WO2014101005A1 - 一种led背光驱动电路 - Google Patents

一种led背光驱动电路 Download PDF

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Publication number
WO2014101005A1
WO2014101005A1 PCT/CN2012/087545 CN2012087545W WO2014101005A1 WO 2014101005 A1 WO2014101005 A1 WO 2014101005A1 CN 2012087545 W CN2012087545 W CN 2012087545W WO 2014101005 A1 WO2014101005 A1 WO 2014101005A1
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Prior art keywords
comparator
voltage
coupled
reference voltage
output
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Ceased
Application number
PCT/CN2012/087545
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English (en)
French (fr)
Inventor
胡安乐
杨翔
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TCL China Star Optoelectronics Technology Co Ltd
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Shenzhen China Star Optoelectronics Technology Co Ltd
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Priority to US13/809,448 priority Critical patent/US9230490B2/en
Publication of WO2014101005A1 publication Critical patent/WO2014101005A1/zh
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/38—Switched mode power supply [SMPS] using boost topology
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the present invention relates to the field of liquid crystal display, and more particularly to an LED backlight driving circuit. ⁇ Background technique ⁇
  • the existing liquid crystal display device uses LED as a backlight, and the specific method is to connect a plurality of LED lamps in series to form an LED strip, and then couple the LED strip to a booster circuit.
  • the controllable switch Q of the boosting circuit is coupled to a backlight driving chip IC, and the output voltage of the boosting circuit can be adjusted according to the duty ratio of the output signal of the backlight driving chip driving pin G, thereby realizing the LED light bar. Dimming. If there are multiple LED strips, they can be coupled in parallel to the same boost circuit.
  • a backlight is provided inside the backlight driving chip, and an output end of each LED light bar is coupled to an inverting input end of the comparator; a non-inverting input end of the comparator is coupled to a reference voltage, and the comparator is associated with each LED light bar according to the reference voltage
  • the voltage difference is used to adjust the duty ratio of the output signal of the backlight driving chip, thereby achieving the dimming purpose.
  • the existing backlight driving module has the problem of poor circuit performance, for example, when the LED light bar is lightly loaded (the brightness of the LED light bar is low), a large voltage is still output, which causes the efficiency of the backlight driving to be reduced; or the LED is overloaded ( When the brightness of the LED strip is high, the output voltage is low and the LED strip does not reach the expected brightness.
  • One of the technical problems to be solved by the present invention is to provide an LED backlight driving circuit capable of improving backlight driving efficiency when the LED light bar is lightly loaded.
  • An LED backlight driving circuit includes a driving module of an LED light bar and an LED light bar, wherein the driving module includes a backlight driving chip for adjusting an output voltage of the driving module, and the backlight driving chip includes a backlight for correcting a driving module output voltage.
  • a first comparator an output end of the LED light bar is coupled to an inverting input end of the first comparator; a non-directional input end of the first comparator is coupled with a protection module; a detecting unit that detects an output current of the driving module; When the current value detected by the detecting unit is higher than the preset first current value, the protection module outputs a first reference voltage to the same input end of the first comparator; the current value detected by the detecting unit is low And at a preset first current value, the protection module outputs a second reference voltage that is less than the first reference voltage to a non-inverting input end of the first comparator.
  • the protection module includes a second comparator
  • the detection unit includes a conversion component that converts the detected current value into a voltage value, and the conversion component is coupled to a non-inverting input end of the second comparator;
  • An inverting input of the second comparator is coupled to a third reference voltage;
  • the first reference voltage and the second reference voltage are respectively coupled to two excitation terminals of the second comparator;
  • an output of the second comparator An end coupled to the same input of the first comparator;
  • the second comparator When the current value detected by the detecting unit is higher than the preset first current value, the second comparator outputs a first reference voltage; when the current value detected by the detecting unit is lower than the preset first current value, The second comparator outputs a second reference voltage.
  • This is the circuit structure of a specific protection module.
  • the current information of the set is converted into voltage information and compared with a third reference voltage of the other input of the second comparator to determine whether to output the first reference voltage or the second reference voltage.
  • the driving module of the LED light bar includes an inductor coupled to the power source and a diode coupled to the inductor, and the diode anode is coupled to the input end of the LED strip, and the anode of the diode and the ground of the power source are sequentially connected in series a voltage-controlled switchable switch having a control terminal coupled to the backlight driving chip, and a terminal voltage of the voltage dividing resistor coupled to the same-direction input end of the second comparator .
  • This is a topology of the driving module using the boosting circuit.
  • the current flowing through the voltage dividing resistor of the boosting circuit has a significant linear relationship with the output current of the driving module, so that the terminal voltage of the voltage dividing resistor can be coupled to
  • the second comparator realizes the function of the conversion component of the detecting unit, so that the voltage dividing resistor can complete the function of the boosting circuit and realize the voltage collecting function of the converting component, the circuit is simpler, and the device multiplexing rate is high, which is beneficial to cut costs.
  • the protection module further includes a third comparator, a conversion component of the detection unit is coupled to a non-inverting input end of the third comparator, and a reverse input end of the third comparator is coupled to a fourth a reference voltage, an output of the second comparator is coupled to an excitation terminal of the third comparator;
  • the other excitation end of the three comparators is coupled with a fifth reference voltage; the fourth reference voltage is greater than the third reference voltage; the fifth reference voltage is greater than the first reference voltage;
  • the third comparator When the current value detected by the detecting unit is higher than the preset second current value, the third comparator outputs a fifth reference voltage coupled to the same input end of the first comparator; the second current value Greater than the first current value.
  • the technical solution expands the function of the protection module.
  • the existing drive module outputs heavy load (the current is large, the brightness of the LED light bar is high), the voltage of the output end of the LED light bar increases, and the first comparator coupled thereto The voltage at the inverting input will also increase, and the voltage difference between the inverting input and the first reference voltage will decrease.
  • the backlight driving chip will reduce the duty ratio and reduce the output voltage, resulting in no voltage at the time of heavy load.
  • the LED light bar does not reach the expected brightness; and the protection module can output a fifth reference voltage higher than the first reference voltage in time for heavy load, so that the first comparator reverse input end and the same direction input end
  • the differential pressure increases, and the backlight driver chip increases the duty cycle to increase the output voltage, achieving high-voltage output during heavy loads, ensuring that the LED strips achieve the desired brightness.
  • the driving module of the LED light bar includes an inductor coupled to the power source and a diode coupled to the inductor, and the diode anode is coupled to the input end of the LED strip, and the anode of the diode and the ground of the power source are sequentially connected in series a voltage-controllable switch and a voltage dividing resistor, wherein a control end of the voltage-regulated control switch is coupled to the backlight driving chip, and a terminal voltage of the voltage-dividing resistor is respectively coupled to the second comparator and a third comparison The co-directional input of the device.
  • This is a topology of the driving module using the boosting circuit.
  • the current flowing through the voltage dividing resistor of the boosting circuit has a significant linear relationship with the output current of the driving module, so that the terminal voltage of the voltage dividing resistor can be coupled to
  • the second comparator and the third comparator realize the function of the conversion component of the detecting unit, so that the voltage dividing resistor can complete the function of the boosting circuit and realize the voltage collecting function of the converting component, the circuit is simpler, and the device is reused.
  • the high rate is conducive to reducing costs.
  • the first reference voltage is selected to be 0.6V
  • the second reference voltage is selected to be 0.5V
  • the third reference voltage is selected to be 0.25V
  • the fourth reference voltage is selected to be 0.45V
  • the fifth reference voltage is selected to be 0.7V. This is a specific reference voltage value, which can be applied to the backlight driving of different types of liquid crystal display devices.
  • the backlight driving chip includes an overcurrent protection pin, and a terminal voltage of the voltage dividing resistor Coupled to the protection pin.
  • the backlight driver chip adds an overcurrent protection function, which can adjust the output when the output current of the driver module is too large to prevent the LED strip from being burned out.
  • the driving module of the LED light bar includes an inductor coupled to the power source and a diode coupled to the inductor, and the diode anode is coupled to the input end of the LED strip, and the anode of the diode and the ground of the power source are sequentially connected in series a voltage-controllable switch and a voltage dividing resistor, wherein the detecting unit is the voltage dividing resistor, a control end of the voltage-regulating controllable switch is coupled to the backlight driving chip, and the protection module further includes a third comparator The terminal voltages of the voltage dividing resistors are respectively coupled to the non-inverting input terminals of the second comparator and the third comparator, and the inverting input terminal of the third comparator is coupled with a fourth reference voltage, The output of the second comparator is coupled to the excitation terminal of the third comparator; the other excitation terminal of the third comparator is coupled with a fifth reference voltage; the fourth reference voltage is greater than the third reference voltage; The fifth reference voltage is greater than the
  • the terminal voltage of the voltage resistor is coupled to the same end of the second comparator and the third comparator to realize the function of the detecting unit, so that the voltage dividing resistor can complete the function of the boosting circuit and realize the voltage collecting function of the converting component.
  • the circuit is simpler and the device reuse rate is high, which is beneficial to reduce the cost.
  • a driving method for the LED backlight driving circuit described above comprising the steps of:
  • the protection module Detecting an output current of the driving module, when the current exceeds the preset first current value, the protection module outputs the first reference voltage to the same input end of the first comparator; otherwise, the protection module outputs a second less than the first reference voltage The reference voltage is to the non-inverting input of the first comparator.
  • the driving method further includes setting a second current value greater than the first current value, and when detecting that the output current of the driving module is greater than the second current value, the protection module outputs a fifth reference voltage greater than the first reference voltage to The same input of the first comparator.
  • the technical solution expands the function of the protection module.
  • the existing drive module outputs heavy load (the current is large, the brightness of the LED light bar is high)
  • the voltage of the output end of the LED light bar increases, and the first comparator coupled thereto
  • the voltage at the inverting input will also increase, and the voltage difference between the inverting input and the first reference voltage will decrease.
  • the backlight driver chip will reduce the duty ratio.
  • the output voltage is lowered, so that the voltage does not go up when the load is heavy, so the LED light bar does not reach the expected brightness; and the protection module can output a fifth reference voltage higher than the first reference voltage in time for heavy load, so that the first
  • the voltage difference between the comparator's inverting input and the non-inverting input increases, and the backlight driver chip increases the duty cycle to increase the output voltage, achieving high-voltage output during heavy loads, ensuring that the LED strip achieves the desired brightness.
