技术领域technical field
本发明属于半导体技术领域，具体涉及一种LED驱动电路。The invention belongs to the technical field of semiconductors, and in particular relates to an LED driving circuit.
背景技术Background technique
恒流源是一种常用的电子设备和装置，主要用于保护整个电路，即使出现电压不稳定或负载电阻变化很大的情况，都能确保供电电流的稳定，恒流源在电子线路中已广泛应用，如LED灯串的驱动等。传统的LED照明驱动一般由整流桥加一个(或多个)恒流芯片或恒流器件组成，恒流器件一般是一种类似JFET结型场效应晶体管结构的恒流器件，具有双向导通的特点，即在正向工作时可达到恒流的效果，在反向工作时类似于普通二极管的导通方式，具有较高的电流。工作时，AC交流电输入整流桥，再经过滤波电容滤波转换成直流电，然后串联恒流芯片或恒流器件(例如恒流二极管)，达到恒流输出的效果，从而驱动LED灯串。The constant current source is a commonly used electronic equipment and device, mainly used to protect the entire circuit, even if the voltage is unstable or the load resistance changes greatly, it can ensure the stability of the supply current. The constant current source has been used in electronic circuits. Widely used, such as the drive of LED light strings, etc. The traditional LED lighting driver is generally composed of a rectifier bridge plus one (or more) constant current chips or constant current devices. The constant current device is generally a constant current device with a structure similar to a JFET junction field effect transistor, with bidirectional conduction The characteristic is that it can achieve the effect of constant current when it works in the forward direction, and it is similar to the conduction mode of ordinary diodes when it works in the reverse direction, and has a higher current. When working, AC alternating current is input to the rectifier bridge, and then converted into direct current through filtering capacitors, and then connected in series with constant current chips or constant current devices (such as constant current diodes) to achieve the effect of constant current output, thereby driving LED light strings.
Yitao He等(A vertical current regulator diode with trench cathodebased on double epitaxial layers for LED lighting,Yitao He,PowerSemiconductor Devices&IC's(ISPSD)，2015 IEEE 27th International Symposium on,Page(s):157–160,10-14 May 2015)提出了一种LED照明驱动系统，如图1所示，该LED照明驱动系统包括整流滤波模块和恒流芯片两部分，整流滤波模块由整流桥和一个滤波电容构成，恒流芯片为任意二端恒流器件。该LED照明驱动系统包括整流和恒流两部分，结构较复杂，且该驱动系统容易产生瞬间高压浪涌，不具有大电流保护能力，容易使LED灯烧毁。Yitao He et al. (A vertical current regulator diode with trench cathode based on double epitaxial layers for LED lighting, Yitao He, Power Semiconductor Devices&IC's(ISPSD), 2015 IEEE 27th International Symposium on, Page(s):157–160,10-14 May 2015 ) proposed an LED lighting drive system, as shown in Figure 1, the LED lighting drive system includes two parts, a rectifier filter module and a constant current chip, the rectifier filter module is composed of a rectifier bridge and a filter capacitor, and the constant current chip is any two terminal constant current device. The LED lighting drive system includes two parts, rectification and constant current, with a relatively complex structure, and the drive system is prone to instantaneous high-voltage surges, does not have high-current protection capabilities, and easily burns out the LED lights.
发明内容Contents of the invention
本发明针对背景技术存在的缺陷，提出了一种LED驱动电路，增加可控硅调光模块和电压保护模块，将恒流和整流功能结合在一起，使得LED的驱动更简单可靠，可实现驱动系统的小型化，且进一步降低了成本。Aiming at the defects existing in the background technology, the present invention proposes an LED drive circuit, which adds a thyristor dimming module and a voltage protection module, and combines the constant current and rectification functions together to make the driving of the LED simpler and more reliable, and realize the driving The miniaturization of the system further reduces the cost.
