WO2016029512A1 - 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
WO2016029512A1
WO2016029512A1 PCT/CN2014/086315 CN2014086315W WO2016029512A1 WO 2016029512 A1 WO2016029512 A1 WO 2016029512A1 CN 2014086315 W CN2014086315 W CN 2014086315W WO 2016029512 A1 WO2016029512 A1 WO 2016029512A1
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Prior art keywords
resistor
voltage
mos transistor
circuit
backlight
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PCT/CN2014/086315
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English (en)
French (fr)
Inventor
张华�
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深圳市华星光电技术有限公司
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Priority to US14/395,062 priority Critical patent/US9433044B2/en
Priority to JP2017510489A priority patent/JP6375444B2/ja
Priority to KR1020177007697A priority patent/KR101932364B1/ko
Priority to RU2017105754A priority patent/RU2669061C2/ru
Priority to GB1700580.2A priority patent/GB2542533B/en
Publication of WO2016029512A1 publication Critical patent/WO2016029512A1/zh

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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • 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
    • 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]
    • H05B45/20—Controlling the colour 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]
    • H05B45/30—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]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/38—Switched mode power supply [SMPS] using boost topology
    • 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
    • H05B45/48—Details of LED load circuits with an active control inside an LED matrix having LEDs organised in strings and incorporating parallel shunting devices
    • 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]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective 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
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/20—Responsive to malfunctions or to light source life; for protection
    • H05B47/25—Circuit arrangements for protecting against overcurrent
    • 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
    • G02F1/133612—Electrical details
    • 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
    • G02F1/133615—Edge-illuminating devices, i.e. illuminating from the side
    • 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
    • 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
    • G09G2330/025—Reduction of instantaneous peaks of current
    • 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 backlights Due to their disadvantages such as poor color reproduction capability, low luminous efficiency, high discharge voltage, poor discharge characteristics at low temperatures, and long stable gradation time.
  • the LED backlight includes a booster circuit, a backlight drive control circuit, and an LED string.
  • the boosting circuit includes an inductor L, a rectifier diode D1, a first MOS transistor Q1, a capacitor C, and a first resistor R1, wherein one end of the inductor L receives the input DC voltage Vin, and the other end of the inductor L Connected to the positive terminal of the rectifier diode D1 and connected to the drain of the first MOS transistor Q1, the gate of the first MOS transistor Q1 is driven by the first square wave signal PWM1 provided by the backlight drive control circuit, the source of the first MOS transistor Q1
  • the pole is electrically connected to the ground through the first resistor R1; the negative terminal of the rectifier diode D1 obtains the output voltage Vout and is supplied to the LED string, and the negative terminal of the rectifier diode D1 is also electrically connected to the ground through the
  • the second MOS transistor Q2 is connected to the cathode of the LED string, wherein the drain of the second MOS transistor Q2 is connected to the cathode of the LED string, and the source of the second MOS transistor Q2 is electrically connected to the ground through the third resistor R3.
  • the gate of the second MOS transistor Q2 is driven by the second square wave signal PWM2 provided by the backlight driving control circuit. By changing the duty ratio of the second square wave signal PWM2, the operating current of the LED string can be increased or decreased.
  • the backlight driving control circuit is further connected with a second resistor R2 for determining the driving frequency of the first square wave signal PWM1 supplied to the gate of the first MOS transistor Q1.
  • the first square wave signal PWM1 supplied to the gate of the first MOS transistor Q1 accounts for
  • the space ratio D is increased by the adjustment of the backlight driving control circuit, resulting in an increase in the energy storage time D ⁇ T of the inductor L during the duty cycle T of the first square wave signal PWM1, and the maximum current on the inductor L is significantly increased.
  • the input current Iin of the LED backlight also becomes large, resulting in an instantaneous generation of a surge of input current pulses, which cause an impact on the circuit components of the LED backlight, causing damage.
  • an LED backlight for a liquid crystal display device comprising: a booster circuit configured to boost an input voltage to a work required for operation of the LED string a voltage control module configured to be coupled to a negative end of the LED string to adjust an operating current of the LED string; a voltage detection circuit configured to detect whether the input voltage is reduced; Providing a control signal to the backlight driving control circuit when the input voltage is reduced; the backlight driving control circuit is configured to provide a first square wave signal to the boosting circuit to control the boosting circuit to implement the rising a function of pressing; providing a second square wave signal to the current control module to control the current control module to implement a function of adjusting current; and receiving a control signal provided by the voltage detecting circuit, reducing the input current .
  • the voltage detecting circuit includes: a voltage dividing circuit configured to divide the input voltage to generate a comparison voltage; and a comparator configured to compare the comparison voltage and the reference voltage; An adjustment circuit configured to control an increase in a frequency of the first square wave signal provided by the backlight drive control circuit to the boost circuit when the contrast voltage is less than the reference voltage, thereby causing the input The current is reduced.
  • the voltage dividing circuit includes a first resistor and a second resistor, wherein one end of the first resistor is for receiving the input voltage, and the other end of the first resistor is connected to one end of the second resistor And connected to the negative input of the comparator, the other end of the second resistor is electrically grounded.