  • a liquid crystal display device comprising the above-described LED backlight driving circuit.
  • the invention adopts a protection module, and the protection module determines whether the LED light bar is in a light load state by detecting the output current of the driving module, and if the LED light bar works normally, outputs a higher first reference voltage to the backlight driving chip.
  • the first comparator if it is in a light load state (ie, lower than the preset first current value), the output voltage of the LED strip is also reduced, and the voltage of the inverting input of the first comparator coupled thereto is also It will decrease, and the voltage difference between the inverting input terminal and the first reference voltage will increase.
  • the backlight driving chip will increase the duty ratio and increase the output voltage, resulting in excessive voltage at light load and lowering the efficiency of the driving module;
  • the protection module can output a second reference voltage lower than the first reference voltage in time when the load is light, so that the voltage difference between the reverse input end and the same input end of the first comparator is reduced, and the backlight drive chip reduces the duty Compared with lowering the output voltage, it achieves low-voltage output at light load, which improves the efficiency of the drive module.
  • the second technical problem to be solved by the present invention is to provide an LED backlight driving circuit capable of stabilizing the backlight driving efficiency of the LED strip when the LED strip is heavily loaded.
  • An LED backlight driving circuit includes a driving module of an LED light bar and an LED light bar, wherein the driving module includes a backlight driving chip for adjusting an output voltage of the driving module, and the backlight driving chip includes a backlight for correcting a driving module output voltage.
  • a first comparator an output end of the LED light bar is coupled to an inverting input end of the first comparator; a non-inverting input end of the first comparator is coupled with a protection module with a variable output voltage;
  • the protection module includes a detection unit for detecting an output current of the driving module
  • the protection module When the current value detected by the detecting unit is lower than the preset second current value, the protection module outputs a first reference voltage to the same input end of the first comparator; the current value detected by the detecting unit is high And at a preset second current value, the protection module outputs a fifth reference voltage greater than the first reference voltage to the same input end of the first comparator.
  • the protection module includes a third comparator
  • the detecting unit includes a conversion component that converts the detected current value into a voltage value, and the conversion component is coupled to a non-inverting input end of the third comparator;
  • a fourth reference voltage is coupled to the inverting input of the third comparator;
  • the first reference voltage and the fifth reference voltage are respectively coupled to the two excitation terminals of the third comparator;
  • the output of the third comparator An end coupled to the same input of the first comparator;
  • the third comparator When the current value detected by the detecting unit is lower than the preset second current value, the third comparator outputs a first reference voltage; when the current value detected by the detecting unit is higher than the preset second current value, The third comparator outputs a fifth reference voltage.
  • This is the circuit structure of a specific protection module.
  • the current information of the set is converted into voltage information, and compared with a fifth reference voltage of the other input terminal of the third comparator, thereby determining whether to output the first reference voltage or the fifth reference voltage.
  • the backlight driving chip includes an overcurrent protection pin;
  • the driving module of the LED light bar includes an inductor coupled to the power source, and a diode coupled to the inductor, and the diode negative electrode is coupled to the input end of the LED light bar.
  • a voltage-regulating controllable switch and a voltage dividing resistor are sequentially connected in series between the positive pole of the diode and the grounding end of the power supply, and the control end of the voltage-regulating controllable switch is coupled to the backlight driving chip, and the terminal voltages of the voltage dividing resistor are respectively A non-inverting input coupled to the third comparator and a protection pin of the backlight driving chip. This is a topology of the driving module using the boosting circuit.
  • the current flowing through the voltage dividing resistor of the boosting circuit has a significant linear relationship with the output current of the driving module, so that the terminal voltage of the voltage dividing resistor can be coupled to
  • the third comparator realizes the function of the conversion component of the detecting unit, so that the voltage dividing resistor can complete the function of the boosting circuit and realize the voltage collecting function of the converting component, the circuit is simpler, and the device multiplexing rate is high, which is beneficial to cut costs.
  • the backlight driver chip adds overcurrent protection, which can adjust the output when the output current of the driver module is too large to prevent the LED strip from being burned out.
  • the first reference voltage is selected to be 0.6V
  • the fourth reference voltage is selected to be 0.45V
  • the fifth reference voltage is selected to be 0.7V.
  • the backlight driving chip includes an overcurrent protection pin;
  • the driving module of the LED light bar includes an inductor coupled to the power source, and a diode coupled to the inductor, and the diode negative electrode is coupled to the input end of the LED light bar.
  • the detecting unit is the voltage dividing resistor, and the control end of the voltage-regulating controllable switch is coupled to the backlight driving a chip
  • the protection module includes a third comparator, a terminal voltage of the voltage dividing resistor is respectively coupled to a non-inverting input end of the third comparator and a protection pin of the backlight driving chip
  • the detecting unit includes a conversion component that converts the detected current value into a voltage value, the conversion component is coupled to a non-inverting input of the third comparator; the inverting input of the third comparator is coupled with a fourth reference voltage; a first reference voltage and a fifth reference voltage are respectively coupled to the two excitation terminals of the third comparator; an output of the third comparator is coupled to the same of the first comparator Input.
  • the terminal voltage of the voltage resistor is coupled to the same end of the third comparator to realize the function of the detecting unit, so that the voltage dividing resistor can complete the function of the boosting circuit and realize the voltage collecting function of the converting component, and the circuit is simpler.
  • the high reuse rate of the device helps to reduce costs.
  • a driving method for the LED backlight driving circuit described above comprising the steps of:
  • the protection module Detecting an output current of the driving module, when the output current is lower than the preset first current value, the protection module outputs the first reference voltage to the same input end of the first comparator; otherwise, the protection module outputs the output greater than the first reference voltage A fifth reference voltage is applied to the non-inverting input of the first comparator.
  • a liquid crystal display device comprising the above-described LED backlight driving circuit.
  • the invention adopts a protection module, and the protection module determines whether the LED light bar is in a heavy load state by detecting the output current of the driving module, and if the LED light bar works normally, outputs a lower first reference voltage to the backlight driving chip.
  • the first comparator if it is in the heavy load state (ie, exceeds the preset second current value), the output voltage of the LED strip is also increased, and the voltage of the inverting input of the first comparator coupled thereto is also Increasing, the voltage difference between the inverting input terminal and the first reference voltage will be reduced.
  • the backlight driving chip will lower the duty ratio and lower the output voltage, resulting in a voltage that is too low when the load is heavy, and the LED light bar reaches The brightness is less than expected; and the protection module can output a fifth reference voltage higher than the first reference voltage in time, so that the voltage difference between the reverse input end and the same input end of the first comparator increases, and the backlight drive
  • the chip will increase the duty cycle to increase the output voltage, increase the output voltage of the driver module when it is overloaded, and make the LED strip achieve the desired brightness.
  • the third technical problem to be solved by the present invention is to provide an LED backlight driving circuit for improving the circuit performance of the LED light bar driving module.
  • An LED backlight driving circuit includes a driving module of an LED light bar and an LED light bar, wherein the driving module includes a backlight driving chip for adjusting an output voltage of the driving module, and the backlight driving chip includes a backlight for correcting a driving module output voltage.
  • a first comparator an output end of the LED light bar is coupled to an inverting input end of the first comparator; a non-inverting input end of the first comparator is coupled with a protection module with a variable output voltage;
  • the protection module includes a detection unit for detecting an output current of the driving module.
  • the detection unit detects that the output current of the driving module is increased, the voltage outputted by the protection module to the same comparator is synchronously increased.
  • the detecting unit detects that the output current of the driving module decreases, the voltage outputted by the protection module to the same direction of the first comparator is synchronously reduced.
  • the protection module is a voltage regulator whose output voltage is continuously adjustable, and a function relationship is established between the output voltage of the voltage regulator and the detected current value.
  • a driving method of the above LED backlight driving circuit comprising the steps of:
  • a liquid crystal display device comprising the above-described LED backlight driving circuit.
  • the protection module determines the current load of the LED light bar by detecting the output current of the drive module.
  • the output current of the drive module decreases, the brightness of the LED light bar decreases, and the light load state tends to be light.
  • the output voltage of the LED strip is also reduced, the first comparison with its coupling The voltage at the inverting input of the device will also decrease, and the voltage difference between the inverting input terminal and the first reference voltage will increase.
  • the backlight driving chip will increase the duty ratio and increase the output voltage, resulting in a voltage that is too high at light loads. Reduce the efficiency of the drive module.
  • the backlight driver chip reduces the duty cycle, and lowering the output voltage of the driver module increases the efficiency of the driver module.
  • the protection module is set so that the LED backlight driving circuit has sufficient brightness at any time and has high working efficiency.
  • the voltage at the output end of the LED light bar also increases, and the voltage of the opposite input terminal of the first comparator coupled thereto is also It will increase, the voltage difference between the inverting input and the first reference voltage will be reduced.
  • the backlight driving chip will reduce the duty ratio and reduce the output voltage, resulting in a voltage that is too low when the load is heavy, and the LED strip does not reach the expected level. brightness.
  • the protection module can increase the voltage output to the same comparator at the same end when the output current of the driving module increases, so that the differential pressure between the reverse input terminal and the same input terminal of the first comparator increases. Large, backlight driver chips increase the duty cycle and increase the output voltage of the driver module to achieve the desired brightness of the LED strip.
  • FIG. 1 is a schematic diagram of a conventional LED backlight driving circuit
  • FIG. 2 is a schematic diagram of the principle of the second embodiment of the present invention.
  • FIG. 3 is a schematic diagram of a method according to Embodiments 1 and 2 of the present invention.
  • FIG. 5 is a schematic diagram of a method according to Embodiment 3 of the present invention.
  • Embodiment 4 of the present invention is a schematic diagram of the principle of Embodiment 4 of the present invention.
  • FIG. 7 is a schematic diagram of a method according to Embodiment 4 of the present invention.
  • Figure 9 is a schematic diagram of a method of Embodiment 5 of the present invention. ⁇ detailed description ⁇
  • the LED backlight driving circuit includes an LED light bar and a driving module of the LED light bar.
