WO2013023395A1 - 一种led背光驱动方法、液晶显示装置及led背光驱动电路 - Google Patents

一种led背光驱动方法、液晶显示装置及led背光驱动电路 Download PDF

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Publication number
WO2013023395A1
WO2013023395A1 PCT/CN2011/079445 CN2011079445W WO2013023395A1 WO 2013023395 A1 WO2013023395 A1 WO 2013023395A1 CN 2011079445 W CN2011079445 W CN 2011079445W WO 2013023395 A1 WO2013023395 A1 WO 2013023395A1
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Prior art keywords
current
led
led string
voltage
backlight driving
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PCT/CN2011/079445
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English (en)
French (fr)
Inventor
高新明
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深圳市华星光电技术有限公司
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Priority to US13/320,253 priority Critical patent/US8686653B2/en
Publication of WO2013023395A1 publication Critical patent/WO2013023395A1/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
    • G09G3/3406—Control of illumination source
    • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines
    • 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
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • 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
    • G09G2330/028—Generation of voltages supplied to electrode drivers in a matrix display other than LCD

Definitions

  • the present invention relates to the field of liquid crystal display, and more particularly to an LED backlight driving method, a liquid crystal display device, and an LED backlight driving circuit.
  • a liquid crystal display device using LED as a backlight the existing LED driving device is as shown in FIG. 1:
  • the backlight driving includes a light guiding plate, and the light guiding plate is provided with a plurality of parallel LED strings, and each LED string includes a plurality of series connected LED light, one end of the LED string is connected with the forward voltage Vin, and the other end is connected to the constant current controller respectively.
  • the LED driving device monitors the voltage of each LED string in real time, and then feeds the minimum voltage to the power input terminal to adjust the positive direction.
  • the value of the voltage Vin is used to ensure that the forward voltage Vin can meet the brightness requirement of the LED string with the smallest voltage, and the input voltage of the LED is optimized.
  • the constant current control circuit uses the same current and duty cycle (Duty) drive to control the different strings of LEDs, as shown in Figure 2, thus ensuring the current RMS of all LED strings. They are equal so that the brightness of the LEDs is consistent.
  • this difference is added to the constant current control circuit, causing loss, causing the temperature of the constant current control circuit to rise and the power efficiency to be low.
  • the technical problem to be solved by the present invention is to provide an LED backlight driving method, a liquid crystal display device and an LED backlight driving circuit which can compensate for the LED voltage difference under the premise of ensuring brightness.
  • An LED backlight driving method the steps of which include:
  • A The voltage of each LED string is equal by adjusting the current of the LED string
  • the step A includes the following steps: detecting the voltage value of the LED string with the smallest voltage, and adjusting the voltage of each LED string to make the voltage of each LED string be the above voltage value. This method can achieve lower power and reduce energy consumption.
  • the current duty ratio of the LED string in the step B is less than 80%, and a wide adjustment range can be obtained in this range.
  • the step A includes the following steps: detecting the voltage value of the LED string having the largest voltage, and adjusting the voltage of each LED string to make the voltage of each LED string be the above voltage value. This method can achieve higher brightness.
  • the step A includes the following steps: detecting the average value of the voltage of each LED string, and adjusting the current of each LED string to make the voltage of each LED string be the above-mentioned voltage average value. This method provides a wider adjustment range based on the average value.
  • the step B further includes a step C: feeding back the current RMS value after the current sharing to the power module of the LED string power supply, and the power module adjusts the output voltage in real time according to the current RMS value required by the current brightness, and then repeats the steps. A ⁇ C. This method ensures that the brightness of the adjusted LED light meets the preset requirements.
  • the step B further comprises the step D: determining whether the current effective value adjustment exceeds the adjustment range of the LED string duty ratio, and if so, the LED backlight driving circuit is switched to the constant current control mode, that is, the current magnitude of all the LED strings. And the duty cycle is the same; if no, return to the step.
  • This method can automatically adopt the constant current control method commonly used in the prior art when the adjustment range of the duty ratio of the LED string is exceeded, so as to ensure that the LED backlight driving circuit can work normally.
