WO2017096665A1 - 背光驱动电路、液晶显示器和背光调节方法 - Google Patents

背光驱动电路、液晶显示器和背光调节方法 Download PDF

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Publication number
WO2017096665A1
WO2017096665A1 PCT/CN2015/099780 CN2015099780W WO2017096665A1 WO 2017096665 A1 WO2017096665 A1 WO 2017096665A1 CN 2015099780 W CN2015099780 W CN 2015099780W WO 2017096665 A1 WO2017096665 A1 WO 2017096665A1
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Prior art keywords
backlight
circuit
pfm
signal
driving circuit
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English (en)
French (fr)
Inventor
邢振周
左清成
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Wuhan China Star Optoelectronics Technology Co Ltd
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Wuhan China Star Optoelectronics Technology Co Ltd
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Priority to US14/905,820 priority Critical patent/US10115352B2/en
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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
    • G09G3/3406—Control of 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
    • 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
    • G09G3/3607—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 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels
    • 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
    • G09G2310/0264—Details of driving circuits
    • G09G2310/027—Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
    • 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
    • G09G2320/0613—The adjustment depending on the type of the information to be displayed
    • 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
    • G09G2320/0613—The adjustment depending on the type of the information to be displayed
    • G09G2320/062—Adjustment of illumination source parameters
    • 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
    • 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
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/0646—Modulation of illumination source brightness and image signal correlated to each other
    • 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
    • G09G2330/021—Power management, e.g. power saving
    • 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
    • G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data

Definitions

  • the invention relates to a liquid crystal display technology, in particular to a backlight driving circuit, a liquid crystal display and a backlight adjusting method.
  • PWM pulse width modulation
  • PFM pulse frequency modulation
  • the grayscale value in the liquid crystal display has 256 grayscale values
  • the grayscale value is the concept of brightness, depending on the color depth range from 0 to 255, 0 is black, and 255 is white.
  • the grayscale value of an electronic product changes more, the load on the liquid crystal display increases. Conversely, the load on the liquid crystal display is smaller.
  • the switching operation of the switching switch is controlled by a pulse width modulation technology (PMW), and the pulse width modulation technology (PMW) has good efficiency and better control performance.
  • the working loss has conduction loss and switching loss.
  • PFM pulse frequency modulation technique
  • PWM pulse width modulation
  • PFM pulse frequency modulation
  • PWM pulse width modulation technique
  • PFM pulse frequency modulation technique
  • Another object of the present invention is to provide a liquid crystal display using the above backlight driving circuit.
  • Another object of the present invention is to provide a backlight adjustment method.
  • the backlight driving circuit of the present invention includes a backlight, an image collecting circuit, a comparison circuit, a PWM generating circuit, a PFM generating circuit, a driving circuit and a backlight driving circuit, and the image collecting circuit is configured to grayscale the current picture. The value is output to the driving circuit;
  • the driving circuit is configured to calculate a grayscale change value of the target picture grayscale value and the current picture grayscale value and transmit the grayscale change value to the comparison circuit;
  • the comparison circuit is configured to compare the grayscale change value calculated by the driving circuit with a preset grayscale change threshold, and output a PWM generating circuit control signal or a PFM generating circuit control signal according to the comparison result;
  • the PWM generating circuit is configured to generate a PWM signal and output the signal to the backlight driving circuit in response to the PWM generating circuit control signal;
  • the PFM generating circuit is configured to generate a PFM signal in response to the PFM generating circuit control signal and output the signal to the backlight driving circuit;
  • the backlight driving circuit is configured to change the backlight current to perform dimming in response to the input PWM signal or the PFM signal.
  • the grayscale change threshold preset in the comparison circuit is 26.
  • the PFM generating circuit generates a PFM signal, including adjusting a time interval of the PFM signal in real time according to a backlight current currently outputted to the backlight by the backlight driving circuit, until the backlight current currently outputted by the backlight driving circuit to the backlight reaches the Backlight current target value.
  • the PWM generating circuit generates a PWM signal, including adjusting a duty ratio of the PWM signal according to a backlight current currently outputted to the backlight by the backlight driving circuit, until the backlight current of the backlight driving circuit currently outputs to the backlight reaches the backlight current.
  • the backlight current target value is a value that specifies a duty ratio of the PWM signal according to a backlight current currently outputted to the backlight by the backlight driving circuit.
