WO2013082825A1 - 发光二极管的驱动电路与方法及其应用的显示装置 - Google Patents

发光二极管的驱动电路与方法及其应用的显示装置 Download PDF

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Publication number
WO2013082825A1
WO2013082825A1 PCT/CN2011/083865 CN2011083865W WO2013082825A1 WO 2013082825 A1 WO2013082825 A1 WO 2013082825A1 CN 2011083865 W CN2011083865 W CN 2011083865W WO 2013082825 A1 WO2013082825 A1 WO 2013082825A1
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Prior art keywords
dimming signal
pulse width
duty ratio
analog
node
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English (en)
French (fr)
Inventor
杨翔
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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 US13/381,044 priority Critical patent/US20130147381A1/en
Publication of WO2013082825A1 publication Critical patent/WO2013082825A1/zh
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    • 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
    • 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]
    • H05B45/39—Circuits containing inverter bridges
    • 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 present invention relates to a driving circuit and method for a light emitting diode, and more particularly to a driving circuit and method for a light emitting diode applicable to a backlight module and a display device.
  • Liquid crystal display (Liquid Crystal Display, LCD) has been widely used in a variety of electronic products, most of the liquid crystal display is a backlight type liquid crystal display, which is composed of a liquid crystal display panel and a backlight module (backlight Module).
  • the backlight module can be divided into a side-light type and a direct-light type according to the incident position of the light source (Direct-light) Type) Two to provide a backlight to the LCD panel.
  • Direct-light Direct-light
  • LED Due to light-emitting diodes (Light-Emitting) Diode, LED) has good optoelectronic properties such as low power consumption, low heat generation, long operating life, impact resistance, small volume, fast response, and color light that emits stable wavelengths, so it is suitable for use in backlight modules.
  • pulse width modulation In the driving circuit of the LED, pulse width modulation is usually used.
  • Modulation, PWM A dimming signal that controls the switching of the LED current to control the brightness of the LED.
  • the invention provides a driving circuit and method for a light emitting diode and a display device thereof, to solve the noise problem that the duty ratio of the dimming signal is too small.
  • a main object of the present invention is to provide a driving circuit for driving a plurality of light emitting diodes, the driving circuit comprising:
  • a power switch connected between the light emitting diode and the first node
  • dimming circuit connected to the power switch, wherein the dimming circuit comprises:
  • An operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, wherein the inverting input terminal is connected to the first node, and the non-inverting input terminal is connected to the second node, the output The end is connected to the power switch;
  • a fourth resistor connected between the first node and the timing controller, wherein an analog dimming signal is used when a duty ratio of the pulse width modulation dimming signal for dimming is less than a predetermined duty ratio
  • the analog controller is input to the fourth resistor, and the analog dimming signal is formed by converting the pulse width modulation dimming signal by reverse and digital-to-analog.
  • the operational amplifier further includes a positive power terminal, and the timing controller provides the pulse when a duty ratio of the pulse width modulation dimming signal is greater than or equal to the preset duty ratio.
  • a width modulated dimming signal is applied to the positive supply terminal of the operational amplifier.
  • the preset duty ratio is 5%, 10% or 20%.
  • a further object of the present invention is to provide a driving method for driving a plurality of light emitting diodes, wherein the light emitting diodes are electrically connected to a driving circuit, and the driving method includes:
  • the duty ratio of the pulse width modulation dimming signal is less than the preset duty ratio, providing an analog dimming signal to the driving circuit to adjust brightness of the LED, the analog dimming signal
  • the pulse width modulation dimming signal is converted by reverse and digital-to-analog conversion.
  • the pulse width modulation dimming signal is inverted by an inverter, and then the inverse pulse width modulation is performed by using a digital to analog converter.
  • the dimming signal is converted to the analog dimming signal.
  • Still another object of the present invention is to provide a display device, including: a display panel, a timing controller, and a backlight module, the backlight module includes: a backplane; and a plurality of LEDs disposed on the backplane; a driving circuit electrically connected to the light emitting diode for driving the plurality of light emitting diodes, wherein the driving circuit comprises: a power switch connected between the light emitting diode and the first node; and a first resistor connected The dimming circuit is connected to the power switch, wherein the dimming circuit comprises: an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal.
