WO2014187015A1 - Led背光驱动电路、液晶显示装置和一种驱动方法 - Google Patents
Led背光驱动电路、液晶显示装置和一种驱动方法 Download PDFInfo
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- WO2014187015A1 WO2014187015A1 PCT/CN2013/078307 CN2013078307W WO2014187015A1 WO 2014187015 A1 WO2014187015 A1 WO 2014187015A1 CN 2013078307 W CN2013078307 W CN 2013078307W WO 2014187015 A1 WO2014187015 A1 WO 2014187015A1
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—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
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- 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
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- 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
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- 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
Definitions
- the present invention relates to the field of liquid crystal display, and more particularly to an LED backlight driving circuit, a liquid crystal display device, and a driving method.
- the LCD TV includes a liquid crystal panel and a backlight module, and the backlight module mostly uses LED as a backlight source, and a plurality of LED lamp beads are connected in series to form an LED light bar, which is driven and displayed by a backlight driving circuit; backlight brightness required for a large-size LCD TV High, need to use multiple series of LED strips arranged in parallel, the output power of the whole backlight module is very large, the backlight drive circuit with single boost line can not provide matching power, need to use dual boost circuit in parallel to drive the LED Light.
- the external power supply V+ is simultaneously connected to the first boosting circuit 21 and the second boosting circuit 22, and the first boosting circuit 21 and the second boosting circuit 22 collectively drive the LED light bar 30.
- the first boosting circuit 21 is driven by the first constant current driving chip 11; the second boosting circuit 22 is driven by the second constant current driving chip 12.
- the boosting circuit has the highest conversion efficiency during full-load operation, and the conversion efficiency decreases as the output power decreases. Therefore, the first boosting circuit 21 and the second boosting circuit 22 operate simultaneously in a light load condition, and the whole The heat loss of the circuit is large, and the conversion efficiency is smaller than the conversion efficiency of the single-channel boost line when it is fully loaded.
- the technical problem to be solved by the present invention is to provide an LED backlight driving circuit, a liquid crystal display device and a driving method capable of improving the conversion efficiency of a multi-channel boosting circuit.
- An LED backlight driving circuit includes a power module, an LED light bar, and a constant current driving chip for adjusting brightness of the LED light bar, wherein the constant current driving chip is coupled with a PWM dimming signal; the power module and the LED light bar There are N boost modules arranged in parallel, wherein the control terminals of 1 ⁇ (N-1) boost modules are coupled with a comparison module; that is, at least one, up to (N-1) boost modules are controlled. End coupling There is a comparison module;
- the comparison module drives the corresponding boost module to be turned off;
- the N is an integer greater than or equal to 2.
- the comparison module includes a comparator, a non-inverting input end of the comparator is coupled with a reference voltage, and a reverse input end is coupled with a conversion unit that converts the PWM dimming signal into an equivalent voltage; a switching controllable switch is connected in series between the control terminal and the ground end of the LED backlight driving circuit; the magnitude of the reference voltage is less than or equal to an equivalent voltage of the PWM dimming signal corresponding to the preset threshold value, when When the equivalent voltage output by the conversion unit is less than the reference voltage, the comparator drives the switching controllable switch to be turned off.
- This is a circuit structure of a specific comparison module.
- the PWM dimming signal of the rectangular wave is converted into a smooth DC voltage signal by the conversion unit, and different duty ratios correspond to DC voltage signals of different values. Therefore, the equivalent voltage of the PWM dimming signal corresponding to the preset threshold can be used as a comparison reference, and the voltage signal outputted by the conversion unit can be compared to determine whether the duty ratio of the PWM dimming signal exceeds the threshold.
- the technical solution converts the duty ratio comparison 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.
- the conversion unit includes a filter resistor and a filter capacitor; the PWM dimming signal is connected to an inverting input end of the comparator through a filter resistor, and the filter capacitor is serially connected to the opposite input end of the comparator and Between the ground terminals of the LED backlight drive circuit.
- the technical solution uses an RC filter to convert a high frequency varying PWM dimming signal into a flat voltage signal, which is low in cost.
- control terminal of the N-1 boosting modules is coupled with a comparison module, and when the duty ratio of the PWM dimming signal is less than or equal to (100/N)%, the comparison module drives the corresponding rising The pressure module is turned off.
- the duty ratio of the PWM dimming signal is less than or equal to (100/N)%, only one boosting module is reserved, and all others are turned off; since only one boosting module is in operation, the power loss is minimum. And because it fully bears all the load, the output power is also kept high, which further improves the conversion efficiency and reduces the energy consumption.
- the boosting module includes an inductor, a diode, a voltage controllable switch, and a capacitor; One end of the inductor is coupled to the power module, and the other end is coupled to the anode of the diode and coupled to the ground of the LED backlight driving circuit through a voltage-regulated controllable switch; the negative pole of the diode is coupled to the anode of the LED strip; and is coupled to the capacitor through a capacitor The ground end; the control end of the voltage controllable switch is coupled to the constant current driving chip.
- This is the circuit structure of a specific boost module.
- the constant current driving chip includes a control unit that controls an output voltage of the boosting module, and a detecting unit that adjusts brightness of the LED light bar, and the LED light bar is driven by the detecting unit and the LED backlight
- the ground terminal of the circuit is coupled; the PWM dimming signal is coupled to the control terminal of the detecting unit.
