WO2018126495A1 - 一种led背光驱动电路及液晶显示器 - Google Patents

一种led背光驱动电路及液晶显示器 Download PDF

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Publication number
WO2018126495A1
WO2018126495A1 PCT/CN2017/071298 CN2017071298W WO2018126495A1 WO 2018126495 A1 WO2018126495 A1 WO 2018126495A1 CN 2017071298 W CN2017071298 W CN 2017071298W WO 2018126495 A1 WO2018126495 A1 WO 2018126495A1
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Prior art keywords
led
led string
transistor
electrically connected
protection circuit
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PCT/CN2017/071298
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English (en)
French (fr)
Inventor
李文东
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深圳市华星光电技术有限公司
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Priority to US15/535,445 priority Critical patent/US20180376549A1/en
Publication of WO2018126495A1 publication Critical patent/WO2018126495A1/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]
    • 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
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • 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
    • 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
    • H05B45/54—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits in a series array of LEDs
    • 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 driving circuit and a liquid crystal display.
  • the backlight of a conventional liquid crystal display uses a cold cathode fluorescent lamp (CCFL).
  • CCFL cold cathode fluorescent lamp
  • the LED Due to the shortcomings of CCFL backlight, such as poor color reproduction ability, low luminous efficiency, high discharge voltage, poor discharge characteristics at low temperature, and long stable gradation time, the LED has been developed (Light Emitting Diode, Chinese name: Backlight technology for light-emitting diodes).
  • the LED backlight driving circuit includes a power source, a LED string and a driving chip. Specifically, the LED string positive end is electrically connected to the power source, and the LED string negative end is electrically connected to the driving chip pin. The driver chip is used to drive the LED string.
  • the inventors of the present invention have found that in the process of using the liquid crystal display, sometimes one end of the LED lamp (such as the + end) and the other end of the LED lamp (such as the - terminal) are short-circuited (Fig. 1 indicates that the last LED is short-circuited at both ends, causing the voltage at the pin of the driver chip to be electrically connected to the LED string to increase, and the pin is a low-voltage pin, once the voltage at the pin is higher than the resistance of the pin The voltage value will drive the pins of the chip to be broken down, which will cause damage to the driver chip. In severe cases, even sparks will occur, which will bring hidden dangers to the system security.
  • the prior art provides two solutions, one of which is to embed a high voltage resistant transistor at the pin of the driving chip.
  • the complicated process of the solution increases the manufacturing cost of the driving chip; the other solution is driving.
  • a low-voltage transistor is built into the pin of the chip.
  • the cost of manufacturing is low, when the voltage is higher than the withstand voltage of the transistor, the pin of the driver chip is broken down, causing the drive to be driven.
  • the pins of the moving chip are damaged; therefore, neither solution is ideal.
  • the technical problem to be solved by the embodiments of the present invention is to provide an LED backlight driving circuit and a liquid crystal display. It can reduce the pin damage of the driver chip.
  • the first aspect of the present invention provides an LED backlight driving circuit, including:
  • the LED string includes a plurality of LED lights, and a positive end of the LED string is electrically connected to the power source;
  • one end of the protection circuit is electrically connected to the negative end of the LED string
  • the first pin of the driving chip is electrically connected to the other end of the protection circuit; wherein, when the LED string is working normally, the protection circuit is turned on, when the LED lamp in the LED string When the two ends are shorted, the protection circuit is automatically disconnected for protecting the driver chip.
  • the LED string includes a first LED string
  • the first LED string includes a plurality of LED lamps connected in series, and a positive end of the first LED string is electrically connected to the power source.
  • the protection circuit includes a first protection circuit, one end of the first protection circuit is electrically connected to a negative end of the first LED string, and the other end of the first protection circuit and the first lead of the driving chip The first protection circuit is turned on when the first LED string is working normally, and the first protection circuit is automatically disconnected when the two ends of the LED lamp in the first LED string are short-circuited For protecting the driver chip.
  • the first protection circuit includes: a first protection power supply circuit; a first transistor, a drain of the first transistor electrically connected to a negative end of the first LED string, first a source of the transistor is electrically connected to the first pin of the driving chip, a gate of the first transistor is electrically connected to the first protection power supply circuit, and the first protection power supply circuit drives the first transistor close.
  • the first protection power supply circuit includes: a first protection power source; a first resistor, the first end of the first resistor is electrically connected to the first protection power source, a second end of the first resistor is electrically connected to a gate of the first transistor; a second resistor, a second resistor One end is electrically connected to the second end of the first resistor, and the second end of the second resistor is electrically connected to the source of the first transistor.
  • the first protection circuit further includes a first diode, an anode of the first diode is electrically connected to a source of the first transistor, and the first diode The cathode is electrically connected to the gate of the first transistor.
  • the resistance of the first resistor is smaller than the resistance of the second resistor.
  • the first transistor has a withstand voltage greater than or equal to 50V.
  • the LED string further includes a second LED string
  • the second LED string includes a plurality of LED lamps connected in series, and the first LED string and the second LED string are connected in parallel
  • the positive end of the second LED string is electrically connected to the power source
  • the protection circuit further includes the second protection circuit, and one end of the second protection circuit is electrically connected to a negative end of the second LED string, The other end of the second protection circuit is electrically connected to the second pin of the driving chip; when the second LED string is working normally, the second protection circuit is turned on, when the second LED string is When the LED lamp is short-circuited at both ends, the second protection circuit is automatically disconnected for protecting the driver chip.
