WO2014187005A1 - 一种背光驱动电路、液晶显示装置和背光驱动方法 - Google Patents

一种背光驱动电路、液晶显示装置和背光驱动方法 Download PDF

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Publication number
WO2014187005A1
WO2014187005A1 PCT/CN2013/078153 CN2013078153W WO2014187005A1 WO 2014187005 A1 WO2014187005 A1 WO 2014187005A1 CN 2013078153 W CN2013078153 W CN 2013078153W WO 2014187005 A1 WO2014187005 A1 WO 2014187005A1
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WO
WIPO (PCT)
Prior art keywords
coupled
resistor
voltage
driving circuit
backlight driving
Prior art date
Application number
PCT/CN2013/078153
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English (en)
French (fr)
Inventor
张华�
黎飞
Original Assignee
深圳市华星光电技术有限公司
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Publication date
Application filed by 深圳市华星光电技术有限公司 filed Critical 深圳市华星光电技术有限公司
Priority to US13/981,335 priority Critical patent/US9183788B2/en
Publication of WO2014187005A1 publication Critical patent/WO2014187005A1/zh

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Classifications

    • 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
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/021—Power management, e.g. power saving
    • 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
    • G09G2330/12—Test circuits or failure detection circuits included in a display system, as permanent part thereof

Definitions

  • the present invention relates to the field of liquid crystal display, and more particularly to a backlight driving circuit, a liquid crystal display device, and a backlight driving method.
  • the liquid crystal display device includes a liquid crystal panel and a backlight module, and the backlight module includes an LED backlight driving circuit.
  • the LED backlight driving circuit includes an LED light bar 30, a power module 10 for driving the LED light bar, the power module is controlled by the constant current driving chip 20, and the constant current driving chip 20 receives an external PWM dimming signal. Controls the effective current flowing through the LED strip, which in turn affects the brightness of the LED strip.
  • the constant current driving chip 20 outputs a driving signal to the MOS transistor of the power module.
  • the MOS transistor When the MOS transistor is turned on, the inductor stores energy. When the MOS transistor is turned off, the inductor releases energy and provides a high voltage to the LED strip.
  • the output voltage Vo Vin/(l-D), D is the duty cycle of the drive waveform.
  • the power loss on the MOS transistor is related to the frequency of the drive signal and the length of the conduction time per unit period.
  • the technical problem to be solved by the present invention is to provide a backlight driving circuit, a liquid crystal display device and a backlight driving method for improving the conversion efficiency of a power module.
  • a backlight driving circuit includes a constant current driving chip, a power module, and an LED strip coupled with the power module, the constant current driving chip includes a control module for controlling a switching frequency of the power module, and adjusting an effective current flowing through the LED strip Air ratio detection module; the control module is provided for setting a power module a frequency pin of a switching frequency, the detecting module is coupled to an external PWM dimming signal; the backlight driving circuit further includes a detecting module for acquiring a duty ratio of the PWM dimming signal, and a monitoring module coupled with the detecting module,
  • the monitoring module When the duty cycle of the PWM dimming signal is lower than a preset threshold, the monitoring module outputs a signal of the down frequency to the frequency pin.
  • the detecting module includes a voltage dividing resistor and a photoresistor adjacent to the LED strip, the photo resistor is connected to a high-level reference voltage at one end, and the other end is connected to the ground end of the backlight driving circuit through a voltage dividing resistor.
  • the voltage across the voltage divider resistor is fed back to the monitoring module.
  • the monitoring module can determine whether the duty cycle of the PWM dimming signal is lower than a preset according to the voltage change across the voltage dividing resistor. Threshold.
  • the monitoring module includes a comparator and a first controllable switch; a first resistor and a second resistor are serially connected between the frequency pin and the ground end of the backlight driving circuit, and the first controllable switch is
  • the second resistors are arranged in parallel, the opposite input of the comparator is connected with a comparison voltage, and the non-inverting input is coupled to one end of the voltage dividing resistor connected to the photoresistor.
  • the frequency of the driving signal of the constant current driving chip control power module is related to the resistance value of the frequency pin connected. The larger the resistance value is, the smaller the frequency of the driving signal is. Conversely, the higher the frequency, the opposite end of the comparator is connected.
  • the voltage of the comparison voltage is equal to the voltage across the voltage dividing resistor corresponding to the preset threshold.
  • the comparator When the duty ratio of the PWM dimming signal is lower than the preset threshold, the comparator outputs a low level signal, and the first controllable switch is off.
  • the resistance value of the frequency pin connection is equal to the sum of the resistance values of the first resistor and the second resistor; the driving frequency of the output of the control module is reduced, and the power mode is lowered.
  • Block switching loss When the duty ratio of the PWM dimming signal exceeds a preset threshold, the comparator outputs a high level signal, the first controllable switch is turned on, and the resistance of the frequency pin is equal to the resistance of the first resistor Value; The drive frequency of the control module output increases, reducing the conduction loss of the power module.
  • a photosensitive resistor is connected in series between the frequency pin and the ground of the backlight driving circuit, and the photoresistor is disposed at a position where the LED strip can be directly irradiated.
  • the duty ratio of the PWM dimming signal is increased, and the brightness of the LED strip is increased; conversely, the brightness of the LED strip is reduced.
  • the technical scheme captures the change of the brightness of the LED light bar through the photoresistor. Under the premise that the resistance of the reference voltage and the voltage divider resistance is constant, when the duty ratio of the PWM dimming signal is large, the average current of the LED is large, and the brightness of the LED is high.
  • the resistance of the photoresistor is small, and the resistance of the photoresistor increases.
  • the frequency of the drive signal of the constant current drive chip control power module is related to the resistance value of the resistor connected to the frequency pin. The larger the resistance value, the smaller the frequency of the drive signal; Conversely, the frequency is higher.
  • the photoresistor just set the photoresistor to the place where the light emitted by the LED strip can be directly irradiated, and then feed back the resistance value to the frequency pin, so that as the brightness decreases, the output frequency of the control module will gradually decrease, and decrease at a low level.
  • the switching loss at the time of loading improves the conversion efficiency of the backlight driving circuit.
  • the technical solution only needs to adopt a photoresistor to realize the functions of the detection module and the monitoring module at the same time, the cost is low, and the control module driving frequency can be continuously adjusted, thereby improving the control precision.
  • the detecting module includes a filter resistor and a filter capacitor;
  • the monitoring module includes a comparator and a first controllable switch; and the first resistor and the first phase are connected in series between the frequency pin and the ground end of the backlight driving circuit a second resistor, the first controllable switch is disposed in parallel with the second resistor, a reverse voltage input of the comparator is connected with a comparison voltage, and the PWM dimming signal is connected to a reverse input of the comparator through a filter resistor
  • the filter capacitor is connected in series between the inverting input of the comparator and the ground of the LED backlight driving circuit.
  • the technical scheme uses an RC filter to convert a high-frequency varying PWM dimming signal into a flat voltage signal, and converts a rectangular wave PWM dimming signal into a smooth DC voltage signal, and different duty ratios correspond to different values of DC voltage. signal. Therefore, the equivalent voltage of the PWM dimming signal corresponding to the preset threshold can be compared, and compared with the voltage of the filtered PWM dimming signal, it can be determined whether the duty ratio of the PWM dimming signal exceeds the threshold.
  • This technical solution will account for the load Comparing the ratio of the air ratio to the voltage of the single tube, the technical difficulty is reduced, which is conducive to improving the development progress and reducing the development cost.
  • the detecting module includes a voltage dividing resistor and a photoresistor adjacent to the LED strip, the one end of the photoresistor is connected to a high level reference voltage through a voltage dividing resistor, and the other end is connected to a ground end of the backlight driving circuit;
  • the monitoring module includes a comparator and a first controllable switch; a first resistor and a second resistor are connected in series between the frequency pin and the ground of the backlight driving circuit, and the first controllable switch and the first The two resistors are arranged in parallel, the comparator input has a comparison voltage connected thereto, and the inverting input terminal is coupled to one end of the voltage dividing resistor connected to the photoresistor.
