WO2016049946A1 - 用于液晶显示设备的led背光源及液晶显示设备 - Google Patents

用于液晶显示设备的led背光源及液晶显示设备 Download PDF

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Publication number
WO2016049946A1
WO2016049946A1 PCT/CN2014/088521 CN2014088521W WO2016049946A1 WO 2016049946 A1 WO2016049946 A1 WO 2016049946A1 CN 2014088521 W CN2014088521 W CN 2014088521W WO 2016049946 A1 WO2016049946 A1 WO 2016049946A1
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Prior art keywords
resistor
led
voltage
led string
mos transistor
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PCT/CN2014/088521
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English (en)
French (fr)
Inventor
陈辛洪
杨翔
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深圳市华星光电技术有限公司
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Application filed by 深圳市华星光电技术有限公司 filed Critical 深圳市华星光电技术有限公司
Priority to GB1702110.6A priority Critical patent/GB2543701B/en
Priority to JP2017516759A priority patent/JP6337203B2/ja
Priority to KR1020177010118A priority patent/KR101932366B1/ko
Priority to DE112014007002.5T priority patent/DE112014007002B4/de
Priority to US14/426,381 priority patent/US20160249427A1/en
Priority to RU2017109716A priority patent/RU2673703C2/ru
Publication of WO2016049946A1 publication Critical patent/WO2016049946A1/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
    • H05B45/3725—Switched mode power supply [SMPS]
    • 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
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133603—Direct backlight with LEDs
    • 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
    • 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
    • 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
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the invention belongs to the technical field of liquid crystal display, and in particular to an LED backlight and a liquid crystal display device for a liquid crystal display device.
  • CCFL cold cathode fluorescent lamp
  • LED light-emitting diode
  • the LED forward current is positively correlated with the LED turn-on voltage, that is, the larger the LED forward current, the larger the LED turn-on voltage.
  • the LED in the LED backlight may be flickered, and in the serious case, the LED driver chip may malfunction due to LED short circuit protection.
  • an object of the present invention is to provide an LED backlight for a liquid crystal display device, comprising: a boosting circuit configured to boost an input voltage to an operating voltage of an LED string; a control module configured to be coupled to the negative terminal of the LED string to regulate an operating current of the LED string; the microcontroller configured to provide a second square wave signal to the current control module to control the current control module to implement a current regulating function And finding a feedback adjustment voltage from the lookup table according to the operating current of the LED string; the boosting driving chip is configured to provide a first square wave signal to the boosting circuit to control the boosting circuit to implement the boosting function; The microcontroller finds the feedback adjustment voltage, and changes the duty ratio of the first square wave signal supplied to the boost circuit according to the received feedback adjustment voltage to change the operating voltage of the LED string.
  • Another object of the present invention is to provide a liquid crystal display device including a liquid crystal display panel and an LED backlight.
  • the LED backlight provides a display light source to the liquid crystal display panel to display the liquid crystal display panel.
  • the image, wherein the LED backlight comprises: a boosting circuit configured to boost an input voltage to an operating voltage of the LED string; and a current control module configured to be coupled to a negative end of the LED string to adjust the LED string a working current;
  • the microcontroller is configured to provide a second square wave signal to the current control module to control the current control module to implement a function of adjusting the current, and to find a feedback adjustment voltage from the lookup table according to the operating current of the LED string;
  • the boost driving chip is configured to provide a square wave signal to the boosting circuit to control the boosting circuit to implement a boosting function; receive a feedback adjustment voltage found by the microcontroller, and adjust the voltage change according to the received feedback
  • the duty cycle of the first square wave signal provided to the boost circuit to change the operating
  • the boosting circuit includes: an inductor, a first MOS transistor, and a rectifier diode, wherein one end of the inductor is used to receive the input voltage, and the other end of the inductor is connected to a positive pole of the rectifier diode, and is connected to a drain of the first MOS transistor, a cathode of the rectifier diode is connected to a positive terminal of the LED string, a gate of the first MOS transistor is connected to a square wave signal output end of the boost driver chip, and a source of the first MOS transistor is electrically grounded .