  • the driving module includes a backlight driving chip for adjusting the output voltage of the driving module, and the backlight driving chip includes a first comparison for correcting the output voltage of the driving module.
  • the output end of the LED strip is coupled to the inverting input of the first comparator; the non-inverting input of the first comparator is coupled with a protection module; and the protection module includes a detecting unit for detecting the output current of the driving module;
  • the protection module When the current value detected by the detecting unit is higher than the preset first current value, the protection module outputs the first reference voltage to the same input end of the first comparator; the current value detected by the detecting unit is lower than the preset first current value The protection module outputs a second reference voltage that is less than the first reference voltage to the non-inverting input of the first comparator.
  • the driving method of the LED backlight driving circuit of the embodiment includes the steps of: detecting an output current of the driving module, and when the current exceeds a preset first current value, the protection module outputs the first reference voltage to the first comparator. The same input; otherwise, the protection module outputs a second reference voltage that is less than the first reference voltage to the non-inverting input of the first comparator.
  • the protection module determines whether the LED light bar is in a light load state by detecting the output current of the driving module, and if the LED light bar works normally, outputs a higher first reference voltage to the backlight driving.
  • the first comparator of the chip if it is in a light load state (ie, lower than the preset first current value), the output voltage of the LED strip is also reduced, and the voltage of the inverting input of the first comparator coupled thereto It will also decrease, and the voltage difference between the inverting input terminal and the first reference voltage will increase.
  • the backlight driving chip will increase the duty ratio and increase the output voltage, resulting in excessive voltage at light load, which reduces the efficiency of the driving module;
  • the protection module can output a second reference voltage lower than the first reference voltage in time when the load is light, so that the voltage difference between the reverse input end and the same input end of the first comparator is reduced, and the backlight drive chip is reduced.
  • the air ratio reduces the output voltage, realizes low-voltage output at light load, and improves the drive module. s efficiency.
  • an LED backlight driving circuit includes an LED light bar 20 and a driving module 10 of the LED light bar 20.
  • the driving module 10 of the LED light bar 20 includes an inductor coupled to the power source, a diode coupled to the inductor, and a diode negative electrode.
  • the driving module 10 includes a backlight driving chip 11 for adjusting the output voltage of the driving module 10,
  • the control terminal of the voltage-regulated controllable switch is coupled to the backlight driving chip 11, the backlight driving chip 11 includes an overcurrent protection pin, the terminal voltage of the voltage dividing resistor is coupled to the protection pin, and the first is for correcting the output voltage of the driving module 10.
  • a comparator U1 an output of the LED strip 20 is coupled to the inverting input of the first comparator U1; a non-inverting input of the first comparator U1 is coupled with a protection module; and the protection module includes means for detecting the output of the driver module 10. Current detection unit.
  • the protection module includes a second comparator, the terminal voltage of the voltage dividing resistor is coupled to the non-inverting input of the second comparator; the inverting input of the second comparator is coupled with the third reference voltage; the first reference voltage and the second reference The voltages are respectively coupled to the two excitation terminals of the second comparator; the output of the second comparator is coupled to the non-inverting input of the first comparator U1;
  • the second comparator When the current value detected by the detecting unit is higher than the preset first current value, the second comparator outputs the first reference voltage; when the current value detected by the detecting unit is lower than the preset first current value, the second comparator outputs The second reference voltage.
  • the reference voltage reference value 0.6V for the first reference voltage, 0.5V for the second reference voltage, and 0.25V for the third reference voltage.
  • the overcurrent protection pin of the backlight driver chip 11 has an overcurrent protection function, which can adjust the output when the output current of the driving module 10 is too large, so as to prevent the LED strip 20 from being burned out.
  • the driving method of the LED backlight driving circuit of the embodiment includes the steps of: detecting an output current of the driving module, and when the current exceeds a preset first current value, the protection module outputs the first reference voltage to the first The non-inverting input of the comparator; otherwise, the protection module output is smaller than the first base A second reference voltage of the quasi-voltage is to the non-inverting input of the first comparator.
  • the driving module 10 uses the topology of the boosting circuit, and the current flowing through the voltage dividing resistor of the boosting circuit has a significant linear relationship with the output current of the driving module 10. Therefore, the end of the voltage dividing resistor can be used.
  • the voltage is coupled to the second comparator to implement the function of the conversion component 32 of the detecting unit of the embodiment.
  • the voltage dividing resistor can complete the function of the boosting circuit and realize the voltage collecting function of the converting component 32, and the circuit is simpler.
  • the high reuse rate of the device helps to reduce costs.
  • an LED backlight driving circuit includes an LED light bar 20 and a driving module of the LED light bar 20.
  • the driving module 10 of the LED light bar 20 includes an inductor coupled to the power source, a diode coupled to the inductor, and a diode negative coupling.
  • the driving module 10 includes a backlight driving chip 11 for adjusting the output voltage of the driving module 10.
  • the control terminal of the voltage controllable switch is coupled to the backlight driving chip 11, and the backlight driving chip 11 includes an overcurrent protection pin, the terminal voltage of the voltage dividing resistor is coupled to the protection pin, and further includes a first circuit for correcting the output voltage of the driving module 10.
  • Comparator U1 the output end of the LED strip 20 is coupled to the inverting input of the first comparator U1; the non-inverting input of the first comparator U1 is coupled with a protection module; and the protection module includes an output current for detecting the driving module 10. Detection unit.
  • the protection module includes a second comparator and a third comparator, the terminal voltages of the voltage dividing resistors are respectively coupled to the non-inverting input terminals of the second comparator and the third comparator; the second comparator is coupled with the third terminal a reference voltage; a first reference voltage and a second reference voltage respectively coupled to the two excitation terminals of the second comparator; an inverting input of the third comparator coupled to the fourth reference voltage, and an output of the second comparator coupled to The excitation end of the third comparator; the other excitation end of the third comparator is coupled with a fifth reference voltage; the fourth reference voltage is greater than the third reference voltage; the fifth reference voltage is greater than the first reference voltage;
  • the third comparator When the current value detected by the detecting unit is higher than the preset second current value, the third comparator outputs the fifth base The quasi-voltage is coupled to the non-inverting input of the first comparator U1; the second current value is greater than the first current value.
  • the reference voltage reference value 0.6V for the first reference voltage, 0.5V for the second reference voltage, 0.25V for the third reference voltage, 0.45V for the fourth reference voltage, and 0.7V for the fifth reference voltage. This is a specific reference voltage value, which can be applied to the backlight drive of different types of liquid crystal display devices.
  • the overcurrent protection pin of the backlight driver chip 11 has an overcurrent protection function, which can adjust the output when the output current of the driving module 10 is too large, so as to prevent the LED strip 20 from being burned out.
  • the voltage of the protection pin CS of the backlight driving chip i.e., the terminal voltage of the voltage dividing resistor
  • the protection pin CS voltage is equal to 0.25V (the third reference voltage) as a criterion for determining whether the LED strip is lightly loaded.
  • the protection pin CS voltage is equal to 0.45V (fourth reference voltage) as the judgment condition for whether the LED strip is overloaded:
  • the protection pin CS voltage is ⁇ 0.25 ⁇
  • the second comparator U2 outputs the second reference voltage 0.5V
  • the third comparator U3 also outputs the second reference voltage 0.5V
  • the first comparator The voltage of the LED-LV of the non-inverting input terminal of U1 is 0.5V, and the duty ratio of the output signal of the driving pin G of the backlight driving chip is reduced by the action of the first comparator U1, thereby reducing the output voltage of the driving module.
  • the protection pin CS voltage is >0.45V
  • the second comparator U2 outputs the first reference voltage 0.6V
  • the third comparator U3 outputs the fifth reference voltage 0.7V
  • the first comparator U1 The voltage of the LED-LV of the same input terminal is 0.7V, and the duty ratio of the output signal of the driving driver pin G of the backlight driving chip is increased by the action of the first comparator U1, thereby increasing the output voltage of the driving module.
  • the driving module 10 of the present embodiment also uses the topology of the boosting circuit, and the current flowing through the voltage dividing resistor of the boosting circuit has a significant linear relationship with the output current of the driving module 10, so the terminal voltage of the voltage dividing resistor can be used. Coupling to the second comparator and the third comparator, the function of the conversion component 32 of the detecting unit of the embodiment is realized, so that the voltage dividing resistor can complete the function of the boosting circuit and realize the electricity of the converting component 32.
  • the compression set function, the circuit is simpler, and the device reuse rate is high, which is beneficial to reduce the cost.
  • the embodiment adds the function of the heavy load adjustment on the basis of the second embodiment, and expands the function of the protection module.
  • the existing drive module 10 outputs a heavy load (the current is large, the brightness of the LED light bar 20 is high)
  • the voltage at the output of the LED strip 20 is increased, and the voltage at the inverting input of the first comparator coupled thereto is also increased, and the voltage difference between the inverting input and the first reference voltage is reduced.
  • Chip 11 will reduce the duty cycle to reduce the output voltage, causing the voltage not to go up when the load is heavy, so the LED light bar 20 will not reach the expected brightness; and the protection module can output a higher than the first reference voltage in time for heavy load.
  • the fifth reference voltage so that the voltage difference between the inverting input terminal and the non-inverting input terminal of the first comparator increases, and the backlight driving chip 11 increases the duty ratio to increase the output voltage, thereby achieving high voltage output during heavy load, ensuring the LED light.
  • Bar 20 achieves the desired brightness.
  • more comparators can be added to achieve more precise control, in which a plurality of preset current values are picked up in a change interval of the current of the driving module, and each current value corresponds to one reference voltage.
  • the corresponding comparator detects that the output current of the driving module exceeds or falls below the corresponding preset current value, the corresponding reference voltage is output, so that the first comparator can have multiple sets of reference voltages, which can be selected according to the driving module.
  • the output current variation enables more precise regulation, further optimizing the performance of the backlight driver module.
  • a driving method of the LED backlight driving circuit of this embodiment includes the following steps: presetting a first current value, a second current value greater than the first current value, detecting an output current of the driving module, and when the current exceeds a preset first current value, the protection module outputs the first reference voltage to the first a non-inverting input of the comparator; otherwise, the protection module outputs a second reference voltage that is less than the first reference voltage to the non-inverting input of the first comparator; and when detecting that the output current of the driving module is greater than the second current value, the protection The module outputs a fifth reference voltage greater than the first reference voltage to the non-inverting input of the first comparator.