本发明的技术方案如下：Technical scheme of the present invention is as follows:
一种LED驱动电路，包括可控硅调光模块、恒流整流模块、功率因素校正模块、滤波模块和电路保护模块，An LED drive circuit, comprising a thyristor dimming module, a constant current rectification module, a power factor correction module, a filter module and a circuit protection module,
所述恒流整流模块包括第一高反向耐压恒流器件D2、第二高反向耐压恒流器件D3、第一高压二极管D4和第二高压二极管D5，第一高压二极管D4和第二高压二极管D5的阳极互连并作为所述恒流整流模块的第一输出端，第一高压二极管D4的阴极接第一高反向耐压恒流器件D2的阳极并作为所述恒流整流模块的第一输入端，所述恒流整流模块的第一输入端前设置可控硅调光模块，第二高压二极管D5的阴极接第二高反向耐压恒流器件D3的阳极并作为所述恒流整流模块的第二输入端，第一高反向耐压恒流器件D2和第二高反向耐压恒流器件D3的阴极互连并作为所述恒流整流模块的第二输出端；The constant current rectification module includes a first high reverse withstand voltage constant current device D2, a second high reverse withstand voltage constant current device D3, a first high voltage diode D4 and a second high voltage diode D5, the first high voltage diode D4 and the second high voltage diode D4 The anodes of the two high-voltage diodes D5 are interconnected and serve as the first output terminal of the constant current rectification module, and the cathode of the first high-voltage diode D4 is connected to the anode of the first high reverse withstand voltage constant current device D2 and serves as the constant current rectification module. The first input terminal of the module, the first input terminal of the constant current rectification module is provided with a thyristor dimming module, and the cathode of the second high voltage diode D5 is connected to the anode of the second high reverse withstand voltage constant current device D3 and serves as The second input terminal of the constant current rectification module, the cathodes of the first high reverse withstand voltage constant current device D2 and the second high reverse withstand voltage constant current device D3 are interconnected and serve as the second input terminal of the constant current rectification module. output terminal;
所述功率因素校正模块包括第二电容C2、第三电容C3、第一二极管D6、第二二极管D7和第三二极管D8，第二电容C2一端连接第三二极管D8的阴极和所述恒流整流模块的第二直流输出端，另一端连接第一二极管D6的阴极和第二二极管D7的阳极，第三电容C3的一端连接第一二极管D6的阳极和所述恒流整流模块的第一直流输出端，另一端连接第二二极管D7的阴极和第三二极管D8的阳极；The power factor correction module includes a second capacitor C2, a third capacitor C3, a first diode D6, a second diode D7 and a third diode D8, and one end of the second capacitor C2 is connected to the third diode D8 The cathode and the second DC output terminal of the constant current rectification module, the other end is connected to the cathode of the first diode D6 and the anode of the second diode D7, and one end of the third capacitor C3 is connected to the first diode D6 The anode of the anode and the first DC output terminal of the constant current rectification module, and the other end is connected to the cathode of the second diode D7 and the anode of the third diode D8;
所述滤波模块包括接在所述恒流整流模块第一直流输出端和第二直流输出端之间并联的第四电容C4和第五电容C5；The filtering module includes a fourth capacitor C4 and a fifth capacitor C5 connected in parallel between the first DC output terminal and the second DC output terminal of the constant current rectification module;
所述电路保护模块包括高分子正温热敏电阻PPTC和压敏电阻Rv，高分子正温热敏电阻PPTC的一端接所述恒流整流模块的第二直流输出端，其另一端通过压敏电阻Rv后接所述恒流整流模块的第一直流输出端。The circuit protection module includes a polymer positive temperature thermistor PPTC and a piezoresistor Rv, one end of the polymer positive temperature thermistor PPTC is connected to the second DC output end of the constant current rectification module, and the other end is passed through the pressure sensitive The resistor Rv is followed by the first DC output terminal of the constant current rectification module.
具体的，所述可控硅调光模块包括调光电位器RW、电阻R1、第一电容C1、双向触发二极管D1和双向可控硅VS1，Specifically, the thyristor dimming module includes a dimming potentiometer RW, a resistor R1, a first capacitor C1, a triac D1 and a triac VS1,
调光电位器RW一端与双向可控硅VS1的第一阳极连接并作为所述可控硅调光模块的输入端，另一端通过电阻R1后连接电容C1的一端和双向触发二极管D1的一端，双向触发二极管D1的另一端连接双向可控硅VS1的控制端，电容C1的另一端连接双向可控硅VS1的第二阳极并作为所述可控硅调光模块的输出端连接所述恒流整流模块的第一输入端。One end of the dimming potentiometer RW is connected to the first anode of the triac VS1 and used as the input end of the thyristor dimming module, and the other end is connected to one end of the capacitor C1 and one end of the bidirectional trigger diode D1 after passing through the resistor R1, The other end of the triac D1 is connected to the control end of the triac VS1, the other end of the capacitor C1 is connected to the second anode of the triac VS1 and is used as the output end of the thyristor dimming module to connect to the constant current The first input end of the rectification module.
