WO2015006963A1 - 一种led背光***及显示装置 - Google Patents

一种led背光***及显示装置 Download PDF

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Publication number
WO2015006963A1
WO2015006963A1 PCT/CN2013/079650 CN2013079650W WO2015006963A1 WO 2015006963 A1 WO2015006963 A1 WO 2015006963A1 CN 2013079650 W CN2013079650 W CN 2013079650W WO 2015006963 A1 WO2015006963 A1 WO 2015006963A1
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WIPO (PCT)
Prior art keywords
led
module
control
switch
string
Prior art date
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PCT/CN2013/079650
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English (en)
French (fr)
Inventor
曹丹
Original Assignee
深圳市华星光电技术有限公司
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Filing date
Publication date
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 KR1020167003068A priority Critical patent/KR101789946B1/ko
Priority to RU2016104103A priority patent/RU2621883C1/ru
Priority to GB1522574.1A priority patent/GB2529978B/en
Priority to JP2016526392A priority patent/JP6240762B2/ja
Priority to US14/006,091 priority patent/US9084321B2/en
Publication of WO2015006963A1 publication Critical patent/WO2015006963A1/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
    • G09G3/22—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 using controlled light sources
    • G09G3/30—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 using controlled light sources using electroluminescent panels
    • G09G3/32—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 using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—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 using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—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 using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
    • 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
    • G09G3/22—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 using controlled light sources
    • G09G3/30—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 using controlled light sources using electroluminescent panels
    • G09G3/32—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 using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]

Definitions

  • the present invention relates to the field of display technologies, and in particular, to an LED backlight system and a display device.
  • the existing LED backlight system comprises an LED light string and an LED backlight control circuit for controlling the LED light string, wherein the LED backlight control circuit mainly controls the conduction and the closing of the LED light string.
  • the LED backlight control circuit mainly controls the conduction and the closing of the LED light string.
  • the technical problem to be solved by the present invention is to provide an LED backlight system and a display device, which can prevent loop instability caused when the LED lamp string differential pressure is too large, and prevent the flicker phenomenon of the LED backlight system.
  • an LED backlight system which includes: a power module for providing power; an LED display module, connected with a power module, and an LED display module including multiple a parallel LED light string; and an LED backlight control circuit, wherein the LED backlight control circuit comprises: a plurality of current modules having the same number as the plurality of LED light strings, and the current module is electrically connected with the corresponding LED light string for providing the LED The operating current of the string; the plurality of control modules having the same number as the plurality of LED strings, the control module comprising a comparison unit, a control switch unit connected to the comparison unit, and an impedance unit connected to the control switch unit, wherein the input of the comparison unit The terminal obtains the voltage of the negative terminal of the LED string, and when the voltage of the negative terminal is greater than the preset threshold voltage, outputs a control signal, and controls the control switch unit to be turned on to control the impedance unit to be connected in parallel with the current module to increase the
  • the power module includes an inductor and a diode, and the diode
  • the pole is connected to the inductor, the cathode of the diode is connected to the positive terminal of the LED string
  • the comparison unit is a comparator
  • the control switch unit is the first switch tube
  • the impedance unit is an adjustable resistor
  • the first input of the comparator is connected to the LED string
  • the negative input end, the second input end of the comparator receives the threshold voltage, the output end of the comparator outputs a control signal
  • the gate of the first switch tube is connected to the output end of the comparator
  • the source of the first switch tube is connected to one end of the current module
  • the other end of the current module is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the drain of the first switch tube.
  • the LED backlight control circuit further includes a display switch module having the same number as the LED light string, the display switch module is disposed between the current module and the LED light string, and the display switch module is a second switch tube, and is connected in series with the LED light string, The second switch receives the LED string switch to control the PWM dimming signal to control the opening and closing of the LED string.
  • an LED backlight system which includes: a power module for providing power; an LED display module connected to the power module, and the LED display module includes a plurality of parallel LED light strings; and an LED backlight control circuit, wherein the LED backlight control circuit comprises: a plurality of current modules having the same number as the plurality of LED light strings, wherein the current modules are electrically connected with the corresponding LED light strings for providing The operating current of the LED string; the plurality of control modules having the same number as the plurality of LED strings, the control module comprising a comparison unit, a control switch unit connected to the comparison unit, and an impedance unit connected to the control switch unit, wherein the comparison unit
  • the input end obtains the voltage of the negative terminal of the LED string, and when the voltage of the negative terminal is greater than the preset threshold voltage, the control signal is output, and the control switch unit is turned on to control the impedance unit to be connected in parallel with the current module to increase the LED.
  • the comparison unit is a comparator, the first input end of the comparator is connected to the negative end of the LED light string, the second input end of the comparator receives the threshold voltage, and the output end of the comparator outputs a control signal.
  • control switch unit is a first switch tube
  • impedance unit is an adjustable resistor
  • a gate of the first switch tube is connected to an output end of the comparator
  • a source of the first switch tube is connected to one end of the current module
  • a current module is The other end is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the drain of the first switch tube.
  • the LED backlight control circuit further includes a display switch module having the same number as the LED light string, the display switch module is disposed between the current module and the LED light string, and the display switch module is a second switch tube, and is connected in series with the LED light string, Two switch tube receiving LED light string switch control PWM dimming signal (PWM Dimming signal, referred to as PDIM signal), to control the opening and closing of the LED string.
  • PDIM signal Two switch tube receiving LED light string switch control PWM dimming signal
  • the LED backlight system further includes a processing module, and the processing module provides an LED light string switch to control the PWM dimming signal to the second switching tube, and the processing module further provides a fixed working voltage to the current module.
