WO2011131086A1 - 驱动电路及其驱动方法和液晶显示器 - Google Patents

驱动电路及其驱动方法和液晶显示器 Download PDF

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Publication number
WO2011131086A1
WO2011131086A1 PCT/CN2011/072466 CN2011072466W WO2011131086A1 WO 2011131086 A1 WO2011131086 A1 WO 2011131086A1 CN 2011072466 W CN2011072466 W CN 2011072466W WO 2011131086 A1 WO2011131086 A1 WO 2011131086A1
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WIPO (PCT)
Prior art keywords
liquid crystal
crystal display
backlight
driving circuit
reset signal
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Application number
PCT/CN2011/072466
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English (en)
French (fr)
Inventor
于尧
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北京京东方光电科技有限公司
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Application filed by 北京京东方光电科技有限公司 filed Critical 北京京东方光电科技有限公司
Priority to US13/377,955 priority Critical patent/US9240155B2/en
Publication of WO2011131086A1 publication Critical patent/WO2011131086A1/zh

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Classifications

    • 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
    • G09G3/36—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 using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3674—Details of drivers for scan electrodes
    • G09G3/3677—Details of drivers for scan electrodes suitable for active matrices only
    • 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
    • G09G2310/06—Details of flat display driving waveforms
    • G09G2310/061—Details of flat display driving waveforms for resetting or blanking
    • G09G2310/063—Waveforms for resetting the whole screen at once
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/14—Detecting light within display terminals, e.g. using a single or a plurality of photosensors
    • G09G2360/145—Detecting light within display terminals, e.g. using a single or a plurality of photosensors the light originating from the display screen

Definitions

  • Driving circuit driving method thereof and liquid crystal display
  • the present invention relates to a driving circuit, a driving method thereof, and a liquid crystal display. Background technique
  • Liquid crystal displays are currently commonly used flat panel displays, and Thin Film Transistor Liquid Crystal Display (TFT-LCD) is a mainstream product in liquid crystal displays.
  • TFT-LCD Thin Film Transistor Liquid Crystal Display
  • the image sticking phenomenon in the LCD screen is eliminated by using a power module with a reset function or a separate chip with a reset function.
  • These devices mainly detect the input voltage of the TFT-LCD.
  • a reset signal is output to the gate driving integrated circuit (IC), and all output voltages of the gate driving IC are pulled up to the gate turn-on voltage, and the corresponding pixels are The gate of the thin film transistor is turned on to achieve the function of eliminating image sticking.
  • the residual image mainly exists for a period of time after the backlight is turned off and before the input signal is turned off.
  • the input signal is turned off more than 200ms after the backlight is turned off, and then the input voltage is turned off. Therefore, it is still possible to perform image sticking within 200 ms after the backlight is turned off by the prior art method.
  • the reset signal is output because the detection input voltage is lowered to a certain value, and the input voltage at this time is still in a critical state for the power supply module and the driving IC to operate, and the output voltage is lowered.
  • the time is generally 0 ⁇ 10ms (the operating state of the power module and the gate driver IC are in a critical state), so the pixel capacitance and the storage capacitor of the TFT-LCD cannot be discharged quickly, so that the afterimage cannot be quickly eliminated.
  • Embodiments of the present invention provide a driving circuit, a driving method thereof, and a liquid crystal display, so as to perform image sticking elimination while the backlight is turned off, thereby improving display performance of the liquid crystal display.
  • An embodiment of the present invention provides a driving circuit for a liquid crystal display, comprising: a photosensitive element disposed on a liquid crystal panel of the liquid crystal display, detecting an operating state of a backlight of the liquid crystal display; and resetting a signal output The device receives an input signal from the photosensitive element according to an operating state of the backlight, and outputs a reset signal to a gate driver of the liquid crystal display to turn on all gate lines on the liquid crystal panel.
  • a driving method of a liquid crystal display includes: detecting an operating state of a backlight of the liquid crystal display; and outputting a reset signal when the detected backlight of the liquid crystal display is turned off
  • the device outputs a reset signal to the gate line driver of the liquid crystal panel to turn on all gate lines on the liquid crystal panel.
  • a further embodiment of the present invention provides a driving circuit for a liquid crystal display, comprising: a photodiode disposed on the liquid crystal panel for detecting an operating state of a backlight of the liquid crystal display; a non-inverting amplifier, The photodiode is connected; a P-type metal-oxide-semiconductor transistor (PMOS) having a gate connected to an output of the non-inverting amplifier, wherein the turn-on and turn-off of the PMOS are controlled by the non-inverting amplifier, thereby outputting A reset signal is applied to the gate driver of the liquid crystal display to turn on all gate lines.
  • PMOS P-type metal-oxide-semiconductor transistor
  • FIG. 1A is a schematic top plan view of a liquid crystal display according to an embodiment of the present invention.