  • An LED backlight driving circuit comprises a plurality of parallel LED strings and a power module for supplying the same, each LED string comprises a plurality of LED lamps connected in series, and the LED backlight driving circuit further comprises a current for adjusting the LED strings a current regulating module that equalizes the voltage of each LED string, and a duty ratio adjusting module that adjusts the current duty of each LED string to achieve a brightness requirement by adjusting the current duty ratio of the corresponding LED string.
  • the current adjustment module includes a voltage detection circuit that detects a voltage of each LED string.
  • the current detecting circuit further includes a control circuit for adjusting the current of each LED string based on a reference voltage obtained by the voltage detecting circuit. This is a specific embodiment of the current regulation module.
  • a liquid crystal display device characterized in that the liquid crystal display device comprises the above LED backlight driving circuit.
  • the invention reduces the voltage Vf of a single LED lamp by reducing the current If of a single LED; reduces the LED string current Vfs by reducing the LED string current of the LED string voltage Vfs, and makes the LED string and the LED string with the LED string voltage Vfs large
  • a small matching of the voltage Vfs can match the voltages of the LEDs of different LED strings, reduce the voltage difference, reduce the voltage applied to the constant current MOSFET, reduce the loss, and improve the efficiency; while the current values of the different LED strings are equal, Can ensure the consistency of LED brightness.
  • FIG. 1 is a schematic diagram of a prior art LED backlight driving method
  • FIG. 2 is a schematic diagram of a prior art LED backlight driving current waveform
  • Figure 3 is a graph showing the relationship between the voltage Vf of a single LED of the present invention and the current If flowing through the LED;
  • Figure 4 is a graph showing the relationship between the lumen of the LED of the present invention and the current If;
  • FIG. 5 is a flow chart of an LED driving method according to an embodiment of the present invention.
  • FIG. 5 is a block diagram showing the principle of an LED driving circuit according to an embodiment of the present invention.
  • Fig. 6 is a schematic view showing the waveform of the driving current of the LED backlight according to the embodiment of the present invention.
  • the inventive concept of the LED backlight driving method of the present invention is as follows:
  • the relationship between the relative luminous intensity of the LED and the lumen and current If is shown in Figure 3 and Figure 4: The larger the forward current, the greater the relative luminous intensity and the greater the lumen, the more the forward current Small, the smaller the relative luminous intensity, the smaller the lumen. Since the voltages Vfs of the different strings of LEDs are different, the difference is added to the constant current MOSFET. By reducing the current of the large LED string 1 with the voltage Vfs, the voltage Vf of the single LED is lowered, and the voltage Vfs of the different strings is close. The voltage difference ⁇ Vfs is reduced, which reduces the voltage applied to the constant current MOSFET.
  • the LED backlight driving method shown in this embodiment includes the following steps:
  • A The voltage of each LED string 1 is equal by adjusting the current of the LED string 1;
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • step A is performed: detecting the voltage value of the LED string 1 having the smallest voltage based on the minimum voltage, and adjusting the current of each LED string 1 so that the voltage of each LED string 1 is the above voltage value.
  • step B is performed: the current effective value of each LED string 1 is adjusted to a preset brightness requirement by adjusting the current duty ratio of the corresponding LED string 1.
  • the current duty ratio of the LED string 1 is preferably less than 80%, which ensures a wide adjustment range. With the minimum voltage value of LED string 1, the lower voltage value can be obtained. Power consumption.
  • the step B may further include the step C: feeding back the current effective value after the current sharing to the power supply of the LED string 1 Module, the power module adjusts the output voltage in real time according to the current RMS value required for the current brightness, and then repeats steps A ⁇ C.
  • the LED backlight driving circuit can also work normally, and the step B can further include the step D: determining whether the current effective value adjustment exceeds the LED string 1 The adjustment range of the air ratio, if yes, the LED backlight drive circuit is switched to the constant current control mode, that is, the current magnitude and duty ratio of all the LED strings 1 are consistent; if not, return to step A.