  • the fifth reference voltage is greater than the first reference voltage; the first reference voltage is greater than the second reference voltage.
  • an LED backlight driving circuit includes a driving module of an LED light bar and an LED light bar, a driving module for adjusting a backlight driving chip of a driving module output voltage, an inductance coupled with a power source, and a power
  • the coupled diode is coupled to the input end of the LED strip, the anode of the diode and the ground of the power supply are sequentially connected in series with a voltage-controlled switch and a voltage dividing resistor, and the control end of the voltage-controlled switch is coupled to the backlight a driving chip
  • the backlight driving chip includes an overcurrent protection pin, a first comparator for correcting an output voltage of the driving module, and an output end of the LED light bar is coupled to an inverting input end of the first comparator;
  • a protection module with a variable output voltage is coupled to the input.
  • the protection module includes a third comparator and a detection unit for detecting the output current of the drive module.
  • the detecting unit includes a conversion component that converts the detected current value into a voltage value, the conversion component is coupled to the non-inverting input of the third comparator; the inverting input of the third comparator is coupled with the fourth reference voltage; the first reference The voltage and the fifth reference voltage are respectively coupled to the two excitation terminals of the third comparator; the output of the third comparator is coupled to the non-inverting input of the first comparator;
  • the conversion component and the voltage dividing resistor can be multiplexed, that is, the terminal voltage of the voltage dividing resistor is coupled to the non-inverting input terminal of the third comparator, and is also coupled to the protection pin of the backlight driving chip.
  • the terminal voltage of the voltage dividing resistor When the current value of the voltage dividing resistor is lower than the preset second current value, the terminal voltage of the voltage dividing resistor is smaller than the fourth reference voltage, and the third comparator outputs the first reference voltage; the current value of the voltage dividing resistor is higher than the preset value When the second current value is, the terminal voltage of the voltage dividing resistor is greater than the fourth reference voltage, and the third comparator outputs the fifth reference voltage.
  • the reference voltage reference value 0.6V for the first reference voltage, 0.45V for the fourth reference voltage, and 0.7V for the fifth reference voltage. This is a specific reference voltage value, which can be applied to the backlight driving of different types of liquid crystal display devices.
  • the driving method of the LED backlight driving circuit of the embodiment includes the steps of: detecting an output current of the driving module, and when the output current is lower than the preset first current value, the protection module outputs the first reference voltage to the first The non-inverting input of the comparator; otherwise, the protection module outputs a fifth reference voltage greater than the first reference voltage to the non-inverting input of the first comparator.
  • the protection module determines whether the LED light bar is in a heavy load state by detecting the output current of the driving module, and if the LED light bar works normally, outputs a lower first reference voltage to the backlight driving.
  • the first comparator of the chip if it is in a heavy state (ie, it is beyond the preset The second current value), the voltage at the output of the LED strip is also increased, and the voltage at the inverting input of the first comparator coupled thereto is also increased, and the voltage difference between the inverting input and the first reference voltage is Zooming out, at this time, the backlight driver chip will reduce the duty cycle to lower the output voltage, causing the voltage to be too low when the load is heavy, and the LED light bar will not reach the expected brightness; and the protection module can output a higher than the first reference voltage in time when heavy The fifth reference voltage, so that the voltage difference between the inverting input terminal and the non-inverting input terminal of the first comparator increases, and the backlight driving chip increases the duty
  • the LED backlight driving circuit includes an LED light bar 20 and a driving module 10 of the LED light bar 20.
  • the driving module 10 includes a backlight driving chip 11 for adjusting the output voltage of the driving module 10, and the backlight driving chip 11 includes a driving for correcting the driving.
  • the first comparator U1 of the output voltage of the module 10, the output end of the LED strip 20 is coupled to the inverting input of the first comparator U1; the non-inverting input of the first comparator U1 is coupled with a protection module with variable output voltage 30;