  • the duty ratio of the PWM dimming signal is increased, and the brightness of the LED strip is increased; on the contrary, the brightness of the LED strip is reduced.
  • the technical scheme captures the change of the brightness of the LED light bar through the photoresistor. Under the premise that the resistance of the reference voltage and the voltage divider resistance is constant, when the duty ratio of the PWM dimming signal is large, the average current of the LED is large, and the brightness of the LED is high. The resistance of the photoresistor is small; on the contrary, the resistance of the photoresistor increases.
  • the monitoring module can determine whether the duty cycle of the PWM dimming signal is lower than a preset threshold according to the voltage change across the photoresistor.
  • the technical solution only needs two resistors to convert the complex PWM duty cycle signal acquisition into the voltage level of the single tube, and the implementation method is simple, and the cost is low.
  • the frequency of the driving signal of the constant current driving chip control power module is related to the resistance value of the frequency pin connected. The larger the resistance is, the smaller the frequency of the driving signal is. Conversely, the higher the frequency, the same end of the comparator is connected.
  • the voltage of the comparison voltage is equal to the voltage across the voltage dividing resistor corresponding to the preset threshold. When the duty ratio of the PWM dimming signal is lower than the preset threshold, the comparator outputs a low level signal, and the first controllable switch is off.
  • the resistance value of the frequency pin connection is equal to the sum of the resistance values of the first resistor and the second resistor; the driving frequency of the control module output is reduced, and the switching loss of the power module is reduced; when the duty ratio of the PWM dimming signal exceeds the preset When the threshold value is reached, the comparator outputs a high level signal, the first controllable switch is turned on, and the resistance value of the frequency pin connection is equal to the resistance value of the first resistor; the driving frequency of the control module output is increased, and the power supply is lowered. The conduction loss of the module.
  • the power module includes an inductor, a diode, a voltage-regulating controllable switch, and a capacitor; one end of the inductor is coupled to an external input voltage, the other end is coupled to the anode of the diode, and is coupled to the backlight driving circuit through a voltage-regulated controllable switch. a ground terminal; a cathode of the diode coupled to a positive pole of the LED strip; and capacitively coupled to the ground; the voltage controlled switch is coupled to the control module.
  • This is a power module that uses a boost circuit.
  • the detecting module includes a dimming controllable switch, and an input end of the dimming controllable switch is coupled to a negative pole of the LED light bar; an output end thereof is coupled to a ground end of the LED backlight driving circuit through a current limiting resistor
  • the PWM dimming signal is coupled to the control terminal of the dimmable controllable switch.
  • the power module includes an inductor, a diode, a voltage-regulating controllable switch, and a capacitor; one end of the inductor is coupled to an external input voltage, the other end is coupled to the anode of the diode, and is coupled to the backlight driving circuit through a voltage-regulated controllable switch.
  • the voltage-regulated controllable switch coupled to the control module; a light controllable switch, the input end of the dimmable controllable switch is coupled to the negative pole of the LED strip; the output end is coupled to the ground of the LED backlight drive circuit via a current limiting resistor; the PWM dimming signal is coupled to the The control end of the dimmable controllable switch;
  • the detecting module comprises a voltage dividing resistor and a photoresistor adjacent to the LED strip, the photo resistor is connected with a high level reference voltage at one end, and the other end is connected to the ground end of the backlight driving circuit through a voltage dividing resistor;
  • the monitoring module a comparator, a first controllable switch; a first resistor and a second resistor are connected in series between the frequency pin and the ground of the backlight driving circuit, and the first controllable switch is arranged in parallel with the second resistor
  • the opposite input of the comparator is connected with a comparison voltage, and the non-inverting input is coupled to one end of the voltage dividing resistor connected to the photoresistor.
  • a liquid crystal display device comprising the backlight driving circuit of the present invention.
  • a driving method of a backlight driving circuit comprises a power module controlled by a switching frequency, an LED light bar coupled with the power module, and an effective current duty ratio for adjusting the flow through the LED light bar
  • the detecting module is coupled to the external PWM dimming signal; the driving method comprises the steps of:
  • the invention adds a detection module and a monitoring module.
  • the threshold of the duty ratio of the PWM dimming signal is preset; the detecting module monitors the duty ratio information of the PWM dimming signal in real time, and if the duty ratio of the PWM dimming signal is lower than a preset threshold, the switching frequency of the power module is lowered. On the contrary, maintain the status quo. In this way, the switching frequency can be reduced when the average value of the current of the LED strip is reduced, thereby reducing the switching loss; and improving the conversion efficiency of the power module.
  • FIG. 1 is a schematic diagram of a conventional backlight driving circuit
  • FIG. 2 is a schematic diagram of the principle of a backlight driving circuit according to an embodiment of the present invention.
  • FIG. 3 is a schematic diagram of the principle of a backlight driving circuit according to Embodiment 2 of the present invention.
  • FIG. 4 is a schematic diagram of the principle of a backlight driving circuit according to Embodiment 3 of the present invention.
  • FIG. 5 is a schematic diagram of the principle of a backlight driving circuit according to Embodiment 4 of the present invention.
  • FIG. 6 is a schematic diagram of a driving method of a backlight driving circuit according to Embodiment 5 of the present invention.
  • the invention discloses a liquid crystal display device.
  • the liquid crystal display device comprises a liquid crystal panel and a backlight module, and the backlight module comprises a backlight driving circuit.
  • the backlight driving circuit comprises a constant current driving chip, a power module, and an LED light bar coupled with the power module, and the constant current driving chip comprises a control module for controlling a switching frequency of the power module.
  • a detection module for adjusting an effective current duty ratio of the LED light bar;
  • the control module is provided with a frequency pin for setting a switching frequency of the power module, and the detection module is coupled to an external PWM dimming signal;
  • the backlight driving circuit further includes collecting A detection module for the duty cycle of the PWM dimming signal, and a monitoring module coupled to the detection module. When the duty cycle of the PWM dimming signal is lower than a preset threshold, the monitoring module outputs a signal of the frequency down to the frequency pin.
  • the invention adds a detection module and a monitoring module.
  • the threshold of the duty ratio of the PWM dimming signal is preset; the detecting module monitors the duty ratio information of the PWM dimming signal in real time, and if the duty ratio of the PWM dimming signal is lower than a preset threshold, the switching frequency of the power module is lowered. On the contrary, maintain the status quo. In this way, the switching frequency can be reduced when the average value of the current of the LED strip is reduced, thereby reducing the switching loss; and improving the conversion efficiency of the power module.
  • the backlight driving circuit 1 includes a constant current driving chip 20, a power module 10, and an LED strip 30 coupled to the power module 10.
  • the constant current driving chip 20 includes a control module 21 for controlling the switching frequency of the power module 10, and
  • the detection module 23 is configured to adjust the effective current duty ratio of the LED light bar 30;
  • the control module 21 is provided with a frequency pin 22 for setting the switching frequency of the power module 10, and the detection module 23 is coupled to the external PWM dimming signal;
  • the driving circuit further includes a detecting module 40 that collects the duty ratio of the PWM dimming signal, and a monitoring module 50 coupled to the detecting module 40.
  • the monitoring module 5050 When the duty cycle of the PWM dimming signal is below a predetermined threshold, the monitoring module 5050 outputs a signal of the down frequency to the frequency pin 22.
  • the power module 10 includes an inductor diode D, a voltage-regulating controllable switch Q2, and a capacitor C.
  • One end of the inductor L is coupled to an external input voltage, and the other end is coupled to the anode of the diode D, and coupled to the backlight driving circuit through the voltage-regulating controllable switch Q2.
  • a ground terminal a cathode of the diode D is coupled to the anode of the LED strip 30; And coupled to the ground through the capacitor C; the voltage controllable switch Q2 is coupled to the control module 21; the detection module 23 includes a dimmable controllable switch Q3, the input of the dimmable controllable switch Q3 is coupled to the negative pole of the LED strip 30 The output terminal is coupled to the ground terminal of the LED backlight driving circuit through a current limiting resistor R5; the PWM dimming signal is coupled to the control terminal of the dimmable controllable switch Q3.