  • the gate of the second switch tube is electrically connected to the processing module, the source of the second switch tube is connected to the current module, and the drain of the second switch tube is connected to the negative end of the LED light string.
  • the current module is a fixed value resistor, one end of the fixed value resistor is connected to the source of the second switch tube, and the other end of the fixed value resistor is connected to the source of the first switch tube.
  • the first switch tube and the second switch tube are dimming MOS tubes.
  • the power module includes an inductor and a diode, wherein a cathode of the diode is connected to the inductor, and a cathode of the diode is connected to a positive terminal of the LED string.
  • a display device including a display panel and an LED backlight system for providing backlight for the display panel
  • the LED backlight system includes: a power module for providing a power supply module; the LED display module includes a plurality of parallel LED light strings; and an LED backlight control circuit, wherein the LED backlight control circuit comprises: a plurality of current modules having the same number as the plurality of LED light strings The current module is electrically connected to the corresponding LED light string for providing an operating current of the LED light string; and the plurality of control modules having the same number of the plurality of LED light strings, the control module includes a comparison unit and a control switch unit connected to the comparison unit And an impedance unit connected to the control switch unit, wherein the input end of the comparison unit acquires the voltage of the negative terminal of the LED string, and when the voltage of the negative terminal is greater than a preset threshold voltage, the control signal is output, and the control switch unit is controlled. Passing to control the imped
  • the comparison unit is a comparator, the first input end of the comparator is connected to the negative end of the LED light string, the second input end of the comparator receives the threshold voltage, and the output end of the comparator outputs a control signal.
  • control switch unit is a first switch tube
  • impedance unit is an adjustable resistor
  • a gate of the first switch tube is connected to an output end of the comparator
  • a source of the first switch tube is connected to one end of the current module
  • a current module is The other end is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the drain of the first switch tube.
  • the LED backlight control circuit further includes a display switch module having the same number as the LED light string, the display switch module is disposed between the current module and the LED light string, and the display switch module is a second switch tube, and is connected in series with the LED light string, The second switch receives the LED string switch to control the PWM dimming signal to control the opening and closing of the LED string.
  • the LED backlight system further includes a processing module, and the processing module provides an LED light string switch to control the PWM dimming signal to the second switching tube, and the processing module further provides a fixed working voltage to the current module.
  • the gate of the second switch tube is electrically connected to the processing module, the source of the second switch tube is connected to the current module, and the drain of the second switch tube is connected to the negative end of the LED light string.
  • the current module is a fixed value resistor, one end of the fixed value resistor is connected to the source of the second switch tube, and the other end of the fixed value resistor is connected to the source of the first switch tube.
  • the first switch tube and the second switch tube are dimming MOS tubes.
  • the power module includes an inductor and a diode, wherein a cathode of the diode is connected to the inductor, and a cathode of the diode is connected to a positive terminal of the LED string.
  • the present invention provides a plurality of control modules having the same number as the plurality of LED light strings, the control module including a comparison unit, a control switch unit connected to the comparison unit, and Controlling the impedance unit connected to the switch unit, wherein the input end of the comparison unit acquires the voltage of the negative terminal of the LED string, and when the voltage of the negative terminal is greater than the preset threshold voltage, the control signal is output, and the control switch unit is turned on,
  • the control impedance unit is connected in parallel with the current module to increase the operating current of the LED string, thereby reducing the voltage at the negative terminal.
  • the voltage difference between the LED strings of the present invention is too large, and when the voltage of the negative terminal of at least one of the LED strings is greater than the threshold voltage, the resistance is lowered by the parallel impedance unit to increase the LED string.
  • the working current is used to reduce the voltage of the negative terminal, so that the loop instability caused by the LED lamp string differential is too large to prevent the LED backlight system from flickering; secondly, the LED string can be adjusted in real time. Extreme voltages, thus reducing the optical requirements for LED strings, and achieving cost savings.
  • FIG. 1 is a schematic structural view of an embodiment of an LED backlight system of the present invention
  • FIG. 2 is a schematic structural view of a specific embodiment of the LED backlight system shown in FIG. 1;
  • FIG. 3 is a schematic structural view of an embodiment of a display device of the present invention.
  • FIG. 1 is a schematic structural view of an embodiment of an LED backlight system of the present invention.
  • the backlight system 10 of the present invention includes a power module 11, an LED display module 12, and an LED backlight control circuit 13.
  • the LED display module 12 is electrically connected to the power module 11 and the LED backlight control circuit 13, respectively.
  • the power module 11 is used to provide power.
  • the LED display module 12 includes a plurality of LED strings 121 connected in parallel.
  • the LED backlight control circuit 13 is for controlling the display of the LED light string 121.
  • the LED backlight control circuit 13 includes a plurality of current modules 14 and a plurality of control modules 15 having the same number as the plurality of LED light strings 121.
  • the current module 14 is electrically connected to the corresponding LED string 121 for providing an operating current of the LED string 121.
  • the control module 15 is used to control the operating current of the LED string 121 in conjunction with the current module 14.
  • the control module 15 includes a comparison unit 151, a control switch unit 152 connected to the comparison unit 151, and an impedance unit 153 connected to the control switch unit 152.
  • the input end of the comparison unit 151 acquires the voltage of the negative terminal of the LED string 121, and when the voltage of the negative terminal is greater than the preset threshold voltage, outputs a control signal, and the control switch unit 152 is turned on to control the impedance unit 153.
  • the current module 14 is connected in parallel to increase the operating current of the LED string 121, thereby reducing the voltage at the negative terminal of the LED string 121.
  • the LED backlight control circuit 13 further includes a processing module 17 and a display switch module 16 of the same number as the LED light string 121.