  • the protection module 30 includes a detection unit 31 for detecting the output current of the driving module 10; when the detection unit 31 detects that the output current of the driving module 10 is increased, the voltage output by the protection module 30 to the same end of the first comparator U1 is increased; When the unit 31 detects that the output current of the driving module 10 decreases, the voltage output from the protection module 30 to the same end of the first comparator U1 decreases.
  • this embodiment further discloses a driving method for the LED backlight driving circuit, which includes the following steps:
  • the protection module 30 determines whether the LED light bar 20 is in a light load or heavy load state by detecting the output current of the drive module 10, when the output of the drive module 10 is When the flow is reduced, that is, the brightness of the LED light bar 20 is lowered, and the light load state is reached, and the voltage at the output end of the LED light bar 20 is also lowered, and the voltage of the opposite input terminal of the first comparator U1 coupled thereto is also lowered. The voltage difference between the inverting input terminal and the first reference voltage is increased. At this time, the backlight driving chip 11 increases the duty ratio to increase the output voltage, causing the voltage to be too high at light load, thereby reducing the efficiency of the driving module 10.
  • the protection module 30 can reduce the voltage output to the same end of the first comparator U1 when the output current of the driving module 10 decreases, so that the voltage difference between the inverting input terminal and the non-inverting input terminal of the first comparator U1 is reduced. Accordingly, the backlight driving chip 11 reduces the duty ratio, and lowering the output voltage of the driving module 10 improves the efficiency of the driving module 10.
  • the output voltage of the LED light bar 20 increases, that is, the brightness of the LED light bar 20 rises and tends to be in a heavy load state
  • the output voltage of the LED light bar 20 also increases, and the reverse of the first comparator U1 coupled thereto
  • the voltage at the input terminal will also increase, and the voltage difference between the inverting input terminal and the first reference voltage will be reduced.
  • the backlight driving chip 11 will lower the duty ratio and lower the output voltage, resulting in a voltage that is too low during heavy load, and the LED strip 20 does not reach the expected brightness.
  • the backlight driving chip 11 increases the duty ratio, increases the output voltage of the driving module 10, and causes the LED strip 20 to reach a desired brightness.
  • the protection module of the embodiment can select a voltage regulator with continuously adjustable output voltage, and establish a functional relationship between the output voltage of the voltage regulator and the detected current value, so that the output voltage of the protection module can follow the current synchronization of the driving module. Or synchronous reduction.

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Abstract

一种LED背光驱动电路包括LED灯条（20）、LED灯条（20）的驱动模块，驱动模块包括用于调整驱动模块输出电压的背光驱动芯片（11），背光驱动芯片（11）包括用于校正驱动模块输出电压的第一比较器（U1），LED灯条（20）的输出端耦合到第一比较器（U1）的反相输入端；第一比较器（U1）的同相输入端耦合有保护模块；保护模块包括用于检测驱动模块输出电流的检测单元；检测单元检测的电流值高于预设的第一电流值时，保护模块输出第一基准电压到第一比较器（U1）的同相输入端；检测单元检测的电流值低于预设的第一电流值时，保护模块输出小于第一基准电压的第二基准电压到第一比较器（U1）的同相输入端。

Description

一种 LED背光驱动电路
【技术领域】
本发明涉及液晶显示领域， 更具体的说， 涉及一种 LED背光驱动电路。 【背景技术】
现有液晶显示装置多釆用 LED作为背光源， 具体做法是将多颗 LED灯串 接形成 LED灯条， 然后将 LED灯条耦合到一升压电路。 参见图 1 , 升压电路的 可控开关 Q耦合到一背光驱动芯片 IC,根据调整背光驱动芯片驱动引脚 G输出 信号的占空比就能调节升压电路的输出电压， 从而实现 LED灯条的调光。 如果 LED灯条有多条， 可以并联设置耦合到同一升压电路。 背光驱动芯片内部设有 比较器， 每条 LED灯条的输出端耦合到比较器的反向输入端； 比较器的同向输 入端耦合到一基准电压， 比较器根据基准电压跟各 LED灯条的压差来调整背光 驱动芯片输出信号的占空比， 从而实现调光目的。 现有的背光驱动模块存在电 路性能不佳的问题， 比如在 LED灯条轻载（LED灯条亮度较低）时仍然输出较 大的电压， 造成背光驱动的效率降低； 或在 LED重载（LED灯条亮度较高）时 输出电压较低， LED灯条达不到预期的亮度。
【发明内容】
本发明所要解决的技术问题之一是提供一种可在 LED灯条轻载时提升背光 驱动效率的 LED背光驱动电路。
本发明的目的是通过以下技术方案来实现的：
一种 LED背光驱动电路， 包括 LED灯条、 LED灯条的驱动模块， 所述驱 动模块包括用于调整驱动模块输出电压的背光驱动芯片， 所述背光驱动芯片包 括用于校正驱动模块输出电压的第一比较器， 所述 LED灯条的输出端耦合到所 述第一比较器的反向输入端； 所述第一比较器的同向输入端耦合有保护模块； 所述保护模块包括用于检测所述驱动模块输出电流的检测单元； 所述检测单元检测的电流值高于预设的第一电流值时， 所述保护模块输出 第一基准电压到所述第一比较器的同向输入端； 所述检测单元检测的电流值低 于预设的第一电流值时， 所述保护模块输出小于第一基准电压的第二基准电压 到所述第一比较器的同向输入端。
进一步的， 所述保护模块包括第二比较器， 所述检测单元包括将检测到的 电流值转换为电压值的转换组件， 所述转换组件耦合到第二比较器的同向输入 端； 所述第二比较器的反向输入端耦合有第三基准电压； 所述第一基准电压和 第二基准电压分别耦合到所述第二比较器的两个激励端； 所述第二比较器的输 出端耦合到所述第一比较器的同向输入端；
所述检测单元检测的电流值高于预设的第一电流值时， 所述第二比较器输 出第一基准电压； 所述检测单元检测的电流值低于预设的第一电流值时， 所述 第二比较器输出第二基准电压。 此为一种具体的保护模块的电路结构。 将釆集 的电流信息转化为电压信息， 与第二比较器的另一输入端的第三基准电压比较， 从而判断输出第一基准电压还是第二基准电压。
进一步的， 所述 LED灯条的驱动模块包括与电源耦合的电感、 与电感耦合 的二极管， 二极管负极耦合到所述 LED灯条的输入端， 所述二极管的正极和电 源接地端之间依次串联有调压可控开关和分压电阻， 所述调压可控开关的控制 端耦合到所述背光驱动芯片， 所述分压电阻的端电压耦合到所述第二比较器的 同向输入端。 此为一种釆用升压电路的驱动模块拓朴结构， 流经该升压电路分 压电阻的电流跟驱动模块的输出电流有明显的线性关系， 因此可以将分压电阻 的端电压耦合到第二比较器， 实现检测单元的转换组件的功能， 这样分压电阻 既可以完成升压电路的功能， 又能实现转换组件的电压釆集功能， 电路更简单， 器件复用率高， 有利于降低成本。
进一步的， 所述保护模块还包括第三比较器， 所述检测单元的转换组件耦 合到所述第三比较器的同向输入端， 所述第三比较器的反向输入端耦合有第四 基准电压， 所述第二比较器的输出端耦合到所述第三比较器的激励端； 所述第 三比较器的另一激励端耦合有第五基准电压； 所述第四基准电压大于所述第三 基准电压； 所述第五基准电压大于所述第一基准电压；
