WO2016086675A1 - 一种电流型lcd背光升压方法、电路 - Google Patents

一种电流型lcd背光升压方法、电路 Download PDF

Info

Publication number
WO2016086675A1
WO2016086675A1 PCT/CN2015/085468 CN2015085468W WO2016086675A1 WO 2016086675 A1 WO2016086675 A1 WO 2016086675A1 CN 2015085468 W CN2015085468 W CN 2015085468W WO 2016086675 A1 WO2016086675 A1 WO 2016086675A1
Authority
WO
WIPO (PCT)
Prior art keywords
circuit
current
inductor
lcd backlight
diode
Prior art date
Application number
PCT/CN2015/085468
Other languages
English (en)
French (fr)
Inventor
程微
Original Assignee
中兴通讯股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 中兴通讯股份有限公司 filed Critical 中兴通讯股份有限公司
Publication of WO2016086675A1 publication Critical patent/WO2016086675A1/zh

Links

Images

Classifications

    • 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
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light 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
    • 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

Definitions

  • the present invention relates to the field of communications, and in particular, to a current-type LCD backlight boosting method and circuit.
  • the liquid crystal display (LCD) backlight of a mobile terminal product such as a smart phone or a tablet computer
  • LCD liquid crystal display
  • LEDs Light Emitting Diodes
  • FIG. 1 is a block diagram of a conventional backlight boosting circuit according to the related art.
  • a DC converter Direct Current/Direct Current, abbreviated as DC/DC
  • the current is monitored by detecting the voltage across the current-sampling resistor, and the pulse width and duty cycle of the DC/DC are controlled by an error amplifier to achieve a constant current output.
  • the disadvantage of this scheme is that the current sampling resistor has a current through the power loop, so there is a large theoretical power consumption. For example, in the case of an output voltage of 10 V and a sampling voltage of 0.5 V, the power consumption of the sampling resistor reaches 5% of the output power. It is unfavorable for mobile terminals to reduce power consumption.
  • the conventional scheme is a boost-like DC/DC, and the main difference is error sampling. the way.
  • Conventional DC/DC needs to output a constant voltage, so the error is sampled from the output voltage, and the proportional relationship of the output voltage is obtained by the voltage dividing resistor.
  • the LED backlight circuit requires a constant current to drive, and the error sampling is taken from the voltage of the current sampling resistor. Its voltage is proportional to the current.
  • the present invention provides a current-type LCD backlight boosting method and circuit for solving the above technical problem.
  • a current-type LCD backlight boost circuit includes: an LED current control module, an inductor, a diode, a switching transistor, a capacitor, and an LCD backlight LED display;
  • An LED current control module is connected to the input end of the inductor, configured to measure a voltage of the inductor, and obtain a load current value of the circuit based on the voltage, to adjust the circuit based on the load current value, thereby controlling the LCD backlight LED Display drive current;
  • the inductor has an output connected to the input end of the diode and configured to control current and boost;
  • the diode has an output connected to the input end of the capacitor, configured to be turned on when the induced electromotive force of the inductor charges the capacitor, and turned off when the capacitor is not charged;
  • the switching transistor has an input end connected to the output end of the inductor, and is configured to store the inductor during the conducting period;
  • the capacitor is configured to provide a steady current to the LED
  • the LCD backlight LED display has an input end connected to the input end of the capacitor, and the number of LEDs is related to the screen size of the LCD.
  • the LED current control module includes: an integration circuit, a comparator 1, a comparator 2, an analog multiplier, an error amplifier, a duty ratio measurement circuit, a sawtooth generator, and a timing circuit;
  • the timing circuit is connected to one end of the integrating circuit, the duty ratio measuring circuit, and the sawtooth wave generator, and is set to be timed;
  • the integration circuit has another end connected to the analog multiplier and configured to perform an integration operation
  • the duty ratio measuring circuit is connected to the comparator 1 at the other end thereof, and is configured to measure the second The duty cycle during the turn-on of the pole tube;
  • the analog multiplier is connected at one end to the integrating circuit and the duty ratio measuring circuit, and the other end is connected to the error amplifier, and is arranged to compare an average current during the conducting period of the diode with the duty ratio Multiply, the load current value is obtained.
  • the inductance is a power inductor.
  • the diode is a switching diode or a field effect transistor.
  • the capacitor is a filtered storage capacitor.
  • the present invention also provides a current-type LCD backlight boosting method, wherein the method comprises: measuring a voltage across an inductor in a current-type LCD backlight boost circuit, integrating the voltage to obtain a current And obtaining a load current value of the circuit based on the current value; adjusting the circuit based on the load current value to control a driving current of the LCD backlight LED display in the circuit.