具体的，所述恒流整流模块的第一输入端和第二输入端为交流输入端。Specifically, the first input terminal and the second input terminal of the constant current rectification module are AC input terminals.
具体的，所述恒流整流模块的第一输入端和第二输入端为直流输入端。Specifically, the first input terminal and the second input terminal of the constant current rectification module are DC input terminals.
具体的，所述高反向耐压恒流器件的特点为：当正向电压大于夹断电压时，其电流保持恒定；当施加反向电压时，器件保持关断，且具有高的耐压。Specifically, the characteristics of the high reverse withstand voltage constant current device are: when the forward voltage is greater than the pinch-off voltage, its current remains constant; when the reverse voltage is applied, the device remains turned off and has a high withstand voltage .
具体的，所述第一高反向耐压恒流器件D2、第二高反向耐压恒流器件D3为相同结构的二端高反向耐压恒流器件。Specifically, the first high reverse withstand voltage constant current device D2 and the second high reverse withstand voltage constant current device D3 are two-terminal high reverse withstand voltage constant current devices with the same structure.
具体的，所述第一高反向耐压恒流器件D2、第二高反向耐压恒流器件D3为不同结构的二端高反向耐压恒流器件。Specifically, the first high reverse withstand voltage constant current device D2 and the second high reverse withstand voltage constant current device D3 are two-terminal high reverse withstand voltage constant current devices of different structures.
具体的，所述第一高压二极管D4和第二高压二极管D5为具有相同高反向耐压性能的二极管。Specifically, the first high-voltage diode D4 and the second high-voltage diode D5 are diodes with the same high reverse withstand voltage performance.
具体的，所述第一高压二极管D4和第二高压二极管D5为具有不同高反向耐压性能的二极管。Specifically, the first high voltage diode D4 and the second high voltage diode D5 are diodes with different high reverse withstand voltage properties.
LED灯串并联在所述恒流整流模块的第一输出的和第二输出端两端，直流电或交流电接在所述可控硅调光模块的输入端和所述恒流整流模块的第二输入端之间。The LED lights are connected in parallel between the first output terminal and the second output terminal of the constant current rectification module, and the direct current or alternating current is connected between the input terminal of the thyristor dimming module and the second output terminal of the constant current rectification module. between the input terminals.
高分子正温热敏电阻PPTC的特点为：当正常工作电流通过高分子正温热敏电阻PPTC时，高分子正温热敏电阻PPTC呈低阻状态；当电路中有异常过电流通过时，高分子正温热敏电阻PPTC呈高阻状态；当电路中过电流消失后，聚合物冷却，体积恢复正常，高分子正温热敏电阻PPTC又呈初始的低阻状态。The characteristics of the polymer positive temperature thermistor PPTC are: when the normal working current passes through the polymer positive temperature thermistor PPTC, the polymer positive temperature thermistor PPTC is in a low resistance state; when there is an abnormal overcurrent in the circuit, The polymer positive temperature thermistor PPTC is in a high-resistance state; when the overcurrent in the circuit disappears, the polymer cools down and the volume returns to normal, and the polymer positive temperature thermistor PPTC is in an initial low-resistance state again.
压敏电阻Rv的特点为：当有瞬态高压经过时，压敏电阻Rv呈低阻态有电流流过，当电压正常时压敏电阻Rv处于高阻态无电流流过。The characteristics of the varistor Rv are: when a transient high voltage passes by, the varistor Rv is in a low resistance state and current flows through it, and when the voltage is normal, the varistor Rv is in a high resistance state and no current flows through it.
