WO2018090478A1 - 一种消除电流纹波的线性恒流led驱动电路以及led发光装置 - Google Patents

一种消除电流纹波的线性恒流led驱动电路以及led发光装置 Download PDF

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WO2018090478A1
WO2018090478A1 PCT/CN2017/070698 CN2017070698W WO2018090478A1 WO 2018090478 A1 WO2018090478 A1 WO 2018090478A1 CN 2017070698 W CN2017070698 W CN 2017070698W WO 2018090478 A1 WO2018090478 A1 WO 2018090478A1
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Prior art keywords
constant current
linear constant
branch
current
led
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PCT/CN2017/070698
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English (en)
French (fr)
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李照华
林道明
符传汇
王东旭
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深圳市明微电子股份有限公司
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Publication of WO2018090478A1 publication Critical patent/WO2018090478A1/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]
    • 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
    • H05B45/36—Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI]
    • 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
    • H05B45/395—Linear regulators
    • 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
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light 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 application relates to the field of LED driving, and in particular to a linear constant current LED driving circuit for eliminating current ripple and an LED lighting device.
  • LED As a new type of light source, LED is widely used in various fields due to its strong brightness, low energy consumption and long life. Since the LED has a fixed forward voltage, the LED string can only illuminate when the total forward voltage of the entire LED string is reached. In order to ensure that the LED string can work normally and stably, it needs constant current control.
  • the constant current control method of the traditional LED string is connected to the output of the rectifier bridge and the LED string by connecting a constant current control circuit. Between the inputs, as shown in Figure 1, or connected between the output of the LED string and ground, as shown in Figure 2.
  • the constant current source when the constant current source is used for constant current control of the LED light string, the LED light string can only emit light when the input voltage reaches its total forward voltage, so as shown in FIG. It shows that the current of the LED string will appear in the form of a square wave. The change of current will cause certain discomfort to the human eye, and will be caught by some photography settings, such as cameras.
  • the prior art is to parallel the capacitors at both ends of the LED string to refer to FIG. 4.
  • the current stored by the capacitor causes the current of the LED string to flow, thereby reducing the current ripple of the LED string.
  • the capacitor is charging and discharging in the voltage cycle of the city network, and the charge and discharge of the capacitor is non-linear, the LED string current will appear in the form of a triangular wave.
  • a better current strip elimination is achieved.
  • the wave effect in order to meet the LED lighting strobe requirements, requires the largest possible increase in the capacitance value, resulting in a larger volume and higher cost of the entire control system, and reduces the reliability of the system.
  • the technical problem to be solved by the present application is to provide a linear constant current LED driving circuit and an LED lighting device that eliminate current ripple for the above-mentioned drawbacks of the prior art.
  • the technical solution adopted by the present application to solve the technical problem is to construct a linear constant current LED driving circuit for eliminating current ripple, comprising a first branch and a second branch connected in parallel with each other, the first branch comprising a string Connected to the filter wave chip and the LED load, the second branch includes a first capacitor, and the whole of the first branch and the second branch are connected in parallel with the linear constant current control circuit and connected to the DC output of the rectifier bridge Between the ends.
  • the filter wave chip has a voltage terminal and a ground terminal
  • the chip includes: a first operational amplifier, a second operational amplifier, a first MOS transistor, and a second MOS transistor.
  • the source of the tube is connected to the ground via a DC source, and the drain is connected to another DC source.
  • the drain of the second MOS transistor is also connected to the non-inverting input of the first operational amplifier and to the ground via an integrating capacitor.
  • the linear constant current LED driving circuit further includes a thyristor bleeder circuit, and the thyristor bleeder circuit is connected between the DC output ends of the rectifier bridge.
  • the linear constant current LED driving circuit Also included is a unidirectional circuit having an input coupled to a DC positive output of the rectifier bridge or to a DC positive output of the rectifier bridge via the linear constant current control circuit, an output of the unidirectional circuit Connected to the first branch and the second branch in parallel.
  • the unidirectional circuit is a diode.
  • the present application also discloses an LED lighting device, including a thyristor dimming circuit, a rectifier bridge, and the linear constant current LED driving circuit, wherein the alternating current positive input end of the rectifier bridge is via the thyristor dimming circuit Connect to the mains line, the AC negative input of the rectifier bridge is connected to the mains zero line.