  • the display switch module 16 is disposed between the LED light string 121 and the current module 14 for controlling the opening and closing of the LED light string 121.
  • the processing module 17 provides the LED switch string control PWM dimming signal (PWM) for controlling the LED string 121 to be turned on and off to the display switch module 16.
  • PWM PWM dimming signal
  • the Dimming signal referred to as the PDIM signal
  • the Dimming signal further provides a fixed operating voltage to the current module 14.
  • the present invention sets the LED backlight control circuit 13 such that the voltage difference between the plurality of LED light strings 121 is large, and when the voltage of the negative terminal of at least one of the LED light strings 121 is greater than the threshold voltage, the parallel impedance unit is passed in time. 153, that is, the manner of reducing the impedance, to increase the operating current of the LED string 121, thereby reducing the voltage of the negative terminal of the LED string 121, and preventing loop instability caused by the voltage difference of the LED string 121 being too large, The flickering phenomenon of the LED backlight system 10 is prevented; secondly, since the voltage of the negative terminal of the LED string 121 can be adjusted in real time, the optical requirement for the LED string 121 is reduced, and the cost reduction effect is achieved.
  • FIG. 2 is a schematic structural view of a specific embodiment of the LED backlight system shown in FIG. 1.
  • the LED string 121 is electrically connected to the power module 11 and the LED backlight control circuit 13 to form a loop. Since there are a plurality of LED light strings 121, there are also a plurality of loops. The connection mode and working principle of each loop are the same. The following will only illustrate the connection mode and working principle of one of the loops.
  • the comparing unit 151 is a comparator 151a, and the first input end of the comparator 151a is connected to the negative terminal LED- of the LED lamp string 121 to obtain the voltage V LED- of the negative terminal LED- , and the second of the comparator 151a.
  • the input terminal receives the preset threshold voltage V ref , and the output terminal of the comparator 151a outputs a control signal.
  • the comparator 151a is also connected to a 5v DC voltage and a ground voltage, respectively.
  • the control switch unit 152 is a first switch tube 152a, and the impedance unit 153 is an adjustable resistor 153a.
  • the gate G1 of the first switch tube 152a is connected to the output end of the comparator 151a, the source S1 of the first switch tube 152a is connected to one end of the current module 14, and the other end of the current module 14 is connected to one end of the adjustable resistor 153a.
  • the other end of the adjustment resistor 153a is connected to the drain D1 of the first switching transistor 152a.
  • the display switch module 16 is a second switch tube 16a connected in series with the LED string 121, and the second switch tube 16a receives the LED string switch control PWM dimming signal to control the opening and closing of the LED string 121.
  • the gate G2 of the second switch tube 16a is electrically connected to the processing module 17, the source S2 of the second switch tube 16a is connected to the current module 14, and the drain D2 of the second switch tube 16a is connected to the negative terminal LED of the LED string 121.
  • the current module 14 is a fixed value resistor 14a. One end of the fixed value resistor 14a is connected to the source S2 of the second switch tube 16a and the adjustable resistor 153a, and the other end of the resistor 14a is connected to the source S1 of the first switch tube 152a. With the ground.
  • the processing module 17 includes a plurality of inputs and a plurality of outputs.
  • the first input terminal In1 is electrically connected between the first input end of the comparator 151a and the connection node of the negative terminal LED- of the LED lamp string 121 and the drain D2 of the second switch tube 16a to receive the negative terminal LED-
  • the voltage V LED- is electrically connected to the gate G2 of the second switching transistor 16a to provide an LED light string switch to control the PWM dimming signal to the gate G2, and the second output terminal Out2 is electrically connected at a fixed value.
  • a fixed operating voltage V B is supplied to the fixed value resistor 14a between the resistor 14a and the connection node B of the adjustable resistor 153a and the source S2 of the second switching transistor 16a.
  • the power module 11 includes an inductor 111 and a diode 112.
  • the anode of the diode 112 is connected to the inductor 111, and the cathode of the diode 112 is connected to the anode terminal LED+ of the LED string 121.
  • the LED backlight control circuit 13 further includes a switch resistor 18, detection resistors 19 and 20, and a third switch transistor 21.
  • the one end of the detecting resistor 19 is connected to the current detecting terminal ISEN of the processing module 17, the other end of the detecting resistor 19 is connected to one end of the detecting resistor 20, and the other end of the detecting resistor 20 is grounded.
  • the gate G3 of the third switch 21 is connected to one end of the switch resistor 18, the drain D3 of the third switch 21 is connected to the anode of the diode 112, and the source S3 of the third switch 21 is connected to one end of the sense resistor 20, and the switch The other end of the resistor 18 is coupled to the third output terminal Out3 of the processing module 17 to receive the switch control signal provided by the processing module 17.
  • the first switch tube 152a and the second switch tube 16a are dimming MOS tubes.
  • the third switching transistor 21 When the third output terminal Out3 of the processing module 17 supplies a switch control signal to the gate G3 of the third switching transistor 21 to be at a high level, the third switching transistor 21 is turned on, and the inductor 111 stores current energy, and the diode 112 functions at this time. Prevent the effect of current backflow.
  • the switching control signal provided by the processing module 17 to the gate G3 of the third light-emitting tube 21 is low, the third switching transistor 21 is turned off. At this time, the current stored in the inductor 111 is output from the inductor 111 and passes through the diode. After 112, the LED string 121 is output.
  • processing Module 17 When the gate G2 of the second switch 16a receives the LED string switch control PWM dimming signal provided by the processing module 17 to be at a high level, the second switch 16a is turned on, and the LED string 121 starts to be displayed. At this time, processing Module 17 further provides a fixed operating voltage V B to fixed value resistor 14a.