  • Embodiment 2 :
  • step A is performed first, and the step A includes the following steps: detecting the voltage value of the LED string 1 having the largest voltage, and adjusting the voltage of each LED string 1 to make the voltage of each LED string 1 the above-mentioned voltage value. Then perform step B: By adjusting the current duty ratio of the corresponding LED string 1, the current effective value of each LED string 1 reaches the preset brightness requirement. This embodiment is based on the maximum voltage value of the LED string 1.
  • the step B further includes the step C: feeding back the current effective value after the current sharing to the power supply module of the LED string 1 , and the power module is effective according to the current required by the current brightness.
  • the value adjusts the output voltage in real time, then repeat steps A ⁇ C.
  • the LED backlight driving circuit can also work normally, and the step B further includes the step D: determining whether the current effective value adjustment exceeds the LED string 1 duty.
  • the adjustment range of the ratio if yes, the LED backlight drive circuit is switched to the constant current control mode, that is, the current magnitude and duty ratio of all the LED strings 1 are consistent; if not, return to step A.
  • step A is performed first, and the step A includes the following steps: detecting and calculating the average value of the voltage of each LED string 1, and adjusting the current of each LED string 1 so that the voltage of each LED string 1 is the above-mentioned voltage average value. Then perform step B: By adjusting the current duty ratio of the corresponding LED string 1, the current effective value of each LED string 1 reaches the preset brightness requirement. In this embodiment, based on the average value of the voltage of the LED string 1, a wide adjustment range can be obtained.
  • the step B further includes the step C: feeding back the current effective value after the current sharing to the power supply module of the LED string 1 , and the power module is effective according to the current required by the current brightness.
  • the value adjusts the output voltage in real time, then repeat steps A ⁇ C.
