WO2014183330A1 - 一种led调光电路 - Google Patents

一种led调光电路 Download PDF

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Publication number
WO2014183330A1
WO2014183330A1 PCT/CN2013/078533 CN2013078533W WO2014183330A1 WO 2014183330 A1 WO2014183330 A1 WO 2014183330A1 CN 2013078533 W CN2013078533 W CN 2013078533W WO 2014183330 A1 WO2014183330 A1 WO 2014183330A1
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Prior art keywords
circuit
delay
led
voltage
signal
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PCT/CN2013/078533
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English (en)
French (fr)
Inventor
张华�
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TCL China Star Optoelectronics Technology Co Ltd
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Shenzhen China Star Optoelectronics Technology Co Ltd
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Priority to US14/111,778 priority Critical patent/US9743499B2/en
Publication of WO2014183330A1 publication Critical patent/WO2014183330A1/zh
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • G09G3/3426—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines the different display panel areas being distributed in two dimensions, e.g. matrix
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/16—Controlling the light source by timing means
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/024—Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/38—Switched mode power supply [SMPS] using boost topology
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/395—Linear regulators
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the invention relates to a backlight module driving circuit, in particular to an LED dimming circuit.
  • the adjustment of the LED brightness is controlled by a pulse width modulation signal (PWM dimming signal), and when the PWM dimming signal is a constant DC high voltage, the LED is constant.
  • the MOS transistor connected to the LED string inside the flow driver IC is always in the on state, and the LED current is constant, and the brightness is the highest at this time.
  • the PWM dimming signal is a rectangular wave
  • the MOS tube inside the IC exchanges between on and off, so that the LED current also becomes a rectangular wave, and the average value of the LED current decreases, and the brightness also decreases.
  • the PWM dimming signals of the LED strings are the same, that is, the MOS transistors connected to the LED strings are simultaneously turned on or off, and the output power varies greatly in each working cycle, resulting in
  • the current in the inductor changes frequently between the maximum and minimum values, generating noise, and at the same time causing impact on components in the circuit.
  • the output voltage has a large ripple and the circuit is unstable.
  • the main object of the present invention is to provide an LED dimming circuit capable of controlling multiple sets of LED strings in a backlight module to be lit at different times in the same working cycle, so that the output power of the whole circuit is constant, avoiding the occurrence of no stable state.
  • the invention provides an LED dimming circuit for controlling a plurality of LED strings to be illuminated at different times in the same working cycle, comprising: a plurality of groups of LED strings, each LED string being connected in parallel;
  • a driving circuit that is connected to the LED string to drive it to illuminate
  • a control circuit connected to the driving circuit, and controlling the illumination of the LED string by inputting a pulse width modulation signal (PWM dimming signal) to the driving circuit;
  • PWM dimming signal a pulse width modulation signal
  • the control circuit includes a voltage comparator and a delay circuit.
  • the voltage comparator is disposed between the delay circuit and the driving circuit, and each delay circuit is sequentially connected in series with each group of driving circuits, and the PWM dimming signal is extended by the delay circuit. After the time delay signal is generated, the sine wave signal of the delayed signal is converted into a square wave or a rectangular wave by the voltage comparator, and transmitted to the driving circuit to sequentially emit the corresponding LED string.
  • the output of the previous set of voltage comparators is connected in series with the next set of delay circuits to transmit the delayed signals of the previous set of outputs to the next set of delay circuits for further delay.
  • the delay circuits connected in series are three groups.
  • the delay circuit is an RC delay circuit, and the input end of the delay circuit is input with a PWM dimming signal, and the output terminal is electrically connected.
  • the high potential end of the voltage comparator is connected.
  • the low potential end of the voltage comparator is connected to a constant comparison voltage.
  • the delay time between the two adjacent PWM dimming signals is set in a high level interval of the PWM dimming signal, so that when the previous LED string is not extinguished between adjacent LED strings, the next LED string is start up.
  • the constant comparison voltage is set between a high potential voltage and a low potential voltage of the input voltage of the PWM dimming signal.
