WO2013010351A1 - Pwm调光电路 - Google Patents

Pwm调光电路 Download PDF

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Publication number
WO2013010351A1
WO2013010351A1 PCT/CN2011/080948 CN2011080948W WO2013010351A1 WO 2013010351 A1 WO2013010351 A1 WO 2013010351A1 CN 2011080948 W CN2011080948 W CN 2011080948W WO 2013010351 A1 WO2013010351 A1 WO 2013010351A1
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Prior art keywords
mos transistor
current
source
operational amplifier
drain
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PCT/CN2011/080948
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English (en)
French (fr)
Inventor
高新明
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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 DE112011105356.8T priority Critical patent/DE112011105356T5/de
Priority to US13/379,738 priority patent/US8760076B2/en
Publication of WO2013010351A1 publication Critical patent/WO2013010351A1/zh
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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

Definitions

  • the invention relates to PWM (Pulse Width) Modulation, pulse width modulation) dimming technology, especially related to a PWM dimming circuit.
  • PWM Pulse Width Modulation, pulse width modulation
  • PWM dimming Pulse-Voltage dimming
  • analog dimming dimming
  • digital dimming Many LEDs on the market (Light Emitting Diode (LED) drivers are capable of supporting one or more of these dimming techniques.
  • the PWM dimming method is a dimming technique that repeatedly switches a white LED driver using a simple digital pulse.
  • the application's system only needs to provide wide and narrow digital pulses to easily change the output current to adjust the white light. The brightness of the LED.
  • PWM dimming or analog dimming in existing LED driver circuits usually uses a balanced chip (Balance) IC), through the internal module of the chip to adjust the duty cycle (Duty) of the output current, to achieve the purpose of adjusting the brightness of the LED.
  • the circuit of the balanced chip is very complicated, and a corresponding dimming module needs to be disposed inside the chip.
  • the main function is to make a product of the input PWM signal and the driving signal of the field effect transistor (MOSFET) for realizing current balancing.
  • MOSFET field effect transistor
  • the FET is switched according to the PWM signal, thereby controlling the duty ratio of the LED to be consistent with the duty ratio of the input PWM signal, thereby realizing PWM dimming or analog dimming, which may cause an increase in circuit design difficulty and increase Cost of production.
  • the main object of the present invention is to provide a PWM dimming circuit that simplifies circuit design and reduces production costs.
  • the invention provides a PWM dimming circuit, comprising a switching unit, a current generating unit, a mirror current source, a multi-output unit, a plurality of current balancing units and a plurality of LED light strings, wherein the switching unit is configured to receive a PWM signal, And the PWM signal is controlled to be turned on and off; the current generating unit is connected to the switch unit, and configured to generate a current of a predetermined magnitude when the switch unit is turned on; the mirror current source is connected to the current generating unit, And is used for accessing the current generated by the current generating unit and generating a mirror current; the multiple output unit is connected to the mirror current source for accessing the mirror current and multiplexing the mirror current;
  • the number of the current balancing units is the same as the number of the LED light strings, and the plurality of current balancing units are respectively connected between the multiple output units and the plurality of LED strings for adjusting the resistance of the LED strings. balance.
  • the switching unit is a MOS tube or a relay.
  • the switching unit is a MOS transistor (11) whose gate is for receiving a PWM signal, the drain is connected to the current generating unit, and the source is grounded.
  • the current generating unit includes a resistor (RSET), an operational amplifier (OP1), and a MOS transistor (Q1); the resistor (RSET) has one end connected to the switching unit and the other end connected to the operational amplifier (OP1)
  • the inverting input terminal and the source of the MOS transistor (Q1); the non-inverting input terminal of the operational amplifier (OP1) is connected to a first reference voltage, and the output terminal is connected to the gate of the MOS transistor (Q1);
  • the drain of the MOS transistor (Q1) is connected to the mirror current source.
  • the mirror current source comprises a MOS transistor (Q2) and a MOS transistor (Q3); a drain of the MOS transistor (Q2) is connected to a drain of the MOS transistor (Q1); and the MOS transistor (Q2) The source and the gate are respectively connected to the source and the gate of the MOS transistor (Q3); the drain of the MOS transistor (Q3) is connected to the multiple output unit; the drain of the MOS transistor (Q2) The pole and the gate are connected by wires.
  • the multiple output unit comprises an operational amplifier (OP2), a MOS transistor (Q4) and a plurality of MOS transistors (Q6); an inverting input terminal of the operational amplifier (OP2) and a drain of the MOS transistor (Q4) a pole is respectively connected to a drain of the MOS transistor (Q3); an output terminal of the operational amplifier (OP2) is connected to a gate of a MOS transistor (Q4) and a plurality of MOS transistors (Q6); the operational amplifier (OP2) a non-inverting input terminal of a second reference voltage; a source of the MOS transistor (Q4), a source of the plurality of MOS transistors (Q6) are respectively connected to the source of the MOS transistor (11) in the switching unit;
  • the number of MOS tubes (Q6) is the same as the number of current balancing units, and the drains of the plurality of MOS tubes (Q6) are respectively connected to a plurality of current balancing units.