  • FIG. 1B is an enlarged schematic structural view of the driving circuit of FIG. 1A;
  • FIG. 2 is a schematic diagram showing an equivalent structure of a driving circuit according to an embodiment of the present invention.
  • FIG. 3 is a timing diagram of signals of a driving circuit according to an embodiment of the present invention. detailed description
  • FIG. 1A is a schematic top plan view of a liquid crystal display according to an embodiment of the present invention
  • FIG. 1B is an enlarged schematic structural view of the driving circuit of FIG. 1A.
  • this embodiment provides a liquid crystal display including a liquid crystal panel 1, a driving circuit 2, a gate driving integrated circuit IC 3 as a gate line driver, and a source driving IC as a data line driver.
  • the liquid crystal panel 1 includes a pixel region 11 located in a central region and a peripheral region around the pixel region 11, and an array of a plurality of rows and a plurality of columns of pixels is disposed in the pixel region 11.
  • the liquid crystal display further includes a backlight (not shown) disposed behind the liquid crystal panel to provide a light source for display for the liquid crystal panel.
  • the backlight may include a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), an organic light emitting diode (OLED), or the like as a light emitting element, and embodiments of the present invention are not limited to the type of backlight.
  • the gate driving integrated circuit IC 3 is for applying a driving signal to each row of gate lines in the pixel array in the driving pixel region 11, thereby controlling the turning on and off of each row of pixels.
  • the source driving IC 4 is for applying a data signal to each column of data lines in the pixel array in the driving pixel region 11, thereby controlling the magnitude of the voltage on the pixel electrode in each column of pixels for display.
  • the drive circuit 2 includes a light sensitive element that detects the operational state of the backlight and a reset signal output device.
  • the photosensitive member is a photoelectric conversion sensor based on a semiconductor photoelectric effect, and examples thereof include a photodiode, a phototransistor, a photoresistor, and the like.
  • the reset signal output device may then determine whether to output a reset signal such as a gate line driver according to the input signal, for example, may include a digital or analog circuit such as a switching element, a comparison amplifier or a flip-flop, and the switching element may include, for example, a thin film transistor.
  • Three-terminal switching elements such as diode two-terminal switching elements.
  • the drive circuit 2 includes a photodiode as a photosensitive element and a P-type metal oxide semiconductor transistor (PMOS) as a reset signal output device.
  • the example may also include an amplifier that amplifies the output of the photosensitive element, such as a non-inverting amplifier.
  • 2 is a schematic diagram showing an equivalent structure of an example of a driving circuit provided in an embodiment of the present invention. As shown in FIG. 2, examples of the drive circuit 2 include a photodiode 21, a non-inverting amplifier 22, and a PMOS 23.
  • the photodiode 21 is associated with a backlight (not shown), is disposed in the pixel region 11 of the liquid crystal panel 1, and is capable of being illuminated by the emitted light of the backlight for detecting an operational state of the backlight.
  • the photodiode 21 can also be disposed at a position other than the pixel region 11 as long as it can detect the light emitted from the backlight to judge its operating state.
  • the non-inverting amplifier 22 is connected to the photodiode 21 to amplify the output signal of the photodiode 21, thereby controlling the on and off of the PMOS 23.
  • the gate of PMOS 23 is coupled to the output of non-inverting amplifier 22 for outputting a reset signal to the gate drive integrated circuit IC to turn on all gate lines.
  • the output of 21 is sufficient to drive the PMOS 23 as a reset signal output device, and the amplifier 22 is not necessary.
  • the operating state of the backlight is detected by the photodiode 21, and according to the operating state of the backlight, through the non-inverting amplifier 22
  • the on and off states of the PMOS 23 are controlled.
  • the POMS 23 outputs a reset signal to the gate drive IC to turn on all the gate lines.
  • the photodiode 21 in this embodiment may be disposed in the pixel region 11 of the liquid crystal panel 1, for example, may be disposed on the first pixel on the left side, but is not limited thereto. Since the fabrication of the photodiode 21 can employ a semiconductor process, the process of adding the photodiode 21 in the pixel region 11 is relatively easy to implement. Based on the characteristics of the photodiode itself, when it is not exposed to light, it is reversed, and the current in the driving circuit cannot pass through the photodiode 21; when it is illuminated by the light, the photodiode 21 is forward-passed, in the driving circuit Current can pass through the photodiode 21.
  • the photodiode 21 is connected to the backlight.
  • the photodiode 21 is turned on, and when the backlight is turned off, the photodiode 21 is turned off. Therefore, the photodiode 21 can be used to detect the operating state of the backlight.
  • the current or voltage variation on the photodiode 21 can be reflected by chip COF (Chip On Film; COF) technology (an integrated circuit package) and TFT substrate traces on a flexible substrate.
  • COF Chip On Film
  • TFT substrate traces on a flexible substrate.
  • the operating state of the backlight is detected to be an on state; when no current flows through the photodiode 21, it indicates When the photodiode 21 is in the off state, it is detected that the operating state of the backlight is off.