- the detecting unit 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 voltage dividing resistor
- the PWM dimming signal is coupled to the control end of the dimming controllable switch; each of the boosting modules corresponds to a constant current driving chip, and correspondingly, the LED strips are divided into N groups, each constant current
- the driver chip controls a set of LED strips. This is the circuit structure of a specific detection unit.
- Constant current driving chip and boosting module - corresponding, different boosting modules and their control circuits are independent of each other, and the single boosting module and its constant current driving chip loss do not affect the normality of other boosting modules and constant current driving chips. Operation; Furthermore, due to the large number of LED strips driven by multiple boost modules, it is difficult for a typical constant current driver chip to provide the same number of pins to be connected to the LED strips. Therefore, multiple constant current driving chips are used. Packet control eliminates the need to redesign existing constant current driver chips, which reduces development costs and reduces development time.
- boost modules wherein a control module of one boost module is coupled with a comparison module.
- the comparison module includes a comparator, a non-inverting input end of the comparator is coupled with a reference voltage, and a reverse input end is coupled with a conversion unit that converts the PWM dimming signal into an equivalent voltage; a control end of the boosting module And a switching controllable switch is connected in series with the ground end of the LED backlight driving circuit; the converting unit includes a filter resistor and a filter capacitor; and the PWM dimming signal is connected to the opposite input end of the comparator through a filter resistor.
- the filter capacitor is serially connected to the opposite input of the comparator and the LED backlight is driven Between the ground terminals of the circuit;
- the magnitude of the reference voltage is less than or equal to an equivalent voltage of a PWM dimming signal corresponding to a 50% duty ratio, and the comparator drives the switching when an equivalent voltage output by the conversion unit is less than the reference voltage
- the controllable switch is turned off.
- the boosting module includes an inductor, a diode, a voltage-regulating controllable switch, and a capacitor; one end of the inductor is coupled to the power module, and the other end is coupled to the anode of the diode, and coupled to the ground of the LED backlight driving circuit through the voltage-regulating controllable switch; a cathode of the diode is coupled to a positive pole of the LED strip; and is capacitively coupled to the ground;
- the constant current driving chip includes a control unit, and a detecting unit for adjusting brightness of the LED light bar, and a control end of the voltage regulating switch is coupled to the control unit;
- the detecting unit includes a dimming controllable switch, An input end of the dimmable 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 drive circuit through a voltage dividing resistor; the PWM dimming signal coupled to the dimming controllable The control end of the switch;
- Each of the boosting modules corresponds to a constant current driving chip.
- the LED light strips are divided into two groups, and each constant current driving chip controls a group of LED light strips.
- a liquid crystal display device comprising the LED backlight driving circuit of the present invention.
- a driving method of an LED backlight driving circuit the LED backlight driving circuit comprises a power module, an LED light bar, and a constant current driving chip for adjusting brightness of the LED light bar, wherein the constant current driving chip is coupled with a PWM dimming signal
- the power module and the LED strip are connected in series with N boost modules arranged in parallel; the driving method includes:
- step B detecting the duty cycle of the PWM dimming signal, when the duty ratio is less than the preset threshold, go to step C; otherwise, go to step D;
- step C controlling at least one boost module to be turned off; returning to step A;
- the N is an integer greater than or equal to 2.
- the maximum output power W of each boost module is saved.
- the threshold in the step B has N-1, and each threshold is W.
- step C determining the total required power W of the current LED strip, if W is less than or equal to (Nx) W 0 , then turning off the x boost modules; returning to step A;
- X is a positive integer less than N.
- the technical solution adopts a step-by-step shutdown method to control the boost module. Specifically, if the maximum output power of the N-1 booster modules can meet the brightness requirement of the current LED strip, a boost module is turned off; if the maximum output power of the N-2 booster modules can satisfy the current LED strip The brightness requirement, turn off the two boost modules; and so on. This allows the LED strip to be driven with a minimum of boost modules with maximum power, maximizing conversion efficiency and reducing energy consumption.
- the invention adopts a comparison module to monitor the PWM dimming signal, and the PWM dimming signal is used to adjust the average value of the LED strip current, and the brightness of the LED backlight is adjusted by the customer according to different ambient brightness.
- the PWM dimming signal is a rectangular wave, coupled to the inside of the constant current driving chip, so that the current flowing through the LED strip becomes a rectangular wave having the same duty ratio, and the average value of the LED current changes with the change of the duty ratio, corresponding to The brightness of the LED backlight also changes. It can be seen that the output power of the LED backlight driving circuit is proportional to the duty ratio of the PWM dimming signal.
- FIG. 1 is a schematic diagram of a conventional LED backlight driving circuit
- FIG. 2 is a schematic diagram showing the principle of an LED backlight driving circuit according to an embodiment of the present invention
- FIG. 3 is a schematic diagram of a driving method of an LED backlight driving circuit according to Embodiment 2 of the present invention. ⁇ detailed description ⁇
- 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 an LED backlight driving circuit.
- the LED backlight driving circuit comprises a power module, an LED light bar, and a constant current driving chip for adjusting the brightness of the LED light bar, the constant current driving chip is coupled with a PWM dimming signal; and the power module and the LED light bar are connected in series with N
- the boosting module is arranged in parallel, wherein the control terminals of 1 ⁇ (N-1) boost modules are coupled with a comparison module; that is, at least one, and the control terminals of at most (N-1) boost modules are coupled with a comparison module.
