US9271361B2 - Backlight driving circuit, LCD device, and method for driving the backlight driving circuit - Google Patents

Backlight driving circuit, LCD device, and method for driving the backlight driving circuit Download PDF

Info

Publication number
US9271361B2
US9271361B2 US13/984,530 US201313984530A US9271361B2 US 9271361 B2 US9271361 B2 US 9271361B2 US 201313984530 A US201313984530 A US 201313984530A US 9271361 B2 US9271361 B2 US 9271361B2
Authority
US
United States
Prior art keywords
cathode
comparator
unit
coupled
voltage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related, expires
Application number
US13/984,530
Other versions
US20140354180A1 (en
Inventor
Hua Zhang
Fei Li
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TCL China Star Optoelectronics Technology Co Ltd
Original Assignee
Shenzhen China Star Optoelectronics Technology Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CN201310203882.7A external-priority patent/CN103280193B/en
Application filed by Shenzhen China Star Optoelectronics Technology Co Ltd filed Critical Shenzhen China Star Optoelectronics Technology Co Ltd
Assigned to SHENZHEN CHINA STAR OPTOELECTRONICS TECHNOLOGY CO., LTD reassignment SHENZHEN CHINA STAR OPTOELECTRONICS TECHNOLOGY CO., LTD ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LI, FEI, ZHANG, HUA
Publication of US20140354180A1 publication Critical patent/US20140354180A1/en
Application granted granted Critical
Publication of US9271361B2 publication Critical patent/US9271361B2/en
Expired - Fee Related legal-status Critical Current
Adjusted expiration legal-status Critical

Links

Images

Classifications

    • H05B33/0845—
    • 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
    • G09G3/3426—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines the different display panel areas being distributed in two dimensions, e.g. matrix
    • H05B33/0815—
    • H05B33/0827—
    • 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]
    • H05B45/10—Controlling the intensity 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
    • H05B45/3725—Switched mode power supply [SMPS]
    • 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
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/08—Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared

Definitions

  • the present disclosure relates to the field of liquid crystal displays (LCDs), and more particularly to a backlight driving circuit, an LCD device, and a method for driving the backlight driving circuit.
  • LCDs liquid crystal displays
  • a liquid crystal display (LCD) device includes an LCD panel and a backlight unit.
  • a typical backlight unit uses a light emitting diode (LED) lightbar as light source and uses an LED backlight driving circuit to drive the LED lightbar to display.
  • the typical LED backlight driving circuit includes an LED lightbar 20 , a power supply 10 driving the LED lightbar 20 to display, and a constant current driving chip 30 controlling the power supply 10 and the LED lightbar 20 .
  • the constant current driving chip 30 includes an adjusting unit 32 that adjusts brightness of the LED lightbar 20 .
  • An input end of the adjusting unit 32 is connected with a cathode of the LED lightbar, and an output end of the adjusting unit 32 is coupled to a ground terminal of the LED backlight driving circuit through a resistor.
  • the aim of the present disclosure is to provide a backlight driving circuit, a liquid crystal display (LCD) device, and a method for driving the backlight driving circuit capable of reducing power loss of a constant current driving chip and improving stability of an entire backlight driving circuit after any one of LED lamps of the LED lightbar short-circuits.
  • LCD liquid crystal display
  • a backlight driving circuit comprises a light emitting diode (LED) lightbar, a power supply driving the LED lightbar, a constant current driving chip controlling the power supply and the LED lightbar, and a control unit monitoring a voltage of a cathode of the LED lightbar.
  • the constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar. An input end of the adjusting unit is coupled to the cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, a resistance value of the load unit is adjusted.
  • the control unit controls the load unit to reduce the resistance value of the load unit.
  • the load unit comprises N resistors connected in parallel, and (N ⁇ 1) resistors are connected with the controllable switches in series; when the voltage of the cathode of the LED lightbars is greater than or equal to the preset threshold, the control unit controls at least one controllable switch to turn on.
  • N is a natural number that is greater than or equal to 2.
  • This is specific circuit of the load unit using a plurality of resistors connected in parallel, and each of the resistors is controlled by the controllable switch. As a number of the controllable switch being on increases, the resistance value of the load unit reduces.
  • the control unit controls at least one controllable switch to turn on, which reduces the resistance value of the load unit.
  • the load unit comprises a first resistor and a second resistor that are connected in parallel.
  • the second resistor is connected with a first controllable switch in series.
  • the control unit controls the first controllable switch to turn on.
  • control unit comprises a first comparator and a monitor unit.
  • a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit.
  • the first comparator When the voltage of the cathode of the LED lightbar is greater than or equal to the first reference voltage, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit.
  • the first reference voltage is less than or equal to the preset threshold. The first comparator quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold.
  • the first comparator When the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator outputs the reserved voltage, namely the first comparator outputs a low level signal at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator outputs a high level signal.
  • the monitor unit may determine whether the LED lamp is short-circuited, and further controls the load unit to reduce the resistance value of the load unit.
  • the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal.
  • the adjusting assembly is coupled to the adjusting unit.
  • the adjusting assembly reduces the duty cycle of the PWM dimming signal.
  • the resistance value of the load unit reduces, current flowing through the LED lightbar increases, and brightness of the LED lightbar increases.
  • the adjusting assembly of the monitor unit In order to make brightness of the LED lightbar that is short-circuited be consistent with brightness of the LED lightbars that are not short-circuited, the adjusting assembly of the monitor unit outputs a PWM dimming signal having a small duty cycle to the adjusting unit of the constant current driving chip, which allows current of the LED lightbar that is short-circuited to be consistent with current of the LED lightbars that are not short-circuited.
  • the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch.
  • the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit.
  • An output end of the adjusting assembly is coupled to a control end of the second controllable switch. This is a specific circuit of the adjusting unit using the second controllable switch to control effective current of the LED lightbar.
  • the load unit comprises a first resistor and a second resistor that are connected in parallel, where the second resistor is connected with a first controllable switch in series.
  • the control unit comprises a first comparator and a monitor unit.
  • a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit.
  • the first reference voltage is less than or equal to the preset threshold.
  • the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal.
  • the adjusting assembly is coupled to the adjusting unit.
  • the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch.
  • the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit.
  • An output end of the adjusting assembly is coupled to a control end of the second controllable switch.
  • the first comparator When the voltage of the cathode of the LED lightbars is greater than or equal to the first reference voltage, the first comparator outputs a reserved voltage, and the control unit controls the first controllable switch to turn on, and simultaneously, the adjusting assembly reduces the duty cycle of the PWM dimming signal.
  • the load unit uses two connected-in-parallel resistors, first controllable switch is used to control the second resistor.
  • first controllable switch is used to control the second resistor.
  • the control unit controls the first controllable switch to turn on, and current flows through the second resistor.
  • the resistance value of the load unit is equal to the resistance value of two connected-in-parallel resistors, which is less than the first resistor (the first resistor is equal to the resistance value of the load unit when the first controllable switch turns off).
  • the present disclosure uses a method of using two connected-in-parallel resistors, and only needs to control one controllable switch, thus the control method is easy, development difficulty and hardware cost are reduced.
  • the first comparator quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold.
  • the first comparator outputs the reserved voltage, namely the first comparator outputs a low level signal at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator outputs a high level signal.
  • the monitor unit may determine whether the LED lamp is short-circuited, and further controls the load unit to reduce the resistance value of the load unit.
  • the adjusting assembly of the monitor unit outputs a PWM dimming signal having a small duty cycle to the adjusting unit of the constant current driving chip, which allows current flowing through the LED lightbar that is short-circuited to be consistent with current of the LED lightbars that are not short-circuited.
  • a light crystal display (LCD) device comprises a backlight driving circuit of the present disclosure.
  • the backlight driving circuit comprises an LED lightbar, a power supply driving the LED lightbar, and a constant current driving chip controlling the power supply and the LED lightbar.
  • the constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar, an input end of the adjusting unit is coupled to a cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, a resistance value of the load unit is adjusted.
  • the method comprises:
  • the step B comprises: when reducing the resistance value of the load unit, reducing a duty cycle of a driving signal of the adjusting unit, which allows effective current flowing through the LED lightbar that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
  • the resistance value of the load unit reduces, current flowing through the LED lightbar increases, and brightness of the LED lightbar increases.
  • the adjusting assembly of the monitor unit In order to make brightness of the LED lightbar that is short-circuited be consistent with brightness of the LED lightbars that are not short-circuited, the adjusting assembly of the monitor unit outputs a PWM dimming signal having a small duty cycle to the adjusting unit of the constant current driving chip, which allows current of the LED lightbar that is short-circuited to be consistent with current of the LED lightbars that are not short-circuited.
  • current is determined by a reference voltage V input to the adjusting unit and a resistance value R of a resistor connected in series between the adjusting unit and the ground terminal of the backlight driving circuit.
  • the adjusting unit controls the duty cycle of the current of the LED lightbar to adjust backlight brightness of the LED lightbar.
  • a voltage Vo outputted by the power supply is relative to the current flowing through the LED lightbar, when the current flowing through the LED lightbar is great, the voltage Vo driving the LED lightbars is corresponding great.
  • a redundant voltage of the cathode of the LED lightbar (about 6 V) is input to the adjusting unit, which results in increasing temperature of the constant current driving chip, thereby affecting stability of an entire backlight driving circuit.
  • the present disclosure uses the control unit and the load unit, when one or more LED lamps of the LED lightbar short-circuit, the voltage of the cathode of the LED lightbar increases.
  • the voltage of the cathode of the LED lightbar is regarded as the preset threshold when one or more LED lamps of the LED lightbars short-circuit.
  • the control unit monitors that the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit.
  • FIG. 1 is a schematic diagram of a typical backlight driving circuit
  • FIG. 2 is a schematic diagram of a backlight driving circuit of a first example of the present disclosure
  • FIG. 3 is a schematic diagram of a backlight driving circuit of a second example of the present disclosure.
  • FIG. 4 is a flowchart of a method for driving a backlight driving circuit of a third example of the present disclosure.
  • the present disclosure provides a liquid crystal display (LCD) device comprising an LCD panel and a backlight unit.
  • the backlight unit comprises a backlight driving circuit.
  • the backlight driving circuit comprises a light emitting diode (LED) lightbar, a power supply driving the LED lightbar to display, and a constant current driving chip controlling the power supply and the LED lightbar.
  • the constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar.
  • An input end of the adjusting unit is coupled to a cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, where a resistance value of the load unit can be adjusted.
  • the backlight driving circuit further comprises a control unit that monitors voltage of the cathode of the LED lightbar.
  • control unit controls the load unit to reduce a resistance value of the load unit.
  • current is determined by a reference voltage V input to the adjusting unit and a resistance value R of a resistor connected in series between the adjusting unit and a ground terminal of the backlight driving circuit.
  • the adjusting unit adjusts backlight brightness of the LED lightbar by controlling a duty cycle of the current flowing through the LED lightbar.