  • the detecting module 40 includes a voltage dividing resistor R4 and a photoresistor R3 adjacent to the LED strip 30.
  • the photo resistor R3 is connected to a reference voltage of a high level (logic 1 ), and the other end is connected to the backlight driving circuit through a voltage dividing resistor R4. Ground terminal.
  • the reference voltage can be a stable high level voltage present in the circuit, such as 10V, 12V, 5V and other common voltages.
  • the monitoring module 50 includes a comparator ⁇ 1, a first controllable switch Q1; a first resistor RT1 and a second resistor RT2 are connected in series between the frequency pin 22 and the ground of the backlight driving circuit, and the first controllable switch Q1 and the second
  • the resistor RT2 is arranged in parallel, the opposite input of the comparator OP1 is connected with a comparison voltage VF, and the same input terminal is coupled to one end of the voltage dividing resistor R4 connected to the photoresistor R3.
  • the monitoring module 50 can determine whether the duty ratio of the PWM dimming signal is lower than the voltage of the voltage across the voltage dividing resistor R4.
  • the preset threshold The technical solution only needs two resistors to convert the complex PWM duty cycle signal acquisition into the voltage level of the single tube, and the implementation method is simple, and the cost is low.
  • the constant current driving chip 20 controls the frequency of the driving signal of the power module 10 to be related to the resistance value of the frequency pin 22, and the larger the resistance value, the smaller the frequency of the driving signal; conversely, the higher the frequency, the comparator OP1
  • the comparison voltage VF of the reverse terminal connection is equal to the voltage across the voltage dividing resistor R4 corresponding to the preset threshold.
  • the comparator OP1 outputs a low level ( Logic 0) signal, the first controllable switch Q1 is turned off, the resistance of the frequency pin 22 is connected, etc.
  • the backlight driving circuit includes a constant current driving chip 20, a power module 10, and an LED strip 30 coupled to the power module 10.
  • the constant current driving chip 20 includes a control module 21 for controlling the switching frequency of the power module 10, and an adjustment.
  • the detection module 23 flows through the LED light bar 30 effective current duty ratio; the control module 21 is provided with a frequency pin 22 for setting the switching frequency of the power module 10, the detection module 23 is coupled to an external PWM dimming signal;
  • the circuit also includes a detection module 40 that acquires the duty cycle of the PWM dimming signal, and a monitoring module 50 coupled to the detection module 40.
  • the monitoring module 50 When the duty cycle of the PWM dimming signal is below a predetermined threshold, the monitoring module 50 outputs a signal of the down frequency to the frequency pin 22.
  • the power module 10 includes an inductor diode D, a voltage-regulating controllable switch Q2, and a capacitor C.
  • One end of the inductor L is coupled to an external input voltage, and the other end is coupled to the anode of the diode D, and coupled to the backlight driving circuit through the voltage-regulating controllable switch Q2.
  • the ground terminal; the cathode of the diode D is coupled to the anode of the LED strip 30; and is coupled to the ground through a capacitor C; the voltage-controlled switch Q2 is coupled to the control module 21; the detection module 23 includes a dimmable controllable switch Q3, The input end of the optically controllable switch Q3 is coupled to the negative pole of the LED strip 30; the output is coupled to the ground of the LED backlight drive circuit via a current limiting resistor R5; the PWM dimming signal is coupled to the control of the dimmable controllable switch Q3 end.
  • the detecting module 40 includes a voltage dividing resistor R4 and a photoresistor R3 adjacent to the LED strip 30.
  • the photo resistor R3 is connected to a high level reference voltage through a voltage dividing resistor R4, and the other end is connected to a ground terminal of the backlight driving circuit.
  • the reference voltage can be a stable high level voltage present in the circuit, such as 10V, 12V, 5V and other common voltages.
  • the monitoring module 50 includes a comparator ⁇ 1, a first controllable switch Q1, a frequency pin 22 and a backlight drive
  • a first resistor RT1 and a second resistor RT2 are connected in series between the grounding ends of the circuit, and the first controllable switch Q1 and the second resistor RT2 are arranged in parallel, and the comparator input terminal of the comparator OP1 is connected with a comparison voltage VF, and the reverse input The terminal is coupled to a voltage dividing resistor R4 connected to one end of the photoresistor R3.
  • the monitoring module 50 can determine whether the duty ratio of the PWM dimming signal is lower than the preset according to the voltage change across the photoresistor R3. Threshold.
  • the technical solution only needs two resistors to convert the complex PWM duty cycle signal acquisition into the voltage level of the single tube, and the implementation method is simple, and the cost is low.
  • the constant current driving chip 20 controls the frequency of the driving signal of the power module 10 to be related to the resistance value of the frequency pin 22, and the larger the resistance value, the smaller the frequency of the driving signal; conversely, the higher the frequency, the comparator OP1
  • the voltage of the comparison voltage VF connected to the same end is equal to the voltage across the voltage dividing resistor R4 corresponding to the preset threshold.
  • the comparator OP1 outputs a low level signal.
  • the first controllable switch Q1 is turned off, and the resistance value of the frequency pin 22 is equal to the sum of the resistances of the first resistor RT1 and the second resistor RT2; the driving frequency outputted by the control module 21 is reduced, and the switching loss of the power module 10 is reduced.
  • the comparator OP1 outputs a high level signal, the first controllable switch Q1 is turned on, and the resistance of the frequency pin 22 is equal to the first resistor RT1.
  • the resistance value of the control module 21 is increased, and the conduction loss of the power module 10 is reduced.
  • the detecting module 40 of the present embodiment includes a filter resistor R Q and a filter capacitor C Q ;
  • the monitoring module 50 includes a comparator ⁇ 1, a first controllable switch Q1, a frequency pin 22, and a ground terminal of the backlight driving circuit.
  • a first resistor RT1 and a second resistor RT2 are connected in series, and the first controllable switch Q1 and the second resistor are connected in series RT2 is set in parallel.
  • the opposite input of comparator OP1 is connected with a comparison voltage VF, and the PWM dimming signal passes through the filter resistor R.
  • the detection module 40 of the present embodiment uses an RC filter to convert a high frequency variable PWM dimming signal into a flat voltage signal, and converts a rectangular wave PWM dimming signal into a smooth DC voltage signal, and different duty ratios are different. Numerical DC voltage signal. Therefore, the equivalent voltage of the PWM dimming signal corresponding to the preset threshold can be compared, and compared with the voltage of the filtered PWM dimming signal, it can be determined whether the duty ratio of the PWM dimming signal exceeds the threshold.
  • the technical solution compares the duty ratio of the load into a voltage comparison of the single tube, which reduces the technical difficulty, and is beneficial to improving the development progress and reducing the research and development cost.
  • a photoresistor R3 is connected in series between the frequency pin 22 of the constant current driving chip 20 and the ground terminal of the backlight driving circuit, and the photoresistor R3 is disposed at a position where the LED strip 30 can be directly irradiated.
  • the duty ratio of the PWM dimming signal is increased, and the brightness of the LED strip is increased; conversely, the brightness of the LED strip is reduced.
  • the technical scheme captures the change of the brightness of the LED light bar through the photoresistor. Under the premise that the resistance of the reference voltage and the voltage divider resistance is constant, when the duty ratio of the PWM dimming signal is large, the average current of the LED is large, and the brightness of the LED is high.
  • the resistance of the photoresistor is small, and the resistance of the photoresistor increases.
  • the frequency of the drive signal of the constant current drive chip control power module is related to the resistance value of the resistor connected to the frequency pin. The larger the resistance value, the smaller the frequency of the drive signal; Conversely, the frequency is higher.
  • the photoresistor just set the photoresistor to the place where the light emitted by the LED strip can be directly irradiated, and then feed back the resistance value to the frequency pin, so that as the brightness decreases, the output frequency of the control module will gradually decrease, and decrease at a low level.
  • the switching loss at the time of loading improves the conversion efficiency of the backlight driving circuit.
  • the technical solution only needs to adopt a photoresistor to realize the functions of the detection module and the monitoring module at the same time, the cost is low, and the control module driving frequency can be continuously adjusted, thereby improving the control precision.
  • the present invention also discloses a driving method of a backlight driving circuit, and a backlight driving circuit.
  • the utility model comprises a power module controlled by a switching frequency, an LED light bar coupled with the power module, a detecting module for adjusting an effective current duty ratio of the LED light bar, a detecting module coupled to the external PWM dimming signal, and a driving method comprising the steps :

