WO2014131201A1 - 一种背光调光电路及其调光方法、液晶显示器 - Google Patents

一种背光调光电路及其调光方法、液晶显示器 Download PDF

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Publication number
WO2014131201A1
WO2014131201A1 PCT/CN2013/072179 CN2013072179W WO2014131201A1 WO 2014131201 A1 WO2014131201 A1 WO 2014131201A1 CN 2013072179 W CN2013072179 W CN 2013072179W WO 2014131201 A1 WO2014131201 A1 WO 2014131201A1
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Prior art keywords
inverting input
signal
voltage
comparator
input terminal
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PCT/CN2013/072179
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English (en)
French (fr)
Inventor
杨翔
陈辛洪
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深圳市华星光电技术有限公司
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Priority to US13/878,226 priority Critical patent/US8829807B1/en
Publication of WO2014131201A1 publication Critical patent/WO2014131201A1/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
    • 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
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • 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

Definitions

  • the present invention relates to the field of image display, and in particular to a backlight dimming circuit, a dimming method thereof, and a liquid crystal display.
  • the main theme of the industry is green energy conservation and environmental protection.
  • large-size LCD monitors need to be energy-saving.
  • the power of the whole machine is 120W
  • the power of the backlight is about 60W, which accounts for 50% of the power of the whole machine. Therefore, in the green energy saving of products, the energy saving of backlights will play an important role.
  • a variety of technologies are currently available to achieve energy savings by adjusting backlight brightness in a variety of ways.
  • the first is manual dimming, which is manually adjusted by the user through the operating menu.
  • This kind of scheme is not intelligent, and the manual adjustment causes the operation to be cumbersome; in addition, since the brightness of the screen changes frequently, the manual adjustment is not real-time.
  • the second type is ambient light-induced dimming, that is, relying on an ambient light sensor such as a photodiode or a transistor to sense the brightness of the surrounding light, converting the brightness perceived by the light sensor into a current or a voltage, and the processor automatically adjusts the display based on the preset threshold.
  • Backlight brightness When the ambient light is strong and bright, the backlight of the liquid crystal display will automatically adjust to high brightness; when the external environment is dark, the backlight of the liquid crystal display will be adjusted to low brightness, thereby reducing the backlight power consumption.
  • this solution needs to be based on the perception of the ambient light brightness of the light sensor, the real-time performance is not strong, the response speed is slow, and the hardware support such as MCU is required, and the cost is high.
  • the third type is Local Dimming, which divides the entire picture into several regions in a matrix.
  • the MCU analyzes and calculates the brightness of each area, and then independently controls the brightness of each area.
  • This solution also requires hardware support such as MCU, and the more partitions the LED driver makes The more you use, the more complex the algorithm and timing control, which greatly increases the cost of the whole machine.
  • the technical problem to be solved by the present invention is to provide a backlight dimming circuit with low cost and high real-time performance, a dimming method thereof, and a liquid crystal display.
  • the present invention provides a backlight dimming circuit, which includes: a power supply voltage terminal VCC for supplying a power supply voltage; an operational amplifier Q having a non-inverting input terminal connected to a power supply voltage terminal VCC, and an inverting input terminal Connected to the load terminal; the precision resistor R is connected between the non-inverting input terminal and the inverting input terminal of the operational amplifier Q, and the differential voltage signal across the precision resistor R is converted and amplified by the operational amplifier Q into a DC DC voltage signal and output; C, the non-inverting input receives the DC DC voltage signal output from the operational amplifier Q, and the inverting input receives the sawtooth signal from the boost IC in the boost converter for use in the DC DC voltage signal and the boost IC The sawtooth signal is compared, and a pulse width modulated PWM dimming signal is output according to the comparison result.
  • the DC DC voltage is the input voltage VIN+ of the non-inverting input of the comparator C
  • the sawtooth wave of the boost IC is the input voltage VIN - of the inverting input of the comparator C.