  • the inverting input terminal is connected to the first node, the non-inverting input terminal is connected to the second node, the output terminal is connected to the power switch; and the second resistor is connected to the reference voltage and the Between the second nodes; and a third resistor connected between the second node and electrically grounded; and a fourth resistor connected to the first node and the timing control
  • an analog dimming signal is input to the fourth resistor by the timing controller, The analog dimming signal is formed by converting the pulse width modulation dimming signal by reverse and digital-to-analog.
  • the timing controller comprises:
  • a counter for calculating a duty ratio of the pulse width modulation dimming signal
  • a comparator configured to compare whether a calculated duty ratio of the pulse width modulation dimming signal is less than the preset duty ratio
  • a first switch coupled to the comparator and disposed on a path through which the pulse width modulated dimming signal is transmitted to the drive circuit;
  • a second switch is coupled to the comparator and disposed on a path through which the analog dimming signal is transmitted to the drive circuit.
  • the timing controller further includes:
  • a rising edge trigger for triggering the counter to begin calculating a duty cycle of the pulse width modulated dimming signal
  • a falling edge trigger that is used to trigger the counter to end the calculation.
  • the timing controller comprises:
  • a digital to analog converter coupled to the inverter for converting the inverted pulse width modulated dimming signal into the analog dimming signal.
  • the driving circuit and method of the light emitting diode of the invention can improve the noise and the abnormality of the startup caused by the dimming signal with a small duty ratio to ensure the dimming effect of the light emitting diode.
  • FIG. 1 is a cross-sectional view showing a backlight module and a display panel in accordance with a first embodiment of the present invention
  • FIG. 2 shows a circuit diagram of a driving circuit in accordance with an embodiment of the present invention
  • FIG. 3 shows a block diagram of a timing controller in accordance with an embodiment of the present invention.
  • FIG. 1 shows a cross-sectional view of a backlight module and a display panel according to an embodiment of the invention.
  • the driving circuit 150 of this embodiment can be used to drive a plurality of light emitting diodes (Light-Emitting) Diode, LED) 120, these LEDs 120 can be connected in series to form a string of LEDs to serve as a light source for the backlight module 100.
  • the backlight module 100 can be a lateral light input or a direct light input light, which is disposed relative to a display panel 101 (for example, a liquid crystal display panel) to form a display device (for example, a liquid crystal display device).
  • the display device of this embodiment includes a timing controller (Timing The controller (Tcon) 102 is configured to provide an image signal to the display panel 101 and provide a corresponding backlight driving signal to the backlight module 100.
  • Timing The controller (Tcon) 102 is configured to provide an image signal to the display panel 101 and provide a corresponding backlight driving signal to
  • the backlight module 100 can be, for example, a direct type backlight module, including a back plate 110 , a plurality of light emitting diodes (LEDs) 120 , a circuit board 130 , a reflective layer 140 , a driving circuit 150 , and Optical film 160.
  • the backplane 110 is configured to carry the LED 120 and the circuit board 130.
  • the LED 120 can be disposed on the circuit board 130 and electrically connected to the driving circuit 150 through the circuit board 130 for emitting light to the display panel 101.
  • Circuit board 130 can be a printed circuit board (Printed Circuit board, PCB) or flexible printed circuit board (Flexible Printed Circuits, FPC).
  • the reflective layer 140 is formed around the light emitting diode 120 (for example, formed on the circuit board 130 or the back plate 110) to reflect the light of the LED 120.
  • the driving circuit 150 can be electrically connected to the light emitting diode 120 through the circuit board 130.
  • the optical film 160 is disposed above the light emitting diode 120 to improve the uniformity of illumination or the luminous efficiency of the light emitting diode 120.
  • the driving circuit of the present invention can also be applied to a laterally-lit backlight module (not shown).
  • the driving circuit 150 of this embodiment includes a power switch Q1, a first resistor R1, a dimming circuit 103, and a fourth resistor R4.
  • the power switch Q1 is connected between the light emitting diode 120 and the first node N1.
  • the first resistor R1 is connected to the first node N1 and is electrically grounded.
  • the dimming circuit 103 is connected to the power switch Q1 for receiving a pulse width modulation (PWM) dimming signal or an analog dimming signal to adjust the brightness of the LED 120.
  • PWM pulse width modulation
  • the fourth resistor R4 is connected between the first node N1 and the timing controller 102.
  • the power switch Q1 is, for example, a depletion type N-channel metal oxide semiconductor (NMOS) transistor, the drain of which is connected to the light emitting diode 120; the source thereof is connected to the first resistor R1; It is connected to the operational amplifier OP1.
