a driving device of a light emitting diode and a driving method thereof, which can suppress audio noise and electromagnetic interference.

The invention provides a driving method of a light emitting diode, which is suitable for a driving device. The driving method includes: detecting whether the driving device performs dimming; if the driving device is detected to perform dimming, judging whether the duty cycle of a dimming signal is smaller than a preset value; when the duty cycle of the dimming signal is greater than When equal to the preset value, adjust the current magnitude of multiple driving currents, and output these driving currents in one cycle, wherein the output time of these driving currents is equal to the cycle; and, when the duty factor of the dimming signal is less than the preset value , respectively output these driving currents in a period, wherein the output time of these driving currents is shorter than the period.

The invention provides a driving method of a light emitting diode, which is suitable for a driving device. The driving method includes: receiving a dimming signal; detecting whether the driving device performs dimming; and, if the driving device is detected to perform dimming, adjusting individual currents among the plurality of driving currents according to a duty cycle of the dimming signal size, so that the sum of these drive currents in a period is proportional to the duty cycle of the dimming signal.

The invention proposes a driving circuit for driving a plurality of LEDs, including a plurality of switches, a dimming detector, and a current control unit. The switches are used to couple the LEDs. The dimming detector is used for receiving a dimming signal and outputting a dimming mode signal according to the dimming signal. The current control unit is used for outputting a plurality of control signals according to the dimming mode signal and the dimming signal, wherein the control signals respectively control the conduction states of the switches.

Based on the above, the driving device of the light emitting diode and the driving method thereof of the present invention, when the driving device performs dimming and the duty cycle of the dimming signal is less than a preset value, the output time of each driving current in one cycle is evenly distributed, And correspondingly adjust the current magnitude of each driving current. When the driving device performs dimming and the duty cycle of the dimming signal is greater than or equal to a preset value, the driving current is simultaneously output in a cycle, and the magnitude of the driving current is adjusted according to the dimming signal. In this way, the audio noise and electromagnetic interference caused by the excessive variation of the sum of the driving currents can be suppressed.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail with reference to the accompanying drawings.

Description of drawings

FIG. 1A is a system schematic diagram of a conventional LED driving device.

FIG. 1B is a timing diagram of the driving current in FIG. 1A .

FIG. 2A is a schematic circuit diagram of a driving device according to an embodiment of the present invention.

FIG. 2B is a schematic diagram of a current waveform of the LED string in FIG. 2A .

FIG. 2C is a schematic diagram of another current waveform of the LED string in FIG. 2A .

FIG. 2D is a schematic waveform diagram of the driving device and LED series in FIG. 2A .

FIG. 2E is a schematic circuit diagram of the current control unit in FIG. 2A coupled to the dimming detector.

FIG. 2F is a schematic circuit diagram of the duty factor-to-voltage converter shown in FIG. 2E .

FIG. 2G is another schematic circuit diagram of the duty factor-to-voltage converter shown in FIG. 2E .

FIG. 2H is another schematic circuit diagram of the current control unit in FIG. 2A coupled to the dimming detector.

FIG. 2I is another schematic circuit diagram of the current control unit in FIG. 2A coupled to the dimming detector.

FIG. 3A is a flowchart of a driving method according to an embodiment of the invention.

FIG. 3B is a flowchart of a driving method according to another embodiment of the present invention.

Description of main component symbols:

50_1～50_n: Light-emitting diode series 100, 200: Driving device

110, 210: voltage converter 120, 220: conversion loop controller

130, 230: amplifier 140, 240: voltage selector

150, 250: current drive unit 260: dimming detector

261: Analog-to-digital converter 262: OR gate

270: current control unit 271, mux1: multiplexer

272, 274, 275: Decentralized delay unit 273, 276: Duty cycle to voltage converter

D: current size S1～Sn, SW1～SWn: switch

Scol: control signal Smod: dimming mode signal

Sdim: Dimming signal t ₁ , t ₂ : Time

T: period GN: gain signal

i ₁ ～i _n : load current _VR : 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: Resistor C1, C2: Capacitor