  • the frequency adjustment circuit includes: a second MOS transistor, a third resistor, and a fourth resistor, wherein a gate of the second MOS transistor is connected to an output of the comparator, and a drain of the second MOS transistor a pole connected to one end of the third resistor and connected to the backlight driving control
  • the source of the second MOS transistor is connected to one end of the fourth resistor, and the other end of the third resistor is electrically grounded to the other end of the fourth resistor.
  • the voltage detecting circuit includes: a voltage dividing circuit configured to divide the input voltage to generate a comparison voltage; and a micro control unit configured to detect whether the comparison voltage is reduced; And detecting that the contrast voltage is reduced, controlling a duty ratio of the second square wave signal provided by the backlight driving control circuit to the current control module to decrease, thereby reducing an operating current of the LED string Small, which in turn reduces the input current.
  • the voltage dividing circuit includes a first resistor and a second resistor, wherein one end of the first resistor is for receiving the input voltage, and the other end of the first resistor is connected to one end of the second resistor And connected to the micro control unit, the other end of the second resistor is electrically grounded.
  • the boosting circuit includes: an inductor, a first MOS transistor, a rectifier diode, and a capacitor, 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 Connected to the drain of the first MOS transistor, the negative terminal of the rectifier diode is connected to the positive terminal of the LED string, and is connected to one end of the capacitor, the gate of the first MOS transistor is connected to the backlight driving control circuit, the first MOS The source of the transistor and the other end of the capacitor are electrically grounded.
  • the current control module includes a third MOS transistor and a fifth resistor, wherein a gate of the third MOS transistor is connected to the backlight driving control circuit, and a drain of the third MOS transistor is connected to the LED string The negative terminal, the source of the third MOS transistor is connected to one end of the fifth resistor, and the other end of the fifth resistor is electrically grounded.
  • the LED string includes a predetermined number of LEDs in series.
  • Another object of the present invention is to provide a liquid crystal display device including a liquid crystal display panel and a backlight module, wherein the backlight module provides a display light source to the liquid crystal display panel to enable the liquid crystal display
  • the panel displays an image, wherein the backlight module includes the LED backlight described above.
  • the LED backlight and liquid crystal display device for liquid crystal display device of the invention can reduce the input current when the liquid crystal display device is powered off, thereby avoiding the surge of input current pulse. Impact on circuit components, causing damage.
  • FIG. 1 is a circuit diagram of a conventional LED backlight for a liquid crystal display device
  • FIG. 2 is a block diagram of an LED backlight for a liquid crystal display device in accordance with a first embodiment of the present invention
  • FIG. 3 is a circuit configuration diagram of an LED backlight for a liquid crystal display device according to a first embodiment of the present invention
  • FIG. 4 is a block diagram of an LED backlight for a liquid crystal display device in accordance with a second embodiment of the present invention.
  • FIG. 5 is a circuit configuration diagram of an LED backlight for a liquid crystal display device according to a second embodiment of the present invention.
  • FIG. 6 is a structural diagram 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 according to a first embodiment of the present invention
  • FIG. 3 is a circuit configuration diagram of an LED backlight for a liquid crystal display device according to a first embodiment of the present invention
  • the LED backlight includes a boosting circuit 110, a current control module 120, a voltage detecting circuit 130, a backlight driving control circuit 140, and an LED string 150.
  • 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 metal oxide semiconductor (MOS) transistor 112, a rectifier diode 113, and a capacitor 114.
  • MOS metal oxide semiconductor
  • one end of the inductor 111 is for receiving the input voltage
  • 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.
  • the boosting circuit of the present invention is not limited to the circuit configuration of the boosting circuit 110 shown in FIG.
  • the inductor 111 is an energy conversion device capable of mutually converting electrical energy and magnetic fields, and the gate of the first MOS transistor 112 receives the high voltage in the first square wave signal PWM1 provided by the backlight driving control circuit 140. After the signal is flat, 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, and the electric energy and the input voltage
  • the Vin is superimposed and filtered by the rectifier diode 113 and the capacitor 114 to obtain a DC voltage, which is used as the 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
  • Vs 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 third MOS transistor 121 and a fifth resistor 122.
  • the gate of the third MOS transistor 121 is connected to the backlight driving control circuit 140, the drain of the third MOS transistor 121 is connected to the negative terminal of the LED string 150, and the source of the third MOS transistor 121 is connected to the fifth resistor.
  • One end of the device 122 and the other end of the fifth resistor 122 are electrically grounded.
  • the gate of the third MOS transistor 121 receives the second square wave signal PWM2 supplied from the backlight drive control circuit 140.
  • the backlight drive control circuit 140 increases or decreases the operating current level of the LED string 150 by changing the duty ratio of the second square wave signal PWM2.
  • the operating current of the LED string 150 is kept constant during normal operation.
  • the voltage detecting circuit 130 is configured to detect whether the input voltage Vin is decreased (for example, when the liquid crystal display device is powered off, the input voltage Vin to the LED backlight is gradually decreased until 0), and the input voltage Vin is detected to be reduced. In the small case, a control signal is supplied to the backlight drive control circuit 140.
  • the voltage detecting circuit 130 includes a voltage dividing circuit 131, a comparator 132, and a frequency adjusting circuit 133.