  • the current balancing unit comprises a MOS transistor (Q5) and an operational amplifier (OP3); an inverting input terminal of the operational amplifier (OP3) and a source of the MOS transistor (Q5) and the MOS transistor (Q6) a drain connection, an output of the operational amplifier (OP3) is coupled to a gate of the MOS transistor (Q5); a non-inverting input of the operational amplifier (OP3) is coupled to a second reference voltage, the MOS The drain of the tube (Q5) is connected to the LED string.
  • the MOS transistors (11), (Q1), (Q2), (Q3), (Q4), (Q5), and (Q6) are all N. MOS.
  • the first reference voltage is 1.2V and the second reference voltage is 0.3V.
  • the PWM dimming circuit is an integrated circuit, and a source of the MOS transistor (Q1) is a reset end of the integrated circuit.
  • the invention also provides a PWM dimming circuit, comprising a switching unit, a current generating unit, a mirror current source, a multi-output unit, a plurality of current balancing units and a plurality of LED light strings, wherein the switching unit is a MOS tube (11) a gate for receiving a PWM signal, a drain connected to the current generating unit, a source grounded, and controlled by the PWM signal; the current generating unit is coupled to the switching unit for use in the switching unit Generating a predetermined magnitude of current when conducting; the mirror current source is coupled to the current generating unit for accessing a current generated by the current generating unit and generating a mirror current; the multiple output unit and the a mirror current source connection for accessing the mirror current and multi-outputting the mirror current; the number of the current balancing units is the same as the number of the LED strings, and the plurality of current balancing units are respectively connected to the multiple output units Between the plurality of LED strings, it is used to adjust its own resistance to
  • the current generating unit includes a resistor (RSET), an operational amplifier (OP1), and a MOS transistor (Q1); the resistor (RSET) has one end connected to the switching unit and the other end connected to the operational amplifier (OP1)
  • the inverting input terminal and the source of the MOS transistor (Q1); the non-inverting input terminal of the operational amplifier (OP1) is connected to a first reference voltage, and the output terminal is connected to the gate of the MOS transistor (Q1);
  • the drain of the MOS transistor (Q1) is connected to the mirror current source.
  • the mirror current source comprises a MOS transistor (Q2) and a MOS transistor (Q3); a drain of the MOS transistor (Q2) is connected to a drain of the MOS transistor (Q1); and the MOS transistor (Q2) The source and the gate are respectively connected to the source and the gate of the MOS transistor (Q3); the drain of the MOS transistor (Q3) is connected to the multiple output unit; the drain of the MOS transistor (Q2) The pole and the gate are connected by wires.
  • the multiple output unit comprises an operational amplifier (OP2), a MOS transistor (Q4) and a plurality of MOS transistors (Q6); an inverting input terminal of the operational amplifier (OP2) and a drain of the MOS transistor (Q4) a pole is respectively connected to a drain of the MOS transistor (Q3); an output terminal of the operational amplifier (OP2) is connected to a gate of a MOS transistor (Q4) and a plurality of MOS transistors (Q6); the operational amplifier (OP2) a non-inverting input terminal of a second reference voltage; a source of the MOS transistor (Q4), a source of the plurality of MOS transistors (Q6) are respectively connected to the source of the MOS transistor (11) in the switching unit;
  • the number of MOS tubes (Q6) is the same as the number of current balancing units, and the drains of the plurality of MOS tubes (Q6) are respectively connected to a plurality of current balancing units.
  • the current balancing unit comprises a MOS transistor (Q5) and an operational amplifier (OP3); an inverting input terminal of the operational amplifier (OP3) and a source of the MOS transistor (Q5) and the MOS transistor (Q6) a drain connection, an output of the operational amplifier (OP3) is coupled to a gate of the MOS transistor (Q5); a non-inverting input of the operational amplifier (OP3) is coupled to a second reference voltage, the MOS The drain of the tube (Q5) is connected to the LED string.
  • the MOS transistors (11), (Q1), (Q2), (Q3), (Q4), (Q5), and (Q6) are all N. MOS.
  • the first reference voltage is 1.2V and the second reference voltage is 0.3V.
  • the PWM dimming circuit is an integrated circuit, and a source of the MOS transistor (Q1) is a reset end of the integrated circuit.
  • the PWM dimming circuit of the present invention does not need to provide a dimming module in the prior art, and realizes dimming of the LED light string through a simple circuit, thereby reducing the design difficulty of the circuit and the production cost.
  • FIG. 1 is a schematic structural view of a first embodiment of a PWM dimming circuit of the present invention
  • FIG. 2 is a detailed circuit diagram of the PWM dimming circuit of the first embodiment.
  • the PWM dimming circuit 10 includes a switching unit 11, a current generating unit 12, a mirror current source 13, a multi-output unit 14, a plurality of current balancing units 15, and a plurality of LED strings 16.