  • the linear constant current LED driving circuit and the LED lighting device for eliminating current ripple of the present application have the following beneficial effects: Compared with the conventional method of increasing the capacitance, the present application is connected to the LED load through a filter wave chip. Parallel to a first capacitor, this method drives the first capacitor without a large capacitance value, which can greatly reduce the capacitance value of the capacitor, and can achieve the purpose of eliminating the current ripple of the LED string, so that the LED string is two
  • the terminal current is kept constant, which occupies a small system area, increases the flexibility of the application of the system and improves the stability of the system.
  • 1 is a schematic structural view of a conventional linear constant current LED driving circuit
  • FIG. 2 is a schematic structural view of another conventional linear constant current LED driving circuit
  • Figure 3 is a waveform diagram of LED voltage and current in a conventional driving mode
  • FIG. 4 is a schematic structural view of a conventional linear constant current LED driving circuit for eliminating current ripple
  • FIG. 5 is a schematic structural view of a first embodiment of a linear constant current LED driving circuit of the present application.
  • FIG. 6 is a schematic diagram showing the internal circuit structure of the filter wave chip of FIG. 5;
  • FIG. 7 is a schematic structural view of a second embodiment of a linear constant current LED driving circuit of the present application.
  • FIG. 5 is a schematic structural view of a first embodiment of a linear constant current LED driving circuit of the present application.
  • the current-ripple eliminating linear constant current LED driving circuit of the present application comprises: a first branch and a second branch connected in parallel with each other, the first branch comprising a serially connected filter wave chip 20 and an LED load 10,
  • the two branches include a first capacitor C1, and the whole of the first branch and the second branch in parallel are connected in series with the linear constant current control circuit 30 between the DC output ends of the rectifier bridge 50.
  • the specific connection of the LED load 10 is not limited.
  • the LED load 10 is a plurality of LED lights connected in series. It can be understood that it can also be connected in parallel or in series and parallel.
  • the LED load 10 may also be a parallel connection of a plurality of light groups, and the number of LEDs of each light group may be the same or different, and may also be other irregular arrangement combinations, etc., which are all within the protection scope of the present application.
  • the present application is connected in series with the LED load 10 through a filter wave chip 20, and then connected in parallel with a first capacitor C1.
  • the first capacitor C1 is driven without a large capacity.
  • the value can greatly reduce the capacitance value of the capacitor, which can achieve the purpose of eliminating the current ripple of the LED string, keeping the current at both ends of the LED string constant, occupying a small system area, and increasing the flexibility of the application of the system. And improve the stability of the system.
  • FIG. 6 is a schematic diagram showing the internal circuit structure of the filter wave chip of FIG. 5.
  • the filter wave chip 20 has a voltage terminal Drain and a ground terminal GND, and the chip includes: a first operational amplifier Amp1, a second operational amplifier Amp2, a MOS transistor Q1, a MOS transistor Q2, a first resistor R1, and an integrating capacitor.
  • C2 the drain of the MOS transistor Q1 is connected to the voltage terminal Drain, The source is connected to the out-of-phase input terminal of the first operational amplifier Amp1 and the ground terminal GND via the first resistor R1, the gate is connected to the output terminal of the first operational amplifier Amp1, and the non-inverting input terminal of the second operational amplifier Amp2 is connected.
  • the non-inverting input terminal is for receiving the reference voltage Vref
  • the output terminal is connected to the gate of the MOS transistor Q2
  • the source of the MOS transistor Q2 is connected to the grounding terminal GND via a DC source
  • the drain is connected to another DC.
  • the drain of the MOS transistor Q2 is also connected to the non-inverting input terminal of the first operational amplifier Amp1 and to the ground GND via the integrating capacitor C2.
  • MOS transistor Q1 and the MOS transistor Q2 are both P-channel MOS transistors.