  • the voltage dividing circuit 131 is for dividing the input voltage Vin to generate a contrast voltage Vc.
  • the voltage dividing circuit 131 includes a first resistor 1311 and a second resistor 1312, wherein one end of the first resistor 1311 is for receiving the input voltage Vin, and the other end of the first resistor 1311 is connected to one end of the second resistor 1312. And connected to the negative input terminal of the comparator 132, the other end of the second resistor 1312 is electrically grounded.
  • the comparator 132 is configured to compare the comparison voltage Vc and the reference voltage Vref.
  • the negative input terminal of the comparator 132 is connected to the other end of the first resistor 1311, the positive input terminal of the comparator 132 is for receiving the reference voltage Vref, and the output terminal of the comparator 132 is connected to the second MOS transistor 1331 of the frequency adjustment circuit 133.
  • the gate It should be noted that the reference voltage Vref is equal to the comparison voltage Vc when the liquid crystal display device according to the embodiment of the present invention operates normally.
  • the frequency adjustment circuit 133 is configured to control the frequency of the first square wave signal PWM1 supplied to the gate of the first MOS transistor 112 of the boosting circuit 110 by the backlight driving control circuit 140 when the comparison voltage Vc is smaller than the reference voltage Vref. , thereby reducing the input current Iin.
  • the frequency adjustment circuit 133 includes a second MOS transistor 1331, a third resistor 1332, and a fourth resistor 1333, wherein a gate of the second MOS transistor 1331 is connected to an output terminal of the comparator 132, and a second MOS transistor 1331 The drain is connected to one end of the third resistor 1332 and is connected to the backlight driving control circuit 140, the source of the second MOS transistor 1331 is connected to one end of the fourth resistor 1333, and the other end of the third resistor 1332 The other end of the fourth resistor 1333 is electrically grounded.
  • How to increase the frequency of the first square wave signal PWM1 that controls the backlight driving control circuit 140 to the gate of the first MOS transistor 112 of the boosting circuit 110 is increased in detail, thereby reducing the input current Iin.
  • the input voltage Vin is stable or constant
  • the resistance value, R2 represents the resistance value of the second resistor 1312.
  • the frequency of the first square wave signal PWM1 supplied from the backlight driving control circuit 140 to the gate of the first MOS transistor 112 of the boosting circuit 110 is inversely proportional to the resistance value R3 of the third resistor 1332 when the gate of the second MOS transistor 1331 When the pole receives the low level signal, so that the second MOS transistor 1331 is turned off, the resistance value R3 of the third resistor 1332 does not change, the frequency of the first square wave signal PWM1 does not change, and the input current Iin remains unchanged.
  • the output of the comparator 132 outputs a high voltage.
  • the gate of the second MOS transistor 1331 receives a high level signal, so that the second MOS transistor 1331 is turned on.
  • the third resistor 1332 is connected in parallel with the fourth resistor 1333, and the frequency of the first square wave signal PWM1 is the third.
  • the resistor 1332 is inversely proportional to the resistance value R3 ⁇ R4/(R3+R4) in parallel with the fourth resistor 1333, wherein R4 represents the resistance value of the fourth resistor 1333. Since the resistance value R3 ⁇ R4 / (R3 + R4) is larger than the resistance value R3, the frequency of the first square wave signal PWM1 becomes large, and in other words, the period T of the first counter-attack signal PWM1 decreases.
  • the energy storage time D ⁇ T of the inductor 111 during the duty cycle T of the first square wave signal PWM1 decreases, the maximum current on the inductor 111 decreases significantly, and the input current Iin also decreases, thereby avoiding a surge of input. Current pulses can cause damage to circuit components and cause damage.
  • FIG. 4 is a block diagram of an LED backlight for a liquid crystal display device according to a second embodiment of the present invention
  • FIG. 5 is a circuit configuration diagram of an LED backlight for a liquid crystal display device according to a second embodiment of the present invention.
  • the LED backlight according to the second embodiment of the present invention includes a boosting circuit 110, a current control module 120, a voltage detecting circuit 130, a backlight driving control circuit 140, and an LED string 150.
  • 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 metal oxide semiconductor (MOS) transistor 112, a rectifier diode 113, and a capacitor 114.
  • MOS metal oxide semiconductor
  • one end of the inductor 111 is for receiving the input voltage
  • 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.
  • the boosting circuit of the present invention is not limited to the circuit configuration of the boosting circuit 110 shown in FIG.
  • the inductor 111 is an energy conversion device capable of mutually converting electrical energy and magnetic fields, and the gate of the first MOS transistor 112 receives the high voltage in the first square wave signal PWM1 provided by the backlight driving control circuit 140. After the signal is flat, 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, and the electric energy and the input voltage
  • the Vin is superimposed and filtered by the rectifier diode 113 and the capacitor 114 to obtain a DC voltage, which is used as the 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
  • Vs 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 third MOS transistor 121 and a fifth resistor 122.
  • the gate of the third MOS transistor 121 is connected to the backlight driving control circuit 140, the drain of the third MOS transistor 121 is connected to the negative terminal of the LED string 150, and the source of the third MOS transistor 121 is connected to the fifth resistor.
  • One end of the device 122 and the other end of the fifth resistor 122 are electrically grounded.