  • the switch unit 11 is configured to receive a PWM signal and control the on and off by the PWM signal to adjust the duty cycle of the current flowing through the LED string 16.
  • the current generating unit 12 is connected to the switching unit 11 for generating a current of a predetermined magnitude when the switching unit 11 is turned on.
  • the mirror current source 13 is connected to the current generating unit 12 for accessing the current generated by the current generating unit 12 and generating a mirror current.
  • the multi-output unit 14 is connected to the mirror current source 13 for accessing the mirror current and multiplexing the mirror current.
  • the number of current balancing units 15 is the same as the number of LED strings.
  • a plurality of current balancing units are respectively connected between the multi-output unit 14 and the plurality of LED strings 16 for adjusting their own resistance to maintain current balance of the respective LED strings.
  • the PWM dimming circuit 10 can be applied to an LED driving circuit, which is connected to a PWM signal generating circuit (not shown), and adjusts the duty ratio of the current generated by the current generating unit 12 by adjusting the duty ratio of the PWM signal. In order to adjust the duty ratio of the mirror current, thereby adjusting the duty ratio of the current flowing through the LED string 16, the PWM dimming is realized.
  • the above-described switching unit 11 is a MOS transistor. In other embodiments, the above-mentioned switch unit 11 can also be other switching devices such as relays.
  • the gate of the MOS transistor 11 is for receiving a PWM signal, the drain is connected to the current generating unit 12, and the source is grounded.
  • the MOS transistor 11 can be N MOS.
  • the current generating unit 12 includes a resistor RSET, an operational amplifier OP1, and a MOS transistor Q1.
  • One end of the resistor RSET is connected to the drain of the MOS transistor 11, and the other end is connected to the inverting input terminal of the operational amplifier OP1 and the source of the MOS transistor Q1.
  • the non-inverting input terminal of the operational amplifier OP1 is connected to a first reference voltage, and the output terminal is connected to the gate of the MOS transistor Q1.
  • the first reference voltage described above may be 1.2V.
  • the drain of the MOS transistor Q1 is connected to the mirror current source 13.
  • the mirror current source 13 includes a MOS transistor Q2 and a MOS transistor Q3.
  • the drain of the MOS transistor Q2 is connected to the drain of the MOS transistor Q1.
  • the drain and the gate of the MOS transistor Q2 are connected by wires.
  • the source and the gate of the MOS transistor Q2 are respectively connected to the source and the gate of the MOS transistor Q3.
  • the drain of the MOS transistor Q3 is connected to the multi-output unit 14.
  • the above-described multiple output unit 14 includes an operational amplifier OP2, a MOS transistor Q4, and a plurality of MOS transistors Q6.
  • the inverting input terminal of the operational amplifier OP2 and the drain of the MOS transistor Q4 are respectively connected to the drain of the MOS transistor Q3.
  • the output terminal of the operational amplifier OP2 is connected to the MOS transistor Q4 and the gates of the plurality of MOS transistors Q6.
  • the non-inverting input of the operational amplifier OP2 is connected to a second reference voltage.
  • the second reference voltage described above may be 0.3V.
  • the MOS transistor Q4 and the sources of the plurality of MOS transistors Q6 are connected to the sources of the MOS transistors 11, respectively.
  • the number of the MOS transistors Q6 is the same as the number of the current balancing units 15, and the drains of the plurality of MOS transistors Q6 are connected to the plurality of current balancing units 15, respectively.
  • the current balancing unit 15 includes a MOS transistor Q5 and an operational amplifier OP3.
  • the inverting input terminal of the operational amplifier OP3 and the source of the MOS transistor Q5 are respectively connected to the drain of the MOS transistor Q6, and the output terminal of the operational amplifier OP3 is connected to the gate of the MOS transistor Q5; the positive phase of the operational amplifier OP3
  • the input terminal is connected to the second reference voltage.
  • the drain of the MOS transistor Q5 is connected to the LED string 16.
  • the above MOS tubes (Q1), (Q2), (Q3), (Q4), (Q5), and (Q6) are all N MOS.
  • the anodes of the LED string 16 receive an input voltage Vin, and the cathodes are respectively connected to the current balancing unit 15.
  • the PWM dimming circuit 10 can be an integrated circuit, and the source of the MOS transistor Q1 is the reset end of the integrated circuit.
  • the MOS transistor 11 When the PWM signal is at a high level, the MOS transistor 11 is turned on. According to the virtual short characteristic of the non-inverting input terminal and the inverting input terminal of the operational amplifier OP1 of the current generating unit 12, the inverting input terminal and the non-inverting input terminal are approximately short-circuited. Therefore, the inverting input terminal of the operational amplifier OP1 and the source voltage of the MOS transistor Q1 can be regarded as 1.2V. In addition, the voltage difference between the gate and the source of the MOS transistor Q1 satisfies the conduction condition, so the MOS transistor Q1 Turned on, the current flowing through the MOS transistor Q1 is 1.2V/Rset, where Rset represents the resistance value of the resistor RSET.