ML1: Analog multiplier S301, S302, S311～S313: According to this

The steps of the driving method of the various embodiments of the invention

detailed description

FIG. 2A is a schematic circuit diagram of a driving device according to an embodiment of the present invention. 2A, the driving device 200 includes a voltage converter 210, a conversion loop controller 220, an amplifier 230, a voltage selector 240, a current driving unit 250, a dimming detector 260, a current control unit 270 and switches SW1˜SWn. The dimming detector 260 receives the dimming signal Sdim, detects whether the driving device 200 performs dimming according to the dimming signal Sdim, and outputs a dimming mode signal Smod accordingly. The current control unit 270 outputs a plurality of control signals Scol and a control voltage Vcol according to the dimming mode signal Smod and the dimming signal Sdim, so as to use these control signals Scol to respectively control whether the switches SW1-SWn are turned on or not, and control the current through the control voltage Vcol The driving unit 250 adjusts the magnitude of the driving currents I _{1 -In} .

The voltage converter 210 receives the power supply voltage V _DD , and generates an operating voltage V _CC at a level different from the power supply voltage V _DD according to the adjustment signal output by the conversion loop controller 220 . The conversion loop controller 220 generates an adjustment signal according to the received voltage. The positive input terminal of the amplifier 230 receives the reference voltage V _R , and the negative input terminal receives the voltage output from the voltage selector 240 , and outputs the voltage to the switching loop controller 220 accordingly, wherein the reference voltage Vref can be a fixed value. The voltage selector 240 is used to select and output the voltage of a negative terminal of the LED series 50_1˜50_n. The positive terminals of the LED series 50_1-50_n receive the operating voltage V _CC , the negative terminals of the LED series 50_1-50_n are respectively coupled to the current driving unit 250 through the switches SW1-SWn, and the driving currents I ₁ -I _n are passed. Driving the LED series 50_1˜50_n to emit light.

When the duty factor of the dimming signal Sdim is 100%, it means that the driving device 200 will not perform dimming. At this time, the current control unit 270 will generate the control signal Scol according to the dimming mode signal Smod to control the switches SW1-SWn to be turned on simultaneously in one cycle, and adjust and control the current magnitude D of the driving currents _I1 -In through the control voltage _Vcol as follows: current upper limit. When the duty factor of the dimming signal Sdim is not 100%, it means that the driving device 200 will perform dimming. At this time, the current control unit 270 also controls the conduction time of the switches SW1-SWn in one cycle to be equal or equal according to the control signal Scol generated by the dimming mode signal Smod, and controls the current drive unit 250 to adjust the driving through the control voltage Vcol. The magnitude of the currents I _{1 -In} , wherein the current driving unit 250 may be composed of a plurality of voltage-controlled current sources to simultaneously adjust the magnitude of the driving currents I ₁ -In according to the control voltage _Vcol . It is worth mentioning that the relationship between the duty cycle of the dimming signal Sdim and whether the driving device 200 performs dimming is for illustration and may vary according to actual needs.

To further illustrate the dimming operation of the driving device 200 , FIG. 2B is a schematic diagram of the current waveform of the LED string in FIG. 2A . Please refer to FIG. 2A and FIG. 2B. When the driving device 200 performs dimming and the duty factor of the dimming signal Sdim is greater than or equal to a preset value, the current control unit 270 generates a plurality of The control signal Scol and the control voltage Vcol. These control signals Scol control the switches SW1˜SWn to be turned on simultaneously in the period T, so as to simultaneously provide driving currents I ₁ ˜I _n to the LED strings 50_1˜50_n. The currents of the LED strings 50_1 - 50_n are DC rather than pulsed because the switches SW1 - SWn are turned on. Moreover, the current driving unit 250 adjusts the current magnitude D of the driving currents I ₁ -In according to the control voltage _Vcol , where the current magnitude D is related to the duty factor of the dimming signal Sdim, for example, the duty factor is 1/8, then the current The size D will be equal to 1/8 of the current upper limit value. The above preset value can be the period T divided by the number _n of the driving currents I ₁ -In, for example, the number n of the driving currents is 8, then the preset value is 1/8 of the period (ie T/8).