  • the gate of the third MOS transistor 121 receives the second square wave signal PWM2 supplied from the backlight drive control circuit 140.
  • the backlight driving control circuit 140 changes the duty of the second square wave signal PWM2 To increase or decrease the operating current of the LED string 150.
  • the operating current of the LED string 150 is kept constant during normal operation.
  • the voltage detecting circuit 130 is configured to detect whether the input voltage Vin is decreased (for example, when the liquid crystal display device is powered off, the input voltage Vin to the LED backlight is gradually decreased until 0), and the input voltage Vin is detected to be reduced. In the small case, a control signal is supplied to the backlight drive control circuit 140.
  • the voltage detecting circuit 130 includes a voltage dividing circuit 131 and a micro control unit (MCU) 134.
  • MCU micro control unit
  • the voltage dividing circuit 131 is for dividing the input voltage Vin to generate a contrast voltage Vc.
  • the voltage dividing circuit 131 includes a first resistor 1311 and a second resistor 1312, wherein one end of the first resistor 1311 is for receiving the input voltage Vin, and the other end of the first resistor 1311 is connected to one end of the second resistor 1312. And connected to the micro control unit 134, the other end of the second resistor 1312 is electrically grounded.
  • the micro control unit 134 is configured to detect whether the contrast voltage Vc is decreased.
  • the micro control unit 134 controls the duty ratio of the second square wave signal PWM2 supplied from the backlight driving control circuit 140 to the current control module 120 to decrease the contrast voltage Vc, thereby causing the operation of the LED string 150.
  • the current is reduced, which in turn reduces the input current Iin.
  • the resistance value, R2 represents the resistance value of the second resistor 1312.
  • the micro control unit 134 controls the duty ratio of the second square wave signal PWM2 supplied from the backlight driving control circuit 140 to the current control module 120 to be constant, the operating current of the LED string 150 is constant, and the input current Iin remains unchanged.
  • the micro control unit 134 controls the duty ratio of the second square wave signal PWM2 supplied from the backlight driving control circuit 140 to the current control module 120 to decrease, the operating current of the LED string 150 decreases, and the input current Iin also decreases. Therefore, the surge of input current pulses is prevented from causing an impact on the circuit components and causing damage.
  • FIG. 6 is a structural diagram of a liquid crystal display device according to an embodiment of the present invention.
  • a liquid crystal display device includes a liquid crystal display that is disposed oppositely The panel 200 and the backlight module 100, wherein the backlight module 100 provides a display light source to the liquid crystal display panel 200 to cause the liquid crystal display panel 200 to display images.