  • the PWM generating circuit and the PFM generating circuit can be implemented by a square wave generator.
  • the present invention provides a liquid crystal display including a backlight driving circuit including a backlight, an image collecting circuit, a comparison circuit, a PWM generating circuit, a PFM generating circuit, a driving circuit, and a backlight driving circuit, and the image capturing
  • the circuit is configured to output a grayscale value of the current picture to the driving circuit
  • the driving circuit is configured to calculate a grayscale change value of the target picture grayscale value and the current picture grayscale value and transmit the grayscale change value to the comparison circuit;
  • the comparison circuit is configured to compare the grayscale change value calculated by the driving circuit with a preset grayscale change threshold, and output a PWM generating circuit control signal or a PFM generating circuit control signal according to the comparison result;
  • the PWM generating circuit is configured to generate a PWM signal and output the signal to the backlight driving circuit in response to the PWM generating circuit control signal;
  • the PFM generating circuit is configured to generate a PFM signal in response to the PFM generating circuit control signal and output the signal to the backlight driving circuit;
  • the backlight driving circuit is configured to change the backlight current to perform dimming in response to the input PWM signal or the PFM signal.
  • the grayscale change threshold preset in the comparison circuit is 26.
  • the PFM generating circuit generates a PFM signal, including adjusting a time interval of the PFM signal in real time according to a backlight current currently outputted to the backlight by the liquid crystal display, until the backlight current currently output to the backlight of the liquid crystal display reaches the backlight current. Target value.
  • the PWM generating circuit generates a PWM signal, including adjusting a duty ratio of the PWM signal in real time according to a backlight current currently outputted to the backlight by the liquid crystal display, until the backlight current currently output to the backlight of the liquid crystal display reaches the backlight Current target value.
  • the PWM generating circuit and the PFM generating circuit can be implemented by a square wave generator.
  • the invention provides a backlight adjustment method, which comprises the following steps:
  • the image acquisition circuit transmits the current screen grayscale value to the driving circuit
  • the driving circuit calculates a grayscale change value of the grayscale value of the target screen and the grayscale value of the current display screen, and transmits the grayscale change value to the comparison circuit;
  • the comparison circuit compares the grayscale change value with a preset grayscale change threshold.
  • the PWM generation circuit When the grayscale change value obtained by the comparison circuit is greater than a preset grayscale change threshold, the PWM generation circuit generates a PWM signal. And outputting to the backlight driving circuit; when the grayscale change value obtained by the comparison circuit is less than or equal to a preset grayscale change threshold, the PFM generating circuit generates a PFM signal and outputs the signal to the backlight driving circuit;
  • the backlight driving circuit performs dimming by an input PWM signal or a PFM signal.
  • the grayscale change threshold in the comparison circuit is 26.
  • the PFM generating circuit generates a PFM signal, including adjusting a time interval of the PFM signal in real time according to a backlight current currently outputted to the backlight by the backlight driving circuit, until the backlight current currently outputted by the backlight driving circuit to the backlight reaches the Backlight current target value.
  • the PWM generating circuit generates a PWM signal, including adjusting a duty ratio of the PWM signal according to a backlight current currently outputted to the backlight by the backlight driving circuit, until the backlight current of the backlight driving circuit currently outputs to the backlight reaches the backlight current.
  • the backlight current target value is a value that specifies a duty ratio of the PWM signal according to a backlight current currently outputted to the backlight by the backlight driving circuit.
  • the image transmission circuit of the invention transmits the gray scale value of the screen to the driving circuit, and the driving circuit calculates the difference between the current screen grayscale value and the target grayscale value and feeds back to the comparison circuit, and compares the grayscale variation value obtained by the comparison circuit.
  • the PWM generating circuit When the preset gray scale change threshold is greater than the preset gray scale change threshold, the PWM generating circuit generates a PWM signal and outputs the signal to the backlight driving circuit. Otherwise, the PFM generating circuit generates the PFM signal and outputs the signal to the backlight driving circuit, thereby reducing the overall energy loss of the backlight adjusting process and improving The efficiency of the circuit.
  • FIG. 1 is a schematic structural view of a backlight driving circuit of the present invention.
  • the backlight driving circuit of the present invention includes a main control circuit 100 , a driving circuit 200 , a backlight driving circuit 300 , and a backlight 400 .