FIG. 2C is a schematic diagram of another current waveform of the LED string in FIG. 2A . 2A and 2C, when the driving device 200 performs dimming and the duty factor of the dimming signal Sdim is smaller than a preset value, the current control unit 270 also generates multiple control signals according to the dimming mode signal Smod and the dimming signal Sdim. Signal Scol and control voltage Vcol. These control signals Scol control the conduction time _t2 of the switches SW1˜SWn in the period T to be equal, so as to respectively output the drive currents I _{1˜I n to} the LED strings 50_1˜50_n. For example, the number of switches is 8, then The conduction time _t2 is 1/8 period. The current driving unit 250 adjusts the current magnitude D of the driving currents I ₁ -In according to the control voltage _Vcol , where the current magnitude D is related to the duty factor and the preset value of the dimming signal Sdim, for example, the duty factor is 1/16, Then the current magnitude D is equal to 1/2 of the current upper limit, that is, the duty factor (ie 1/16) is divided by the preset value (ie 1/8) and then multiplied by the current upper limit. The output order of the driving currents I _{1 -In} can be sequential or random.

In this way, regardless of whether the switches SW1˜SWn are simultaneously turned on or turned on separately in the period T according to the duty cycle of the dimming mode signal Sdim, the sum of the driving currents I _{1 ˜In} is generally maintained at a certain value, greatly Reduce, or even eliminate, the pumping variation of the operating voltage V _CC to suppress the resulting audio noise and electromagnetic interference.

FIG. 2D is a schematic waveform diagram of the driving device and LED series in FIG. 2A . Referring to FIG. 2A and FIG. 2D , in this embodiment, it is assumed that the driving device 200 only drives the LED strings 50_1 and 50_2 , and the received duty factor of the dimming signal Sdim is 1/4. At this time, the switches SW1 and SW2 are respectively turned on by the received control signal Scol and the turn-on time is T/2 respectively. Moreover, the current driving unit 250 is controlled by the control voltage _Vcol to adjust the current magnitude D of the driving currents I ₁ -In to be half (ie, 1/2) of the current upper limit H, wherein the current upper limit H can correspond to the voltage signal The high level of V. In this way, the driving device 200 can achieve a dimming effect of 1/4, and the current value D is maintained at approximately 1/2 of the upper limit value H of the current, so as to suppress audio noise and electromagnetic interference generated thereby.

FIG. 2E is a schematic circuit diagram of the current control unit in FIG. 2A coupled to the dimming detector. Please refer to FIG. 2E , in this embodiment, the current control unit 270 includes a multiplexer 271 , a distributed delay unit 272 and a duty factor to voltage converter 273 . When the driving device 200 performs dimming and the duty factor of the dimming signal Sdim is greater than or equal to a preset value, the dimming mode signal Smod of the dimming detector 260 will control the multiplexer 271 to receive the The dimming signal Sdim is output to the duty factor to voltage converter 273 through its first output terminal, so as to adjust the magnitude of the control voltage Vcol according to the duty factor of the dimming signal Sdim. The current driving unit 250 synchronously adjusts the magnitude of the driving currents I ₁ -In according to the magnitude of the control voltage _Vcol . At the same time, since the distributed delay unit 272 does not receive the dimming signal Sdim, the control signal Scol of the distributed delay unit 272 controls the switches SW1˜SWn to be turned on at the same time, so that the driving currents _{I 1˜In} are simultaneously output to the LED series 50_1～50_n.