  • the backlight module 100 is the first embodiment or the second embodiment described above. LED backlight.

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Abstract

一种用于液晶显示设备的LED背光源以及具有该LED背光源的液晶显示设备，包括：升压电路（110），被构造为将输入电压（Vin）升压至LED串（150）工作所需的工作电压；电流控制模块（120），被构造为连接到所述LED串（150）的负端，以调节所述LED串（150）的工作电流；电压侦测电路（130），被构造为侦测所述输入电压（Vin）是否减小；在侦测到所述输入电压（Vin）减小的情况下，提供控制信号给背光驱动控制电路（140）；背光驱动控制电路（140），被构造为向所述升压电路（110）提供第一方波信号（PWM1），以控制所述升压电路（110）实现升压的功能；向所述电流控制模块（120）提供第二方波信号（PWM2），以控制所述电流控制模块（120）实现调节电流的功能；在接收到电压侦测电路（130）提供的控制信号的情况下，控制输入电流减小（Iin）。

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LED背光源的背光源技术。
图1是现有的一种用于液晶显示设备的LED背光源的电路图。如图1所示，该LED背光源包括升压电路、背光驱动控制电路以及LED串。该升压电路包括电感器L、整流二极管D1、第一MOS晶体管Q1、电容器C和第一电阻器R1，其中，电感器L的一端接收所述输入的直流电压Vin，电感器L的另一端连接到整流二极管D1的正端并连接到第一MOS晶体管Q1的漏极，第一MOS晶体管Q1的栅极由背光驱动控制电路提供的第一方波信号PWM1驱动，第一MOS晶体管Q1的源极通过第一电阻器R1与地电性连接；整流二极管D1的负端获得输出电压Vout提供给LED串，整流二极管D1的负端还通过电容器C与地电性连接。LED串的负极还连接有第二MOS晶体管Q2，其中，第二MOS晶体管Q2的漏极连接到LED串的负极，第二MOS晶体管Q2的源极通过第三电阻器R3与地电性连接，第二MOS晶体管Q2的栅极由背光驱动控制电路提供的第二方波信号PWM2驱动，通过改变第二方波信号PWM2的占空比，可以增大或减小LED串的工作电流。此外，在该LED背光源中，背光驱动控制电路还连接有第二电阻器R2，用于确定提供给第一MOS晶体管Q1的栅极的第一方波信号PWM1的驱动频率。
当该LED背光源的输入的直流电压Vin减小直至0(例如液晶显示设备断电瞬间)时，由于输入电容的存在，以及背光驱动控制电路的供电范围较大的 原因，整个LED背光源不会立即停止工作，而是会继续工作在恒定功率一段时间。然而，在此段时间内，由于输出至LED串上的输出电压Vout不变，而输入的直流电压Vin减小，所以提供至第一MOS晶体管Q1的栅极的第一方波信号PWM1的占空比D会受背光驱动控制电路的调节而变大，导致电感器L在第一方波信号PWM1的工作周期T内的储能时间D×T增加，电感器L上的最大电流显著增大，该LED背光源的输入电流Iin也会变大，导致瞬间产生一激增的输入电流脉冲，对该LED背光源的电路元器件产生冲击，造成损伤。
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串工作所需的工作电压；电流控制模块，被构造为连接到所述LED串的负端，以调节所述LED串的工作电流；电压侦测电路，被构造为侦测所述输入电压是否减小；在侦测到所述输入电压减小的情况下，提供控制信号给背光驱动控制电路；背光驱动控制电路，被构造为向所述升压电路提供第一方波信号，以控制所述升压电路实现升压的功能；向所述电流控制模块提供第二方波信号，以控制所述电流控制模块实现调节电流的功能；在接收到电压侦测电路提供的控制信号的情况下，控制输入电流减小。
进一步地，所述电压侦测电路包括：分压电路，被构造为对所述输入电压进行分压，以产生对比电压；比较器，被构造为对所述对比电压及参考电压进行比较；频率调节电路，被构造为在所述对比电压小于所述参考电压的情况下，控制所述背光驱动控制电路提供给所述升压电路的第一方波信号的频率增大，从而使所述输入电流减小。
进一步地，所述分压电路包括第一电阻器和第二电阻器，其中，第一电阻器的一端用于接收所述输入电压，第一电阻器的另一端连接至第二电阻器的一端，且连接至所述比较器的负输入端，第二电阻器的另一端电性接地。
进一步地，所述频率调节电路包括：第二MOS晶体管、第三电阻器和第四电阻器，其中，第二MOS晶体管的栅极连接至所述比较器的输出端，第二MOS晶体管的漏极连接至第三电阻器的一端，并连接至所述背光驱动控制电 路，第二MOS晶体管的源极连接至第四电阻器的一端，第三电阻器的另一端与第四电阻器的另一端均电性接地。
进一步地，所述电压侦测电路包括：分压电路，被构造为对所述输入电压进行分压，以产生对比电压；微控制单元，被构造为侦测所述对比电压是否减小；在侦测到所述对比电压减小的情况下，控制所述背光驱动控制电路提供给所述电流控制模块的第二方波信号的占空比减小，从而使所述LED串的工作电流减小，进而使所述输入电流减小。
进一步地，所述分压电路包括第一电阻器和第二电阻器，其中，第一电阻器的一端用于接收所述输入电压，第一电阻器的另一端连接至第二电阻器的一端，且连接至所述微控制单元，第二电阻器的另一端电性接地。
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、电容器，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所述LED串的正端，并连接至电容器的一端，第一MOS晶体管的栅极连接至所述背光驱动控制电路，第一MOS晶体管的源极与电容器的另一端均电性接地。
进一步地，所述电流控制模块包括第三MOS晶体管及第五电阻器，其中，第三MOS晶体管的栅极连接至所述背光驱动控制电路，第三MOS晶体管的漏极连接至所述LED串的负端，第三MOS晶体管的源极连接至第五电阻器的一端，第五电阻器的另一端电性接地。
进一步地，所述LED串包括串联的预定数量的LED。
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背光模组，其中，所述背光模组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，所述背光模组包括上述的LED背光源。
本发明的用于液晶显示设备的LED背光源及液晶显示设备，在液晶显示设备断电瞬间，可以减小输入电流的大小，从而避免产生激增的输入电流脉冲 对电路元器件产生冲击，造成损伤。
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是现有的一种用于液晶显示设备的LED背光源的电路图；