- the comparison module drives the corresponding boost module to turn off;
- N is an integer greater than or equal to 2.
- the invention adopts a comparison module to monitor the PWM dimming signal, and the PWM dimming signal is used to adjust the average value of the LED strip current, and the brightness of the LED backlight is adjusted by the customer according to different ambient brightness.
- the PWM dimming signal is a rectangular wave, coupled to the inside of the constant current driving chip, so that the current flowing through the LED strip becomes a rectangular wave having the same duty ratio, and the average value of the LED current changes with the change of the duty ratio, corresponding to The brightness of the LED backlight also changes. It can be seen that the output power of the LED backlight driving circuit is proportional to the duty ratio of the PWM dimming signal.
- the LED backlight driving circuit includes a power module 50, an LED strip 30, and a constant current driving chip 10 for adjusting the brightness of the LED strip 30.
- the constant current driving chip 10 is coupled with a PWM dimming signal;
- the comparison terminal 40 is coupled to the control terminals of 1 ⁇ (Nl) boost modules.
- the LED backlight driving circuit of the present embodiment includes a first boosting module 21 and a second boosting module 22, wherein the control terminal of the second boosting module 22 is coupled with the comparing module 40.
- the comparison module 40 includes a comparator OP1.
- the non-inverting input terminal of the comparator OP1 is coupled with a reference voltage VF, and the inverting input terminal is coupled with a conversion unit 41 for converting the PWM dimming signal into an equivalent voltage;
- a switchable controllable switch Q5 is connected in series between the grounding ends of the LED backlight driving circuit;
- the converting unit 41 includes a filter resistor R0 and a filter capacitor CO; the PWM dimming signal is connected to the inverting input terminal of the comparator OP1 through the filter resistor R0, and is filtered.
- the capacitor CO is connected in series between the inverting input of the comparator OP1 and the ground of the LED backlight driving circuit.
- the magnitude of the reference voltage VF is less than or equal to the equivalent voltage of the PWM dimming signal corresponding to the 50% duty ratio.
- the comparator OP1 drives the switchable controllable switch Q5 to be turned off. .
- boost module If there are more than two boost modules, it can also be done by stepping off. Specifically, if the maximum output power of the N-1 boost modules can meet the brightness requirement of the current LED strip 30, a boost module is turned off; if the maximum output power of the N-2 boost modules can satisfy the current LED The brightness requirement of strip 30 turns off both boost modules; and so on. In this way, the LED strip 30 can be driven with a minimum boost module with power as much as possible, maximizing conversion efficiency and reducing energy consumption.
- Each boosting module includes an inductor L1/L2, a diode D1/D2, a voltage-regulating controllable switch Q1/Q2, and a capacitor C1/C2; one end of the inductor L1/L2 is coupled to the power module 50, and the other end is coupled to the anode of the diode D1/D2. And the voltage controllable switch Q1/Q2 is coupled to the ground terminal of the LED backlight driving circuit; the cathode of the diode D1/D2 is coupled to the anode of the LED strip 30; and is coupled to the ground through the capacitor C1/C2;
- the constant current driving chip 10 includes a control unit 13 and a detecting unit that adjusts the brightness of the LED strip 30 14.
- the control terminal of the voltage controllable switch Q1/Q2 is coupled to the control unit 13;
- the detection unit includes a dimmable controllable switch Q3/Q4, and the input of the dimmable controllable switch Q3/Q4 is coupled to the LED strip 30
- the output terminal is coupled to the ground terminal of the LED backlight driving circuit through a voltage dividing resistor R1/R2; the PWM dimming signal is coupled to the control terminal of the dimmable controllable switch Q3/Q4.
- Each boosting module corresponds to one constant current driving chip 10, that is, there are two constant current driving chips 10, the first constant current driving chip 11 controls the first boosting module 21; the second constant current driving chip 12 controls the second boosting Module 22; Correspondingly, the LED strips 30 are divided into two groups, and each constant current driving chip 10 controls a group of LED strips 30.
- Constant current driving chip 10 and boosting module - correspondingly, different boosting modules and their control circuits are independent of each other, and the loss of a single boosting module and its constant current driving chip 10 does not affect other boosting modules and constant current driving chips. Normal operation of 10; Furthermore, since the number of strings of LED strips 30 driven by a plurality of boost modules is large, it is difficult for the general constant current driving chip 10 to provide the same number of pins to be connected with the LED strips 30, so The grouping control of the plurality of constant current driving chips 10 does not require redesigning the existing constant current driving chip 10, which is advantageous in reducing development cost and reducing development time.
- the PWM dimming signal of the rectangular wave is converted into a smooth DC voltage signal by the converting unit 41, and different duty ratios correspond to DC voltage signals of different values. Therefore, the equivalent voltage of the PWM dimming signal corresponding to the preset threshold can be used as a comparison reference, and the voltage signal outputted by the conversion unit 41 can be compared to determine whether the duty ratio of the PWM dimming signal exceeds the threshold. Comparing the duty ratio comparison of the load into the voltage of the single unit reduces the technical difficulty, which is beneficial to improving the development progress and reducing the development cost.
- the RC filter is used to convert the high frequency variable PWM dimming signal into a flat voltage signal, which is low in cost.
- the invention also discloses a driving method of an LED backlight driving circuit.