  • the non-inverting amplifier 22 can be used to control the PMOS 23 to be in an off state when the photodiode 21 is turned on, and to control the PMOS 23 to be in an on state when the photodiode 21 is turned off.
  • the COF and TFT substrate traces can detect changes in current on the photodiode 21, convert the detected change in current on the photodiode 21 into a change in voltage, and control the turn-on and turn-off of the PMOS 23 through the non-inverting amplifier 22. . As shown in FIG.
  • resistors R1 and R2 are voltage dividing resistors of the forward input terminal of the non-inverting amplifier 22
  • resistors R3 and R4 are feedback resistors
  • resistor R5 is a pull-up resistor of the drain output of the PMOS 23
  • VDD is the entire driving circuit.
  • the power supply voltage, VD is the turn-on voltage of the photodiode 21
  • VOUT is the gate input voltage of the PMOS 23.
  • VIN (VDD-VD)*R2/(R1+R2) ( 1 )
  • VOUT VIN(l+R4/R3) ( 2 )
  • V GS is the gate-source voltage of PMOS 23 and V s is the source voltage of PMOS 23.
  • V GS is the gate-source voltage of PMOS 23 and V s is the source voltage of PMOS 23.
  • V GS is the gate-source voltage of PMOS 23
  • V s is the source voltage of PMOS 23.
  • PMOS 23 in order to ensure that the PMOS 23 is turned off by the non-inverting amplifier 22 when the photodiode 21 is turned on, and when V GS is greater than the threshold voltage V GS (TH) of the PMOS, PMOS 23 can be turned off. Then, by selecting the appropriate resistances of the resistors R1, R2, R3, and R4, VOUT is greater than V GS (TH), so that the PMOS 23 is turned off by the non-inverting amplifier 22 when the backlight is turned on. When the backlight is off, the photodiode 21 is in an off state, then:
  • V GS is smaller than the threshold voltage V GS ( TH ) of the PMOS, and at this time, the PMOS 23 is turned on by the non-inverting amplifier 22 .
  • the PMOS 23 is specifically configured to output a reset signal to the gate driving IC 3 when the PMOS 23 is in an on state to turn on all gate lines on the liquid crystal panel.
  • the reset signal XON is output as the power supply voltage VDD, that is, the output is high
  • the gate drive IC 3 is controlled by the normal signal.
  • the PMOS is turned on, that is, when the PMOS is turned on, the reset signal XON is output low.
  • the PMOS 23 is in the on state, the low level of the reset signal XON is output to the gate driving IC 3, so that all the gate lines are turned on.
  • the image sticking can be eliminated when the backlight is turned off, and the low level continues until the power supply voltage VDD is turned off.
  • the resistance of the resistor R5 it is preferable to set the resistance of the resistor R5 to be 100 k or more.
  • FIG. 3 is a timing diagram of signals of a driving circuit according to an embodiment of the present invention. As shown in Figure 3, in the figure
  • VDD is the input voltage of the power module and the driver IC
  • LVDS is the display signal provided by the system to the LCD panel of the TFT-LCD
  • B/L is the backlight turn-on signal. Due to the power supply requirements of the power module and the driver IC, the rise time of VDD is between 0 and 10 ms.
  • the power module, the driver IC, and the timing controller all require an initialization time.
  • the backlight is turned on. This time generally takes more than 200ms, so the TFT is turned on.
  • the LCD module is subject to the above signal timing.
  • the signal timing is opposite to the turn-on.
  • XON normal is the timing of the output gate IC reset signal in the legacy mode. As can be seen from FIG. 3, the conventional mode is to output a reset signal when the input voltage VDD is detected to reach a certain value. While XON improvement is a timing implemented by the embodiment of the present invention, a reset signal is output when it is detected that the backlight is off.
  • the working state of the backlight is detected by the photodiode, and according to the working state of the backlight, through the in-phase amplifier pair
  • the on and off states of the PMOS are controlled.
  • the POMS outputs a reset signal to the gate driving IC to turn on all the gate lines, thereby solving the residual image problem in the screen displayed by the LCD in the prior art. , improve the display performance of the liquid crystal display.
  • the embodiment of the present invention further provides a driving method.
  • the driving method of the embodiment can be executed by using the driving circuit provided by the embodiment of the present invention to complete the corresponding process.
  • the driving method of the embodiment of the present invention includes: providing a liquid crystal panel with a photosensitive element to detect an operating state of the backlight; according to the working state of the backlight, the reset signal output device outputs a reset signal to the gate line driver of the liquid crystal panel, To turn on all the gate lines on the LCD panel.
  • the photosensitive member include a photodiode, a phototransistor, a photoresistor, and the like.
  • the reset signal output device can then determine whether to output a reset signal such as a gate line driver based on the input signal, for example, by comparing a digital or analog circuit such as an amplifier or a flip-flop.
  • Step 401 The working state of the backlight is detected by a photodiode disposed in a pixel area of the liquid crystal panel.