本发明的有益效果为：本发明使用可控硅调光模块增加了调光功能，通过改变调光电位器RW阻值从而改变导通延时，改变导通角大小，使得流过LED的电流的占空比发生变化，从而影响LED的亮度，而且双向可控硅VS1易于使用，调光范围宽；由高反向耐压恒流器件和高压二极管组成的新型LED恒流驱动简化了传统LED照明驱动电路的结构，使整流功能和恒流功能结合到一起，无需加其它分立恒流器件即可直接外接市电来驱动LED灯串；使用高分子正温热敏电阻PPTC与压敏电阻Rv实现了过流保护与过压保护，在LED工作时起到了一定的保护作用。The beneficial effects of the present invention are: the present invention uses the thyristor dimming module to increase the dimming function, by changing the resistance value of the dimming potentiometer RW to change the conduction delay and the conduction angle, so that the current flowing through the LED The duty cycle of the LED changes, which affects the brightness of the LED, and the triac VS1 is easy to use and has a wide dimming range; the new LED constant current driver composed of a high reverse withstand voltage constant current device and a high voltage diode simplifies the traditional LED The structure of the lighting drive circuit combines the rectification function and the constant current function together, and the LED light string can be directly connected to the mains without adding other discrete constant current devices; the polymer positive temperature thermistor PPTC and the piezoresistor Rv are used Realize the over-current protection and over-voltage protection, and play a certain protective role when the LED is working.
附图说明Description of drawings
图1为背景技术提供的一种LED照明驱动系统的结构示意图；FIG. 1 is a schematic structural diagram of an LED lighting drive system provided in the background technology;
图2为本发明提供的LED恒流驱动的内部结构；Fig. 2 is the internal structure of the LED constant current drive provided by the present invention;
图3为本发明所述可控硅调光模块中双向可控硅VS1的电压输出波形图；3 is a voltage output waveform diagram of the triac VS1 in the thyristor dimming module of the present invention;
图4为本发明中的高反向耐压恒流器件的I-V特性曲线图；Fig. 4 is the I-V characteristic curve diagram of the high reverse withstand voltage constant current device in the present invention;
图5为本发明电路保护模块中过压保护原理图；Fig. 5 is a schematic diagram of overvoltage protection in the circuit protection module of the present invention;
图6为实施例中的一种高反向耐压恒流器件结构图。Fig. 6 is a structural diagram of a high reverse withstand voltage constant current device in the embodiment.
具体实施方式detailed description
下面结合具体实施例和附图对本发明进行详细说明。The present invention will be described in detail below in conjunction with specific embodiments and accompanying drawings.
如图2所示为本发明提出的LED驱动电路的具体示意图，包括可控硅调光模块Ⅰ、恒流整流模块Ⅱ、功率因素校正模块Ⅲ、滤波模块Ⅳ和电路保护模块Ⅴ。本实施例中可控硅调光模块Ⅰ的一种电路实现方式为，包括调光电位器RW、电阻R1、第一电容C1、双向触发二极管D1和双向可控硅VS1，调光电位器RW一端与双向可控硅VS1的第一阳极连接并作为所述可控硅调光模块的输入端，另一端通过电阻R1后连接电容C1的一端和双向触发二极管D1的一端，双向触发二极管D1的另一端连接双向可控硅VS1的控制端，电容C1的另一端连接双向可控硅VS1的第二阳极并作为所述可控硅调光模块的输出端连接所述恒流整流模块的第一输入端。Figure 2 is a specific schematic diagram of the LED drive circuit proposed by the present invention, including a silicon controlled rectifier module I, a constant current rectification module II, a power factor correction module III, a filter module IV and a circuit protection module V. A circuit implementation of the thyristor dimming module I in this embodiment is as follows: the dimming potentiometer RW, the resistor R1, the first capacitor C1, the triac D1 and the triac VS1, the dimming potentiometer RW One end is connected to the first anode of the bidirectional thyristor VS1 and serves as the input end of the thyristor dimming module, and the other end is connected to one end of the capacitor C1 and one end of the bidirectional trigger diode D1 after passing through the resistor R1, and the end of the bidirectional trigger diode D1 The other end is connected to the control end of the triac VS1, and the other end of the capacitor C1 is connected to the second anode of the triac VS1 and used as the output end of the thyristor dimming module to be connected to the first terminal of the constant current rectification module. input.
