基于UC3842的开关稳压电源的设计
摘 要
随着电力电子技术的发展以及创新，使得开关电源这一项技术也在不断地发展与创新，由于这一成本反转点日益向低输出电力端的移动，为开关电源提供了广阔的发展空间。
电源设备用以实现电能变换和功率传递，是各种电子设备正常工作的基础，而高频高效小型开关电源又是开关电源发展的必然趋势，在通信、军事装备、交通设施、仪器仪表、工业设备、家用电器等领域得到了越来越多的广泛应用。
开关电源是利用现代电力电子技术，控制开关管开通和关断的时间比率，维持稳定输出电压的一种电源，开关电源一般由脉冲宽度调制（PWM）控制IC和MOSFET构成。开关电源和线性电源相比，二者的成本都随着输出功率的增加而增长，但二者增长速率各异。线性电源成本在某一输出功率点上，反而高于开关电源，这一点称为成本反转点。
设计论文主要是利用一种性能优良的电流控制型脉宽调制器UC3842。假如由于某种原因使输出电压升高时，脉宽调制器就会改变驱动信号的脉冲宽度，亦即占空比D，使斩波后的平均值电压下降，从而达到稳压目的，反之亦然。UC3842可以直接驱动MOS管、IGBT等，适合于制作20～80W小功率开关电源。
关键词：开关电源；UC3842；脉宽调制
Abstract
Along with the Power electronic technology development and innovation,it make that technology Switching power supply is always in the way of developing and innovating, whit the cost of inversion points increasingly to the low output power end mobile,make the Switch power supply provide a broad space for development.
Power equipment used to achieve the power conversion and power transmission，which is basic to the various electronic devices working normally,and the high frequency and high efficient small switching power supply is an inevitable development
trend,which
is
used
more
and
more
in
communications,militaryequipment,transportacilities,instrumentation,insustrial equipment,household appliances and other ares.
Switching power supply use the Modern electronic technology to control the turn-on and turn-off time ratio,maintain the stability of the output voltage of
Power
supply.Switching
power
supply
used
by
Pulse
width
modulation(PWM)Control IC and MOSFET. Switching power supply and Linear power comparison,they are cost's as the Output Power increases,But their growth is different.Linear power supply costs in Certain output power point,is higher than Switching power supply.This point is called Cost inversion point.
Design thesis is mainly using a kind of high performance current control Pulse width modulation UC3842.If some reasons make the output voltage rise,Pulse
width modulator can change the drive signal pulse width,the Duty ratio D,the chopper after the average voltage drop,to achieve the goal of stabilizing voltage,The reverse is also true.UC3842 Can directly drive MOSFET,IGBT and so on.Suitable for the production of 20～80W Small power switch power supply.
Key Words：Switching power supply，UC3842，Pulse width modulation
目 录
基于UC3842的开关稳压电源的设计 ................................................. I 摘 要 ........................................................................ I 目 录 ....................................................................... IV 插入图表 ....................................................................... VI 引 言 ...................................................................... VII 第1章 绪论 .................................................................... 1 1.1 课题背景与意义 ............................................................ 1 1.2 课题研究历程与现状 ........................................................ 1 1.3 本课题的研究容与目标 ...................................................... 4 第2章 开关电源的基本工作原理与电路结构 ........................................ 5 2.1 开关电源概述 .............................................................. 5 2.1.1 开关电源的工作原理 .................................................... 5 2.1.2 开关电源的组成 ........................................................ 7 2.1.3 开关电源的特点 ........................................................ 8 2.2 DC-DC变换电路拓扑概述 .................................................... 10 2.2.1 单端反激式电压变换器 ................................................. 10 2.2.2 推挽式电压变换器 ..................................................... 11 2.2.3 单端正激式电压变换器 ................................................. 11 2.2.4 半桥变换器 ........................................................... 12 2.2.5 全桥变换器 ........................................................... 13 第3章 高频变压器设计 ......................................................... 15 3.1 “黑箱”预先估计 ......................................................... 15 3.2 设计反激式变压器 ........................................................ 16 第4章 控制单元的选择 ......................................................... 19 4.1 UC3842的简介 ............................................................. 19 4.1.1 UC3842的封装形式 ..................................................... 19 4.1.2 UC3842部电路框图介绍 ................................................. 20 4.1.3 UC3842的工作原理 ..................................................... 21