- the LED backlight driving circuit comprises a power module, an LED light bar, and a constant current driving chip for adjusting brightness of the LED light bar, and the constant current driving chip is coupled with PWM dimming. Signal; N power supply modules and LED strips are connected in series with N boost modules arranged in parallel.
- the driving method of the LED backlight driving circuit includes: A. preset a threshold value of a duty ratio of a PWM dimming signal;
- step B detecting the duty cycle of the PWM dimming signal, when the duty cycle is less than the preset threshold, go to step C; otherwise, go to step D;
- step C controlling at least one boost module to be turned off; returning to step A;
- step D Maintain the normal operation of the boost module; return to step A;
- the N is an integer greater than or equal to 2.
- step A the maximum output power W of each boost module is saved.
- the threshold in step B has N-1, and each threshold is W.
- the integer duty power corresponds to the duty cycle of the PWM dimming signal;
- step C the total required power W of the current LED strip is determined. If W is less than or equal to (NX) W 0 , the X boost modules are turned off;
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Abstract
一种LED背光驱动电路包括电源模块、LED灯条,以及用于调整LED灯条亮度的恒流驱动芯片,所述恒流驱动芯片耦合有PWM调光信号;所述电源模块和LED灯条之间串接有N个并联设置的升压模块,其中1~(N-1)个升压模块的控制端耦合有比较模块;当PWM调光信号的占空比小于预设的阈值时,所述比较模块驱动相应的升压模块关断;所述N为大于或等于2的整数。
Description
LED背光驱动电路、 液晶显示装置和一种驱动方法
【技术领域】
本发明涉及液晶显示领域, 更具体的说, 涉及一种 LED背光驱动电路、 液 晶显示装置和一种驱动方法。
【背景技术】
液晶电视包括液晶面板和背光模组, 背光模组多采用 LED作为背光源, 将 多个 LED灯珠串接成 LED灯条, 由背光驱动电路进行驱动显示; 大尺寸液晶电 视所需要的背光亮度高, 需要采用多串并联设置的 LED灯条, 整个背光模组的 输出功率很大, 采用单路升压线路的背光驱动电路无法提供匹配的功率, 需要 使用双路升压电路并联来驱动 LED灯条。 如图 1所示, 外部电源 V+同时连接 到第一升压电路 21和第二升压电路 22, 由第一升压电路 21和第二升压电路 22 共同驱动 LED灯条 30。 第一升压电路 21通过第一恒流驱动芯片 11驱动; 第二 升压电路 22通过第二恒流驱动芯片 12驱动。
升压电路在全载工作时的转换效率最高, 随着输出功率的降低, 其转换效 率随之下降, 因此在第一升压电路 21和第二升压电路 22同时工作在轻载情况, 整个电路的热损耗大, 转换效率要小于单路升压线路全载工作时的转换效率。
【发明内容】
本发明所要解决的技术问题是提供一种能提高多路升压电路转换效率的 LED背光驱动电路、 液晶显示装置和一种驱动方法。
本发明的目的是通过以下技术方案来实现的:
一种 LED背光驱动电路, 包括电源模块、 LED灯条, 以及用于调整 LED 灯条亮度的恒流驱动芯片,所述恒流驱动芯片耦合有 PWM调光信号; 所述电源 模块和 LED灯条之间串接有 N个并联设置的升压模块,其中 1 ~ (N-1)个升压模 块的控制端耦合有比较模块; 即至少一个, 最多 (N-1)个升压模块的控制端耦合
有比较模块;
当 PWM调光信号的占空比小于预设的阈值时,所述比较模块驱动相应的升 压模块关断;
所述 N为大于或等于 2的整数。
进一步的, 所述比较模块包括比较器, 所述比较器的同向输入端耦合有基 准电压,反向输入端耦合有将 PWM调光信号转化成等效电压的转换单元; 所述 升压模块的控制端和所述 LED 背光驱动电路的接地端之间串接有切换可控开 关;所述基准电压的大小小于或等于所述预设的阈值对应的 PWM调光信号的等 效电压, 当所述转换单元输出的等效电压小于所述基准电压时, 所述比较器驱 动所述切换可控开关关断。 此为一种具体的比较模块的电路结构, 通过转换单 元将矩形波的 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 电压作为比较基准,跟转换单元输出的电压信号进行比对,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,所述转换单元包括滤波电阻和滤波电容; 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, 成本低廉。