  • adjusting the circuit based on the load current value to control a driving current of the LCD backlight LED display in the circuit comprises: adjusting a conduction period of the switching transistor to achieve a preset desired current value.
  • the invention solves the problem that the theoretical power consumption of the driving circuit of the LCD backlight LED itself is large in the related art, effectively avoids the theoretical power consumption of the driving circuit of the LCD backlight LED, and effectively ensures the stable current of the driving circuit output.
  • FIG. 1 is a block diagram of a conventional backlight boost circuit according to the related art
  • FIG. 2 is a block diagram of a current type LCD backlight boosting circuit according to a first embodiment of the present invention
  • FIG. 3 is a schematic diagram of current waveforms of an inductor according to a second embodiment of the present invention.
  • FIG. 4 is a flow chart of a current type LCD backlight boosting method according to a third embodiment of the present invention.
  • the present invention provides a current-type LCD backlight boosting method and circuit, and the present invention is further detailed in conjunction with the accompanying drawings and embodiments. Description. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
  • FIG. 2 is a block diagram of a current-type LCD backlight boosting circuit according to a first embodiment of the present invention.
  • the circuit includes: an LED current control module, an inductor, a diode, a switching transistor, a capacitor, and an LCD backlight LED display. ;among them,
  • the LED current control module is connected to the input end of the inductor, is configured to measure the voltage of the inductor, and obtain a load current value of the circuit based on the voltage, to adjust the circuit based on the load current value, thereby controlling the driving current of the LCD backlight LED display ;
  • An inductor having an output connected to the input end of the diode and configured to control current and boost; preferably, the inductor can be a power inductor;
  • the diode having an output connected to the input end of the capacitor, configured to be turned on when the induced electromotive force of the inductor charges the capacitor, and turned off when the capacitor is not charged; preferably, the diode is a switching diode or a field effect transistor;
  • a switching transistor having an input connected to an output of the inductor and configured to store energy during conduction
  • the capacitor configured to provide a steady current to the LED; preferably, the capacitor is a filtered storage capacitor;
  • the LCD backlight LED display has an input connected to the input of the capacitor, and the number of LEDs is related to the screen size of the LCD.
  • the LED current control module is described below based on FIG. 2, the module includes: an integration circuit, a comparator 1, a comparator 2, an analog multiplier, an error amplifier, a duty ratio measurement circuit, a sawtooth generator, and a timing circuit;
  • the timing circuit is connected to one end of the integrating circuit, the duty ratio measuring circuit, and the sawtooth wave generator, and is set to be timed;
  • the integration circuit is connected to the analog multiplier at the other end and is set to perform an integral operation
  • a duty cycle measuring circuit the other end of which is connected to the comparator 1 and configured to measure a duty ratio during which the diode is turned on;
  • the analog multiplier has one end connected to the integrating circuit and the duty ratio measuring circuit, and the other end connected to the error amplifier, and is set to multiply the average current during the diode conduction period by the duty ratio to obtain the load current value.
  • the current type LCD backlight boosting circuit further includes a power supply and a power tube driving circuit, and the functions of the two are the same as those in the conventional backlight boosting circuit, and will not be described in detail herein.
  • a current-type LCD backlight boost circuit without a sampling resistor will be described below by way of a preferred embodiment.
  • Mobile terminal products usually use a single-cell lithium battery, and the working voltage is usually between 3V and 4.2V.
  • the backlight LED of the LCD needs a constant current to drive to obtain a pure color temperature.
  • the mobile product is extremely sensitive to power consumption. Therefore, its drive circuit is usually a DC/DC circuit capable of outputting a stable current.
  • the traditional driver circuit block diagram is shown in Figure 1. Because of the existence of the sampling resistor, the theoretical power consumption is the working power. The product of the stream and the sampled voltage. In order to avoid the sampling resistor, a new current control scheme is proposed in the embodiment of the present invention.
  • the current-type LCD backlight boost circuit without sampling resistor includes the following functional modules:
  • LED current control module including: integral circuit, 2 voltage comparators, analog multiplier, error amplifier, duty cycle measuring circuit, sawtooth wave generator;
  • Module C switching diode or replacement device
  • Module D switching transistor or replacement device
  • the module A controls the operating current of the LED by controlling the switching transistor to be turned on and off.
  • the switching transistor can be a bipolar transistor or a field effect transistor, or it can be other controlled electronic switches.