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Abstract

一种背光驱动电路，包括恒流驱动芯片（20）、电源模块（10）、与电源模块（10）耦合的LED灯条（30），恒流驱动芯片（20）包括控制电源模块（10）开关频率的控制模块（21），以及调节流经LED灯条（30）有效电流占空比的侦测模块（23）；控制模块（21）设有用于设置电源模块（10）开关频率的频率引脚（22），侦测模块（23）耦合到外部的PWM调光信号；背光驱动电路还包括采集PWM调光信号占空比的检测模块（40），与检测模块（40）耦合的监控模块（50）。当PWM调光信号的占空比低于预设的阈值时，监控模块（50）输出调低频率的信号到频率引脚（22）。

Description

一种背光驱动电路、 液晶显示装置和背光驱动方法
【技术领域】
本发明涉及液晶显示领域， 更具体的说， 涉及一种背光驱动电路、 液晶显 示装置和背光驱动方法。
【背景技术】
液晶显示装置包括液晶面板和背光模组， 所述背光模组包括 LED背光驱动 电路。 如图 1所示， LED背光驱动电路包括 LED灯条 30, 驱动 LED灯条的电 源模块 10, 电源模块通过恒流驱动芯片 20进行控制， 恒流驱动芯片 20接收外 部的 PWM调光信号， 用于控制流经 LED灯条的有效电流， 进而影响 LED灯条 的亮度。
恒流驱动芯片 20输出驱动信号给电源模块的 MOS管， MOS管导通时， 电 感储能， MOS管关断时， 电感释放能量， 给 LED灯条提供高电压。 输出电压 Vo=Vin/(l-D), D 为驱动波形的占空比， MOS 管上的功率损耗与驱动信号的频 率大小以及单位周期内的导通时间长短有关。 驱动频率越大， MOS管上的开关 损耗越大， 但是单位周期内的导通时间短， MOS管上的导通损耗小； 驱动频率 越小， MOS管上的开关损耗越小， 但是单位周期内的导通时间长， MOS管上的 导通损耗大。
【发明内容】
本发明所要解决的技术问题是提供一种提高电源模块转换效率的背光驱动 电路、 液晶显示装置和背光驱动方法。
本发明的目的是通过以下技术方案来实现的：
一种背光驱动电路， 包括恒流驱动芯片、 电源模块、与电源模块耦合的 LED 灯条， 所述恒流驱动芯片包括控制电源模块开关频率的控制模块， 以及调节流 经 LED灯条有效电流占空比的侦测模块； 所述控制模块设有用于设置电源模块 开关频率的频率引脚，所述侦测模块耦合到外部的 PWM调光信号；所述背光驱 动电路还包括采集 PWM调光信号占空比的检测模块，与检测模块耦合的监控模 块，
当所述 PWM调光信号的占空比低于预设的阈值时，所述监控模块输出调低 频率的信号到所述频率引脚。
进一步的， 所述检测模块包括分压电阻和邻近 LED灯条的光敏电阻， 所述 光敏电阻一端连有高电平的基准电压， 另一端通过分压电阻连接到背光驱动电 路的接地端， 所述分压电阻两端的电压反馈到所述监控模块。 此为一种具体的 检测模块的电路。 经研究， PWM调光信号的占空比提高， LED灯条的亮度随之 增加； 反之， LED灯条的亮度减小。 本技术方案通过光敏电阻来捕捉 LED灯条 亮度的变化，在基准电压和分压电阻阻值不变的前提下， 当 PWM调光信号的占 空比较大时， LED平均电流大， 发光亮度高， 光敏电阻阻值小， 这样分压电阻 两端的电压就会增加； 反之， 分压电阻两端的电压就会降低。 只要将 PWM调光 信号的占空比和分压电阻两端的电压建立映射关系， 监控模块就可以根据分压 电阻两端电压的变化来判断 PWM调光信号的占空比是否低于预设的阈值。本技 术方案只需要两个电阻就能将复杂的 PWM 占空比信号采集转换成筒单的电压 大小采集， 实施方式筒单， 成本低廉。
进一步的， 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背 光驱动电路的接地端之间串接有第一电阻和第二电阻， 所述第一可控开关与所 述第二电阻并联设置， 所述比较器的反向输入端连接有比较电压， 同向输入端 耦合到所述分压电阻连接光敏电阻的一端。 恒流驱动芯片控制电源模块的驱动 信号频率大小跟频率引脚连接的电阻阻值大小相关， 电阻阻值越大， 驱动信号 的频率越小； 反之， 频率越大， 比较器的反向端连接的比较电压大小跟预设的 阈值对应的分压电阻两端电压相等，当 PWM调光信号的占空比低于预设的阈值 时， 比较器输出低电平信号， 第一可控开关关断， 频率引脚连接的电阻阻值等 于第一电阻和第二电阻阻值之和； 控制模块输出的驱动频率减小， 降低电源模 块开关损耗； 当 PWM调光信号的占空比超过预设的阈值时， 比较器输出高电平 信号， 第一可控开关导通， 频率引脚连接的电阻阻值等于第一电阻的阻值； 控 制模块输出的驱动频率增加， 降低电源模块的导通损耗。
进一步的， 所述频率引脚和所述背光驱动电路的接地端之间串接有光敏电 阻， 所述光敏电阻设置在所述 LED灯条可以直接照射到的位置。 经研究， PWM 调光信号的占空比提高， LED灯条的亮度随之增加； 反之， LED灯条的亮度减 小。 本技术方案通过光敏电阻来捕捉 LED灯条亮度的变化， 在基准电压和分压 电阻阻值不变的前提下， 当 PWM调光信号的占空比较大时， LED平均电流大， 发光亮度高， 光敏电阻阻值小， 光敏电阻阻值增加； 恒流驱动芯片控制电源模 块的驱动信号频率大小跟频率引脚连接的电阻阻值大小相关， 电阻阻值越大， 驱动信号的频率越小； 反之， 频率越大。
因此，只要把光敏电阻设置到 LED灯条发出的光线可以直接照射到的地方， 然后将其阻值反馈给频率引脚， 这样随着亮度降低， 控制模块的输出频率会逐 步降低， 减少在低载时的开关损耗， 提高了背光驱动电路的转换效率。 本技术 方案只需要采用一个光敏电阻就能同时实现检测模块和监控模块的功能， 成本 低廉， 而且可以实现控制模块驱动频率的连续可调， 提高了控制精度。
进一步的， 所述检测模块包括滤波电阻和滤波电容； 所述监控模块包括比 较器、 第一可控开关； 所述频率引脚和背光驱动电路的接地端之间串接有第一 电阻和第二电阻， 所述第一可控开关与所述第二电阻并联设置， 所述比较器的 反向输入端连接有比较电压，所述 PWM调光信号通过滤波电阻连接到比较器的 反向输入端， 所述滤波电容串接在所述比较器的反向输入端和 LED背光驱动电 路的接地端之间。本技术方案采用 RC滤波器将高频变动的 PWM调光信号转换 成平整的电压信号，将矩形波的 PWM调光信号转换成平稳的直流电压信号， 不 同的占空比对应不同数值的直流电压信号。 因此， 可以将预设的阈值对应的 PWM调光信号的等效电压作为比较， 跟滤波后的 PWM调光信号的电压进行比 对，就可以判断 PWM调光信号的占空比是否超出阈值。本技术方案将负载的占 空比比较转换成筒单的电压大小比较， 降低了技术难度， 有利于提升开发进度， 减少研发成本。
进一步的， 所述检测模块包括分压电阻和邻近 LED灯条的光敏电阻， 所述 光敏电阻一端通过分压电阻连接到一高电平的基准电压， 另一端连接到背光驱 动电路的接地端；
所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路 的接地端之间串接有第一电阻和第二电阻， 所述第一可控开关与所述第二电阻 并联设置， 所述比较器的同向输入端连接有比较电压， 反向输入端耦合到所述 分压电阻连接光敏电阻的一端。
此为一种具体的检测模块和监控模块的电路。 经研究， PWM调光信号的占 空比的提高， LED灯条的亮度随之增加； 反之， LED灯条的亮度减小。 本技术 方案通过光敏电阻来捕捉 LED灯条亮度的变化， 在基准电压和分压电阻阻值不 变的前提下， 当 PWM调光信号的占空比较大时， LED平均电流大， 发光亮度 高， 光敏电阻阻值小； 反之， 光敏电阻阻值增加。 只要将 PWM调光信号的占空 比和光敏电阻两端的电压建立映射关系， 监控模块就可以根据光敏电阻两端电 压的变化来判断 PWM调光信号的占空比是否低于预设的阈值。本技术方案只需 要两个电阻就能将复杂的 PWM占空比信号采集转换成筒单的电压大小采集，实 施方式筒单， 成本低廉。