  • the filter wave chip 20 detects the LED string current through the drain voltage of the MOS transistor Q1, performs feedback control through the second operational amplifier Amp2, adjusts the gate voltage of the MOS transistor Q1, and finally keeps the source voltage of the MOS transistor Q1 constant, specific When the drain terminal voltage is greater than a set value, the gate voltage of the MOS transistor Q1 is slowly raised. When the drain terminal voltage is less than a set value, the gate voltage of the MOS transistor Q1 is slowly lowered, and finally the conduction of the MOS transistor Q1 is changed. State to achieve the goal of constant current.
  • the linear constant current LED driving circuit further includes a thyristor bleeder circuit 40 connected between the DC output ends of the rectifier bridge 50.
  • linear constant current control circuit 30 and the thyristor bleeder circuit 40 are prior art, and are not described herein again.
  • the linear constant current LED driving circuit further includes a unidirectional circuit to prevent current from flowing to the rectifier bridge 50 when the first capacitor C1 is discharged, and the input end of the unidirectional circuit is connected to the DC positive output terminal of the rectifier bridge 50 or Connected to the DC positive output of the rectifier bridge 50 via the linear constant current control circuit 30, the output of the unidirectional circuit is coupled to the first and second branches in parallel.
  • the unidirectional circuit can be a diode D1.
  • the anode of the diode D1 is directly connected to the DC positive output terminal of the rectifier bridge 50, and the cathode of the diode D1 is connected to the input end of the LED string and the discharge end of the first capacitor C1.
  • FIG. 7 is a schematic structural view of a second embodiment of the linear constant current LED driving circuit of the present application.
  • the linear constant current control circuit 30 is located between the DC positive output terminal of the rectifier bridge 50 and the anode of the diode D1. After the first branch and the second branch are connected in parallel, they are directly grounded, that is, the DC negative output end of the rectifier bridge 50.
  • the linear constant current control circuit 30 When the grid voltage is greater than the sum of the forward voltage of the LED string and the voltage across the filter chip 20, the linear constant current control circuit 30 is turned on by the set fixed current, which flows through the LED string and the filter. The sum of the currents of the ripple chip 20 and the inflow capacitor; when the market voltage is less than the sum of the forward voltage of the LED string and the voltage across the filter chip 20, the linear constant current control circuit 30 is turned off, the first capacitor The amount of electricity on C1 is vented through the LED string and the filter wave chip 20.
  • the LED string current passes through the filter wave chip 20, and the filter wave chip 20 detects the average current of the LED string through the drain terminal voltage of the MOS transistor Q1. After several cycles of detection, the filter wave chip The gate voltage of the 20MOS transistor Q1 is kept constant, and the current flowing through the filter ripple chip 20 is kept constant, that is, the current flowing through the LED string remains constant.
  • the LED light string flows a constant current, and the excess current is charged by the first capacitor C1, the voltage of the first capacitor C1 increases, and the voltage of the drain terminal of the MOS transistor Q1 follows The capacitance increases and increases, and the amplitude remains the same.
  • the LED when the voltage of the commercial network is greater than the sum of the forward voltage of the LED string and the voltage across the filter chip 20, the LED is turned on with a constant current;
  • the first capacitor C1 When the light string is conducting voltage and the sum of the voltages across the filter chip 20, the first capacitor C1 is discharged through the LED string, the LED lamp string flows through a constant current, and the voltage of the first capacitor C1 decreases linearly, and the MOS transistor Q1 leaks.
  • the voltage decreases as the voltage of the first capacitor C1 decreases, and the amplitude remains the same, so that the LED current remains constant throughout the market voltage period.
  • the input is AC 120V/60Hz
  • the 120V LED string is connected in series
  • the capacitance of the first capacitor C1 is 10uF.
  • the current of the linear constant current control circuit 30 chip
  • the detection voltage of the drain terminal of the 20MOS transistor Q1 is 3V
  • the time ratio of charging and discharging the integrated capacitor C2 is 9:1
  • the MOS transistor Q1 The gate voltage is constant.
  • the peak value of the AC voltage is 170V.
  • the linear constant current control chip When the voltage is greater than 120V of the forward voltage of the string, the linear constant current control chip is turned on, and the conduction phase angle is So the average current is
  • the filter chip 20MOS drain terminal voltage is greater than 0.5V, the filter wave chip 20 can maintain a constant current of 50 mA.