  • the first input of the comparator 151a receives the voltage V LED- of the negative terminal LED- of the LED string 121.
  • the V LED- is compared with a preset threshold voltage V ref . When V LED - is less than V ref , the comparator 151 a outputs a low level signal to control the first switching transistor 152 a to be turned off.
  • the comparator 151 a outputs a high level signal, and controls the first switch 152 a to be turned on to control the adjustable resistor 153 a to be connected to the circuit, and
  • the maximum value of the adjustable resistor 153a is preferentially connected to the circuit.
  • I' is greater than I, that is, when the voltage V LED- of the negative terminal LED- of the LED string 121 increases, the LED backlight control circuit 13 increases the operation of the LED string 121.
  • Current according to the current characteristic of the LED string 121, when the current of the LED string 121 increases, the voltage drop of the LED string 121 increases, and the voltage of the LED+ of the positive terminal of the LED string 121 is constant. Therefore, the voltage V LED- of the LED- negative terminal LED-LED can be reduced, thereby preventing loop instability.
  • the negative terminal of LED- controlled voltage V LED- LED light string 121 further by adjusting the variable resistor 153a, a voltage of the negative terminal V LED- LED- slightly above the threshold voltage V ref, on the one hand
  • the comparator 151a is guaranteed to output a high level signal to control the adjustable resistor 153a in parallel with the fixed value resistor 14a, and on the other hand, the voltage V LED detected by the processing module 17 from the negative terminal LED - in the specification of the processing module 17.
  • loop instability is prevented, thereby preventing the LED backlight system 10 from flickering.
  • the on frequency and duration of the second switch 16a are the same as the frequency and pulse width of the LED string switch control PWM dimming signal.
  • FIG. 3 is a schematic structural view of an embodiment of a display device according to the present invention.
  • the display device 300 of the present invention includes a display panel 301 and an LED backlight system 302 that provides backlighting for the display panel 301.
  • the LED backlight system 302 is the LED backlight system 10 described above, and details are not described herein again.
  • the present invention provides the same number of control modules 15 as the LED light string 121 in the LED backlight control circuit 13, the voltage difference between the LED light strings 121 is large, and the negative end of one of the LED light strings 121
  • the first switch 152 a is turned on, and the adjustable resistor 153 a is connected in parallel with the fixed value resistor 14 a to increase the operating current of the LED string 121 , thereby reducing the LED string 121 .