  • a second transistor is built in the driving chip, and a withstand voltage of the second transistor is less than or equal to 10V; a drain of the second transistor is connected to the driving chip. a first pin, a source of the second transistor is grounded, and a gate of the second transistor is coupled to a control unit within the driver chip.
  • a second aspect of the present invention provides a liquid crystal display including a liquid crystal panel and a backlight module, wherein the backlight module provides a display light source to the liquid crystal panel to display an image of the liquid crystal panel.
  • the backlight module adopts an LED backlight, and the LED backlight uses the LED backlight driving circuit described above.
  • the LED backlight driving circuit of the embodiment has a protection circuit, when the LED string works normally, the protection circuit is turned on. When the LED lamps in the LED string are short-circuited at both ends, the protection circuit is automatically disconnected for protecting the driving chip. Therefore, the pins of the driver chip are not damaged, thereby reducing the damage of the driver chip.
  • FIG. 1 is a circuit diagram of a prior art LED backlight driving circuit
  • FIG. 2 is a circuit diagram of an LED backlight driving circuit of a first embodiment of the present invention
  • FIG. 3 is a schematic view showing short-circuiting of LED lights in an LED backlight driving circuit according to a first embodiment of the present invention
  • FIG. 4 is a circuit diagram of an LED backlight driving circuit of a second embodiment of the present invention.
  • the backlight driving circuit includes a power source 110, a LED string, a protection circuit, and a driving chip 130.
  • the power source 110 is configured to provide power to the LED string, and the power source 110 is, for example, a DC power source outputted by another power supply circuit, or a DC power source output by the power manager.
  • the 110 for example, provides output voltages of 36V (volts), 48V, 60V, 72V, etc., so that the LED strings can be driven.
  • the LED string includes a plurality of LED lights, and the positive end of the LED string is electrically connected to the power source 110.
  • the number of LED lights in the LED string can be determined according to requirements, for example, 2 LED lights, 4 LED lights, The number of 6 LED lights, 8 LED lights, 9 LED lights, 10 LED lights, etc., LED lights in the LED string can be connected in parallel or in series.
  • One end of the protection circuit is electrically connected to the negative end of the LED string, and the protection circuit is used to prevent the drive chip 130 from being damaged when the LED lamps are short-circuited at both ends.
  • the first pin of the driving chip 130 is electrically connected to the other end of the protection circuit; wherein, when the LED string is working normally, for example, when the LED string is normally provided with a light source, the LED string is not short-circuited at this time, and the protection circuit is normally turned on.
  • the first pin of the driving chip 130 and the negative terminal of the LED string are subjected to a normal stress; when the LED lamp in the LED string is short-circuited at both ends, for example, the + end and the end of the same LED lamp are short-circuited.
  • the protection circuit is automatically disconnected, thereby cutting off the electrical connection between the negative end of the LED and the first pin of the driving chip 130, thereby reducing the driving chip 130.
  • the first pin is broken down to prevent damage to the driving chip 130.
  • the protection circuit when the LED string is working normally, the protection circuit is turned on. When the LED lamps in the LED string are short-circuited at both ends, the protection circuit is automatically disconnected for protecting the driving chip 130. Thereby, the first pin of the driving chip 130 is not damaged, thereby reducing the damage of the driving chip 130.
  • the LED string includes a first LED string 120, and the first LED string 120 includes a plurality of LED lamps connected in series.
  • the LED lamps in the first LED string may be in parallel and in series or the like.
  • the positive end of the first LED string 120 is electrically connected to the power source 110;
  • the protection circuit includes a first protection circuit 200, and one end of the first protection circuit 200 is electrically connected to the negative end of the first LED string 120, and the first protection circuit 200
  • the other end and the first of the driving chip 130 The pin is electrically connected; when the first LED string 120 is working normally, the first protection circuit 200 is turned on, and when the two ends of the LED lamp in the first LED string 120 are short-circuited, the first protection circuit 200 is automatically disconnected for use.
  • the drive chip 130 is protected.
  • the first protection circuit 200 includes a first protection power supply circuit 210 and a first transistor Q1, and a drain of the first transistor Q1 is electrically connected to a negative terminal of the first LED string 120, the first transistor The source of Q1 is electrically connected to the first pin of the driving chip 130, and the gate of the first transistor Q1 is electrically connected to the first protection power supply circuit 210, so that the first protection power supply circuit 210 can control the conduction of the first transistor Q1. cutoff.
  • the first protection power supply circuit 210 drives the first transistor Q1 to be normally closed, that is, the first transistor Q1 is in an on state.
  • the voltage that the first protection power supply circuit 210 can supply to the gate of the first transistor Q1 is, for example, 15V, 14V, 13V, 12V, 11V, 10V, 9V, 8V, or the like.
  • the first protection power supply circuit 210 includes a first protection power source 211, a first resistor R1, and a second resistor R2.
  • the first protection power source 211 is used for outputting a power source, and the first protection power source 211 can be, for example, a DC power source outputted by another power supply circuit, or a DC power source output by the power manager.