  • the MOS transistor Q2 and the MOS transistor Q3 constitute a mirror current source 13, so that the current flowing through the MOS transistor Q1 and the MOS transistor Q4 is the same.
  • the non-inverting input terminals of the above operational amplifiers OP2 and OP3 are all reference voltages of 0.3V, based on the virtual short characteristics of the positive phase input terminal and the inverting input terminal of the operational amplifiers OP2 and OP3, and the voltages of the inverting input terminals of both are also It is 0.3V. Since the drains of the MOS transistors Q4 and Q6 are connected to the inverting input terminals of the operational amplifiers OP2 and OP3, respectively, the drain voltages of the MOS transistors Q4 and Q6 are the same. Further, since the gate and source voltages of the MOS transistors Q4 and Q6 are also the same, the impedances of the MOS transistors Q4 and Q6 are the same, and the magnitude of the current flowing through them is also the same.
  • the MOS transistor Q5 of the current balancing unit 15 corresponds to a resistor here, and the MOS transistor Q5 is divided in series with the MOS transistor Q6 of the above-described multiple output unit 14 to share the voltage of the LED light string 16. Since the turn-on voltage drop Vf of each LED string 16 may be different, the voltage of each current balancing unit 15 may be different after the same input voltage Vin is stepped down by each LED string 16.
  • the source voltage of the MOS transistor Q5 is 0.3V, so the operational amplifier OP3 automatically adjusts the resistance of the MOS transistor Q5 by controlling the voltage at its output terminal, thereby realizing the same current of each LED string 16 in parallel.
  • the PWM dimming circuit can adjust the duty ratio of the current flowing through the LED string 16 by adjusting the duty ratio of the PWM signal to realize PWM dimming.
  • the above-mentioned PWM dimming circuit 10 does not need to provide a dimming module in the prior art, and realizes dimming of the LED string by a simple circuit, thereby reducing the design difficulty of the circuit and the cost of production. If the PWM dimming circuit 10 is packaged into an integrated circuit, the volume can be reduced, which is more convenient and practical.