  • NMOS metal oxide semiconductor
  • the dimming circuit 103 of this embodiment includes an operational amplifier OP1, a second resistor R2, and a third resistor R3.
  • the operational amplifier OP1 has an inverting input terminal 151, a non-inverting input terminal 152, an output terminal 153, a positive power supply terminal 154, and a negative power supply terminal 155.
  • the inverting input terminal 151 is connected to the first node N1
  • the non-inverting input terminal 152 is connected to the second node N2
  • the output terminal 153 is connected to the gate of the power switch Q1.
  • the second resistor is connected between the reference voltage VREF and the second node N2, and the third resistor is connected between the second node N2 and electrically grounded.
  • the dimming circuit 103 can be integrated into an IC chip.
  • the system terminal can transmit a PWM dimming signal to the timing controller 102, and the timing controller 102 can selectively transmit the PWM dimming signal according to the duty ratio of the PWM dimming signal.
  • the PWM dimming signal or the analog dimming signal is sent to the driving circuit 150 to adjust the brightness of the LED 120.
  • the timing controller 102 can provide the PWM dimming signal to the driving circuit 150. At this time, the PWM dimming signal is transmitted.
  • the timing controller 102 can provide the analog dimming signal to the driving circuit 150.
  • the PWM dimming signal is input to the driving via the fourth resistor R4.
  • the circuit 150 is simultaneously input to the inverting input terminal 151 of the operational amplifier OP1.
  • the preset duty ratio is 10%, but is not limited thereto. In the embodiment, the preset duty ratio may be 20% or 5%.
  • the timing controller 102 includes a counter 171 and a rising edge trigger (rising) Edge trigger) 172, falling edge trigger (falling edge Trigger) 173, comparator 174, first switch SW1, second switch SW2, inverter 175, and digital-to-analog converter (D/A) Converter) 176.
  • the rising edge flip-flop 172 and the falling edge flip-flop 173 are respectively connected to the counter 171, the counter 171 connected to the oscillator OSC is further connected to the comparator 174, and the comparator 174 is respectively connected to the first switcher SW1 and the second switcher.
  • the first switch SW1 is disposed on the path of the PWM dimming signal transmitted to the driving circuit 150
  • the second switch SW2 is disposed on the path of the analog dimming signal transmitted to the driving circuit 150
  • the inverter 175 is connected Between the second switcher SW2 and the digital-to-analog converter 176, for inverting the PWM dimming signal, the digital-to-analog converter 176 is connected to the inverter 175 for converting the reversed PWM dimming signal Into the analog signal.
  • the PWM dimming signal when the system side transmits the PWM dimming signal to the timing controller 102, the PWM dimming signal first triggers the counter 171 through the rising edge flip-flop 172 to start calculating the duty ratio of the PWM dimming signal.
  • the falling edge flip-flop 173 can trigger the counter 171 to end the calculation.
  • the comparator 174 can compare whether the calculation result of the counter 171 (the duty ratio of the PWM dimming signal) is less than the preset duty ratio.
  • the comparator 174 may output a high level signal to the first switch SW1, and output a low level signal to the second switch SW2, The path for transmitting the PWM dimming signal to the driving circuit 150 is turned on, and the path of the analog dimming signal to the driving circuit 150 is turned off, so that the timing controller 102 supplies the PWM dimming signal to the driving circuit 150.
  • the comparator 174 may output a low level signal to the first switch SW1, and output a high level signal to the second switch SW2 to turn off the PWM modulation.
  • the optical signal is transmitted to the path of the driving circuit 150, and the path of the analog dimming signal to the driving circuit 150 is turned on, so that the timing controller 102 supplies the analog dimming signal to the driving circuit 150.
  • the timing controller 102 in the normal dimming mode, when the timing controller 102 detects that the duty ratio of the PWM dimming signal is greater than or equal to the preset duty ratio, the timing controller 102 can directly provide the PWM dimming signal to The circuit 150 is driven to adjust the brightness of the light emitting diode 120. At this time, the PWM dimming signal is transmitted from the timing controller 102 to the positive power terminal 154 of the operational amplifier OP1. As shown in FIG. 2, in the normal dimming mode, the current setting point of the dimming circuit 103 is VREF*R3/(R2+R3)/R1, and is at the inverting input terminal 151 of the operational amplifier OP1 and non-inverting.
  • the voltage at the input terminal 152 needs to be equal, that is, the voltage generated at the first resistor R1 needs to be equal to VREF*R3/(R2+R3).