进一步的,所述 N-1个升压模块的控制端耦合有比较模块, 当所述 PWM调 光信号的占空比小于或等于 (100/N ) %时, 所述比较模块驱动相应的升压模块 关断。 本技术方案在 PWM调光信号的占空比小于或等于 ( 100/N ) %时, 只保 留一个升压模块工作, 其他的全部关断; 由于只有一个升压模块处于运行状态, 功率损耗最小, 并且由于其完全承担所有负荷, 因此输出功率也保持较高的状 态, 进一步提升了转换效率, 降低能耗。
进一步的, 所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述
电感的一端耦合电源模块, 另一端耦合二极管正极, 并通过调压可控开关耦合 到 LED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; 所述调压可控开关的控制端耦合到所述恒流驱 动芯片。 此为一种具体的升压模块的电路结构。
进一步的, 所述恒流驱动芯片包括控制所述升压模块输出电压的控制单元, 以及调节 LED灯条亮度的侦测单元, 所述 LED灯条通过所述侦测单元与所述 LED背光驱动电路的接地端耦合; 所述 PWM调光信号耦合到所述侦测单元的 控制端。 此为一种具体的恒流驱动芯片的电路结构。
进一步的, 所述侦测单元包括调光可控开关, 调光可控开关的输入端耦合 到所述 LED灯条的负极;其输出端通过一分压电阻耦合到 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; 所述每个升压 模块对应一个恒流驱动芯片, 相应的, 所述 LED灯条分成 N组, 每个恒流驱动 芯片控制一组 LED灯条。 此为一种具体的侦测单元的电路结构。 恒流驱动芯片 和升压模块——对应, 不同升压模块及其控制电路之间相互独立, 单个升压模 块及其恒流驱动芯片损耗都不影响其他升压模块和恒流驱动芯片的正常运行; 再者, 由于多个升压模块驱动的 LED灯条的串数较多, 一般的恒流驱动芯片很 难提供相同数量的引脚与 LED灯条连接, 因此采用多个恒流驱动芯片分组控制 无须对现有的恒流驱动芯片进行重新设计, 有利于减少开发成本, 缩减开发时 间。
进一步的, 所述升压模块有两个, 其中一个升压模块的控制端耦合有比较 模块,
所述比较模块包括比较器, 所述比较器的同向输入端耦合有基准电压, 反 向输入端耦合有将 PWM调光信号转化成等效电压的转换单元;所述升压模块的 控制端和所述 LED背光驱动电路的接地端之间串接有切换可控开关; 所述转换 单元包括滤波电阻和滤波电容;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;
所述基准电压的大小小于或等于 50%占空比对应的 PWM调光信号的等效 电压, 当所述转换单元输出的等效电压小于所述基准电压时, 所述比较器驱动 所述切换可控开关关断。
所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端 耦合电源模块, 另一端耦合二极管正极, 并通过调压可控开关耦合到 LED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;
所述恒流驱动芯片包括控制单元, 以及调节 LED灯条亮度的侦测单元, 所 述调压可控开关的控制端耦合到所述控制单元; 所述侦测单元包括调光可控开 关, 调光可控开关的输入端耦合到所述 LED灯条的负极; 其输出端通过一分压 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;
所述每个升压模块对应一个恒流驱动芯片, 相应的, 所述 LED灯条分成两 组, 每个恒流驱动芯片控制一组 LED灯条。
此为一种双升压模块的 LED背光驱动电路。
一种液晶显示装置, 包括本发明所述的 LED背光驱动电路。
一种 LED背光驱动电路的驱动方法,所述 LED背光驱动电路包括电源模块、 LED灯条, 以及用于调整 LED灯条亮度的恒流驱动芯片, 所述恒流驱动芯片耦 合有 PWM调光信号; 所述电源模块和 LED灯条之间串接有 N个并联设置的升 压模块; 所述驱动方法包括:
A、 预设一个 PWM调光信号的占空比的阈值;
B、检测 PWM调光信号的占空比, 当占空比小于预设的阈值时, 转步骤 C; 否则, 转步骤 D;
C、 控制至少一个升压模块关断; 返回步骤 A;
D、 维持升压模块正常运行; 返回步骤 A;
所述 N为大于或等于 2的整数。
进一步的, 所述步骤 A中, 保存每个升压模块的最大输出功率 W。, 所述步骤 B中的阈值有 N-1个, 且每个阈值都是 W。的整数倍功率对应的 PWM调光信号的占空比;
所述步骤 C中, 判断当前 LED灯条的总需求功率 W, 如果 W小于或等于 ( N-x ) W0, 则关断 x个升压模块; 返回步骤 A;
X为小于 N的正整数。
本技术方案采用逐步关断的方式来控制升压模块。 具体来说, 如果 N-1 个 升压模块最大输出功率可以满足当前 LED灯条的亮度需求, 就关断一个升压模 块; 如果 N-2个升压模块最大输出功率可以满足当前 LED灯条的亮度需求, 就 关断两个升压模块; 如此类推。 这样就可以在功率允许的前提下应该用最少的 升压模块来驱动 LED灯条, 最大限度的提高转换效率, 降低能耗。
本发明由于采用了比较模块来监测 PWM调光信号, PWM调光信号用来调 节 LED灯条电流平均值大小,由客户根据不同的环境亮度来调节合适的 LED背 光亮度。 PWM调光信号为矩形波, 耦合到恒流驱动芯片内部, 使流经 LED灯 条的电流成为具有相同占空比的矩形波, LED 电流平均值随着占空比的大小变 化而改变, 对应的 LED背光亮度也改变。 可见, LED背光驱动电路的输出功率 与 PWM调光信号的占空比大小成正比, 因此, 只要预设一个 PWM调光信号的 占空比的阈值, 当占空比小于预设的阈值时, 控制至少一个升压模块关断, 这 样剩余的升压模块就需要承担更大的功率输出, 随着输出功率的增加, 处于运 行状态的升压模块的转换效率随之增加, 降低了能量损耗。