  • the main control circuit 100 includes: an image collecting circuit 101 , a comparing circuit 102 , a PWM generating circuit 103 , and The PFM generation circuit 104.
  • the image acquisition circuit 101 is configured to extract feature parameters of the image data, that is, collect grayscale values of the current image, the grayscale value is a concept of luminance, and the grayscale value ranges from 0 to 255, indicating that the brightness is from deep to shallow, corresponding to the image.
  • the color is from black to white, and each pixel value is one of 256 gray scales between black and white.
  • the image acquisition circuit 101 in the main control circuit 100 transmits the acquired grayscale value of the current picture to the drive circuit 200.
  • the driving circuit 200 receives the grayscale value of the current picture, and calculates a grayscale change value of the target screen grayscale value and the current screen grayscale value.
  • the drive circuit 200 calculates the gray scale change value and transmits it to the comparison circuit 102 in the main control circuit 100.
  • the comparison circuit 100 compares the grayscale value change value with a preset grayscale threshold value. At this time, if the grayscale value change value is higher than the preset grayscale threshold, the comparison circuit 100 generates a PWM generation circuit control signal to control the PWM generation circuit. 103.
  • the PWM generating circuit 103 generates a PWM signal after receiving the control signal, and outputs the PWM signal to the backlight driving circuit 300 to adjust the brightness of the backlight module.
  • the comparison circuit The 100 generating PFM generating circuit control signal controls the PFM generating circuit 104, and the PFM generating circuit 104 generates a PFM signal and outputs it to the backlight driving circuit 300, and the backlight driving circuit 300 performs dimming according to the PFM signal.
  • the backlight driving circuit 300 performs dimming by changing the current input to the backlight to achieve a grayscale value of the target image.
  • the invention transmits the gray scale value of the screen to the driving circuit through the image collecting circuit in the main control circuit, and the driving circuit calculates the difference between the gray level value of the current picture and the target gray level value and feeds back to the comparison circuit in the main control circuit, when When the grayscale change value is greater than the preset grayscale change threshold, the PWM generating circuit of the main control circuit generates a PWM signal and outputs the PWM signal to the backlight driving circuit. Otherwise, the PFM generating circuit of the main control circuit generates the PFM signal and outputs the backlight to the backlight.
  • the driving circuit reduces the overall energy loss of the backlight adjustment process and improves the working efficiency of the circuit.
  • the grayscale change threshold may be about 10% of a range of grayscale values, and the grayscale value of the image is between 0-255. That is, the grayscale change threshold can be set to 26. Specifically, if the grayscale value of the current picture is 200, and the grayscale value of the target picture is 255 (or the grayscale value of the current picture is 255, and the grayscale value of the target picture is 200), that is, the grayscale change value is 55>26, the gray scale change value is small, the load at this time is large, so the PMW adjustment is needed, and the comparison circuit 102 outputs the PWM output.
  • the circuit control circuit 103 generates a PWM signal in response to the PWM generation circuit control signal and outputs it to the backlight driving circuit 300.
  • the grayscale value of the current picture is 200
  • the grayscale value of the target picture is 215 (or the grayscale value of the current picture is 215, and the grayscale value of the target picture is 200), that is, the grayscale change value. 15 ⁇ 26
  • the backlight needs to adjust the gray-scale difference is small, the load is relatively small, need to adopt PFM adjustment
  • the comparison circuit 102 outputs the PFM generating circuit control signal
  • the PFM generating circuit 104 generates the circuit control signal in response to the PFM, generating The PFM signal is output to the backlight driving circuit 300.
  • the PFM generating circuit 104 may further adjust the time interval of the PFM signal in real time according to the backlight current currently output to the backlight by the backlight driving circuit 300 until the current output of the backlight driving circuit 300 is The backlight current of the backlight reaches the target value of the backlight current.
  • the PFM generating circuit 104 can adjust the time interval of the PFM signal in real time until the grayscale value of the current picture is equal to the grayscale value of the target picture.
  • the PWM generating circuit 103 may further adjust the duty ratio of the PWM signal in real time according to the backlight current currently output to the backlight by the backlight driving circuit 300 until the current output of the backlight driving circuit 300.
  • the backlight current to the backlight reaches the backlight current target value.