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Abstract

本发明揭示了一种PWM调光电路，其包括开关单元、电流产生单元、镜像电流源、多路输出单元、多个电流平衡单元以及多个LED灯串。所述开关单元用于接收一PWM信号，并由所述PWM信号控制通断。所述电流产生单元与所述开关单元连接，用于在开关单元导通时产生一预定大小的电流。所述镜像电流源与所述电流产生单元连接，用于接入该电流产生单元产生的电流，并产生一镜像电流。所述多路输出单元与所述镜像电流源连接，用于接入该镜像电流并将所述镜像电流进行多路输出。多个电流平衡单元分别连接于多路输出单元与多个LED灯串之间。本发明的PWM调光电路降低了电路的设计难度以及生产的成本，方便实用。

Description

PWM调光电路
技术领域
本发明涉及到PWM（Pulse Width Modulation，脉冲宽度调节）调光技术，特别涉及到一种PWM调光电路。
背景技术
目前调光技术主要有三种：PWM调光、模拟调光以及数字调光。市场上很多LED（Light Emitting Diode，发光二极管）驱动器都能够支持其中的一种或多种调光技术。PWM调光方式是一种利用简单的数字脉冲反复开关白光LED驱动器的调光技术。应用者的系统只需要提供宽、窄不同的数字式脉冲，即可简单地实现改变输出电流，从而调节白光 LED 的亮度。
在现有的LED驱动电路中的PWM调光或模拟调光通常使用的是平衡芯片（Balance IC），通过该芯片的内部模块调节输出电流的占空比（Duty），达到调节LED的亮度的目的。通常平衡芯片的电路非常复杂，而且需要在该芯片的内部设置相应的调光（Dimming）模块，主要功能就是把输入的PWM信号和实现电流平衡的场效应管（MOSFET）的驱动信号做一个乘积，使场效应管根据PWM信号做开关动作，从而控制LED的占空比与输入的PWM信号的占空比一致，实现PWM调光或模拟调光，如此可造成电路设计难度增加，以及增加了生产成本。
发明内容
本发明的主要目的为提供一种PWM调光电路，简便了电路设计以及降低了生产成本。
本发明提出一种PWM调光电路，包括开关单元、电流产生单元、镜像电流源、多路输出单元、多个电流平衡单元以及多个LED灯串，所述开关单元用于接收一PWM信号，并由所述PWM信号控制通断；所述电流产生单元与所述开关单元连接，用于在开关单元导通时产生一预定大小的电流；所述镜像电流源与所述电流产生单元连接，用于接入该电流产生单元产生的电流，并产生一镜像电流；所述多路输出单元与所述镜像电流源连接，用于接入该镜像电流并将所述镜像电流进行多路输出；上述电流平衡单元的数量与上述LED灯串的数量相同，多个电流平衡单元分别连接于多路输出单元与多个LED灯串之间，用于调整自身的电阻而维持各个LED灯串的电流平衡。
优选地，所述开关单元为MOS管或继电器。
优选地，所述开关单元为MOS管（11），其栅极用于接收一PWM信号，漏极与电流产生单元连接，源极接地。
优选地，所述电流产生单元包括电阻（RSET）、运算放大器（OP1）以及MOS管（Q1）；所述电阻（RSET）一端与所述开关单元连接，另一端连接到该运算放大器（OP1）的反相输入端以及MOS管（Q1）的源极；所述运算放大器（OP1）的正相输入端接入一第一参考电压，输出端连接所述MOS管（Q1）的栅极；所述MOS管（Q1）的漏极连接至所述镜像电流源。
优选地，所述镜像电流源包括MOS管（Q2）以及MOS管（Q3）；所述MOS管（Q2）的漏极与所述MOS管（Q1）的漏极连接；所述MOS管（Q2）的源极以及栅极分别与MOS管（Q3）的源极以及栅极对接；所述MOS管（Q3）的漏极与所述多路输出单元连接；所述MOS管（Q2）的漏极与栅极通过导线相接。
优选地，所述多路输出单元包括运算放大器（OP2）、MOS管（Q4）以及多个MOS管（Q6）；所述运算放大器（OP2）的反相输入端以及MOS管（Q4）的漏极分别与所述MOS管（Q3）的漏极连接；所述运算放大器（OP2）的输出端与MOS管（Q4）和多个MOS管（Q6）的栅极连接；所述运算放大器（OP2）的正相输入端一第二参考电压；所述MOS管（Q4）的源极、多个MOS管（Q6）的源极分别连接至所述开关单元中MOS管（11）的源极；MOS管（Q6）的数量与电流平衡单元的数量相同，多个MOS管（Q6）的漏极分别连接多个电流平衡单元。
优选地，所述电流平衡单元包括MOS管（Q5）以及运算放大器（OP3）；所述运算放大器（OP3）的反相输入端以及MOS管（Q5）的源极分别与所述MOS管（Q6）的漏极连接，所述运算放大器（OP3）的输出端与MOS管（Q5）的栅极连接；所述运算放大器（OP3）的正相输入端接入一第二参考电压，所述MOS管（Q5）的漏极连接LED灯串。
优选地，所述MOS管（11）、（Q1）、（Q2）、（Q3）、（Q4）、（Q5）以及（Q6）都为N MOS。
优选地，所述第一参考电压为1.2V，所述第二参考电压为0.3V。
优选地，所述PWM调光电路为集成电路，所述MOS管（Q1）的源极为所述集成电路的复位端。
