基于NCP3065的大功率LED驱动电路的设计 毕业论文.doc

摘 要 LED（Light Emitting Diode）即发光二极管，是一种可以将电能转化为光能并具有二级管特性的电子器件。LED 具有节能、环保、结构牢固、使用寿命长、体积小、发光效率高、显色性高、工作电压低、功耗低等优点。LED照明现已成为具有发展前景和影响力的一项高新技术产品。但是原始电源有各种形式，无论哪种电源，一般都不能直接给LED供电因此，要用LED作为照明光源就要解决电源变换的问题。 本文内容是基于NCP3065的大功率LED驱动电路的设计，目的就是把常用电源转换成适合LED的电源。整个系统为纯硬件电路，包括开关电源部分和NCP3065芯片控制部分。开关电源为基于UC3842的单端激式开关电源，实现的是交流85V~265V /50HZ宽范围输入，输出电压24V最大电流5A。开关电源主要由四大部分组成：交流输入EMI防电磁干扰电源滤波器、二极管整流与电容滤波、DC/ DC 功率变换电路、 PWM控制电路。NCP3065控制部分将前级开关电源输出的稳定的直流电源信号经过输入取样电路的取样比较，然后加到升、降压斩波电路上，通过斩波电路将经过调节的电信号加到LED负载上，使LED正常发光。另外可以通过改变控制信号的占空比来控制NCP3065的工作与待机时间的比例，相对改变送到LED的平均功率，来调节LED的亮度。 本次设计的LED驱动电路具有比较高的可靠性，基本达到了设计要求。并且具有体积小、成本低、工作稳定，调试与维护都便的特点。 关键词：LED；NCP3065；开关电源；DC/DC变换电路 Abstract LED?(Light?Emitting?Diode),?light-emitting?diode,?is?a?kind?of?electronic?device?which?can?transform?electric?energy?into?light?energy?and?have?the?diode?characteristics.??LED?has?the?advantage?of?energy?saving,?environmental?protection,?firm?structure,?long?service?life,?small?volume,?high?luminous?efficiency,?high?color,?low?operating?voltage?and?low?power?consumption.?LED?lighting?has?become?a?high-tech?product?which?has?the?prospect?development?and?influence.?Although?the?original?power?has?a?variety?of?forms,?no?matter?what?kind?of?power,?are?generally?not?directly?to?the?LED?power?supply,?therefore,?the?use?LED?as?a?light?source?will?solve?the?problem. This?paper?is?the?design?of?high?power?NCP3065?drive?circuit?based?on?LED,?the?purpose?is?to?turn?the?usual?power?into?power?for?LED.?The?whole?system?is?pure?hardware?circuit,?which?divided?into?switching?power?supply?and?NCP3065?control?chip.?The?power?of?the?design?is?single-ended?forward?switching?power?supply?based?on?UC3842,.the?input?of?AC?will?reach?as?wide?as?85V~265V?/50HZ,the?output?of?voltage?is?24V?and?the?current??is?5A.?There?are?four?main?parts:?the?AC?input?EMI?electromagnetic?interference?power?filter,?a?diode?rectifier?with?capacitor?filter,?DC/?DC?power?converter?circuit,?PWM?control?circuit.?The?NCP3065?control?part?of?the?stable?DC