  • the photodiode 21 when the photodiode is turned on, detecting that the operating state of the backlight is an on state; when the photodiode is turned off, detecting that the operating state of the backlight is off.
  • the photodiode 21 when the backlight is turned on, the photodiode 21 is turned on, and when the backlight is turned off, the photodiode 21 is turned off. Therefore, the photodiode 21 can be used to detect the operating state of the backlight.
  • current changes on the photodiode 21 can be detected by COF and TFT substrate traces, as photodiodes When there is a current passing through 21, indicating that the photodiode 21 is in an on state, it is detected that the operating state of the backlight is in an on state; when no current flows through the photodiode 21, indicating that the photodiode 21 is in an off state, the backlight is detected. The working state of the source is off.
  • Step 402 Control, according to an operating state of the backlight, a conduction and an off state of a P-type MOS transistor PMOS through a non-inverting amplifier connected to the photodiode, the gate of the PMOS and the in-phase The outputs of the amplifiers are connected.
  • the PMOS when it is detected that the backlight is turned on, the PMOS is controlled to be in an off state by the non-inverting amplifier; when the backlight is detected to be off, the PMOS is controlled to be in an on state by the non-inverting amplifier.
  • the photodiode 21 when the backlight is turned on, the photodiode 21 is in an on state, and the relationship shown by the above formulas (1) and (2) is obtained.
  • the source of the PMOS 23 is grounded, that is, V s .
  • V s When it is 0, the relational expression shown by the above formula (3) is obtained.
  • the PMOS 23 is turned off by the non-inverting amplifier 22 when the backlight is turned on.
  • VOUT is 0, V GS is smaller than the PMOS threshold voltage V GS ( TH ), and the PMOS 23 is controlled to be turned on by the non-inverting amplifier 22 at this time.
  • Step 403 outputting a reset signal to the gate driving integrated circuit IC through the PMOS to turn on all the gate lines.
  • a reset signal is output to the gate driving IC through the PMOS to turn on all gate lines by the reset signal.
  • the reset signal XON is output as the power supply voltage VDD, that is, the output is high.