  • module B is a power inductor, which controls the current and boosts. According to the definition of the inductance:
  • the slope of its current change is V/L. If the starting current of each cycle is 0, then the current is an integral of time. Therefore, the current value can be obtained by integrating the voltage across the inductor.
  • the module C is a switching diode, which is turned on when the induced electromotive force of the inductor charges the storage capacitor, and is turned off when the capacitor is not charged, so as to prevent the electric energy from being discharged from other branches.
  • the switching diode can also be replaced by a synchronous switching circuit such as a field effect transistor.
  • Module D is a switching transistor.
  • the module B——inductor is stored, and the inductor current rises.
  • the inductor releases energy through the diode, thereby supplying current to the LED.
  • module E is a filter storage capacitor to provide a stable current to the LED.
  • module F is an electrical load - LCD backlight LED array, its number of LEDs and LCD Screen size and other related.
  • the inductor current at the end of each on-period of the switching transistor is measured by an integrator, and the duty cycle of the diode conduction is also measured and multiplied. The current through the LED is proportional to the product.
  • the technical solution in the embodiment of the present invention is still a boost-like DC/DC, which is similar to the solution in the related art, and the main difference is the LED current control module.
  • the integration circuit integrates the input voltage and is therefore proportional to the inductor current, as follows:
  • the comparator 1 converts the diode-conducted signal into a constant-amplitude pulse signal, and the duty ratio can be measured by, for example, an integrator.
  • the comparator 2 compares the error signal with the sawtooth signal to obtain a pulse width signal that controls the switching transistor.
  • the average current during diode conduction is: I PEAK /2.
  • the duty cycle of the diode conduction is T LED /T ALL , so the average current (ie load current) is the average current ⁇ duty cycle:
  • the duty cycle of the diode conduction is adjusted, so that the load current value reaches the preset desired current value, and the required constant output current can be obtained.
  • FIG. 3 is a schematic diagram of a current waveform of an inductor according to a second embodiment of the present invention.
  • the T FET of FIG. 3 is a switching transistor conduction period. During this period, the current change slope of the inductor is V IN /L. The peak current is I PEAK .
  • the T LED is the diode conduction period. When the diode is turned on, the inductor charges the LED circuit. The slope of the current change is (V OUT -V IN )/L, then the average current during this time is I PEAK /2.
  • T OFF is the switching transistor and the diode are both cut off, this time needs to be greater than 0 to ensure that the current in the inductor returns to 0, to avoid accumulation error;
  • T ALL is a complete cycle. Including the above three periods, the current of the LED is equal to the average current during the diode conduction period multiplied by the duty ratio of its conduction.
  • the peak current also becomes larger, and the diode conduction period also becomes longer, then the LED current becomes larger, and the LED current becomes smaller.
  • FIG. 4 is a flowchart of a current-type LCD backlight boosting method according to Embodiment 3 of the present invention. As shown in FIG. 4, the method includes the following steps. (Step S402 - Step S406):
  • Step S402 measuring a voltage across the inductor in the current-type LCD backlight boost circuit, and integrating the voltage to obtain a current value
  • Step S404 obtaining a load current value of the circuit based on the current value
  • Step S406 adjusting the circuit based on the load current value to control the driving current of the LCD backlight LED display in the circuit.
  • the load current of the circuit is obtained based on the current value, which can be realized by calculating the slope of the current change during the on-time of the switching transistor in the calculation circuit; and calculating the slope of the current when the switching transistor is turned on, according to the slope of the current change, flowing through the inductor
  • step S406 the circuit is adjusted based on the load current value to control the driving current of the LCD backlight LED display in the circuit, which can be realized by adjusting the conduction period of the switching transistor so that the load current value reaches the preset expectation. Current value.
  • the present invention relates to a constant current output DC/DC circuit without a current sampling resistor for driving a backlight LED of a mobile terminal LCD. It is an object of the present invention to reduce the theoretical power consumption of the drive circuit of the LCD backlight LED itself while ensuring that the drive circuit outputs a stable current.
  • the current-type LCD backlight boosting method and circuit provided by the embodiments of the present invention have the following beneficial effects: solving the problem that the theoretical power consumption of the driving circuit of the LCD backlight LED itself is large in the related art, and effectively avoiding the LCD The theoretical power consumption of the driving circuit of the backlight LED effectively ensures that the driving circuit outputs a stable current.