  • the filter chip 20MOS drain terminal voltage is less than 3V time:
  • the minimum voltage of the MOS drain terminal of the filter wave chip 20 is: It is larger than the minimum voltage at which MOS transistor Q1 maintains a constant current, so the LED string can maintain a constant current of 50 mA during the grid period.
  • Another object of the present application is to protect an LED lighting device, including a thyristor dimming circuit 60, a rectifier bridge 50, and the linear constant current LED driving circuit, wherein the AC positive input terminal of the rectifier bridge 50 passes through
  • the thyristor dimming circuit 60 is connected to the mains hot line, and the AC negative input end of the rectifier bridge 50 is connected to the mains zero line.
  • the linear constant current LED driving circuit and the LED lighting device for eliminating current ripple of the present application have the following beneficial effects: Compared with the conventional method of increasing the capacitance, the present application passes a filter wave chip and an LED. After the load is connected in series, it is connected in parallel with a first capacitor. In this way, the first capacitor does not need a large capacitance value, and the capacitance value of the capacitor can be greatly reduced, thereby achieving the purpose of eliminating the current ripple of the LED string. Keep the current across the LED string constant and occupy a smaller system Area, increase the flexibility of the application of the system and improve the stability of the system.

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  • Electromagnetism (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

一种消除电流纹波的线性恒流LED驱动电路以及LED发光装置，包括相互并联的第一支路和第二支路，所述第一支路包括串接的滤纹波芯片(20)和LED负载(10)，第二支路包括第一电容(C1)，所述第一支路和第二支路并联后的整体与线性恒流控制电路(30)串接于整流桥(50)的直流输出端之间；相对传统的通过加大电容的方法，一个滤纹波芯片(20)与LED负载(10)串接后再与一个第一电容(C1)并联，这种方式驱动下第一电容(C1)不需要较大的容值，可大大减小电容的容值，既可以达到消除LED灯串电流纹波的目的，使LED灯串两端电流保持恒定，又占用了较小的系统面积，增加系统的应用的灵活性和提高系统的稳定性。