  • the comparator C when VIN+ is greater than VIN-, the comparator C outputs a PWM dimming signal with a large duty ratio for increasing the backlight brightness; when VIN+ is less than VIN-, the comparator C outputs a PWM dimming signal having a small duty ratio. , used to reduce the brightness of the backlight.
  • the resistance of the precision resistor R is less than or equal to 0.1 ohm.
  • the invention further provides a dimming method for a backlight dimming circuit
  • the backlight dimming circuit comprises: a power supply voltage terminal VCC; an operational amplifier Q, the non-inverting input terminal is connected to the power supply voltage terminal VCC, and the inverting input terminal is connected to the load terminal; a precision resistor R connected between the non-inverting input terminal and the inverting input terminal of the operational amplifier Q; and a comparator C having a non-inverting input terminal connected to the output terminal of the operational amplifier Q, and an inverting input terminal connected to the boosting IC;
  • the light method comprises the following steps: converting the differential pressure signal across the precision resistor R by the operational amplifier Q into a DC voltage signal and outputting it to the comparator C; the DC voltage signal of the DC voltage signal and the boosting IC of the boosting IC are compared by the comparator C.
  • the present invention further provides a liquid crystal display, comprising: a backlight dimming circuit, the backlight dimming circuit further comprising: a power supply voltage terminal VCC for supplying a power supply voltage; an operational amplifier Q having a non-inverting input terminal connected to the power supply voltage terminal VCC, The inverting input terminal is connected to the load end; the precision resistor R is connected between the non-inverting input terminal and the inverting input terminal of the operational amplifier Q, and the differential voltage signal across the precision resistor R is converted and converted into a DC DC voltage signal by the operational amplifier Q and Output; and comparator C, the non-inverting input receives the DC DC voltage signal output from the operational amplifier Q, and the inverting input receives the sawtooth signal from the boost IC in the boost converter for use in the DC DC voltage signal The sawtooth signals of the boost IC are compared, and a pulse width modulated PWM dimming signal is output according to the comparison result.
  • the DC DC voltage is the input voltage VIN+ of the non-inverting input of the comparator C
  • the sawtooth wave of the boost IC is the input voltage VIN - of the inverting input of the comparator C.
  • the comparator C when VIN+ is greater than VIN-, the comparator C outputs a PWM dimming signal with a large duty ratio for increasing the backlight brightness; when VIN+ is less than VIN-, the comparator C outputs a PWM dimming signal having a small duty ratio. , used to reduce the brightness of the backlight.
  • the resistance of the precision resistor R is less than or equal to 0.1 ohm.
  • the backlight dimming circuit, the dimming method thereof and the liquid crystal display provided by the invention have simple structure, do not affect the original circuit structure and scheme, and have low cost input; the backlight brightness is associated with the picture in real time, and the data of other existing solutions are reduced. Conversion and data transmission, real-time detection, real-time backlight response, reduce backlight power consumption, and promote product energy saving.
  • FIG. 1 is a schematic structural diagram of a backlight dimming circuit according to an embodiment of the present invention.
  • 2 is a schematic flow chart of a dimming method of a backlight dimming circuit according to Embodiment 2 of the present invention. detailed description
  • the embodiment of the present invention is mainly based on two aspects: First, considering that the display of the liquid crystal panel is a charging-storage process, the brightness of the screen is proportional to the current, and the brightness of the screen is The higher the voltage difference is, the larger the current is drawn. Accordingly, by using the magnitude of the current drawn as the measurement object, the brightness and darkness of the picture can be determined in real time according to the current magnitude. Further, the brightness and darkness of the real-time picture can be known according to the change of the current size.
  • PWM Pulse Width Modulation
  • the dimming signal controls the brightness of the backlight to achieve dimming.
  • the specific implementation requires low-cost input, directly adding lines to the original circuit, and does not affect the original circuit architecture and solution.
  • a backlight dimming circuit uses a conventional DC conversion circuit (DC-DC loop) to connect a precision resistor R, which flows through the precision resistor R when the screen changes. The current will change accordingly.
  • the precision resistor R detects the change of the current to know the change of the brightness and darkness of the picture, and then performs the targeted dimming.