  • the first protection power supply 211 is, for example, provided with an output voltage of 15V, 12V, 10V, 9V, etc., the first end of the first resistor R1 is electrically connected to the first protection power supply 211, and the second end of the first resistor R1 is electrically connected.
  • a first terminal of the second resistor R2 is electrically connected to the second end of the first resistor R1, and a second end of the second resistor R2 is electrically connected to the source of the first transistor Q1.
  • the first resistor R1 and the second resistor R2 are used for voltage division to ensure that the Vgs voltage of the first transistor Q1 is greater than the threshold voltage, so that the first transistor Q1 is normally closed, that is, the first transistor Q1 is kept in an on state.
  • the resistance of the first resistor R1 is smaller than the resistance of the second resistor R2, for example, the resistance of the first resistor R1 is 30k ohm, 20k ohm, 10k ohm, 5k ohm, 1k ohm, etc.
  • the resistance of the second resistor R2 is 300k ohm, 200k ohm, 100k ohm, 50k ohm, 10k ohm, and the like.
  • the ratio of the resistance of the first resistor R1 to the resistance of the second resistor R2 ranges from 1:50 to 1:5, for example, 1:50, 1:40, 1:30, 1:20, 1:10 , 1:9, 1:8, 1:7, 1:6, 1:5, etc., preferably 1:10.
  • the first protection circuit 200 further includes a first diode D1, and an anode of the first diode D1 is electrically connected to a source of the first transistor Q1, and the first diode D1 The cathode is electrically connected to the gate of the first transistor Q1, and the first diode D1 is used for voltage stabilization.
  • the first protection circuit further The first diode may not be included.
  • the first protection power supply circuit may also be other circuits known to those skilled in the art, or may be a DC power supply.
  • the first transistor Q1 when the first LED string 120 is working normally, the first transistor Q1 is turned on, so that the first LED string 120 is electrically connected to the first pin of the driving chip 130 via the source of the first transistor Q1;
  • the LEDs in the first LED string 120 are short-circuited at both ends, for example, the + end and the - end of the same LED light are shorted (see Figure 3), or the + end of the previous LED light and the next LED light -
  • the terminals are shorted, or otherwise, the overall resistance of the first LED string 120 is reduced, causing the current on the first LED string 120 to increase, and the voltage at the negative terminal of the first LED string 120 to increase, for example.
  • a sharp increase that is, the drain voltage of the first transistor Q1 will increase sharply, and the source voltage of the first transistor Q1 will also rise rapidly, and when it rises to a certain stage, the Vgs voltage of the first transistor Q1 is caused.
  • the first transistor Q1 is turned off by conduction, so that the voltage of the negative terminal of the first LED string 120 is not delivered to the first pin of the driving chip 130, thereby The first pin is not broken down, thereby protecting the first pin of the driving chip 130 and also preventing the driving core 130 damage.
  • the first transistor Q1 in order to prevent the first transistor Q1 from being broken down, is a high voltage resistant transistor, and the first transistor Q1 has a withstand voltage greater than or equal to 50V, for example, 50V, 60V, 70V, 80V, 90V, 100V, etc., in this range, the first transistor Q1 is not damaged by breakdown.
  • the first transistor Q1 is an NMOS transistor.
  • the first transistor may also be a switching component equivalent to an NMOS transistor known to those skilled in the art.
  • the driving chip 130 is provided with a second transistor Q2, the second transistor Q2 is a low voltage transistor, and the withstand voltage of the second transistor Q2 is less than or equal to 10V, for example, the withstand voltage is 10V, 9V. , 8V, 7V, 6V, 5V, etc., the cost is lower.
  • the second transistor Q2 is used to control the on and off of the first LED string 120 to achieve lighting and extinguishing of the LED lamp in the first LED string 120.
  • the drain of the second transistor Q2 is connected to the first pin of the driving chip 130, that is, electrically connected to the source of the first transistor Q1, the source of the second transistor Q2 is grounded, and the second The gate of the transistor Q2 is electrically coupled to the control unit within the driving chip 130 to control the on and off of the second transistor Q2 to control the lighting or extinction of the first LED string 120.
  • the second transistor Q2 is built in the driving chip, which can save space and reduce cost.
  • FIG. 4 is an LED backlight driving circuit according to a second embodiment of the present invention.
  • the circuit of FIG. 4 is similar to the circuit of FIG. 2. Therefore, the same component symbols represent the same components.
  • the main difference between this embodiment and the first embodiment is LED string and protection circuit.
  • the LED string further includes a second LED string 320
  • the second LED string 320 includes a plurality of LED lamps connected in series, and the first LED string 120 and the second LED string 320 are connected in parallel.
  • the positive end of the second LED string 320 is electrically connected to the power source 110;
  • the protection circuit further includes a second protection circuit 400, and one end of the second protection circuit 400 is electrically connected to the negative end of the second LED string 320, and the second protection circuit
  • the other end of the 400 is electrically connected to the second pin of the driving chip 130; when the second LED string 320 is working normally, the second protection circuit 400 is turned on, when the two ends of the LED lamp in the second LED string 320 are short-circuited, The second protection circuit 400 is automatically disconnected for protecting the driver chip 130.
  • the second protection circuit 400 includes a second protection power supply circuit 410 and a third transistor Q3.
  • the drain of the third transistor Q3 is electrically connected to the negative terminal of the second LED string 320.