  • the reset signal XON output is low.
  • the PMOS 23 is in the on state, the low level of the reset signal XON is output to the gate driving IC, so that all the gate lines are turned on, so that the image sticking can be eliminated when the backlight is turned off.
  • the resistance of the resistor R5 it is preferable to set to be 100k or more.
  • the technical solution of the embodiment is to set a photodiode, a non-inverting amplifier and a PMOS in the driving circuit, and the working state of the backlight is detected by the photodiode, and the PMOS is turned on and off by the non-inverting amplifier according to the working state of the backlight.
  • the state is controlled.
  • the POMS outputs a reset signal to the gate driving IC to turn on all the gate lines, thereby solving the residual image problem existing in the screen displayed by the LCD in the prior art, and improving the liquid crystal display. Display performance.

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Description

驱动电路及其驱动方法和液晶显示器 技术领域
本发明涉及一种驱动电路及其驱动方法和液晶显示器。 背景技术
液晶显示器是目前常用的平板显示器，其中薄膜晶体管液晶显示器（ Thin Film Transistor Liquid Crystal Display, TFT-LCD )是液晶显示器中的主流产 品。 随着 LCD产业的发展， 目前大尺寸 LCD产品逐渐成为市场的主流， 而 LCD尺寸的增加会导致数据线和栅线的电阻和电容增加。 由于电阻电容的延 迟问题， 在关机时在画面中会出现残影现象。
在现有技术中，通过釆用带重置功能的电源模块或独立的具有重置功能 的芯片， 来消除 LCD画面中出现的残影现象。 这些装置主要对 TFT-LCD的 输入电压进行检测。 当输入电压小于芯片内部的一个参考电压时， 向栅极驱 动集成电路（Integrated Circuit; IC )输出重置信号， 将栅极驱动 IC的所有 输出电压拉升到栅极开启电压， 将相应的像素的薄膜晶体管的栅极打开， 实 现消除残影的功能。
然而，残影现象主要存在的时间为背光源关闭之后，输入信号关闭之前 的时间段内。 根据一般产品的特性， 在背光源关闭之后 200ms以上才关闭输 入信号， 然后再关闭输入电压。 因此， 釆用现有技术的方法在背光源关闭之 后的 200ms之内仍有可能出现残影。 而且， 在现有技术的方法中， 由于检测 输入电压降低到某一个值才输出重置信号， 而且此时的输入电压仍处于使得 电源模块和驱动 IC 工作的一种临界状态， 并且输出电压下降时间一般为 0~10ms (电源模块和栅极驱动 IC的工作状态都处于一种临界状态） ， 因此 TFT-LCD的像素电容和存储电容不能迅速放电， 使得残影不能迅速地消除。 发明内容
本发明的实施例提供一种驱动电路及其驱动方法和液晶显示器， 以实现 在背光源关闭的同时进行残影消除， 提高了液晶显示器的显示性能。 本发明的一实施例提供了一种用于液晶显示器的驱动电路， 包括： 光敏 元件， 设置在所述液晶显示器的液晶面板上， 检测所述液晶显示器的背光源 的工作状态； 重置信号输出装置， 接收来自所述光敏元件根据所述背光源的 工作状态的输入信号， 输出重置信号到所述液晶显示器的栅极驱动器， 以开 启所述液晶面板上的全部栅线。
本发明的又一实施例一种液晶显示器的驱动方法， 包括： 对所述液晶显 示器的背光源的工作状态进行检测； 当检测到的所述液晶显示器的背光源关 闭时， 通过重置信号输出装置向所述液晶面板的栅线驱动器输出重置信号， 以开启所述液晶面板上的全部栅线。
本发明的再一实施例提供了一种用于液晶显示器的驱动电路， 包括： 光 敏二极管， 设置在所述液晶面板上， 用于检测所述液晶显示器的背光源的工 作状态； 同相放大器， 与所述光敏二极管相连； P型金属氧化物半导体晶体 管 （PMOS ) , 其栅极与所述同相放大器的输出端相连， 其中， 所述 PMOS 的导通和截止受所述同相放大器的控制， 从而输出重置信号到所述液晶显示 器的栅极驱动器， 以开启全部栅线。 附图说明
图 1A为本发明实施例提供的液晶显示器的俯视结构示意图；
图 1B为图 1A中驱动电路的放大结构示意图；
图 2为本发明实施例提供的驱动电路的等效结构示意图；