  • the LED backlight driving circuit can also work normally, and the step B further includes the step D: determining whether the current effective value adjustment exceeds the LED string 1 duty.
  • the adjustment range of the ratio if yes, the LED backlight drive circuit is switched to the constant current control mode, that is, the current magnitude and duty ratio of all the LED strings 1 are consistent; if not, return to step A.
  • the structure of the LED backlight driving circuit of the liquid crystal display device using the above LED backlight driving method is as shown in FIG. 6.
  • the LED backlight driving circuit includes a plurality of LED strings 1 connected in parallel and a power module for supplying power thereto, and each LED string 1 includes many a series of LED lamps, characterized by further comprising a current regulating module 2 for adjusting the current of the LED string 1 to make the voltage of each LED string 1 equal, and by adjusting the current duty ratio of the corresponding LED string 1
  • the current effective value of each LED string 1 reaches the duty ratio adjustment module 3 of the brightness requirement.
  • the adjusted current waveform is shown in Figure 7.
  • the current adjustment module 2 includes a voltage detecting circuit 21 and a current detecting circuit 22 that detect voltages of the respective LED strings 1, and further includes adjusting the LED strings 1 based on a reference voltage obtained according to the voltage detecting circuit.
  • Current control circuit 23 is shown in Figure 7.

Abstract

一种LED背光驱动方法、液晶显示装置及LED背光驱动电路，该LED背光驱动方法，其步骤包括：通过调节LED串（1）的电流大小，使每条LED串（1）的电压相等；通过调节相应LED串（1）的电流占空比，使每条LED串（1）的电流有效值达到预设的亮度要求。本发明通过电流调节模块（2）调节电流大小保障每条LED串（1）的电压相等，解决了压差造成的损耗问题；同时通过占空比调节模块（3）调整占空比使得每条LED串（1）的电流有效值相等，保证了亮度的一致性。

Description

一种 LED背光驱动方法、 液 显示装置及 LED背光驱动电路 【技术领域】
本发明涉及液晶显示领域， 更具体的说， 涉及一种 LED背光驱动方法、 液 晶显示装置及 LED背光驱动电路。
【背景技术】
采用 LED作为背光源的液晶显示装置， 其现有的 LED驱动装置如图 1所 示： 该背光驱动包括导光板， 导光板上设有多条并联的 LED串， 每个 LED串包 括多个串联的 LED灯， LED串一端与正向电压 Vin连通， 另外一端分别连接到 恒流控制器， LED驱动装置会实时监测每一条 LED串的电压， 然后把最小电压 反馈到电源输入端，调整正向电压 Vin的数值， 以保证正向电压 Vin能满足电压 最小的 LED串的亮度要求， 使 LED的输入电压最优化。 同时， 为了保证 LED 亮度的一致性， 恒流控制电路采用同样的电流和占空比 （Duty )驱动来控制不 同串的 LED, 如图 2中所示， 这样保证了所有 LED串的电流有效值是相等的， 从而可以保证 LED亮度的一致性。 该实施方式由于不同串的 LED的电压不同， 这个差值会加在恒流控制电路上， 造成损耗， 使恒流控制电路温度升高， 电源 效率变低。