Description

一种消除电流纹波的线性恒流LED驱动电路以及LED发光装置 技术领域
本申请涉及LED驱动领域，尤其涉及一种消除电流纹波的线性恒流LED驱动电路以及LED发光装置。
背景技术
LED作为一种新型光源，因其具备亮度强、能耗低且寿命长的优点而被广泛应用于各个领域。由于LED具有固定的正向导通电压，只有达到整个LED灯串的总的正向导通电压时，LED灯串才能发光。为了保证LED灯串能够正常稳定地工作，需要对其进行恒流控制，而传统的LED灯串的恒流控制方法就是通过将一个恒流控制电路连接于整流桥的输出端与LED灯串的输入端之间，如图1所示；或者连接于LED灯串的输出端与地之间，如图2所示。而在市电供电条件下，采用上述恒流源对LED灯串进行恒流控制时，LED灯串只能在输入电压达到其总的正向导通电压时才会发光，因此，如图3所示，LED灯串的电流会以方波的形式出现，电流的变化会对人眼造成一定的不适，并会被一些摄影设置捕抓到，比如相机等。
为解决上述LED灯串电流问题，现有技术是在LED灯串两端并联一下电容参考图4。在电网电压小于LED灯串正向导通电压时，通过电容存储的电量使LED灯串的电流流过，以此来达到减小LED灯串电流纹波。由于在市网电压周期内，电容在充放电，并且电容充放电的非线性，LED灯串电流会以三角波的形式出现，为了尽可能的消除三角波电流，达到较好的消除电流纹 波效果，以符合LED照明频闪要求，需要尽可能大的加大电容值，从而造成整个控制系统体积较大和成本较高，并降低了系统的可靠性。
发明内容
本申请要解决的技术问题在于，针对现有技术的上述缺陷，提供一种消除电流纹波的线性恒流LED驱动电路以及LED发光装置。
本申请解决其技术问题所采用的技术方案是：构造一种消除电流纹波的线性恒流LED驱动电路，包括相互并联的第一支路和第二支路，所述第一支路包括串接的滤纹波芯片和LED负载，第二支路包括第一电容，所述第一支路和第二支路并联后的整体与所述线性恒流控制电路串接于整流桥的直流输出端之间。
在本申请所述的线性恒流LED驱动电路中，所述滤纹波芯片具有电压端和接地端，芯片内部包括：第一运算放大器、第二运算放大器、第一MOS管、第二MOS管、第一电阻、积分电容，所述第一MOS管的漏极连接所述电压端、源极连接第一运算放大器的异相输入端以及经由所述第一电阻连接接地端、栅极连接至第一运算放大器的输出端，第二运算放大器的异相输入端连接至所述电压端、同相输入端用于接收参考电压、输出端连接至第二MOS管的栅极，所述第二MOS管的源极经由直流源连接接地端、漏接连接另一直流源，所述第二MOS管的漏极还连接第一运算放大器的同相输入端以及经由积分电容连接至接地端。
在本申请所述的线性恒流LED驱动电路中，所述线性恒流LED驱动电路还包括可控硅泄放电路，可控硅泄放电路连接于整流桥的直流输出端之间。
在本申请所述的线性恒流LED驱动电路中，所述线性恒流LED驱动电路 还包括单向电路，所述单向电路的输入端连接至整流桥的直流正输出端或者经由所述线性恒流控制电路连接至整流桥的直流正输出端，所述单向电路的输出端与并联的第一支路和第二支路连接。
在本申请所述的线性恒流LED驱动电路中，所述单向电路为一二极管。
本申请还公开了一种LED发光装置，包括可控硅调光电路、整流桥以及所述的线性恒流LED驱动电路，所述整流桥的交流正输入端经由所述可控硅调光电路连接市电火线，所述整流桥的交流负输入端连接市电零线。
实施本申请的消除电流纹波的线性恒流LED驱动电路以及LED发光装置，具有以下有益效果：相对传统的通过加大电容的方法，本申请通过一个滤纹波芯片与LED负载串接后再与一个第一电容并联，这种方式驱动下第一电容不需要较大的容值，可大大减小电容的容值，既可以达到消除LED灯串电流纹波的目的，使LED灯串两端电流保持恒定，又占用了较小的系统面积，增加系统的应用的灵活性和提高系统的稳定性。
附图说明
下面将结合附图及实施例对本申请作进一步说明，附图中：
图1是一种传统线性恒流LED驱动电路的结构示意图；
图2是另一种传统线性恒流LED驱动电路的结构示意图；
图3是传统驱动方式下LED电压和电流波形图；
图4是传统的消除电流纹波的线性恒流LED驱动电路的结构示意图；
图5是本申请的线性恒流LED驱动电路的第一实施例的结构示意图；
图6是图5中的滤纹波芯片的内部电路结构示意图；
图7是本申请的线性恒流LED驱动电路的第二实施例的结构示意图。
