WO2013013430A1 - 一种led调光的方法及led调光系统 - Google Patents

一种led调光的方法及led调光系统 Download PDF

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Publication number
WO2013013430A1
WO2013013430A1 PCT/CN2011/078598 CN2011078598W WO2013013430A1 WO 2013013430 A1 WO2013013430 A1 WO 2013013430A1 CN 2011078598 W CN2011078598 W CN 2011078598W WO 2013013430 A1 WO2013013430 A1 WO 2013013430A1
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Prior art keywords
led
duty ratio
ratio information
current
equivalent
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PCT/CN2011/078598
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English (en)
French (fr)
Inventor
黎飞
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深圳市华星光电技术有限公司
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Priority to US13/375,477 priority Critical patent/US8686661B2/en
Publication of WO2013013430A1 publication Critical patent/WO2013013430A1/zh

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits

Definitions

  • the present invention relates to the field of liquid crystal display devices, and more particularly to a method for dimming LEDs and an LED dimming system for a liquid crystal display device.
  • the quality of the LED backlight affects the stability, luminosity and color of the image, so it is one of the most important components in the LCD.
  • LEDs are rapidly replacing CCFL technology. The reason is that LEDs have lower voltage requirements, and the cartridges are easy to use, have high dimming capability, are not mercury-containing, and are more efficient. As LEDs continue to improve in terms of luminosity and cost, they are increasingly being used in larger liquid crystal displays.
  • the dimming method of the LED backlight is PWM (Pulse Width Modulation) dimming
  • the current of the LED is the maximum value in the PWM positive duty ratio
  • the average current of the LED is adjusted by changing the positive duty ratio, so that the LED backlight is adjusted.
  • Light E.g:
  • the PWM dimming frequency is generally between 100 and 500 Hz. These are in the range that can be heard by the human ear. Since a low-frequency switching signal acts on the winding inductance, mechanical vibrations are generated between the turns in the inductor. The frequency is exactly at the above frequency, and the noise from the inductor can be heard by the human ear. At the same time, due to the fixed delay in PWM dimming, a part of the fixed period is lost, so that the dimming degree is reduced.
  • the technical problem to be solved by the present invention is to provide an LED backlight driving method and apparatus thereof that are noiseless and have high dimming uniformity.
  • a method for LED dimming comprising the following steps:
  • A Calculate the equivalent current value flowing through the LED according to the duty ratio information of the input PWM signal
  • step B Adjust the current flowing through the LED to the equivalent current value in step A.
  • adjusting the current flowing through the LED is to compare the equivalent current value calculated in the step A as a comparison reference, adjusting the output voltage, and comparing the current flowing through the LED with the comparison reference. , making the current flowing through the LED equal to the comparison reference.
  • the feedback current is compared with the calculated equivalent current value, and the method is single.
  • the process of adjusting the current flowing through the LED is performed by calculating the corresponding voltage value of the above-mentioned equivalent current value, and adjusting the output voltage for the LED according to the corresponding voltage value. Adjusting the linear variation of the output voltage allows the LED current to vary linearly. This adjustment method is simpler.
  • An LED dimming system including an LED, further comprising:
  • a duty ratio information input module configured to receive duty cycle information of the input PWM signal
  • a duty ratio information equivalent current calculation module connected to the duty ratio information input module, configured to calculate an equivalent current value flowing through the LED according to the duty ratio information obtained by the duty ratio information input module;
  • the current adjustment module is connected with the LED and the duty ratio information equivalent current calculation module, and is used for adjusting the current flowing through the LED as the equivalent current value obtained by the duty ratio information equivalent current calculation module.
  • the current regulation module includes:
  • a voltage regulation module that can regulate an output voltage of the LED
  • a comparator connected to the LED, the duty ratio information equivalent current calculation module and the voltage adjustment module; the comparator is configured to use the equivalent current value calculated by the equivalent current calculation module as a comparison reference, and to flow through the LED Current values are compared;
  • the voltage adjustment module adjusts an output voltage for the LED according to a comparison result of the comparator, so that the current flowing through the LED is an equivalent current value obtained by the duty ratio information equivalent current calculation module.
  • the current adjustment is performed by the comparator and is accurate.
  • the current adjustment module comprises:
  • An equivalent voltage calculation module connected to the duty ratio information equivalent current calculation module for calculating a corresponding voltage value of the equivalent current value obtained by the duty ratio information equivalent current calculation module;
  • a voltage adjustment module respectively connected to the LED and the equivalent voltage calculation module for adjusting the output voltage of the LED according to the corresponding voltage value obtained by the voltage regulation module.