  • the voltage range of the PWM dimming signal is 0-3.3V
  • the voltage range of the constant comparison voltage is 1.6-3.3V.
  • the resistance R and the capacitance C are inversely proportional to the input voltage change rate of the voltage comparator, and the constant comparison voltage is proportional to the delay time.
  • the delay time can be adjusted by adjusting the R value, C value and constant voltage value.
  • the LED dimming circuit of the present invention sequentially delays the input PWM dimming signal by setting a delay circuit in the control circuit, and then delays the PWM output by the voltage comparator output.
  • the delay circuit of the signal output to the next group of control circuits is delayed again to obtain a step-delayed PWM dimming signal, and each LED string is output and controlled, so that the starting times are staggered from each other, and sequentially lit, so that the entire circuit outputs
  • the power is constant, avoiding the voltage instability caused by the simultaneous start of multiple sets of LED strings, and the current variation range in the inductor is also reduced correspondingly, avoiding the unstable state of the circuit caused by the dimming process.
  • the delay time is set to be less than the high potential interval of the PWM dimming signal, to ensure that the previous set of LED strings is not disconnected, the next set of LED strings is activated, and each LED string is started at different times, and is not turned off at the same time.
  • the lighting time of each LED string is evenly distributed, so that the output power is constant.
  • 1 is a circuit diagram of a conventional LED dimming circuit
  • FIG. 2 is a circuit diagram of an LED dimming circuit of the present invention
  • FIG. 3 is a schematic diagram of waveform adjustment of a PWM dimming signal of an LED dimming circuit according to the present invention
  • 4 is a schematic diagram showing the comparison of the delay of the RWM dimming signal of the LED dimming circuit before and after the delay.
  • the present invention provides an LED dimming circuit for controlling a plurality of LED strings 100 to be illuminated at different times during the same duty cycle, which includes - a plurality of sets of LED strings 100, each LED string 100 being connected in parallel ;
  • the driving circuit 200 is connected to the LED string 100 to drive the light to be illuminated;
  • the control circuit 300 is connected to the driving circuit 200, and controls the illumination of the LED string 100 by inputting a pulse width modulation signal (PWM dimming signal) to the driving circuit 200;
  • PWM dimming signal a pulse width modulation signal
  • the control circuit 300 includes a voltage comparator 301 and a delay circuit 302.
  • the voltage comparator 301 is disposed between the delay circuit 302 and the driving circuit 200.
  • Each delay circuit 302 is sequentially connected in series with each group of driving circuits 200. Dimming The signal is delayed by the delay circuit 302 to produce a delay signal, and the sine wave signal of the delayed signal is converted into a square wave or a rectangular wave by the voltage comparator 301, and transmitted to the driving circuit 200 to sequentially emit the corresponding LED string 100.
  • Each group of LED strings 100 is connected in parallel between the driving circuit 200 and the boosting circuit 400.
  • the control circuit 300 inputs a PWM dimming signal to the boosting circuit 400 to control the lighting time and intensity of the LED string 100.
  • a plurality of LED modules are connected in series in each group of LED strings 100.
  • the total control circuit is divided into multiple groups, and the total driving circuit is also divided into multiple groups.
  • the group control circuit 300 is respectively connected in series with the corresponding driving circuit 200.
  • Each group of driving circuits 200 is respectively connected in series with the corresponding LED string 100, and passes through each group of control circuits. 300 respectively adjusts the on-off time of each group of driving circuits 200 to respectively control the lighting time and intensity of each group of LED strings 100.
  • the control circuit 300 includes a voltage comparator 301 and a delay circuit 302 connected in series with each other.
  • the voltage comparator 301 is disposed between the delay circuit 302 and the driving circuit 200.
  • the delay circuit 302 can implement the delay effect by using an RC delay circuit, an integrated IC with a delay function, or a delay time by setting a signal in the processor.
  • the delay circuits connected in series with each other are three groups.
  • the signal A is an initial PWM dimming signal
  • VI is a constant comparison voltage
  • the signal B is a PWM dimming signal after being delayed by the RC delay circuit
  • the signal C is The delayed PWM dimming signal output by the voltage comparator 301.