【发明内容】
本发明所要解决的技术问题是提供一种可在保证亮度的前提下弥补 LED 电压差值的一种 LED背光驱动方法、 液晶显示装置及 LED背光驱动电路。
本发明的目的是通过以下技术方案来实现的：
一种 LED背光驱动方法， 其步骤包括：
A: 通过调节 LED串的电流大小， 使每条 LED串的电压相等；
B: 通过调节相应 LED串的电流占空比， 使每条 LED 串的电流有效值达 到预设的亮度要求。 优选的， 所述步骤 A包括以下步骤： 检测电压最小的 LED串的电压值， 通过调节各 LED串的电流大小使各 LED串的电压为上述电压值。此方法可以获 得较低的功率， 减少能耗。
优选的， 所述步骤 B中所述 LED串的电流占空比小于 80%, 在此范围内 可以获得较宽的调节范围。
优选的， 所述步骤 A包括以下步骤： 检测电压最大的 LED串的电压值， 通过调节各 LED串的电流大小使各 LED串的电压为上述电压值。此方法可以获 得较高的亮度。
优选的， 所述步骤 A包括以下步骤： 检测各 LED串的电压平均值， 通过 调节各 LED串的电流大小使各 LED串的电压为上述电压平均值。此方法以平均 值为基准， 可以获得较宽的调节范围。
优选的， 所述步骤 B后面还包括步骤 C: 将均流后的电流有效值反馈回给 LED 串供电的电源模块， 电源模块根据当前亮度所需的电流有效值实时调整输 出电压， 然后重复步骤 A~C。 此方法可以保证调整后的 LED灯的亮度符合预设 要求。
优选的， 所述步骤 B 后面还包括步骤 D: 判断电流有效值调整是否超出 LED串占空比的调节范围， 如果是， LED背光驱动电路转入恒流控制方式， 即 所有 LED串的电流大小和占空比都保持一致； 如果否， 返回步骤 。 此方法可 以在超出 LED串占空比的调节范围的时候， 自动采用现有技术常用的恒流控制 方式， 以保障 LED背光驱动电路还能正常工作。
一种 LED背光驱动电路，包括多条并联的 LED串及为其供电的电源模块， 每个 LED串包括多个串联的 LED灯， 所述 LED背光驱动电路还包括用于调节 LED串的电流大小， 使每条 LED串的电压相等的电流调节模块， 以及通过调节 相应 LED串的电流占空比，使每条 LED串的电流有效值达到亮度要求的占空比 调节模块。
优选的， 所述电流调节模块包括检测各条 LED 串的电压的电压检测电路 及电流检测电路， 还包括以根据电压检测电路获得的一基准电压为基准， 调节 各 LED串的电流大小的控制电路。 此为电流调节模块的一种具体实施方式。
一种液晶显示装置， 其特征在于所述液晶显示装置包括上述 LED 背光驱 动电路。
本发明通过降低单颗 LED的电流 If降低单颗 LED灯的电压 Vf;通过降低 LED串电压 Vfs大的 LED串电流， 降低其 LED串电压 Vfs ,使 LED串电压 Vfs 大的 LED串与 LED串电压 Vfs小的匹配，可以使不同 LED串的 LED的电压匹 配， 减小压差， 减小加在恒流 MOSFET上的电压， 降低损耗， 提高效率； 而不 同 LED串的电流有效值相等， 也能保证 LED亮度的一致性。
【附图说明】
图 1是现有技术 LED背光驱动方式示意图；
图 2是现有技术 LED背光驱动电流波形示意图；
图 3是本发明单颗 LED的电压 Vf与流过 LED的电流 If的关系图； 图 4是本发明 LED的流明和电流 If的关系图；
图 5是本发明实施例 LED驱动方法流程图；
图 5是本发明实施例 LED驱动电路原理框图；
图 6是本发明实施例 LED背光驱动电流波形示意图。
其中： 1、 LED 串； 2、 电流调节模块； 21、 电压检测电路； 22、 电流检测 电路； 23、 控制电路； 3、 占空比调节模块。
【具体实施方式】
下面结合附图和较佳的实施例对本发明作进一步说明。
本发明 LED背光驱动方法的发明构思如下：
通过分析单颗 LED的电压 Vf与流过 LED的电流 If的关系可知， 流过 LED 的电流 If越小， 其单颗 LED的电压 Vf也越小。通过降低 LED的电流 If可降低 电压 Vf; 而通过降低 LED串 1电压 Vfs大的电流， 降低其电压 Vfs, 即可使电 压 Vfs大的 LED串 1与电压 Vfs小的匹配，减小不同 LED串 1的电压差 Δ Vfs, 减小加在恒流 MOSFET上的电压， 降低损耗， 提高效率。
如图 3、 4所示， LED的相对发光强度及流明和电流 If 的关系如图 3、 图 4 所示： 正向电流越大， 其相对发光强度越大、 流明越大， 正向电流越小， 其相 对发光强度越小、 流明越小。 由于不同串的 LED的电压 Vfs不同， 差值会加在 恒流 MOSFET上， 通过减小电压 Vfs比较大的 LED串 1的电流， 降低其单个 LED的电压 Vf, 使不同串的电压 Vfs接近， 减小了电压差△ Vfs, 这样便能减小 加在恒流 MOSFET上的电压。 但由于 LED电流变小， 在同样占空比的情况下， 流明变小。 所以可通过增大占空比来增大电流的有效值， 增加流明， 因此， 虽 然每个 LED串 1的电流大小不同， 但通过调节占空比， 可以保障每个 LED串 1 的电流有效值相等， 以获得相同的亮度。 本发明构思可以较好的应用于 LED串 1的电压 Vfs差值不大的场合。 根据上述原理， 如图 5所示， 本实施例所示的 LED背光驱动方法包括以下 步骤：