图2是根据本发明的第一实施例的用于液晶显示设备的LED背光源的模块图；
图3是根据本发明的第一实施例的用于液晶显示设备的LED背光源的电路结构图；
图4是根据本发明的第二实施例的用于液晶显示设备的LED背光源的模块图；
图5是根据本发明的第二实施例的用于液晶显示设备的LED背光源的电路结构图；
图6是根据本发明的实施例的液晶显示设备的结构图。
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2是根据本发明的第一实施例的用于液晶显示设备的LED背光源的模块图；图3是根据本发明的第一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、电压侦测电路130、背光驱动控制电路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、金属氧化物半导体(MOS)晶体管112、整流二极管113、电容器114。在本实施例中，电感器111的一端用于接收所述输入电压，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的负极连接至所述LED串150的正端，并连接至电容器114的一端，第一MOS晶体管112的栅极连接至所述背光驱动控制电路140，第一MOS晶体管112的源极与电容器114的另一端均电性接地。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。
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的栅极接收到背光驱动控制电路140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的栅极接收到背光驱动控制电路140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和电容器114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≤Vs，
其中，Vd为每个LED的正常发光电压，Vs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，Vs＝24V时，N≤3。
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：第三MOS晶体管121及第五电阻器122。其中，第三MOS晶体管121的栅极连接至背光驱动控制电路140，第三MOS晶体管121的漏极连接至所述LED串150的负端，第三MOS晶体管121的源极连接至第五电阻器122的一端，第五电阻器122的另一端电性接地。
第三MOS晶体管121的栅极接收由背光驱动控制电路140提供的第二方波信号PWM2。背光驱动控制电路140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。通常在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。
电压侦测电路130用于侦测输入电压Vin是否减小(例如，液晶显示设备断电时，向LED背光源的输入电压Vin会逐渐减小直至0)，并在侦测到输入电压Vin减小的情况下，向背光驱动控制电路140提供控制信号。在本实施例中，电压侦测电路130包括：分压电路131、比较器132和频率调节电路133。
分压电路131用于对输入电压Vin进行分压，以产生对比电压Vc。分压电路131包括第一电阻器1311和第二电阻器1312，其中，第一电阻器1311的一端用于接收输入电压Vin，第一电阻器1311的另一端连接至第二电阻器1312的一端，且连接至比较器132的负输入端，第二电阻器1312的另一端电性接地。
比较器132用于对所述对比电压Vc及参考电压Vref进行比较。比较器132的负输入端连接至第一电阻器1311的另一端，比较器132的正输入端用于接收参考电压Vref，比较器132的输出端连接至频率调节电路133的第二MOS晶体管1331的栅极。应当说明的是，所述参考电压Vref与根据本发明的实施例的液晶显示设备正常工作时的对比电压Vc相等。
频率调节电路133用于在对比电压Vc小于参考电压Vref的情况下，控制背光驱动控制电路140提供给升压电路110的第一MOS晶体管112的栅极的第一方波信号PWM1的频率增大，从而使输入电流Iin减小。频率调节电路133包括：第二MOS晶体管1331、第三电阻器1332和第四电阻器1333，其中，第二MOS晶体管1331的栅极连接至所述比较器132的输出端，第二MOS晶体管1331的漏极连接至第三电阻器1332的一端，并连接至所述背光驱动控制电路140，第二MOS晶体管1331的源极连接至第四电阻器1333的一端，第三电阻器1332的另一端与第四电阻器1333的另一端均电性接地。
以下详细说明如何使控制背光驱动控制电路140提供给升压电路110的第一MOS晶体管112的栅极的第一方波信号PWM1的频率增大，从而使输入电流Iin减小。
当根据本发明的实施例的液晶显示设备正常工作时，输入电压Vin稳定或不变，对比电压Vc＝Vin×R2/(R1+R2)稳定或不变，其中，R1表示第一电阻器1311的电阻值，R2表示第二电阻器1312的电阻值。这时，由于参考电压Vref与对比电压Vc相等，比较器132的输出端的输出电压为0。背光驱动控制电路140提供给升压电路110的第一MOS晶体管112的栅极的第一方波信号PWM1的频率与第三电阻器1332的电阻值R3成反比，当第二MOS晶体管1331的栅极接收到低电平信号，使得第二MOS晶体管1331截止时，第三电阻器1332的电阻值R3不变，第一方波信号PWM1的频率不变，输入电流Iin保持不变。
当根据本发明的实施例的液晶显示设备断电瞬间，整个LED背光源仍要保持恒定功率运行，此时输入电压Vin减小，对比电压Vc＝Vin×R2/(R1+R2)减小。这时，由于参考电压Vref大于对比电压Vc，比较器132的输出端的输出高电压。第二MOS晶体管1331的栅极接收到高电平信号，使得第二MOS晶体管1331导通，此时第三电阻器1332与第四电阻器1333并联，第一方波信号PWM1的频率与第三电阻器1332与第四电阻器1333并联后电阻值R3×R4/(R3+R4)成反比，其中，R4表示第四电阻器1333的电阻值。由于电阻值R3×R4/(R3+R4)大于电阻值R3，则第一方波信号PWM1的频率变大，换句说话，第一反攻信号PWM1的周期T减小。电感器111在第一方波信号PWM1的工作周期T内的储能时间D×T减小，电感器111上的最大电流显著减小，输入电流Iin也会减小，从而避免产生激增的输入电流脉冲对电路元器件产生冲击，造成损伤。