所述检测单元检测的电流值高于预设的第二电流值时， 所述第三比较器输 出第五基准电压耦合到所述第一比较器的同向输入端； 所述第二电流值大于所 述第一电流值。 本技术方案拓展了保护模块的功能， 现有的驱动模块输出重载 时（电流较大， LED灯条亮度较高时）， LED灯条的输出端电压增大， 与其耦合 的第一比较器的反向输入端的电压也会增加， 反向输入端跟第一基准电压之间 的压差会减小， 此时背光驱动芯片会减小占空比降低输出电压， 造成重载时电 压上不去， 因此 LED灯条达不到预期的亮度； 而保护模块可以在重载时及时输 出一个高于第一基准电压的第五基准电压， 这样第一比较器反向输入端和同向 输入端的压差随之增加， 背光驱动芯片会加大占空比提高输出电压， 实现重载 时高压输出， 确保 LED灯条达到预期的亮度。
进一步的， 所述 LED灯条的驱动模块包括与电源耦合的电感、 与电感耦合 的二极管， 二极管负极耦合到所述 LED灯条的输入端， 所述二极管的正极和电 源接地端之间依次串联有调压可控开关和分压电阻， 所述调压可控开关的控制 端耦合到所述背光驱动芯片， 所述分压电阻的端电压分别耦合到所述第二比较 器和第三比较器的同向输入端。 此为一种釆用升压电路的驱动模块拓朴结构， 流经该升压电路分压电阻的电流跟驱动模块的输出电流有明显的线性关系， 因 此可以将分压电阻的端电压耦合到第二比较器和第三比较器， 实现检测单元的 转换组件的功能， 这样分压电阻既可以完成升压电路的功能， 又能实现转换组 件的电压釆集功能， 电路更简单， 器件复用率高， 有利于降低成本。
进一步的， 所述第一基准电压选用 0.6V、 第二基准电压选用 0.5V、 第三基 准电压选用 0.25V、 第四基准电压选用 0.45V、 第五基准电压选用 0.7V。 此为一 种具体的基准电压数值， 釆用该组数值， 可以适用于不同种类液晶显示装置的 背光驱动。
进一步的， 所述背光驱动芯片包括过流保护引脚， 所述分压电阻的端电压 耦合到所述保护引脚。 背光驱动芯片增加过流保护功能， 可以在驱动模块输出 电流过大时调整输出， 避免 LED灯条被烧坏。
进一步的， 所述 LED灯条的驱动模块包括与电源耦合的电感、 与电感耦合 的二极管， 二极管负极耦合到所述 LED灯条的输入端， 所述二极管的正极和电 源接地端之间依次串联有调压可控开关和分压电阻， 所述检测单元为所述分压 电阻， 所述调压可控开关的控制端耦合到所述背光驱动芯片， 所述保护模块还 包括第三比较器， 所述分压电阻的端电压分别耦合到所述第二比较器和第三比 较器的同向输入端， 所述第三比较器的反向输入端耦合有第四基准电压， 所述 第二比较器的输出端耦合到所述第三比较器的激励端； 所述第三比较器的另一 激励端耦合有第五基准电压； 所述第四基准电压大于所述第三基准电压； 所述 第五基准电压大于所述第一基准电压。
此为一种具体的 LED背光驱动电路， 釆用升压电路的驱动模块拓朴结构， 流经该升压电路分压电阻的电流跟驱动模块的输出电流有明显的线性关系， 因 此可以将分压电阻的端电压耦合到第二比较器和第三比较器的同向端， 实现检 测单元的功能， 这样分压电阻既可以完成升压电路的功能， 又能实现转换组件 的电压釆集功能， 电路更简单， 器件复用率高， 有利于降低成本。
一种上述的 LED背光驱动电路的驱动方法， 包括步骤：
检测驱动模块的输出电流， 当电流超出预设的第一电流值时， 保护模块输 出第一基准电压到第一比较器的同向输入端； 否则， 保护模块输出小于第一基 准电压的第二基准电压到所述第一比较器的同向输入端。
进一步的， 所述驱动方法还包括设置大于第一电流值的第二电流值， 当检 测到驱动模块的输出电流大于第二电流值时， 保护模块输出大于第一基准电压 的第五基准电压到第一比较器的同向输入端。 本技术方案拓展了保护模块的功 能， 现有的驱动模块输出重载时（电流较大， LED灯条亮度较高时）， LED灯条 的输出端电压增大， 与其耦合的第一比较器的反向输入端的电压也会增加， 反 向输入端跟第一基准电压之间的压差会减小， 此时背光驱动芯片会减小占空比 降低输出电压， 造成重载时电压上不去， 因此 LED灯条达不到预期的亮度； 而 保护模块可以在重载时及时输出一个高于第一基准电压的第五基准电压， 这样 第一比较器反向输入端和同向输入端的压差随之增加， 背光驱动芯片会加大占 空比提高输出电压， 实现重载时高压输出， 确保 LED灯条达到预期的亮度。
一种液晶显示装置， 包括上述的一种 LED背光驱动电路。
本发明由于釆用了保护模块， 保护模块通过检测驱动模块的输出电流来判 断 LED灯条是否处于轻载状态，如果 LED灯条正常工作，则输出一个较高的第 一基准电压给背光驱动芯片的第一比较器； 如果是轻载状态 （即低于预设的第 一电流值）， LED灯条的输出端电压也随之降低， 与其耦合的第一比较器的反向 输入端的电压也会降低， 反向输入端跟第一基准电压之间的压差会增加， 此时 背光驱动芯片会提高占空比提高输出电压， 造成轻载时电压过高， 降低了驱动 模块的效率； 而保护模块可以在轻载时及时输出一个低于第一基准电压的第二 基准电压， 这样第一比较器反向输入端和同向输入端的压差随之降低， 背光驱 动芯片会减小占空比降低输出电压， 实现轻载时低压输出， 提高了驱动模块的 效率。
本发明所要解决的技术问题之二是提供一种可在 LED灯条重载时稳定 LED 灯条亮度的背光驱动效率的 LED背光驱动电路。
本发明的目的是通过以下技术方案来实现的：
一种 LED背光驱动电路， 包括 LED灯条、 LED灯条的驱动模块， 所述驱 动模块包括用于调整驱动模块输出电压的背光驱动芯片， 所述背光驱动芯片包 括用于校正驱动模块输出电压的第一比较器， 所述 LED灯条的输出端耦合到所 述第一比较器的反向输入端； 所述第一比较器的同向输入端耦合有输出电压可 变的保护模块；
所述保护模块包括用于检测所述驱动模块输出电流的检测单元；
所述检测单元检测的电流值低于预设的第二电流值时， 所述保护模块输出 第一基准电压到所述第一比较器的同向输入端； 所述检测单元检测的电流值高 于预设的第二电流值时， 所述保护模块输出大于第一基准电压的第五基准电压 到所述第一比较器的同向输入端。
进一步的， 所述保护模块包括第三比较器， 所述检测单元包括将检测到的 电流值转换为电压值的转换组件， 所述转换组件耦合到第三比较器的同向输入 端； 所述第三比较器的反向输入端耦合有第四基准电压； 所述第一基准电压和 第五基准电压分别耦合到所述第三比较器的两个激励端； 所述第三比较器的输 出端耦合到所述第一比较器的同向输入端；
所述检测单元检测的电流值低于预设的第二电流值时， 所述第三比较器输 出第一基准电压； 所述检测单元检测的电流值高于预设的第二电流值时， 所述 第三比较器输出第五基准电压。 此为一种具体的保护模块的电路结构。 将釆集 的电流信息转化为电压信息， 与第三比较器的另一输入端的第五基准电压比较， 从而判断输出第一基准电压还是第五基准电压。
进一步的， 所述背光驱动芯片包括过流保护引脚； 所述 LED灯条的驱动模 块包括与电源耦合的电感、 与电感耦合的二极管， 二极管负极耦合到所述 LED 灯条的输入端， 所述二极管的正极和电源接地端之间依次串联有调压可控开关 和分压电阻， 所述调压可控开关的控制端耦合到所述背光驱动芯片， 所述分压 电阻的端电压分别耦合到所述第三比较器的同向输入端和所述背光驱动芯片的 保护引脚。 此为一种釆用升压电路的驱动模块拓朴结构， 流经该升压电路分压 电阻的电流跟驱动模块的输出电流有明显的线性关系， 因此可以将分压电阻的 端电压耦合到第三比较器， 实现检测单元的转换组件的功能， 这样分压电阻既 可以完成升压电路的功能， 又能实现转换组件的电压釆集功能， 电路更简单， 器件复用率高， 有利于降低成本。 背光驱动芯片增加过流保护功能， 可以在驱 动模块输出电流过大时调整输出， 避免 LED灯条被烧坏。
进一步的， 所述第一基准电压选用 0.6V、 第四基准电压选用 0.45V、 第五 基准电压选用 0.7V。 此为一种具体的基准电压数值， 釆用该组数值， 可以适用 于不同种类液晶显示装置的背光驱动。 进一步的， 所述背光驱动芯片包括过流保护引脚； 所述 LED灯条的驱动模 块包括与电源耦合的电感、 与电感耦合的二极管， 二极管负极耦合到所述 LED 灯条的输入端， 所述二极管的正极和电源接地端之间依次串联有调压可控开关 和分压电阻， 所述检测单元为所述分压电阻， 所述调压可控开关的控制端耦合 到所述背光驱动芯片， 所述保护模块包括第三比较器， 所述分压电阻的端电压 分别耦合到所述第三比较器的同向输入端和所述背光驱动芯片的保护引脚； 所 述检测单元包括将检测到的电流值转换为电压值的转换组件， 所述转换组件耦 合到第三比较器的同向输入端； 所述第三比较器的反向输入端耦合有第四基准 电压； 所述第一基准电压和第五基准电压分别耦合到所述第三比较器的两个激 励端； 所述第三比较器的输出端耦合到所述第一比较器的同向输入端。
此为一种具体的 LED背光驱动电路， 釆用升压电路的驱动模块拓朴结构， 流经该升压电路分压电阻的电流跟驱动模块的输出电流有明显的线性关系， 因 此可以将分压电阻的端电压耦合到第三比较器的同向端， 实现检测单元的功能， 这样分压电阻既可以完成升压电路的功能， 又能实现转换组件的电压釆集功能 , 电路更简单， 器件复用率高， 有利于降低成本。
一种上述的 LED背光驱动电路的驱动方法， 包括步骤：
检测驱动模块的输出电流， 当输出电流低于预设的第一电流值时， 保护模 块输出第一基准电压到第一比较器的同向输入端； 否则， 保护模块输出大于第 一基准电压的第五基准电压到所述第一比较器的同向输入端。
一种液晶显示装置， 包括上述的一种 LED背光驱动电路。
本发明由于釆用了保护模块， 保护模块通过检测驱动模块的输出电流来判 断 LED灯条是否处于重载状态，如果 LED灯条正常工作，则输出一个较低的第 一基准电压给背光驱动芯片的第一比较器； 如果是重载状态 （即超出预设的第 二电流值）， LED灯条的输出端电压也随之增加， 与其耦合的第一比较器的反向 输入端的电压也会增加， 反向输入端跟第一基准电压之间的压差会缩小， 此时 背光驱动芯片会降低占空比降低输出电压， 造成重载时电压过低， LED灯条达 不到预期的亮度； 而保护模块可以在重时及时输出一个高于第一基准电压的第 五基准电压， 这样第一比较器反向输入端和同向输入端的压差随之增加， 背光 驱动芯片会增大占空比提高输出电压，提高驱动模块重载时的输出电压，使 LED 灯条达到预期的亮度。
本发明所要解决的技术问题之三是提供一种提高 LED灯条驱动模块的电路 性能的 LED背光驱动电路。
本发明的目的是通过以下技术方案来实现的：
一种 LED背光驱动电路， 包括 LED灯条、 LED灯条的驱动模块， 所述驱 动模块包括用于调整驱动模块输出电压的背光驱动芯片， 所述背光驱动芯片包 括用于校正驱动模块输出电压的第一比较器， 所述 LED灯条的输出端耦合到所 述第一比较器的反向输入端； 所述第一比较器的同向输入端耦合有输出电压可 变的保护模块；
所述保护模块包括用于检测所述驱动模块输出电流的检测单元； 检测单元 检测到所述驱动模块的输出电流增大时， 所述保护模块输出到第一比较器同向 端的电压同步增大； 检测单元检测到所述驱动模块的输出电流减小时， 所述保 护模块输出到第一比较器同向端的电压同步减小。
进一步的， 所述保护模块为输出电压连续可调的调压器， 所述调压器的输 出电压和检测到的电流值之间建立有函数关系。
一种上述 LED背光驱动电路的驱动方法， 包括步骤：
检测驱动模块的输出电流， 当输出电流增大时， 保护模块输出到第一比较 器的同向输入端的电压同步增大； 当输出电流减小时， 保护模块输出到第一比 较器的同向输入端的电压同步减小。
一种液晶显示装置， 包括上述的一种 LED背光驱动电路。
本发明由于釆用了保护模块， 保护模块通过检测驱动模块的输出电流来判 断 LED灯条当前的负载，当驱动模块的输出电流减小时，即 LED灯条亮度降低， 趋于轻载状态， 此时 LED灯条的输出端电压也随之降低， 与其耦合的第一比较 器的反向输入端的电压也会降低， 反向输入端跟第一基准电压之间的压差会增 加， 此时背光驱动芯片会提高占空比提高输出电压， 造成轻载时电压过高， 降 低了驱动模块的效率。 此时保护模块可以在驱动模块的输出电流减小时， 输出 到第一比较器同向端的电压也随之减 d、， 这样第一比较器反向输入端和同向输 入端的压差随之降低， 背光驱动芯片会减小占空比， 降低驱动模块的输出电压 提高了驱动模块的效率。 保护模块的设置， 使得 LED背光驱动电路随时都具有 足够的亮度， 且具有较高的工作效率。