【附图说明】
图 1是现有的一种 LED背光驱动电路的原理示意图;
图 2是本发明实施例一 LED背光驱动电路的原理示意图;
图 3是本发明实施例二 LED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 LED背光驱动电路。 LED背光驱动电路包括电源模块、 LED灯条, 以及用于调整 LED灯条亮度的恒流驱动芯片, 恒流驱动芯片耦合有 PWM调光 信号;电源模块和 LED灯条之间串接有 N个并联设置的升压模块,其中 1 ~ (N-1) 个升压模块的控制端耦合有比较模块; 即至少一个, 最多 (N-1)个升压模块的 控制端耦合有比较模块。
当 PWM调光信号的占空比小于预设的阈值时, 比较模块驱动相应的升压模 块关断;
N为大于或等于 2的整数。
本发明由于采用了比较模块来监测 PWM调光信号, PWM调光信号用来调 节 LED灯条电流平均值大小,由客户根据不同的环境亮度来调节合适的 LED背 光亮度。 PWM调光信号为矩形波, 耦合到恒流驱动芯片内部, 使流经 LED灯 条的电流成为具有相同占空比的矩形波, LED 电流平均值随着占空比的大小变 化而改变, 对应的 LED背光亮度也改变。 可见, LED背光驱动电路的输出功率 与 PWM调光信号的占空比大小成正比, 因此, 只要预设一个 PWM调光信号的 占空比的阈值, 当占空比小于预设的阈值时, 控制至少一个升压模块关断, 这 样剩余的升压模块就需要承担更大的功率输出, 随着输出功率的增加, 处于运 行状态的升压模块的转换效率随之增加, 降低了能量损耗。
下面以双升压模块的 LED 背光驱动电路为例, 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, LED背光驱动电路包括电源模块 50、 LED灯条 30, 以及用于 调整 LED灯条 30亮度的恒流驱动芯片 10, 恒流驱动芯片 10耦合有 PWM调光 信号; 电源模块 50和 LED灯条 30之间串接有 N个并联设置的升压模块, 其中
1 ~ (N-l)个升压模块的控制端耦合有比较模块 40。 本实施方式的 LED背光驱动 电路包括第一升压模块 21和第二升压模块 22, 其中第二升压模块 22的控制端 耦合有比较模块 40。
比较模块 40包括比较器 OP1 ,比较器 OP1的同向输入端耦合有基准电压 VF, 反向输入端耦合有将 PWM调光信号转化成等效电压的转换单元 41; 升压模块 的控制端和 LED背光驱动电路的接地端之间串接有切换可控开关 Q5;转换单元 41包括滤波电阻 R0和滤波电容 CO; PWM调光信号通过滤波电阻 R0连接到比 较器 OP1的反向输入端, 滤波电容 CO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。
基准电压 VF的大小小于或等于 50%占空比对应的 PWM调光信号的等效电 压, 当转换单元 41输出的等效电压小于基准电压 VF时, 比较器 OP1驱动切换 可控开关 Q5关断。
如果升压模块超过两个时, 也可以通过逐步关断是方式进行。 具体来说, 如 果 N-1个升压模块最大输出功率可以满足当前 LED灯条 30的亮度需求, 就关 断一个升压模块;如果 N-2个升压模块最大输出功率可以满足当前 LED灯条 30 的亮度需求, 就关断两个升压模块; 如此类推。 这样就可以在功率允许的前提 下用最少的升压模块来驱动 LED灯条 30,最大限度的提高转换效率,降低能耗。 当然, 也可以在 PWM调光信号的占空比小于或等于 ( 100/N ) %时, 只保留一 个升压模块工作, 其他的全部关断; 由于只有一个升压模块处于运行状态, 功 率损耗最小, 并且由于其完全承担所有负荷, 因此输出功率也保持较高的状态, 进一步提升了转换效率, 降低能耗。
每个升压模块包括电感 Ll/L2、 二极管 Dl/D2、 调压可控开关 Q1/Q2和电容 C1/C2; 电感 L1/L2的一端耦合电源模块 50, 另一端耦合二极管 D1/D2正极, 并通过调压可控开关 Q1/Q2耦合到 LED背光驱动电路的接地端;二极管 D1/D2 的负极耦合到 LED灯条 30的正极; 并通过电容 C1/C2耦合到接地端;。
恒流驱动芯片 10包括控制单元 13, 以及调节 LED灯条 30亮度的侦测单元
14, 调压可控开关 Q1/Q2的控制端耦合到控制单元 13; 侦测单元包括调光可控 开关 Q3/Q4, 调光可控开关 Q3/Q4的输入端耦合到 LED灯条 30的负极; 其输 出端通过一分压电阻 R1/R2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/Q4的控制端。
每个升压模块对应一个恒流驱动芯片 10, 即恒流驱动芯片 10也有两个, 第 一恒流驱动芯片 11控制第一升压模块 21; 第二恒流驱动芯片 12控制第二升压 模块 22; 相应的, LED灯条 30分成两组, 每个恒流驱动芯片 10控制一组 LED 灯条 30。
恒流驱动芯片 10和升压模块——对应, 不同升压模块及其控制电路之间相 互独立, 单个升压模块及其恒流驱动芯片 10损耗都不影响其他升压模块和恒流 驱动芯片 10的正常运行; 再者, 由于多个升压模块驱动的 LED灯条 30的串数 较多, 一般的恒流驱动芯片 10很难提供相同数量的引脚与 LED灯条 30连接, 因此采用多个恒流驱动芯片 10分组控制无须对现有的恒流驱动芯片 10进行重 新设计, 有利于减少开发成本, 缩减开发时间。
本实施方式通过转换单元 41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基准, 跟转换单元 41输出的电压 信号进行比对,就可以判断 PWM调光信号的占空比是否超出阈值。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。而采用 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, 成本低廉。
实施例二