  • the source of the three transistor Q3 is electrically connected to the second pin of the driving chip 130, and the gate of the third transistor Q3 is electrically connected to the second protection power supply circuit 410, so that the second protection power supply circuit 410 can control the third transistor Q3.
  • the two protection power supply circuit 410 drives the third transistor Q3 to be normally closed, that is, the third transistor Q3 is in an on state.
  • the voltage that the second protection power supply circuit 410 can supply to the gate of the third transistor Q3 is, for example, 15V, 14V, 13V, 12V, 11V, 10V, 9V, 8V, or the like.
  • the second protection power supply circuit 410 includes a second protection power source 411, a third resistor R3, and a fourth resistor R4.
  • the second protection power supply 411 is used for outputting a power supply, and the second protection power supply 411 can be a DC power supply outputted by another power supply circuit, or a DC power supply output by the power manager.
  • the second protection power supply 411 provides, for example, an output voltage of 15V, 12V, 10V, 9V, etc., the first end of the third resistor R3 is electrically connected to the second protection power supply 411, and the second end of the third resistor R3 is electrically connected.
  • the third resistor R3 and the fourth resistor R4 are used for voltage division to ensure that the Vgs voltage of the third transistor Q3 is greater than a threshold voltage, so that the third transistor Q3 is normally closed. That is, the third transistor Q3 is kept in an on state.
  • the resistance of the second resistor R2 is smaller than the resistance of the second resistor R2.
  • the ratio of the resistance of the second resistor R2 to the resistance of the second resistor R2 ranges from 1:50 to 1:5, preferably 1:10.
  • the second protection circuit 400 further includes a second diode D2, the anode of the second diode D2 is electrically connected to the source of the third transistor Q3, and the second diode D2 The cathode is electrically connected to the gate of the third transistor Q3, and the second diode D2 is used for voltage stabilization.
  • the second protection circuit may not include the second diode.
  • the third transistor Q3 when the second LED string 320 is working normally, the third transistor Q3 is turned on, so that the second LED string 320 is electrically connected to the second pin of the driving chip 130 via the source of the third transistor Q3;
  • the voltage of the negative terminal of the second LED string 320 increases, that is, the drain voltage of the third transistor Q3 increases sharply, and the source of the third transistor Q3