恒流驱动芯片控制电源模块的驱动信号频率大小跟频率引脚连接的电阻阻 值大小相关， 电阻阻值越大， 驱动信号的频率越小； 反之， 频率越大， 比较器 的同向端连接的比较电压大小跟预设的阈值对应的分压电阻两端电压相等， 当 PWM调光信号的占空比低于预设的阈值时， 比较器输出低电平信号， 第一可控 开关关断， 频率引脚连接的电阻阻值等于第一电阻和第二电阻阻值之和； 控制 模块输出的驱动频率减小， 降低电源模块开关损耗； 当 PWM调光信号的占空比 超过预设的阈值时， 比较器输出高电平信号， 第一可控开关导通， 频率引脚连 接的电阻阻值等于第一电阻的阻值； 控制模块输出的驱动频率增加， 降低电源 模块的导通损耗。
进一步的， 所述电源模块包括电感、 二极管、 调压可控开关和电容； 所述 电感的一端耦合到外部的输入电压， 另一端耦合二极管正极， 并通过调压可控 开关耦合到背光驱动电路的接地端； 所述二极管的负极耦合到所述 LED灯条的 正极； 并通过电容耦合到所述接地端； 所述调压可控开关耦合到所述控制模块。 此为一种采用升压电路的电源模块。
进一步的， 所述侦测模块包括调光可控开关， 调光可控开关的输入端耦合 到所述 LED灯条的负极；其输出端通过一限流电阻耦合到 LED背光驱动电路的 接地端；所述 PWM调光信号耦合到所述调光可控开关的控制端。此为一种具体 的侦测模块电路。
进一步的， 所述电源模块包括电感、 二极管、 调压可控开关和电容； 所述 电感的一端耦合到外部的输入电压， 另一端耦合二极管正极， 并通过调压可控 开关耦合到背光驱动电路的接地端； 所述二极管的负极耦合到所述 LED灯条的 正极； 并通过电容耦合到所述接地端； 所述调压可控开关耦合到所述控制模块； 所述侦测模块包括调光可控开关， 调光可控开关的输入端耦合到所述 LED 灯条的负极； 其输出端通过一限流电阻耦合到 LED背光驱动电路的接地端； 所 述 PWM调光信号耦合到所述调光可控开关的控制端；
所述检测模块包括分压电阻和邻近 LED灯条的光敏电阻， 所述光敏电阻一 端连有高电平的基准电压， 另一端通过分压电阻连接到背光驱动电路的接地端； 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路 的接地端之间串接有第一电阻和第二电阻， 所述第一可控开关与所述第二电阻 并联设置， 所述比较器的反向输入端连接有比较电压， 同向输入端耦合到所述 分压电阻连接光敏电阻的一端。
一种液晶显示装置， 包括本发明所述的背光驱动电路。
一种背光驱动电路的驱动方法， 所述背光驱动电路包括通过开关频率控制 的电源模块、与电源模块耦合的 LED灯条、调节流经 LED灯条有效电流占空比 的侦测模块，所述侦测模块耦合到外部的 PWM调光信号； 所述驱动方法包括步 骤：
A 、 预设 PWM调光信号的占空比的阈值；
B、 实时监测 PWM调光信号的占空比信息， 如果 PWM调光信号的占空比 低于预设的阈值， 降低电源模块的开关频率； 反之， 维持现状。
经研究， 背光驱动电路在调光状态时， LED灯条的电流跟随 PWM调光信 号变化， 随着 LED电流平均值减小，输出功率降低， 电感上的电流也随之减小， 此时电源模块的损耗主要为开关损耗， 即恒流驱动芯片控制模块的驱动频率的 大小对其的影响。 因此本发明增加了检测模块和监控模块，
先预设 PWM调光信号的占空比的阈值；检测模块实时监测 PWM调光信号 的占空比信息，如果 PWM调光信号的占空比低于预设的阈值， 降低电源模块的 开关频率； 反之， 维持现状。 这样就可以在 LED灯条的电流平均值减小时降低 开关频率， 从而减少开关损耗； 提高了电源模块的转换效率。
【附图说明】
图 1是现有的一种背光驱动电路的原理示意图；
图 2是本发明实施例一背光驱动电路的原理示意图；
图 3是本发明实施例二背光驱动电路的原理示意图；
图 4是本发明实施例三背光驱动电路的原理示意图；
图 5是本发明实施例四背光驱动电路的原理示意图；
图 6是本发明实施例五背光驱动电路的驱动方法示意图。
【具体实施方式】
本发明公开一种液晶显示装置， 液晶显示装置包括液晶面板和背光模组， 背 光模组包括背光驱动电路。 背光驱动电路包括恒流驱动芯片、 电源模块、 与电 源模块耦合的 LED灯条，恒流驱动芯片包括控制电源模块开关频率的控制模块， 以及调节流经 LED灯条有效电流占空比的侦测模块； 控制模块设有用于设置电 源模块开关频率的频率引脚，侦测模块耦合到外部的 PWM调光信号； 背光驱动 电路还包括采集 PWM调光信号占空比的检测模块， 与检测模块耦合的监控模 块。 当 PWM调光信号的占空比低于预设的阈值时，监控模块输出调低频率的信 号到频率引脚。
经研究， 背光驱动电路在调光状态时， LED灯条的电流跟随 PWM调光信号 变化， 随着 LED电流平均值减小， 输出功率降低， 电感上的电流也随之减小， 此时电源模块的损耗主要为开关损耗， 即恒流驱动芯片控制模块的驱动频率的 大小对其的影响。 因此本发明增加了检测模块和监控模块，
先预设 PWM调光信号的占空比的阈值； 检测模块实时监测 PWM调光信号 的占空比信息，如果 PWM调光信号的占空比低于预设的阈值， 降低电源模块的 开关频率； 反之， 维持现状。 这样就可以在 LED灯条的电流平均值减小时降低 开关频率， 从而减少开关损耗； 提高了电源模块的转换效率。
下面结合附图和较佳的实施例对本发明作进一步说明。
实施例一
如图 2所示， 背光驱动电路 1 包括恒流驱动芯片 20、 电源模块 10、 与电源 模块 10耦合的 LED灯条 30, 恒流驱动芯片 20包括控制电源模块 10开关频率 的控制模块 21 , 以及调节流经 LED灯条 30有效电流占空比的侦测模块 23; 控 制模块 21设有用于设置电源模块 10开关频率的频率引脚 22,侦测模块 23耦合 到外部的 PWM调光信号；背光驱动电路还包括采集 PWM调光信号占空比的检 测模块 40, 与检测模块 40耦合的监控模块 50。
当 PWM调光信号的占空比低于预设的阈值时，监控模块 5050输出调低频率 的信号到频率引脚 22。
电源模块 10包括电感 二极管 D、 调压可控开关 Q2和电容 C; 电感 L的 一端耦合到外部的输入电压， 另一端耦合二极管 D正极， 并通过调压可控开关 Q2耦合到背光驱动电路的接地端；二极管 D的负极耦合到 LED灯条 30的正极； 并通过电容 C耦合到接地端； 调压可控开关 Q2耦合到控制模块 21 ; 侦测模块 23包括调光可控开关 Q3, 调光可控开关 Q3的输入端耦合到 LED灯条 30的负 极； 其输出端通过一限流电阻 R5耦合到 LED背光驱动电路的接地端； PWM调 光信号耦合到调光可控开关 Q3的控制端。
检测模块 40包括分压电阻 R4和邻近 LED灯条 30的光敏电阻 R3 , 光敏电 阻 R3—端连有高电平 （logic 1 ) 的基准电压， 另一端通过分压电阻 R4连接到 背光驱动电路的接地端。 基准电压可以采用电路中存在的稳定的高电平电压， 如 10V、 12V、 5V等常用电压。
监控模块 50包括比较器 ΟΡ1、 第一可控开关 Q1; 频率引脚 22和背光驱动 电路的接地端之间串接有第一电阻 RT1和第二电阻 RT2,第一可控开关 Q1与第 二电阻 RT2并联设置， 比较器 OP1的反向输入端连接有比较电压 VF, 同向输 入端耦合到分压电阻 R4连接光敏电阻 R3的一端。