  • the PWM generating circuit 103 can adjust the duty ratio of the PWM signal in real time until the grayscale value of the current picture is equal to the grayscale value of the target picture.
  • the above-mentioned PWM generating circuit and the PFM generating circuit can be implemented by a square wave generator, and the specific process is a prior art, and details are not described herein again.
  • the backlight driving circuit 300 may specifically include: an input filter, a power switch, an inductor or a transformer, an output rectification or filter, a dimming controller, and a main control circuit, wherein the input terminal Vin is connected to the power source, and the output terminal Vout is output.
  • the backlight current and the backlight voltage are given to the LED backlight, and the output terminal Vout is connected to the dimming controller, and the output backlight current is fed back to the dimming controller.
  • the backlight may be an LED strip.
  • the present invention also provides a liquid crystal display comprising any of the above backlight driving circuits, which can be applied to mobile phones, tablet computers, televisions, displays, notebook computers, digital photo frames, navigators, etc. Any electronic device with display capabilities.
  • the invention also provides a backlight adjustment method, which mainly comprises the following steps:
  • the image collecting circuit in the main control circuit first transmits the collected gray level value of the current picture to the driving circuit;
  • the driving circuit calculates a grayscale change value of the grayscale value of the target picture and the grayscale value of the current display picture, and feeds back the grayscale change value to the comparison circuit of the main control circuit for comparison;
  • the comparison circuit receives the gray scale change value calculated by the driving circuit, and compares the gray scale change value with a preset gray scale change threshold. Specifically, when the grayscale change value obtained by the comparison circuit is greater than a preset grayscale change threshold, the PWM generation circuit of the main control circuit generates a PWM signal and outputs the PWM signal to the backlight driving circuit; when the comparison circuit obtains the grayscale change value When the preset gray scale change threshold is less than or equal to, the PFM generating circuit 104 of the main control circuit generates a PFM signal and outputs the signal to the backlight driving circuit;