本发明还公开了一种 LED背光驱动电路的驱动方法, LED背光驱动电路包 括电源模块、 LED灯条, 以及用于调整 LED灯条亮度的恒流驱动芯片, 恒流驱 动芯片耦合有 PWM调光信号; 电源模块和 LED灯条之间串接有 N个并联设置 的升压模块。 如图 3所示, LED背光驱动电路的驱动方法包括:
A、 预设一个 PWM调光信号的占空比的阈值;
B、 检测 PWM调光信号的占空比, 当占空比小于预设的阈值时, 转步骤 C; 否则, 转步骤 D;
C、 控制至少一个升压模块关断; 返回步骤 A;
D、 维持升压模块正常运行; 返回步骤 A;
所述 N为大于或等于 2的整数。
为了最大限度的提高转换效率, 降低能耗, 在功率允许的前提下应该用最少 的升压模块来驱动 LED灯条。 为此, 步骤 A中, 保存每个升压模块的最大输出 功率 W。, 步骤 B中的阈值有 N-1个, 且每个阈值都是 W。的整数倍功率对应的 PWM调光信号的占空比 ;
步骤 C中, 判断当前 LED灯条的总需求功率 W, 如果 W小于或等于(N-X ) W0, 则关断 X个升压模块; 返回步骤 。
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
1. 一种 LED背光驱动电路, 包括电源模块、 LED灯条, 以及用于调整 LED 灯条亮度的恒流驱动芯片,所述恒流驱动芯片耦合有 PWM调光信号; 所述电源 模块和 LED灯条之间串接有 N个并联设置的升压模块,其中 1 ~ (N-1)个升压模 块的控制端耦合有比较模块;
当 PWM调光信号的占空比小于预设的阈值时,所述比较模块驱动相应的升 压模块关断;
所述 N为大于或等于 2的整数。
2. 如权利要求 1所述的 LED背光驱动电路,其中,所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端耦合电源模块, 另一端耦合二 极管正极, 并通过调压可控开关耦合到 LED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 压可控开关的控制端耦合到所述恒流驱动芯片。
3. 如权利要求 1所述的 LED背光驱动电路, 其中, 所述比较模块包括比较 器,所述比较器的同向输入端耦合有基准电压,反向输入端耦合有将 PWM调光 信号转化成等效电压的转换单元; 所述升压模块的控制端和所述 LED背光驱动 电路的接地端之间串接有切换可控开关;
所述基准电压的大小小于或等于所述预设的阈值对应的 PWM调光信号的 等效电压, 当所述转换单元输出的等效电压小于所述基准电压时, 所述比较器 驱动所述切换可控开关关断。
4. 如权利要求 3所述的 LED背光驱动电路, 其中, 所述转换单元包括滤波 电阻和滤波电容; 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。
5. 如权利要求 4所述的 LED背光驱动电路,其中,所述升压模块包括电感、
二极管、 调压可控开关和电容; 所述电感的一端耦合电源模块, 另一端耦合二 极管正极, 并通过调压可控开关耦合到 LED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 压可控开关的控制端耦合到所述恒流驱动芯片。
6. 如权利要求 1所述的 LED背光驱动电路, 其中, 所述 N-1个升压模块的 控制端耦合有比较模块, 当所述 PWM调光信号的占空比小于或等于( 100/N ) % 时, 所述比较模块驱动相应的升压模块关断。
7. 如权利要求 6所述的 LED背光驱动电路,其中,所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端耦合电源模块, 另一端耦合二 极管正极, 并通过调压可控开关耦合到 LED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 压可控开关的控制端耦合到所述恒流驱动芯片。
8. 如权利要求 1所述的 LED背光驱动电路, 其中, 所述恒流驱动芯片包括 控制所述升压模块输出电压的控制单元, 以及调节 LED灯条亮度的侦测单元, 所述侦测单元包括调光可控开关, 调光可控开关的输入端耦合到所述 LED灯条 的负极; 其输出端通过一分压电阻耦合到 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; 所述每个升压模块对应一个 恒流驱动芯片, 相应的, 所述 LED灯条分成 N组, 每个恒流驱动芯片控制一组 LED灯条。
9. 如权利要求 1所述的 LED背光驱动电路, 其中, 所述升压模块有两个, 其中一个升压模块的控制端耦合有比较模块,
所述比较模块包括比较器, 所述比较器的同向输入端耦合有基准电压, 反 向输入端耦合有将 PWM调光信号转化成等效电压的转换单元;所述升压模块的 控制端和所述 LED背光驱动电路的接地端之间串接有切换可控开关; 所述转换 单元包括滤波电阻和滤波电容;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;
所述基准电压的大小小于或等于 50%占空比对应的 PWM调光信号的等效 电压, 当所述转换单元输出的等效电压小于所述基准电压时, 所述比较器驱动 所述切换可控开关关断。
所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端 耦合电源模块, 另一端耦合二极管正极, 并通过调压可控开关耦合到 LED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;
所述恒流驱动芯片包括控制单元, 以及调节 LED灯条亮度的侦测单元, 所 述调压可控开关的控制端耦合到所述控制单元; 所述侦测单元包括调光可控开 关, 调光可控开关的输入端耦合到所述 LED灯条的负极; 其输出端通过一分压 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;
所述每个升压模块对应一个恒流驱动芯片, 相应的, 所述 LED灯条分成两 组, 每个恒流驱动芯片控制一组 LED灯条。