  • the invention equivalently calculates the equivalent current flowing through the LED through the duty ratio information D of the input PWM signal, but does not really adjust the duty ratio, thereby linearly adjusting the current variation flowing through the LED, so that the dimming is performed.
  • the uniformity is improved and no transformer noise is generated due to the current flowing through the transformer during the entire dimming cycle.
  • FIG. 1 is a schematic flow chart of a method for dimming an LED according to an embodiment of the present invention
  • FIG. 2 is a flow chart showing another method of dimming LEDs according to an embodiment of the present invention.
  • FIG. 3 is a block diagram of an LED dimming system according to an embodiment of the present invention.
  • Fig. 4 is a block diagram showing another module of the LED dimming system of the embodiment of the present invention.
  • A calculating an equivalent current value flowing through the LED according to the duty ratio information of the input PWM signal; wherein, the duty ratio of the input PWM signal multiplied by the maximum current is equal to the equivalent current value;
  • step B Adjust the current flowing through the LED to the equivalent current value in step A.
  • w Vf*If*l/f*D, where Vf is the output voltage and If is the flowing LED
  • D is the duty cycle of the PWM signal; Due to the characteristics of the LED itself, the voltage and current of the LED are not linearly proportional to the brightness. Therefore, directly adjusting the current or voltage flowing through the LED cannot achieve 0-100% linearity. The process of the change; but the adjustment of the duty cycle can achieve a linear change of 0-100% of the brightness, therefore, if the adjustment mode of the duty ratio D of the input PWM signal is referred to, the duty ratio D is not adjusted.
  • the equivalent current value flowing through the LED is calculated according to the information of the duty ratio; then, according to the current value flowing through the LED, a linear change process of the brightness can be obtained, so that the dimming uniformity is improved. Moreover, since a current flows through the transformer throughout the dimming period, that is, D is 100%, the inductance turns will not cause mechanical vibration, and thus no transformer noise will be generated.
  • step B the current flowing through the LED can be adjusted in step B, and the equivalent current value calculated in the step A is used as a comparison reference. Adjusting the output voltage, comparing the current flowing through the LED with the comparison reference, and adjusting the current flowing through the LED in a manner that the current flowing through the LED is equal to the comparison reference, as shown in FIG. 1; The process of adjusting the current flowing through the LED is performed by calculating the corresponding voltage value of the above equivalent current value, and adjusting the output voltage of the LED according to the corresponding voltage value, thereby realizing the adjustment of the current flowing through the LED, as shown in FIG. 2 Show.
  • the LED dimming system for realizing the above dimming method comprises: an LED, a duty ratio information input module, a duty ratio information equivalent current calculation module connected to the duty ratio information input module, and an LED and duty ratio information, etc.
  • the effective current calculation module controls the connected current adjustment module; wherein the duty ratio information input module is configured to receive duty ratio information of the input PWM signal; and the duty ratio information equivalent current calculation module is used to calculate The duty ratio information obtained by the ratio information input module calculates the equivalent current value flowing through the LED; the current adjustment module is used to adjust the current flowing through the LED as the duty ratio information equivalent current calculation module Equivalent current value.
  • the current adjustment module can be as shown in FIG. 3, and includes: a voltage adjustment module that can adjust an output voltage of the LED; and is connected to the LED, the duty ratio information equivalent current calculation module, and the voltage adjustment module. a comparator; the comparator is configured to compare an equivalent current value calculated by the equivalent current calculation module with a current value flowing through the LED; the voltage adjustment module root According to the comparison result of the comparator, the output voltage for the LED is adjusted so that the current flowing through the LED is the equivalent current value obtained by the duty ratio information equivalent current calculation module, and the dimming is completed.
  • the current adjustment module may also be as shown in FIG. 4, and includes: an equivalent voltage calculation module connected to the duty ratio information equivalent current calculation module, and a control connection with the LED and the equivalent voltage calculation module respectively. a voltage adjustment module, wherein the equivalent voltage calculation module is configured to calculate a corresponding voltage value of an equivalent current value obtained by the duty ratio information equivalent current calculation module; and the voltage adjustment module is configured to obtain a voltage adjustment module according to the voltage adjustment module The corresponding voltage value is adjusted for the output voltage of this LED. By adjusting the voltage regulation module set in the LED dimming system, the output voltage changes linearly, resulting in a change in current linearity.
  • the duty ratio information equivalent current calculation module calculates the equivalent current value by 45 mA through the multiplier calculation and