具体实施方式
为了对本申请的技术特征、目的和效果有更加清楚的理解，现对照附图详细说明本申请的具体实施方式。
参考图5是本申请的线性恒流LED驱动电路的第一实施例的结构示意图。
本申请的消除电流纹波的线性恒流LED驱动电路包括：相互并联的第一支路和第二支路，所述第一支路包括串接的滤纹波芯片20和LED负载10，第二支路包括第一电容C1，所述第一支路和第二支路并联后的整体与所述线性恒流控制电路30串接于整流桥50的直流输出端之间。
需要明确的是，LED负载10的具体连接并不做限制。本实施例中，LED负载10为多个LED灯串联。可以理解的是，还可以并联或者是串并联结合。例如，LED负载10还可以是多个灯组的并联，每个灯组的LED数量可以相同或者不同，还可以是其他不规则的排列组合等，这些都在本申请的保护范围之内。
相对传统的通过加大电容的方法，本申请通过一个滤纹波芯片20与LED负载10串接后再与一个第一电容C1并联，这种方式驱动下第一电容C1不需要较大的容值，可大大减小电容的容值，既可以达到消除LED灯串电流纹波的目的，使LED灯串两端电流保持恒定，又占用了较小的系统面积，增加系统的应用的灵活性和提高系统的稳定性。
参考图6是图5中的滤纹波芯片的内部电路结构示意图。
具体的，所述滤纹波芯片20具有电压端Drain和接地端GND，芯片内部包括：第一运算放大器Amp1、第二运算放大器Amp2、MOS管Q1、MOS管Q2、第一电阻R1、积分电容C2，所述MOS管Q1的漏极连接所述电压端Drain、 源极连接第一运算放大器Amp1的异相输入端以及经由所述第一电阻R1连接接地端GND、栅极连接至第一运算放大器Amp1的输出端，第二运算放大器Amp2的异相输入端连接至所述电压端Drain、同相输入端用于接收参考电压Vref、输出端连接至MOS管Q2的栅极，所述MOS管Q2的源极经由直流源连接接地端GND、漏接连接另一直流源，所述MOS管Q2的漏极还连接第一运算放大器Amp1的同相输入端以及经由积分电容C2连接至接地端GND。
具体的，MOS管Q1、MOS管Q2均为P沟道的MOS管。
滤纹波芯片20通过MOS管Q1漏端电压来检测LED灯串电流，通过第二运算放大器Amp2进行反馈控制，调整MOS管Q1栅极电压，最终使MOS管Q1源极电压保持恒定，具体的，当漏端电压大于一设定值时，缓慢抬高MOS管Q1栅端电压，当漏端电压小于一设定值时，缓慢降低MOS管Q1栅极电压，最终改变MOS管Q1的导通状态以达到恒流的目的。
优选的，所述线性恒流LED驱动电路还包括可控硅泄放电路40，可控硅泄放电路40连接于整流桥50的直流输出端之间。
其中，线性恒流控制电路30以及可控硅泄放电路40的实现和具体原理为现有技术，此处不再赘述。
优选的，所述线性恒流LED驱动电路还包括单向电路，以防止第一电容C1放电时电流流向整流桥50，所述单向电路的输入端连接至整流桥50的直流正输出端或者经由所述线性恒流控制电路30连接至整流桥50的直流正输出端，所述单向电路的输出端与并联的第一支路和第二支路连接。
具体的，所述单向电路可以为一二极管D1。
第一实施例中，二极管D1的正极直接连接整流桥50的直流正输出端，二极管D1的负极连接LED灯串的输入端和第一电容C1的放电端。
参考图7是本申请的线性恒流LED驱动电路的第二实施例的结构示意图。
第二实施例与第一实施例的唯一不同在于线性恒流控制电路30的位置，第二实施例中，线性恒流控制电路30位于整流桥50的直流正输出端和二极管D1的正极之间，第一支路和第二支路并联后是直接接地，即整流桥50的直流负输出端。
本申请的工作原理如下：
当市网电压大于LED灯串正向导通电压和滤纹波芯片20两端电压之和时，线性恒流控制电路30以设置好的固定电流导通，该电流为流过LED灯串及滤纹波芯片20和流进电容的电流总和；当市网电压小于LED灯串灯串正向导通电压和滤纹波芯片20两端电压之和时，线性恒流控制电路30关闭，第一电容C1上的电量通过LED灯串和滤纹波芯片20泄放。
在市网周期内，LED灯串电流都通过滤纹波芯片20，滤纹波芯片20通过MOS管Q1漏端电压检测LED灯串的平均电流，经过几个周期的检测后，滤纹波芯片20MOS管Q1的栅极电压保持恒定，流过滤纹波芯片20的电流保持恒定，也即流过LED灯串的电流保持恒定。