当驱动模块的输出电流增大时，即 LED灯条亮度升高，趋于重载状态， LED 灯条的输出端电压也随之增加， 与其耦合的第一比较器的反向输入端的电压也 会增加， 反向输入端跟第一基准电压之间的压差会缩小， 此时背光驱动芯片会 降低占空比降低输出电压， 造成重载时电压过低， LED灯条达不到预期的亮度。 此时保护模块可以在驱动模块的输出电流增大时， 输出到第一比较器同向端的 电压也随之增大， 这样第一比较器反向输入端和同向输入端的压差随之增大， 背光驱动芯片会提高占空比， 增加驱动模块的输出电压， 使 LED灯条达到预期 的亮度。
【附图说明】
图 1是现有的一种 LED背光驱动电路示意图;
图 2是本发明实施例二的原理示意图；
图 3是本发明实施例一、 二的方法示意图；
图 4是本发明实施例三的原理示意图；
图 5是本发明实施例三的方法示意图；
图 6是本发明实施例四的原理示意图；
图 7是本发明实施例四的方法示意图；
图 8是本发明实施例一、 五的原理示意图；
图 9是本发明实施例五的方法示意图。 【具体实施方式】
实施例一
本实施例公开一种液晶显示装置， 液晶显示装置包括 LED背光驱动电路。 参见图 8, LED背光驱动电路包括 LED灯条、 LED灯条的驱动模块， 驱动模块 包括用于调整驱动模块输出电压的背光驱动芯片， 背光驱动芯片包括用于校正 驱动模块输出电压的第一比较器， LED灯条的输出端耦合到第一比较器的反向 输入端； 第一比较器的同向输入端耦合有保护模块； 保护模块包括用于检测驱 动模块输出电流的检测单元；
检测单元检测的电流值高于预设的第一电流值时， 保护模块输出第一基准 电压到第一比较器的同向输入端； 检测单元检测的电流值低于预设的第一电流 值时 , 保护模块输出小于第一基准电压的第二基准电压到第一比较器的同向输 入端。
参见图 3 , 本实施例的 LED背光驱动电路的驱动方法， 包括步骤： 检测驱动模块的输出电流， 当电流超出预设的第一电流值时， 保护模块输 出第一基准电压到第一比较器的同向输入端； 否则， 保护模块输出小于第一基 准电压的第二基准电压到所述第一比较器的同向输入端。
本实施例由于釆用了保护模块， 保护模块通过检测驱动模块的输出电流来 判断 LED灯条是否处于轻载状态，如果 LED灯条正常工作，则输出一个较高的 第一基准电压给背光驱动芯片的第一比较器； 如果是轻载状态 （即低于预设的 第一电流值）， LED灯条的输出端电压也随之降低， 与其耦合的第一比较器的反 向输入端的电压也会降低， 反向输入端跟第一基准电压之间的压差会增加， 此 时背光驱动芯片会提高占空比提高输出电压， 造成轻载时电压过高， 降低了驱 动模块的效率； 而保护模块可以在轻载时及时输出一个低于第一基准电压的第 二基准电压， 这样第一比较器反向输入端和同向输入端的压差随之降低， 背光 驱动芯片会减小占空比降低输出电压， 实现轻载时低压输出， 提高了驱动模块 的效率。
实施例二
本实施例公开一种液晶显示装置， 液晶显示装置包括 LED背光驱动电路。 参见图 2, —种 LED背光驱动电路， 包括 LED灯条 20、 LED灯条 20的驱动模 块 10, LED灯条 20的驱动模块 10包括与电源耦合的电感、 与电感耦合的二极 管， 与二极管负极耦合到 LED灯条 20的输入端， 二极管的正极和电源接地端 之间依次串联有调压可控开关和分压电阻； 驱动模块 10包括用于调整驱动模块 10输出电压的背光驱动芯片 11 ,调压可控开关的控制端耦合到背光驱动芯片 11 , 背光驱动芯片 11包括过流保护引脚， 分压电阻的端电压耦合到保护引脚， 还包 括用于校正驱动模块 10输出电压的第一比较器 Ul ; LED灯条 20的输出端耦合 到第一比较器 U1的反向输入端；第一比较器 U1的同向输入端耦合有保护模块； 保护模块包括用于检测驱动模块 10输出电流的检测单元。
保护模块包括第二比较器， 分压电阻的端电压耦合到第二比较器的同向输 入端； 第二比较器的反向输入端耦合有第三基准电压； 第一基准电压和第二基 准电压分别耦合到第二比较器的两个激励端； 第二比较器的输出端耦合到第一 比较器 U1的同向输入端；
当检测单元检测的电流值高于预设的第一电流值时， 第二比较器输出第一 基准电压； 检测单元检测的电流值低于预设的第一电流值时， 第二比较器输出 第二基准电压。
基准电压参考取值： 第一基准电压选用 0.6V、 第二基准电压选用 0.5V、 第 三基准电压选用 0.25V。
背光驱动芯片 11 的过流保护引脚具有过流保护功能， 可以在驱动模块 10 输出电流过大时调整输出， 避免 LED灯条 20被烧坏。
如图 3所示， 本实施例的 LED背光驱动电路的驱动方法， 包括步骤： 检测驱动模块的输出电流， 当电流超出预设的第一电流值时， 保护模块输 出第一基准电压到第一比较器的同向输入端； 否则， 保护模块输出小于第一基 准电压的第二基准电压到所述第一比较器的同向输入端。
本实施例中， 驱动模块 10釆用升压电路的拓朴结构， 流经该升压电路分压 电阻的电流跟驱动模块 10的输出电流有明显的线性关系， 因此可以将分压电阻 的端电压耦合到第二比较器， 实现本实施例检测单元的转换组件 32的功能， 这 样分压电阻既可以完成升压电路的功能，又能实现转换组件 32的电压釆集功能 , 电路更简单， 器件复用率高， 有利于降低成本。 检测单元检测的电流值高于预 设的第一电流值时， 第二比较器输出第一基准电压； 检测单元检测的电流值低 于预设的第一电流值时， 第二比较器输出第二基准电压。
实施例三
本实施例公开一种液晶显示装置， 液晶显示装置包括 LED背光驱动电路。 参见图 4, 一种 LED背光驱动电路， 包括 LED灯条 20、 LED灯条 20的驱动模 块， LED灯条 20的驱动模块 10包括与电源耦合的电感、 与电感耦合的二极管， 与二极管负极耦合到 LED灯条 20的输入端， 二极管的正极和电源接地端之间 依次串联有调压可控开关和分压电阻； 驱动模块 10 包括用于调整驱动模块 10 输出电压的背光驱动芯片 11 , 调压可控开关的控制端耦合到背光驱动芯片 11 , 背光驱动芯片 11包括过流保护引脚， 分压电阻的端电压耦合到保护引脚， 还包 括用于校正驱动模块 10输出电压的第一比较器 Ul ; LED灯条 20的输出端耦合 到第一比较器 U1的反向输入端；第一比较器 U1的同向输入端耦合有保护模块； 保护模块包括用于检测驱动模块 10输出电流的检测单元。
保护模块包括第二比较器和第三比较器， 分压电阻的端电压分别耦合到第 二比较器和第三比较器的同向输入端； 第二比较器的反向输入端耦合有第三基 准电压； 第一基准电压和第二基准电压分别耦合到第二比较器的两个激励端； 第三比较器的反向输入端耦合有第四基准电压， 第二比较器的输出端耦合到第 三比较器的激励端； 第三比较器的另一激励端耦合有第五基准电压； 第四基准 电压大于第三基准电压； 第五基准电压大于第一基准电压；
检测单元检测的电流值高于预设的第二电流值时， 第三比较器输出第五基 准电压耦合到第一比较器 Ul的同向输入端； 第二电流值大于第一电流值。
基准电压参考取值： 第一基准电压选用 0.6V、 第二基准电压选用 0.5V、 第 三基准电压选用 0.25V、 第四基准电压选用 0.45V、 第五基准电压选用 0.7V。 此 为一种具体的基准电压数值， 釆用该组数值， 可以适用于不同种类液晶显示装 置的背光驱动。
背光驱动芯片 11 的过流保护引脚具有过流保护功能， 可以在驱动模块 10 输出电流过大时调整输出， 避免 LED灯条 20被烧坏。
假定在正常状态下， 背光驱动芯片的保护引脚 CS的电压 (即分压电阻的端 电压）为 0.35V。 负载 LED灯条轻载时， 驱动模块功率下降， 保护引脚 CS的电 压也随之减小。 以保护引脚 CS电压等于 0.25V (第三基准电压）作为 LED灯条 是否轻载的判断条件。 类似的， 若负载 LED灯条重载时， 以保护引脚 CS电压 等于 0.45V (第四基准电压）作为 LED灯条是否重载的判断条件：
1.当 LED灯条处于正常状态时， 0.25<保护引脚 CS电压 <0.45V, 第二比较 器 U2输出第一基准电压 0.6V, 第三比较器 U3输出第一基准电压 0.6V;
2.当 LED灯条轻载时， 保护引脚 CS电压<0.25¥, 第二比较器 U2输出第二 基准电压 0.5V,第三比较器 U3也输出第二基准电压 0.5V,第一比较器 U1的同 向输入端 LED-LV的电压为 0.5V, 通过第一比较器 U1的作用， 减小背光驱动 芯片驱动引脚 G的输出信号的占空比， 从而使驱动模块的输出电压减小；
3.当 LED灯条重载时， 保护引脚 CS电压 >0.45V, 第二比较器 U2输出第一 基准电压 0.6V,第三比较器 U3输出第五基准电压 0.7V,第一比较器 U1的同向 输入端 LED-LV的电压为 0.7V, 通过第一比较器 U1的作用， 增大背光驱动芯 片驱动引脚 G的输出信号的占空比， 从而使驱动模块的输出电压增大。
本实施的驱动模块 10也釆用升压电路的拓朴结构， 流经该升压电路分压电 阻的电流跟驱动模块 10的输出电流有明显的线性关系， 因此可以将分压电阻的 端电压耦合到第二比较器和第三比较器， 实现本实施例检测单元的转换组件 32 的功能， 这样分压电阻既可以完成升压电路的功能， 又能实现转换组件 32的电 压釆集功能， 电路更简单， 器件复用率高， 有利于降低成本。
本实施例在实施例二的基础上增加了重载调节的功能， 拓展了保护模块的 功能， 现有的驱动模块 10输出重载时（电流较大， LED灯条 20亮度较高时）， LED灯条 20的输出端电压增大，与其耦合的第一比较器的反向输入端的电压也 会增加， 反向输入端跟第一基准电压之间的压差会减小， 此时背光驱动芯片 11 会减小占空比降低输出电压， 造成重载时电压上不去， 因此 LED灯条 20达不 到预期的亮度； 而保护模块可以在重载时及时输出一个高于第一基准电压的第 五基准电压， 这样第一比较器反向输入端和同向输入端的压差随之增加， 背光 驱动芯片 11会加大占空比提高输出电压， 实现重载时高压输出，确保 LED灯条 20达到预期的亮度。 根据本实施例的构思， 还可以增加更多的比较器来实现更 精确的控制， 具体做法是在驱动模块的电流的变化区间拾取多个预设的电流值， 每个电流值对应一个基准电压， 当相应比较器检测到驱动模块的输出电流超过 或低于对应预设的电流值时， 输出对应的基准电压， 这样第一比较器就可以有 多组的基准电压可以选择， 可以根据驱动模块的输出电流变化实现更精确的调 控， 进一步优化背光驱动模块的性能。
参见图 5, 本实施例的 LED背光驱动电路的驱动方法。 包括步骤： 预设第 一电流值、 大于第一电流值的第二电流值， 检测驱动模块的输出电流， 当电流 超出预设的第一电流值时， 保护模块输出第一基准电压到第一比较器的同向输 入端； 否则， 保护模块输出小于第一基准电压的第二基准电压到第一比较器的 同向输入端； 当检测到驱动模块的输出电流大于第二电流值时， 保护模块输出 大于第一基准电压的第五基准电压到第一比较器的同向输入端。 第五基准电压 大于第一基准电压； 第一基准电压大于第二基准电压。
实施例四
本实施例公开一种液晶显示装置， 液晶显示装置包括 LED背光驱动电路。 参见图 6, —种 LED背光驱动电路， 包括 LED灯条、 LED灯条的驱动模块， 驱 动模块用于调整驱动模块输出电压的背光驱动芯片、 与电源耦合的电感、 与电 感耦合的二极管， 与二极管负极耦合到 LED灯条的输入端， 二极管的正极和电 源接地端之间依次串联有调压可控开关和分压电阻， 调压可控开关的控制端耦 合到背光驱动芯片， 背光驱动芯片包括过流保护引脚、 用于校正驱动模块输出 电压的第一比较器， LED灯条的输出端耦合到第一比较器的反向输入端； 第一 比较器的同向输入端耦合有输出电压可变的保护模块。