图4是根据本发明的第二实施例的用于液晶显示设备的LED背光源的模块图；图5是根据本发明的第二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4和图5，根据本发明的第二实施例的LED背光源包括：升压电路110、电流控制模块120、电压侦测电路130、背光驱动控制电路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、金属氧化物半导体(MOS)晶体管112、整流二极管113、电容器114。 在本实施例中，电感器111的一端用于接收所述输入电压，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的负极连接至所述LED串150的正端，并连接至电容器114的一端，第一MOS晶体管112的栅极连接至所述背光驱动控制电路140，第一MOS晶体管112的源极与电容器114的另一端均电性接地。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。
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的栅极接收到背光驱动控制电路140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的栅极接收到背光驱动控制电路140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和电容器114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≤Vs，
其中，Vd为每个LED的正常发光电压，Vs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，Vs＝24V时，N≤3。
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：第三MOS晶体管121及第五电阻器122。其中，第三MOS晶体管121的栅极连接至背光驱动控制电路140，第三MOS晶体管121的漏极连接至所述LED串150的负端，第三MOS晶体管121的源极连接至第五电阻器122的一端，第五电阻器122的另一端电性接地。
第三MOS晶体管121的栅极接收由背光驱动控制电路140提供的第二方波信号PWM2。背光驱动控制电路140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。通常在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。
电压侦测电路130用于侦测输入电压Vin是否减小(例如，液晶显示设备断电时，向LED背光源的输入电压Vin会逐渐减小直至0)，并在侦测到输入电压Vin减小的情况下，向背光驱动控制电路140提供控制信号。在本实施例中，电压侦测电路130包括：分压电路131和微控制单元(MCU)134。
分压电路131用于对输入电压Vin进行分压，以产生对比电压Vc。分压电路131包括第一电阻器1311和第二电阻器1312，其中，第一电阻器1311的一端用于接收输入电压Vin，第一电阻器1311的另一端连接至第二电阻器1312的一端，且连接至微控制单元134，第二电阻器1312的另一端电性接地。
微控制单元134用于侦测对比电压Vc是否减小。微控制单元134在侦测到对比电压Vc减小的情况下，控制背光驱动控制电路140提供给电流控制模块120的第二方波信号PWM2的占空比减小，从而使LED串150的工作电流减小，进而使输入电流Iin减小。
以下详细说明如何使控制背光驱动控制电路140提供给电流控制模块120的第二方波信号PWM2的占空比减小，从而使输入电流Iin减小。
当根据本发明的实施例的液晶显示设备正常工作时，输入电压Vin稳定或不变，对比电压Vc＝Vin×R2/(R1+R2)稳定或不变，其中，R1表示第一电阻器1311的电阻值，R2表示第二电阻器1312的电阻值。这时，微控制单元134控制背光驱动控制电路140提供给电流控制模块120的第二方波信号PWM2的占空比不变，LED串150的工作电流不变，输入电流Iin保持不变。
当根据本发明的实施例的液晶显示设备断电瞬间，整个LED背光源仍要保持恒定功率运行，此时输入电压Vin减小，对比电压Vc＝Vin×R2/(R1+R2)减小。这时，微控制单元134控制背光驱动控制电路140提供给电流控制模块120的第二方波信号PWM2的占空比减小，LED串150的工作电流减小，输入电流Iin也会减小，从而避免产生激增的输入电流脉冲对电路元器件产生冲击，造成损伤。
图6是根据本发明的实施例的液晶显示设备的结构图。
参照图6，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以及背光模组100，其中，背光模组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，其中，背光模组100上述的第一实施例或第二实施例的LED背光源。
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 (20)

  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串工作所需的工作电压；
    电流控制模块，被构造为连接到所述LED串的负端，以调节所述LED串的工作电流；
    电压侦测电路，被构造为侦测所述输入电压是否减小；在侦测到所述输入电压减小的情况下，提供控制信号给背光驱动控制电路；
    背光驱动控制电路，被构造为向所述升压电路提供第一方波信号，以控制所述升压电路实现升压的功能；向所述电流控制模块提供第二方波信号，以控制所述电流控制模块实现调节电流的功能；在接收到电压侦测电路提供的控制信号的情况下，控制输入电流减小。
  2. 根据权利要求1所述的LED背光源，其中，所述电压侦测电路包括：
    分压电路，被构造为对所述输入电压进行分压，以产生对比电压；
    比较器，被构造为对所述对比电压及参考电压进行比较；
    频率调节电路，被构造为在所述对比电压小于所述参考电压的情况下，控制所述背光驱动控制电路提供给所述升压电路的第一方波信号的频率增大，从而使所述输入电流减小。
  3. 根据权利要求2所述的LED背光源，其中，所述分压电路包括第一电阻器和第二电阻器，
    其中，第一电阻器的一端用于接收所述输入电压，第一电阻器的另一端连接至第二电阻器的一端，且连接至所述比较器的负输入端，第二电阻器的另一端电性接地。
  4. 根据权利要求2所述的LED背光源，其中，所述频率调节电路包括：第二MOS晶体管、第三电阻器和第四电阻器，
    其中，第二MOS晶体管的栅极连接至所述比较器的输出端，第二MOS 晶体管的漏极连接至第三电阻器的一端，并连接至所述背光驱动控制电路，第二MOS晶体管的源极连接至第四电阻器的一端，第三电阻器的另一端与第四电阻器的另一端均电性接地。
  5. 根据权利要求3所述的LED背光源，其中，所述频率调节电路包括：第二MOS晶体管、第三电阻器和第四电阻器，