A: 通过调节 LED串 1的电流大小， 使每条 LED串 1的电压相等；
B: 通过调节相应 LED串 1的电流占空比， 使每条 LED串 1的电流有效值 达到预设的亮度要求。
下面结合具体实施方式进一步阐释本发明的 LED驱动方法。
实施例一：
先执行步骤 A: 以最小电压为基准， 检测电压最小的 LED 串 1的电压值， 通过调节各 LED串 1的电流大小使各 LED串 1的电压为上述电压值。再执行步 骤 B: 通过调节相应 LED串 1的电流占空比，使每条 LED串 1的电流有效值达 到预设的亮度要求。 该方法中所述 LED串 1的电流占空比最好小于 80%, 这样 可以保障有较宽的调节范围。 以 LED串 1的最小电压值为基准， 可以获得较低 的功耗。
为了防止在将占空比调整到最大值时， 仍不能保证 LED 的亮度符合要求， 所述步骤 B后面还可包括步骤 C: 将均流后的电流有效值反馈回给 LED串 1供 电的电源模块， 电源模块根据当前亮度所需的电流有效值实时调整输出电压， 然后重复步骤 A~C。
为了在电流有效值调整超出 LED串 1 占空比的调节范围的时候， LED背光 驱动电路还能正常工作， 所述步骤 B后面还可包括步骤 D: 判断电流有效值调 整是否超出 LED串 1占空比的调节范围， 如果是， LED背光驱动电路转入恒流 控制方式， 即所有 LED串 1的电流大小和占空比都保持一致； 如果否， 返回步 骤 A。 实施例二：
同样的， 先执行步骤 A, 所述步骤 A包括以下步骤： 检测电压最大的 LED 串 1的电压值，通过调节各 LED串 1的电流大小使各 LED串 1的电压为上述电 压值。 再执行步骤 B: 通过调节相应 LED串 1的电流占空比， 使每条 LED串 1 的电流有效值达到预设的亮度要求。 本实施例是以 LED串 1的最大电压值为基 准。
同样的， 为了保证 LED的亮度符合要求， 所述步骤 B后面还包括步骤 C: 将均流后的电流有效值反馈回给 LED串 1供电的电源模块， 电源模块根据当前 亮度所需的电流有效值实时调整输出电压， 然后重复步骤 A~C。
为了在电流有效值调整超出 LED串 1 占空比的调节范围的时候， LED背光 驱动电路还能正常工作， 所述步骤 B后面还包括步骤 D: 判断电流有效值调整 是否超出 LED串 1占空比的调节范围， 如果是， LED背光驱动电路转入恒流控 制方式， 即所有 LED串 1的电流大小和占空比都保持一致； 如果否， 返回步骤 A。 实施例三：
同样的， 先执行步骤 A, 所述步骤 A包括以下步骤： 检测计算各 LED 串 1 的电压平均值，通过调节各 LED串 1的电流大小使各 LED串 1的电压为上述电 压平均值。 再执行步骤 B: 通过调节相应 LED串 1的电流占空比， 使每条 LED 串 1的电流有效值达到预设的亮度要求。 本实施例是以 LED串 1的电压平均值 为基准， 可以获得较宽的调节范围。
同样的， 为了保证 LED的亮度符合要求， 所述步骤 B后面还包括步骤 C: 将均流后的电流有效值反馈回给 LED串 1供电的电源模块， 电源模块根据当前 亮度所需的电流有效值实时调整输出电压， 然后重复步骤 A~C。
为了在电流有效值调整超出 LED串 1 占空比的调节范围的时候， LED背光 驱动电路还能正常工作， 所述步骤 B后面还包括步骤 D: 判断电流有效值调整 是否超出 LED串 1占空比的调节范围， 如果是， LED背光驱动电路转入恒流控 制方式， 即所有 LED串 1的电流大小和占空比都保持一致； 如果否， 返回步骤 A。 使用上述 LED背光驱动方法的液晶显示装置的 LED背光驱动电路的结构如 图 6所示， LED背光驱动电路包括多条并联的 LED串 1及为其供电的电源模块， 每个 LED串 1包括多个串联的 LED灯， 其特征在于还包括用于调节 LED串 1 的电流大小， 使每条 LED串 1的电压相等的电流调节模块 2, 以及通过调节相 应 LED串 1的电流占空比，使每条 LED串 1的电流有效值达到亮度要求的占空 比调节模块 3。 其调整后的电流波形如图 7所示。 优选的， 所述电流调节模块 2 包括检测各条 LED串 1的电压的电压检测电路 21及电流检测电路 22 , 还包括 以根据电压检测电路获得的一基准电压为基准， 调节各 LED串 1的电流大小的 控制电路 23。
以上内容是结合具体的优选实施方式对本发明所作的进一步详细说明， 不能 认定本发明的具体实施只局限于这些说明。 对于本发明所属技术领域的普通技 术人员来说， 在不脱离本发明构思的前提下， 还可以做出若干筒单推演或替换, 都应当视为属于本发明的保护范围。

Claims

权利要求
1、 一种 LED背光驱动方法， 其步骤包括：
A: 通过调节 LED串的电流大小， 使每条 LED串的电压相等； B: 通过调节相应 LED串的电流占空比，使每条 LED串的电流有效值 达到预设的亮度要求。
2、 如权利要求 1所述的一种 LED背光驱动方法， 其特征在于所述步 骤 A包括以下步骤： 检测电压最小的 LED串的电压值， 通过调节各 LED 串的电流大小使各 LED串的电压为上述电压值。
3、 如权利要求 2任一所述的一种 LED背光驱动方法， 其特征在于所 述步骤 B中所述 LED串的电流占空比小于 80%。