  • the voltage also rises rapidly, and when it rises to a certain stage, causing the Vgs voltage (voltage between the gate and the source) of the third transistor Q3 to be less than the threshold voltage, the third transistor Q3 is turned off by conduction, thereby
  • the voltage at the negative terminal of the second LED string 320 is not delivered to the second pin of the driving chip 130, so that the second pin is not broken down, thereby protecting the second pin of the driving chip 130 and also preventing the driving.
  • the chip 130 is damaged.
  • the present invention has the following advantages:
  • the LED backlight driving circuit of the embodiment has a protection circuit, when the LED string works normally, the protection circuit is turned on. When the LED lamps in the LED string are short-circuited at both ends, the protection circuit is automatically disconnected for protecting the driving chip. Therefore, the pins of the driver chip are not damaged, thereby reducing the damage of the driver chip.

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Abstract

一种LED背光驱动电路，包括：电源(110)；LED串(120)，LED串(120)包括多数个LED灯，LED串(120)的正端与电源(110)电连接；保护电路(200)，保护电路(200)的一端与LED串(120)负端电连接；驱动芯片(130)，驱动芯片(130)的第一引脚与保护电路(200)的另一端电连接；其中，当LED串(120)正常工作时，保护电路(200)导通，当LED串(120)内的LED灯两端短接时，保护电路(200)自动断开以用于保护驱动芯片(130)。具有可减少驱动芯片(130)的引脚损坏的优点。

Description

一种LED背光驱动电路及液晶显示器
本发明要求2017年01月04日递交的发明名称为“一种LED背光驱动电路及液晶显示器”的申请号201710004105.8的在先申请优先权，上述在先申请的内容以引入的方式并入本文本中。
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LED背光驱动电路及液晶显示器。
背景技术
随着显示技术的不断进步，液晶显示器的背光技术不断得到发展。传统的液晶显示器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(Light Emitting Diode，中文名：发光二极管)背光源的背光源技术。
图1是现有的一种用于液晶显示器的LED背光驱动电路。如图1所示，该LED背光驱动电路包括电源、LED串和驱动芯片，具体说来，所述LED串正端与电源电连接，所述LED串负端与驱动芯片的引脚电连接，驱动芯片用于驱动LED串。
在使用上述LED背光驱动电路的过程中本发明的发明人发现，在使用液晶显示器过程中，有时候会出现LED灯一端(如+端)与LED灯另一端(如-端)短接(图1中示意最后一个LED两端短接)，导致驱动芯片与LED串电连接的引脚处的电压会增高，而该引脚为低压引脚，一旦引脚处的电压高过引脚的耐压值，驱动芯片的引脚将被击穿，从而造成驱动芯片损坏，严重时甚至会出起火花，给系统安全带来隐患。
现有技术提供了两种解决方案，其中一种方案为在驱动芯片的引脚处内置耐高压的晶体管，然此种方案制程复杂，会增加驱动芯片的制造成本；另外一种方案为在驱动芯片的引脚处内置耐低压的晶体管，此种方案虽然制造成本较低，然当电压高于晶体管耐压值时，也会导致驱动芯片的引脚被击穿，造成驱 动芯片的引脚损坏；从而此两种解决方案都不理想。
发明内容
本发明实施例所要解决的技术问题在于，提供一种LED背光驱动电路及液晶显示器。可减少驱动芯片的引脚损坏。
为了解决上述技术问题，本发明第一方面提供了一种LED背光驱动电路，包括：
电源；
LED串，所述LED串包括多数个LED灯，所述LED串的正端与所述电源电连接；
保护电路，所述保护电路的一端与所述LED串负端电连接；
驱动芯片，所述驱动芯片的第一引脚与所述保护电路的另一端电连接；其中，当所述LED串正常工作时，所述保护电路导通，当所述LED串内的LED灯两端短接时，所述保护电路自动断开以用于保护所述驱动芯片。
在本发明第一方面一实施例中，所述LED串包括第一LED串，所述第一LED串包括多数个串联的LED灯，所述第一LED串的正端与所述电源电连接；所述保护电路包括第一保护电路，所述第一保护电路一端与所述第一LED串的负端电连接，所述第一保护电路另一端与所述驱动芯片的所述第一引脚电连接；当所述第一LED串正常工作时，所述第一保护电路导通，当所述第一LED串内的LED灯两端短接时，所述第一保护电路自动断开以用于保护所述驱动芯片。