经研究， PWM调光信号的占空比的提高， LED灯条 30的亮度随之增加； 反 之， LED灯条 30的亮度减小。 本技术方案通过光敏电阻 R3来捕捉 LED灯条 30亮度的变化，在基准电压和分压电阻 R4阻值不变的前提下， 当 PWM调光信 号的占空比较大时， LED平均电流大， 发光亮度高， 光敏电阻 R3阻值小， 这样 分压电阻 R4两端的电压就会增加； 反之， 分压电阻 R4两端的电压就会降低。 只要将 PWM调光信号的占空比和分压电阻 R4两端的电压建立映射关系， 监控 模块 50就可以根据分压电阻 R4两端电压的变化来判断 PWM调光信号的占空 比是否低于预设的阈值。本技术方案只需要两个电阻就能将复杂的 PWM占空比 信号采集转换成筒单的电压大小采集， 实施方式筒单， 成本低廉。
恒流驱动芯片 20控制电源模块 10的驱动信号频率大小跟频率引脚 22连接 的电阻阻值大小相关， 电阻阻值越大， 驱动信号的频率越小； 反之， 频率越大， 比较器 OP1的反向端连接的比较电压 VF大小跟预设的阈值对应的分压电阻 R4 两端电压相等， 当 PWM调光信号的占空比低于预设的阈值时， 比较器 OP1输 出低电平 (logic 0)信号， 第一可控开关 Q1关断， 频率引脚 22连接的电阻阻值等 于第一电阻 RT1和第二电阻 RT2阻值之和； 控制模块 21输出的驱动频率减小， 降低电源模块 10开关损耗； 当 PWM调光信号的占空比超过预设的阈值时， 比 较器 OP1输出高电平信号， 第一可控开关 Q1导通， 频率引脚 22连接的电阻阻 值等于第一电阻 RT1的阻值； 控制模块 21输出的驱动频率增加， 降低电源模块 10的导通损耗。
实施例二
如图 3所示， 背光驱动电路包括恒流驱动芯片 20、 电源模块 10、 与电源模 块 10耦合的 LED灯条 30, 恒流驱动芯片 20包括控制电源模块 10开关频率的 控制模块 21 , 以及调节流经 LED灯条 30有效电流占空比的侦测模块 23; 控制 模块 21设有用于设置电源模块 10开关频率的频率引脚 22,侦测模块 23耦合到 外部的 PWM调光信号；背光驱动电路还包括采集 PWM调光信号占空比的检测 模块 40, 与检测模块 40耦合的监控模块 50。
当 PWM调光信号的占空比低于预设的阈值时，监控模块 50输出调低频率的 信号到频率引脚 22。
电源模块 10包括电感 二极管 D、 调压可控开关 Q2和电容 C; 电感 L的 一端耦合到外部的输入电压， 另一端耦合二极管 D正极， 并通过调压可控开关 Q2耦合到背光驱动电路的接地端；二极管 D的负极耦合到 LED灯条 30的正极； 并通过电容 C耦合到接地端； 调压可控开关 Q2耦合到控制模块 21 ; 侦测模块 23包括调光可控开关 Q3, 调光可控开关 Q3的输入端耦合到 LED灯条 30的负 极； 其输出端通过一限流电阻 R5耦合到 LED背光驱动电路的接地端； PWM调 光信号耦合到调光可控开关 Q3的控制端。
检测模块 40包括分压电阻 R4和邻近 LED灯条 30的光敏电阻 R3 , 光敏电 阻 R3—端通过分压电阻 R4连接到一高电平的基准电压， 另一端连接到背光驱 动电路的接地端。 基准电压可以采用电路中存在的稳定的高电平电压， 如 10V、 12V、 5V等常用电压。
监控模块 50包括比较器 ΟΡ1、 第一可控开关 Q1; 频率引脚 22和背光驱动 电路的接地端之间串接有第一电阻 RT1和第二电阻 RT2,第一可控开关 Q1与第 二电阻 RT2并联设置， 比较器 OP1的同向输入端连接有比较电压 VF, 反向输 入端耦合到分压电阻 R4连接光敏电阻 R3的一端。
经研究， PWM调光信号的占空比的提高， LED灯条 30的亮度随之增加； 反 之， LED灯条 30的亮度减小。 本技术方案通过光敏电阻 R3来捕捉 LED灯条 30亮度的变化，在基准电压和分压电阻 R4阻值不变的前提下， 当 PWM调光信 号的占空比较大时， LED平均电流大，发光亮度高，光敏电阻 R3阻值小；反之， 光敏电阻 R3阻值增加。 只要将 PWM调光信号的占空比和光敏电阻 R3两端的 电压建立映射关系， 监控模块 50就可以根据光敏电阻 R3两端电压的变化来判 断 PWM调光信号的占空比是否低于预设的阈值。本技术方案只需要两个电阻就 能将复杂的 PWM占空比信号采集转换成筒单的电压大小采集， 实施方式筒单， 成本低廉。
恒流驱动芯片 20控制电源模块 10的驱动信号频率大小跟频率引脚 22连接 的电阻阻值大小相关， 电阻阻值越大， 驱动信号的频率越小； 反之， 频率越大， 比较器 OP1的同向端连接的比较电压 VF大小跟预设的阈值对应的分压电阻 R4 两端电压相等， 当 PWM调光信号的占空比低于预设的阈值时， 比较器 OP1输 出低电平信号， 第一可控开关 Q1关断， 频率引脚 22连接的电阻阻值等于第一 电阻 RT1和第二电阻 RT2阻值之和； 控制模块 21输出的驱动频率减小， 降低 电源模块 10开关损耗； 当 PWM调光信号的占空比超过预设的阈值时， 比较器 OP1输出高电平信号， 第一可控开关 Q1导通， 频率引脚 22连接的电阻阻值等 于第一电阻 RT1的阻值； 控制模块 21输出的驱动频率增加， 降低电源模块 10 的导通损耗。
实施例三
如图 4所示， 本实施方式的检测模块 40包括滤波电阻 RQ和滤波电容 CQ; 监 控模块 50包括比较器 ΟΡ1、 第一可控开关 Q1 ; 频率引脚 22和背光驱动电路的 接地端之间串接有第一电阻 RT1和第二电阻 RT2 ,第一可控开关 Q1与第二电阻 RT2并联设置， 比较器 OP1的反向输入端连接有比较电压 VF, PWM调光信号 通过滤波电阻 R。连接到比较器 OP1的反向输入端， 滤波电容 C。串接在比较器 OP1的反向输入端和 LED背光驱动电路的接地端之间。
本实施方式的检测模块 40采用 RC滤波器将高频变动的 PWM调光信号转换 成平整的电压信号，将矩形波的 PWM调光信号转换成平稳的直流电压信号， 不 同的占空比对应不同数值的直流电压信号。 因此， 可以将预设的阈值对应的 PWM调光信号的等效电压作为比较， 跟滤波后的 PWM调光信号的电压进行比 对，就可以判断 PWM调光信号的占空比是否超出阈值。本技术方案将负载的占 空比比较转换成筒单的电压大小比较， 降低了技术难度， 有利于提升开发进度， 减少研发成本。
实施例四
如图 5所示， 恒流驱动芯片 20的频率引脚 22和背光驱动电路的接地端之间 串接有光敏电阻 R3, 光敏电阻 R3设置在 LED灯条 30可以直接照射到的位置。 经研究， PWM调光信号的占空比提高， LED灯条的亮度随之增加； 反之， LED 灯条的亮度减小。 本技术方案通过光敏电阻来捕捉 LED灯条亮度的变化， 在基 准电压和分压电阻阻值不变的前提下， 当 PWM调光信号的占空比较大时， LED 平均电流大， 发光亮度高， 光敏电阻阻值小， 光敏电阻阻值增加； 恒流驱动芯 片控制电源模块的驱动信号频率大小跟频率引脚连接的电阻阻值大小相关， 电 阻阻值越大， 驱动信号的频率越小； 反之， 频率越大。
因此， 只要把光敏电阻设置到 LED灯条发出的光线可以直接照射到的地方， 然后将其阻值反馈给频率引脚， 这样随着亮度降低， 控制模块的输出频率会逐 步降低， 减少在低载时的开关损耗， 提高了背光驱动电路的转换效率。 本技术 方案只需要采用一个光敏电阻就能同时实现检测模块和监控模块的功能， 成本 低廉， 而且可以实现控制模块驱动频率的连续可调， 提高了控制精度。
实施例五
如图 6所示， 本发明还公开了一种背光驱动电路的驱动方法， 背光驱动电路 包括通过开关频率控制的电源模块、与电源模块耦合的 LED灯条、调节流经 LED 灯条有效电流占空比的侦测模块，侦测模块耦合到外部的 PWM调光信号；驱动 方法包括步骤：
A 、 预设 PWM调光信号的占空比的阈值；
B、 实时监测 PWM调光信号的占空比信息， 如果 PWM调光信号的占空比 低于预设的阈值， 降低电源模块的开关频率； 反之， 维持现状。
以上内容是结合具体的优选实施方式对本发明所作的进一步详细说明， 不能 认定本发明的具体实施只局限于这些说明。 对于本发明所属技术领域的普通技 术人员来说， 在不脱离本发明构思的前提下， 还可以做出若干筒单推演或替换， 都应当视为属于本发明的保护范围。