图 3为本发明实施例提供的驱动电路的信号时序图。 具体实施方式
为使本发明实施例的目的、 技术方案和优点更加清楚， 下面将结合本发 明实施例中的附图， 对本发明实施例中的技术方案进行清楚、 完整地描述， 显然， 所描述的实施例是本发明一部分实施例， 而不是全部的实施例。 基于 本发明中的实施例， 本领域普通技术人员在没有作出创造性劳动前提下所获 得的所有其他实施例， 都属于本发明保护的范围。
图 1A为本发明实施例的提供的液晶显示器的俯视结构示意图， 图 1B为 图 1A中驱动电路的放大结构示意图。 如图 1A和图 IB所示， 本实施例提供了一种液晶显示器， 包括液晶面板 1、 驱动电路 2、 作为栅线驱动器的栅极驱动集成电路 IC 3和作为数据线驱动 器的源极驱动 IC 4。 液晶面板 1包括位于中部区域的像素区域 11以及在像素 区域 11周围的周边区域， 像素区域 11中设置了多行和多列像素构成的阵列。 由于液晶面板不是自发光的， 所以该液晶显示器还包括设置在液晶面板之后 的背光源 （未示出） ， 从而为液晶面板提供显示用光源。 背光源可以包括冷 阴极荧光灯（CCFL ) 、 发光二极管 （LED ) 、 有机发光二极管 （OLED )等 作为发光元件，本发明的实施例不限于背光源的类型。栅极驱动集成电路 IC 3 用于向驱动像素区域 11中像素阵列中的各行栅线施加驱动信号， 从而控制各 行像素的开启与关闭。源极驱动 IC 4用于向驱动像素区域 11中像素阵列中的 各列数据线施加数据信号， 从而控制各列像素中的像素电极上电压大小以进 行显示。
在本实施中， 驱动电路 2 包括检测背光源工作状态的光敏元件以及重置 信号输出装置。 光敏元件是基于半导体光电效应的光电转换传感器， 其示例 包括光敏二极管、 光敏三极管、 光敏电阻等。 重置信号输出装置则可根据输 入的信号以确定是否输出重置例如栅线驱动器的重置信号， 例如可包括开关 元件、 比较放大器或触发器等数字或模拟电路， 开关元件可以包括例如薄膜 晶体管的三端开关元件、 比如二极管的二端开关元件等。
在驱动电路 2的一个示例包括作为光敏元件的光敏二极管和作为重置信 号输出装置的 P型金属氧化物半导体晶体管 （ P-Metal Oxide Semiconductor; PMOS )。 该示例还可以包括一个对光敏元件的输出进行放大的放大器， 例如 同相放大器。 图 2为本发明实施例的提供的驱动电路的示例的等效结构示意 图。 如图 2所示， 该驱动电路 2的示例包括光敏二极管 21、 同相放大器 22 和 PMOS 23。 光敏二极管 21与背光源（未示出）相关联， 设置在液晶面板 1 的像素区域 11中， 能够被背光源的发出的光照射到， 用于检测所述背光源的 工作状态。 该光敏二极管 21也可以设置在除像素区域 11之外的其他位置， 只要其能检测背光源发出的光从而判断其工作状态即可。 同相放大器 22与光 敏二极管 21相连以放大光敏二极管 21的输出信号， 由此控制 PMOS 23的导 通和截止。 PMOS 23的栅极与同相放大器 22的输出端相连，用于输出重置信 号到栅极驱动集成电路 IC, 以开启全部栅线。 在本示例中， 如果光敏二极管 21的输出足以驱动作为重置信号输出装置的 PMOS 23, 则放大器 22不是必 需的。
在该示例的技术方案中， 通过在驱动电路 2中设置光敏二极管 21、 同相 放大器 22和 PMOS23, 由光敏二极管 21对背光源的工作状态进行检测， 并 根据背光源的工作状态，通过同相放大器 22对 PMOS23的导通和截止状态进 行控制。 在背光源关闭时， 由 POMS23向栅极驱动 IC输出重置信号， 以开启 全部栅线。 由此， 解决了现有技术中 LCD显示的画面中存在的残影问题， 提 高了液晶显示器的显示性能。
如图 1A所示，本实施例中的光敏二极管 21可以设置在液晶面板 1的像 素区域 11中， 例如可以设置在左侧第一个像素上，但不限于此。 由于光敏二 极管 21的制作可以釆用半导体工艺， 因此在像素区域 11中增设光敏二极管 21的工艺比较容易实现。基于光敏二极管本身的特性， 当其在未受到光照照 射时， 反向截止， 驱动电路中的电流无法通过光敏二极管 21 ; 当其在被光照 照射时， 光敏二极管 21 正向导通， 驱动电路中的电流可以通过光敏二极管 21。在本实施例提供的驱动电路中， 光敏二极管 21与背光源相连， 当背光源 开启时， 光敏二极管 21导通， 当背光源关闭时， 光敏二极管 21截止。 因此， 光敏二极管 21可以用于检测背光源的工作状态。可以通过柔性基板上的芯片 COF ( Chip on Film; COF )技术（一种集成电路的封装方式）和 TFT基板 走线来反映光敏二极管 21上的电流或电压变化。 例如， 在电流变化的情形， 当光敏二极管 21上有电流通过时， 表明光敏二极管 21处于导通状态， 则检 测到背光源的工作状态为开启状态； 当光敏二极管 21上没有电流通过时，表 明光敏二极管 21处于截止状态， 则检测到背光源的工作状态为关闭状态。
在本示例中， 同相放大器 22 可以用于在光敏二极管 21 导通时， 控制 PMOS 23处于截止状态， 而在光敏二极管 21截止时， 控制 PMOS 23处于导 通状态。 例如， 通过 COF和 TFT基板走线能够检测光敏二极管 21上电流的 变化，将检测到的光敏二极管 21上的电流的变化转换为电压的变化，通过同 相放大器 22来控制 PMOS 23的导通和截止。如图 2所示， 电阻 R1和 R2为 同相放大器 22的正向输入端的分压电阻， 电阻 R3和 R4为反馈电阻， 电阻 R5为 PMOS 23的漏极输出的上拉电阻， VDD为整个驱动电路的电源电压， VD为光敏二极管 21的导通电压， VOUT为 PMOS 23的栅极输入电压。 当 背光源开启时， 光敏二极管 21处于导通状态， 则：