  • An initial PWM dimming signal (signal A) is input to the delay circuit 302 of the control circuit 300.
  • the initial PWM dimming signal is extended by the delay circuit 302, and the time of the rising edge and the falling edge is extended by the adjustment of the resistor R and the capacitor C.
  • the generated signal is then input to the high potential terminal of the voltage comparator 301, and the low potential terminal of the voltage comparator 301 is connected to a constant comparison voltage VI so that the voltage outputted by the voltage comparator 301 is kept positive. Since the rising edge and the falling edge of the PWM dimming signal become relatively flat, the voltage comparator 301 outputs a low level and the PWM dimming signal continues to rise during the same period in which the PWM dimming signal reaches the comparison voltage value from the low level. During the process, the voltage comparator 301 outputs a high level to generate a signal [.
  • the output of the previous set of voltage comparators 301 is connected in series with the next set of delay circuits 302 to output the previous set.
  • the delayed signal is transmitted to the next set of delay circuits 302 for delay again.
  • the delay circuit 302 and the voltage comparator 301 are respectively connected in the control circuit 300 of each group, and the PWM dimming signal adjusted by the previous group of voltage comparators 301 is connected to the next group of delay circuits 302 for delay.
  • the PWM dimming signal after the delay is input to another group of LED strings 100, and at the same time, another delay PWM switching signal is obtained through the next delay circuit 302.
  • the delay time of each group of LED strings 100 is obtained.
  • a plurality of delay time PWM dimming signals can be obtained, which are respectively transmitted to the control circuit 300 of each LED string 100, and the illumination time of the LED string 100 is separately adjusted according to each delay-adjusted PWM dimming signal. So that the lighting time of each group of LED strings 100 is unequal, and sequentially, so that several groups of LED strings 100 are in one cycle. The lights are sequentially turned on, so that the output power of the entire circuit is constant, and the unstable state is avoided.
  • signal A is an initial PWM dimming signal
  • signal C is a delayed PWM dimming signal processed by delay and voltage comparison.
  • the delay time between the two adjacent PWM dimming signals is set in a high level interval of the PWM dimming signal. In this way, when the previous set of LED strings is disconnected, the next set of LED strings remains on, and the respective LED strings are started at different times, and are not turned off at the same time.
  • the constant comparison voltage is set between a high potential voltage and a low potential voltage of an input voltage of the PWM dimming signal.
  • the voltage range of the PWM dimming signal is 0-3.3V
  • the voltage range of the constant comparison voltage is 1.6-3.3V.
  • the resistance R and the capacitance C are inversely proportional to the input voltage change rate of the voltage comparator 301. That is, the larger the resistance of the resistor R, or the larger the capacity of the capacitor C, the higher the voltage at the high potential end of the voltage comparator 301 is, or the slower the rate of change is, the slower, the PWM dimming signal after the delay.
  • the waveform becomes gentle, and the delay time of the adjacent PWM dimming signal is longer as the constant comparison voltage at the low potential end of the voltage comparator 301 is constant.