Claims

权利要求
1. 一种背光驱动电路， 包括恒流驱动芯片、 电源模块、 与电源模块耦合的 LED灯条， 所述恒流驱动芯片包括控制电源模块开关频率的控制模块， 以及调 节流经 LED灯条有效电流占空比的侦测模块； 所述控制模块设有用于设置电源 模块开关频率的频率引脚，所述侦测模块耦合到外部的 PWM调光信号； 所述背 光驱动电路还包括采集 PWM调光信号占空比的检测模块，与检测模块耦合的监 控模块，
当所述 PWM调光信号的占空比低于预设的阈值时，所述监控模块输出调低 频率的信号到所述频率引脚。
2. 如权利要求 1所述的背光驱动电路， 其中， 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路的接地端之间串接有第一电阻和 第二电阻， 所述第一可控开关与所述第二电阻并联设置， 所述比较器的反向输 入端连接有比较电压， 同向输入端耦合到所述分压电阻连接到检测模块。
3. 如权利要求 1所述的背光驱动电路， 其中， 所述检测模块包括分压电阻 和邻近 LED灯条的光敏电阻， 所述光敏电阻一端连有高电平的基准电压， 另一 端通过分压电阻连接到背光驱动电路的接地端， 所述分压电阻两端的电压反馈 到所述监控模块。
4. 如权利要求 3所述的背光驱动电路， 其中， 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路的接地端之间串接有第一电阻和 第二电阻， 所述第一可控开关与所述第二电阻并联设置， 所述比较器的反向输 入端连接有比较电压， 同向输入端耦合到所述分压电阻连接到检测模块。
5. 如权利要求 1所述的背光驱动电路， 其中， 所述频率引脚和所述背光驱 动电路的接地端之间串接有光敏电阻， 所述光敏电阻设置在所述 LED灯条可以 直接照射到的位置。
6. 如权利要求 1所述的背光驱动电路， 其中， 所述检测模块包括滤波电阻 和滤波电容； 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光 驱动电路的接地端之间串接有第一电阻和第二电阻， 所述第一可控开关与所述 第二电阻并联设置，所述比较器的反向输入端连接有比较电压，所述 PWM调光 信号通过滤波电阻连接到比较器的反向输入端， 所述滤波电容串接在所述比较 器的反向输入端和 LED背光驱动电路的接地端之间。
7. 如权利要求 1所述的背光驱动电路， 其中， 所述电源模块包括电感、 二 极管、 调压可控开关和电容； 所述电感的一端耦合到外部的输入电压， 另一端 耦合二极管正极， 并通过调压可控开关耦合到背光驱动电路的接地端； 所述二 极管的负极耦合到所述 LED灯条的正极； 并通过电容耦合到所述接地端； 所述 调压可控开关耦合到所述控制模块。
8. 如权利要求 1所述的背光驱动电路， 其中， 所述侦测模块包括调光可控 开关， 调光可控开关的输入端耦合到所述 LED灯条的负极； 其输出端通过一限 流电阻耦合到 LED背光驱动电路的接地端； 所述 PWM调光信号耦合到所述调 光可控开关的控制端。
9. 如权利要求 1所述的背光驱动电路， 其中， 所述电源模块包括电感、 二 极管、 调压可控开关和电容； 所述电感的一端耦合到外部的输入电压， 另一端 耦合二极管正极， 并通过调压可控开关耦合到背光驱动电路的接地端； 所述二 极管的负极耦合到所述 LED灯条的正极； 并通过电容耦合到所述接地端； 所述 调压可控开关耦合到所述控制模块；
所述侦测模块包括调光可控开关， 调光可控开关的输入端耦合到所述 LED 灯条的负极； 其输出端通过一限流电阻耦合到 LED背光驱动电路的接地端； 所 述 PWM调光信号耦合到所述调光可控开关的控制端；
所述检测模块包括分压电阻和邻近 LED灯条的光敏电阻， 所述光敏电阻一 端连有高电平的基准电压， 另一端通过分压电阻连接到背光驱动电路的接地端； 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路 的接地端之间串接有第一电阻和第二电阻， 所述第一可控开关与所述第二电阻 并联设置， 所述比较器的反向输入端连接有比较电压， 同向输入端耦合到所述 分压电阻连接光敏电阻的一端。
10. 一种液晶显示装置， 包括背光驱动电路； 所述背光驱动电路包括恒流驱 动芯片、 电源模块、 与电源模块耦合的 LED灯条， 所述恒流驱动芯片包括控制 电源模块开关频率的控制模块， 以及调节流经 LED灯条有效电流占空比的侦测 模块； 所述控制模块设有用于设置电源模块开关频率的频率引脚， 所述侦测模 块耦合到外部的 PWM调光信号；所述背光驱动电路还包括采集 PWM调光信号 占空比的检测模块， 与检测模块耦合的监控模块，
当所述 PWM调光信号的占空比低于预设的阈值时，所述监控模块输出调低 频率的信号到所述频率引脚。
11. 如权利要求 10所述的液晶显示装置， 其中， 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路的接地端之间串接有第一电阻和 第二电阻， 所述第一可控开关与所述第二电阻并联设置， 所述比较器的反向输 入端连接有比较电压， 同向输入端耦合到所述分压电阻连接到检测模块。
12. 如权利要求 10所述的液晶显示装置， 其中， 所述检测模块包括分压电 阻和邻近 LED灯条的光敏电阻， 所述光敏电阻一端连有高电平的基准电压， 另 一端通过分压电阻连接到背光驱动电路的接地端， 所述分压电阻两端的电压反 馈到所述监控模块。
13. 如权利要求 12所述的液晶显示装置， 其中， 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路的接地端之间串接有第一电阻和 第二电阻， 所述第一可控开关与所述第二电阻并联设置， 所述比较器的反向输 入端连接有比较电压， 同向输入端耦合到所述分压电阻连接到检测模块。
14. 如权利要求 10所述的液晶显示装置， 其中， 所述频率引脚和所述背光 驱动电路的接地端之间串接有光敏电阻， 所述光敏电阻设置在所述 LED灯条可 以直接照射到的位置。
15. 如权利要求 10所述的液晶显示装置， 其中， 所述检测模块包括滤波电 阻和滤波电容； 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背 光驱动电路的接地端之间串接有第一电阻和第二电阻， 所述第一可控开关与所 述第二电阻并联设置，所述比较器的反向输入端连接有比较电压，所述 PWM调 光信号通过滤波电阻连接到比较器的反向输入端， 所述滤波电容串接在所述比 较器的反向输入端和 LED背光驱动电路的接地端之间。
16. 如权利要求 10所述的液晶显示装置， 其中， 所述电源模块包括电感、 二极管、 调压可控开关和电容； 所述电感的一端耦合到外部的输入电压， 另一 端耦合二极管正极， 并通过调压可控开关耦合到背光驱动电路的接地端； 所述 二极管的负极耦合到所述 LED灯条的正极； 并通过电容耦合到所述接地端； 所 述调压可控开关耦合到所述控制模块。
17. 如权利要求 10所述的液晶显示装置， 其中， 所述侦测模块包括调光可 控开关， 调光可控开关的输入端耦合到所述 LED灯条的负极； 其输出端通过一 限流电阻耦合到 LED背光驱动电路的接地端； 所述 PWM调光信号耦合到所述 调光可控开关的控制端。
18. 如权利要求 10所述的液晶显示装置， 其中， 所述电源模块包括电感、 二极管、 调压可控开关和电容； 所述电感的一端耦合到外部的输入电压， 另一 端耦合二极管正极， 并通过调压可控开关耦合到背光驱动电路的接地端； 所述 二极管的负极耦合到所述 LED灯条的正极； 并通过电容耦合到所述接地端； 所 述调压可控开关耦合到所述控制模块；
所述侦测模块包括调光可控开关， 调光可控开关的输入端耦合到所述 LED 灯条的负极； 其输出端通过一限流电阻耦合到 LED背光驱动电路的接地端； 所 述 PWM调光信号耦合到所述调光可控开关的控制端；
所述检测模块包括分压电阻和邻近 LED灯条的光敏电阻， 所述光敏电阻一 端连有高电平的基准电压， 另一端通过分压电阻连接到背光驱动电路的接地端； 所述监控模块包括比较器、 第一可控开关； 所述频率引脚和背光驱动电路 的接地端之间串接有第一电阻和第二电阻， 所述第一可控开关与所述第二电阻 并联设置， 所述比较器的反向输入端连接有比较电压， 同向输入端耦合到所述 分压电阻连接光敏电阻的一端。
19. 一种背光驱动电路的驱动方法，所述背光驱动电路包括通过开关频率控 制的电源模块、与电源模块耦合的 LED灯条、调节流经 LED灯条有效电流占空 比的侦测模块，所述侦测模块耦合到外部的 PWM调光信号； 所述驱动方法包括 步骤：
A 、 预设 PWM调光信号的占空比的阈值；
B、 实时监测 PWM调光信号的占空比信息， 如果 PWM调光信号的占空比 低于预设的阈值， 降低电源模块的开关频率； 反之， 维持现状。
PCT/CN2013/078153 2013-05-20 2013-06-27 一种背光驱动电路、液晶显示装置和背光驱动方法 WO2014187005A1 (zh)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114495846A (zh) * 2022-02-21 2022-05-13 冠捷电子科技(福建)有限公司 一种显示器变频调光方法及变频调光显示器