Abstract

本发明公开了一种电流型LCD背光升压方法、电路。其中，该电路包括：LED电流控制模块、电感、二极管、开关晶体管、电容、LCD背光LED陈列；其中，LED电流控制模块，与电感的输入端相连，设置为测量电感的电压，并基于该电压得到电路的负载电流值，以基于该负载电流值对电路进行调整，从而控制LCD背光LED陈列的驱动电流。通过本发明，解决了相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问题，有效避免LCD背光LED的驱动电路的理论功率消耗，有效保证驱动电路输出稳定的电流。

Description

一种电流型LCD背光升压方法、电路 技术领域
本发明涉及通讯领域，特别是涉及一种电流型LCD背光升压方法、电路。
背景技术
当前市面上的移动终端产品，如智能手机、平板电脑等，其液晶显示器(Liquid Crystal Display，简称为LCD)背光源通常是白光发光二极管(Light Emitting Diode，简称为LED)阵列。为了获得理想的色温和光谱，需要控制LED的驱动电流。
图1是根据相关技术的传统背光升压电路框图，如图1所示，相关技术中采用恒定电流输出的直流变换器(Direct Current/Direct Current，简称为DC/DC)来驱动LED。通过检测电流取样电阻两端的电压来监测电流，并通过误差放大器来控制DC/DC的脉冲宽度和占空比，从而实现恒定电流输出。该方案的缺点是电流取样电阻有功率回路的电流通过，因此有较大的理论功耗。例如在输出电压10V，取样电压0.5V情况下，取样电阻的功率消耗达到输出功率的5％。对于移动终端降低功耗不利。
因为通常移动终端使用单电芯的锂电池，而通常的LCD背光LED阵列需要的电压约10V(视LED数量而定)，所以传统方案是一个类似boost类DC/DC，而主要区别是误差取样方式。常规的DC/DC需要输出恒定的电压，因此误差取样自输出电压，通过分压电阻获得输出电压的比例关系；而LED背光电路需要恒定的电流来驱动，其误差取样取自电流取样电阻的电压，其电压与电流成正比例关系。
针对相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问 题，目前尚未提出有效的解决方案。
发明内容
针对相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问题，本发明提供了一种电流型LCD背光升压方法、电路，用以解决上述技术问题。
根据本发明的一个方面，本发明提供了一种电流型LCD背光升压电路，包括：LED电流控制模块、电感、二极管、开关晶体管、电容、LCD背光LED陈列；其中，
LED电流控制模块，与电感的输入端相连，设置为测量所述电感的电压，并基于该电压得到电路的负载电流值，以基于该负载电流值对电路进行调整，从而控制所述LCD背光LED陈列的驱动电流；
所述电感，其输出端与所述二极管的输入端相连，设置为控制电流和升压；
所述二极管，其输出端与所述电容的输入端相连，设置为在所述电感的感生电动势对所述电容充电时导通，在不对所述电容充电时关断；
所述开关晶体管，其输入端与所述电感的输出端相连，设置为在导通期间对所述电感进行储能；
所述电容，设置为为所述LED提供稳定电流；
所述LCD背光LED陈列，其输入端与所述电容的输入端相连，其LED的数量与LCD的屏幕尺寸相关。
优选地，所述LED电流控制模块包括：积分电路、比较器1、比较器2、模拟乘法器、误差放大器、占空比测量电路、锯齿波发生器、定时电路；其中，
所述定时电路，与所述积分电路、所述占空比测量电路、所述锯齿波发生器的一端相连，设置为定时；
所述积分电路，其另一端与所述模拟乘法器相连，设置为进行积分运算；
所述占空比测量电路，其另一端与所述比较器1相连，设置为测量所述二 极管导通期间的占空比；
所述模拟乘法器，一端与所述积分电路、所述占空比测量电路相连，另一端与所述误差放大器相连，设置为将所述二极管导通期间的平均电流与所述占空比相乘，得到所述负载电流值。
优选地，所述电感为功率电感。
优选地，所述二极管为开关二极管或场效应晶体管。
优选地，所述电容为滤波储能电容。
根据本发明的另一方面，本发明还提供了一种电流型LCD背光升压方法，其中，该方法包括：测量电流型LCD背光升压电路中电感两端的电压，对该电压进行积分得到电流值；基于所述电流值得到所述电路的负载电流值；基于所述负载电流值对电路进行调整，以控制所述电路中LCD背光LED陈列的驱动电流。
优选地，基于所述电流值得到所述电路的负载电流，包括：计算所述电路中开关晶体管导通期间的电流变化斜率；根据所述电流变化斜率，计算所述开关晶体管导通终止时，流经电感的电流峰值；将二极管导通期间的平均电流×占空比，得到所述负载电流值；其中，所述平均电流＝所述电流峰值/2。