When the driving device 200 performs dimming and the duty factor of the dimming signal Sdim is smaller than a preset value, the dimming mode signal Smod of the dimming detector 260 will control the multiplexer 271 to convert the dimming signal received at its input terminal to The optical signal Sdim is output to the decentralized delay unit 272 through its second output terminal. After the distributed delay unit 272 receives the dimming signal Sdim, the control signal Scol generated by it controls the switches SW1 - SWn to be turned on respectively in one cycle, and the turn-on time of the switches SW1 - SWn is the same. Generally speaking, these control signals Scol can transmit pulses at different times to turn on the switches SW1 -SWn at different times. The turn-on times of the switches SW1-SWn are separated but continuous with each other, that is, the pulses for turning on the switches are continuously output at the terminals corresponding to the control signals Scol, and the effect of the continuous output is like shifting the pulses. Wherein, the function of pulse displacement can be accomplished by shift registers, that is, the function of these control signals Scol to transmit pulses at different times can be accomplished by shifting and outputting pulses by multiple shift registers.

At the same time, the distributed delay unit 272 transmits the received dimming signal Sdim to the duty factor-to-voltage converter 273 , and simultaneously outputs a gain signal GN to the duty factor-to-voltage converter 273 . The duty factor-to-voltage converter 273 adjusts the magnitude of the control voltage Vcol according to the duty ratio of the dimming signal _Sdim and the gain signal GN, so as to adjust the magnitude of the driving currents I ₁ -In synchronously. Wherein, the gain signal GN can transmit the gain number, the gain number transmitted by the gain signal GN can be the current number of the driving current I ₁ ~In _n , and the current number of the driving current I ₁ ~In _n is 8 as an example, then the gain signal GN is Teleportation buff number is 8. For example, when the duty factor of the dimming signal Sdim is 1/16, the current magnitude of the driving current I ₁ ~I _n should be 1/16 of the current upper limit, but after adjustment according to the gain signal GN, the driving The currents of the currents I _{1 -In} are adjusted to 1/2 of the upper limit of the current, and combined with the output time of the driving currents I _{1 -In} being 1/8 of the period, a dimming effect of 1/16 can be achieved.

It is worth mentioning that when the decentralized delay unit 272 does not receive the dimming signal Sdim, it may output the gain signal GN with a gain number of 1 or not output the gain signal GN. In addition, when the duty factor-to-voltage converter 273 does not receive the gain signal GN, it generates the corresponding control voltage Vcol according to the duty factor of the dimming signal Sdim.

FIG. 2F is a schematic circuit diagram of the duty factor-to-voltage converter shown in FIG. 2E . Please refer to FIG. 2F. In this embodiment, the duty factor-to-voltage converter 273 includes a low-pass filter circuit LPF1 and an analog multiplier ML1. The low-pass filter circuit LPF1 may be composed of a resistor R1 and a capacitor C1, but not This limits other embodiments. The low-pass filter circuit LPF1 converts the received dimming signal Sdim into a DC level, that is, the low-pass filter circuit LPF1 outputs different DC levels according to different duty factors of the dimming signal Sdim. The analog multiplier ML1 amplifies the DC level output from the low-pass filter circuit LPF1 according to the gain signal GN as the control voltage Vcol. When the gain value transmitted by the gain signal GN is 1, the level of the control voltage Vcol will be the same as the DC level output by the low-pass filter circuit LPF1. When the gain number transmitted by the gain signal GN is 2, the level of the control voltage Vcol will be twice the DC level output by the low-pass filter circuit LPF1 , and so on.

FIG. 2G is another schematic circuit diagram of the duty factor-to-voltage converter shown in FIG. 2E . Please refer to FIG. 2F and FIG. 2G , the difference lies in the multiplexer mux1. The multiplexer mux1 determines whether the DC level output by the low-pass filter circuit LPF1 is transmitted to the analog multiplier ML1 or directly output according to the dimming mode signal Smod. In other words, when the driving device 200 performs dimming and the duty factor of the dimming signal Sdim is greater than or equal to a preset value, it will directly output the DC level output by the low-pass filter circuit LPF1 as the control voltage Vcol. When the driving device 200 performs dimming and the duty factor of the dimming signal Sdim is smaller than a preset value, the DC level output by the low-pass filter circuit LPF1 is sent to the analog multiplier ML1, which is amplified according to the gain signal GN and then output as a control voltage Vcol.