本发明还提出一种PWM调光电路，包括开关单元、电流产生单元、镜像电流源、多路输出单元、多个电流平衡单元以及多个LED灯串，所述开关单元为MOS管（11），其栅极用于接收一PWM信号，漏极与电流产生单元连接，源极接地，并由所述PWM信号控制通断；所述电流产生单元与所述开关单元连接，用于在开关单元导通时产生一预定大小的电流；所述镜像电流源与所述电流产生单元连接，用于接入该电流产生单元产生的电流，并产生一镜像电流；所述多路输出单元与所述镜像电流源连接，用于接入该镜像电流并将所述镜像电流进行多路输出；上述电流平衡单元的数量与上述LED灯串的数量相同，多个电流平衡单元分别连接于多路输出单元与多个LED灯串之间，用于调整自身的电阻而维持各个LED灯串的电流平衡。
优选地，所述电流产生单元包括电阻（RSET）、运算放大器（OP1）以及MOS管（Q1）；所述电阻（RSET）一端与所述开关单元连接，另一端连接到该运算放大器（OP1）的反相输入端以及MOS管（Q1）的源极；所述运算放大器（OP1）的正相输入端接入一第一参考电压，输出端连接所述MOS管（Q1）的栅极；所述MOS管（Q1）的漏极连接至所述镜像电流源。
优选地，所述镜像电流源包括MOS管（Q2）以及MOS管（Q3）；所述MOS管（Q2）的漏极与所述MOS管（Q1）的漏极连接；所述MOS管（Q2）的源极以及栅极分别与MOS管（Q3）的源极以及栅极对接；所述MOS管（Q3）的漏极与所述多路输出单元连接；所述MOS管（Q2）的漏极与栅极通过导线相接。
优选地，所述多路输出单元包括运算放大器（OP2）、MOS管（Q4）以及多个MOS管（Q6）；所述运算放大器（OP2）的反相输入端以及MOS管（Q4）的漏极分别与所述MOS管（Q3）的漏极连接；所述运算放大器（OP2）的输出端与MOS管（Q4）和多个MOS管（Q6）的栅极连接；所述运算放大器（OP2）的正相输入端一第二参考电压；所述MOS管（Q4）的源极、多个MOS管（Q6）的源极分别连接至所述开关单元中MOS管（11）的源极；MOS管（Q6）的数量与电流平衡单元的数量相同，多个MOS管（Q6）的漏极分别连接多个电流平衡单元。
优选地，所述电流平衡单元包括MOS管（Q5）以及运算放大器（OP3）；所述运算放大器（OP3）的反相输入端以及MOS管（Q5）的源极分别与所述MOS管（Q6）的漏极连接，所述运算放大器（OP3）的输出端与MOS管（Q5）的栅极连接；所述运算放大器（OP3）的正相输入端接入一第二参考电压，所述MOS管（Q5）的漏极连接LED灯串。
优选地，所述MOS管（11）、（Q1）、（Q2）、（Q3）、（Q4）、（Q5）以及（Q6）都为N MOS。
优选地，所述第一参考电压为1.2V，所述第二参考电压为0.3V。
优选地，所述PWM调光电路为集成电路，所述MOS管（Q1）的源极为所述集成电路的复位端。
本发明的PWM调光电路无需设置现有技术中的调光模块，通过简便的电路实现对LED灯串的调光，降低了电路的设计难度以及生产的成本。
附图说明
图1 是本发明PWM调光电路第一实施例的结构示意图；
图2 是第一实施例PWM调光电路的具体电路图。
本发明目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
图1是本发明第一实施例中PWM调光电路10的结构示意图。该PWM调光电路10包括开关单元11、电流产生单元12、镜像电流源13、多路输出单元14、多个电流平衡单元15以及多个LED灯串16。上述开关单元11用于接收一PWM信号，并由该PWM信号控制通断，从而调节流过LED灯串16的电流的占空比。上述电流产生单元12与上述开关单元11连接，用于在开关单元11导通时产生一预定大小的电流。上述镜像电流源13与上述电流产生单元12连接，用于接入该电流产生单元12产生的电流，并产生一镜像电流。上述多路输出单元14与上述镜像电流源13连接，用于接入该镜像电流并将所述镜像电流进行多路输出。电流平衡单元15的数量与LED灯串的数量相同。多个电流平衡单元分别连接于多路输出单元14与多个LED灯串16之间，用于调整自身的电阻而维持各个LED灯串的电流平衡。
上述PWM调光电路10可应用于LED驱动电路中，其与一PWM信号产生电路（图未示）连接，通过调节PWM信号的占空比来调节电流产生单元12所产生的电流的占空比，从而调节镜像电流的占空比，进而调节流过LED灯串16的电流的占空比，实现PWM调光。
图2是第一实施例PWM调光电路的具体电路图。参照图2，上述开关单元11为MOS管。其他实施例中，上述开关单元11也可为继电器等其它开关器件。该MOS管11的栅极用于接收一PWM信号，漏极与电流产生单元12连接，源极接地。该MOS管11可为N MOS。
上述电流产生单元12包括电阻RSET、运算放大器OP1以及MOS管Q1。该电阻RSET一端与上述MOS管11的漏极连接，另一端连接到该运算放大器OP1的反相输入端以及MOS管Q1的源极。该运算放大器OP1的正相输入端接入一第一参考电压，输出端连接该MOS管Q1的栅极。上述第一参考电压可为1.2V。该MOS管Q1的漏极连接至所述镜像电流源13。
上述镜像电流源13包括MOS管Q2以及MOS管Q3。该MOS管Q2的漏极与上述MOS管Q1的漏极连接。该MOS管Q2的漏极与栅极通过导线相接。该MOS管Q2的源极以及栅极分别与MOS管Q3的源极以及栅极对接。该MOS管Q3的漏极与该多路输出单元14连接。