恒流整流模块包括第一高反向耐压恒流器件D2、第二高反向耐压恒流器件D3、第一高压二极管D4和第二高压二极管D5，第一高压二极管D4和第二高压二极管D5的阳极互连并作为所述恒流整流模块的第一输出端，第一高压二极管D4的阴极接第一高反向耐压恒流器件D2的阳极并作为所述恒流整流模块的第一输入端，所述恒流整流模块的第一输入端前设置可控硅调光模块，第二高压二极管D5的阴极接第二高反向耐压恒流器件D3的阳极并作为所述恒流整流模块的第二输入端，第一高反向耐压恒流器件D2和第二高反向耐压恒流器件D3的阴极互连并作为所述恒流整流模块的第二输出端。The constant current rectification module includes a first high reverse withstand voltage constant current device D2, a second high reverse withstand voltage constant current device D3, a first high voltage diode D4 and a second high voltage diode D5, the first high voltage diode D4 and the second high voltage The anodes of the diode D5 are interconnected and serve as the first output terminal of the constant current rectification module, and the cathode of the first high voltage diode D4 is connected to the anode of the first high reverse withstand voltage constant current device D2 and serves as the first output terminal of the constant current rectification module. The first input end, the first input end of the constant current rectification module is provided with a thyristor dimming module, and the cathode of the second high voltage diode D5 is connected to the anode of the second high reverse withstand voltage constant current device D3 and serves as the The second input end of the constant current rectification module, the cathodes of the first high reverse withstand voltage constant current device D2 and the second high reverse withstand voltage constant current device D3 are interconnected and serve as the second output end of the constant current rectification module .
进一步地，所述第一高反向耐压恒流器件D2和第二高反向耐压恒流器件D3的特点为：当正向电压大于夹断电压时，其电流保持恒定；当施加反向电压时，器件保持关断，且具有高的耐压。Further, the characteristics of the first high reverse withstand voltage constant current device D2 and the second high reverse withstand voltage constant current device D3 are: when the forward voltage is greater than the pinch-off voltage, the current remains constant; The device remains off when the voltage is applied and has a high withstand voltage.
进一步地，所述第一高反向耐压恒流器件D2、第二高反向耐压恒流器件D3为相同结构的二端高反向耐压恒流器件，也可以为不同结构的二端高反向耐压恒流器件。Further, the first high reverse withstand voltage constant current device D2 and the second high reverse withstand voltage constant current device D3 are two-terminal high reverse withstand voltage constant current devices with the same structure, or they can be two high reverse withstand voltage constant current devices with different structures. End high reverse withstand voltage constant current device.
进一步地，所述第一高压二极管D4和第二高压二极管D5为具有相同高反向耐压性能的二极管，也可以为具有不同高反向耐压性能的二极管。Further, the first high voltage diode D4 and the second high voltage diode D5 are diodes with the same high reverse withstand voltage performance, or they may be diodes with different high reverse withstand voltage performance.
进一步地，所述恒流整流模块的第一输入端和第二输入端可以为交流输入端，也可以为直流输入端。Further, the first input terminal and the second input terminal of the constant current rectification module may be AC input terminals or DC input terminals.
所述功率因素校正模块是由第二电容C2、第三电容C3、第一二极管D6、第二二极管D7和第三二极管D8组成的填谷式无源功率因素校正电路，第二电容C2一端连接第三二极管D8的阴极和所述恒流整流模块的第二直流输出端，另一端连接第一二极管D6的阴极和第二二极管D7的阳极，第三电容C3的一端连接第一二极管D6的阳极和所述恒流整流模块的第一直流输出端，另一端连接第二二极管D7的阴极和第三二极管D8的阳极；所述滤波模块包括接在所述恒流整流模块第一直流输出端和第二直流输出端之间并联的第四电容C4和第五电容C5。The power factor correction module is a valley-filling passive power factor correction circuit composed of the second capacitor C2, the third capacitor C3, the first diode D6, the second diode D7 and the third diode D8, One end of the second capacitor C2 is connected to the cathode of the third diode D8 and the second DC output end of the constant current rectification module, and the other end is connected to the cathode of the first diode D6 and the anode of the second diode D7. One end of the three capacitors C3 is connected to the anode of the first diode D6 and the first DC output end of the constant current rectification module, and the other end is connected to the cathode of the second diode D7 and the anode of the third diode D8; The filter module includes a fourth capacitor C4 and a fifth capacitor C5 connected in parallel between the first DC output terminal and the second DC output terminal of the constant current rectification module.