VIN=(VDD-VD)*R2/(R1+R2) ( 1 )
VOUT=VIN(l+R4/R3) ( 2 )
此时 , PMOS 23的源极接地 , 即 Vs为 0 , 则：
VGS=VOUT- VS=VOUT ( 3 )
其中， VGS是 PMOS23的栅极 -源极电压， Vs是 PMOS23的源极电压。 在本 示例的驱动电路的等效电路中，为保证在光敏二极管 21导通时，通过同相放 大器 22控制 PMOS 23处于截止状态，而当 VGS大于 PMOS的阔值电压 VGS(TH) 时， PMOS 23才能截止。 则本示例通过选择合适的电阻 Rl、 R2、 R3和 R4 的阻值， 使得 VOUT 大于 VGS(TH), 从而在背光源开启时， 通过同相放大器 22控制 PMOS 23截止。 而当背光源关闭时， 光敏二极管 21处于截止状态， 则：
VIN=VOUT=0 ( 4 )
则 VGS小于 PMOS的阔值电压 VGS(TH),此时通过同相放大器 22控制 PMOS 23 导通。
在本示例中， PMOS 23具体用于在 PMOS 23处于导通状态时， 向所述 栅极驱动 IC 3输出重置信号， 以开启液晶面板上的全部栅线。 根据 PMOS 的特性； 当 PMOS 23截止时， 即处于关闭状态时， 重置信号 XON输出为电 源电压 VDD , 即输出高电平， 栅极驱动 IC 3受正常信号控制。 当 PMOS导 通， 即处于打开状态时， 重置信号 XON输出为低电平。 在 PMOS 23处于导 通状态时， 将重置信号 XON的低电平输出到栅极驱动 IC 3, 使得全部的栅 线开启。 由此， 可实现在背光源关闭时即可消除残影现象， 低电平一直持续 到电源电压 VDD关闭。 为了保证在 PMOS 23处于导通状态时功耗较小， 则 最好将电阻 R5的阻值设置为 100k以上。
图 3为本发明实施例提供的驱动电路的信号时序图。 如图 3所示， 图中
VDD为电源模块和驱动 IC的输入电压， LVDS为系统提供给 TFT-LCD的液 晶面板的显示信号， B/L为背光源开启信号。 由于电源模块和驱动 IC对电源 的要求， 所以 VDD的上升时间为 0~10ms之间。在驱动电路板上存在时序控 制器主要接收 LVDS信号，通过该芯片能够控制栅极驱动 IC 3和源驱动 IC 4 的工作状态， 实现 TFT-LCD显示。 根据时序控制器的规格， 为保证显示正 常， LVDS与 VDD之间的时间为 0~50ms。 当电压 VDD和 LVDS信号都提 供的时候， 电源模块、 驱动 IC、 时序控制器都需要一个初始化的时间， 当达 到工作稳定状态的时候， 背光源开启， 这个时间一般需要 200ms以上， 因此 开启 TFT-LCD模块的时候服从上述信号时序。 而关闭的时候信号时序与开 启相反。 XON normal是传统模式下输出栅极 IC重置信号的时序。 从图 3中 可以看到， 传统模式是检测输入电压 VDD达到某一个值的时候输出重置信 号。 而 XON improvement为该本发明的实施例所实现的时序， 当检测到背光 源关闭的时候输出重置信号。
本发明实施例的上述示例的技术方案中， 通过在驱动电路中设置光敏二 极管、 同相放大器和 PMOS, 由光敏二极管对背光源的工作状态进行检测， 并根据背光源的工作状态， 通过同相放大器对 PMOS的导通和截止状态进行 控制， 在背光源关闭时， 由 POMS向栅极驱动 IC输出重置信号， 以开启全部 栅线， 解决了现有技术中 LCD显示的画面中存在的残影问题， 提高了液晶显 示器的显示性能。
本发明的实施例还提供了一种驱动方法， 本实施例的驱动方法可以釆用 本发明实施例所提供的驱动电路来执行， 完成对应的流程。 本发明实施例的 驱动方法包括为液晶面板提供一个光敏元件对背光源的工作状态进行检测； 根据所述背光源的工作状态， 重置信号输出装置向液晶面板的栅线驱动器输 出重置信号， 以开启液晶面板上的全部栅线。 光敏元件的示例包括光敏二极 管、 光敏三极管、 光敏电阻等。 重置信号输出装置则可根据输入的信号以确 定是否输出重置例如栅线驱动器的重置信号， 例如可通过比较放大器或触发 器等数字或模拟电路来实现。
本实施例提供的驱动方法的一个示例可以包括如下步骤：
步骤 401 ,通过设置在液晶面板的像素区域中的光敏二极管对背光源的工 作状态进行检测。
具体地， 在所述光敏二极管导通时， 检测到所述背光源的工作状态为开 启状态； 在所述光敏二极管截止时， 检测到所述背光源的工作状态为关闭状 态。 当背光源开启时， 光敏二极管 21导通， 当背光源关闭时， 光敏二极管 21 截止。 因此， 光敏二极管 21可以用于检测背光源的工作状态。 例如， 可以通 过 COF和 TFT基板走线来检测光敏二极管 21上的电流变化， 当光敏二极管 21上有电流通过时，表明光敏二极管 21处于导通状态， 则检测到背光源的工 作状态为开启状态； 当光敏二极管 21上没有电流通过时，表明光敏二极管 21 处于截止状态， 则检测到背光源的工作状态为关闭状态。
步骤 402,根据所述背光源的工作状态，通过与所述光敏二极管相连的同 相放大器对 P型金属氧化物半导体晶体管 PMOS的导通和截止状态进行控制， 所述 PMOS的栅极与所述同相放大器的输出端相连。