  • the resistance value of the power switch Q1 can be changed to change the magnitude of the driving current to ensure that the voltages are equal, and the brightness of the light emitting diode 120 can be adjusted by the change of the driving current.
  • the timing controller 102 when the timing controller 102 detects that the duty ratio of the PWM dimming signal is less than the preset duty ratio, the timing controller 102 can provide only the analog dimming signal to the driving circuit. 150 to adjust the brightness of the light emitting diode 120.
  • the analog dimming signal is formed by converting the PWM dimming signal through reverse and digital-to-analog.
  • the analog dimming signal input to the driving circuit 150 can be voltage-dropped through the fourth resistor R4, so that the voltage generated at the first resistor R1 can be equal to VREF*R3/(R2+R3), thereby changing the driving. Current to adjust the brightness of the LED 120.
  • the analog dimming signal can dynamically change the current set point of the dimming circuit 103 to change the driving current to achieve the purpose of adjusting the brightness.
  • the power switch Q1 does not need to be controlled by the switch, so that the current can be suddenly turned on and off.
  • the driving circuit 150 can provide a linear variable current to the LED 120, which can be improved. Noise and abnormal startup problems.
  • the driving method of the embodiment includes: detecting a duty ratio of the PWM dimming signal; when the duty ratio of the PWM dimming signal is greater than or equal to a preset duty ratio, Providing a PWM dimming signal dimming signal to the driving circuit 150 to adjust the brightness of the LED 120; and providing an analog dimming signal to the driving circuit 150 when the duty ratio of the PWM dimming signal is less than the preset duty ratio, To adjust the brightness of the LED 120, the analog dimming signal is formed by converting the PWM dimming signal through reverse and digital-to-analog.