优选地，基于所述负载电流值对电路进行调整，以控制所述电路中LCD背光LED陈列的驱动电流，包括：通过调整开关晶体管的导通周期，使得所述负载电流值达到预设期望电流值。
本发明有益效果如下：
通过本发明，解决了相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问题，有效避免LCD背光LED的驱动电路的理论功率消耗，有效保证驱动电路输出稳定的电流。
上述说明仅是本发明技术方案的概述，为了能够更清楚了解本发明的技术手段，而可依照说明书的内容予以实施，并且为了让本发明的上述和其它目的、特征和优点能够更明显易懂，以下特举本发明的具体实施方式。
附图说明
图1是根据相关技术的传统背光升压电路框图；
图2是根据本发明实施例一的电流型LCD背光升压电路的框图；
图3是根据本发明实施例二的电感的电流波形示意图；
图4是根据本发明实施例三的电流型LCD背光升压方法的流程图。
具体实施方式
为了解决相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问题，本发明提供了一种电流型LCD背光升压方法、电路，以下结合附图以及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不限定本发明。
实施例一
图2是根据本发明实施例一的电流型LCD背光升压电路的框图，如图2所示，该电路包括：LED电流控制模块、电感、二极管、开关晶体管、电容、LCD背光发光二极管LED陈列；其中，
LED电流控制模块，与电感的输入端相连，设置为测量电感的电压，并基于该电压得到电路的负载电流值，以基于该负载电流值对电路进行调整，从而控制LCD背光LED陈列的驱动电流；
电感，其输出端与二极管的输入端相连，设置为控制电流和升压；优选地，该电感可以为功率电感；
二极管，其输出端与电容的输入端相连，设置为在电感的感生电动势对电容充电时导通，在不对电容充电时关断；优选地，二极管为开关二极管或场效应晶体管；
开关晶体管，其输入端与电感的输出端相连，设置为在导通期间对电感进行储能；
电容，设置为为LED提供稳定电流；优选地，电容为滤波储能电容；
LCD背光LED陈列，其输入端与电容的输入端相连，其LED的数量与LCD的屏幕尺寸相关。
通过本实施例，解决了相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问题，有效避免LCD背光LED的驱动电路的理论功率消耗，有效保证驱动电路输出稳定的电流。
下面基于图2对LED电流控制模块进行介绍，该模块包括：积分电路、比较器1、比较器2、模拟乘法器、误差放大器、占空比测量电路、锯齿波发生器、定时电路；其中，
定时电路，与积分电路、占空比测量电路、锯齿波发生器的一端相连，设置为定时；
积分电路，其另一端与模拟乘法器相连，设置为进行积分运算；
占空比测量电路，其另一端与比较器1相连，设置为测量二极管导通期间的占空比；
模拟乘法器，一端与积分电路、占空比测量电路相连，另一端与误差放大器相连，设置为将二极管导通期间的平均电流与占空比相乘，得到负载电流值。
当然，如图2所示，上述电流型LCD背光升压电路中还包括电源、功率管驱动电路，二者的功能与传统背光升压电路中的功能相同，在此不再详细介绍。
实施例二
下面通过优选实施例对无取样电阻的电流型LCD背光升压电路进行介绍。
移动终端产品通常使用单电芯锂电池，其工作电压通常在3V～4.2V之间，而LCD的背光LED需要恒定的电流来驱动，以获得纯正的色温，此外，移动产品对功耗极其敏感，因此其驱动电路通常是能够输出稳定的电流的DC/DC电路。而传统驱动电路框图如图1，因取样电阻的存在，其理论功耗为工作电 流与取样电压的乘积。为了不用取样电阻，本发明实施例中提出了一种新的电流控制方案。
无取样电阻的电流型LCD背光升压电路包括有以下功能模块：
模块A、LED电流控制模块，包括：积分电路，2个电压比较器，模拟乘法器，误差放大器，占空比测量电路，锯齿波发生器；
模块B、电感；
模块C、开关二极管或替代器件；
模块D、开关晶体管或替代器件；
模块E、电容；
模块F、LCD背光LED阵列。
其中，模块A通过控制开关晶体管导通和截止，从而控制LED的工作电流。开关晶体管可以是双极型晶体管或场效应晶体管，也可以是其他受控电子开关。
其中，模块B是功率电感，起控制电流和升压作用。根据电感的定义公式：
Figure PCTCN2015085468-appb-000001
……①
Figure PCTCN2015085468-appb-000002
……②
其电流变化的斜率是V/L，如果每个周期的起始电流为0，那么电流是对时间的积分。因此，对电感两端的电压进行积分，可以求出电流值。
其中，模块C是开关二极管，在电感的感生电动势对储能电容充电时导通，而在不对电容充电时关断，避免电能从其他支路泻放。开关二极管也可以用场效应晶体管等同步开关电路来代替。