所述电路保护模块包括高分子正温热敏电阻PPTC和压敏电阻Rv，高分子正温热敏电阻PPTC的一端接所述恒流整流模块的第二直流输出端，其另一端通过压敏电阻Rv后接所述恒流整流模块的第一直流输出端。The circuit protection module includes a polymer positive temperature thermistor PPTC and a piezoresistor Rv, one end of the polymer positive temperature thermistor PPTC is connected to the second DC output end of the constant current rectification module, and the other end is passed through the pressure sensitive The resistor Rv is followed by the first DC output terminal of the constant current rectification module.
进一步地，所述高分子正温热敏电阻PPTC的特点为：当正常工作电流通过PPTC时，PPTC呈低阻状态；当电路中有异常过电流通过时，PPTC呈高阻状态；当电路中过电流消失后，聚合物冷却，体积恢复正常,PPTC又呈初始的低阻状态。Further, the characteristics of the polymer positive temperature thermistor PPTC are: when the normal operating current passes through the PPTC, the PPTC is in a low-resistance state; when an abnormal overcurrent passes through the circuit, the PPTC is in a high-resistance state; After the overcurrent disappears, the polymer cools down, the volume returns to normal, and PPTC assumes the initial low-resistance state again.
高分子正温热敏电阻PPTC作为过流保护防止了流过LED的电流过大，压敏电阻Rv作为过压保护保护了LED灯串不会因为瞬态高压而损坏。The polymer positive temperature thermistor PPTC acts as an overcurrent protection to prevent excessive current flowing through the LED, and the varistor Rv acts as an overvoltage protection to protect the LED light string from damage due to transient high voltage.
本实施例采用220V的交流市电，工作原理为：This embodiment adopts 220V AC mains, and the working principle is:
可控硅调光模块的输入端和恒流整流模块的第二输入端接市电220V交流电，信号通过可控硅调光模块时，经调光电位器RW、电阻R1等负载对第一电容C1进行充电，当第一电容C1两端电压达到双向触发二极管D1的导通电压时，双向触发二极管D1导通，双向可控硅VS1也导通。如图3所示，输出有一定的导通延时(delay)，此时输出信号为每半周期的前沿波形被切除的斩波。信号传输至恒流整流模块，经过整流桥的整流作用和高反向耐压恒流器件恒流作用得到恒定直流信号。同时功率因素校正模块大幅度增加了整流恒流模块中整流管的导通角，使功率因数提高。信号经过滤波模块，利用电容充放电原理得到平滑输出的直流电压，并使后级的LED灯串可靠稳定的工作。电路保护模块中，高分子正温热敏电阻PPTC提供了过流保护，压敏电阻Rv提供了过压保护。如图5所示，当在正常工作电压下，压敏电阻Rv呈高阻状态，当电压高于阈值电压时，压敏电阻Rv将体现它的钳位特性，电流急剧增大，使得电流几乎不从LED流过，把过高的电压拉低，从而达到过压保护。这些元件保证了LED不因电流、电压过大而损坏，能够稳定安全的工作。综上可知，在外加交流电时，LED灯串上流过的电流可保持一致，从而可以一直点亮LED灯串。LED灯串正常工作时，当灯串两端电压小于启动电压时，LED截止无电流通过，当两端电压大于启动电压，LED发光，并且通过的电流为一定值，所以电流波形为有一定占空比的矩形波。当调节调光模块中的调光电位器RW，即改变了接入电路的电位器阻值，从而改变了导通延时，改变了导通角大小，使得流过LED的电流的占空比发生变化，改变了平均输出电流的大小从而影响了LED的亮度，达到了调光的效果。The input terminalof thethyristor dimming module and the second input terminal of the constant current rectification module are connected to the mains 220V AC. A capacitorC1 is charged, and when the voltage across thefirst capacitorC1 reaches the conduction voltage of the bidirectional trigger diode D1, the bidirectional trigger diode D1 is turnedon , and the bidirectional thyristor VS1 is also turned on. As shown in Figure 3, the output has a certain turn-on delay (delay), and the output signal at this time is a chopping wave in which the leading edge waveform of each half cycle is cut off. The signal is transmitted to the constant current rectification module, and a constant DC signal is obtained through the rectification function of the rectifier bridge and the constant current function of the high reverse withstand voltage constant current device. At the same time, the power factor correction module greatly increases the conduction angle of the rectifier tube in the rectification constant current module, so that the power factor is improved. The signal passes through the filter module, and the smooth output DC voltage is obtained by using the principle of capacitor charging and discharging, so that the LED light string of the subsequent stage can work reliably and stably. In the circuit protection module, the polymer positive temperature thermistor PPTC provides overcurrent protection, and the varistor Rv provides overvoltage protection. As shown in Figure 5, when the varistor Rv is in a high-resistance state under normal operating voltage, when the voltage is higher than the threshold voltage, the varistor Rv will reflect its clamping characteristics, and the current increases sharply, making the current almost Do not flow through the LED, and pull down the excessive voltage to achieve overvoltage protection. These components ensure that the LED will not be damaged due to excessive current and voltage, and can work stably and safely. To sum up, it can be seen that when an alternating current is applied, the current flowing through the LED light string can be kept consistent, so that the LED light string can be always lit. When the LED light string is working normally, when the voltage at both ends of the light string is lower than the starting voltage, the LED will cut off and no current will pass through. Duct ratio of the rectangular wave. When the dimming potentiometer RW in the dimming module is adjusted, the resistance value of the potentiometer connected to the circuit is changed, thereby changing the conduction delay and the conduction angle, so that the duty of the current flowing through the LED The ratio changes, which changes the size of the average output current and thus affects the brightness of the LED, achieving the effect of dimming.