  • an embodiment of the present invention - a backlight dimming circuit includes:
  • the power supply voltage terminal VCC is used to supply the supply voltage
  • the operational amplifier Q has its non-inverting input terminal connected to the power supply voltage terminal VCC, and the inverting input terminal is connected to the load terminal;
  • the precision resistor R is connected between the non-inverting input terminal and the inverting input terminal of the operational amplifier Q, and the differential voltage signal across the precision resistor R is converted and amplified by the operational amplifier Q into a DC DC voltage signal and output;
  • the non-inverting input receives the DC-DC voltage signal output from the operational amplifier Q
  • the inverting input receives the sawtooth signal from the boost IC in the boost converter for boosting the DC-DC voltage signal
  • the sawtooth signals of the IC are compared, and the PWM dimming signal is output according to the comparison result.
  • the precision resistor R since the precision resistor R is connected, in order to reduce the loss caused by it, the value should be as small as possible. In this embodiment, the resistance is less than or equal to 0.1 ohm.
  • the working principle of the backlight dimming circuit of this embodiment is as follows: the brightness and PWM of the picture
  • the current drawn by the IC from the power supply voltage terminal VCC (12V) (that is, the current flowing through the precision resistor R) is proportional to the low-load (low loading), pure white pattern (in the black pattern).
  • White pattern is overloaded ( high loading ).
  • the aforementioned proportional relationship can be used with a gray
  • I Imin+ - fx ( Imax-Imin ), where Imin is the current at the low loading screen, gray is the gray level of the current picture, and Imax is the current at the high loading screen. .
  • Imin is the current at the low loading screen
  • gray is the gray level of the current picture
  • Imax is the current at the high loading screen.
  • the DC voltage signal VDC1 is outputted by the conversion of the operational amplifier Q, and the DC voltage signal VDC1 is compared.
  • the C input signal of the non-inverting input is VIN+, and the sawtooth signal of the boost IC is used as the input voltage VIN- of the inverting input of the comparator C.
  • VIN+ is greater than VIN-, the comparator C will output a high-level (high) PWM. Dimming signal (large duty ratio), increase backlight brightness; conversely, if VIN+ is less than VIN-, comparator C will output low-level (low) PWM dimming signal (small duty cycle), turn down the backlight Brightness. Realizes the real-time correlation between the current picture brightness and the PWM dimming signal, enabling real-time dimming without dimming delay
  • the associated PWM dimming signal is output in real time according to the same principle.
  • the pictures P1 and P2 are pictures of adjacent frames, the light and dark changes of the picture will be involved. For example, when the picture P1 is a dark picture and the picture P2 is a bright picture, that is, when the current picture is darkened, the current flowing through the precision resistor R becomes larger, and the voltage difference between the two ends becomes correspondingly larger, which is converted by the amplifier Q.
  • the DC voltage signal VDC VIN+
  • Comparator C outputs a high-level (high) PWM dimming signal with a large duty cycle to increase the brightness of the picture. Also: 3 ⁇ 4 port, when the picture P1 is a bright picture and the picture P2 is a dark picture, that is, when the current picture is turned from dark to dark, the current flowing through the precision resistor R becomes smaller, and the voltage difference between the two ends becomes smaller, and is converted by the amplifier Q.
  • the obtained DC DC voltage signal VDC ( VIN+ ) is also reduced, which is smaller than the sawtooth signal (VIN-) of the boost IC, and the comparator C output duty cycle becomes a low level (low) PWM dimming signal, which will The picture brightness is reduced.
  • the second embodiment of the present invention provides a dimming method for a backlight dimming circuit.
  • the backlight dimming circuit includes: a power supply voltage terminal VCC; an operational amplifier Q whose non-inverting input terminal is connected to a power supply voltage terminal VCC.