  • the driving circuit and method of the LED of the present invention can improve the noise and the abnormality of the startup caused by the dimming signal with a small duty ratio to ensure the dimming effect of the LED.

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  • Computer Hardware Design (AREA)
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Abstract

一种发光二极管的驱动电路与方法及其应用的显示装置。此驱动电路包括功率开关（Q1）及调光电路（103）。此方法包括侦测一脉冲宽度调制调光信号的占空比；以及当所述脉冲宽度调制调光信号的占空比小于所述预设占空比时，提供一模拟调光信号至所述驱动电路。此驱动电路与方法可应用于显示装置，并可改善在调光信号的占空比太小时的噪声问题。

Description

发光二极管的驱动电路与方法及其应用的显示装置 技术领域
本发明涉及一种发光二极管的驱动电路与方法，特别是涉及一种可应用于背光模块与显示装置的发光二极管的驱动电路与方法。
 背景技术
液晶显示器(Liquid Crystal Display，LCD)已被广泛应用于各种电子产品中，液晶显示器大部分为背光型液晶显示器，其是由液晶显示面板及背光模块(backlight module)所组成。背光模块可依照光源入射位置的不同分成侧向式入光(Side-light type)与直下式入光(Direct-light type)两种，藉以提供背光源至液晶显示面板。
由于发光二极管(Light-Emitting Diode，LED)具有低耗电量、低发热量、操作寿命长、耐撞击、体积小、反应速度快、以及可发出稳定波长的色光等良好光电特性，因而适合应用于背光模块的光源。
在LED的驱动电路中，通常使用脉冲宽度调制(pulse width modulation，PWM)调光信号来控制LED电流的开关，以控制LED的亮度。
然而，当调光信号的占空比(Duty)太小时，LED电流的开关时间很短，而容易产生噪声(noise)，且容易导致开机异常。
故，有必要提供一种发光二极管的驱动电路与方法及其应用的显示装置，以解决现有技术所存在的问题。
 技术问题
本发明提供一种发光二极管的驱动电路与方法及其应用的显示装置，以解决在调光信号的占空比太小时的噪声问题。
 技术解决方案
本发明的主要目的在于提供一种驱动电路，用于驱动多个发光二极管，所述驱动电路包括：
功率开关，连接于所述发光二极管与第一节点之间；
第一电阻，连接于所述第一节点，并电性接地；
调光电路，连接于所述功率开关，其中所述调光电路包括：
运算放大器，具有反相输入端、非反相输入端及输出端，所述反相输入端是连接于所述第一节点，所述非反相输入端是连接于第二节点，所述输出端是连接于所述功率开关；
第二电阻，连接于参考电压与所述第二节点之间；以及
第三电阻，连接于所述第二节点之间，并电性接地；以及
第四电阻，连接于所述第一节点与时序控制器之间，其中当一用于调光的脉冲宽度调制调光信号的占空比小于一预设占空比时，一模拟调光信号是由所述时序控制器输入至所述第四电阻，所述模拟调光信号是将所述脉冲宽度调制调光信号通过反向及数模转换而成。
在本发明的一实施例中，所述运算放大器更包括正电源端，当脉冲宽度调制调光信号的占空比大于等于所述预设占空比时，所述时序控制器提供所述脉冲宽度调制调光信号至所述运算放大器的所述正电源端。
在本发明的一实施例中，所述预设占空比为5%、10%或20%。
本发明的又一目的在于提供一种驱动方法，用于驱动多个发光二极管，其中所述发光二极管是电性连接于一驱动电路，所述驱动方法包括：
侦测一用于调光的脉冲宽度调制调光信号的占空比；
当所述脉冲宽度调制调光信号的占空比大于或等于一预设占空比时，提供所述脉冲宽度调制调光信号至所述驱动电路，以调整所述发光二极管的亮度；以及
当所述脉冲宽度调制调光信号的占空比小于所述预设占空比时，提供一模拟调光信号至所述驱动电路，以调整所述发光二极管的亮度，所述模拟调光信号是将所述脉冲宽度调制调光信号通过反向及数模转换而成。
在本发明的一实施例中，当提供所述模拟调光信号时，利用反向器将所述脉冲宽度调制调光信号反向，接着，利用数模转换器将反向后的脉冲宽度调制调光信号转换成所述模拟调光信号。
本发明的又一目的在于提供一种显示装置，所述显示装置包括：显示面板、时序控制器以及背光模块，背光模块包括：背板；多个发光二极管，设置于所述背板上；以及驱动电路，电性连接于所述发光二极管，用于驱动所述多个发光二极管，其中所述驱动电路包括：功率开关，连接于所述发光二极管与第一节点之间；第一电阻，连接于所述第一节点，并电性接地；调光电路，连接于所述功率开关，其中所述调光电路包括：运算放大器，具有反相输入端、非反相输入端及输出端，所述反相输入端是连接于所述第一节点，所述非反相输入端是连接于第二节点，所述输出端是连接于所述功率开关；第二电阻，连接于参考电压与所述第二节点之间；以及第三电阻，连接于所述第二节点之间，并电性接地；以及第四电阻，连接于所述第一节点与所述时序控制器之间，其中当一用于调光的脉冲宽度调制调光信号的占空比小于一预设占空比时，一模拟调光信号是由所述时序控制器输入至所述第四电阻，所述模拟调光信号是将所述脉冲宽度调制调光信号通过反向及数模转换而成。