4、 如权利要求 1所述的一种 LED背光驱动方法， 其特征在于所述步 骤 A包括以下步骤： 检测电压最大的 LED串的电压值， 通过调节各 LED 串的电流大小使各 LED串的电压为上述电压值。
5、 如权利要求 1所述的一种 LED背光驱动方法， 其特征在于所述步 骤 A包括以下步骤： 检测各 LED串的电压平均值， 通过调节各 LED串的 电流大小使各 LED串的电压为上述电压平均值。
6、 如权利要求 1所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 C:将均流后的电流有效值反馈回给 LED串供电的电 源模块， 电源模块根据当前亮度所需的电流有效值实时调整输出电压， 然 后重复步骤 A~C。
7、 如权利要求 2所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 C:将均流后的电流有效值反馈回给 LED串供电的电 源模块， 电源模块根据当前亮度所需的电流有效值实时调整输出电压， 然 后重复步骤 A~C。
8、 如权利要求 3所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 C:将均流后的电流有效值反馈回给 LED串供电的电 源模块， 电源模块根据当前亮度所需的电流有效值实时调整输出电压， 然 后重复步骤 A~C。
9、 如权利要求 4所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 C:将均流后的电流有效值反馈回给 LED串供电的电 源模块， 电源模块根据当前亮度所需的电流有效值实时调整输出电压， 然 后重复步骤 A~C。
10、如权利要求 5所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 C:将均流后的电流有效值反馈回给 LED串供电的电 源模块， 电源模块根据当前亮度所需的电流有效值实时调整输出电压， 然 后重复步骤 A~C。
11、如权利要求 1所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 D:判断电流有效值调整是否超出 LED串占空比的调 节范围， 如果是， LED背光驱动电路转入恒流控制方式， 即所有 LED串的 电流大小和占空比都保持一致； 如果否， 返回步骤 。
12、如权利要求 2所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 D:判断电流有效值调整是否超出 LED串占空比的调 节范围， 如果是， LED背光驱动电路转入恒流控制方式， 即所有 LED串的 电流大小和占空比都保持一致； 如果否， 返回步骤 。
13、如权利要求 3所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 D:判断电流有效值调整是否超出 LED串占空比的调 节范围， 如果是， LED背光驱动电路转入恒流控制方式， 即所有 LED串的 电流大小和占空比都保持一致； 如果否， 返回步骤 。
14、如权利要求 4所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 D:判断电流有效值调整是否超出 LED串占空比的调 节范围， 如果是， LED背光驱动电路转入恒流控制方式， 即所有 LED串的 电流大小和占空比都保持一致； 如果否， 返回步骤 。
15、如权利要求 5所述的一种 LED背光驱动方法， 其特征在于所述步 骤 B后面还包括步骤 D:判断电流有效值调整是否超出 LED串占空比的调 节范围， 如果是， LED背光驱动电路转入恒流控制方式， 即所有 LED串的 电流大小和占空比都保持一致； 如果否， 返回步骤 。
16、 一种 LED背光驱动电路， 包括： 多条并联的 LED串， 所述每个 LED串包括多个串联的 LED灯； 为其供电的电源模块； 用于调节 LED串 的电流大小， 使每条 LED串的电压相等的电流调节模块； 以及通过调节相 应 LED 串的电流占空比， 使每条 LED 串的电流有效值达到亮度要求的占 空比调节模块。
17、 如权利要求 16所述的 LED背光驱动电路， 其特征在于所述电流 调节模块包括检测各条 LED串的电压的电压检测电路及电流检测电路，还 包括以根据电压检测电路获得的一基准电压为基准，调节各 LED串的电流 大小的控制电路。
18、 一种液晶显示装置， 包括： 如权利要求 16所述的 LED背光驱动 电路； 所述 LED背光驱动电路包括： 多条并联的 LED串， 所述每个 LED 串包括多个串联的 LED灯； 为其供电的电源模块； 用于调节 LED 串的电 流大小， 使每条 LED 串的电压相等的电流调节模块； 以及通过调节相应 LED串的电流占空比，使每条 LED串的电流有效值达到亮度要求的占空比 调节模块。
19、如权利要求 18所述的液晶显示装置， 其特征在于所述电流调节模 块包括检测各条 LED串的电压的电压检测电路及电流检测电路，还包括以 根据电压检测电路获得的一基准电压为基准，调节各 LED串的电流大小的 控制电路。
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