基于SG3525设计单相正弦波SPWM逆变电源

基于SG3525控制的车载逆变电源设计与实现
 引言
 随着电子信息产业高速发展，逆变电源被广泛应用于很多领域，一个可靠、优质的逆变电源可以保证系统可靠安全运行，所以，逆变电源是一个重要的
研究领域。

方波逆变是一种较简单的变换方式，它适用于各种整流负载，不
仅技术要求低，而且设计电路比较简单。

本文依据方波逆变电源的基本原理，模块化设计了逆变电源的实现电路，包括基于SG3525控制的高频PWM主
电路、全桥逆变电路、必要的保护电路和相关驱动电路，并给出实验结果及
分析。

 1、原理与设计
1.1、逆变电源基本原理
 逆变电源采用典型的两级变换：第1级是DC/DC升压变换器，第2级是DC/AC逆变器。

DC/DC升压变换由SG3525芯片产生的PWM波将12V直流逆变为高频方波，经高频变压器升压后，变压器副边可获得峰值为155V的
高频方波，再经过全波整流获得一个稳定的310V直流电压；DC/AC变换以
方波逆变方式，将稳定的直流电压逆变成310V的工频方波电压，该电压有
效值约为220V，频率为50Hz，可驱动负载［1］。

为保证系统正常运行，需。

湖南工程学院课程设计课程名称电力电子技术课题名称 SG3525正弦波逆变电源设计专业班级学号姓名指导教师2013年12 月16 日湖南工程学院课程设计任务书课程名称单片机原理及应用课题智能密码锁设计专业班级学生姓名学号指导老师审批任务书下达日期2013 年12 月16 日设计完成日期2013 年12 月27 日目录第1章概述 (1)1.1课题来源 (1)1.2解决方法 (1)1.3设计的优点 (2)第2章系统总体设计 (2)2.1 系统设计总体思路 (2)2.1 系统基本工作原理 (3)2.3 系统设计框图 (4)第3章系统主电路设计 (5)3.1 系统主电路结构设计 (5)3.2 系统保护电路设计 (5)第4章单元电路设计 (6)4.1 正弦信号发生电路设计 (6)4.2 宽度调制PWM电路设计 (7)4.3 电压电流检测电路设计 (11)4.4 光耦合驱动电路设计 (12)第6章总结与体会 (13)附录1总电路图 (14)附录2 参考文献 (15)附录3 课程设计成绩评分表 (16)第1章概述1.1课题来源电力逆变电源有着广泛的用途，它可用于各类交通工具，在太阳能及风能发电领域，逆变器有着不可替代的作用。

电力控制系统的可靠程度是电力系统和设备可靠、高效运行的保证，而电力控制系统必须具备安全可靠的控制电源。

电力系统中为保证变电所的诸如后台机、通讯设备等能在交流电源停电后不间断工作，工程做法一般采用UPS电源作为主要解决方案，但UPS电源存在容量小、价格贵、故障率高等不足，因此综合自动化变电所中可采用电力正弦波逆变电源来代替常规不间断UPS电源。

1.2解决方法逆变电源是一种采用电力电子技术进行电能变换的装置，它从交流或直流输入获得稳压恒频的交流输出。

利用逆变电源可以解决UPS电源存在的各种缺点，可以很好的运用在一些不能断电的场合。

本相正弦波SPWM逆变电源的设计以SG3252为核心，采用了运算放大器、二极管、功率场效应管、电容和电阻等器件来组成电路。

2019.08科学技术创新-7-基于SG3525的全桥逆变SWPM控制波形电路周勤玲(中山职业技术学院，广东中山528400)摘要:本文介绍了基于SG3525的全桥逆变SWPM控制波形电路，包括正弦波发生电路、整流电路、SWPM脉冲产生电路、延时死区调整电路。

该电路简单、易于实现，为正弦波逆变器SWPM电路设计提供一种借鉴'关键词:逆变;正弦波;全桥;SPWM中图分类号:TP274.2文献标识码：A文章编号:2096-4390(2019)08-0007-02随着电力电子技术的发展，正弦波逆变器得到了广泛的应用。

正弦波(SWPM)技术是正弦波逆变的关键技术问题。

逆变电源SWPM脉冲产生的方法有很多，如模拟电路、数字电路、数模结合电路等等。

目前，市场上主要是模拟控制和单片机控制。

用运算放大器组成的模拟SPWM电路复杂。

用单片机编程实现的方法,CPU被占用了大量资源,运行效率低。

模数混合控制的电路，可靠性和稳定性差叫本文基于SG3525集成芯片设计了一种简单、稳定的SWPM脉冲产生电路。

1主电路结构全桥逆变器主电路拓扑如图1所示。

其基本原理为:当两只对角功率管Q1、Q4或Q2、Q3同时导通时，功率从直流电源侧通过变压器向负载传输。

同一桥上、下功率管的驱动信号互补,并有一定的死区时间。

逆变桥的功率管QI、Q3由SPWM信号驱动,Q2、Q4由方波驱动。

逆变桥图4全桥逆变器主电路拓扑2开关管驱动控制信号的调制策略目前，电压型单相全桥逆变器有三种基本的SPWM技术，即双极性SPWM、单极性SPWM、倍频式SPWMo双极性SPWM的总开关频率比单极性高几乎一倍，所以开关损耗、总的谐波畸变率也大一倍。

单极性SPWM与倍频式SPWM谐波畸变率相近。

本文采用单极性SPWM调制技术，如图2所示，桥臂Q1和Q3在高频互补SPWM信号驱动下导通，桥臂Q2和Q4由方波(与基准正弦波同频同步)驱动导通,在全桥输出端AB形成了SPWM波形。