具体的，当市网电压大于LED灯串正向导通电压时，LED灯串流过恒定电流，多余电流通过给第一电容C1充电，第一电容C1电压增加，MOS管Q1漏端电压随着电容电压增加而增加，并且幅度保持一致，所以，在市网电压大于LED灯串正向导通电压和滤纹波芯片20两端电压之和时，LED以恒定电流导通；在市网电压小于灯串正向导通电压和滤纹波芯片20两端电压之和时，第一电容C1通过LED灯串放电，LED灯串流过恒定电流，第一电容C1电压线性下降，MOS管Q1漏端电压随着第一电容C1电压减少而减小，并且幅度保持一致，从而，在整个市网电压周期内，LED电流保持恒定。
为了便于理解本申请的效果，下面举例说明。
以图5的第一实施例为例，输入为交流120V/60Hz，串接120V LED灯串，第一电容C1的容值为10uF。假设线性恒流控制电路30(芯片)开启时电流为100mA，滤纹波芯片20MOS管Q1漏端检测电压为3V，当给积分电容C2充电和放电的时间比为9：1时，MOS管Q1栅极电压达到恒定。交流电压峰值为170V，当电压大于灯串正向导通电压120V时，线性恒流控制芯片开启，导通相角为
Figure PCTCN2017070698-appb-000001
所以平均电流为
Figure PCTCN2017070698-appb-000002
当滤纹波芯片20MOS漏端电压大于0.5V时，滤纹波芯片20可以保持50mA恒定电流。滤纹波芯片20MOS漏端电压小于3V时间为：
Figure PCTCN2017070698-appb-000003
滤纹波芯片20的MOS漏端最小电压为:
Figure PCTCN2017070698-appb-000004
大于MOS管Q1保持恒流的最小电压，所以在电网周期内，LED灯串可以保持50mA恒流。
本申请的另一目的，是保护一种LED发光装置，包括可控硅调光电路60、整流桥50以及所述的线性恒流LED驱动电路，所述整流桥50的交流正输入端经由所述可控硅调光电路60连接市电火线，所述整流桥50的交流负输入端连接市电零线。
综上所述，实施本申请的消除电流纹波的线性恒流LED驱动电路以及LED发光装置，具有以下有益效果：相对传统的通过加大电容的方法，本申请通过一个滤纹波芯片与LED负载串接后再与一个第一电容并联，这种方式驱动下第一电容不需要较大的容值，可大大减小电容的容值，既可以达到消除LED灯串电流纹波的目的，使LED灯串两端电流保持恒定，又占用了较小的系统 面积，增加系统的应用的灵活性和提高系统的稳定性。
上面结合附图对本申请的实施例进行了描述，但是本申请并不局限于上述的具体实施方式，上述的具体实施方式仅仅是示意性的，而不是限制性的，本领域的普通技术人员在本申请的启示下，在不脱离本申请宗旨和权利要求所保护的范围情况下，还可做出很多形式，这些均属于本申请的保护之内。

Claims (6)

  1. 一种消除电流纹波的线性恒流LED驱动电路，其特征在于，包括相互并联的第一支路和第二支路，所述第一支路包括串接的滤纹波芯片和LED负载，第二支路包括第一电容，所述第一支路和第二支路并联后的整体与所述线性恒流控制电路串接于整流桥的直流输出端之间。
  2. 根据权利要求1所述的线性恒流LED驱动电路，其特征在于，所述滤纹波芯片具有电压端和接地端，所述滤纹波芯片具有芯片内包括：第一运算放大器、第二运算放大器、第一MOS管、第二MOS管、第一电阻、积分电容，所述第一MOS管的漏极连接所述电压端、源极连接第一运算放大器的异相输入端以及经由所述第一电阻连接接地端、栅极连接至第一运算放大器的输出端，第二运算放大器的异相输入端连接至所述电压端、同相输入端用于接收参考电压、输出端连接至第二MOS管的栅极，所述第二MOS管的源极经由直流源连接接地端、漏接连接另一直流源，所述第二MOS管的漏极还连接第一运算放大器的同相输入端以及经由积分电容连接至接地端。
  3. 根据权利要求1所述的线性恒流LED驱动电路，其特征在于，所述线性恒流LED驱动电路还包括可控硅泄放电路，可控硅泄放电路连接于整流桥的直流输出端之间。
  4. 根据权利要求1所述的线性恒流LED驱动电路，其特征在于，所述线性恒流LED驱动电路还包括单向电路，所述单向电路的输入端连接至整流桥的直流正输出端或者经由所述线性恒流控制电路连接至整流桥的直流正输出端，所述单向电路的输出端与并联的第一支路和第二支路连接。
  5. 根据权利要求4所述的线性恒流LED驱动电路，其特征在于，所述 单向电路为一二极管。
  6. 一种LED发光装置，其特征在于，包括可控硅调光电路、整流桥以及如权利要求1-5任一项所述的线性恒流LED驱动电路，所述整流桥的交流正输入端经由所述可控硅调光电路连接市电火线，所述整流桥的交流负输入端连接市电零线。
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