  • the phase input terminal is connected to the load terminal;
  • the precision resistor R is connected between the non-inverting input terminal and the inverting input terminal of the operational amplifier Q;
  • the comparator C has its non-inverting input terminal connected to the output terminal of the operational amplifier Q, and the inverting input
  • the terminal is connected to the boost IC; and then, as shown in FIG. 2, the dimming method includes the following steps:
  • the differential voltage signal across the precision resistor R is converted by the operational amplifier Q into a DC DC voltage signal and output to the comparator C;
  • the comparator C if the DC DC voltage signal is greater than the sawtooth signal of the boost IC, the comparator C outputs a high-level PWM dimming signal (large duty ratio) to increase the backlight brightness; otherwise, if DC When the DC voltage signal is smaller than the sawtooth signal of the boost IC, the comparator C will output a low-level (low) PWM dimming signal (small duty cycle) to lower the backlight brightness.
  • a third embodiment of the present invention provides a liquid crystal display, including the backlight dimming circuit provided in Embodiment 1.
  • the backlight dimming circuit provided in Embodiment 1.
  • the related working principle of the backlight dimming circuit will not be described here.
  • the backlight dimming circuit and the dimming method thereof and the liquid crystal display respectively provided by the embodiments of the present invention have a simple structure, do not affect the original circuit architecture and the scheme, and have low cost input; the backlight brightness is associated with the picture in real time, and other existing solutions are reduced. Data conversion and data transmission, real-time detection, real-time backlight response, reduce backlight power consumption, and promote product energy saving.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Liquid Crystal (AREA)