保护模块包括第三比较器和用于检测驱动模块输出电流的检测单元。 检测 单元包括将检测到的电流值转换为电压值的转换组件， 转换组件耦合到第三比 较器的同向输入端； 第三比较器的反向输入端耦合有第四基准电压； 第一基准 电压和第五基准电压分别耦合到第三比较器的两个激励端； 第三比较器的输出 端耦合到第一比较器的同向输入端；
本实施例中， 转换组件和分压电阻可以复用， 即分压电阻的端电压耦合到 第三比较器的同向输入端， 同时也耦合到背光驱动芯片的保护引脚。
分压电阻的电流值低于预设的第二电流值时， 分压电阻的端电压小于第四 基准电压， 第三比较器输出第一基准电压； 分压电阻的电流值高于预设的第二 电流值时， 分压电阻的端电压大于第四基准电压， 第三比较器输出第五基准电 压。
基准电压参考取值： 第一基准电压选用 0.6V、 第四基准电压选用 0.45V、 第五基准电压选用 0.7V。 此为一种具体的基准电压数值， 釆用该组数值， 可以 适用于不同种类液晶显示装置的背光驱动。
参见图 7、 本实施例的 LED背光驱动电路的驱动方法， 包括步骤： 检测驱动模块的输出电流， 当输出电流低于预设的第一电流值时， 保护模 块输出第一基准电压到第一比较器的同向输入端； 否则， 保护模块输出大于第 一基准电压的第五基准电压到第一比较器的同向输入端。
本实施例由于釆用了保护模块， 保护模块通过检测驱动模块的输出电流来 判断 LED灯条是否处于重载状态，如果 LED灯条正常工作，则输出一个较低的 第一基准电压给背光驱动芯片的第一比较器； 如果是重载状态 （即超出预设的 第二电流值）， LED灯条的输出端电压也随之增加， 与其耦合的第一比较器的反 向输入端的电压也会增加， 反向输入端跟第一基准电压之间的压差会缩小， 此 时背光驱动芯片会降低占空比降低输出电压， 造成重载时电压过低， LED灯条 达不到预期的亮度； 而保护模块可以在重时及时输出一个高于第一基准电压的 第五基准电压， 这样第一比较器反向输入端和同向输入端的压差随之增加， 背 光驱动芯片会增大占空比提高输出电压， 提高驱动模块重载时的输出电压， 使 LED灯条达到预期的亮度。
实施例五
本实施例公开一种液晶显示装置， 液晶显示装置包括 LED背光驱动电路。 参见图 8, 本实施例公开了一种液晶显示装置， 包括一种 LED背光驱动电路。 参见图 2, LED背光驱动电路包括 LED灯条 20、 LED灯条 20的驱动模块 10, 驱动模块 10包括用于调整驱动模块 10输出电压的背光驱动芯片 11 , 背光驱动 芯片 11包括用于校正驱动模块 10输出电压的第一比较器 Ul , LED灯条 20的 输出端耦合到第一比较器 U1的反向输入端； 第一比较器 U1的同向输入端耦合 有输出电压可变的保护模块 30;
保护模块 30包括用于检测驱动模块 10输出电流的检测单元 31 ; 检测单元 31检测到驱动模块 10的输出电流增大时， 保护模块 30输出到第一比较器 U1 同向端的电压增大； 检测单元 31检测到驱动模块 10的输出电流减小时， 保护 模块 30输出到第一比较器 U1同向端的电压减小。
参见图 9, 本实施例还公开了一种上述 LED背光驱动电路的驱动方法， 包 括步骤：
检测驱动模块的输出电流， 当输出电流增大时， 保护模块输出到第一比较 器 U1的同向输入端的电压增大； 当输出电流减小时， 保护模块 30输出到第一 比较器 U1的同向输入端的电压减小。
本实施例由于釆用了保护模块 30, 保护模块 30通过检测驱动模块 10的输 出电流来判断 LED灯条 20是否处于轻载或重载状态， 当驱动模块 10的输出电 流减小时， 即 LED灯条 20亮度降低， 趋于轻载状态， 此时 LED灯条 20的输出 端电压也随之降低， 与其耦合的第一比较器 U1的反向输入端的电压也会降低， 反向输入端跟第一基准电压之间的压差会增加， 此时背光驱动芯片 11会提高占 空比提高输出电压， 造成轻载时电压过高， 降低了驱动模块 10的效率。 此时保 护模块 30可以在驱动模块 10的输出电流减小时，输出到第一比较器 U1同向端 的电压也随之减小，这样第一比较器 U1反向输入端和同向输入端的压差随之降 低， 背光驱动芯片 11会减小占空比， 降低驱动模块 10的输出电压提高了驱动 模块 10的效率。
当驱动模块 10的输出电流增大时， 即 LED灯条 20亮度升高， 趋于重载状 态， LED灯条 20的输出端电压也随之增加， 与其耦合的第一比较器 U1的反向 输入端的电压也会增加， 反向输入端跟第一基准电压之间的压差会缩小， 此时 背光驱动芯片 11会降低占空比降低输出电压， 造成重载时电压过低， LED灯条 20达不到预期的亮度。此时保护模块 30可以在驱动模块 10的输出电流增大时， 输出到第一比较器 U1同向端的电压也随之增大， 这样第一比较器 U1反向输入 端和同向输入端的压差随之增大， 背光驱动芯片 11会提高占空比， 增加驱动模 块 10的输出电压， 使 LED灯条 20达到预期的亮度。
本实施例的保护模块可以选用输出电压连续可调的调压器， 将调压器的输 出电压和检测的电流值建立函数关系， 这样保护模块的输出电压就可以跟随驱 动模块的电流同步增大或同步减小。
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， 还可以做出若干简单推演或替 换， 都应当视为属于本发明的保护范围。

Claims

权利要求
1、 一种 LED背光驱动电路， 包括 LED灯条、 驱动 LED灯条的驱动模块， 所述驱动模块包括用于调整驱动模块输出电压的背光驱动芯片， 所述背光驱动 芯片包括用于校正驱动模块输出电压的第一比较器， 所述 LED灯条的输出端耦 合到所述第一比较器的反向输入端； 所述第一比较器的同向输入端耦合有输出 电压可变的保护模块；
所述保护模块包括用于检测所述驱动模块输出电流的检测单元；
所述检测单元检测的电流值高于预设的第一电流值时， 所述保护模块输出 第一基准电压到所述第一比较器的同向输入端； 所述检测单元检测的电流值低 于预设的第一电流值时， 所述保护模块输出小于第一基准电压的第二基准电压 到所述第一比较器的同向输入端。
2、 如权利要求 1所述的一种 LED背光驱动电路， 其中， 所述保护模块包 括第二比较器， 所述检测单元包括将检测到的电流值转换为电压值的转换组件， 所述转换组件耦合到第二比较器的同向输入端； 所述第二比较器的反向输入端 耦合有第三基准电压； 所述第一基准电压和第二基准电压分别耦合到所述第二 比较器的两个激励端； 所述第二比较器的输出端耦合到所述第一比较器的同向 输入端；
所述检测单元检测的电流值高于预设的第一电流值时， 所述第二比较器输 出第一基准电压； 所述检测单元检测的电流值低于预设的第一电流值时， 所述 第二比较器输出第二基准电压。
3、 如权利要求 2所述的一种 LED背光驱动电路， 其中， 所述 LED灯条的 驱动模块包括与电源耦合的电感、 与电感耦合的二极管， 二极管负极耦合到所 述 LED灯条的输入端， 所述二极管的正极和电源接地端之间依次串联有调压可 控开关和分压电阻， 所述调压可控开关的控制端耦合到所述背光驱动芯片， 所 述分压电阻的端电压耦合到所述第二比较器的同向输入端。
4、 如权利要求 2所述的一种 LED背光驱动电路， 其中， 所述保护模块还 包括第三比较器， 所述检测单元的转换组件耦合到所述第三比较器的同向输入 端， 所述第三比较器的反向输入端耦合有第四基准电压， 所述第二比较器的输 出端耦合到所述第三比较器的激励端； 所述第三比较器的另一激励端耦合有第 五基准电压； 所述第四基准电压大于所述第三基准电压； 所述第五基准电压大 于所述第一基准电压；
所述检测单元检测的电流值高于预设的第二电流值时， 所述第三比较器输 出第五基准电压耦合到所述第一比较器的同向输入端； 所述第二电流值大于所 述第一电流值。
5、 如权利要求 4所述的一种 LED背光驱动电路， 其中， 所述 LED灯条的 驱动模块包括与电源耦合的电感、 与电感耦合的二极管， 二极管负极耦合到所 述 LED灯条的输入端， 所述二极管的正极和电源接地端之间依次串联有调压可 控开关和分压电阻， 所述调压可控开关的控制端耦合到所述背光驱动芯片， 所 述分压电阻的端电压分别耦合到所述第二比较器和第三比较器的同向输入端。
6、 如权利要求 4所述的一种 LED背光驱动电路， 其中， 所述第一基准电 压选用 0.6V、 第二基准电压选用 0.5V、 第三基准电压选用 0.25V、 第四基准电 压选用 0.45V、 第五基准电压选用 0.7V。
7、 如权利要求 3或 5所述的一种 LED背光驱动电路， 其中， 所述背光驱 动芯片包括过流保护引脚， 所述分压电阻的端电压耦合到所述保护引脚。
8、 一种 LED背光驱动电路， 包括 LED灯条、 LED灯条的驱动模块， 所述 驱动模块包括用于调整驱动模块输出电压的背光驱动芯片， 所述背光驱动芯片 包括用于校正驱动模块输出电压的第一比较器， 所述 LED灯条的输出端耦合到 所述第一比较器的反向输入端； 所述第一比较器的同向输入端耦合有输出电压 可变的保护模块；
所述保护模块包括用于检测所述驱动模块输出电流的检测单元；
所述检测单元检测的电流值低于预设的第二电流值时， 所述保护模块输出 第一基准电压到所述第一比较器的同向输入端； 所述检测单元检测的电流值高 于预设的第二电流值时， 所述保护模块输出大于第一基准电压的第五基准电压 到所述第一比较器的同向输入端。
9、 如权利要求 8所述的一种 LED背光驱动电路， 其中， 所述保护模块包 括第三比较器， 所述检测单元包括将检测到的电流值转换为电压值的转换组件， 所述转换组件耦合到第三比较器的同向输入端； 所述第三比较器的反向输入端 耦合有第四基准电压； 所述第一基准电压和第五基准电压耦合分别耦合到所述 第三比较器的两个激励端； 所述第三比较器的输出端耦合到所述第一比较器的 同向输入端；
所述检测单元检测的电流值低于预设的第二电流值时， 所述第三比较器输 出第一基准电压； 所述检测单元检测的电流值高于预设的第二电流值时， 所述 第三比较器输出第五基准电压。
10、 如权利要求 9所述的一种 LED背光驱动电路， 其中， 所述背光驱动芯 片包括过流保护引脚； 所述 LED灯条的驱动模块包括与电源耦合的电感、 与电 感耦合的二极管， 二极管负极耦合到所述 LED灯条的输入端， 所述二极管的正 极和电源接地端之间依次串联有调压可控开关和分压电阻， 所述调压可控开关 的控制端耦合到所述背光驱动芯片， 所述分压电阻的端电压分别耦合到所述第 三比较器的同向输入端和所述背光驱动芯片的保护引脚。
11、 如权利要求 9所述的一种 LED背光驱动电路， 其中， 所述第一基准电 压选用 0.6V、 第四基准电压选用 0.45V、 第五基准电压选用 0.7V。
12、 一种 LED背光驱动电路， 包括 LED灯条、 LED灯条的驱动模块， 所 述驱动模块包括用于调整驱动模块输出电压的背光驱动芯片， 所述背光驱动芯 片包括用于校正驱动模块输出电压的第一比较器， 所述 LED灯条的输出端耦合 到所述第一比较器的反向输入端； 所述第一比较器的同向输入端耦合有输出电 压可变的保护模块；
所述保护模块包括用于检测所述驱动模块输出电流的检测单元； 检测单元 检测到所述驱动模块的输出电流增大时， 所述保护模块输出到第一比较器同向 端的电压同步增大； 检测单元检测到所述驱动模块的输出电流减小时， 所述保 护模块输出到第一比较器同向端的电压同步减小。
13、 如权利要求 12所述的一种 LED背光驱动电路， 其中， 所述保护模块 为输出电压连续可调的调压器， 所述调压器的输出电压和检测到的电流值之间 建立有函数关系。
PCT/CN2012/087545 2012-12-25 2012-12-26 一种led背光驱动电路 Ceased WO2014101005A1 (zh)

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