实施例Example
本实施例中，第一高压二极管D4和第二高压二极管D5为相同的具有高反向耐压的二极管，第一高反向耐压恒流器件D2和第二高反向耐压恒流器件D3为相同的高反向耐压恒流器件。所述高反向耐压恒流器件的结构示意图如图6所示，包括P型轻掺杂衬底2，位于P型轻掺杂衬底2之上的N型轻掺杂外延层3，位于N型轻掺杂外延层3之中的扩散P型阱区4，所述扩散P型阱区4为两个并位于两端，位于扩散P型阱区4之中的P型重掺杂区5和N型重掺杂区7，位于N型重掺杂区7和N型轻掺杂外延层3之间且嵌入扩散P型阱区4上表面的耗尽型沟道区6，位于N型轻掺杂外延层3和耗尽型沟道区6上表面的氧化层10，覆盖整个上表面的金属阴极9，位于P型轻掺杂衬底2下表面的金属阳极8，所述P型重掺杂区5、N型重掺杂区7和金属阴极9形成欧姆接触。In this embodiment, the first high voltage diode D4 and the second high voltage diode D5 are the same diodes with high reverse withstand voltage, the first high reverse withstand voltage constant current device D2 and the second high reverse withstand voltage constant current device D3 is the same high reverse withstand voltage constant current device. The structural diagram of the high reverse withstand voltage constant current device is shown in Figure 6, including a P-type lightly doped substrate 2, an N-type lightly doped epitaxial layer 3 located on the P-type lightly doped substrate 2, The diffused P-type well region 4 located in the N-type lightly doped epitaxial layer 3, the diffused P-type well region 4 is two and located at both ends, and the P-type heavily doped region located in the diffused P-type well region 4 The region 5 and the N-type heavily doped region 7 are located between the N-type heavily doped region 7 and the N-type lightly doped epitaxial layer 3 and the depletion channel region 6 embedded in the upper surface of the diffused P-type well region 4 is located The N-type lightly doped epitaxial layer 3 and the oxide layer 10 on the upper surface of the depletion channel region 6, the metal cathode 9 covering the entire upper surface, and the metal anode 8 located on the lower surface of the P-type lightly doped substrate 2, said The P-type heavily doped region 5, the N-type heavily doped region 7 and the metal cathode 9 form an ohmic contact.
本领域的普通技术人员可以根据本发明公开的这些技术启示做出各种不脱离本发明实质的其它各种具体变形和组合，这些变形和组合仍然在本发明的保护范围内。Those skilled in the art can make various other specific modifications and combinations based on the technical revelations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710311508.7ACN106973461A (en) | 2017-05-05 | 2017-05-05 | A kind of LED drive circuit |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710311508.7ACN106973461A (en) | 2017-05-05 | 2017-05-05 | A kind of LED drive circuit |
| Publication Number | Publication Date |
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| CN106973461Atrue CN106973461A (en) | 2017-07-21 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710311508.7APendingCN106973461A (en) | 2017-05-05 | 2017-05-05 | A kind of LED drive circuit |
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| CN (1) | CN106973461A (en) |
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