  • the voltage of the negative terminal LED-V LED- prevents leakage instability on the one hand, thereby preventing flickering, and on the other hand, the voltage of the negative terminal LED- of the LED string 121 can be adjusted in real time, thereby reducing the LED The optical requirements of the string 121 achieve cost savings.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Led Devices (AREA)

Abstract

本发明公开了一种LED背光***及显示装置。该LED背光***包括LED显示模块以及LED背光控制电路，其中LED显示模块包括LED灯串，LED背光控制电路包括电流模块、比较单元、控制开关单元以及阻抗单元，其中比较单元的输入端获取LED灯串的负极端的电压，并当负极端的电压大于预设的阈值电压吋，控制控制开关单元导通，以控制阻抗单元与电流模块并联，以降低负极端的电压。通过上述方式，本发明能够防止环路不稳，从而防止背光***闪烁的现象。

Description

一种LED背光***及显示装置
【技术领域】
本发明涉及显示技术领域，特别是涉及一种LED背光***及显示装置。
【背景技术】
目前，现有LED背光***包括LED灯串及控制LED灯串的LED背光控制电路，其中，LED背光控制电路主要是控制LED灯串的导通与关闭。但是在LED灯串导通时，因为各LED灯的内阻等不可能完全相同，容易导致各LED灯串之间存在压差，当该压差很大时，就会导致环路不稳，从而可能出现LED背光***闪烁的现象。
因此，有必要提供一种技术方案解决上述技术问题。
【发明内容】
本发明主要解决的技术问题是提供一种LED背光***及显示装置，能够防止LED灯串压差太大时引起的环路不稳，防止LED背光***的闪烁现象。
为解决上述技术问题，本发明采用的一个技术方案是：提供一种LED背光***，该LED背光***包括：电源模块，用于提供电源；LED显示模块，与电源模块连接，LED显示模块包括多个并联的LED灯串；以及LED背光控制电路，其中，LED背光控制电路包括：与多个LED灯串数量相同的多个电流模块，电流模块与对应的LED灯串电连接，用于提供LED灯串的工作电流；与多个LED灯串数量相同的多个控制模块，控制模块包括比较单元、与比较单元连接的控制开关单元以及与控制开关单元连接的阻抗单元，其中，比较单元的输入端获取LED灯串的负极端的电压，并当负极端的电压大于预设的阈值电压时，输出控制信号，控制控制开关单元导通，以控制阻抗单元与电流模块并联，以增大LED灯串的工作电流，从而降低负极端的电压；其中，电源模块包括电感和二极管，二极管的正极与电感连接，二极管的负极与LED灯串的正极端连接；比较单元为比较器，控制开关单元为第一开关管，阻抗单元为可调电阻，比较器的第一输入端连接LED灯串的负极端，比较器的第二输入端接收阈值电压，比较器的输出端输出控制信号，第一开关管的栅极连接比较器的输出端，第一开关管的源极连接电流模块的一端，电流模块的另一端连接可调电阻的一端，可调电阻的另一端连接第一开关管的漏极。
其中，LED背光控制电路还包括与LED灯串数量相同的显示开关模块，显示开关模块设置在电流模块与LED灯串之间，显示开关模块为第二开关管，与LED灯串串联连接，第二开关管接收LED灯串开关控制PWM调光信号，以控制LED灯串的开启与关闭。
为解决上述技术问题，本发明采用的另一个技术方案是：提供一种LED背光***，该LED背光***包括：电源模块，用于提供电源；LED显示模块，与电源模块连接，LED显示模块包括多个并联的LED灯串；以及LED背光控制电路，其中，LED背光控制电路包括：与多个LED灯串数量相同的多个电流模块，电流模块与对应的LED灯串电连接，用于提供LED灯串的工作电流；与多个LED灯串数量相同的多个控制模块，控制模块包括比较单元、与比较单元连接的控制开关单元以及与控制开关单元连接的阻抗单元，其中，比较单元的输入端获取LED灯串的负极端的电压，并当负极端的电压大于预设的阈值电压时，输出控制信号，控制控制开关单元导通，以控制阻抗单元与电流模块并联，以增大LED灯串的工作电流，从而降低负极端的电压。
其中，比较单元为比较器，比较器的第一输入端连接LED灯串的负极端，比较器的第二输入端接收阈值电压，比较器的输出端输出控制信号。
其中，控制开关单元为第一开关管，阻抗单元为可调电阻，其中，第一开关管的栅极连接比较器的输出端，第一开关管的源极连接电流模块的一端，电流模块的另一端连接可调电阻的一端，可调电阻的另一端连接第一开关管的漏极。
其中，LED背光控制电路还包括与LED灯串数量相同的显示开关模块，显示开关模块设置在电流模块与LED灯串之间，显示开关模块为第二开关管，与LED灯串串联连接，第二开关管接收LED灯串开关控制PWM调光信号（PWM Dimming信号，简称PDIM信号），以控制LED灯串的开启与关闭。
其中，LED背光***还包括一处理模块，处理模块向第二开关管提供LED灯串开关控制PWM调光信号，处理模块进一步向电流模块提供固定的工作电压。
其中，第二开关管的栅极电连接处理模块，第二开关管的源极连接电流模块，第二开关管的漏极连接LED灯串的负极端。
其中，电流模块为定值电阻，定值电阻的一端与第二开关管的源极连接，定值电阻的另一端连接第一开关管的源极。
其中，第一开关管和第二开关管为调光MOS管。
其中，电源模块包括电感和二极管，其中，二极管的正极与电感连接，二极管的负极与LED灯串的正极端连接。