  • the current control module includes a second MOS transistor and a fourth resistor, wherein a gate of the second MOS transistor is connected to an LED operating current control terminal of the microcontroller, and a drain of the second MOS transistor is connected to the LED The negative terminal of the string, the source of the third MOS transistor is connected to one end of the fourth resistor, and the other end of the fourth resistor is electrically grounded.
  • the LED backlight further includes: a first resistor, a second resistor, and a third resistor, wherein one end of the first resistor is connected to the positive end of the LED string, and one end of the second resistor is connected to the electric sexually grounded, one end of the third resistor is connected to the feedback regulated voltage output of the microcontroller, the other end of the first resistor, the other end of the second resistor, and the other end of the third resistor are connected to the boost drive The feedback of the chip adjusts the voltage input.
  • the LED string includes a predetermined number of LEDs in series.
  • the LED backlight and the liquid crystal display device for a liquid crystal display device of the present invention can quickly change the boost because the microcontroller can quickly find the corresponding feedback adjustment voltage from the lookup table according to the operating current of the LED string.
  • the circuit provides the operating voltage to the LED string to adjust the operating current of the LED string, and can quickly adjust the operating voltage of the LED string to avoid the LED string.
  • the LED flashes, and it also avoids the malfunction of the LED short circuit protection of the microcontroller.
  • FIG. 1 is a structural view of a liquid crystal display device according to an embodiment of the present invention.
  • FIG. 2 is a block diagram of an LED backlight for a liquid crystal display device in accordance with an embodiment of the present invention
  • FIG. 3 is a circuit configuration diagram of an LED backlight for a liquid crystal display device in accordance with an embodiment of the present invention.
  • FIG. 1 is a structural diagram of a liquid crystal display device in accordance with an embodiment of the present invention.
  • a liquid crystal display device includes a liquid crystal display panel 200 and an LED backlight 100 disposed opposite to each other, wherein the LED backlight 100 provides a display light source to the liquid crystal display panel 200 to display the liquid crystal display panel 200. image.
  • LED backlight 100 according to an embodiment of the present invention will be described in detail.
  • FIG. 2 is a block diagram of an LED backlight for a liquid crystal display device according to an embodiment of the present invention
  • FIG. 3 is a circuit configuration diagram of an LED backlight for a liquid crystal display device according to an embodiment of the present invention.
  • the LED backlight includes: a boosting circuit 110, a current control module 120, a Micro Control Unit (MCU) 130, and a boost driving chip (IC). 140 and LED string 150.
  • a boosting circuit 110 a current control module 120, a Micro Control Unit (MCU) 130, and a boost driving chip (IC).
  • MCU Micro Control Unit
  • IC boost driving chip
  • the boost circuit 110 can be, for example, an inductive boost circuit for boosting the input voltage Vin to the operating voltage required for the LED string 150 to function properly.
  • the boosting circuit 110 includes an inductor 111, a first metal oxide semiconductor (MOS) transistor 112, and a rectifier diode 113.
  • MOS metal oxide semiconductor
  • one end of the inductor 111 is for receiving the input voltage Vin
  • the other end of the inductor 111 is connected to the anode of the rectifier diode 113, and is connected to the drain of the first MOS transistor 112, and the cathode of the rectifier diode 113 is connected to the LED string.
  • the gate of the first MOS transistor 112 is connected to the square wave signal output terminal DRV of the boosting driving chip 140, and the source of the first MOS transistor 112 is electrically grounded.
  • the boosting circuit of the present invention is not limited to the circuit configuration of the boosting circuit 110 shown in FIG. 3, and may be, for example, a circuit configuration of other suitable types of boosting circuits.
  • the inductor 111 is an energy conversion device capable of mutually converting electrical energy and magnetic field.
  • the inductor 111 converts the electrical energy into a magnetic field that can be stored.
  • the inductor 111 converts the stored magnetic field energy into electrical energy.
  • this electric energy is superimposed with the input voltage Vin and filtered by the rectifier diode 113 to obtain a DC voltage, which is used as an operating voltage required for the LED string 150 to operate normally, and is supplied to the LED string 150. Since this DC voltage is formed by the superposition of the input voltage Vin and the electric energy converted by the magnetic field energy of the inductor 111, the DC voltage is higher than the input voltage Vin.