  • the constant comparison voltage is proportional to the delay time, and the larger the constant comparison voltage value, the longer the delay time. It can be seen that the length of the delay time can be adjusted by adjusting the R value, the C value and the constant voltage value of the voltage comparator 301 in the RC delay circuit to control the time difference of the illumination of each group of LED strings.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Led Devices (AREA)

Abstract

一种LED调光电路，用于控制多个LED串（100）在同一工作周期内不同时刻发亮。该LED调光电路包括：相互并联的若干组LED串（100）；与LED串（100）连接的驱动电路（200），驱动其发亮；与驱动电路（200）连接的控制电路（300），通过向驱动电路（200）输入脉冲宽度调制信号来控制LED串（100）的发亮。控制电路（300）包括电压比较器（301）和延时电路（302）。电压比较器（301）设于延时电路（302）和驱动电路（200）之间，各延时电路（302）与各组驱动电路（200）依次串联。脉冲宽度调制信号经延时电路（302）延时后生产延时信号，经电压比较器（301）将延时信号的正弦波信号转换为方波或矩形波，传输至驱动电路（200）使相应的LED串（100）依次发光。

Description

说 明 书
一种 LED调光电路
技术领域
本发明涉及一种背光模组驱动电路， 尤其是指一种 LED调光电路。
背景技术
参照图 1所示， 在现有的 LED背光驱动电路图中， LED亮度的调节是通过脉冲宽度调 制信号 （PWM调光信号）控制的， 当 PWM调光信号为恒定的直流高电压时， LED恒流驱 动 IC内部与 LED串连接的 MOS管一直处于导通状态， LED电流恒定， 此时亮度为最高。 调光时， PWM调光信号为矩形波， IC内部的 MOS管在导通和关断之间交换动作，使得 LED 电流同样成为矩形波， LED电流的平均值下降， 亮度也随之降低。
在调光时， 各 LED串的 PWM调光信号是相同的， 即与各 LED串连接的 MOS管同时 处于导通或者关断状态， 在每个工作周期内， 输出功率变化幅度太大， 导致电感中的电流在 最大值与最小值之间频繁变化， 产生噪声， 同时对电路中的元器件造成冲击， 输出电压存在 较大的纹波， 电路工作不稳定。
发明内容
基于现有技术的不足， 本发明的主要目的在于提供可控制背光模组中的多组 LED串在 同一工作周期内不同时刻点亮的 LED调光电路， 使得整个电路输出功率恒定， 避免出现不 稳定状态。
本发明提供了一种 LED调光电路， 用于控制多个 LED串在同一工作周期内不同时刻发 亮， 其包括- 若干组 LED串， 各 LED串相互并联；
驱动电路， 与 LED串连接， 驱动其发亮；
控制电路， 与驱动电路连接， 通过向驱动电路输入脉冲宽度调制信号（PWM调光信号） 来控制 LED串的发亮；
所述控制电路包括电压比较器和延时电路， 电压比较器设于延时电路和驱动电路之间， 各延时电路与各组驱动电路依次串联， 所述 PWM调光信号经延时电路延时后生产延时信 号， 经电压比较器将延时信号的正弦波信号转换为方波或矩形波，传输至驱动电路使相应的 LED串依次发光。
优选地， 在相邻的控制电路上， 前一组电压比较器的输出端与下一组延时电路串联， 以 将前一组输出的延时信号传输至下一组延时电路进行再次延时。 相互串联的延时电路为 3 组。 所述延时电路为 RC延时电路， 所述延时电路输入端导入 PWM调光信号， 输出端与电 压比较器的高电位端连接。 所述电压比较器的低电位端与恒定比较电压相连接。 所述两相邻 PWM调光信号之间的延迟时间设于 PWM调光信号的高电平区间内， 使得 相邻的 LED串间， 上一组 LED串未灭时， 下一组 LED串即启动。