为解决上述技术问题，本发明采用的另一个技术方案是：提供一种显示装置，其包括显示面板以及为显示面板提供背光的LED背光***，其中，LED背光***包括：电源模块，用于提供电源；LED显示模块，与电源模块连接，LED显示模块包括多个并联的LED灯串；以及LED背光控制电路，其中，LED背光控制电路包括：与多个LED灯串数量相同的多个电流模块，电流模块与对应的LED灯串电连接，用于提供LED灯串的工作电流；与多个LED灯串数量相同的多个控制模块，控制模块包括比较单元、与比较单元连接的控制开关单元以及与控制开关单元连接的阻抗单元，其中，比较单元的输入端获取LED灯串的负极端的电压，并当负极端的电压大于预设的阈值电压时，输出控制信号，控制控制开关单元导通，以控制阻抗单元与电流模块并联，以增大LED灯串的工作电流，从而降低负极端的电压。
其中，比较单元为比较器，比较器的第一输入端连接LED灯串的负极端，比较器的第二输入端接收阈值电压，比较器的输出端输出控制信号。
其中，控制开关单元为第一开关管，阻抗单元为可调电阻，其中，第一开关管的栅极连接比较器的输出端，第一开关管的源极连接电流模块的一端，电流模块的另一端连接可调电阻的一端，可调电阻的另一端连接第一开关管的漏极。
其中，LED背光控制电路还包括与LED灯串数量相同的显示开关模块，显示开关模块设置在电流模块与LED灯串之间，显示开关模块为第二开关管，与LED灯串串联连接，第二开关管接收LED灯串开关控制PWM调光信号，以控制LED灯串的开启与关闭。
其中，LED背光***还包括一处理模块，处理模块向第二开关管提供LED灯串开关控制PWM调光信号，处理模块进一步向电流模块提供固定的工作电压。
其中，第二开关管的栅极电连接处理模块，第二开关管的源极连接电流模块，第二开关管的漏极连接LED灯串的负极端。
其中，电流模块为定值电阻，定值电阻的一端与第二开关管的源极连接，定值电阻的另一端连接第一开关管的源极。
其中，第一开关管和第二开关管为调光MOS管。
其中，电源模块包括电感和二极管，其中，二极管的正极与电感连接，二极管的负极与LED灯串的正极端连接。
本发明的有益效果是：区别于现有技术的情况，本发明通过设置与多个LED灯串数量相同的多个控制模块，该控制模块包括比较单元、与比较单元连接的控制开关单元以及与控制开关单元连接的阻抗单元，其中，比较单元的输入端获取LED灯串的负极端的电压，并当负极端的电压大于预设的阈值电压时，输出控制信号，控制控制开关单元导通，以控制阻抗单元与电流模块并联，以增大LED灯串的工作电流，从而降低负极端的电压。通过上述方式，本发明在LED灯串之间的压差太大，并且其中至少一个LED灯串的负极端的电压大于阈值电压时，通过并联阻抗单元来降低阻值，以增加LED灯串的工作电流，从而达到降低负极端的电压的作用，因此能够防止LED灯串压差太大时引起的环路不稳，以防止LED背光***的闪烁现象；其次，因为可以实时调节LED灯串负极端的电压，因此降低了对LED灯串的光学要求，达到降低成本的效益。
【附图说明】
图1是本发明LED背光***的一实施例的结构示意图；
图2是图1所示的LED背光***的一具体实施方式的结构示意图；
图3是本发明显示装置的一实施例的结构示意图。
【具体实施方式】
下面结合附图和实施例对本发明进行详细的说明。
请参阅图1，图1是本发明LED背光***的一实施例的结构示意图。如图1所示，本发明的背光***10包括电源模块11、LED显示模块12以及LED背光控制电路13。
其中，LED显示模块12分别与电源模块11和LED背光控制电路13电连接。电源模块11用于提供电源。LED显示模块12包括多个并联的LED灯串121。LED背光控制电路13用于控制LED灯串121的显示。
本实施例中，LED背光控制电路13包括与多个LED灯串121数量相同的多个电流模块14以及多个控制模块15。其中，电流模块14与对应的LED灯串121电连接，其用于提供LED灯串121的工作电流。控制模块15用于结合电流模块14来控制LED灯串121的工作电流。具体而言，控制模块15包括比较单元151、与比较单元151连接的控制开关单元152以及与控制开关单元152连接的阻抗单元153。其中，比较单元151的输入端获取LED灯串121的负极端的电压，并当负极端的电压大于预设的阈值电压时，输出控制信号，控制控制开关单元152导通，以控制阻抗单元153与电流模块14并联，以增大LED灯串121的工作电流，从而降低LED灯串121的负极端的电压。
本实施例中，LED背光控制电路13还包括处理模块17以及与LED灯串121数量相同的显示开关模块16。其中，显示开关模块16设置在LED灯串121与电流模块14之间，用于控制LED灯串121的开启与关闭。处理模块17向显示开关模块16提供控制LED灯串121开启与关闭的LED灯串开关控制PWM调光信号（PWM Dimming信号，简称PDIM信号），并进一步向电流模块14提供固定的工作电压。
因此，本发明通过设置LED背光控制电路13，使得多个LED灯串121之间的压差较大，并且其中至少一个LED灯串121的负极端的电压大于阈值电压时，及时通过并联阻抗单元153，即减小阻抗的方式，来增大LED灯串121的工作电流，从而降低LED灯串121的负极端的电压，防止LED灯串121压差太大时引起的环路不稳，以防止LED背光***10的闪烁现象；其次，因为可以实时调节LED灯串121的负极端的电压，因此降低了对LED灯串121的光学要求，达到降低成本的效益。
请参阅图2，图2是图1所示的LED背光***的一具体实施方式的结构示意图。如图2所示，LED灯串121电连接电源模块11和LED背光控制电路13以组成环路。因为LED灯串121有多个，因此，环路也有多个。每个环路的连接方式和工作原理都相同，以下将仅举例说明其中一个环路的连接方式和工作原理。
本实施例中，比较单元151为比较器151a，比较器151a的第一输入端连接LED灯串121的负极端LED-，以获得负极端LED-的电压VLED-，比较器151a的第二输入端接收预设的阈值电压Vref，比较器151a的输出端输出控制信号。其中，比较器151a还分别连接5v直流电压和地电压。
控制开关单元152为第一开关管152a，阻抗单元153为可调电阻153a。其中，第一开关管152a的栅极G1连接比较器151a的输出端，第一开关管152a的源极S1连接电流模块14的一端，电流模块14的另一端连接可调电阻153a的一端，可调电阻153a的另一端连接第一开关管152a的漏极D1。
显示开关模块16为第二开关管16a，与LED灯串121串联连接，第二开关管16a接收LED灯串开关控制PWM调光信号，以控制LED灯串121的开启与关闭。具体的，第二开关管16a的栅极G2电连接处理模块17，第二开关管16a的源极S2连接电流模块14，第二开关管16a的漏极D2连接LED灯串121的负极端LED-。电流模块14为定值电阻14a，其中，定值电阻14a的一端分别连接第二开关管16a的源极S2和可调电阻153a，电阻14a的另一端分别连接第一开关管152a的源极S1与地。