  • the backlight driving circuit performs dimming by an input PWM signal or a PFM signal. Further specifically, the backlight driving circuit dims by changing the current of the input backlight to achieve the grayscale value of the target picture.
  • the grayscale change threshold may be about 10% of a range of grayscale values, and the grayscale value of the image is between 0-255. That is, the grayscale change threshold can be set to 26.
  • the PFM generating circuit may further adjust the time interval of the PFM signal in real time according to the backlight current currently output to the backlight by the backlight driving circuit until the current output of the backlight driving circuit The backlight current to the backlight reaches the backlight current target value.
  • the PFM generating circuit can adjust the time interval of the PFM signal in real time until the grayscale value of the current picture is equal to the grayscale value of the target picture.
  • the PWM generating circuit may further adjust the duty ratio of the PWM signal in real time according to the backlight current currently outputted to the backlight by the backlight driving circuit until the backlight driving circuit is currently The backlight current output to the backlight reaches the target value of the backlight current.
  • the PWM generating circuit can adjust the duty ratio of the PWM signal in real time until the grayscale value of the current picture is equal to the grayscale value of the target picture.

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

Abstract

一种背光驱动电路，包括背光源（400）、图像采集电路（101）、比较电路（102）、PWM产生电路（103）、PFM产生电路（104）、驱动电路（200）和背光驱动电路（300），图像采集电路（101）用于将当前画面的灰阶值输出给驱动电路（200）；驱动电路（200）用于计算灰阶变化值并传送至比较电路（102）；比较电路（102）用于将灰阶变化值与预设的灰阶变化阈值进行比较，输出PWM产生电路控制信号或PFM产生电路控制信号； PWM产生电路（103）用于产生PWM信号并输出给背光驱动电路（300）； PFM产生电路（104）用于产生PFM信号并输出给背光驱动电路（300）；背光驱动电路（300）用于改变背光源电流进行调光。背光驱动电路降低背光调节过程的整体能量损耗，提高电路的工作效率。

Description

背光驱动电路、液晶显示器和背光调节方法
本发明要求2015年12月9日递交的发明名称为“背光驱动电路、液晶显示器和背光调节方法”的申请号201510903551.3的在先申请优先权，上述在先申请的内容以引入的方式并入本文本中。
技术领域
本发明涉及一种液晶显示技术，尤其涉及一种背光驱动电路、液晶显示器和背光调节方法。
背景技术
由于电子技术的蓬勃发展，电子产品已被人们广为使用，因此，电子产品使用的电力供应问题成为非常重要的课题。目前，电子产品普遍使用开关切换式的电源供应方式来实现电力的供应，并且，开关切换式是可以通过脉宽调变技术(PWM)或脉冲频率调变技术(PFM)两种工作模式来进行开关的切换工作。