Abstract

一种背光调光电路及其调光方法、液晶显示器，其中背光调光电路包括：电源电压端（VCC），用于提供供电电压；运算放大器（Q），其同相输入端与电源电压端（VCC）相连，反相输入端与负载端相连；精密电阻（R），连接在运算放大器（Q）的同相输入端和反相输入端之间，精密电阻（R）两端的压差信号由运算放大器（Q）转换放大为直流（DC）电压信号并输出；以及比较器（C），其同相输入端接收运算放大器（Q）输出的直流（DC）电压信号，反相输入端接收来自升压转换器内的升压（IC）的锯齿波信号，用于将直流（DC）电压信号与升压（IC）的锯齿波信号进行比较，并根据比较结果输出PWM调光信号。该背光调光电路结构简单，成本投入较低；背光亮度与画面实时关联，降低背光功耗，促进产品节能化。

Description

一种背光调光电路及其调光方法、 液晶显示器
本申请要求于 2013 年 2 月 26 日提交中国专利局、 申请号为 201310059850.4、 发明名称为 "一种背光调光电路及其调光方法、 液晶显示 器" 的中国专利申请的优先权， 上述专利的全部内容通过引用结合在本申请 中。 技术领域
本发明涉及图像显示领域， 尤其涉及一种背光调光电路及其调光方法、 液晶显示器。
背景技术
目前业界主推的主题是绿色节能环保， 大尺寸液晶显示器尤其需要做到 节能， 以 48寸为例， 整机功率 120W, 其中背光的功率约 60W, 占整机功 率的 50%。 所以在产品绿色节能化中， 背光的节能将扮演重要角色。 目前已 有多种技术通过各种方式调节背光亮度实现节能。
第一种为手动调光， 即用户通过操作菜单手动调节。 这种方案不智能， 手动调节导致操作繁瑣； 另外， 由于画面明暗时常变化， 手动调节也不具有 实时性。
第二种为环境光感应调光， 即依靠光电二极管或晶体管等环境光传感器 感知周围光线亮度情况， 将光传感器感知的光亮度转变成电流或电压， 由处 理器基于预设的阈值自动调节显示器背光亮度。 当环境光线强亮度高时， 液 晶显示器背光会自动调成高亮度； 当外界环境较暗时， 液晶显示器背光就会 调成低亮度， 以此来降低背光功耗。 但是， 这种方案需要以光传感器对周围 环境光线亮度的感知为前提， 实时性不强， 响应速度慢； 并且需要 MCU等 硬件支持， 成本较高。
第三种为区域调光（Local Dimming ), 即将整个画面按矩阵式分成若干 个区域， MCU根据各区域画面亮度进行分析计算， 然后对各区域背光亮度 独立控制。这种方案也同样需要 MCU等硬件支持，且分区越多 LED驱动使 用越多， 算法和时序控制越复杂， 这大大增加了整机的成本。
由上可知， 提供一种成本低、 实时性强的背光调光方案， 是业界不断努 力的目标。
发明内容
本发明所要解决的技术问题在于， 提供一种成本低、 实时性强的背光调 光电路及其调光方法、 液晶显示器。
为了解决上述技术问题， 本发明提供一种背光调光电路， 其中， 包括： 电源电压端 VCC, 用于提供供电电压； 运算放大器 Q, 其同相输入端与电源 电压端 VCC相连， 反相输入端与负载端相连； 精密电阻 R, 连接在运算放 大器 Q的同相输入端和反相输入端之间， 精密电阻 R两端的压差信号由运 算放大器 Q转换放大为直流 DC电压信号并输出； 以及比较器 C, 其同相输 入端接收运算放大器 Q输出的直流 DC电压信号，反相输入端接收来自升压 转换器内的升压 IC的锯齿波信号， 用于将直流 DC电压信号与升压 IC的锯 齿波信号进行比较， 并根据比较结果输出脉宽调制 PWM调光信号。
其中， 直流 DC电压为比较器 C的同相输入端输入电压 VIN+, 升压 IC 的锯齿波为比较器 C的反相输入端输入电压 VIN -。
其中，当 VIN+大于 VIN-时，比较器 C输出占空比大的 PWM调光信号， 用于调高背光亮度； 当 VIN+小于 VIN-时， 比较器 C输出占空比小的 PWM 调光信号， 用于调低背光亮度。
其中， 精密电阻 R的阻值小于等于 0.1欧姆。