  • the LED string 150 acts as a backlight for a liquid crystal display device, wherein the LED string 150 includes a predetermined number of LEDs in series.
  • the LED string 150 receives from the boost circuit 110 the operating voltage required for its normal operation.
  • the number N of LEDs in the LED string 150 (N is an integer greater than zero) is determined in the following manner:
  • Vd is the normal lighting voltage of each LED
  • Vout is the operating voltage required for the LED string 150 to receive its normal operation from the boosting circuit 110.
  • the Current control module 120 is coupled to the negative terminal of LED string 150 to regulate the operating current of LED string 150.
  • the current control module 120 includes a second MOS transistor 121 and a fourth resistor 122.
  • the gate of the second MOS transistor 121 is connected to the LED operating current control terminal LIN of the microcontroller 130, the drain of the second MOS transistor 121 is connected to the negative terminal of the LED string 150, and the source of the second MOS transistor 121 is connected.
  • To one end of the fourth resistor 122 the other end of the fourth resistor 122 is electrically grounded.
  • the gate of the third MOS transistor 121 receives the second square wave signal PWM2 provided by the LED operating current control terminal LIN of the microcontroller 130.
  • the microcontroller 130 increases or decreases the operating current level of the LED string 150 by changing the duty cycle of the second square wave signal PWM2.
  • the operating current of the LED string 150 is kept constant during normal operation of the liquid crystal display device according to an embodiment of the present invention.
  • the microcontroller 130 finds the feedback adjustment voltage from its lookup table based on the operating current of the received LED string 150.
  • the lookup table is built into the microcontroller 130.
  • the feedback regulating voltage output terminal DAC of the microcontroller 130 is connected to the feedback regulating voltage input terminal FB of the boosting driving chip 140 through the third resistor 163, and the boosting driving chip 140 adjusts the feedback received according to the feedback adjusting voltage input terminal FB thereof.
  • the voltage changes the duty ratio of the first square wave signal PWM1 supplied from the square wave signal output terminal DRV to the boosting circuit 110, thereby changing the operating voltage supplied from the boosting circuit 110 to the LED string 150.
  • one end of the first resistor 161 is connected to the positive end of the LED string 150, one end of the second resistor 162 is connected to the electrical ground, and the other end of the first resistor 161 and the other end of the second resistor 162 are connected to The feedback of the boost driver chip 140 adjusts the voltage input terminal FB.
  • the relationship between the operating voltage of the LED string 150 and the feedback adjustment voltage outputted by the feedback regulating voltage output terminal DAC of the microcontroller 130 can be expressed by the following equation (1).
  • V LED represents the operating voltage of the LED string 150
  • V DAC represents the feedback regulated voltage of the feedback regulated voltage output terminal DAC of the microcontroller 130
  • V FB represents the feedback received by the feedback regulating voltage input terminal FB of the boosting driving chip 140.
  • the voltage is adjusted, R 1 represents the resistance value of the first resistor 161, R 2 represents the resistance value of the second resistor 162, and R 3 represents the resistance value of the third resistor 163.
  • the LED string 150 Since the operating current of the LED string 150 is proportional to the operating voltage of the LED string 150, and the operating voltage of the LED string 150 is inversely proportional to the feedback regulated voltage of the feedback regulated voltage output DAC of the microcontroller 130, the LED string 150 The operating current is inversely proportional to the feedback regulated voltage of the feedback regulated voltage output DAC output of the microcontroller 130. Therefore, according to the inverse relationship, a look-up table of the operating current of the LED string 150 and the feedback adjustment voltage output by the feedback regulating voltage output terminal DAC of the microcontroller 130 can be established in the microcontroller 130, in the look-up table, an LED The current value of the operating current of the string 150 corresponds to a feedback regulated voltage output terminal DAC of the microcontroller 130. The output feedback adjusts the voltage value of the voltage.
  • the microcontroller 130 can quickly find the corresponding feedback adjustment voltage from its look-up table according to the operating current of the LED string 150, the operating voltage supplied from the boosting circuit 110 to the LED string 150 can be quickly changed. Therefore, while adjusting the operating current of the LED string 150, the operating voltage of the LED string 150 can be quickly adjusted to avoid flickering of the LEDs in the LED string 150, and also avoid the malfunction of the LED short circuit protection of the microcontroller 130. .