因为在液晶显示器中的灰阶图像有256个灰阶值，灰阶值是亮度的概念，依据颜色深浅范围为0～255，0为黑色，255为白色。当电子产品的灰阶值变化越大，液晶显示器的负载也就越大。反之，液晶显示器的负载也就越小。通常在大负载条件下进行工作时，通过脉宽调变技术(PMW)来控制切换开关的切换动作，此时采用脉宽调变技术(PMW)具有良好的效率和较佳的控制性能，其工作损耗有传导损耗与开关切换损耗。当电子产品处于轻载时，若仍由脉宽调变技术(PWM)来控制切换开关的切换动作，此时传导损耗会因为电子产品处于轻载而下降，不过由于开关切换频率固定不变，所以开关切换损耗不会随着负载下降而减少，从而在轻载时，使用脉宽调变技术(PWM)的工作模式，则其整体损耗大、效率降低，不利于节能设计。
通常，当电子产品在轻载条件下进行工作时，一般采用脉冲频率调变技术(PFM)来控制切换开关的切换动作。即在负载下降时，开关的切换频率也随之下降，从而可以降低开关切换损耗，维持较高的工作效率。
因此，电子产品可以根据负载情况自动选择脉宽调变技术(PWM)或脉冲频率调变技术(PFM)开关切换模式是电子发展的趋势。
发明内容
本发明的目的在于提供一种可以根据灰阶变化值自动选择脉宽调变技术(PWM)或脉冲频率调变技术(PFM)开关切换模式的背光驱动电路。
本发明的另一目的在于提供一种采用上述背光驱动电路的液晶显示器。
本发明的另一目的在于提供一种背光调节方法。
为了实现上述目的，本发明实施方式提供如下技术方案：
本发明所述的背光驱动电路，其中，包括背光源、图像采集电路、比较电路、PWM产生电路、PFM产生电路、驱动电路和背光驱动电路，所述图像采集电路用于将当前画面的灰阶值输出给所述驱动电路；
所述驱动电路用于计算目标画面灰阶值与当前画面灰阶值的灰阶变化值并将该灰阶变化值传送至所述比较电路；
所述比较电路用于将所述驱动电路计算出的灰阶变化值与预设的灰阶变化阈值进行比较，并依据比较结果输出PWM产生电路控制信号或PFM产生电路控制信号；
所述PWM产生电路用于响应所述PWM产生电路控制信号，产生PWM信号并输出给所述背光驱动电路；
所述PFM产生电路用于响应所述PFM产生电路控制信号，产生PFM信号并输出给所述背光驱动电路；
所述背光驱动电路用于响应输入的所述PWM信号或所述PFM信号改变所述背光源电流进行调光。
其中，所述比较电路中预设的灰阶变化阈值为26。
其中，所述PFM产生电路产生PFM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
其中，所述PWM产生电路产生PWM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
其中，所述PWM产生电路和所述PFM产生电路均可以通过一个方波发生器来实现。
本发明提供一种液晶显示器，其中，包括背光驱动电路，所述背光驱动电路包括背光源、图像采集电路、比较电路、PWM产生电路、PFM产生电路、驱动电路和背光驱动电路，所述图像采集电路用于将当前画面的灰阶值输出给所述驱动电路；
所述驱动电路用于计算目标画面灰阶值与当前画面灰阶值的灰阶变化值并将该灰阶变化值传送至所述比较电路；
所述比较电路用于将所述驱动电路计算出的灰阶变化值与预设的灰阶变化阈值进行比较，并依据比较结果输出PWM产生电路控制信号或PFM产生电路控制信号；
所述PWM产生电路用于响应所述PWM产生电路控制信号，产生PWM信号并输出给所述背光驱动电路；
所述PFM产生电路用于响应所述PFM产生电路控制信号，产生PFM信号并输出给所述背光驱动电路；
所述背光驱动电路用于响应输入的所述PWM信号或所述PFM信号改变所述背光源电流进行调光。
其中，所述比较电路中预设的灰阶变化阈值为26。
其中，所述PFM产生电路产生PFM信号，包括根据液晶显示器当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到液晶显示器当前输出给背光源的背光电流达到所述背光电流目标值。
其中，所述PWM产生电路产生PWM信号，包括根据液晶显示器当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到液晶显示器当前输出给背光源的背光电流达到所述背光电流目标值。
其中，所述PWM产生电路和所述PFM产生电路均可以通过一个方波发生器来实现。
本发明提供一种背光调节方法，其中，包括如下步骤：
图像采集电路将当前画面灰阶值传输给驱动电路；
驱动电路计算目标画面灰阶值与当前显示画面的灰阶值的灰阶变化值，并将所述灰阶变化值传送到比较电路；
比较电路将所述灰阶变化值与预设的灰阶变化阈值进行比较，当比较电路得到的灰阶变化值大于预设的灰阶变化阈值时，PWM产生电路产生PWM信 号并输出给背光驱动电路；比较电路得到的灰阶变化值小于或等于预设的灰阶变化阈值时，PFM产生电路产生PFM信号并输出给背光驱动电路；
背光驱动电路通过输入的PWM信号或PFM信号进行调光。
其中，所述比较电路中灰阶变化阈值为26。
其中，所述PFM产生电路产生PFM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
其中，所述PWM产生电路产生PWM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
本发明实施例具有如下优点或有益效果：
本发明通过中的图像采集电路将画面灰阶值传输给驱动电路，驱动电路将计算当前画面灰阶值与目标灰阶值的差值并反馈到比较电路，当比较电路得到的灰阶变化值大于预设的灰阶变化阈值时，PWM产生电路产生PWM信号并输出给背光驱动电路，反之，则PFM产生电路产生PFM信号并输出给背光驱动电路，从而降低背光调节过程的整体能量损耗，提高电路的工作效率。
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是本发明背光驱动电路结构示意图。
具体实施方式