  • a voltage Vo outputted by the power supply is relative to the current flowing through the LED lightbar, when the current flowing through the LED lightbar is great, the voltage Vo driving the LED lightbar is corresponding great.
  • a redundant voltage of the cathode of the LED lightbar (about 6 V) is input to the adjusting unit, which results in increasing temperature of the constant current driving chip, thereby affecting stability of an entire backlight driving circuit.
  • the present disclosure uses the control unit and the load unit, when one or more LED lamps of the LED lightbar short-circuit, the voltage of the cathode of the LED lightbar increases.
  • the voltage of the cathode of the LED lightbar is regard as a preset threshold when one or more LED lamps of the LED lightbar short-circuit.
  • the control unit monitors that the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit.
  • a backlight driving circuit 1 of a first example comprises a light emitting diode (LED) lightbar 20 , a power supply 10 driving the LED lightbar 20 , and a constant current driving chip 30 controlling the power supply 10 and the LED lightbar 20 .
  • the constant current driving chip 30 comprises a main control unit 31 that drives the power supply, and an adjusting unit 32 that adjusts brightness of the LED lightbars 20 .
  • An input end of the adjusting unit 32 is coupled to a cathode of the LED lightbar 20 , and an output end of the adjusting unit 32 is coupled to a load unit 40 , a resistance value of the load unit 40 can be adjusted.
  • the backlight driving circuit 1 further comprises a control unit 50 that monitors a voltage of the cathode of the LED lightbar.
  • a plurality of the LED lightbars 20 are shown in FIG. 2 .
  • a plurality of load units 40 and a plurality of control units 50 are correspondingly arranged in the backlight driving circuit and are used to control the plurality of LED lightbars 20 ;
  • the first example only takes one LED lightbar, the load unit 40 , and the control unit 50 for example to further describe the present disclosure, where the load unit 40 and the control unit 50 correspond to the one LED lightbar.
  • each of the LED lightbars 20 corresponds to one load unit 40 and one control unit 50 , structures of all units are same, and structures of all control units are same.
  • the load unit 40 comprises a first resistor R 1 and a second resistor R 2 that are connected in parallel.
  • the second resistor R 2 is connected with a first controllable switch Q 1 in series.
  • the control unit 50 comprises a first comparator OP 1 and a monitor unit 51 .
  • the monitor unit 51 uses a microcontroller (MCU) or other control chips.
  • a first reference voltage VF 1 is input to a first input end of the first comparator OP 1
  • a second input end of the first comparator OP 1 is coupled to the cathode of the LED lightbar 20
  • an output end of the first comparator OP 1 is coupled to the monitor unit 51 .
  • the first comparator OP 1 When the voltage of the cathode of the LED lightbar 20 is greater than or equal to the first reference voltage VF 1 , the first comparator OP 1 outputs a reserved voltage, the monitor unit 51 controls the first controllable switch Q 1 to turn on.
  • the first reference voltage VF 1 is less than or equal to the preset threshold, the first reference voltage VF 1 uses common voltage in the backlight driving circuit, such as 5V, 12V, and the like.
  • the load unit 40 uses two connected-in-parallel resistors, and the first controllable switch Q 1 is used to control the second resistor R 2 .
  • the monitor unit 51 of the control unit 50 controls the first controllable switch Q 1 to turn on, and current flows through the second resistor R 2 .
  • the resistance value of the load unit 40 is equal to the resistance value of two connected-in-parallel resistors, which is less than the first resistor R 1 (R 1 is equal to the resistance value of the load unit 40 when the first controllable switch Q 1 turns off).
  • the first comparator OP 1 quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold. When the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP 1 outputs the reserved voltage, namely the first comparator OP 1 outputs a low level signal (logic 0) at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP 1 outputs a high level signal (logic 1). Thus, according to change of the output voltage of the first comparator OP 1 , the monitor unit 51 may determine whether the LED lamp is short-circuited, and further controls the load unit to reduce the resistance value of the load unit.
  • the present disclosure uses a method of using two connected-in-parallel resistors, and only one controllable switch needs to be controlled, thus the control method is easy, development difficulty and hardware cost are reduced.
  • the present disclosure should not be limited to use two connected-in-parallel resistors and may further use a plurality of resistors connected in parallel.
  • the load unit 40 comprises N resistors connected in parallel, where (N ⁇ 1) resistors are connected with the controllable switches in series, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, as long as at least one controllable switch turns on, the resistance value of the load unit can be reduced.
  • N is a natural number that is greater than or equal to 2.
  • a backlight driving circuit 1 of a second example comprises an LED lightbar 20 , a power supply 10 driving the LED lightbar 20 , and a constant current driving chip 30 controlling the power supply 10 and the LED lightbar 20 .
  • the constant current driving chip 30 comprises a main control unit 31 that drives the power supply, and an adjusting unit 32 that adjusts brightness of the LED lightbars 20 .
  • An input end of the adjusting unit 32 is coupled to a cathode of the LED lightbar 20
  • an output end of the adjusting unit 32 is coupled to a load unit 40 , where a resistance value of the load unit 40 can be adjusted.
  • the backlight driving circuit 1 further comprises a control unit 50 that monitors a voltage of the cathode of the LED lightbar.
  • a plurality of the LED lightbars 20 are shown in FIG. 3 .
  • a plurality of load units 40 and a plurality of control units 50 are correspondingly arranged in the backlight driving circuit and are used to control the plurality of LED lightbars 20 .
  • the second example only takes one LED lightbar, the load unit 40 , and the control unit 50 for example to further describe the present disclosure, where the load unit 40 and the control unit 50 correspond to the one LED lightbar. It should be understood that each of the LED lightbars 20 corresponds to one load unit 40 and one control unit 50 , structures of all load units are same, and structures of all control units are same.
  • the load unit 40 comprises the first resistor R 1 and the second resistor R 2 that are connected in parallel.
  • the second resistor R 2 is connected with a first controllable switch Q 1 in series.
  • the control unit 50 comprises a first comparator OP 1 and a monitor unit 51 .
  • the monitor unit 51 uses a microcontroller (MCU) or other control chips.
  • a first reference voltage VF 1 is input to a first input end of the first comparator OP 1 , a second input end of the first comparator OP 1 is coupled to the cathode of the LED lightbar 20 , and an output end of the first comparator OP 1 is coupled to the monitor unit 51 .
  • the first reference voltage VF 1 is less than or equal to the preset threshold, the first reference voltage VF 1 uses common voltage in the backlight driving circuit, such as 5V, 12V, and the like.
  • the monitor unit 51 comprises an adjusting assembly 52 which adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal.
  • the adjusting assembly 52 is coupled to the adjusting unit 32 .
  • the adjusting unit 32 comprises a second controllable switch Q 2 and a second comparator OP 2 coupled to the second controllable switch Q 2 .
  • a second reference voltage V 2 is input to a non-inverting input end of the second comparator OP 2 , and an inverting input end of the second comparator OP 2 is coupled to an output end of the second controllable switch Q 2 .
  • the second controllable switch Q 2 is connected in series between the cathode of the LED lightbar 20 and the load unit 40 .
  • An output end of the adjusting assembly 52 is coupled to a control end of the second controllable switch Q 2 .
  • the first comparator OP 1 When the voltage of the cathode of the LED lightbar 20 is greater than or equal to the first reference voltage VF 1 , the first comparator OP 1 outputs a reserved voltage.
  • the monitor unit 51 controls the first controllable switch Q 1 to turn on, in the meantime, the adjusting assembly 52 reduces the duty cycle of PWM dimming signal outputted by the adjusting assembly, which allows effective current flowing through the LED lightbar 20 that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
  • the load unit 40 uses two connected-in-parallel resistors, and the first controllable switch Q 1 is used to control the second resistor R 2 .
  • the control unit 50 controls the first controllable switch Q 1 to turn on, and current flows through the second resistor R 2 .
  • the resistance value of the load unit 40 is equal to the resistance value of two connected-in-parallel resistors, which is less than the first resistor R 1 (R 1 is equal to the resistance value of the load unit 40 when the first controllable switch Q 1 turns off).
  • the present disclosure uses a method of using two connected-in-parallel resistors, and only needs to control one controllable switch, thus the control method is easy, development difficulty and hardware cost are reduced.
  • the first comparator OP 1 quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold. When the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP 1 outputs the reserved voltage, namely the first comparator OP 1 outputs a low level signal (logic 0) at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP 1 outputs a high level signal (logic 1). Thus, according to change of the output voltage of the first comparator OP 1 , the monitor unit 51 may determine whether the LED lamp is short-circuited, further controls the load unit to reduce the resistance value of the load unit.
  • the adjusting assembly 52 of the monitor unit 51 outputs a PWM dimming signal having a small duty cycle to the adjusting unit 32 of the constant current driving chip 30 , which allows current flowing through the LED lightbar 20 that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
  • the present disclosure uses a method of using two connected-in-parallel resistors, only needs to control one controllable switch, thus the control method is easy, development difficulty and hardware cost are reduced.
  • the present disclosure should not be limited to use two connected-in-parallel resistors and may use a plurality of resistors connected in parallel.
  • the load unit 40 comprises N resistors connected in parallel, where (N ⁇ 1) resistors are connected with the controllable switch in series, when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, as long as at least one controllable switch turns on, the resistance value of the load unit can be reduced.
  • N is a natural number that is greater than or equal to 2.
  • the present disclosure provides a method for driving a backlight driving circuit
  • the backlight driving circuit comprises an LED lightbar, a power supply driving the LED lightbar, and a constant current driving chip controlling the power supply and the LED lightbar.
  • the constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar.
  • An input end of the adjusting unit is coupled to a cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, where a resistance value of the load unit can be adjusted.
  • the method comprises:
  • the step B comprises: when reducing the resistance value of the load unit, reducing a duty cycle of a driving signal of the adjusting unit, which allows effective current flowing through the LED lightbar 20 that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
  • the controllable switch of the present disclosure uses semiconductor switch device such as a metal-oxide-semiconductor field-effect transistor (MOSFET).
  • MOSFET metal-oxide-semiconductor field-effect transistor