所述恒定比较电压设于 PWM调光信号的输入电压的高电位电压与低电位电压之间， 优 选地， 所述 PWM调光信号的电压范围是 0-3.3V, 恒定比较电压的电压范围为 1.6-3.3V。
在所述 RC延时电路中，电阻 R和电容 C与电压比较器的输入电压变化速度成反比例关 系， 所述恒定比较电压与延迟时间呈正比例关系。 通过调整 R值、 C值及恒定电压值， 可 对延时时间长短进行调整。
与现有技术相比， 本发明的 LED调光电路通过在控制电路中设置延时电路， 对输入的 PWM调光信号进行依次延时控制， 再将经电压比较器输出的延时 PWM调光信号输出至下 一组控制电路的延时电路进行再次延时， 以获得阶梯状延迟的 PWM调光信号， 分别输出控 制各个 LED串， 使其启动时间相互错开， 依次点亮， 使得整个电路输出功率恒定， 避免了 多组 LED串同时启动造成的电压不稳定状况， 电感中的电流变化范围也会相应减小， 避免 调光过程中引起的电路不稳定状态。 同时， 通过设置延迟时间小于 PWM调光信号的高电位 区间， 以保障了上一组 LED串未断开时， 下一组 LED串即启动， 各个 LED串不同时启动， 且不同时关闭。在本 LED调光电路的同一个工作周期内， 均匀分配给各个 LED串的点亮时 刻， 使得输出功率恒定。
附图说明
图 1为现有一种 LED调光电路的电路图；
图 2为本发明一种 LED调光电路的电路图；
图 3为本发明一种 LED调光电路的 PWM调光信号的波形调整示意图；
图 4为本发明一种 LED调光电路的 RWM调光信号的延时前后比较示意图。
具体实施方式
参照图 2所示， 本发明提供了一种 LED调光电路， 用于控制多个 LED串 100在同一工 作周期内不同时刻发亮， 其包括- 若干组 LED串 100， 各 LED串 100相互并联；
驱动电路 200， 与 LED串 100连接， 驱动其发亮；
控制电路 300，与驱动电路 200连接，通过向驱动电路 200输入脉冲宽度调制信号（PWM 调光信号） 来控制 LED串 100的发亮；
所述控制电路 300包括电压比较器 301和延时电路 302， 电压比较器 301设于延时电路 302和驱动电路 200之间， 各延时电路 302与各组驱动电路 200依次串联， 所述 PWM调光 信号经延时电路 302延时后生产延时信号，经电压比较器 301将延时信号的正弦波信号转换 为方波或矩形波， 传输至驱动电路 200使相应的 LED串 100依次发光。
各组 LED串 100并联于驱动电路 200和升压电路 400之间， 控制电路 300向升压电路 400输入 PWM调光信号， 以控制 LED串 100的发光时间和强度。 每组 LED串 100中分别 串联多个 LED模块。
总控制电路分为多组， 总驱动电路亦分为多组， 分组控制电路 300分别与相对应的驱动 电路 200串联， 各组驱动电路 200分别与对应的 LED串 100串联， 通过各组控制电路 300 分别对各组驱动电路 200的通断时间进行调整， 以分别控制各组 LED串 100的发光时间和 强度。
其中， 控制电路 300包括相互串联的电压比较器 301和延时电路 302， 电压比较器 301 设于延时电路 302和驱动电路 200之间。 延时电路 302可采用 RC延时电路、 具有延时功能 的集成 IC或通过在处理器中设定信号发出的延迟时间来实现延迟效果。 在本实施例中， 相 互串联的延时电路为 3组。
参照图 2和图 3所示， 在图 3中， 信号 A为初始 PWM调光信号， VI为恒定比较电压， 信号 B为经 RC延时电路延时处理后的 PWM调光信号，信号 C为经电压比较器 301输出的 延时 PWM调光信号。 向控制电路 300的延时电路 302输入一个初始 PWM调光信号（信号 A)， 初始 PWM调光信号经延时电路 302， 经电阻 R和电容 C的调整将上升沿和下降沿的 时间延长， 生成信号 然后， 输入到电压比较器 301的高电位端， 电压比较器 301的低电 位端与一恒定比较电压 VI相连接， 使得经电压比较器 301整流后输出的电压保持正向。 由 于 PWM调光信号的上升沿和下降沿变得比较平缓，在 PWM调光信号由低电平达到比较电 压值相同的时间内， 电压比较器 301输出为低电平， PWM调光信号持续上升的过程中， 电 压比较器 301输出为高电平， 生成信号〔。