Families Citing this family (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103440848B (zh) * 2013-09-02 2016-01-20 深圳市华星光电技术有限公司 背光驱动电路
CN203858849U (zh) * 2014-05-15 2014-10-01 高创(苏州)电子有限公司 背光调节装置、背光模组及显示装置
TWI558262B (zh) 2015-01-28 2016-11-11 友達光電股份有限公司 發光二極體驅動器
CN104853490B (zh) * 2015-05-14 2017-06-23 科博达技术有限公司 一种用于汽车照明***的pwm信号滤波方法
CN105717438A (zh) * 2016-01-29 2016-06-29 环鸿电子（昆山）有限公司 电流信号的测试装置及其测试方法
CN106448577B (zh) * 2016-11-29 2019-02-26 深圳创维－Rgb电子有限公司 一种背光恒流驱动板及液晶电视机
CN107277985B (zh) * 2017-08-15 2023-10-24 合肥惠科金扬科技有限公司 Led调光电路和led显示设备
CN107342059B (zh) * 2017-08-31 2019-07-23 京东方科技集团股份有限公司 一种电流控制电路及控制方法、背光模组、显示装置
CN108520720B (zh) * 2018-07-13 2020-06-30 四川长虹电器股份有限公司 一种液晶电视背光多分区控制***
CN109757007B (zh) * 2019-02-25 2020-08-11 深圳市华星光电半导体显示技术有限公司 电源电路
CN111210782A (zh) * 2020-03-10 2020-05-29 上海闻泰电子科技有限公司 同步整流背光驱动电路、电子设备及方法
CN111739477B (zh) * 2020-06-30 2022-09-13 昆山龙腾光电股份有限公司 调光电路和显示装置
CN112102788B (zh) * 2020-09-18 2021-12-28 深圳创维－Rgb电子有限公司 一种恒流背光输出通道控制***及显示设备
CN112102789A (zh) * 2020-09-25 2020-12-18 南京中电熊猫液晶显示科技有限公司 一种液晶显示模组以及降低背光功耗的方法
CN112669767B (zh) * 2020-12-28 2023-05-30 深圳创维－Rgb电子有限公司 一种Mini LED驱动***及其驱动方法
CN113602192B (zh) * 2021-09-09 2023-04-07 深圳市豪恩汽车电子装备股份有限公司 电子后视镜及其自动调光电路和方法
CN114474157A (zh) * 2022-02-18 2022-05-13 坎德拉（深圳）科技创新有限公司 一种补光装置及机器人
CN115035867B (zh) * 2022-07-20 2023-04-28 绵阳惠科光电科技有限公司 背光驱动电路及方法、背光模组以及显示装置
KR20230096121A (ko) 2022-07-20 2023-06-29 몐양 에이치케이씨 옵토일렉트로닉스 테크놀로지 씨오., 엘티디. 백라이트 구동 회로, 백라이트 모듈 및 표시 장치
CN117318488B (zh) * 2023-11-29 2024-05-14 荣耀终端有限公司 一种多相电源和电子设备

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060175986A1 (en) * 2005-02-04 2006-08-10 Samsung Electro-Mechanics Co., Ltd. LED array driving apparatus and backlight driving apparatus using the same
CN101668377A (zh) * 2008-09-03 2010-03-10 冠捷投资有限公司 冷阴极灯管换流器及其控制方法、控制模块
CN201523469U (zh) * 2009-11-07 2010-07-07 桂林电子科技大学 一种智能化led脉冲驱动电路
TW201110093A (en) * 2009-09-03 2011-03-16 Chunghwa Picture Tubes Ltd Display device and backlight control method thereof
CN102982772A (zh) * 2012-12-11 2013-03-20 友达光电股份有限公司 一种用于液晶面板的调光控制电路

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7202608B2 (en) * 2004-06-30 2007-04-10 Tir Systems Ltd. Switched constant current driving and control circuit
JP5399943B2 (ja) * 2010-02-22 2014-01-29 パナソニック株式会社 Ｌｅｄ点灯回路
JP5616768B2 (ja) * 2010-12-08 2014-10-29 ローム株式会社 発光素子の駆動回路、それを用いた発光装置および電子機器
GB2492833A (en) * 2011-07-14 2013-01-16 Softkinetic Sensors Nv LED boost converter driver circuit for Time Of Flight light sources

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060175986A1 (en) * 2005-02-04 2006-08-10 Samsung Electro-Mechanics Co., Ltd. LED array driving apparatus and backlight driving apparatus using the same
CN101668377A (zh) * 2008-09-03 2010-03-10 冠捷投资有限公司 冷阴极灯管换流器及其控制方法、控制模块
TW201110093A (en) * 2009-09-03 2011-03-16 Chunghwa Picture Tubes Ltd Display device and backlight control method thereof
CN201523469U (zh) * 2009-11-07 2010-07-07 桂林电子科技大学 一种智能化led脉冲驱动电路
CN102982772A (zh) * 2012-12-11 2013-03-20 友达光电股份有限公司 一种用于液晶面板的调光控制电路

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114495846A (zh) * 2022-02-21 2022-05-13 冠捷电子科技(福建)有限公司 一种显示器变频调光方法及变频调光显示器
CN114495846B (zh) * 2022-02-21 2024-05-14 冠捷电子科技(福建)有限公司 一种显示器变频调光方法及变频调光显示器

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