Landscapes

  • 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)

Abstract

A backlight driving circuit includes a light emitting diode (LED) lightbar, a power supply driving the LED lightbar, a constant current driving chip controlling the power supply and the LED lightbar, and a control unit monitoring a voltage of a cathode of the LED lightbar. The constant current driving chip includes a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar. An input end of the adjusting unit is coupled to the cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, a resistance value of the load unit may be adjusted. When the voltage of the cathode of the LED lightbar is greater than or equal to a preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit.

Description

TECHNICAL FIELD
The present disclosure relates to the field of liquid crystal displays (LCDs), and more particularly to a backlight driving circuit, an LCD device, and a method for driving the backlight driving circuit.
BACKGROUND
A liquid crystal display (LCD) device includes an LCD panel and a backlight unit. A typical backlight unit uses a light emitting diode (LED) lightbar as light source and uses an LED backlight driving circuit to drive the LED lightbar to display. As shown in FIG. 1, the typical LED backlight driving circuit includes an LED lightbar 20, a power supply 10 driving the LED lightbar 20 to display, and a constant current driving chip 30 controlling the power supply 10 and the LED lightbar 20. The constant current driving chip 30 includes an adjusting unit 32 that adjusts brightness of the LED lightbar 20. An input end of the adjusting unit 32 is connected with a cathode of the LED lightbar, and an output end of the adjusting unit 32 is coupled to a ground terminal of the LED backlight driving circuit through a resistor.
When any one of LED lamps of the LED lightbar 20 short-circuits, temperature of the constant current driving chip 30 increases, thus the affecting stability of an entire LED backlight driving circuit.
SUMMARY
The aim of the present disclosure is to provide a backlight driving circuit, a liquid crystal display (LCD) device, and a method for driving the backlight driving circuit capable of reducing power loss of a constant current driving chip and improving stability of an entire backlight driving circuit after any one of LED lamps of the LED lightbar short-circuits.
The aim of the present disclosure is achieved by the following method.
A backlight driving circuit comprises a light emitting diode (LED) lightbar, a power supply driving the LED lightbar, a constant current driving chip controlling the power supply and the LED lightbar, and a control unit monitoring a voltage of a cathode of the LED lightbar. The constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar. An input end of the adjusting unit is coupled to the cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, a resistance value of the load unit is adjusted.
When the voltage of the cathode of the LED lightbar is greater than or equal to a preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit.
Furthermore, the load unit comprises N resistors connected in parallel, and (N−1) resistors are connected with the controllable switches in series; when the voltage of the cathode of the LED lightbars is greater than or equal to the preset threshold, the control unit controls at least one controllable switch to turn on. N is a natural number that is greater than or equal to 2. This is specific circuit of the load unit using a plurality of resistors connected in parallel, and each of the resistors is controlled by the controllable switch. As a number of the controllable switch being on increases, the resistance value of the load unit reduces. Thus, when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls at least one controllable switch to turn on, which reduces the resistance value of the load unit.
Furthermore, the load unit comprises a first resistor and a second resistor that are connected in parallel. The second resistor is connected with a first controllable switch in series. When the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the first controllable switch to turn on. This is a method of using two connected-in-parallel resistors, where only one controllable switch needs to be controlled, and the control method is easy, development difficulty and hardware cost are reduced.
Furthermore, the control unit comprises a first comparator and a monitor unit. A first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit. When the voltage of the cathode of the LED lightbar is greater than or equal to the first reference voltage, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit. The first reference voltage is less than or equal to the preset threshold. The first comparator quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold. When the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator outputs the reserved voltage, namely the first comparator outputs a low level signal at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator outputs a high level signal. Thus, according to change of the output voltage of the first comparator, the monitor unit may determine whether the LED lamp is short-circuited, and further controls the load unit to reduce the resistance value of the load unit.
Furthermore, the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal. The adjusting assembly is coupled to the adjusting unit. When the voltage of the cathode of the LED lightbars is greater than or equal to the preset threshold, the adjusting assembly reduces the duty cycle of the PWM dimming signal. When the resistance value of the load unit reduces, current flowing through the LED lightbar increases, and brightness of the LED lightbar increases. In order to make brightness of the LED lightbar that is short-circuited be consistent with brightness of the LED lightbars that are not short-circuited, the adjusting assembly of the monitor unit outputs a PWM dimming signal having a small duty cycle to the adjusting unit of the constant current driving chip, which allows current of the LED lightbar that is short-circuited to be consistent with current of the LED lightbars that are not short-circuited.
Furthermore, the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch. The second controllable switch is connected in series between the cathode of the LED lightbar and the load unit. An output end of the adjusting assembly is coupled to a control end of the second controllable switch. This is a specific circuit of the adjusting unit using the second controllable switch to control effective current of the LED lightbar.
Furthermore, the load unit comprises a first resistor and a second resistor that are connected in parallel, where the second resistor is connected with a first controllable switch in series.
The control unit comprises a first comparator and a monitor unit. A first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit. The first reference voltage is less than or equal to the preset threshold.
The monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal. The adjusting assembly is coupled to the adjusting unit. The adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch. The second controllable switch is connected in series between the cathode of the LED lightbar and the load unit. An output end of the adjusting assembly is coupled to a control end of the second controllable switch.
When the voltage of the cathode of the LED lightbars is greater than or equal to the first reference voltage, the first comparator outputs a reserved voltage, and the control unit controls the first controllable switch to turn on, and simultaneously, the adjusting assembly reduces the duty cycle of the PWM dimming signal.
The load unit uses two connected-in-parallel resistors, first controllable switch is used to control the second resistor. When the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the first controllable switch to turn on, and current flows through the second resistor. Thus, the resistance value of the load unit is equal to the resistance value of two connected-in-parallel resistors, which is less than the first resistor (the first resistor is equal to the resistance value of the load unit when the first controllable switch turns off). The present disclosure uses a method of using two connected-in-parallel resistors, and only needs to control one controllable switch, thus the control method is easy, development difficulty and hardware cost are reduced.
The first comparator quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold. When the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator outputs the reserved voltage, namely the first comparator outputs a low level signal at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator outputs a high level signal. Thus, according to change of the output voltage of the first comparator, the monitor unit may determine whether the LED lamp is short-circuited, and further controls the load unit to reduce the resistance value of the load unit.
When the resistance value of the load unit reduces, current flowing through the LED lightbar increases and brightness of the LED lightbar increases. In order to make brightness of the LED lightbar that is short-circuited to be consistent with brightness of the LED lightbars that are not short-circuited, the adjusting assembly of the monitor unit outputs a PWM dimming signal having a small duty cycle to the adjusting unit of the constant current driving chip, which allows current flowing through the LED lightbar that is short-circuited to be consistent with current of the LED lightbars that are not short-circuited.
A light crystal display (LCD) device comprises a backlight driving circuit of the present disclosure.
A method for driving a backlight driving circuit. The backlight driving circuit comprises an LED lightbar, a power supply driving the LED lightbar, and a constant current driving chip controlling the power supply and the LED lightbar. The constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar, an input end of the adjusting unit is coupled to a cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, a resistance value of the load unit is adjusted. The method comprises:
A: setting a preset threshold; and
B: monitoring a voltage of the cathode of the LED lightbar; if the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, reducing the resistance value of the load unit. If the voltage of the cathode of the LED lightbar is less than the preset threshold, maintaining the resistance value of the load unit.
Furthermore, the step B comprises: when reducing the resistance value of the load unit, reducing a duty cycle of a driving signal of the adjusting unit, which allows effective current flowing through the LED lightbar that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited. When the resistance value of the load unit reduces, current flowing through the LED lightbar increases, and brightness of the LED lightbar increases. In order to make brightness of the LED lightbar that is short-circuited be consistent with brightness of the LED lightbars that are not short-circuited, the adjusting assembly of the monitor unit outputs a PWM dimming signal having a small duty cycle to the adjusting unit of the constant current driving chip, which allows current of the LED lightbar that is short-circuited to be consistent with current of the LED lightbars that are not short-circuited.
It should be understood that current is determined by a reference voltage V input to the adjusting unit and a resistance value R of a resistor connected in series between the adjusting unit and the ground terminal of the backlight driving circuit. An equation of current flowing through the LED lightbar is: I=V1/R (V1 is the voltage of the cathode of the LED lightbar). The adjusting unit controls the duty cycle of the current of the LED lightbar to adjust backlight brightness of the LED lightbar. A voltage Vo outputted by the power supply is relative to the current flowing through the LED lightbar, when the current flowing through the LED lightbar is great, the voltage Vo driving the LED lightbars is corresponding great. An equation of the voltage Vo is: Vo=Vin/(1−D), where Vin is an input voltage of the power supply, and D is a duty cycle of the power supply.
When any one LED lamps of the LED lightbar short-circuits, a redundant voltage of the cathode of the LED lightbar (about 6 V) is input to the adjusting unit, which results in increasing temperature of the constant current driving chip, thereby affecting stability of an entire backlight driving circuit. The present disclosure uses the control unit and the load unit, when one or more LED lamps of the LED lightbar short-circuit, the voltage of the cathode of the LED lightbar increases. Thus, the voltage of the cathode of the LED lightbar is regarded as the preset threshold when one or more LED lamps of the LED lightbars short-circuit. When the control unit monitors that the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit. According to the equation of I=V1/R, as the resistance value of the load unit reduces, the current flowing through the LED lightbar increases, the redundant voltage is uniformly assigned to remaining LED lamps that are not short-circuited, and the voltage of the cathode of the LED lightbar reduces, thus correspondingly reducing voltage of the adjusting unit and temperature of the constant current driving chip. Therefore, the present disclosure reduces power loss of the constant current driving chip and improves stability of the entire backlight driving circuit when the LED lamp short-circuits.
BRIEF DESCRIPTION OF FIGURES
FIG. 1 is a schematic diagram of a typical backlight driving circuit;
FIG. 2 is a schematic diagram of a backlight driving circuit of a first example of the present disclosure;
FIG. 3 is a schematic diagram of a backlight driving circuit of a second example of the present disclosure; and
FIG. 4 is a flowchart of a method for driving a backlight driving circuit of a third example of the present disclosure.
 DETAILED DESCRIPTION
The present disclosure provides a liquid crystal display (LCD) device comprising an LCD panel and a backlight unit. The backlight unit comprises a backlight driving circuit. The backlight driving circuit comprises a light emitting diode (LED) lightbar, a power supply driving the LED lightbar to display, and a constant current driving chip controlling the power supply and the LED lightbar. The constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar. An input end of the adjusting unit is coupled to a cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, where a resistance value of the load unit can be adjusted. The backlight driving circuit further comprises a control unit that monitors voltage of the cathode of the LED lightbar.
When the voltage of the cathode of the LED lightbar is greater than or equal to a preset threshold, the control unit controls the load unit to reduce a resistance value of the load unit.
It should be understood that current is determined by a reference voltage V input to the adjusting unit and a resistance value R of a resistor connected in series between the adjusting unit and a ground terminal of the backlight driving circuit. An equation of current flowing through the LED lightbar is: I=V1/R (V1 is the voltage of the cathode of the LED lightbar). The adjusting unit adjusts backlight brightness of the LED lightbar by controlling a duty cycle of the current flowing through the LED lightbar. A voltage Vo outputted by the power supply is relative to the current flowing through the LED lightbar, when the current flowing through the LED lightbar is great, the voltage Vo driving the LED lightbar is corresponding great. An equation of the voltage Vo is: Vo=Vin/(1−D), where Vin is an input voltage of the power supply, and D is a duty cycle of the power supply.
When any one of LED lamps of the LED lightbar short-circuits, a redundant voltage of the cathode of the LED lightbar (about 6 V) is input to the adjusting unit, which results in increasing temperature of the constant current driving chip, thereby affecting stability of an entire backlight driving circuit. The present disclosure uses the control unit and the load unit, when one or more LED lamps of the LED lightbar short-circuit, the voltage of the cathode of the LED lightbar increases. Thus the voltage of the cathode of the LED lightbar is regard as a preset threshold when one or more LED lamps of the LED lightbar short-circuit. When the control unit monitors that the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit. According to the equation of I=V1/R, as the resistance value of the load unit reduces, the current flowing through the LED lightbar increases, the redundant voltage is uniformly assigned to remaining LED lamps that are not short-circuited, and the voltage of the cathode of the LED lightbar reduces, thus correspondingly reducing voltage of the adjusting unit and temperature of the constant current driving chip. Therefore, the present disclosure reduces power loss of the constant current driving chip and improves stability of the entire backlight driving circuit when the LED lamp short-circuits.
The present disclosure is further described in detail in accordance with the figures and the exemplary examples.
Example 1
As shown in FIG. 2, a backlight driving circuit 1 of a first example comprises a light emitting diode (LED) lightbar 20, a power supply 10 driving the LED lightbar 20, and a constant current driving chip 30 controlling the power supply 10 and the LED lightbar 20. The constant current driving chip 30 comprises a main control unit 31 that drives the power supply, and an adjusting unit 32 that adjusts brightness of the LED lightbars 20. An input end of the adjusting unit 32 is coupled to a cathode of the LED lightbar 20, and an output end of the adjusting unit 32 is coupled to a load unit 40, a resistance value of the load unit 40 can be adjusted. The backlight driving circuit 1 further comprises a control unit 50 that monitors a voltage of the cathode of the LED lightbar. A plurality of the LED lightbars 20 are shown in FIG. 2. When the plurality of the LED lightbars 20 are arranged in the backlight driving circuit, a plurality of load units 40 and a plurality of control units 50 are correspondingly arranged in the backlight driving circuit and are used to control the plurality of LED lightbars 20; the first example only takes one LED lightbar, the load unit 40, and the control unit 50 for example to further describe the present disclosure, where the load unit 40 and the control unit 50 correspond to the one LED lightbar. It should be understood that each of the LED lightbars 20 corresponds to one load unit 40 and one control unit 50, structures of all units are same, and structures of all control units are same.
The load unit 40 comprises a first resistor R1 and a second resistor R2 that are connected in parallel. The second resistor R2 is connected with a first controllable switch Q1 in series. The control unit 50 comprises a first comparator OP1 and a monitor unit 51. The monitor unit 51 uses a microcontroller (MCU) or other control chips. A first reference voltage VF1 is input to a first input end of the first comparator OP1, a second input end of the first comparator OP1 is coupled to the cathode of the LED lightbar 20, and an output end of the first comparator OP1 is coupled to the monitor unit 51. When the voltage of the cathode of the LED lightbar 20 is greater than or equal to the first reference voltage VF1, the first comparator OP1 outputs a reserved voltage, the monitor unit 51 controls the first controllable switch Q1 to turn on. The first reference voltage VF1 is less than or equal to the preset threshold, the first reference voltage VF1 uses common voltage in the backlight driving circuit, such as 5V, 12V, and the like.
The load unit 40 uses two connected-in-parallel resistors, and the first controllable switch Q1 is used to control the second resistor R2. When the voltage of the cathode of the LED lightbar 20 is greater than or equal to the preset threshold (the first reference voltage VF1), the monitor unit 51 of the control unit 50 controls the first controllable switch Q1 to turn on, and current flows through the second resistor R2. Thus, the resistance value of the load unit 40 is equal to the resistance value of two connected-in-parallel resistors, which is less than the first resistor R1 (R1 is equal to the resistance value of the load unit 40 when the first controllable switch Q1 turns off).