在本发明第一方面一实施例中，所述第一保护电路包括：第一保护电源供给电路；第一晶体管，第一晶体管的漏极电连接所述第一LED串的负端，第一晶体管的源极电连接所述驱动芯片的所述第一引脚，第一晶体管的栅极电连接所述第一保护电源供给电路，所述第一保护电源供给电路驱动所述第一晶体管常闭。
在本发明第一方面一实施例中，所述第一保护电源供给电路包括：第一保护电源；第一电阻，所述第一电阻的第一端电连接所述第一保护电源，所述第一电阻的第二端电连接所述第一晶体管的栅极；第二电阻，所述第二电阻的第 一端电连接所述第一电阻的第二端，所述第二电阻的第二端电连接所述第一晶体管的源极。
在本发明第一方面一实施例中，所述第一保护电路还包括第一二极管，所述第一二极管的阳极电连接第一晶体管的源极，所述第一二极管的阴极电连接第一晶体管的栅极。
在本发明第一方面一实施例中，所述第一电阻的阻值小于所述第二电阻的阻值。
在本发明第一方面一实施例中，所述第一晶体管的耐压大于或等于50V。
在本发明第一方面一实施例中，所述LED串还包括第二LED串，所述第二LED串包括多数个串联的LED灯，所述第一LED串和所述第二LED串并联，所述第二LED串的正端与所述电源电连接；所述保护电路还包括所述第二保护电路，所述第二保护电路一端与所述第二LED串的负端电连接，所述第二保护电路另一端与所述驱动芯片的第二引脚电连接；当所述第二LED串正常工作时，所述第二保护电路导通，当所述第二LED串内的LED灯两端短接时，所述第二保护电路自动断开以用于保护所述驱动芯片。
在本发明第一方面一实施例中，所述驱动芯片内设有内置第二晶体管，所述第二晶体管的耐压小于或等于10V；所述第二晶体管的漏极连接所述驱动芯片的第一引脚，所述第二晶体管的源极接地，所述第二晶体管的栅极连接所述驱动芯片内的控制单元。
本发明实施例第二方面提供了一种液晶显示器，包括相对设置的液晶面板以及背光模组，由所述背光模组提供显示光源给所述液晶面板，以使所述液晶面板显示图像；所述背光模组采用LED背光源，所述LED背光源采用上述的LED背光驱动电路。
实施本发明实施例，具有如下有益效果：
由于本实施例的LED背光驱动电路有了保护电路，当LED串正常工作时，保护电路导通，当LED串内的LED灯两端短接时，保护电路自动断开以用于保护驱动芯片，从而不会损坏驱动芯片的引脚，从而减少了驱动芯片损坏。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是现有技术LED背光驱动电路的电路图；
图2是本发明第一实施例LED背光驱动电路的电路图；
图3是本发明第一实施例LED背光驱动电路中LED灯短接的示意图；
图4是本发明第二实施例LED背光驱动电路的电路图；
图号说明：
110-电源；120-第一LED串；130-驱动芯片；Q2-第二晶体管；200-第一保护电路；210-第一保护电源供给电路；211-第一保护电源；R1-第一电阻；R2-第二电阻；D1-第一二极管；Q1-第一晶体管；320-第二LED串；400-第二保护电路；410-第二保护电源供给电路；411-第二保护电源；R3-第三电阻；R4-第四电阻；D2-第二二极管；Q3-第三晶体管。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
本申请说明书、权利要求书和附图中出现的术语“包括”和“具有”以及它们任何变形，意图在于覆盖不排他的包含。例如包含了一系列步骤或单元的过程、方法、系统、产品或设备没有限定于已列出的步骤或单元，而是可选地还包括没有列出的步骤或单元，或可选地还包括对于这些过程、方法、产品或设备固有的其它步骤或单元。此外，术语“第一”、“第二”和“第三”等是用于区别不同的对象，而并非用于描述特定的顺序。
第一实施例
请参照图2，为本发明第一实施例提供的一种LED背光驱动电路，所述 背光驱动电路包括电源110、LED串、保护电路和驱动芯片130。
具体说来，所述电源110用于提供电力给LED串，所述电源110例如为其他供电电路输出的直流电源，也可以是电源管理器输出的直流电源等，本实施例提供的所述电源110例如提供36V(伏特)、48V、60V、72V等输出电压，从而可以驱动LED串。
所述LED串包括多数个LED灯，所述LED串的正端与电源110电连接，所述LED串中的LED灯的数量可根据需要确定，例如为2个LED灯、4个LED灯、6个LED灯、8个LED灯、9个LED灯、10个LED灯等数目，LED串中的LED灯可以并联也可以串联。
所述保护电路一端与LED串负端电连接，所述保护电路用于在LED灯的两端短接时防止驱动芯片130损坏。
所述驱动芯片130的第一引脚与保护电路的另一端电连接；其中，当LED串正常工作时，例如LED串正常提供光源时，此时LED串没有被短路，保护电路导通正常工作，驱动芯片130与LED串负端电连接的第一引脚所承受的应力在正常值；当LED串内的LED灯两端短接时，例如同一个LED灯的+端与-端短接(请参见图3)，或者上一个LED灯的+端与下一个LED灯的-端短接时，或者其他情况，此时，LED串上的电流会增大，LED串的负端电压会增加，为了防止增大后的电压施加到驱动芯片130的第一引脚上，保护电路自动断开，从而切断LED负端与驱动芯片130第一引脚的电连接，从而减少驱动芯片130的第一引脚被击穿，防止驱动芯片130损坏。
在本实施例中，由于有了保护电路，当LED串正常工作时，保护电路导通，当LED串内的LED灯两端短接时，保护电路自动断开以用于保护驱动芯片130，从而不会损坏驱动芯片130的第一引脚，从而减少了驱动芯片130损坏。
在本实施例中，所述LED串包括第一LED串120，所述第一LED串120包括多数个串联的LED灯。在本发明的其他实施例中，所述第一LED串中LED灯可以并联和串联结合等形式。所述第一LED串120的正端与电源110电连接；所述保护电路包括第一保护电路200，第一保护电路200一端与第一LED串120的负端电连接，第一保护电路200另一端与驱动芯片130的第一 引脚电连接；当第一LED串120正常工作时，第一保护电路200导通，当第一LED串120内的LED灯两端短接时，第一保护电路200自动断开以用于保护驱动芯片130。