上述多路输出单元14包括运算放大器OP2、MOS管Q4和多个MOS管Q6。该运算放大器OP2的反相输入端以及MOS管Q4的漏极分别与上述MOS管Q3的漏极连接。该运算放大器OP2的输出端与MOS管Q4和多个MOS管Q6的栅极连接。该运算放大器OP2的正相输入端接入一第二参考电压。上述第二参考电压可为0.3V。该MOS管Q4、多个MOS管Q6的源极分别连接至上述MOS管11的源极。上述MOS管Q6的数量与电流平衡单元15的数量相同，多个MOS管Q6的漏极分别连接多个电流平衡单元15。
上述电流平衡单元15包括MOS管Q5以及运算放大器OP3。该运算放大器OP3的反相输入端以及MOS管Q5的源极分别与上述MOS管Q6的漏极连接，该运算放大器OP3的输出端与MOS管Q5的栅极连接；该运算放大器OP3的正相输入端接入上述第二参考电压。该MOS管Q5的漏极连接LED灯串16。上述MOS管（Q1）、（Q2）、（Q3）、（Q4）、（Q5）以及（Q6）都为N MOS。
上述LED灯串16的阳极都接收一输入电压Vin，阴极分别连接上述电流平衡单元15。
上述PWM调光电路10可为集成电路，所述MOS管Q1的源极为上述集成电路的复位端。
上述PWM调光电路的工作原理如下：
当PWM信号为一高电平时，上述MOS管11导通，根据电流产生单元12的运算放大器OP1的正相输入端与反相输入端的虚短特性，其反相输入端与同相输入端近似短路，因此运算放大器OP1的反相输入端和MOS管Q1的源极电压可看作是1.2V，此外，MOS管Q1的栅极与源极之间的电压差满足导通条件，因此MOS管Q1导通，流过MOS管Q1的电流为1.2V/Rset，其中Rset表示电阻RSET的电阻值。上述MOS管Q2和MOS管Q3组成镜像电流源13，使得流过MOS管Q1和MOS管Q4的电流大小相同。此外，上述运算放大器OP2和OP3的同相输入端连接都是0.3V的参考电压，基于运算放大器OP2和OP3正相输入端与反相输入端的虚短特性，两者的反相输入端的电压也都是0.3V，因MOS管Q4和Q6的漏极分别连接运算放大器OP2和OP3的反相输入端，故MOS管Q4和Q6的漏极电压相同。另外，MOS管Q4和Q6的栅极和源极电压也相同，因此MOS管Q4和Q6的阻抗相同，流过两者的电流大小也相同。
该电流平衡单元15的MOS管Q5在此处相当于电阻，该MOS管Q5与上述多路输出单元14中的MOS管Q6组成串联分压，分担LED灯串16的电压。由于各个LED灯串16的导通压降Vf可能会有差异，因此同一输入电压Vin经过各个LED灯串16降压后，各个电流平衡单元15的电压可能会有所不同。而该MOS管Q5的源极电压都为0.3V，因此运算放大器OP3会通过控制其输出端的电压而对MOS管Q5的电阻进行自动调整，从而实现并联的各个LED灯串16的电流相同。
当PWM信号为一低电平时，上述MOS管11断开，无电流流过MOS管Q1，同理MOS管Q4以及MOS管Q6为断开，LED灯串16不亮。因此，上述PWM调光电路可以通过调节PWM信号的占空比来调节流过LED灯串16的电流的占空比，实现PWM调光。
上述PWM调光电路10无需设置现有技术中的调光模块，通过简便的电路实现对LED灯串的调光，降低了电路的设计难度以及生产的成本。如将该PWM调光电路10封装成集成电路，还可减小体积，更方便实用。
以上所述仅为本发明的优选实施例，并非因此限制本发明的专利范围，凡是利用本发明说明书及附图内容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本发明的专利保护范围内。

Claims (18)

  1. 一种PWM调光电路，其特征在于，包括开关单元、电流产生单元、镜像电流源、多路输出单元、多个电流平衡单元以及多个LED灯串，所述开关单元用于接收一PWM信号，并由所述PWM信号控制通断；所述电流产生单元与所述开关单元连接，用于在开关单元导通时产生一预定大小的电流；所述镜像电流源与所述电流产生单元连接，用于接入该电流产生单元产生的电流，并产生一镜像电流；所述多路输出单元与所述镜像电流源连接，用于接入该镜像电流并将所述镜像电流进行多路输出；上述电流平衡单元的数量与上述LED灯串的数量相同，多个电流平衡单元分别连接于多路输出单元与多个LED灯串之间，用于调整自身的电阻而维持各个LED灯串的电流平衡。
  2. 根据权利要求1所述的PWM调光电路，其特征在于，所述开关单元为MOS管或继电器。
  3. 根据权利要求2所述的PWM调光电路，其特征在于，所述开关单元为MOS管（11），其栅极用于接收一PWM信号，漏极与电流产生单元连接，源极接地。
  4. 根据权利要求1至3中任一项所述的PWM调光电路，其特征在于，所述电流产生单元包括电阻（RSET）、运算放大器（OP1）以及MOS管（Q1）；所述电阻（RSET）一端与所述开关单元连接，另一端连接到该运算放大器（OP1）的反相输入端以及MOS管（Q1）的源极；所述运算放大器（OP1）的正相输入端接入一第一参考电压，输出端连接所述MOS管（Q1）的栅极；所述MOS管（Q1）的漏极连接至所述镜像电流源。
  5. 根据权利要求4所述的PWM调光电路，其特征在于，所述镜像电流源包括MOS管（Q2）以及MOS管（Q3）；所述MOS管（Q2）的漏极与所述MOS管（Q1）的漏极连接；所述MOS管（Q2）的源极以及栅极分别与MOS管（Q3）的源极以及栅极对接；所述MOS管（Q3）的漏极与所述多路输出单元连接；所述MOS管（Q2）的漏极与栅极通过导线相接。