The first comparator OP1 quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold. When the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP1 outputs the reserved voltage, namely the first comparator OP1 outputs a low level signal (logic 0) at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP1 outputs a high level signal (logic 1). Thus, according to change of the output voltage of the first comparator OP1, the monitor unit 51 may determine whether the LED lamp is short-circuited, and further controls the load unit to reduce the resistance value of the load unit.
The present disclosure uses a method of using two connected-in-parallel resistors, and only one controllable switch needs to be controlled, thus the control method is easy, development difficulty and hardware cost are reduced. The present disclosure should not be limited to use two connected-in-parallel resistors and may further use a plurality of resistors connected in parallel. Namely the load unit 40 comprises N resistors connected in parallel, where (N−1) resistors are connected with the controllable switches in series, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, as long as at least one controllable switch turns on, the resistance value of the load unit can be reduced. Thus, as a number of the controllable switch being on increases, the resistance value of the load unit reduces, where N is a natural number that is greater than or equal to 2.
Example 2
As shown in FIG. 3, a backlight driving circuit 1 of a second example comprises an LED lightbar 20, a power supply 10 driving the LED lightbar 20, and a constant current driving chip 30 controlling the power supply 10 and the LED lightbar 20. The constant current driving chip 30 comprises a main control unit 31 that drives the power supply, and an adjusting unit 32 that adjusts brightness of the LED lightbars 20. An input end of the adjusting unit 32 is coupled to a cathode of the LED lightbar 20, and an output end of the adjusting unit 32 is coupled to a load unit 40, where a resistance value of the load unit 40 can be adjusted. The backlight driving circuit 1 further comprises a control unit 50 that monitors a voltage of the cathode of the LED lightbar. A plurality of the LED lightbars 20 are shown in FIG. 3. When the plurality of the LED lightbars 20 are arranged in the backlight driving circuit, a plurality of load units 40 and a plurality of control units 50 are correspondingly arranged in the backlight driving circuit and are used to control the plurality of LED lightbars 20. The second example only takes one LED lightbar, the load unit 40, and the control unit 50 for example to further describe the present disclosure, where the load unit 40 and the control unit 50 correspond to the one LED lightbar. It should be understood that each of the LED lightbars 20 corresponds to one load unit 40 and one control unit 50, structures of all load units are same, and structures of all control units are same.
The load unit 40 comprises the first resistor R1 and the second resistor R2 that are connected in parallel. The second resistor R2 is connected with a first controllable switch Q1 in series.
The control unit 50 comprises a first comparator OP1 and a monitor unit 51. The monitor unit 51 uses a microcontroller (MCU) or other control chips. A first reference voltage VF1 is input to a first input end of the first comparator OP1, a second input end of the first comparator OP1 is coupled to the cathode of the LED lightbar 20, and an output end of the first comparator OP1 is coupled to the monitor unit 51. The first reference voltage VF1 is less than or equal to the preset threshold, the first reference voltage VF1 uses common voltage in the backlight driving circuit, such as 5V, 12V, and the like.
The monitor unit 51 comprises an adjusting assembly 52 which adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal. The adjusting assembly 52 is coupled to the adjusting unit 32. The adjusting unit 32 comprises a second controllable switch Q2 and a second comparator OP2 coupled to the second controllable switch Q2. A second reference voltage V2 is input to a non-inverting input end of the second comparator OP2, and an inverting input end of the second comparator OP2 is coupled to an output end of the second controllable switch Q2.
The second controllable switch Q2 is connected in series between the cathode of the LED lightbar 20 and the load unit 40. An output end of the adjusting assembly 52 is coupled to a control end of the second controllable switch Q2.
When the voltage of the cathode of the LED lightbar 20 is greater than or equal to the first reference voltage VF1, the first comparator OP1 outputs a reserved voltage. The monitor unit 51 controls the first controllable switch Q1 to turn on, in the meantime, the adjusting assembly 52 reduces the duty cycle of PWM dimming signal outputted by the adjusting assembly, which allows effective current flowing through the LED lightbar 20 that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
The load unit 40 uses two connected-in-parallel resistors, and the first controllable switch Q1 is used to control the second resistor R2. When the voltage of the cathode of the LED lightbar 20 is greater than or equal to the preset threshold, the control unit 50 controls the first controllable switch Q1 to turn on, and current flows through the second resistor R2. Thus, the resistance value of the load unit 40 is equal to the resistance value of two connected-in-parallel resistors, which is less than the first resistor R1 (R1 is equal to the resistance value of the load unit 40 when the first controllable switch Q1 turns off). The present disclosure uses a method of using two connected-in-parallel resistors, and only needs to control one controllable switch, thus the control method is easy, development difficulty and hardware cost are reduced.
The first comparator OP1 quickly determines whether the voltage of the cathode of the LED lightbar exceeds the preset threshold. When the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP1 outputs the reserved voltage, namely the first comparator OP1 outputs a low level signal (logic 0) at first, when the voltage of the cathode of the LED lightbar exceeds the preset threshold, the first comparator OP1 outputs a high level signal (logic 1). Thus, according to change of the output voltage of the first comparator OP1, the monitor unit 51 may determine whether the LED lamp is short-circuited, further controls the load unit to reduce the resistance value of the load unit.
When the resistance value of the load unit reduces, current flowing through the LED lightbar increases, the brightness of the LED lightbar increases. In order to make brightness of the LED lightbar 20 that is short-circuited be consistent with brightness of the LED lightbars that are not short-circuited, the adjusting assembly 52 of the monitor unit 51 outputs a PWM dimming signal having a small duty cycle to the adjusting unit 32 of the constant current driving chip 30, which allows current flowing through the LED lightbar 20 that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
The present disclosure uses a method of using two connected-in-parallel resistors, only needs to control one controllable switch, thus the control method is easy, development difficulty and hardware cost are reduced. The present disclosure should not be limited to use two connected-in-parallel resistors and may use a plurality of resistors connected in parallel. Namely the load unit 40 comprises N resistors connected in parallel, where (N−1) resistors are connected with the controllable switch in series, when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, as long as at least one controllable switch turns on, the resistance value of the load unit can be reduced. Thus, as a number of the controllable switch being on increases, the resistance value of the load unit reduces, where N is a natural number that is greater than or equal to 2.
Example 3
As shown in FIG. 4, the present disclosure provides a method for driving a backlight driving circuit, the backlight driving circuit comprises an LED lightbar, a power supply driving the LED lightbar, and a constant current driving chip controlling the power supply and the LED lightbar. The constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar. An input end of the adjusting unit is coupled to a cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, where a resistance value of the load unit can be adjusted. The method comprises:
A: setting a preset threshold; and
B: monitoring a voltage of the cathode of the LED lightbar; if the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, reducing the resistance value of the load unit. If the voltage of the cathode of the LED lightbar is less than the preset threshold, maintaining the resistance value of the load unit.
When the resistance value of the load unit reduces, current flowing through the LED lightbar increases, and brightness of the LED lightbar increases. In order to ensure brightness of the LED lightbar 20 that is short-circuited be consistent with brightness of the LED lightbars that are not short-circuited, the step B comprises: when reducing the resistance value of the load unit, reducing a duty cycle of a driving signal of the adjusting unit, which allows effective current flowing through the LED lightbar 20 that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
The controllable switch of the present disclosure uses semiconductor switch device such as a metal-oxide-semiconductor field-effect transistor (MOSFET). The present disclosure is described in detail in accordance with the above contents with the specific exemplary examples. However, this present disclosure is not limited to the specific examples. For the ordinary technical personnel of the technical field of the present disclosure, on the premise of keeping the conception of the present disclosure, the technical personnel can also make simple deductions or replacements, and all of which should be considered to belong to the protection scope of the present disclosure.