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  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

一种LED调光的方法及LED调光系统，LED调光的方法包括步骤：根据输入的PWM信号的占空比信息，计算出流过的LED的等效电流值（A）；调节流过LED的电流为等效电流值（B）。由于通过输入的PWM信号的占空比信息D来等效计算出LED流过的等效电流，而不对占空比进行调节，从而实现线性调节流过LED的电流变化，提高了调光均匀度，由于在整个调光周期中变压器都有电流流过，也不会产生变压器噪声。

Description

种 LED调光的方法及 LED调光系统
【技术领域】
本发明涉及液晶显示装置领域，更具体的说，涉及一种液晶显示装置的 LED 调光的方法及 LED调光系统。
【背景技术】
LED背光的质量影响着图像的稳定性、 光度和颜色， 因此可说是液晶显示 器中最重要的组件之一。 在现今的背光照明设计中， LED正迅速取代 CCFL技 术。 原因是 LED对电压的要求较低、 而且筒单易用， 调光能力强， 不含水银而 且效率更高。 随着 LED在光度和成本方面的不断改进， 它们逐渐应用于较大型 的液晶显示器中。
目前 LED背光源的调光方法为 PWM (脉沖宽度调制）调光， 在 PWM正 占空比内 LED的电流为最大值，通过改变正占空比来调节 LED的平均电流，使 LED背光源实现调光。 例如：
假设 LED的 Vf=3.3V, If=60mA,调光频率 f=100Hz,调光占空比 D=50%, 假如 LED 的发光亮度以平均功率来衡量， 那么最大亮度所对应的功率是 w=Vf*If*l/f=3.3 0.06 l/100=1.98mW, 调光占空比 D=50%时的发光亮度所对 应的发光功率为 w=3.3 X 0.06 X 1/100 x l/2=0.99mW, 可以看出， 占空比 D对应 于发光功率变化。
PWM调光频率一般在 100 ~ 500Hz, 这些都处于人耳能够听见的范围， 由 于一个低频的开关信号作用于绕线电感时， 会使得电感中的线圏之间互相产生 机械振动， 该机械振动的频率正好落在上述频率， 电感发出的噪音就能够被人 耳所听见。 同时由于 PWM调光中的固定延迟， 损耗掉一部分固定周期， 使得调 光均勾度降低。
【发明内容】 本发明所要解决的技术问题是提供一种无噪音且调光均匀度高的 LED 背 光驱动方法及其装置。
本发明一种 LED调光方法的目的是通过以下技术方案来实现的： 一种 LED调光的方法， 其中， 包括以下步骤：
A:根据输入的 PWM信号的占空比信息，计算出流过 LED 的等效电流值；
B: 调节流过 LED的电流为步骤 A中的等效电流值。
优选的， 所述步骤 B中， 调节流过 LED的电流是将所述步骤 A中计算出 的等效电流值作为比较基准， 调节输出电压， 将流过 LED的电流与所述比较基 准进行比较， 使流过 LED的电流与所述比较基准相等。 通过反馈电流与计算得 出的等效电流值进行比较， 方法筒单。
优选的， 所述的步骤 B中， 调节流过 LED的电流的过程是通过对上述等 效电流值进行对应电压值的计算， 并根据此对应电压值调节针对此 LED的输出 电压实现的。 调节输出电压线性变化， 可使得 LED电流线性变化， 这种调节方 法较为筒单。
本发明一种 LED调光系统的目的是通过以下技术方案来实现的： 一种 LED调光系统， 包括 LED, 还包括：
占空比信息输入模块， 用于接收输入 PWM信号的占空比信息；
与占空比信息输入模块连接的占空比信息等效电流计算模块， 用于根据占 空比信息输入模块获得的占空比信息， 计算出流过 LED 的等效电流值；
与 LED及占空比信息等效电流计算模块控制连接的电流调节模块， 用于 调节流过 LED的电流为占空比信息等效电流计算模块得出的等效电流值。
所述的电流调节模块包括：
可对针对 LED的输出电压进行调节的电压调节模块；