为了对相邻的 LED串 100的发光时间进行调整控制， 在相邻的控制电路 300上， 前一 组电压比较器 301的输出端与下一组延时电路 302串联，以将前一组输出的延时信号传输至 下一组延时电路 302进行再次延时。这样，每组控制电路 300中分别串联延时电路 302和电 压比较器 301，且将前一组电压比较器 301调整后的 PWM调光信号接入下一组延时电路 302 进行再延时， 再次延时后的 PWM调光信号输入至另一组 LED串 100， 同时再通过下一个 延时电路 302， 得到另一个延时 PWM调光信号， 优选地， 各组 LED串 100的延时时间相 同。 以此类推， 可获得多个延迟时间的 PWM调光信号， 分别传输至各 LED串 100的控制 电路 300， 并根据各延迟调整后的 PWM调光信号分别地对 LED串 100的发光时间进行调 整， 使得各组 LED串 100的发光时间不等， 且依次顺延， 使若干组 LED串 100在一个周期 内依次点亮， 使得整个电路输出功率恒定， 避免出现不稳定状态。
参照图 4所示， 在本发明中， 信号 A为初始 PWM调光信号， 信号 C为经延迟和电压比 较处理后的延迟 PWM调光信号。 所述两相邻 PWM调光信号之间的延迟时间设于 PWM调 光信号的高电平区间内。 这样， 保障了上一组 LED串断开时， 下一组 LED串保持接通， 各 个 LED串不同时启动， 且不同时关闭。
在本发明， 所述恒定比较电压设于 PWM调光信号的输入电压的高电位电压与低电位电 压之间。 优选地， 所述 PWM调光信号的电压范围是 0-3.3V, 恒定比较电压的电压范围为 1.6-3.3V。
在所述 RC延时电路中，电阻 R和电容 C与电压比较器 301的输入电压变化速度成反比 例关系。 即电阻 R的阻值越大， 或电容 C的容量越大， 电压比较器 301高电位端的电压由 低升高， 或由高降低的变化速度会渐渐缓慢， 延时后的 PWM调光信号的波形会变得平缓， 在电压比较器 301低电位端的恒定比较电压一定时，相邻的 PWM调光信号的延迟时间越长。 另外， 所述恒定比较电压与延迟时间呈正比例关系， 恒定比较电压值越大， 延迟时间越长。 由此可见， 可通过调整 RC延时电路中的 R值、 C值和电压比较器 301接入的恒定电压值， 来调整延迟时间的长短， 以控制各组 LED串发光的时间差。

Claims

权 利 要 求 书 、 一种 LED调光电路， 用于控制多个 LED串在同一工作周期内不同时刻发亮， 其包括： 若干组 LED串， 各 LED串相互并联； 驱动电路， 与 LED串连接， 驱动其发亮； 控制电路， 与驱动电路连接， 通过向驱动电路输入脉冲宽度调制信号来控制 LED串的发亮； 其中：所述控制电路包括电压比较器和延时电路，电压比较器设于延时电路和驱动电路之间， 各延时电路与各组驱动电路依次串联， 所述脉冲宽度调制信号经延时电路延时后产生延时信 号， 经电压比较器将延时信号的正弦波信号转换为方波或矩形波， 传输至驱动电路使相应的 LED串依次发光。 、 根据权利要求 1所述的 LED调光电路， 其中： 在相邻的控制电路上， 前一组电压比较器的 输出端与下一组延时电路串联， 以将前一组输出的延时信号传输至下一组延时电路进行再次 延时。 、 根据权利要求 2所述的 LED调光电路， 其中： 所述两相邻脉冲宽度调制信号之间的延迟时 间设于脉冲宽度调制信号的高电平区间内。 、 根据权利要求 3所述的 LED调光电路， 其中： 所述延时电路输入端导入脉冲宽度调制信号， 输出端与电压比较器的高电位端连接。 、 根据权利要求 4所述的 LED调光电路， 其中： 所述电压比较器的低电位端与恒定比较电压 相连接。 、 根据权利要求 5所述的 LED调光电路， 其中： 所述恒定比较电压设于脉冲宽度调制信号的 输入电压的高电位电压与低电位电压之间。 、 根据权利要求 6所述的 LED调光电路，其中： 所述脉冲宽度调制信号的电压范围是 0-3.3V。 、 根据权利要求 6所述的 LED调光电路， 其中： 所述恒定比较电压的电压范围为 1.6-3.3V。 、 根据权利要求 2所述的 LED调光电路， 其中： 相互串联的延时电路为 3组。 0、 根据权利要求 1所述的 LED调光电路， 其中： 所述延时电路为 RC延时电路。
1、 根据权利要求 10所述的 LED调光电路， 其中： 在所述 RC延时电路中， 电阻 R和电容 C 与电压比较器的输入电压变化速度成反比例关系。
、 根据权利要求 10所述的 LED调光电路， 其中： 所述恒定比较电压与延迟时间呈正比例关 系。
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