具体地， 在检测到所述背光源开启时， 通过同相放大器控制 PMOS处于 截止状态； 在检测到所述背光源关闭时， 通过同相放大器控制 PMOS处于导 通状态。 参照图 2所示， 当背光源开启时， 光敏二极管 21处于导通状态， 则 得到上述公式（ 1 )和（2 )所示的关系式， 此时， PMOS 23的源极接地， 即 Vs为 0, 则得到上述公式（3 )所示的关系式。 本实施例通过选择合适的电阻 Rl、 R2、 R3和 R4的阻值， 使得 VOUT大于 VGS(TH), 从而在背光源开启时， 通过同相放大器 22控制 PMOS 23截止。 而当背光源关闭时， 光敏二极管处 于截止状态， 则 VOUT为 0, VGS小于 PMOS的阔值电压 VGS(TH), 此时通过 同相放大器 22控制 PMOS 23导通。
步骤 403, 通过所述 PMOS向栅极驱动集成电路 IC输出重置信号， 以开 启全部栅线。
具体地， 在所述 PMOS处于导通状态时， 通过所述 PMOS向所述栅极驱 动 IC输出重置信号， 以由所述重置信号开启全部栅线。 根据 PMOS的特性， 当 PMOS截止， 即处于关闭状态时， 重置信号 XON输出为电源电压 VDD, 即输出高电平。 当 PMOS导通， 即处于打开状态时， 重置信号 XON输出为 低电平。 在 PMOS 23处于导通状态时， 将重置信号 XON的低电平输出到栅 极驱动 IC,使得全部的栅线开启， 以实现在背光源关闭时即可消除残影现象。 为了保证在 PMOS处于导通状态时功耗较小， 则最好将电阻 R5的阻值设置 为 100k以上。
本实施例的技术方案通过在驱动电路中设置光敏二极管、 同相放大器和 PMOS, 由光敏二极管对背光源的工作状态进行检测， 并根据背光源的工作状 态，通过同相放大器对 PMOS的导通和截止状态进行控制，在背光源关闭时， 由 POMS向栅极驱动 IC输出重置信号， 以开启全部栅线，解决了现有技术中 LCD显示的画面中存在的残影问题， 提高了液晶显示器的显示性能。 最后应说明的是： 以上实施例仅用以说明本发明的技术方案， 而非对其 限制； 尽管参照前述实施例对本发明进行了详细的说明， 本领域的普通技术 人员应当理解： 其依然可以对前述各实施例所记载的技术方案进行修改， 或 者对其中部分技术特征进行等同替换； 而这些修改或者替换， 并不使相应技 术方案的本质脱离本发明各实施例技术方案的精神和范围。

Claims

权利要求书
1、 一种用于液晶显示器的驱动电路， 包括：
光敏元件， 设置在所述液晶显示器的液晶面板上， 检测所述液晶显示器 的背光源的工作状态； 和
重置信号输出装置， 接收来自所述光敏元件根据所述背光源的工作状态 的输入信号， 输出重置信号到所述液晶显示器的栅极驱动器， 以开启所述液 晶面板上的全部栅线。
2、根据权利要求 1所述的驱动电路， 其中， 所述光敏元件包括光敏二极 管、 光敏三极管或光敏电阻。
3、根据权利要求 2所述的驱动电路， 其中， 所述光敏二极管导通时， 检 测到所述背光源的工作状态为开启状态， 在所述光敏二极管截止时， 检测到 所述背光源的工作状态为关闭状态。
4、根据权利要求 1所述的驱动电路， 其中， 所述光敏元件设置在所述液 晶面板的像素区域之中。
5、根据权利要求 1所述的驱动电路， 其中， 所述重置信号输出装置包括 开关元件、 比较放大器或触发器。
6、根据权利要求 5所述的驱动电路， 其中， 所述开关元件包括二端开关 元件或三端开关元件。
7、根据权利要求 6所述的驱动电路， 其中， 所述三端开关元件包括薄膜 晶体管 , 且所述薄膜晶体管的栅极接受所述光敏元件的输出信号。
8、 根据权利要求 1所述的驱动电路， 还包括：
放大器， 与所述光敏元件相连， 用于放大所述光敏元件输出到所述重置 信号输出装置的输入信号。
9、 一种液晶显示器的驱动方法， 包括：
对所述液晶显示器的背光源的工作状态进行检测；
当检测到的所述液晶显示器的背光源关闭时， 通过重置信号输出装置向 所述液晶面板的栅线驱动器输出重置信号， 以开启所述液晶面板上的全部栅 线。
10、 根据权利要求 9所述的驱动方法， 其中， 通过设置在所述液晶显示 器的液晶面板上的光敏元件对背光源的工作状态进行检测。
11、根据权利要求 10所述的驱动方法， 其中， 所述光敏元件设置在所述 液晶面板的像素区域之中， 从而检测所述液晶显示器的背光源的工作状态。
12、根据权利要求 11所述的驱动方法， 其中， 所述光敏元件在检测到的 所述液晶显示器的背光源关闭时， 向所述重置信号输出装置输出控制信号。
13、根据权利要求 12所述的驱动方法， 其中， 所述从光敏元件输出的控 制信号被放大， 然后再被输入到所述重置信号输出装置。
14、 一种液晶显示器， 包括液晶面板、 驱动电路、 栅极驱动器和源极驱 动器， 其中， 所述驱动电路包括权利要求 1所述的驱动电路。
15、 一种用于液晶显示器的驱动电路， 包括：
光敏二极管， 设置在所述液晶面板上， 用于检测所述液晶显示器的背光 源的工作状态；
同相放大器， 与所述光敏二极管相连； 和
P型金属氧化物半导体晶体管 （PMOS ) ， 其栅极与所述同相放大器的 输出端相连，
其中， 所述 PMOS的导通和截止受所述同相放大器的控制， 从而输出重 置信号到所述液晶显示器的栅极驱动器， 以开启全部栅线。
PCT/CN2011/072466 2010-04-23 2011-04-06 驱动电路及其驱动方法和液晶显示器 WO2011131086A1 (zh)

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