在本发明的一实施例中，所述时序控制器包括：
计数器，用于计算所述脉冲宽度调制调光信号的占空比；
比较器，用于比较计算后的所述脉冲宽度调制调光信号的占空比是否小于所述预设占空比；
第一切换器，连接于所述比较器，并设置于所述脉冲宽度调制调光信号传送至所述驱动电路的路径上；以及
第二切换器，连接于所述比较器，并设置于所述模拟调光信号传送至所述驱动电路的路径上。
在本发明的一实施例中，所述时序控制器还包括：
上升沿触发器，用于触发所述计数器开始计算所述脉冲宽度调制调光信号的占空比；以及
下降沿触发器，用于触发所述计数器结束计算。
在本发明的一实施例中，所述时序控制器包括：
反向器，用于将所述脉冲宽度调制调光信号反向；以及
数模转换器，连接于所述反向器，用于将反向后的所述脉冲宽度调制调光信号转换成所述模拟调光信号。
 有益效果
本发明的发光二极管的驱动电路与方法可改善具有小占空比的调光信号所导致的噪声及开机异常问题，以确保发光二极管的调光效果。
 附图说明
图1显示依照本发明的第一实施例的背光模块与显示面板的剖面示意图；
图2显示依照本发明的一实施例的驱动电路的电路图；以及
图3显示依照本发明的一实施例的时序控制器的方块图。
 本发明的最佳实施方式
以下各实施例的说明是参考附加的图式，用以例示本发明可用以实施的特定实施例。本发明所提到的方向用语，例如「上」、「下」、「前」、「后」、「左」、「右」、「内」、「外」、「侧面」等，仅是参考附加图式的方向。因此，使用的方向用语是用以说明及理解本发明，而非用以限制本发明。
在图中，结构相似的单元是以相同标号表示。
请参照图1，其显示依照本发明的一实施例的背光模块与显示面板的剖面示意图。本实施例的驱动电路150可用以驱动多个发光二极管(Light-Emitting Diode，LED)120，这些发光二极管120可串联成一发光二极管串，以作为背光模块100的光源。此背光模块100可为侧向式入光或直下式入光，其相对于一显示面板101(例如液晶显示面板)来设置，而形成一显示装置(例如液晶显示装置)。本实施例的显示装置包括一时序控制器(Timing Controller，Tcon)102，用于提供影像信号至显示面板101，且提供对应的背光驱动信号至背光模块100。
如图1所示，在本实施例中，背光模块100可例如为直下式背光模块，其包括背板110、多个发光二极管(LED)120、电路板130、反射层140、驱动电路150及光学膜片160。背板110用以承载发光二极管120及电路板130，发光二极管120可设置于电路板130上，并通过电路板130来电性连接于驱动电路150，用以发光来提供光线至显示面板101。电路板130可为印刷电路板(Printed circuit board，PCB)或柔性印刷电路板(Flexible Printed Circuits，FPC)。反射层140是形成于发光二极管120的周围(例如形成于电路板130或背板110上)，用以反射发光二极管120的光线。驱动电路150可通过电路板130来电性连接于发光二极管120。光学膜片160是设置于发光二极管120上方，用以改善发光二极管120的发光均匀性或发光效率。
在另一实施例中，本发明的驱动电路亦可应用于侧向式入光的背光模块(未显示)。
请参照图2，其显示依照本发明的一实施例的驱动电路的电路图。本实施例的驱动电路150包括功率开关 Q1、第一电阻R1、调光电路103及第四电阻R4。功率开关Q1是连接于发光二极管120与第一节点N1之间。第一电阻R1是连接于所述第一节点N1，并电性接地。调光电路103是连接于所述功率开关Q1，用于接收一脉冲宽度调制(PWM)调光信号或一模拟调光信号，以调整发光二极管120的亮度。第四电阻R4是连接于所述第一节点N1与时序控制器102之间。
在本实施例中，功率开关Q1例如为耗尽型N沟道金属氧化物半导体(NMOS)晶体管，其漏极是连接于发光二极管120；其源极是连接于第一电阻R1；其栅极是连接于运算放大器OP1。
如图2所示，本实施例的调光电路103包括运算放大器OP1、第二电阻R2及第三电阻R3。运算放大器OP1具有反相输入端151、非反相输入端152、输出端153、正电源端154及负电源端155。反相输入端151是连接于第一节点N1，非反相输入端152是连接于第二节点N2，输出端153是连接于功率开关Q1的栅极。第二电阻是连接于参考电压VREF与第二节点N2之间，第三电阻是连接于第二节点N2之间，并电性接地。其中，调光电路103可整合成一IC芯片。