处理模块17包括多个输入端与多个输出端。其中，第一输入端In1电连接在比较器151a的第一输入端与LED灯串121的负极端LED-的连接节点与第二开关管16a的漏极D2之间，以接收负极端LED-的电压VLED-，第一输出端Out1与第二开关管16a的栅极G2电连接，以向栅极G2提供LED灯串开关控制PWM调光信号，第二输出端Out2电连接在定值电阻14a与可调电阻153a的连接节点B与第二开关管16a的源极S2之间，以向定值电阻14a提供固定的工作电压VB。
电源模块11包括电感111和二极管112。其中，二极管112的正极与电感111连接，二极管112的负极与LED灯串121的正极端LED+连接。
本实施例中，LED背光控制电路13还包括开关电阻18、检测电阻19和20以及第三开关管21。其中，检测电阻19的一端连接处理模块17的电流检测端ISEN，检测电阻19的另一端连接检测电阻20的一端，检测电阻20的另一端接地。第三开关管21的栅极G3连接开关电阻18的一端，第三开关管21的漏极D3连接二级管112的正极，第三开关管21的源极S3连接检测电阻20的一端，开关电阻18的另一端连接处理模块17的第三输出端Out3，以接收处理模块17提供的开关控制信号。
本实施例中，第一开关管152a、第二开关管16a为调光MOS管。
以下将介绍LED背光***10的工作原理，因为各LED灯串121的原理相同，因此，仅举例说明其中一个LED灯串121的原理，具体为：
当处理模块17的第三输出端Out3向第三开关管21的栅极G3提供的开关控制信号为高电平时，第三开关管21导通，电感111存储电流能量，此时二极管112起到防止电流倒灌的作用。当处理模块17向第三开光管21的栅极G3提供的开关控制信号为低电平时，第三开关管21断开，此时，存储在电感111中的电流从电感111中输出并经过二极管112后输给LED灯串121。
当第二开关管16a的栅极G2接收到处理模块17提供的LED灯串开关控制PWM调光信号为高电平时，第二开关管16a导通，LED灯串121开始显示，此时，处理模块17进一步向定值电阻14a提供固定的工作电压VB。比较器151a的第一输入端接收LED灯串121的负极端LED-的电压VLED-。并将VLED-与预设的阈值电压Vref进行比较，当VLED-小于Vref时，比较器151a输出低电平信号，控制第一开关管152a断开。此时LED灯串121中的工作电流为I=VB/R14a，其中，R14a是定值电阻14a的阻值；当LED灯串121之间的压差变大，并且其中一个LED灯串121的负极端LED-的电压VLED-大于阈值电压Vref时，比较器151a输出高电平信号，控制第一开关管152a导通，以控制可调电阻153a接入电路中，并与定值电阻14a并联连接，此时LED灯串121中的工作电流为I＇=VB*（R153a+R14a）/（R153a*R14a），其中，R153a是可调电阻153a当前的阻值。本实施例中，优先将可调电阻153a的最大值接入电路中。由以上两个工作电流的运算公式可得：I＇大于I，即当LED灯串121的负极端LED-的电压VLED-增大时，LED背光控制电路13增大LED灯串121的工作电流，根据LED灯串121的电流特性，当LED灯串121的电流增大时，LED灯串121的压降就会增大，而LED灯串121的正极端LED+的电压是不变的，因此即可降低LED灯串121负极端LED-的电压VLED-，从而防止出现环路不稳。
本实施例中，进一步通过调节可调电阻153a来控制LED灯串121的负极端LED-的电压VLED-，使负极端LED-的电压VLED-稍高于阈值电压Vref，一方面可保证比较器151a输出高电平信号来控制可调电阻153a与定值电阻14a并联，另一方面又可使处理模块17从负极端LED-侦测到的电压VLED-在处理模块17的规格之内，防止出现环路不稳，从而防止LED背光***10出现闪烁的现象。
本实施例中，第二开关16a的导通频率和时长与LED灯串开关控制PWM调光信号的频率和脉宽相同。
请参阅图3，图3是本发明一种显示装置的一实施例的结构示意图。如图3所示，本发明的显示装置300包括显示面板301以及为显示面板301提供背光的LED背光***302。其中，LED背光***302为前文所述LED背光***10，在此不再赘述。
综上所述，本发明在LED背光控制电路13中设置与LED灯串121数量相同的控制模块15，在LED灯串121之间的压差较大，并且其中一个LED灯串121的负极端LED-的电压VLED-大于阈值电压Vref时，导通第一开关152a，使可调电阻153a与定值电阻14a并联，以增大LED灯串121的工作电流，从而降低LED灯串121的负极端LED-的电压VLED-，一方面防止出现环路不稳，从而防止出现闪烁现象，另一方面因为可以实时调节LED灯串121的负极端LED-的电压，因此降低了对LED灯串121的光学要求，达到降低成本的效益。
以上所述仅为本发明的实施方式，并非因此限制本发明的专利范围，凡是利用本发明说明书及附图内容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本发明的专利保护范围内。

Claims (20)

  1. 一种LED背光***，其中，所述LED背光***包括：
    电源模块，用于提供电源；
    LED显示模块，与所述电源模块连接，所述LED显示模块包括多个并联的LED灯串；以及
    LED背光控制电路，其中，所述LED背光控制电路包括：
    与多个所述LED灯串数量相同的多个电流模块，所述电流模块与对应的所述LED灯串电连接，用于提供所述LED灯串的工作电流；
    与多个所述LED灯串数量相同的多个控制模块，所述控制模块包括比较单元、与所述比较单元连接的控制开关单元以及与所述控制开关单元连接的阻抗单元，其中，所述比较单元的输入端获取所述LED灯串的负极端的电压，并当所述负极端的电压大于预设的阈值电压时，输出控制信号，控制所述控制开关单元导通，以控制所述阻抗单元与所述电流模块并联，以增大所述LED灯串的工作电流，从而降低所述负极端的电压；
    其中，所述电源模块包括电感和二极管，所述二极管的正极与所述电感连接，所述二极管的负极与所述LED灯串的正极端连接；