与 LED、 占空比信息等效电流计算模块及电压调节模块连接的比较器； 所述比较器用于将等效电流计算模块所计算得出的等效电流值作为比较 基准， 与流过 LED的电流值进行比较； 所述电压调节模块根据比较器的比较结果， 调节针对 LED 的输出电压， 使得流过 LED的电流为占空比信息等效电流计算模块得出的等效电流值。 通过 比较器来进行电流调节筒单而准确。
优选的， 所述的电流调节模块包括：
与占空比信息等效电流计算模块控制连接的等效电压计算模块， 用于计算 出占空比信息等效电流计算模块得出的等效电流值的对应电压值；
及与 LED、 等效电压计算模块分别控制连接的电压调节模块， 用于根据电 压调节模块得出的对应电压值调整针对此 LED的输出电压。
本发明由于通过输入的 PWM信号的占空比信息 D来等效计算出 LED流 过的等效电流， 却并不真正调节占空比， 从而实现线性调节流过 LED的电流变 化， 使得调光均匀度得以提高， 同时由于在整个调光周期中变压器都有电流流 过， 也不会产生变压器噪音。
【附图说明】
图 1是本发明实施例 LED调光的方法的流程示意图，
图 2是本发明实施例 LED调光的另一种方法流程示意图，
图 3是本发明实施例 LED调光系统的模块示意图，
图 4是本发明实施例 LED调光系统的另一种模块示意图。
【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。
本发明实施例中所述的 LED调光的方法包括以下步骤：
A: 根据输入的 PWM信号的占空比信息，计算出流过 LED 的等效电流值； 其中， 输入的 PWM信号的占空比乘以最大电流即等于等效电流值；
B: 调节流过 LED的电流为步骤 A中的等效电流值。
根据 LED的发光功率， w=Vf*If*l/f*D,式中 Vf为输出电压， If为流过 LED 的电流， D为 PWM信号占空比； 由于 LED本身的特性， LED的电压与电流与 亮度不是线性的比例关系， 因此直接调节流过 LED的电流或电压， 是不能获得 0-100%的线性变化过程的； 但对占空比的调节却可以实现亮度的 0-100%的线性 变化， 因此， 若参照对输入的 PWM信号的占空比 D的调节模式， 却并不调节 占空比 D, 而是根据占空比的信息计算出流过 LED 的等效电流值； 再按照此调 节流过 LED 的电流值， 即可以获得亮度的线性变化过程， 使得调光均匀度得以 提高。 而且由于在整个调光周期内都有电流流过变压器， 即使得 D为 100%, 电 感线圏将不会发生机械振动， 因而也就不会产生变压器（transformer )噪音。
而假如更改 Vf, If 也会随着改变， 因此， 步骤 B 中， 可通过所述步骤 B 中，调节流过 LED的电流是将所述步骤 A中计算出的等效电流值作为比较基准， 调节输出电压，将流过 LED的电流与所述比较基准进行比较，使流过 LED的电 流与所述比较基准相等的方式实现对流过 LED的电流的调节， 如图 1所示； 也 可以通过调节流过 LED的电流的过程是通过对上述等效电流值进行对应电压值 的计算，并根据此对应电压值调节针对此 LED的输出电压， 实现对流过 LED的 电流的调节， 如图 2所示。
实现上述调光方法的 LED调光系统包括有： LED, 占空比信息输入模块、 与占空比信息输入模块连接的占空比信息等效电流计算模块、 及与 LED及占空 比信息等效电流计算模块控制连接的电流调节模块； 其中， 所述的占空比信息 输入模块用于接收输入 PWM信号的占空比信息；所述的占空比信息等效电流计 算模块用于根据占空比信息输入模块获得的占空比信息，计算出流过 LED 的等 效电流值； 所述的电流调节模块用于调节流过 LED的电流为占空比信息等效电 流计算模块得出的等效电流值。
其中， 所述电流调节模块可如图 3中所示， 其包括： 可对针对 LED的输出 电压进行调节的电压调节模块； 与 LED、 占空比信息等效电流计算模块及电压 调节模块连接的比较器； 所述比较器用于将等效电流计算模块所计算得出的等 效电流值作为比较基准， 与流过 LED的电流值进行比较； 所述电压调节模块根 据比较器的比较结果，调节针对 LED的输出电压，使得流过 LED的电流为占空 比信息等效电流计算模块得出的等效电流值， 完成调光。