当调整发光二极管120的亮度时，系统端(未显示)可传送一PWM调光信号至时序控制器102，而时序控制器102可依据此PWM调光信号的占空比来选择性地传送此PWM调光信号或模拟调光信号至驱动电路150，以调整发光二极管120的亮度。当系统端传来的PWM调光信号的占空比大于或等于一预设占空比时，时序控制器102可提供此PWM调光信号至驱动电路150，此时，PWM调光信号是传送至运算放大器OP1的正电源端154。当PWM调光信号的占空比小于预设占空比时，时序控制器102可提供此模拟调光信号至驱动电路150，此时，PWM调光信号是经由第四电阻R4来输入至驱动电路150，且同时输入至运算放大器OP1的反相输入端151。在本实施例中，此预设占空比为10%，然不限于此，在其实施例中，此预设占空比可为20%或5%。
请参照图3，其显示依照本发明的一实施例的时序控制器的方块图。在本实施例中，时序控制器102包括计数器171、上升沿触发器(rising edge trigger)172、下降沿触发器(falling edge trigger)173、比较器174、第一切换器SW1、第二切换器SW2、反向器175及数模转换器(D/A converter)176。上升沿触发器172及下降沿触发器173分别连接于计数器171，接有振荡器OSC的计数器171是更连接于比较器174，比较器174是分别连接于第一切换器SW1及第二切换器SW2，第一切换器SW1是设置于PWM调光信号传送至驱动电路150的路径上，第二切换器SW2是设置于模拟调光信号传送至驱动电路150的路径上，反向器175是连接于第二切换器SW2与数模转换器176之间，用于将PWM调光信号反向，数模转换器176是连接于反向器175，用于将反向后的PWM调光信号转换成模拟信号。
如图3所示，当系统端传送PWM调光信号至时序控制器102时，PWM调光信号会先通过上升沿触发器172来触发计数器171开始计算PWM调光信号的占空比。当PWM调光信号关断时，下降沿触发器173可触发计数器171结束计算。接着，比较器174可比较计数器171的计算结果(PWM调光信号的占空比)是否小于预设占空比。当PWM调光信号的占空比大于或等于预设占空比时，比较器174可输出一高电平信号至第一切换器SW1，且输出一低电平信号至第二切换器SW2，以开启PWM调光信号传送至驱动电路150的路径，并关闭模拟调光信号传送至驱动电路150的路径，使得时序控制器102提供PWM调光信号至驱动电路150。当PWM调光信号的占空比小于预设占空比时，比较器174可输出低电平信号至第一切换器SW1，且输出高电平信号至第二切换器SW2，以关闭PWM调光信号传送至驱动电路150的路径，并开启模拟调光信号传送至驱动电路150的路径，使得时序控制器102提供模拟调光信号至驱动电路150。
如图2所示，在正常调光模式中，当时序控制器102侦测PWM调光信号的占空比大于或等于预设占空比时，时序控制器102可直接提供PWM调光信号至驱动电路150，以调整发光二极管120的亮度。此时，PWM调光信号是由时序控制器102传送至运算放大器OP1的正电源端154。如图2所示，在正常调光模式中，调光电路103的电流设定点为VREF*R3/(R2+R3)/R1，且在运算放大器OP1的反相输入端151及非反相输入端152的电压需保持相等，亦即在第一电阻R1所产生的电压需等于VREF*R3/(R2+R3)。此时，可改变功率开关Q1的阻值来改变驱动电流的大小，以确保电压相等，且可通过驱动电流的改变来调整发光二极管120的亮度。
如图2所示，在模拟调光模式中，当时序控制器102侦测PWM调光信号的占空比小于预设占空比时，时序控制器102可仅提供模拟调光信号至驱动电路150，以调整发光二极管120的亮度。其中，模拟调光信号是将PWM调光信号通过反向及数模转换而成。此时，输入至驱动电路150的模拟调光信号可通过第四电阻R4来进行压降，使得在第一电阻R1所产生的电压可等于VREF*R3/(R2+R3)，进而可改变驱动电流，以调整发光二极管120的亮度。因此，模拟调光信号可动态地改变调光电路103的电流设定点，以改变驱动电流，达到调整亮度的目的。在模拟调光模式中，不需对功率开关Q1进行开关控制，因而可避免电流突然的开通和关断，此时，驱动电路150可提供一个线性的可变电流至发光二极管120，而可改善噪声(noise)及开机异常的问题。
当利用驱动电路150来驱动发光二极管120时，本实施例的驱动方法包括：侦测PWM调光信号的占空比；当PWM调光信号的占空比大于或等于预设占空比时，提供PWM调光信号调光信号至驱动电路150，以调整发光二极管120的亮度；以及当PWM调光信号的占空比小于预设占空比时，提供一模拟调光信号至驱动电路150，以调整发光二极管120的亮度，此模拟调光信号是将PWM调光信号通过反向及数模转换而成。
由上述可知，本发明的发光二极管的驱动电路与方法可改善具有小占空比的调光信号所导致的噪声及开机异常问题，以确保发光二极管的调光效果。