  6. 根据权利要求5所述的PWM调光电路，其特征在于，所述多路输出单元包括运算放大器（OP2）、MOS管（Q4）以及多个MOS管（Q6）；所述运算放大器（OP2）的反相输入端以及MOS管（Q4）的漏极分别与所述MOS管（Q3）的漏极连接；所述运算放大器（OP2）的输出端与MOS管（Q4）和多个MOS管（Q6）的栅极连接；所述运算放大器（OP2）的正相输入端一第二参考电压；所述MOS管（Q4）的源极、多个MOS管（Q6）的源极分别连接至所述开关单元中MOS管（11）的源极；MOS管（Q6）的数量与电流平衡单元的数量相同，多个MOS管（Q6）的漏极分别连接多个电流平衡单元。
  7. 根据权利要求6所述的PWM调光电路，其特征在于，所述电流平衡单元包括MOS管（Q5）以及运算放大器（OP3）；所述运算放大器（OP3）的反相输入端以及MOS管（Q5）的源极分别与所述MOS管（Q6）的漏极连接，所述运算放大器（OP3）的输出端与MOS管（Q5）的栅极连接；所述运算放大器（OP3）的正相输入端接入一第二参考电压，所述MOS管（Q5）的漏极连接LED灯串。
  8. 根据权利要求7所述的PWM调光电路，其特征在于，所述MOS管（11）、（Q1）、（Q2）、（Q3）、（Q4）、（Q5）以及（Q6）都为N MOS。
  9. 根据权利要求6或7所述的PWM调光电路，其特征在于，所述第一参考电压为1.2V，所述第二参考电压为0.3V。
  10. 根据权利要求1所述的PWM调光电路，其特征在于，所述PWM调光电路为集成电路，所述MOS管（Q1）的源极为所述集成电路的复位端。
  11. 一种PWM调光电路，其特征在于，包括开关单元、电流产生单元、镜像电流源、多路输出单元、多个电流平衡单元以及多个LED灯串，所述开关单元为MOS管（11），其栅极用于接收一PWM信号，漏极与电流产生单元连接，源极接地，并由所述PWM信号控制通断；所述电流产生单元与所述开关单元连接，用于在开关单元导通时产生一预定大小的电流；所述镜像电流源与所述电流产生单元连接，用于接入该电流产生单元产生的电流，并产生一镜像电流；所述多路输出单元与所述镜像电流源连接，用于接入该镜像电流并将所述镜像电流进行多路输出；上述电流平衡单元的数量与上述LED灯串的数量相同，多个电流平衡单元分别连接于多路输出单元与多个LED灯串之间，用于调整自身的电阻而维持各个LED灯串的电流平衡。
  12. 根据权利要求11所述的PWM调光电路，其特征在于，所述电流产生单元包括电阻（RSET）、运算放大器（OP1）以及MOS管（Q1）；所述电阻（RSET）一端与所述开关单元连接，另一端连接到该运算放大器（OP1）的反相输入端以及MOS管（Q1）的源极；所述运算放大器（OP1）的正相输入端接入一第一参考电压，输出端连接所述MOS管（Q1）的栅极；所述MOS管（Q1）的漏极连接至所述镜像电流源。
  13. 根据权利要求12所述的PWM调光电路，其特征在于，所述镜像电流源包括MOS管（Q2）以及MOS管（Q3）；所述MOS管（Q2）的漏极与所述MOS管（Q1）的漏极连接；所述MOS管（Q2）的源极以及栅极分别与MOS管（Q3）的源极以及栅极对接；所述MOS管（Q3）的漏极与所述多路输出单元连接；所述MOS管（Q2）的漏极与栅极通过导线相接。
  14. 根据权利要求13所述的PWM调光电路，其特征在于，所述多路输出单元包括运算放大器（OP2）、MOS管（Q4）以及多个MOS管（Q6）；所述运算放大器（OP2）的反相输入端以及MOS管（Q4）的漏极分别与所述MOS管（Q3）的漏极连接；所述运算放大器（OP2）的输出端与MOS管（Q4）和多个MOS管（Q6）的栅极连接；所述运算放大器（OP2）的正相输入端一第二参考电压；所述MOS管（Q4）的源极、多个MOS管（Q6）的源极分别连接至所述开关单元中MOS管（11）的源极；MOS管（Q6）的数量与电流平衡单元的数量相同，多个MOS管（Q6）的漏极分别连接多个电流平衡单元。
  15. 根据权利要求14所述的PWM调光电路，其特征在于，所述电流平衡单元包括MOS管（Q5）以及运算放大器（OP3）；所述运算放大器（OP3）的反相输入端以及MOS管（Q5）的源极分别与所述MOS管（Q6）的漏极连接，所述运算放大器（OP3）的输出端与MOS管（Q5）的栅极连接；所述运算放大器（OP3）的正相输入端接入一第二参考电压，所述MOS管（Q5）的漏极连接LED灯串。
  16. 根据权利要求15所述的PWM调光电路，其特征在于，所述MOS管（11）、（Q1）、（Q2）、（Q3）、（Q4）、（Q5）以及（Q6）都为N MOS。
  17. 根据权利要求14或15所述的PWM调光电路，其特征在于，所述第一参考电压为1.2V，所述第二参考电压为0.3V。
  18. 根据权利要求11所述的PWM调光电路，其特征在于，所述PWM调光电路为集成电路，所述MOS管（Q1）的源极为所述集成电路的复位端。
PCT/CN2011/080948 2011-07-15 2011-10-18 Pwm调光电路 Ceased WO2013010351A1 (zh)

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