Claims (20)

We claim:
1. A backlight driving circuit, comprising:
a light emitting diode (LED) lightbar,
a power supply driving the LED lightbar;
a constant current driving chip controlling the power supply and the LED lightbar; and
a control unit monitoring voltage of a cathode of the LED lightbar;
wherein the constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar; an input end of the adjusting unit is coupled to the cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, a resistance value of the load unit is adjustable;
when the voltage of the cathode of the LED lightbar is greater than or equal to a preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit.
2. The backlight driving circuit of claim 1, wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit;
when the voltage of the cathode of the LED lightbar is greater than or equal to a preset threshold, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit; the first reference voltage is less than or equal to the preset threshold.
3. The backlight driving circuit of claim 2, wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal, and the adjusting assembly is coupled to the adjusting unit; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the adjusting assembly reduces the duty cycle of the PWM dimming signal.
4. The backlight driving circuit of claim 3, wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch.
5. The backlight driving circuit of claim 1, wherein the load unit comprises N resistors connected in parallel, and (N−1) resistors are connected with the controllable switches in series; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls at least one controllable switch to turn on; wherein N is a natural number that is greater than or equal to 2.
6. The backlight driving circuit of claim 5, wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit;
when the voltage of the cathode of the LED lightbars is greater than or equal to the preset threshold, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit; the first reference voltage is less than or equal to the preset threshold;
wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal; and the adjusting assembly is coupled to the adjusting unit; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the adjusting assembly reduces the duty cycle of the PWM dimming signal;
wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch.
7. The backlight driving circuit of claim 1, the load unit comprises a first resistor and a second resistor that are connected in parallel; the second resistor is connected with a first controllable switch in series; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the first controllable switch to turn on.
8. The backlight driving circuit of claim 7, wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit;
when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit; the first reference voltage is less than or equal to the preset threshold;
wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal, and the adjusting assembly is coupled to the adjusting unit; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the adjusting assembly reduces the duty cycle of the PWM dimming signal;
wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch.
9. The backlight driving circuit of claim 1, wherein the load unit comprises a first resistor and a second resistor that are connected in parallel; the second resistor is connected with a first controllable switch in series;
wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit; the first reference voltage is less than or equal to the preset threshold;
wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal, and the adjusting assembly is coupled to the adjusting unit;
wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch;
when the voltage of the cathode of the LED lightbar is greater than or equal to the first reference voltage, the first comparator outputs a reserved voltage, the control unit controls the first controllable switch to turn on, and simultaneously, the adjusting assembly reduces the duty cycle of the PWM dimming signal.
10. A light crystal display (LCD) device, comprising:
a backlight driving circuit;
wherein the backlight driving circuit comprises a light emitting diode (LED) lightbar, a power supply driving the LED lightbar, a constant current driving chip controlling the power supply and the LED lightbar, and a control unit monitoring a voltage of a cathode of the LED lightbar;
wherein constant current driving chip comprises a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar; an input end of the adjusting unit is coupled to the cathode of the LED lightbar, and an output end of the adjusting unit is coupled to a load unit, a resistance value of the load unit is adjusted;
when the voltage of the cathode of the LED lightbar is greater than or equal to a preset threshold, the control unit controls the load unit to reduce the resistance value of the load unit.
11. The LCD device of claim 10, wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit;
when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit; the first reference voltage is less than or equal to the preset threshold.
12. The LCD device of claim 10, wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal; and the adjusting assembly is coupled to the adjusting unit; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the adjusting assembly reduces the duty cycle of the PWM dimming signal.
13. The LCD device of claim 12, wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch.
14. The LCD device of claim 10, wherein the load unit comprises N resistors connected in parallel, and (N−1) resistors are connected with the controllable switches in series; when the voltage of the cathode of the LED lightbars is greater than or equal to the preset threshold, the control unit controls at least one controllable switch to turn on; wherein N is a natural number that is greater than or equal to 2.
15. The LCD device of claim 14, wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit;
when the voltage of the cathode of the LED lightbars is greater than or equal to the preset threshold, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit; the first reference voltage is less than or equal to the preset threshold;
wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal; and the adjusting assembly is coupled to the adjusting unit; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the adjusting assembly reduces the duty cycle of the PWM dimming signal;
wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch.
16. The LCD device of claim 10, wherein the load unit comprises a first resistor and a second resistor that are connected in parallel; the second resistor is connected with a first controllable switch in series; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the control unit controls the first controllable switch to turn on.
17. The LCD device of claim 16, wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit;
when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the first comparator outputs a reserved voltage, and the monitor unit controls the load unit to reduce the resistance value of the load unit; the first reference voltage is less than or equal to the preset threshold;
wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal, and the adjusting assembly is coupled to the adjusting unit; when the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, the adjusting assembly reduces the duty cycle of the PWM dimming signal;
wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch.
18. The LCD device of claim 10, wherein the load unit comprises a first resistor and a second resistor that are connected in parallel; the second resistor is connected with a first controllable switch in series;
wherein the control unit comprises a first comparator and a monitor unit; a first reference voltage is input to a first input end of the first comparator, a second input end of the first comparator is coupled to the cathode of the LED lightbar, and an output end of the first comparator is coupled to the monitor unit; the first reference voltage is less than or equal to the preset threshold;
wherein the monitor unit comprises an adjusting assembly that adjusts a duty cycle of a pulse-width modulation (PWM) dimming signal, and the adjusting assembly is coupled to the adjusting unit;
wherein the adjusting unit comprises a second controllable switch and a second comparator coupled to the second controllable switch; the second controllable switch is connected in series between the cathode of the LED lightbar and the load unit; an output end of the adjusting assembly is coupled to a control end of the second controllable switch;
when the voltage of the cathode of the LED lightbar is greater than or equal to the first reference voltage, the first comparator outputs a reserved voltage, the control unit controls the first controllable switch to turn on, and simultaneously, the adjusting assembly reduces the duty cycle of the PWM dimming signal.
19. A method for driving a backlight driving circuit, the backlight driving circuit comprising a light emitting diode (LED) lightbar, a power supply driving the LED lightbar, and a constant current driving chip controlling the power supply and the LED lightbar; the constant current driving chip comprising a main control unit that drives the power supply, and an adjusting unit that adjusts brightness of the LED lightbar; an input end of the adjusting unit being coupled to a cathode of the LED lightbar, an output end of the adjusting unit being coupled to a load unit, and a resistance value of the load unit being adjusted; the method comprising:
A: setting a preset threshold; and
B: monitoring a voltage of the cathode of the LED lightbar, if the voltage of the cathode of the LED lightbar is greater than or equal to the preset threshold, reducing the resistance value of the load unit; if the voltage of the cathode of the LED lightbar is less than the preset threshold, maintaining the resistance value of the load unit.
20. The method for driving the backlight driving circuit of claim 19, wherein the step B comprises:
when reducing the resistance value of the load unit, reducing a duty cycle of a driving signal of the adjusting unit, which allows effective current flowing through the LED lightbar that is short-circuited to be consistent with current flowing through the LED lightbars that are not short-circuited.
US13/984,530 2013-05-28 2013-06-27 Backlight driving circuit, LCD device, and method for driving the backlight driving circuit Expired - Fee Related US9271361B2 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CN201310203882.7A CN103280193B (en) 2013-05-28 2013-05-28 A kind of backlight drive circuit, liquid crystal indicator and backlight driving method
CN201310203882.7 2013-05-28
CN201310203882 2013-05-28
PCT/CN2013/078162 WO2014190577A1 (en) 2013-05-28 2013-06-27 Backlight driver circuit, liquid crystal display device, and backlight driving method

Publications (2)

Publication Number Publication Date
US20140354180A1 US20140354180A1 (en) 2014-12-04
US9271361B2 true US9271361B2 (en) 2016-02-23

Family

ID=51984360

Family Applications (1)

Application Number Title Priority Date Filing Date
US13/984,530 Expired - Fee Related US9271361B2 (en) 2013-05-28 2013-06-27 Backlight driving circuit, LCD device, and method for driving the backlight driving circuit

Country Status (1)

Country Link
US (1) US9271361B2 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130271701A1 (en) * 2012-04-12 2013-10-17 Xiang Yang LED Backlight Drive Circuit, Liquid Crystal Display Device and Driving Method
CN108811242A (en) * 2018-05-18 2018-11-13 青岛亿联客信息技术有限公司 A kind of integral control circuit and intelligent desk lamp