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  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Nonlinear Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optics & Photonics (AREA)
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Abstract

一种用于液晶显示设备的LED背光源，包括：升压电路（110），被构造为将输入电压升压至LED串（150）的工作电压；电流控制模块（120），被构造为连接到LED串（150）的负端，以调节LED串（150）的工作电流；微控制器（130），被构造为向电流控制模块（120）提供第二方波信号，以控制电流控制模块（120）实现调节电流的功能，且根据LED串（150）的工作电流从其查找表中查找出反馈调节电压；升压驱动芯片（140），被构造为向升压电路（110）提供第一方波信号，以控制升压电路（110）实现升压的功能；接收微控制器（130）查找出的反馈调节电压，且根据接收到的所述反馈调节电压改变向升压电路（110）提供的第一方波信号的占空比，以改变LED串（150）的工作电压。

Description

用于液晶显示设备的LED背光源及液晶显示设备 技术领域
本发明属于液晶显示技术领域，具体地讲，涉及一种用于液晶显示设备的LED背光源及液晶显示设备。
背景技术
随着显示技术的不断进步，液晶显示设备的背光技术不断得到发展。传统的液晶显示设备的背光源采用冷阴极荧光灯(CCFL)。但是由于CCFL背光源存在色彩还原能力较差、发光效率低、放电电压高、低温下放电特性差、加热达到稳定灰度时间长等缺点，当前已经开发出使用发光二极管(LED)背光源的背光源技术。
在现有技术的LED背光源中，LED正向电流与LED导通电压正相关，即LED正向电流越大，LED导通电压也越大。为了在LED点亮的状态下调整LED正向电流，需要同时对LED导通电压进行快速的调整。然而，由于现有技术中的这种调整速度较慢，所以会导致LED背光源中的LED出现闪烁现象，严重时会使LED驱动芯片出现LED短路保护的误动作。
发明内容
为了解决上述现有技术存在的问题，本发明的目的在于提供一种用于液晶显示设备的LED背光源，包括：升压电路，被构造为将输入电压升压至LED串的工作电压；电流控制模块，被构造为连接到LED串的负端，以调节LED串的工作电流；微控制器，被构造为向电流控制模块提供第二方波信号，以控制电流控制模块实现调节电流的功能，且根据LED串的工作电流从其查找表中查找出反馈调节电压；升压驱动芯片，被构造为向升压电路提供第一方波信号，以控制升压电路实现升压的功能；接收微控制器查找出的反馈调节电压，且根据接收到的所述反馈调节电压改变向升压电路提供的第一方波信号的占空比，以改变LED串的工作电压。
本发明的另一目的还在于提供一种液晶显示设备，包括相对设置的液晶显示面板及LED背光源，所述LED背光源提供显示光源给所述液晶显示面板，以使所述液晶显示面板显示影像，其中，所述LED背光源包括：升压电路，被构造为将输入电压升压至LED串的工作电压；电流控制模块，被构造为连接到LED串的负端，以调节LED串的工作电流；微控制器，被构造为向电流控制模块提供第二方波信号，以控制电流控制模块实现调节电流的功能，且根据LED串的工作电流从其查找表中查找出反馈调节电压；升压驱动芯片，被构造为向升压电路提供一方波信号，以控制升压电路实现升压的功能；接收微控制器查找出的反馈调节电压，且根据接收到的所述反馈调节电压改变向升压电路提供的第一方波信号的占空比，以改变LED串的工作电压。
进一步地，所述升压电路包括：电感器、第一MOS晶体管、整流二极管，其中，电感器的一端用于接收所述输入电压，电感器的另一端连接至整流二极管的正极，并连接至第一MOS晶体管的漏极，整流二极管的负极连接至LED串的正端，第一MOS晶体管的栅极连接至升压驱动芯片的方波信号输出端，第一MOS晶体管的源极电性接地。