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，所描述的实施例仅仅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做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。
请参阅图1，本发明的背光驱动电路包括主控电路100、驱动电路200、背光驱动电路300和背光源400，主控电路100包括：图像采集电路101、比较电路102、PWM产生电路103和PFM产生电路104。图像采集电路101用于提取图像数据的特征参数，即采集当前画面的灰阶值，灰阶值是亮度的概念，灰阶值的范围为0～255，表示亮度从深到浅，对应图像中的颜色为从黑到白，每个像素值都是介于黑色和白色之间的256种灰阶中的一种。主控电路100中的图像采集电路101将采集到的当前画面的灰阶值传输给所述驱动电路200。驱动电路200接收所述当前画面的灰阶值，并计算出目标画面灰阶值与当前画面灰阶值的灰阶变化值。驱动电路200计算出灰阶变化值后将其传输至主控电路100中的比较电路102。比较电路100将灰阶值变化值与预设的灰阶阈值进行比较，此时若灰阶值变化值高于预设的灰阶阈值时，比较电路100产生PWM产生电路控制信号控制PWM产生电路103，PWM产生电路103接收控制信号后产生PWM信号并输出给所述背光驱动电路300，以调节背光模组亮度；此时若灰阶值变化值低于预设的灰阶阈值时，比较电路100产生PFM产生电路控制信号控制PFM产生电路104，PFM产生电路104产生PFM信号并输出给背光驱动电路300，背光驱动电路300根据PFM信号进行调光。具体的，背光驱动电路300通过改变输入背光源的电流进行调光，以达到目标画面的灰阶值。
本发明通过主控电路中的图像采集电路将画面灰阶值传输给驱动电路，驱动电路将计算当前画面灰阶值与目标灰阶值的差值并反馈到主控电路中的比较电路，当灰阶变化值大于预设的灰阶变化阈值时，所述主控电路的PWM产生电路产生PWM信号并输出给背光驱动电路，反之，则主控电路的PFM产生电路产生PFM信号并输出给背光驱动电路，从而降低背光调节过程的整体能量损耗，提高电路的工作效率。
进一步的，所述灰阶变化阈值可以是灰阶值的范围的10％左右，图像的灰阶值介于0-255之间。也就是说，灰阶变化阈值可以设置为26。具体的，若当前画面的灰阶值为200，而目标画面的灰阶值为255时(或者当前画面的灰阶值为255，目标画面灰阶值为200时)，即灰阶变化值为55>26，灰阶变化值较小，此时的负载较大，所以需要采用PMW调节，比较电路102输出PWM产 生电路控制信号，PWM产生电路103响应所述PWM产生电路控制信号，产生PWM信号并输出给所述背光驱动电路300。亦或者此时当前画面的灰阶值为200，而目标画面的灰阶值为215时(或者当前画面的灰阶值为215，目标画面的灰阶值为200时)，即灰阶变化值为15<26，背光需要调节的灰阶差值较小，负载也比较小，需要采用PFM调节，比较电路102输出PFM产生电路控制信号，PFM产生电路104响应所述PFM产生电路控制信号，产生PFM信号并输出给所述背光驱动电路300。
具体的，所述PFM产生电路104在产生PFM信号过程中，还可以根据背光驱动电路300当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到背光驱动电路300当前输出给背光源的背光电流达到所述背光电流目标值。换而言之，PFM产生电路104可以实时调整所述PFM信号的时间间隔，直到当前画面的灰阶值等于目标画面的灰阶值。
具体的，所述PWM产生电路103在产生PWM信号过程中，还可以根据背光驱动电路300当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到背光驱动电路300当前输出给背光源的背光电流达到所述背光电流目标值。换而言之，PWM产生电路103可以实时调整所述PWM信号的占空比，直到当前画面的灰阶值等于目标画面的灰阶值。
进一步具体的，上述的PWM产生电路和PFM产生电路均可以通过一个方波发生器来实现，具体过程为现有技术，在此不再赘述。
进一步具体的，背光驱动电路300具体可以包括：输入过滤器、功率开关、电感或变压器、输出整流或滤波器、调光控制器和主控制电路，其中，输入端Vin连接电源，输出端Vout输出背光电流和背光电压给LED背光源，并且输出端Vout与调光控制器连接，还将输出的背光电流反馈给调光控制器。
进一步具体的，所述背光源可以是LED灯条(Bar)。
本发明还提供了一种液晶显示器，所述液晶显示器包括上述的任意一种背光驱动电路，所述液晶显示器可以应用于手机、平板电脑、电视机、显示器、笔记本电脑、数码相框、导航仪等任何具有显示功能的电子设备上。
本发明还提供一种背光调节方法，主要包括入下步骤：
提供一驱动电路和一具有图像采集电路、比较电路、PWM产生电路和 PFM产生电路的主控电路，主控电路中的图像采集电路先将采集到的当前画面灰阶值传输给驱动电路；
然后，所述驱动电路计算目标画面灰阶值与当前显示画面的灰阶值的灰阶变化值，并将所述灰阶变化值反馈到主控电路的比较电路中进行比较；
比较电路接收所述驱动电路计算得出的灰阶变化值，再将所述灰阶变化值与预设的灰阶变化阈值进行比较。具体的，当比较电路得到的灰阶变化值大于预设的灰阶变化阈值时，所述主控电路的PWM产生电路产生PWM信号并输出给背光驱动电路；当比较电路得到的灰阶变化值小于或等于预设的灰阶变化阈值时，所述主控电路的PFM产生电路104产生PFM信号并输出给背光驱动电路；
背光驱动电路通过输入的PWM信号或PFM信号进行调光。进一步的具体的，背光驱动电路通过改变输入背光源的电流进行调光，以达到目标画面的灰阶值。
进一步的，所述灰阶变化阈值可以是灰阶值的范围的10％左右，图像的灰阶值介于0-255之间。也就是说，灰阶变化阈值可以设置为26。