所述的电流调节模块也可以如图 4 中所示， 其包括： 与占空比信息等效电 流计算模块控制连接的等效电压计算模块、 及与 LED、 等效电压计算模块分别 控制连接的电压调节模块， 所述的等效电压计算模块用于计算出占空比信息等 效电流计算模块得出的等效电流值的对应电压值； 所述的电压调节模块用于根 据电压调节模块得出的对应电压值调整针对此 LED的输出电压。 通过调节设置 在 LED调光系统中的电压调节模块， 使输出电压线性的变化， 从而使得电流线 性的变化。
以图 3 所示的电流调节方式为例， 设有一串 LED 的正常工作 （正占空比 D=100% )电流为 60mA, 工作电压为 30V, 若调光， 设在正占空比 D=50%的情 形下， 调光频率为 100Hz, 这时发光功率为 W=0.06 X 30 X 0.5 x l/100=9mW。 而 若不调节占空比 D, 而将其进行等效： 占空比信息输入模块获得 D=50%, 占空 比信息等效电流计算模块通过乘法器计算确定等效电流值为 45mA并以此作为 比较器的基准， 通过电压调节模块直接调节输出电压使流过 LED的电流值等于 所述比较器的基准即等效电流值 45mA, 而此时输出电压为 20V, 发光功率 W=0.045 X 20 X l/100=9mW, 这样同样实现了等同于 D=50%的情形下的调光， 但是此时电流却是在整个调光周期中保持线性变化的， 调光均勾度得以提高， 而且由于在整个调光周期内都有电流流过变压器， 也不会产生变压器噪音。 . 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调光的方法， 包括以下步骤：
A: 根据输入的 PWM信号的占空比信息，计算出流过 LED 的等效电流值； B: 调节流过 LED的电流为步骤 A中的等效电流值。
2、 如权利要求 1所述的一种 LED调光的方法， 其特征在于， 所述步骤 B 中，调节流过 LED的电流是将所述步骤 A中计算出的等效电流值作为比较基准， 调节输出电压，将流过 LED的电流与所述比较基准进行比较，使流过 LED的电 流与所述比较基准相等。
3、 如权利要求 1所述的一种 LED调光的方法， 其特征在于， 所述的步骤 B 中， 调节流过 LED的电流的过程是通过对上述等效电流值进行对应电压值的计 算， 并根据此对应电压值调节针对此 LED的输出电压实现的。
4、 一种 LED调光系统， 包括： LED;
占空比信息输入模块， 用于接收输入 PWM信号的占空比信息；
与占空比信息输入模块连接的占空比信息等效电流计算模块， 用于根据占 空比信息输入模块获得的占空比信息， 计算出流过 LED 的等效电流值； 以及， 与 LED及占空比信息等效电流计算模块控制连接的电流调节模块， 用于调 节流过 LED的电流为占空比信息等效电流计算模块得出的等效电流值。
5、 如权利要求 4所述的一种 LED调光系统， 其特征在于， 所述的电流调 节模块包括：
可对针对 LED的输出电压进行调节的电压调节模块；
与 LED、 占空比信息等效电流计算模块及电压调节模块连接的比较器； 所述比较器用于将等效电流计算模块所计算得出的等效电流值作为比较基 准， 与流过 LED的电流值进行比较；
所述电压调节模块根据比较器的比较结果， 调节针对 LED的输出电压， 使 得流过 LED的电流为占空比信息等效电流计算模块得出的等效电流值。
6、 如权利要求 4所述的一种 LED调光系统， 其特征在于， 所述的电流调 节模块包括：
与占空比信息等效电流计算模块控制连接的等效电压计算模块， 用于计算 出占空比信息等效电流计算模块得出的等效电流值的对应电压值；
及与 LED、 等效电压计算模块分别控制连接的电压调节模块， 用于根据电 压调节模块得出的对应电压值调整针对此 LED的输出电压。
PCT/CN2011/078598 2011-07-26 2011-08-18 一种led调光的方法及led调光系统 WO2013013430A1 (zh)

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