进一步地，所述电流控制模块包括第二MOS晶体管及第四电阻器，其中，第二MOS晶体管的栅极连接至微控制器的LED工作电流控制端，第二MOS晶体管的漏极连接至LED串的负端，第三MOS晶体管的源极连接至第四电阻器的一端，第四电阻器的另一端电性接地。
进一步地，所述LED背光源还包括：第一电阻器、第二电阻器及第三电阻器，其中，第一电阻器的一端连接至LED串的正端，第二电阻器的一端连接电性接地，第三电阻器的一端连接至微控制器的反馈调节电压输出端，第一电阻器的另一端、第二电阻器的另一端以及第三电阻器的另一端均连接至升压驱动芯片的反馈调节电压输入端。
进一步地，所述LED串包括串联的预定数量的LED。
本发明的用于液晶显示设备的LED背光源及液晶显示设备，由于微控制器可根据LED串的工作电流从其查找表中快速地查找到对应的反馈调节电压，所以能够快速的改变升压电路提供至LED串的工作电压，从而调整LED串的工作电流的同时，能够对LED串的工作电压进行快速的调整，避免LED串中 的LED出现闪烁现象，同时也避免微控制器出现LED短路保护的误动作。
附图说明
通过结合附图进行的以下描述，本发明的实施例的上述和其它方面、特点和优点将变得更加清楚，附图中：
图1是根据本发明的实施例的液晶显示设备的结构图；
图2是根据本发明的实施例的用于液晶显示设备的LED背光源的模块图；
图3是根据本发明的实施例的用于液晶显示设备的LED背光源的电路结构图。
具体实施方式
以下，将参照附图来详细描述本发明的实施例。然而，可以以许多不同的形式来实施本发明，并且本发明不应该被解释为限制于这里阐述的具体实施例。相反，提供这些实施例是为了解释本发明的原理及其实际应用，从而使本领域的其他技术人员能够理解本发明的各种实施例和适合于特定预期应用的各种修改。
图1是根据本发明的实施例的液晶显示设备的结构图。
参照图1，根据本发明的实施例的液晶显示设备包括相对设置的液晶显示面板200以及LED背光源100，其中，LED背光源100提供显示光源给液晶显示面板200，以使液晶显示面板200显示影像。
以下，将对根据本发明的实施例的LED背光源100进行详细描述。
图2是根据本发明的实施例的用于液晶显示设备的LED背光源的模块图；图3是根据本发明的实施例的用于液晶显示设备的LED背光源的电路结构图。
参照图2和图3，根据本发明的第一实施例的LED背光源包括：升压电路110、电流控制模块120、微控制器(Micro Control Unit，简称MCU)130、升压驱动芯片(IC)140和LED串150。
具体而言，升压电路110可例如为电感型升压电路，其用于将输入电压Vin升压至LED串150正常工作所需的工作电压。升压电路110包括：电感器111、第一金属氧化物半导体(MOS)晶体管112、整流二极管113。在本实施 例中，电感器111的一端用于接收输入电压Vin，电感器111的另一端连接至整流二极管113的正极，并连接至第一MOS晶体管112的漏极，整流二极管113的负极连接至LED串150的正端，第一MOS晶体管112的栅极连接至升压驱动芯片140的方波信号输出端DRV，第一MOS晶体管112的源极电性接地。应当理解的是，本发明的升压电路不局限于图3所示的升压电路110的电路结构，其可例如是其他合适类型的升压电路的电路结构。
在升压电路110中，电感器111为电能和磁场能相互转换的能量转换器件，当第一MOS晶体管112的栅极接收到升压驱动芯片140的方波信号输出端DRV提供的第一方波信号PWM1中的高电平信号后，电感器111将电能转换为磁场能存储起来。当第一MOS晶体管112的栅极接收到升压驱动芯片140的方波信号输出端DRV提供的第一方波信号PWM1中的低电平信号后，电感器111将存储的磁场能转化成电能，且这个电能与输入电压Vin叠加后通过整流二极管113的滤波得到直流电压，该直流电压作为LED串150正常工作所需的工作电压，并提供给LED串150。由于这个直流电压是由输入电压Vin和电感器111的磁场能转换成的电能叠加形成的，所以该直流电压要高于输入电压Vin。