FIG. 2H is another schematic circuit diagram of the current control unit in FIG. 2A coupled to the dimming detector. Please refer to FIG. 2E and FIG. 2H , the difference lies in the distributed delay unit 274 and the omission of the multiplexer 271 . When the driving device 200 performs dimming and the duty factor of the dimming signal Sdim is greater than or equal to a preset value, the decentralized delay unit 274 controls the switches SW1˜SWn to be turned on simultaneously according to the control signal Scol of the dimming mode signal Smod, and does not A gain signal GN or a gain signal GN with a gain number of 1 is output. When the distributed delay unit 274 does not output the gain signal GN, the duty factor to voltage converter 273 generates the control voltage Vcol according to the received dimming signal Sdim. When the distributed delay unit 274 outputs the gain signal GN with a gain number of 1, the duty factor to voltage converter 273 generates the control voltage Vcol according to the received dimming signal Sdim and the gain signal GN.

When the driving device 200 performs dimming and the duty cycle of the dimming signal Sdim is smaller than a preset value, the decentralized delay unit 272 generates a corresponding control signal Scol according to the dimming mode signal Smod to control the switches SW1-SWn to turn on in one cycle. are turned on respectively, and output the gain signal GN corresponding to the current numbers of the driving currents I ₁ -I _n . The duty cycle-to-voltage converter 273 generates the control voltage Vcol according to the received dimming signal Sdim and the gain signal GN.

FIG. 2I is another schematic circuit diagram of the current control unit in FIG. 2A coupled to the dimming detector. Please refer to FIG. 2I , the number of driving currents I ₁ -I _n in this embodiment is 8 as an example, that is, the default value is 1/8. The dimming detector 260 includes a low-pass filter circuit LPF2, an analog-to-digital converter 261 (analog-to-digital converter, hereinafter referred to as: ADC) and an OR gate 262, wherein the analog-to-digital converter 261 uses a 4-bit converter as example. If the duty factor of the dimming signal Sdim is 1/4, the analog-to-digital converter 261 will output "0100", which is "01000000" in digital form. The default value displayed in digital form is "00100000".

According to the above, as long as “1” appears in the first three highest bits, it is greater than the preset value. Therefore, the first three highest bits can be ORed to generate the dimming mode signal Smod. After the "01000000" output by the analog-to-digital converter 261 is operated on the first three highest bits by the OR gate 262, a dimming mode signal Smod with a high logic level will be generated, indicating that the duty cycle of the dimming signal Sdim is greater than the preset value. Next, the multiplexer 271 outputs “01000000” output from the analog-to-digital converter 261 to the duty factor-to-voltage converter 276 according to the dimming mode signal Smod, so as to convert the digital “01000000” into an analog form The output is used as the control voltage Vcol, wherein the duty factor-to-voltage converter 276 may include a digital-to-analog converter (DAC for short) to convert the digital type "01000000" into an analog type. Moreover, when the distributed delay unit 275 does not receive the output of the analog-to-digital converter 261 , correspondingly generate a plurality of control signals Scol to control the switches SW1 -SWn to be turned on simultaneously.

If the duty cycle of the dimming signal Sdim is 1/16, the analog-to-digital converter 261 will output "00010000", and the OR gate 262 will generate a low logic level dimming signal after performing operations on the first three highest bits. Light mode signal Smod. Next, the multiplexer 271 outputs “00010000” output from the analog-to-digital converter 261 to the duty factor-to-voltage converter 276 according to the dimming mode signal Smod. At this time, the distributed delay unit 275 correspondingly generates a plurality of control signals Scol to control the switches SW1 - SWn to be turned on respectively in one cycle. Moreover, the distributed delay unit 275 adjusts "00010000" output by the analog-to-digital converter 261 according to a preset value, that is, "00010000" is multiplied by 8 (equivalent to shifting three bits to the left) to become "10000000". The “10000000” output is used as a gain signal, and the duty cycle to voltage converter 276 converts “10000000” into an analog output as the control voltage Vcol. It should be noted that, in this embodiment, the duty factor to voltage converter 276 may not receive the dimming signal Sdim, so as to simplify the difficulty of circuit design.