10. 一种液晶显示装置, 包括 LED背光驱动电路; 所述 LED背光驱动电路 包括电源模块、 LED灯条, 以及用于调整 LED灯条亮度的恒流驱动芯片, 所述 恒流驱动芯片耦合有 PWM调光信号; 所述电源模块和 LED灯条之间串接有 N 个并联设置的升压模块, 其中 1 ~ (N-1)个升压模块的控制端耦合有比较模块; 当 PWM调光信号的占空比小于预设的阈值时,所述比较模块驱动相应的升 压模块关断;
所述 N为大于或等于 2的整数。
11. 如权利要求 10所述的液晶显示装置, 其中, 所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端耦合电源模块, 另一端耦合二 极管正极, 并通过调压可控开关耦合到 LED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
压可控开关的控制端耦合到所述恒流驱动芯片。
12. 如权利要求 10所述的液晶显示装置, 其中, 所述比较模块包括比较器, 所述比较器的同向输入端耦合有基准电压,反向输入端耦合有将 PWM调光信号 转化成等效电压的转换单元; 所述升压模块的控制端和所述 LED背光驱动电路 的接地端之间串接有切换可控开关;
所述基准电压的大小小于或等于所述预设的阈值对应的 PWM调光信号的 等效电压, 当所述转换单元输出的等效电压小于所述基准电压时, 所述比较器 驱动所述切换可控开关关断。
13. 如权利要求 12所述的液晶显示装置, 其中, 所述转换单元包括滤波电 阻和滤波电容; 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。
14. 如权利要求 13所述的液晶显示装置, 其中, 所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端耦合电源模块, 另一端耦合二 极管正极, 并通过调压可控开关耦合到 LED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 压可控开关的控制端耦合到所述恒流驱动芯片。
15. 如权利要求 10所述的液晶显示装置, 其中, 所述 N-1个升压模块的控 制端耦合有比较模块, 当所述 PWM调光信号的占空比小于或等于 (100/N ) % 时, 所述比较模块驱动相应的升压模块关断。
16. 如权利要求 15所述的液晶显示装置, 其中, 所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端耦合电源模块, 另一端耦合二 极管正极, 并通过调压可控开关耦合到 LED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 压可控开关的控制端耦合到所述恒流驱动芯片。
17. 如权利要求 10所述的液晶显示装置, 其中, 所述恒流驱动芯片包括控
制所述升压模块输出电压的控制单元, 以及调节 LED灯条亮度的侦测单元, 所 述侦测单元包括调光可控开关, 调光可控开关的输入端耦合到所述 LED灯条的 负极;其输出端通过一分压电阻耦合到 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; 所述每个升压模块对应一个恒流 驱动芯片, 相应的, 所述 LED灯条分成 N组, 每个恒流驱动芯片控制一组 LED 灯条。
18. 如权利要求 10所述的液晶显示装置, 其中, 所述升压模块有两个, 其 中一个升压模块的控制端耦合有比较模块,
所述比较模块包括比较器, 所述比较器的同向输入端耦合有基准电压, 反 向输入端耦合有将 PWM调光信号转化成等效电压的转换单元;所述升压模块的 控制端和所述 LED背光驱动电路的接地端之间串接有切换可控开关; 所述转换 单元包括滤波电阻和滤波电容;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;
所述基准电压的大小小于或等于 50%占空比对应的 PWM调光信号的等效 电压, 当所述转换单元输出的等效电压小于所述基准电压时, 所述比较器驱动 所述切换可控开关关断。
所述升压模块包括电感、 二极管、 调压可控开关和电容; 所述电感的一端 耦合电源模块, 另一端耦合二极管正极, 并通过调压可控开关耦合到 LED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;
所述恒流驱动芯片包括控制单元, 以及调节 LED灯条亮度的侦测单元, 所 述调压可控开关的控制端耦合到所述控制单元; 所述侦测单元包括调光可控开 关, 调光可控开关的输入端耦合到所述 LED灯条的负极; 其输出端通过一分压 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;
所述每个升压模块对应一个恒流驱动芯片, 相应的, 所述 LED灯条分成两 组, 每个恒流驱动芯片控制一组 LED灯条。
19. 一种 LED背光驱动电路的驱动方法,所述 LED背光驱动电路包括电源 模块、 LED灯条, 以及用于调整 LED灯条亮度的恒流驱动芯片, 所述恒流驱动 芯片耦合有 PWM调光信号; 所述电源模块和 LED灯条之间串接有 N个并联设 置的升压模块; 所述驱动方法包括:
A、 预设一个 PWM调光信号的占空比的阈值;
B、检测 PWM调光信号的占空比, 当占空比小于预设的阈值时, 转步骤 C; 否则, 转步骤 D;
C、 控制至少一个升压模块关断; 返回步骤 A;
D、 维持升压模块正常运行; 返回步骤 A;
所述 N为大于或等于 2的整数。
20. 如权利要求 19所述的 LED背光驱动电路的驱动方法, 其中, 所述步骤 A中, 保存每个升压模块的最大输出功率 W。,
所述步骤 B中的阈值有 N-1个, 且每个阈值都是 W。的整数倍功率对应的 PWM调光信号的占空比;
所述步骤 C中, 判断当前 LED灯条的总需求功率 W, 如果 W小于或等于 ( N-x ) W0, 则关断 x个升压模块; 返回步骤 A;
X为小于 N的正整数。
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