本发明又提供一种背光调光电路的调光方法， 背光调光电路包括： 电源 电压端 VCC; 运算放大器 Q, 其同相输入端与电源电压端 VCC相连， 反相 输入端与负载端相连； 精密电阻 R, 连接在运算放大器 Q的同相输入端和反 相输入端之间；以及比较器 C,其同相输入端与运算放大器 Q的输出端相连， 反相输入端与升压 IC相连； 调光方法包括以下步骤： 将精密电阻 R两端的 压差信号由运算放大器 Q转换放大为直流 DC电压信号并输出至比较器 C; 由比较器 C将直流 DC电压信号与升压 IC的锯齿波信号进行比较， 并根据 比较结果输出脉宽调制 PWM调光信号； 以及根据比较器输出的 PWM调光 信号相应调节背光亮度。 其中， 当直流 DC电压信号大于升压 IC的锯齿波信号时， 比较器 C输 出占空比大的 PWM调光信号， 进而调高背光亮度； 当直流 DC电压信号小 于升压 IC的锯齿波信号时， 比较器 C输出占空比小的 PWM调光信号， 进 而调低背光亮度。
本发明还提供一种液晶显示器， 其中， 包括背光调光电路， 背光调光电 路进一步包括： 电源电压端 VCC, 用于提供供电电压； 运算放大器 Q, 其同 相输入端与电源电压端 VCC相连， 反相输入端与负载端相连； 精密电阻 R, 连接在运算放大器 Q的同相输入端和反相输入端之间， 精密电阻 R两端的 压差信号由运算放大器 Q转换放大为直流 DC电压信号并输出；以及比较器 C, 其同相输入端接收运算放大器 Q输出的直流 DC电压信号， 反相输入端 接收来自升压转换器内的升压 IC的锯齿波信号， 用于将直流 DC电压信号 与升压 IC的锯齿波信号进行比较， 并根据比较结果输出脉宽调制 PWM调 光信号。
其中， 直流 DC电压为比较器 C的同相输入端输入电压 VIN+, 升压 IC 的锯齿波为比较器 C的反相输入端输入电压 VIN -。
其中，当 VIN+大于 VIN-时，比较器 C输出占空比大的 PWM调光信号， 用于调高背光亮度； 当 VIN+小于 VIN-时， 比较器 C输出占空比小的 PWM 调光信号， 用于调低背光亮度。
其中， 精密电阻 R的阻值小于等于 0.1欧姆。
本发明所提供的背光调光电路及其调光方法、 液晶显示器， 结构简单， 不影响原有电路架构和方案， 成本投入较低； 背光亮度与画面实时关联， 减 少了其它现有方案的数据换算和数据传输， 实现实时侦测， 背光实时响应， 降低背光功耗， 促进产品节能化。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案， 下面将对实 施例或现有技术描述中所需要使用的附图作简单地介绍， 显而易见地， 下面 描述中的附图仅仅是本发明的一些实施例， 对于本领域普通技术人员来讲， 在不付出创造性劳动的前提下， 还可以根据这些附图获得其他的附图。
图 1是本发明实施例一一种背光调光电路的结构示意图。 图 2是本发明实施例二一种背光调光电路的调光方法的流程示意图。 具体实施方式
下面参考附图对本发明的优选实施例进行描述。
为实现成本低、实时性强的背光调光，本发明实施例主要基于两个方面： 一是考虑到液晶面板的显示是充电——储能的过程， 画面亮度与电流成正比 例关系， 画面亮度越高， 需要的电压差就越大， 整体抽载的电流就越大。 据 此， 将这个抽载的电流大小作为量测对象， 便可根据电流大小实时判定画面 的亮暗， 进一步地， 还可根据电流大小的变化获知实时画面的亮暗变化。 另 一方面， 得到画面的实时亮度情况后， 还需将其与 PWM ( Pulse Width Modulation, 脉宽调制）调光信号相关联， 由该调光信号控制背光亮度， 实 现调光。 当然， 具体实现时需要低成本投入， 直接在原有电路上增加线路， 不影响原有电路架构和方案。
请参照图 1所示，本发明实施例一一种背光调光电路利用现有直流变换 电路 ( DC-DC回路）， 接入一颗精密电阻 R, 当画面变化时从精密电阻 R流 过的电流将发生相应变化，通过该精密电阻 R侦测电流的变化从而获知画面 亮暗的变化， 进而进行针对性地调光。
具体地， 本发明实施例——种背光调光电路包括：
电源电压端 VCC, 用于提供供电电压；
运算放大器 Q, 其同相输入端与电源电压端 VCC相连， 反相输入端与 负载端相连；
精密电阻 R, 连接在运算放大器 Q的同相输入端和反相输入端之间，精 密电阻 R两端的压差信号由运算放大器 Q转换放大为直流 DC电压信号并输 出；
比较器 C, 其同相输入端接收运算放大器 Q输出的直流 DC电压信号， 反相输入端接收来自升压转换器内的升压 IC的锯齿波信号， 用于将该直流 DC电压信号与升压 IC的锯齿波信号进行比较， 并根据比较结果输出 PWM 调光信号。