According to the above description, the above actions can be compiled into a method to be applied to the driving device 200 . FIG. 3A is a flowchart of a driving method according to an embodiment of the invention. Referring to FIG. 2A and FIG. 3A , the driving device 200 receives the dimming signal Sdim, and can detect whether the driving device 200 is dimming according to the dimming signal Sdim (step S301 ). When the driving device 200 is performing dimming, it evenly distributes the output time of the driving currents I _{1 -In} in one cycle (step S302), and the driving device 200 will output the driving currents I _{1 -In} to drive the light emitting diodes respectively Series 50_1-50_n. When the driving device 200 is not performing dimming, the driving method ends.

FIG. 3B is a flowchart of a driving method according to another embodiment of the present invention. Please refer to FIG. 3A and FIG. 3B , the difference lies in steps S311 , S312 and S313 . When the driving device is dimming, it is determined whether the duty factor of the dimming signal is smaller than a preset value (step S311 ). When the duty cycle of the dimming signal is not less than the preset value, the driving current is simultaneously output in one cycle, and the magnitude of the driving current is adjusted according to the dimming signal (step S312 ). When the duty cycle of the dimming signal is smaller than the preset value, the output time of the driving current in one cycle is evenly distributed, and the current magnitude of the driving current is adjusted accordingly (step S313 ). Wherein, for steps 312 and 313, reference may be made to the description of the above-mentioned embodiment, and details are not repeated here.

To sum up, in the light-emitting diode driving device and the driving method thereof in various embodiments of the present invention, when the driving device performs dimming and the duty factor of the dimming signal is smaller than a preset value, each driving current is evenly distributed in one cycle. In the output time, and correspondingly adjust the current size of each drive current. When the driving device performs dimming and the duty cycle of the dimming signal is greater than or equal to a preset value, the driving current is simultaneously output in a cycle, and the magnitude of the driving current is adjusted according to the dimming signal. In this way, the audio noise and electromagnetic interference caused by the excessive variation of the sum of the driving currents can be suppressed.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: it still Modifications or equivalent replacements can be made to the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims (20)