在本实施例中，所述第一保护电路200包括第一保护电源供给电路210和第一晶体管Q1，所述第一晶体管Q1的漏极电连接第一LED串120的负端，第一晶体管Q1的源极电连接驱动芯片130的第一引脚，第一晶体管Q1的栅极电连接第一保护电源供给电路210，从而第一保护电源供给电路210可以控制第一晶体管Q1的导通和截止。在本实施例中，所述第一保护电源供给电路210驱动第一晶体管Q1常闭，也即第一晶体管Q1为导通状态。在本实施例中，所述第一保护电源供给电路210可以提供给第一晶体管Q1的栅极的电压例如为15V、14V、13V、12V、11V、10V、9V、8V等。
在本实施例中，所述第一保护电源供给电路210包括第一保护电源211、第一电阻R1和第二电阻R2。其中，所述第一保护电源211用于输出电源，所述第一保护电源211例如可以为其他供电电路输出的直流电源，也可以是电源管理器输出的直流电源等，本实施例提供的所述第一保护电源211例如提供15V、12V、10V、9V等输出电压，所述第一电阻R1的第一端电连接第一保护电源211，所述第一电阻R1的第二端电连接第一晶体管Q1的栅极；所述第二电阻R2的第一端电连接第一电阻R1的第二端，所述第二电阻R2的第二端电连接第一晶体管Q1的源极。所述第一电阻R1和第二电阻R2用来进行分压，以保证第一晶体管Q1的Vgs电压大于阈值电压，从而第一晶体管Q1为常闭，也即第一晶体管Q1保持导通状态。在本实施例中，所述第一电阻R1的阻值小于第二电阻R2的阻值，例如所述第一电阻R1的阻值为30k欧姆、20k欧姆、10k欧姆、5k欧姆、1k欧姆等，所述第二电阻R2的阻值为300k欧姆、200k欧姆、100k欧姆、50k欧姆、10k欧姆等。所述第一电阻R1的阻值与第二电阻R2的阻值的比范围为1:50-1:5，例如为1:50、1:40、1:30、1:20、1:10、1:9、1:8、1:7、1:6、1:5等，较佳的为1:10。在本实施例中，所述第一保护电路200还包括第一二极管D1，所述第一二极管D1的阳极电连接第一晶体管Q1的源极，所述第一二极管D1的阴极电连接第一晶体管Q1的栅极，所述第一二极管D1用于稳压作用。另外，在本发明的其他实施例中，所述第一保护电路还 可以不包括第一二极管。另外，在本发明的其他实施例中，所述第一保护电源供给电路还可以为本领域普通技术人员知晓的其他电路，或者为直流电源也可以。
在本实施例中，当第一LED串120正常工作时，第一晶体管Q1导通，从而第一LED串120经由第一晶体管Q1的源极电连接到驱动芯片130的第一引脚；当第一LED串120内的LED灯两端短接时，例如同一个LED灯的+端与-端短接(请参见图3)，或者上一个LED灯的+端与下一个LED灯的-端短接时，或者其他情况，此时第一LED串120的整体电阻会减小，导致第一LED串120上的电流会增大，第一LED串120的负端电压会增大，例如急剧增大，也即第一晶体管Q1的漏极电压会急剧增大，第一晶体管Q1的源极电压也会随之迅速上升，当上升到一定阶段，导致第一晶体管Q1的Vgs电压(栅极与源极之间的电压)小于阈值电压时，第一晶体管Q1由导通变为截止，从而第一LED串120负端的电压不会被输送到驱动芯片130的第一引脚处，从而第一引脚不会被击穿，从而保护了驱动芯片130的第一引脚，也防止了驱动芯片130损坏。
在本实施例中，为了防止第一晶体管Q1被击穿，所述第一晶体管Q1为耐高压的晶体管，所述第一晶体管Q1的耐压大于或等于50V，例如为50V、60V、70V、80V、90V、100V等，在此范围内第一晶体管Q1不会被击穿损坏。所述第一晶体管Q1为NMOS管，当然，在本发明的其他实施例中，所述第一晶体管还可以为本领域普通技术人员知晓的与NMOS管等同的开关元器件。
在本实施例中，所述驱动芯片130内设有第二晶体管Q2，所述第二晶体管Q2为低压晶体管，所述第二晶体管Q2的耐压小于或等于10V，例如耐压为10V、9V、8V、7V、6V、5V等，成本较低。所述第二晶体管Q2用于控制第一LED串120的导通和断开，以实现第一LED串120中LED灯的点亮和熄灭。具体说来，所述第二晶体管Q2的漏极连接驱动芯片130的第一引脚，也即电连接第一晶体管Q1的源极，所述第二晶体管Q2的源极接地，所述第二晶体管Q2的栅极电连接驱动芯片130内的控制单元，以控制第二晶体管Q2的通断以实现控制第一LED串120的点亮或熄灭。在本实施例中，所述第二晶体管Q2内置在驱动芯片内，可以节省空间，降低成本。
第二实施例
图4为本发明第二实施例提供的LED背光驱动电路，图4的电路与图2的电路相似，因此相同的元件符号代表相同的元件，本实施例与第一实施例的主要不同点为LED串和保护电路。
请参见图4，所述LED串还包括第二LED串320，所述第二LED串320包括多数个串联的LED灯，所述第一LED串120和所述第二LED串320并联。所述第二LED串320的正端与电源110电连接；所述保护电路还包括第二保护电路400，第二保护电路400一端与第二LED串320的负端电连接，第二保护电路400另一端与驱动芯片130的第二引脚电连接；当第二LED串320正常工作时，第二保护电路400导通，当第二LED串320内的LED灯两端短接时，第二保护电路400自动断开以用于保护驱动芯片130。
在本实施例中，所述第二保护电路400包括第二保护电源供给电路410和第三晶体管Q3，所述第三晶体管Q3的漏极电连接第二LED串320的负端，所述第三晶体管Q3的源极电连接驱动芯片130的第二引脚，所述第三晶体管Q3的栅极电连接第二保护电源供给电路410，从而第二保护电源供给电路410可以控制第三晶体管Q3的导通和截止。在本实施例中，所述二保护电源供给电路410驱动第三晶体管Q3常闭，也即第三晶体管Q3为导通状态。在本实施例中，所述第二保护电源供给电路410可以提供给第三晶体管Q3的栅极的电压例如为15V、14V、13V、12V、11V、10V、9V、8V等。