其中，模块D是开关晶体管，导通期间对模块B——电感进行储能，电感电流上升，截止期间电感通过二极管释放能量，从而给LED提供电流。
其中，模块E是滤波储能电容，给LED提供稳定的电流。
其中，模块F是用电负载——LCD背光LED阵列，其LED数量和LCD 屏幕尺寸等相关。
在最核心的模块A：LED电流控制模块中，通过积分器测量出在开关晶体管每个导通周期结束时的电感电流，还测量出二极管导通的占空比，并对二者相乘。LED通过的电流与乘积成正比例关系。
本发明实施例中的技术方案仍然是一个类似boost类DC/DC，与相关技术中的方案类似，主要区别在于LED电流控制模块。其积分电路对输入电压进行积分，因此与电感电流成正比例关系，如下式：
Figure PCTCN2015085468-appb-000003
……③
比较器1将二极管导通的信号转换成恒定幅度的脉冲信号，在通过一个例如积分器即可测量出占空比。比较器2将误差信号与锯齿波信号进行比较，获得控制开关晶体管的脉冲宽度信号。
在开关晶体管导通期间，其电流变化斜率为：
Figure PCTCN2015085468-appb-000004
……④
因此在开关晶体管导通终止时，流经电感的电流达到峰值，其值为：
Figure PCTCN2015085468-appb-000005
……⑤
而在二极管导通期间，电感电流变化的斜率为：
Figure PCTCN2015085468-appb-000006
……⑥
在二极管导通期间的其平均电流为：IPEAK/2。二极管导通的占空比为TLED/TALL，因此平均电流(即负载电流)为平均电流×占空比：
Figure PCTCN2015085468-appb-000007
……⑦
因此，通过选择合适的电感并设置目标电流参考，通过调整开关晶体管的导通周期，从而调整二极管导通的占空比，使得负载电流值达到预设期望电流值，可以获得需要的恒定输出电流。
图3是根据本发明实施例二的电感的电流波形示意图，如图3所示，图3中TFET是开关晶体管导通期，在此段周期中，电感中电流变化斜率为VIN/L，峰值电流为IPEAK。
TLED是二极管导通期，二极管导通期间电感对LED电路充电，其电流变化斜率为(VOUT-VIN)/L，那么这段时间的平均电流为IPEAK/2。
TOFF是开关晶体管和二极管都截止，这段时间需要大于0，以保证电感中的电流恢复到0，避免出现积累误差；
TALL是一个完整周期。包括以上三段周期，LED的电流等于二极管导通期间的平均电流乘以其导通的占空比。当开关晶体管导通期变长，峰值电流也变大，同时二极管导通周期也变长，那么LED电流变大，反之LED电流变小。
上述场景代表了本发明的典型应用，但并不仅限于此。工程技术人员可以很容易的将其扩展到其他类似场景，此处不再赘述。
实施例三
本发明实施例中还提供了一种电流型LCD背光升压方法，图4是根据本发明实施例三的电流型LCD背光升压方法的流程图，如图4所示，该方法包括以下步骤(步骤S402-步骤S406)：
步骤S402，测量电流型LCD背光升压电路中电感两端的电压，对该电压进行积分得到电流值；
步骤S404，基于电流值得到电路的负载电流值；
步骤S406，基于负载电流值对电路进行调整，以控制电路中LCD背光LED陈列的驱动电流。
通过本实施例，解决了相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问题，有效避免LCD背光LED的驱动电路的理论功率消耗，有效保证驱动电路输出稳定的电流。
在上述步骤S404中，基于电流值得到电路的负载电流，可以通过以下流程实现：计算电路中开关晶体管导通期间的电流变化斜率；根据电流变化斜率，计算开关晶体管导通终止时，流经电感的电流峰值；将二极管导通期间的平均电流×占空比，得到负载电流值；其中，平均电流＝电流峰值/2。
在上述步骤S406中，基于负载电流值对电路进行调整，以控制电路中LCD背光LED陈列的驱动电流，可以通过以下流程实现：通过调整开关晶体管的导通周期，使得负载电流值达到预设期望电流值。
从以上的描述中可知，本发明涉及一种没有电流取样电阻的恒流输出DC/DC电路，用于驱动移动终端LCD的背光LED。本发明的目的在于，在保证驱动电路输出稳定的电流的前提下，降低LCD背光LED的驱动电路自身的理论功率消耗。
尽管为示例目的，已经公开了本发明的优选实施例，本领域的技术人员将意识到各种改进、增加和取代也是可能的，因此，本发明的范围应当不限于上述实施例。
工业实用性
如上所述，本发明实施例提供的一种电流型LCD背光升压方法、电路具有以下有益效果：解决了相关技术中LCD背光LED的驱动电路自身的理论功率消耗较大的问题，有效避免LCD背光LED的驱动电路的理论功率消耗，有效保证驱动电路输出稳定的电流。