需要说明的是， 由于接入了精密电阻 R, 为了降低其带来的损耗， 其取 值应尽可能小， 本实施例中其阻值小于等于 0.1欧姆。 本实施例的背光调光电路的工作原理是： 如前所述， 画面的亮度与 PWM
IC从电源电压端 VCC ( 12V )抽载的电流（也就是流经精密电阻 R的电流 ) 成正比例关系， 其中在纯黑图案 ( black pattern ) 时为轻载 ( low loading ), 纯白图案 （ white pattern ) 为重载（ high loading )。 前述正比例关系可以用一 gray
公式简单表示为： I=Imin+ - f x ( Imax-Imin ), 其中 Imin为轻载（ low loading )画面时的电流， gray为当前画面的灰阶， Imax为重载（ high loading ) 画面时的电流。 個没显示当前画面 P1时， 流经^ "密电阻 R的电流为 II , 其 两端的压差为 VI ,通过运算放大器 Q的转换，输出直流 DC电压信号 VDC1 , 该直流 DC电压信号 VDC1作为比较器 C同相输入端输入电压 VIN+, 而升 压 IC的锯齿波信号作为比较器 C反相输入端输入电压 VIN-, 如果 VIN+大 于 VIN-, 则比较器 C将输出高电平（high )的 PWM调光信号 (占空比大）， 调高背光亮度；反之，如果 VIN+小于 VIN-,则比较器 C将输出低电平（low ) 的 PWM调光信号 （占空比小）， 调低背光亮度。 由此实现了当前画面亮度 与 PWM 调光信号的实时关联， 可实现实时的调光， 不会出现调光延迟
( delay )。 例如， 如果画面 P1为暗画面 , 流经^ "密电阻 R的电流 II比较小 , 经放大器 Q转换得到的直流 DC电压信号 VDC1 ( VIN+ )也会比较小， 在 比较器 C中比较时就小于升压 IC的锯齿波信号 （VIN- ), 于是输出低电平
( low ) PWM调光信号 （占空比小）， 调低背光亮度， 节省了功耗。
同理，显示当前画面 P2时， 亦是按同样的原理实时输出相关联的 PWM 调光信号。 而如果画面 Pl、 P2为相邻帧的画面时， 将涉及画面的亮暗变化。 举例来说， 当画面 P1为暗画面、画面 P2为亮画面，即当前画面由暗变亮时， 流经精密电阻 R的电流变大， 其两端的压差相应变大， 经放大器 Q转换得 到的直流 DC电压信号 VDC ( VIN+ )也会增大， 大于升压 IC的锯齿波信号
( VIN- ), 比较器 C输出占空比变大的高电平（high ) PWM调光信号， 将画 面亮度提高。 又: ¾口， 当画面 P1为亮画面、 画面 P2为暗画面， 即当前画面由 亮变暗时， 流经精密电阻 R的电流变小， 其两端的压差相应变小， 经放大器 Q转换得到的直流 DC电压信号 VDC ( VIN+ )也会减小， 小于升压 IC的锯 齿波信号（VIN- ), 比较器 C输出占空比变小的低电平（low ) PWM调光信 号， 将画面亮度降低。 由上所述， 本发明实施例二提供一种背光调光电路的调光方法， 该背光 调光电路包括： 电源电压端 VCC; 运算放大器 Q, 其同相输入端与电源电压 端 VCC相连， 反相输入端与负载端相连； 精密电阻 R, 连接在运算放大器 Q的同相输入端和反相输入端之间； 以及比较器 C, 其同相输入端与运算放 大器 Q的输出端相连， 反相输入端与升压 IC相连； 再请参照图 2所示， 该 调光方法包括以下步骤：
S1、将精密电阻 R两端的压差信号由运算放大器 Q转换放大为直流 DC 电压信号并输出至比较器 C;
52、 由比较器 C将该直流 DC电压信号与升压 IC的锯齿波信号进行比 较， 并根据比较结果输出 PWM调光信号； 以及
53、 根据比较器输出的 PWM调光信号相应调节背光亮度。
具体地，如果直流 DC电压信号大于升压 IC的锯齿波信号，则比较器 C 将输出高电平（high )的 PWM调光信号（占空比大）， 调高背光亮度； 反之， 如果直流 DC电压信号小于升压 IC的锯齿波信号， 则比较器 C将输出低电 平 （low ) 的 PWM调光信号 (占空比小）， 调低背光亮度。
本发明实施例三提供一种液晶显示器， 包括实施例一提供的背光调光电 路。 为叙述简洁， 该背光调光电路的相关工作原理此处不再贅述。