LED串150作为液晶显示设备的背光源，其中，LED串150包括串联的预定数量的LED。LED串150从升压电路110接收其正常工作所需的工作电压。LED串150中的LED的数量N(N为大于零的整数)以如下方式被确定：
N×Vd≤Vout，
其中，Vd为每个LED的正常发光电压，Vout为LED串150从升压电路110接收其正常工作所需的工作电压。
例如，当Vd为6.5V，Vout＝48V时，N≤7。
电流控制模块120连接到LED串150的负端，以调节LED串150的工作电流。电流控制模块120包括：第二MOS晶体管121及第四电阻器122。其中，第二MOS晶体管121的栅极连接至微控制器130的LED工作电流控制端LIN，第二MOS晶体管121的漏极连接至LED串150的负端，第二MOS晶体管121的源极连接至第四电阻器122的一端，第四电阻器122的另一端电性接地。
第三MOS晶体管121的栅极接收由微控制器130的LED工作电流控制端LIN提供的第二方波信号PWM2。微控制器130通过改变第二方波信号PWM2的占空比，以增大或减小LED串150的工作电流大小。通常，根据本发明的实施例的液晶显示设备在正常工作时，LED串150的工作电流保持恒定。微控制器130根据接收到的LED串150的工作电流从其查找表中查找出反馈调节电压。这里，该查找表建立于微控制器130中。微控制器130的反馈调节电压输出端DAC通过第三电阻器163连接至升压驱动芯片140的反馈调节电压输入端FB，升压驱动芯片140根据其反馈调节电压输入端FB接收到的反馈调节电压，改变其方波信号输出端DRV向升压电路110提供的第一方波信号PWM1的占空比，从而改变升压电路110提供至LED串150的工作电压。
此外，第一电阻器161的一端连接至LED串150的正端，第二电阻器162的一端连接电性接地，第一电阻器161的另一端以及第二电阻器162的另一端均连接至升压驱动芯片140的反馈调节电压输入端FB。
以下，将对LED串150的工作电流与微控制器130的反馈调节电压输出端DAC输出的反馈调节电压的关系进行详细说明。
在本实施例，LED串150的工作电压与微控制器130的反馈调节电压输出端DAC输出的反馈调节电压的关系可由下面的式子(1)表示。
[式子1]
Figure PCTCN2014088521-appb-000001
其中，VLED表示LED串150的工作电压，VDAC表示微控制器130的反馈调节电压输出端DAC输出的反馈调节电压，VFB表示升压驱动芯片140的反馈调节电压输入端FB接收的反馈调节电压，R1表示第一电阻器161的电阻值，R2表示第二电阻器162的电阻值，R3表示第三电阻器163的电阻值。
由于LED串150的工作电流与LED串150的工作电压成正比，而LED串150的工作电压与微控制器130的反馈调节电压输出端DAC输出的反馈调节电压成反比关系，所以LED串150的工作电流与微控制器130的反馈调节电压输出端DAC输出的反馈调节电压成反比关系。因此，根据该反比关系，可在微控制器130中建立LED串150的工作电流与微控制器130的反馈调节电压输出端DAC输出的反馈调节电压的查找表，在该查找表中，一个LED串150的工作电流的电流值对应一个微控制器130的反馈调节电压输出端DAC 输出的反馈调节电压的电压值。
综上所述，由于微控制器130可根据LED串150的工作电流从其查找表中快速地查找到对应的反馈调节电压，所以能够快速的改变升压电路110提供至LED串150的工作电压，从而调整LED串150的工作电流的同时，能够对LED串150的工作电压进行快速的调整，避免LED串150中的LED出现闪烁现象，同时也避免微控制器130出现LED短路保护的误动作。
虽然已经参照特定实施例示出并描述了本发明，但是本领域的技术人员将理解：在不脱离由权利要求及其等同物限定的本发明的精神和范围的情况下，可在此进行形式和细节上的各种变化。

Claims (10)

  1. 一种用于液晶显示设备的LED背光源，其中，包括：
    升压电路，被构造为将输入电压升压至LED串的工作电压；
    电流控制模块，被构造为连接到LED串的负端，以调节LED串的工作电流；