1. A driving method for a light-emitting diode, suitable for a driving device, characterized in that the driving method comprises: Detect whether the driving device performs dimming; If the driving device is detected to perform dimming, judging whether a duty factor of a dimming signal is smaller than a preset value; When the duty cycle of the dimming signal is greater than or equal to the preset value, adjust the current magnitudes of multiple driving currents, and output the driving currents in a cycle, wherein the output time of the driving currents is equal to the cycle; as well as When the duty cycle of the dimming signal is smaller than the preset value, the driving currents are output during different time periods in the cycle, wherein the output time of the driving currents is shorter than the cycle. 2. The driving method of the light emitting diode according to claim 1, further comprising: When the duty factor of the dimming signal is greater than or equal to the preset value, the individual current magnitudes of the driving currents are adjusted according to the dimming signal. 3. The driving method of a light emitting diode according to claim 2, wherein when the duty cycle of the dimming signal is greater than or equal to the preset value, the driving method is adjusted according to the duty cycle of the dimming signal Current individual current magnitude. 4. The driving method of a light emitting diode according to claim 1, further comprising: When the duty cycle of the dimming signal is smaller than the preset value, the respective current magnitudes of the driving currents and the respective output times in the cycle are set according to the dimming signal. 5. The driving method of a light emitting diode according to claim 4, wherein when the duty cycle of the dimming signal is smaller than the preset value, the driving currents are set according to the duty cycle of the dimming signal Individual current magnitude and individual output time in the cycle. 6. The driving method of a light emitting diode according to claim 1, further comprising: No matter whether the output time of the driving currents is equal to the period or not, the sum of the driving currents in the period is a fixed value when the dimming signal has the same duty cycle. 7. A driving method for a light emitting diode, suitable for a driving device, characterized in that the driving method comprises: receiving a dimming signal; detecting whether the driving device performs dimming; and If the driving device is detected to perform dimming, adjust the magnitude of individual currents among the plurality of driving currents according to a duty factor of the dimming signal, so that the sum of the driving currents in one cycle is proportional to the dimming signal. The duty cycle of the signal, wherein when the duty cycle of the dimming signal is not less than a preset value, the current magnitude of the driving currents is equal to a current upper limit multiplied by the duty cycle, when the dimming signal When the duty cycle of the optical signal is smaller than the preset value, the current magnitude of the driving currents is equal to the current upper limit multiplied by the duty cycle and the number of the driving currents and then divided by the period. 8. The driving method of a light emitting diode according to claim 7, wherein if the driving device is detected to perform dimming, the current magnitude and the current of the driving currents are adjusted according to the duty factor of the dimming signal. output time. 9. The driving method of a light emitting diode according to claim 7, wherein if the driving device is detected to perform dimming, the output time of the driving currents is equal to the cycle, or the output time of the driving currents less than this period. 10. The driving method of a light emitting diode according to claim 9, wherein when the duty cycle of the dimming signal is not less than a preset value, the output time of the driving currents is equal to the period, when the When the duty cycle of the dimming signal is smaller than the preset value, the output time of the driving currents is shorter than the period. 11. The driving method of a light emitting diode according to claim 9, wherein when the dimming signals have the same duty factor, no matter the output time of the driving power is less than or equal to the period, the driving currents are The sum during this period is maintained at a fixed value. 12. A drive circuit for driving a plurality of light emitting diodes, characterized in that it comprises: a plurality of switches for coupling the light emitting diodes; a dimming detector for receiving a dimming signal and outputting a dimming mode signal according to the dimming signal; a current control unit, configured to output a plurality of control signals according to the dimming mode signal and the dimming signal, wherein the control signals respectively control the conduction state of the switches in one cycle; and A current drive unit, coupled to the switches and the current control unit, and the current control unit outputs a control voltage according to the dimming mode signal and the dimming signal, wherein the control voltage controls the current drive unit to adjust multiple driving current to drive the LEDs, and when the duty cycle of the dimming signal is not less than a preset value, the current magnitude of the driving currents is equal to a current upper limit multiplied by the duty cycle, when the When the duty cycle of the dimming signal is smaller than the preset value, the current magnitude of the driving currents is equal to the current upper limit multiplied by the duty cycle and the number of the driving currents and then divided by the period. 13. The driving circuit according to claim 12, wherein the dimming detector detects whether the dimming is performed according to the dimming signal, and outputs a dimming mode signal according to the detection result. 14. The driving circuit according to claim 13, wherein the dimming detector detects whether the dimming is performed according to the duty factor of the dimming signal. 15. The driving circuit according to claim 13, wherein the dimming detector further outputs the dimming mode signal to the current control unit, and detects whether the duty factor of the dimming signal is less than one A preset value is used to set the conduction state of the switches through the dimming mode signal. 16. The driving circuit according to claim 15, wherein the dimming detector detects whether the duty cycle of the dimming signal is smaller than the preset value, so as to control the current through the dimming mode signal The control unit adjusts the driving currents to drive the LEDs. 17. The driving circuit according to claim 15, wherein when the dimming detector detects that dimming is performed and the duty factor of the dimming signal is smaller than the preset value, the The current control unit outputs the control signals to control the conduction time of the switches in the period to be equal and divide the period equally. 18. The driving circuit according to claim 15, wherein when the dimming detector detects that dimming is performed and the duty factor of the dimming signal is greater than or equal to the preset value, The current control unit outputs the control signals to control the conduction time of the switches in the period to be equal to the period. 19. The driving circuit according to claim 16, wherein when the dimming detector detects that dimming is performed and the duty cycle of the dimming signal is smaller than the preset value, the The current control unit outputs the control signals to control the switches to be turned on in the period. 20. The driving circuit according to claim 16, wherein, no matter whether the duty factor of the dimming signal is smaller than the preset value, the driving currents are adjusted so that the driving currents in the period The sum is proportional to the duty cycle of the dimming signal.