本发明各实施例分别提供的背光调光电路及其调光方法、液晶显示器结 构简单， 不影响原有电路架构和方案， 成本投入较低； 背光亮度与画面实时 关联， 减少了其它现有方案的数据换算和数据传输， 实现实时侦测， 背光实 时响应， 降低背光功耗， 促进产品节能化。
以上所揭露的仅为本发明较佳实施例而已， 当然不能以此来限定本发明 之权利范围， 因此依本发明权利要求所作的等同变化， 仍属本发明所涵盖的 范围。

Claims

权 利 要 求
1、 一种背光调光电路， 其中， 包括：
电源电压端 VCC, 用于提供供电电压；
运算放大器 Q, 其同相输入端与所述电源电压端 VCC相连， 反相输入 端与负载端相连；
精密电阻 R,连接在所述运算放大器 Q的同相输入端和反相输入端之间， 所述精密电阻 R两端的压差信号由所述运算放大器 Q转换放大为直流 DC 电压信号并输出； 以及
比较器 C,其同相输入端接收所述运算放大器 Q输出的直流 DC电压信 号， 反相输入端接收来自升压转换器内的升压 IC的锯齿波信号， 用于将所 述直流 DC电压信号与所述升压 IC的锯齿波信号进行比较， 并根据比较结 果输出脉宽调制 PWM调光信号。
2、 根据权利要求 1所述的背光调光电路， 其中， 所述直流 DC电压为 所述比较器 C的同相输入端输入电压 VIN+,所述升压 IC的锯齿波为比较器 C的反相输入端输入电压 VIN -。
3、 根据权利要求 2所述的背光调光电路， 其中， 当 VIN+大于 VIN-时， 所述比较器 C输出占空比大的 PWM调光信号，用于调高背光亮度；当 VIN+ 小于 VIN-时， 所述比较器 C输出占空比小的 PWM调光信号， 用于调低背 光亮度。
4、 根据权利要求 1所述的背光调光电路， 其中， 所述精密电阻 R的阻 值小于等于 0.1欧姆。
5、 一种背光调光电路的调光方法， 所述背光调光电路包括： 电源电压 端 VCC; 运算放大器 Q, 其同相输入端与所述电源电压端 VCC相连， 反相 输入端与负载端相连； 精密电阻 R, 连接在所述运算放大器 Q的同相输入端 和反相输入端之间； 以及比较器 C, 其同相输入端与所述运算放大器 Q的输 出端相连， 反相输入端与升压 IC相连； 所述调光方法包括以下步骤：
将所述精密电阻 R两端的压差信号由所述运算放大器 Q转换放大为直 流 DC电压信号并输出至所述比较器 C;
由所述比较器 C将所述直流 DC电压信号与所述升压 IC的锯齿波信号 进行比较， 并根据比较结果输出脉宽调制 PWM调光信号； 以及 根据比较器输出的 PWM调光信号相应调节背光亮度。
6、 根据权利要求 5所述的背光调光方法， 其中， 当所述直流 DC电压 信号大于所述升压 IC的锯齿波信号时， 比较器 C输出占空比大的 PWM调 光信号， 进而调高背光亮度； 当所述直流 DC电压信号小于所述升压 IC的 锯齿波信号时， 比较器 C输出占空比小的 PWM调光信号， 进而调低背光亮 度。
7、 一种液晶显示器， 其中， 包括背光调光电路， 所述背光调光电路进 一步包括：
电源电压端 VCC, 用于提供供电电压；
运算放大器 Q, 其同相输入端与所述电源电压端 VCC相连， 反相输入 端与负载端相连；
精密电阻 R,连接在所述运算放大器 Q的同相输入端和反相输入端之间， 所述精密电阻 R两端的压差信号由所述运算放大器 Q转换放大为直流 DC 电压信号并输出； 以及
比较器 C,其同相输入端接收所述运算放大器 Q输出的直流 DC电压信 号， 反相输入端接收来自升压转换器内的升压 IC的锯齿波信号， 用于将所 述直流 DC电压信号与所述升压 IC的锯齿波信号进行比较， 并根据比较结 果输出脉宽调制 PWM调光信号。
8、 根据权利要求 7所述的液晶显示器， 其中， 所述直流 DC电压为所 述比较器 C的同相输入端输入电压 VIN+,所述升压 IC的锯齿波为比较器 C 的反相输入端输入电压 VIN -。
9、 根据权利要求 8所述的液晶显示器， 其中， 当 VIN+大于 VIN-时， 所述比较器 C输出占空比大的 PWM调光信号，用于调高背光亮度；当 VIN+ 小于 VIN-时， 所述比较器 C输出占空比小的 PWM调光信号， 用于调低背 光亮度。
10、 根据权利要求 7所述的液晶显示器， 其中， 所述精密电阻 R的阻值 小于等于 0.1欧姆。
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