具体的，背光调节过程中，所述PFM产生电路在产生PFM信号时，还可以根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。换而言之，PFM产生电路可以实时调整所述PFM信号的时间间隔，直到当前画面的灰阶值等于目标画面的灰阶值。
具体的，背光调节过程中，所述PWM产生电路在产生PWM信号时，还可以根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。换而言之，PWM产生电路可以实时调整所述PWM信号的占空比，直到当前画面的灰阶值等于目标画面的灰阶值。
以上所述的实施方式，并不构成对该技术方案保护范围的限定。任何在上述实施方式的精神和原则之内所作的修改、等同替换和改进等，均应包含在该技术方案的保护范围之内。

Claims (14)

  1. 一种背光驱动电路，其中，包括背光源、图像采集电路、比较电路、PWM产生电路、PFM产生电路、驱动电路和背光驱动电路，所述图像采集电路用于将当前画面的灰阶值输出给所述驱动电路；
    所述驱动电路用于计算目标画面灰阶值与当前画面灰阶值的灰阶变化值并将该灰阶变化值传送至所述比较电路；
    所述比较电路用于将所述驱动电路计算出的灰阶变化值与预设的灰阶变化阈值进行比较，并依据比较结果输出PWM产生电路控制信号或PFM产生电路控制信号；
    所述PWM产生电路用于响应所述PWM产生电路控制信号，产生PWM信号并输出给所述背光驱动电路；
    所述PFM产生电路用于响应所述PFM产生电路控制信号，产生PFM信号并输出给所述背光驱动电路；
    所述背光驱动电路用于响应输入的所述PWM信号或所述PFM信号改变所述背光源电流进行调光。
  2. 如权利要求1所述的背光驱动电路，其中，所述比较电路中预设的灰阶变化阈值为26。
  3. 如权利要求1所述的背光驱动电路，其中，所述PFM产生电路产生PFM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
  4. 如权利要求1所述的背光驱动电路，其中，所述PWM产生电路产生PWM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
  5. 如权利要求1所述的背光驱动电路，其中，所述PWM产生电路和所述PFM产生电路均可以通过一个方波发生器来实现。
  6. 一种液晶显示器，其中，包括背光驱动电路，所述背光驱动电路包括背光源、图像采集电路、比较电路、PWM产生电路、PFM产生电路、驱动电路和背光驱动电路，所述图像采集电路用于将当前画面的灰阶值输出给所述驱动电路；
    所述驱动电路用于计算目标画面灰阶值与当前画面灰阶值的灰阶变化值并将该灰阶变化值传送至所述比较电路；
    所述比较电路用于将所述驱动电路计算出的灰阶变化值与预设的灰阶变化阈值进行比较，并依据比较结果输出PWM产生电路控制信号或PFM产生电路控制信号；
    所述PWM产生电路用于响应所述PWM产生电路控制信号，产生PWM信号并输出给所述背光驱动电路；
    所述PFM产生电路用于响应所述PFM产生电路控制信号，产生PFM信号并输出给所述背光驱动电路；
    所述背光驱动电路用于响应输入的所述PWM信号或所述PFM信号改变所述背光源电流进行调光。
  7. 如权利要求6所述的液晶显示器，其中，所述比较电路中预设的灰阶变化阈值为26。
  8. 如权利要求6所述的液晶显示器，其中，所述PFM产生电路产生PFM信号，包括根据液晶显示器当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到液晶显示器当前输出给背光源的背光电流达到所述背光电流目标值。
  9. 如权利要求6所述的液晶显示器，其中，所述PWM产生电路产生PWM信号，包括根据液晶显示器当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到液晶显示器当前输出给背光源的背光电流达到所述背光电 流目标值。
  10. 如权利要求6所述的液晶显示器，其中，所述PWM产生电路和所述PFM产生电路均可以通过一个方波发生器来实现。
  11. 一种背光调节方法，其中，包括如下步骤：
    图像采集电路将当前画面灰阶值传输给驱动电路；
    驱动电路计算目标画面灰阶值与当前显示画面的灰阶值的灰阶变化值，并将所述灰阶变化值传送到比较电路；
    比较电路将所述灰阶变化值与预设的灰阶变化阈值进行比较，当比较电路得到的灰阶变化值大于预设的灰阶变化阈值时，PWM产生电路产生PWM信号并输出给背光驱动电路；比较电路得到的灰阶变化值小于或等于预设的灰阶变化阈值时，PFM产生电路产生PFM信号并输出给背光驱动电路；
    背光驱动电路通过输入的PWM信号或PFM信号进行调光。
  12. 如权利要求11所述的背光调节方法，其中，所述比较电路中灰阶变化阈值为26。
  13. 如权利要求11所述的背光调节方法，其中，所述PFM产生电路产生PFM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PFM信号的时间间隔，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
  14. 如权利要求11所述的背光调节方法，其中，所述PWM产生电路产生PWM信号，包括根据背光驱动电路当前输出给背光源的背光电流，实时调整所述PWM信号的占空比，直到背光驱动电路当前输出给背光源的背光电流达到所述背光电流目标值。
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