Claims (8)

  1. 一种电流型液晶显示器LCD背光升压电路，包括：LED电流控制模块、电感、二极管、开关晶体管、电容、LCD背光发光二极管LED陈列；其中，
    所述LED电流控制模块，与电感的输入端相连，用于测量所述电感的电压，并基于该电压得到电路的负载电流值，以基于该负载电流值对电路进行调整，从而控制所述LCD背光LED陈列的驱动电流；
    所述电感，其输出端与所述二极管的输入端相连，用于控制电流和升压；
    所述二极管，其输出端与所述电容的输入端相连，用于在所述电感的感生电动势对所述电容充电时导通，在不对所述电容充电时关断；
    所述开关晶体管，其输入端与所述电感的输出端相连，用于在导通期间对所述电感进行储能；
    所述电容，用于为所述LED提供稳定电流；
    所述LCD背光LED陈列，其输入端与所述电容的输入端相连，其LED的数量与LCD的屏幕尺寸相关。
  2. 如权利要求1所述的电路，其中，所述LED电流控制模块包括：积分电路、比较器1、比较器2、模拟乘法器、误差放大器、占空比测量电路、锯齿波发生器、定时电路；其中，
    所述定时电路，与所述积分电路、所述占空比测量电路、所述锯齿波发生器的一端相连，用于定时；
    所述积分电路，其另一端与所述模拟乘法器相连，用于进行积分运算；
    所述占空比测量电路，其另一端与所述比较器1相连，用于测量所述二极管导通期间的占空比；
    所述模拟乘法器，一端与所述积分电路、所述占空比测量电路相连，另一端与所述误差放大器相连，用于将所述二极管导通期间的平均电流与所述占空比相乘，得到所述负载电流值。
  3. 如权利要求1所述的电路，其中，所述电感为功率电感。
  4. 如权利要求1所述的电路，其中，所述二极管为开关二极管或场效应晶体管。
  5. 如权利要求1所述的电路，其中，所述电容为滤波储能电容。
  6. 一种电流型LCD背光升压方法，包括：
    测量电流型LCD背光升压电路中电感两端的电压，对该电压进行积分得到电流值；
    基于所述电流值得到所述电路的负载电流值；
    基于所述负载电流值对电路进行调整，以控制所述电路中LCD背光LED陈列的驱动电流。
  7. 如权利要求6所述的方法，其中，基于所述电流值得到所述电路的负载电流，包括：
    计算所述电路中开关晶体管导通期间的电流变化斜率；
    根据所述电流变化斜率，计算所述开关晶体管导通终止时，流经电感的电流峰值；
    将二极管导通期间的平均电流×占空比，得到所述负载电流值；其中，所述平均电流＝所述电流峰值/2。
  8. 如权利要求6所述的方法，其中，基于所述负载电流值对电路进行调整，以控制所述电路中LCD背光LED陈列的驱动电流，包括：
    通过调整开关晶体管的导通周期，使得所述负载电流值达到预设期望电流值。
PCT/CN2015/085468 2014-12-02 2015-07-29 一种电流型lcd背光升压方法、电路 WO2016086675A1 (zh)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN201410720126.6A CN105722283A (zh) 2014-12-02 2014-12-02 一种电流型lcd背光升压方法、电路
CN201410720126.6 2014-12-02