    其中，第二MOS晶体管的栅极连接至所述比较器的输出端，第二MOS晶体管的漏极连接至第三电阻器的一端，并连接至所述背光驱动控制电路，第二MOS晶体管的源极连接至第四电阻器的一端，第三电阻器的另一端与第四电阻器的另一端均电性接地。
  6. 根据权利要求1所述的LED背光源，其中，所述电压侦测电路包括：
    分压电路，被构造为对所述输入电压进行分压，以产生对比电压；
    微控制单元，被构造为侦测所述对比电压是否减小；在侦测到所述对比电压减小的情况下，控制所述背光驱动控制电路提供给所述电流控制模块的第二方波信号的占空比减小，从而使所述LED串的工作电流减小，进而使所述输入电流减小。
  7. 根据权利要求6所述的LED背光源，其中，所述分压电路包括第一电阻器和第二电阻器，
    其中，第一电阻器的一端用于接收所述输入电压，第一电阻器的另一端连接至第二电阻器的一端，且连接至所述微控制单元，第二电阻器的另一端电性接地。
  8. 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、电容器，
    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所述LED串的正端，并连接至电容器的一端，第一MOS晶体管的栅极连接至所述背光驱动控制电路，第一MOS晶体管的源极与电容器的另一端均电性接地。
  9. 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三MOS晶体管及第五电阻器，
    其中，第三MOS晶体管的栅极连接至所述背光驱动控制电路，第三MOS晶体管的漏极连接至所述LED串的负端，第三MOS晶体管的源极连接至第五电阻器的一端，第五电阻器的另一端电性接地。
  10. 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。
  11. 一种液晶显示设备，包括相对设置的液晶显示面板及背光模组，其中，所述背光模组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，所述背光模组包括LED背光源，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串工作所需的工作电压；
    电流控制模块，被构造为连接到所述LED串的负端，以调节所述LED串的工作电流；
    电压侦测电路，被构造为侦测所述输入电压是否减小；在侦测到所述输入电压减小的情况下，提供控制信号给背光驱动控制电路；
    背光驱动控制电路，被构造为向所述升压电路提供第一方波信号，以控制所述升压电路实现升压的功能；向所述电流控制模块提供第二方波信号，以控制所述电流控制模块实现调节电流的功能；在接收到电压侦测电路提供的控制信号的情况下，控制输入电流减小。
  12. 根据权利要求11所述的液晶显示设备，其中，所述电压侦测电路包括：
    分压电路，被构造为对所述输入电压进行分压，以产生对比电压；
    比较器，被构造为对所述对比电压及参考电压进行比较；
    频率调节电路，被构造为在所述对比电压小于所述参考电压的情况下，控制所述背光驱动控制电路提供给所述升压电路的第一方波信号的频率增大，从而使所述输入电流减小。
  13. 根据权利要求12所述的液晶显示设备，其中，所述分压电路包括第一电阻器和第二电阻器，
    其中，第一电阻器的一端用于接收所述输入电压，第一电阻器的另一端连接至第二电阻器的一端，且连接至所述比较器的负输入端，第二电阻器的另一端电性接地。
  14. 根据权利要求12所述的液晶显示设备，其中，所述频率调节电路包括：第二MOS晶体管、第三电阻器和第四电阻器，
    其中，第二MOS晶体管的栅极连接至所述比较器的输出端，第二MOS晶体管的漏极连接至第三电阻器的一端，并连接至所述背光驱动控制电路，第二MOS晶体管的源极连接至第四电阻器的一端，第三电阻器的另一端与第四电阻器的另一端均电性接地。
  15. 根据权利要求13所述的液晶显示设备，其中，所述频率调节电路包括：第二MOS晶体管、第三电阻器和第四电阻器，
    其中，第二MOS晶体管的栅极连接至所述比较器的输出端，第二MOS晶体管的漏极连接至第三电阻器的一端，并连接至所述背光驱动控制电路，第二MOS晶体管的源极连接至第四电阻器的一端，第三电阻器的另一端与第四电阻器的另一端均电性接地。
  16. 根据权利要求11所述的液晶显示设备，其中，所述电压侦测电路包括：
    分压电路，被构造为对所述输入电压进行分压，以产生对比电压；
    微控制单元，被构造为侦测所述对比电压是否减小；在侦测到所述对比电压减小的情况下，控制所述背光驱动控制电路提供给所述电流控制模块的第二方波信号的占空比减小，从而使所述LED串的工作电流减小，进而使所述输入电流减小。
  17. 根据权利要求16所述的液晶显示设备，其中，所述分压电路包括第一电阻器和第二电阻器，
    其中，第一电阻器的一端用于接收所述输入电压，第一电阻器的另一端连接至第二电阻器的一端，且连接至所述微控制单元，第二电阻器的另一端电性接地。
  18. 根据权利要求11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、电容器，
    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所述LED串的正端，并连接至电容器的一端，第一MOS晶体管的栅极连接至所述背光驱动控制电路，第一MOS晶体管的源极与电容器的另一端均电性接地。
  19. 根据权利要求11所述的液晶显示设备，其中，所述电流控制模块包括第三MOS晶体管及第五电阻器，
    其中，第三MOS晶体管的栅极连接至所述背光驱动控制电路，第三MOS晶体管的漏极连接至所述LED串的负端，第三MOS晶体管的源极连接至第五电阻器的一端，第五电阻器的另一端电性接地。
  20. 根据权利要求11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。
PCT/CN2014/086315 2014-08-26 2014-09-11 用于液晶显示设备的led背光源及液晶显示设备 WO2016029512A1 (zh)

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KR1020177007697A KR101932364B1 (ko) 2014-08-26 2014-09-11 액정 디스플레이 장비를 위한 led 백라이트 소스 및 액정 디스플레이 장비
RU2017105754A RU2669061C2 (ru) 2014-08-26 2014-09-11 Светодиодные источники подсветки для жидкокристаллических устройств и жидкокристаллические устройства
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