综上所述，虽然本发明已以优选实施例揭露如上，但上述优选实施例并非用以限制本发明，本领域的普通技术人员，在不脱离本发明的精神和范围内，均可作各种更动与润饰，因此本发明的保护范围以权利要求界定的范围为准。
 本发明的实施方式
工业实用性
序列表自由内容

Claims (12)

  1. 一种驱动电路，用于驱动多个发光二极管，包括：
    功率开关，连接于所述发光二极管与第一节点之间；
    第一电阻，连接于所述第一节点，并电性接地；
    调光电路，连接于所述功率开关，其中所述调光电路包括：
    运算放大器，具有反相输入端、非反相输入端及输出端，所述反相输入端是连接于所述第一节点，所述非反相输入端是连接于第二节点，所述输出端是连接于所述功率开关；
    第二电阻，连接于参考电压与所述第二节点之间；以及
    第三电阻，连接于所述第二节点之间，并电性接地；以及
    第四电阻，连接于所述第一节点与时序控制器之间，其中当一用于调光的脉冲宽度调制调光信号的占空比小于一预设占空比时，一模拟调光信号是由所述时序控制器输入至所述第四电阻，所述模拟调光信号是将所述脉冲宽度调制调光信号通过反向及数模转换而成。
  2. 根据权利要求1所述的驱动电路，其中所述运算放大器更包括正电源端，当脉冲宽度调制调光信号的占空比大于等于所述预设占空比时，所述时序控制器提供所述脉冲宽度调制调光信号至所述运算放大器的所述正电源端。
  3. 根据权利要求1所述的驱动电路，其中所述预设占空比为5%、10%或20%。
  4. 一种驱动方法，用于驱动多个发光二极管，其中所述发光二极管是电性连接于一驱动电路，所述驱动方法包括：
    侦测一用于调光的脉冲宽度调制调光信号的占空比；
    当所述脉冲宽度调制调光信号的占空比大于或等于一预设占空比时，提供所述脉冲宽度调制调光信号至所述驱动电路，以调整所述发光二极管的亮度；以及
    当所述脉冲宽度调制调光信号的占空比小于所述预设占空比时，提供一模拟调光信号至所述驱动电路，以调整所述发光二极管的亮度，所述模拟调光信号是将所述脉冲宽度调制调光信号通过反向及数模转换而成。
  5. 根据权利要求4所述的驱动方法，其中当提供所述模拟调光信号时，利用反向器将所述脉冲宽度调制调光信号反向，接着，利用数模转换器将反向后的脉冲宽度调制调光信号转换成所述模拟调光信号。
  6. 根据权利要求1所述的驱动方法，其中所述预设占空比为5%、10%或20%。
  7. 一种显示装置，包括：
    显示面板；
    时序控制器；以及
    背光模块，包括：
    背板；
    多个发光二极管，设置于所述背板上；以及
    驱动电路，电性连接于所述发光二极管，用于驱动所述多个发光二极管，其中所述驱动电路包括：
    功率开关，连接于所述发光二极管与第一节点之间；
    第一电阻，连接于所述第一节点，并电性接地；
    调光电路，连接于所述功率开关，其中所述调光电路包括：
    运算放大器，具有反相输入端、非反相输入端及输出端，所述反相输入端是连接于所述第一节点，所述非反相输入端是连接于第二节点，所述输出端是连接于所述功率开关；
    第二电阻，连接于参考电压与所述第二节点之间；以及
    第三电阻，连接于所述第二节点之间，并电性接地；以及
    第四电阻，连接于所述第一节点与所述时序控制器之间，其中当一用于调光的脉冲宽度调制调光信号的占空比小于一预设占空比时，一模拟调光信号是由所述时序控制器输入至所述第四电阻，所述模拟调光信号是将所述脉冲宽度调制调光信号通过反向及数模转换而成。
  8. 根据权利要求7所述的显示装置，其中所述预设占空比为5%、10%或20%。
  9. 根据权利要求7所述的显示装置，其中所述时序控制器包括：
    计数器，用于计算所述脉冲宽度调制调光信号的占空比；
    比较器，用于比较计算后的所述脉冲宽度调制调光信号的占空比是否小于所述预设占空比；
    第一切换器，连接于所述比较器，并设置于所述脉冲宽度调制调光信号传送至所述驱动电路的路径上；以及
    第二切换器，连接于所述比较器，并设置于所述模拟调光信号传送至所述驱动电路的路径上。
  10. 根据权利要求9所述的显示装置，其中所述时序控制器还包括：
    上升沿触发器，用于触发所述计数器开始计算所述脉冲宽度调制调光信号的占空比；以及
    下降沿触发器，用于触发所述计数器结束计算。
  11. 根据权利要求7所述的显示装置，其中所述时序控制器包括：
    反向器，用于将所述脉冲宽度调制调光信号反向；以及
    数模转换器，连接于所述反向器，用于将反向后的所述脉冲宽度调制调光信号转换成所述模拟调光信号。
  12. 根据权利要求7所述的显示装置，其中所述运算放大器更包括正电源端，当脉冲宽度调制调光信号的占空比大于等于所述预设占空比时，所述时序控制器提供所述脉冲宽度调制调光信号至所述运算放大器的所述正电源端。
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