    微控制器，被构造为向电流控制模块提供第二方波信号，以控制电流控制模块实现调节电流的功能，且根据LED串的工作电流从其查找表中查找出反馈调节电压；
    升压驱动芯片，被构造为向升压电路提供第一方波信号，以控制升压电路实现升压的功能；接收微控制器查找出的反馈调节电压，且根据接收到的所述反馈调节电压改变向升压电路提供的第一方波信号的占空比，以改变LED串的工作电压。
  2. 根据权利要求1所述的LED背光源，其中，所述升压电路包括：电感器、第一MOS晶体管、整流二极管，
    其中，电感器的一端用于接收所述输入电压，电感器的另一端连接至整流二极管的正极，并连接至第一MOS晶体管的漏极，整流二极管的负极连接至LED串的正端，第一MOS晶体管的栅极连接至升压驱动芯片的方波信号输出端，第一MOS晶体管的源极电性接地。
  3. 根据权利要求1所述的LED背光源，其中，所述电流控制模块包括第二MOS晶体管及第四电阻器，
    其中，第二MOS晶体管的栅极连接至微控制器的LED工作电流控制端，第二MOS晶体管的漏极连接至LED串的负端，第三MOS晶体管的源极连接至第四电阻器的一端，第四电阻器的另一端电性接地。
  4. 根据权利要求1所述的LED背光源，其中，所述LED背光源还包括：第一电阻器、第二电阻器及第三电阻器，
    其中，第一电阻器的一端连接至LED串的正端，第二电阻器的一端连接电性接地，第三电阻器的一端连接至微控制器的反馈调节电压输出端，第一电阻器的另一端、第二电阻器的另一端以及第三电阻器的另一端均连接至升压驱动芯片的反馈调节电压输入端。
  5. 根据权利要求1所述的LED背光源，其中，所述LED串包括串联的预定数量的LED。
  6. 一种液晶显示设备，包括相对设置的液晶显示面板及LED背光源，其中，所述LED背光源提供显示光源给所述液晶显示面板，以使所述液晶显示面板显示影像，其中，所述LED背光源包括：
    升压电路，被构造为将输入电压升压至LED串的工作电压；
    电流控制模块，被构造为连接到LED串的负端，以调节LED串的工作电流；
    微控制器，被构造为向电流控制模块提供第二方波信号，以控制电流控制模块实现调节电流的功能，且根据LED串的工作电流从其查找表中查找出反馈调节电压；
    升压驱动芯片，被构造为向升压电路提供第一方波信号，以控制升压电路实现升压的功能；接收微控制器查找出的反馈调节电压，且根据接收到的所述反馈调节电压改变向升压电路提供的第一方波信号的占空比，以改变LED串的工作电压。
  7. 根据权利要求6所述的液晶显示设备，其中，所述升压电路包括：电感器、第一MOS晶体管、整流二极管，
    其中，电感器的一端用于接收所述输入电压，电感器的另一端连接至整流二极管的正极，并连接至第一MOS晶体管的漏极，整流二极管的负极连接至LED串的正端，第一MOS晶体管的栅极连接至升压驱动芯片的方波信号输出端，第一MOS晶体管的源极电性接地。
  8. 根据权利要求6所述的液晶显示设备，其中，所述电流控制模块包括第二MOS晶体管及第四电阻器，
    其中，第二MOS晶体管的栅极连接至微控制器的LED工作电流控制端，第二MOS晶体管的漏极连接至LED串的负端，第三MOS晶体管的源极连接至第四电阻器的一端，第四电阻器的另一端电性接地。
  9. 根据权利要求6所述的液晶显示设备，其中，所述LED背光源还包括：第一电阻器、第二电阻器及第三电阻器，
    其中，第一电阻器的一端连接至LED串的正端，第二电阻器的一端连接电性接地，第三电阻器的一端连接至微控制器的反馈调节电压输出端，第一电阻器的另一端、第二电阻器的另一端以及第三电阻器的另一端均连接至升压驱动芯片的反馈调节电压输入端。
  10. 根据权利要求6所述的液晶显示设备，其中，所述LED串包括串联的预定数量的LED。
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CN104240651B (zh) 2016-10-19
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