Publications (1)

Publication Number Publication Date
WO2016086675A1 true WO2016086675A1 (zh) 2016-06-09

Family

ID=56090950

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2015/085468 WO2016086675A1 (zh) 2014-12-02 2015-07-29 一种电流型lcd背光升压方法、电路

Country Status (2)

Country Link
CN (1) CN105722283A (zh)
WO (1) WO2016086675A1 (zh)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112688739A (zh) * 2020-12-16 2021-04-20 武汉永鼎光通科技有限公司 一种自适应背光的apc控制电路

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102932985A (zh) * 2011-08-12 2013-02-13 瑞鼎科技股份有限公司 发光二极管驱动装置
CN103400560A (zh) * 2013-08-12 2013-11-20 深圳市华星光电技术有限公司 Led背光驱动电路以及液晶显示器
CN103531147A (zh) * 2013-10-25 2014-01-22 无锡中星微电子有限公司 Led驱动电路及使用该驱动电路的led驱动系统

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN201182026Y (zh) * 2008-01-28 2009-01-14 缪复华 一种led灯组驱动电源装置
CN101657054B (zh) * 2009-02-18 2016-01-20 上海威廉照明电气有限公司 一种具有功率因数校正的供电电路的改进结构
CN201700061U (zh) * 2010-06-11 2011-01-05 卢国泰 高功率因素led电源驱动器
CN202425106U (zh) * 2011-11-28 2012-09-05 东莞市福地电子材料有限公司 一种led高压电源
US9420645B2 (en) * 2012-05-17 2016-08-16 Dialog Semiconductor Inc. Constant current control buck converter without current sense
CN203590562U (zh) * 2013-11-25 2014-05-07 上海莱托思电子科技有限公司 一种led开关恒流驱动电路

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102932985A (zh) * 2011-08-12 2013-02-13 瑞鼎科技股份有限公司 发光二极管驱动装置
CN103400560A (zh) * 2013-08-12 2013-11-20 深圳市华星光电技术有限公司 Led背光驱动电路以及液晶显示器
CN103531147A (zh) * 2013-10-25 2014-01-22 无锡中星微电子有限公司 Led驱动电路及使用该驱动电路的led驱动系统

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112688739A (zh) * 2020-12-16 2021-04-20 武汉永鼎光通科技有限公司 一种自适应背光的apc控制电路

Also Published As

Publication number Publication date
CN105722283A (zh) 2016-06-29

Similar Documents

Publication Publication Date Title
CN102238779B (zh) 开关电源的控制电路、控制方法和发光装置及电子设备
US20190089251A1 (en) Single inductor multi-output buck-boost converter and control method thereof
JP3198222U (ja) 充電器及び充電システム
TWI411202B (zh) 電源轉換器的控制器以及電源轉換器的控制方法
TWI376979B (en) Driving circuit, controller and method thereof for powering led sources
CN102769981B (zh) 一种嵌入式实现的智能恒流驱动器及其控制方法
CN106208692B (zh) 开关电路的控制方法、控制电路及开关电路装置
TW201521309A (zh) 開關電源輸出過壓保護方法及電路及具有該電路的開關電源ｌｅｄ驅動電路
JP2017521825A (ja) Ｌｅｄバックライト駆動回路及び液晶表示器
CN102132478A (zh) 具有动态阈值的磁滞降压变换器
US20140327421A1 (en) Switching regulator and method for controlling the switching regulator
CN103414357B (zh) 一种受负载电压调节的源端控制恒流输出电源的驱动电路
CN103458557A (zh) 一种led驱动控制电路及led灯具
CN104283430A (zh) 软启动切换电源转换装置
US11665794B2 (en) Dimming circuit and dimming control method
CN104159355A (zh) Led驱动电路及其控制电路以及控制方法
CN102740540A (zh) 发光二极管驱动系统
CN205160851U (zh) 二合一电源
CN202396030U (zh) Led驱动装置、电池充电器及其驱动控制电路
TWM534932U (zh) 電源供應裝置
WO2016086675A1 (zh) 一种电流型lcd背光升压方法、电路
CN103095103A (zh) 开关电源中随负载变化实现曲率降频的频率调整控制电路
US8947062B2 (en) Power supply circuit
CN105101572A (zh) 一种高功率因数led驱动集成电路
CN210429267U (zh) 一种led背光驱动电路

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15864534

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15864534

Country of ref document: EP

Kind code of ref document: A1