    所述比较单元为比较器，所述控制开关单元为第一开关管，所述阻抗单元为可调电阻，所述比较器的第一输入端连接所述LED灯串的负极端，所述比较器的第二输入端接收所述阈值电压，所述比较器的输出端输出所述控制信号，所述第一开关管的栅极连接所述比较器的输出端，所述第一开关管的源极连接所述电流模块的一端，所述电流模块的另一端连接所述可调电阻的一端，所述可调电阻的另一端连接所述第一开关管的漏极。
  2. 根据权利要求1所述的LED背光***，其中，所述LED背光控制电路还包括与所述LED灯串数量相同的显示开关模块，所述显示开关模块设置在所述电流模块与所述LED灯串之间，所述显示开关模块为第二开关管，与所述LED灯串串联连接，所述第二开关管接收LED灯串开关控制PWM调光信号，以控制所述LED灯串的开启与关闭。
  3. 一种LED背光***，其中，所述LED背光***包括：
    电源模块，用于提供电源；
    LED显示模块，与所述电源模块连接，所述LED显示模块包括多个并联的LED灯串；以及
    LED背光控制电路，其中，所述LED背光控制电路包括：
    与多个所述LED灯串数量相同的多个电流模块，所述电流模块与对应的所述LED灯串电连接，用于提供所述LED灯串的工作电流；
    与多个所述LED灯串数量相同的多个控制模块，所述控制模块包括比较单元、与所述比较单元连接的控制开关单元以及与所述控制开关单元连接的阻抗单元，其中，所述比较单元的输入端获取所述LED灯串的负极端的电压，并当所述负极端的电压大于预设的阈值电压时，输出控制信号，控制所述控制开关单元导通，以控制所述阻抗单元与所述电流模块并联，以增大所述LED灯串的工作电流，从而降低所述负极端的电压。
  4. 根据权利要求3所述的LED背光***，其中，所述比较单元为比较器，所述比较器的第一输入端连接所述LED灯串的负极端，所述比较器的第二输入端接收所述阈值电压，所述比较器的输出端输出所述控制信号。
  5. 根据权利要求4所述的LED背光***，其中，所述控制开关单元为第一开关管，所述阻抗单元为可调电阻，其中，所述第一开关管的栅极连接所述比较器的输出端，所述第一开关管的源极连接所述电流模块的一端，所述电流模块的另一端连接所述可调电阻的一端，所述可调电阻的另一端连接所述第一开关管的漏极。
  6. 根据权利要求5所述的LED背光***，其中，所述LED背光控制电路还包括与所述LED灯串数量相同的显示开关模块，所述显示开关模块设置在所述电流模块与所述LED灯串之间，所述显示开关模块为第二开关管，与所述LED灯串串联连接，所述第二开关管接收LED灯串开关控制PWM调光信号，以控制所述LED灯串的开启与关闭。
  7. 根据权利要求6所述的LED背光***，其中，所述LED背光控制电路还包括一处理模块，所述处理模块向所述第二开关管提供所述LED灯串开关控制PWM调光信号，所述处理模块进一步向所述电流模块提供固定的工作电压。
  8. 根据权利要求7所述的LED背光***，其中，所述第二开关管的栅极电连接所述处理模块，所述第二开关管的源极连接所述电流模块，所述第二开关管的漏极连接所述LED灯串的负极端。
  9. 根据权利要求8所述的LED背光***，其中，所述电流模块为定值电阻，所述定值电阻的一端与所述第二开关管的源极连接，所述定值电阻的另一端连接所述第一开关管的源极。
  10. 根据权利要求8所述的LED背光***，其中，所述第一开关管和所述第二开关管为调光MOS管。
  11. 根据权利要求3所述的LED背光***，其中，所述电源模块包括电感和二极管，其中，所述二极管的正极与所述电感连接，所述二极管的负极与所述LED灯串的正极端连接。
  12. 一种显示装置，其中，所述显示装置包括显示面板以及为显示面板提供背光的LED背光***，其中，所述LED背光***包括：
    电源模块，用于提供电源；
    LED显示模块，与所述电源模块连接，所述LED显示模块包括多个并联的LED灯串；以及
    LED背光控制电路，其中，所述LED背光控制电路包括：
    与多个所述LED灯串数量相同的多个电流模块，所述电流模块与对应的所述LED灯串电连接，用于提供所述LED灯串的工作电流；
    与多个所述LED灯串数量相同的多个控制模块，所述控制模块包括比较单元、与所述比较单元连接的控制开关单元以及与所述控制开关单元连接的阻抗单元，其中，所述比较单元的输入端获取所述LED灯串的负极端的电压，并当所述负极端的电压大于预设的阈值电压时，输出控制信号，控制所述控制开关单元导通，以控制所述阻抗单元与所述电流模块并联，以增大所述LED灯串的工作电流，从而降低所述负极端的电压。
  13. 根据权利要求12所述的显示装置，其中，所述比较单元为比较器，所述比较器的第一输入端连接所述LED灯串的负极端，所述比较器的第二输入端接收所述阈值电压，所述比较器的输出端输出所述控制信号。
  14. 根据权利要求13所述的显示装置，其中，所述控制开关单元为第一开关管，所述阻抗单元为可调电阻，其中，所述第一开关管的栅极连接所述比较器的输出端，所述第一开关管的源极连接所述电流模块的一端，所述电流模块的另一端连接所述可调电阻的一端，所述可调电阻的另一端连接所述第一开关管的漏极。
  15. 根据权利要求14所述的显示装置，其中，所述LED背光控制电路还包括与所述LED灯串数量相同的显示开关模块，所述显示开关模块设置在所述电流模块与所述LED灯串之间，所述显示开关模块为第二开关管，与所述LED灯串串联连接，所述第二开关管接收LED灯串开关控制PWM调光信号，以控制所述LED灯串的开启与关闭。
  16. 根据权利要求15所述的显示装置，其中，所述LED背光控制电路还包括一处理模块，所述处理模块向所述第二开关管提供所述LED灯串开关控制PWM调光信号，所述处理模块进一步向所述电流模块提供固定的工作电压。
  17. 根据权利要求16所述的显示装置，其中，所述第二开关管的栅极电连接所述处理模块，所述第二开关管的源极连接所述电流模块，所述第二开关管的漏极连接所述LED灯串的负极端。
  18. 根据权利要求17所述的显示装置，其中，所述电流模块为定值电阻，所述定值电阻的一端与所述第二开关管的源极连接，所述定值电阻的另一端连接所述第一开关管的源极。
  19. 根据权利要求17所述的显示装置，其中，所述第一开关管和所述第二开关管为调光MOS管。
  20. 根据权利要求12所述的显示装置，其中，所述电源模块包括电感和二极管，其中，所述二极管的正极与所述电感连接，所述二极管的负极与所述LED灯串的正极端连接。
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