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9084321B2 (en) * 2013-07-15 2015-07-14 Shenzhen China Star Optoelectronics Technology Co., Ltd LED backlight system and display device
CN105592595B (en) * 2016-03-08 2017-06-27 深圳市华星光电技术有限公司 backlight dimming circuit and liquid crystal display
JP6982189B1 (en) * 2019-06-26 2021-12-17 ジィァンメン ポンジィァン ティェンリー ニュー テック カンパニー リミテッドJiangmen Pengjiang Tianli New Tech Co., Ltd Power line transmission Amplitude modulation signal-based processing method and LED module
CN110446308A (en) * 2019-09-04 2019-11-12 杭州必易微电子有限公司 For controlling control circuit, driving circuit, LED lamp system and the control method of power transistor
CN110996457B (en) * 2019-12-31 2023-05-23 惠州视维新技术有限公司 LED driving circuit, device, LED control protection method and storage medium
CN111146928B (en) * 2020-01-20 2024-06-21 深圳市毂梁源技术有限公司 Regulating circuit and BUCK circuit
CN117037729B (en) * 2023-10-08 2024-01-16 中科(深圳)无线半导体有限公司 Self-adaptive adjustment mini LED backlight driving method and driving chip thereof

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030025465A1 (en) 1999-12-23 2003-02-06 Stmicroelectronics, Inc. LED driver circuit and method
US20060175986A1 (en) * 2005-02-04 2006-08-10 Samsung Electro-Mechanics Co., Ltd. LED array driving apparatus and backlight driving apparatus using the same
US20070159736A1 (en) * 2006-01-12 2007-07-12 Denso Corporation Led-based lamp apparatus
CN101527120A (en) 2008-03-05 2009-09-09 三星电子株式会社 Method of driving a light source, light source device for performing the same, and display device having the light source device
CN102446492A (en) 2010-10-08 2012-05-09 联咏科技股份有限公司 Short-circuit sensing circuit and method, and driving chip and equipment of light emitting diode
CN102682719A (en) 2012-05-16 2012-09-19 深圳市华星光电技术有限公司 LED (Light Emitting Diode) backlight driving circuit, backlight module and liquid crystal display device
CN202551453U (en) 2012-04-20 2012-11-21 钰满荣企业股份有限公司 Constant-power light-emitting diode (LED) driving device
CN102881262A (en) 2012-09-28 2013-01-16 深圳Tcl新技术有限公司 LED backlight driving device, LED backlight driving method and LED backlight module
CN103107697A (en) 2013-01-22 2013-05-15 深圳市华星光电技术有限公司 Current regulating device and regulating method thereof
CN103117046A (en) 2013-03-11 2013-05-22 深圳市华星光电技术有限公司 Liquid crystal display, light-emitting diode (LED) backlight and driving method thereof

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030025465A1 (en) 1999-12-23 2003-02-06 Stmicroelectronics, Inc. LED driver circuit and method
US20060175986A1 (en) * 2005-02-04 2006-08-10 Samsung Electro-Mechanics Co., Ltd. LED array driving apparatus and backlight driving apparatus using the same
US20070159736A1 (en) * 2006-01-12 2007-07-12 Denso Corporation Led-based lamp apparatus
CN101527120A (en) 2008-03-05 2009-09-09 三星电子株式会社 Method of driving a light source, light source device for performing the same, and display device having the light source device
CN102446492A (en) 2010-10-08 2012-05-09 联咏科技股份有限公司 Short-circuit sensing circuit and method, and driving chip and equipment of light emitting diode
CN202551453U (en) 2012-04-20 2012-11-21 钰满荣企业股份有限公司 Constant-power light-emitting diode (LED) driving device
CN102682719A (en) 2012-05-16 2012-09-19 深圳市华星光电技术有限公司 LED (Light Emitting Diode) backlight driving circuit, backlight module and liquid crystal display device
CN102881262A (en) 2012-09-28 2013-01-16 深圳Tcl新技术有限公司 LED backlight driving device, LED backlight driving method and LED backlight module
CN103107697A (en) 2013-01-22 2013-05-15 深圳市华星光电技术有限公司 Current regulating device and regulating method thereof
CN103117046A (en) 2013-03-11 2013-05-22 深圳市华星光电技术有限公司 Liquid crystal display, light-emitting diode (LED) backlight and driving method thereof

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Ren Wenxin, the International Searching Authority written comments, Mar. 2014, CN.

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130271701A1 (en) * 2012-04-12 2013-10-17 Xiang Yang LED Backlight Drive Circuit, Liquid Crystal Display Device and Driving Method
US9426862B2 (en) * 2012-04-12 2016-08-23 Shenzhen China Star Optoelectronics Technology Co., Ltd. LED backlight drive circuit, liquid crystal display device and driving method
CN108811242A (en) * 2018-05-18 2018-11-13 青岛亿联客信息技术有限公司 A kind of integral control circuit and intelligent desk lamp

Also Published As

Publication number Publication date
US20140354180A1 (en) 2014-12-04

Similar Documents

Publication Publication Date Title
US9271361B2 (en) Backlight driving circuit, LCD device, and method for driving the backlight driving circuit
US9183788B2 (en) Backlight driving circuit, LCD device, and method for driving the backlight driving circuit
US9672779B2 (en) Liquid crystal display device, backlight module, and drive circuit for backlight source thereof
US9241377B2 (en) LED backlight driving circuit, LCD device, and method for driving the LED backlight driving circuit
US8686653B2 (en) LED backlight driving method, liquid crystal display device and LED backlight driving circuit
US9001109B2 (en) LED backlight driving circuit, backlight module, and LCD device
WO2014190577A1 (en) Backlight driver circuit, liquid crystal display device, and backlight driving method
RU2621883C1 (en) Led-backlight system and display device
US9258862B2 (en) LED backlight driving circuit, LCD device, and method for driving the LED backlight driving circuit
US20150156846A1 (en) Over-current protection circuit, led backlight driving circuit and liquid crystal device
US9232589B2 (en) LED backlight driving circuit and method for driving the LED backlight driving circuit
US8890417B2 (en) LED backlight driving circuit, backlight module, and LCD device
US9257078B2 (en) LED backlight driving circuit having divider units and method for driving the LED backlight driving circuit
GB2531192A (en) LED backlight and liquid crystal display
WO2014079038A1 (en) Led backlight drive circuit, backlight module and liquid crystal display apparatus
US9058776B2 (en) LED backlight source and liquid crystal device
GB2541612A (en) LED backlight drive circuit and liquid crystal display
US8912731B2 (en) LED backlight driving circuit and backlight module
US9018859B2 (en) LED backlight driving circuit and LCD device
US20130307878A1 (en) LED Backlight Driving Circuit, Backlight Module, and LCD Device
US8803440B2 (en) LED backlight driving circuit and LCD device
US9373284B2 (en) LED backlight driving circuit, LCD device, and method for driving the LED backlight driving circuit
US20130271500A1 (en) LED Backlight Driving Circuit, Backlight Module, and LCD Device
US9196202B2 (en) LED backlight driving circuit, LCD device, and method for driving the LED backlight driving circuit
US20140265925A1 (en) Led backlight driving circuit, lcd device, and method for driving the led backlight drving circuit

Legal Events

Date Code Title Description
AS Assignment

Owner name: SHENZHEN CHINA STAR OPTOELECTRONICS TECHNOLOGY CO.

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ZHANG, HUA;LI, FEI;REEL/FRAME:030994/0092

Effective date: 20130730

ZAAA Notice of allowance and fees due

Free format text: ORIGINAL CODE: NOA

ZAAB Notice of allowance mailed

Free format text: ORIGINAL CODE: MN/=.

STCF Information on status: patent grant

Free format text: PATENTED CASE

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Year of fee payment: 4

FEPP Fee payment procedure

Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

LAPS Lapse for failure to pay maintenance fees

Free format text: PATENT EXPIRED FOR FAILURE TO PAY MAINTENANCE FEES (ORIGINAL EVENT CODE: EXP.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

STCH Information on status: patent discontinuation

Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362

FP Lapsed due to failure to pay maintenance fee

Effective date: 20240223