在本实施例中，所述第二保护电源供给电路410包括第二保护电源411、第三电阻R3和第四电阻R4。其中，所述第二保护电源411用于输出电源，所述第二保护电源411例如可以为其他供电电路输出的直流电源，也可以是电源管理器输出的直流电源等，本实施例提供的所述第二保护电源411例如提供15V、12V、10V、9V等输出电压，所述第三电阻R3的第一端电连接第二保护电源411，所述第三电阻R3的第二端电连接第三晶体管Q3的栅极；所述第四电阻R4的第一端电连接第三电阻R3的第二端，所述第四电阻R4的第二端电连接第三晶体管Q3的源极。所述第三电阻R3和第四电阻R4用来进行分压，以保证第三晶体管Q3的Vgs电压大于阈值电压，从而第三晶体管Q3为常闭， 也即第三晶体管Q3保持导通状态。在本实施例中，所述第二电阻R2的阻值小于第二电阻R2的阻值。所述第二电阻R2的阻值与第二电阻R2的阻值的比范围为1:50-1:5，较佳的为1:10。在本实施例中，所述第二保护电路400还包括第二二极管D2，所述第二二极管D2的阳极电连接第三晶体管Q3的源极，所述第二二极管D2的阴极电连接第三晶体管Q3的栅极，所述第二二极管D2用于稳压作用。另外，在本发明的其他实施例中，所述第二保护电路还可以不包括第二二极管。
在本实施例中，当第二LED串320正常工作时，第三晶体管Q3导通，从而第二LED串320经由第三晶体管Q3的源极电连接到驱动芯片130的第二引脚；当第二LED串320内的LED灯两端短接时，第二LED串320的负端电压会增大，也即第三晶体管Q3的漏极电压会急剧增大，第三晶体管Q3的源极电压也会随之迅速上升，当上升到一定阶段，导致第三晶体管Q3的Vgs电压(栅极与源极之间的电压)小于阈值电压时，第三晶体管Q3由导通变为截止，从而第二LED串320负端的电压不会被输送到驱动芯片130的第二引脚处，从而第二引脚不会被击穿，从而保护了驱动芯片130的第二引脚，也防止了驱动芯片130损坏。本实施例可以应用需要较多个LED灯的场合，可以满足不同场合的需要。
需要说明的是，本说明书中的各个实施例均采用递进的方式描述，每个实施例重点说明的都是与其它实施例的不同之处，各个实施例之间相同相似的部分互相参见即可。对于装置实施例而言，由于其与方法实施例基本相似，所以描述的比较简单，相关之处参见方法实施例的部分说明即可。
通过上述实施例的描述，本发明具有以下优点：
由于本实施例的LED背光驱动电路有了保护电路，当LED串正常工作时，保护电路导通，当LED串内的LED灯两端短接时，保护电路自动断开以用于保护驱动芯片，从而不会损坏驱动芯片的引脚，从而减少了驱动芯片损坏。
以上所揭露的仅为本发明较佳实施例而已，当然不能以此来限定本发明之权利范围，因此依本发明权利要求所作的等同变化，仍属本发明所涵盖的范围。

Claims (10)

  1. 一种LED背光驱动电路，其特征在于，包括：
    电源；
    LED串，所述LED串包括多数个LED灯，所述LED串的正端与所述电源电连接；
    保护电路，所述保护电路一端与所述LED串负端电连接；
    驱动芯片，所述驱动芯片的第一引脚与所述保护电路的另一端电连接；其中，当所述LED串正常工作时，所述保护电路导通，当所述LED串内的LED灯两端短接时，所述保护电路自动断开以用于保护所述驱动芯片。
  2. 如权利要求要求1所述的LED背光驱动电路，其特征在于，所述LED串包括第一LED串，所述第一LED串包括多数个串联的LED灯，所述第一LED串的正端与所述电源电连接；所述保护电路包括第一保护电路，所述第一保护电路一端与所述第一LED串的负端电连接，所述第一保护电路另一端与所述驱动芯片的所述第一引脚电连接；当所述第一LED串正常工作时，所述第一保护电路导通，当所述第一LED串内的LED灯两端短接时，所述第一保护电路自动断开以用于保护所述驱动芯片。
  3. 如权利要求2所述的LED背光驱动电路，其特征在于，所述第一保护电路包括：
    第一保护电源供给电路；
    第一晶体管，第一晶体管的漏极电连接所述第一LED串的负端，第一晶体管的源极电连接所述驱动芯片的所述第一引脚，第一晶体管的栅极电连接所述第一保护电源供给电路，所述第一保护电源供给电路驱动所述第一晶体管常闭。
  4. 如权利要求3所述的LED背光驱动电路，其特征在于，所述第一保护电源供给电路包括：
    第一保护电源；
    第一电阻，所述第一电阻的第一端电连接所述第一保护电源，所述第一电阻的第二端电连接所述第一晶体管的栅极；
    第二电阻，所述第二电阻的第一端电连接所述第一电阻的第二端，所述第二电阻的第二端电连接所述第一晶体管的源极。
  5. 如权利要求4所述的LED背光驱动电路，其特征在于，所述第一保护电路还包括：
    第一二极管，所述第一二极管的阳极电连接第一晶体管的源极，所述第一二极管的阴极电连接第一晶体管的栅极。
  6. 如权利要求4或5所述的LED背光驱动电路，其特征在于，所述第一电阻的阻值小于所述第二电阻的阻值。
  7. 如权利要求3-5任意一项所述的LED背光驱动电路，其特征在于，所述第一晶体管的耐压大于或等于50V。
  8. 如权利要求2所述的LED背光驱动电路，其特征在于，所述LED串还包括第二LED串，所述第二LED串包括多数个串联的LED灯，所述第一LED串和所述第二LED串并联，所述第二LED串的正端与所述电源电连接；所述保护电路还包括所述第二保护电路，所述第二保护电路一端与所述第二LED串的负端电连接，所述第二保护电路另一端与所述驱动芯片的第二引脚电连接；当所述第二LED串正常工作时，所述第二保护电路导通，当所述第二LED串内的LED灯两端短接时，所述第二保护电路自动断开以用于保护所述驱动芯片。
  9. 如权利要求1所述的LED背光驱动电路，其特征在于，所述驱动芯片内设有内置第二晶体管，所述第二晶体管的耐压小于或等于10V；所述第二晶体管的漏极连接所述驱动芯片的第一引脚，所述第二晶体管的源极接地，所述 第二晶体管的栅极连接所述驱动芯片内的控制单元。
  10. 一种液晶显示器，其特征在于，包括相对设置的液晶面板以及背光模组，由所述背光模组提供显示光源给所述液晶面板，以使所述液晶面板显示图像；所述背光模组采用LED背光源，所述LED背光源采用如权利要求1-9任一所述的LED背光驱动电路。
PCT/CN2017/071298 2017-01-04 2017-01-16 一种led背光驱动电路及液晶显示器 WO2018126495A1 (zh)

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