无工频变压器的逆变电源设计【摘要】：本文介绍以SG3525芯片为逆变电源控制系统，设计无工频变压器SPWM调制方式正弦波输出电源，以期实现逆变电源稳定输出。

【关键词】：无工频变压器；电路；电源一、正弦波逆变器的设计要求和主电路形式及参数1.1逆变电源的设计要求和目标1）输出电压：输出为单相220V AC（有效值），频率为50Hz±1Hz。

2）输出功率：4KW，允许过载20%，既Pomax=4800W。

3）输出电流：允许失真度为3倍，既在电压峰值时的电流峰值允许最大为有效值的3倍。

最大有效值为Pomax/V oe=4800W/220V≈16.5A。

4）整机效率：设计目标η≥78%。

5）输入电压：输入：110/220V直流电压波动±15%1.2主电路形式选择1.2.1无工频变压器的逆变电源工作原理逆变电路以PWM方式首先将220VDC电压逆变成高频方波，经高频升压变压器升压，再整流滤波得到一个稳定的直流电压，比如350VDC。

这部分电路实际上是一套直流/直流变换器，既DC/DC或DC-DC。

然后，由另一套逆变器以SPWM方式工作，将稳定的直流电压逆变成有效值稍大于220V的SPWM电压波形，经LC滤波后，就可以得到有效值为220V的50Hz交流电压。

1.2.2主电路形式无工频变压器的逆变电源实际上包含两部分：一套DC/DC和一套SPWM逆变器。

DC/DC的设计这里我们不讨论。

所以，这里只讨论SPWM逆变主电路，其电路形式如下图所示,电源350V。

单相SPWM逆变主电路1.3 参数设计1.3.1开关管逆变器允许输出峰值电流为Im=3Iom=3*5.5A=16.5A所以开关管选择额定电压为600V，额定电流30A。

1.3.2 LC滤波L为工频电感，电感量可选为1～3mH。

为减小噪声，选闭合铁芯，如OD 型硅钢铁芯（400Hz）或铁粉芯铁芯。

C为工频电容，可以选CBB61-10µF-250V AC。

用SG3525制作的正弦波逆变驱动电路
1.正弦波振荡器、精密整流电路、50HZ同步波发生电路,加法电路等和前次贴子中的基本一样,没有大的变动;供稳压用的误差放大器U3A的接法稍做了一些改动,主要是为了提高抗干扰性能及控制灵敏度等.
2.主芯片SG3525的接法和一般常规接法有点不同,因为3525的11,14脚是图腾柱输出,我把11,14脚接地,屏蔽了图腾柱的下管,并在13脚接一个上拉是阻做负载,这样做的目的是把原11,14脚的信号合并在一起输出,以大幅度地提高最大比空比.母线电压的利用率也大幅度提高了,可以在94%以上.但从13脚出来的脉冲,是反向的SPWM波,所以,要用一个4069把它反回来.
3.对死区时间生产部分进行了重新设计,U7和R31R32R33R34及
C20C21C22C23就是死区时间调整电路.当R=47K,C=47P 时,高频波的死区时间大约为2uS,这4个电容要用高频瓷片电容.
特别说明:该电路可以直接推动H桥,但我的H桥输入端是光藕,其方式是低电平有效.如果用的电路是其它推动方式,其要求为高电平有效的话,则时序电路和死区电路要做一点修改,有图片供参考.
电路的调试比较简单(从原来5个电位器减少到三个电位器),只要元件没有问题,接线没有错误,一般通电就可以工作.先断开跳线JP1,让电路开环,调VR1使输出正弦波不削顶;调VR2使正弦波上下半波衔接自然光滑;再合上JP1,调VR3,把输出电压调到预定值就可以了.。

SG3525在电力电子技术中的应用研究实验一、SG3525A 脉宽调制器控制电路一．简介：SG3525A 系列脉宽调制器控制电路可以改进为各种类型的开关电源的控制性能和使用较少的外部零件。

在芯片上的5.1V 基准电压调定在±1％，误差放大器有一个输入共模电压范围。

它包括基准电压，这样就不需要外接的分压电阻器了。

一个到振荡器的同步输入可以使多个单元成为从电路或一个单元和外部系统时钟同步。

在C T 和放电脚之间用单个电阻器连接即可对死区时间进行大范围的编程。

在这些器件内部还有软起动电路，它只需要一个外部的定时电容器。

一只断路脚同时控制软起动电路和输出级。

只要用脉冲关断，通过PWM （脉宽调制）锁存器瞬时切断和具有较长关断命令的软起动再循环。

当V CC 低于标称值时欠电压锁定禁止输出和改变软起动电容器。

输出级是推挽式的可以提供超过200mA 的源和漏电流。

SG3525A 系列的NOR （或非）逻辑在断开状态时输出为低。

·工作范围为8.0V 到35V ；·5.1V ±1.0％调定的基准电压；·100Hz 到400KHz 振荡器频率；·分立的振荡器同步脚；二．SG3525A 内部结构和工作特性：（1）基准电压调整器基准电压调整器是输出为5.1V ，50mA ，有短路电流保护的电压调整器。

它供电给所有内部电路，同时又可作为外部基准参考电压。

若输入电压低于6V 时，可把15、16脚短接，这时5V 电压调整器不起作用。

（2）振荡器3525A 的振荡器，除C T 、R T 端外，增加了放电7、同步端3。

R T 阻值决定了内部恒流值对C T 充电，C T 的放电则由5、7端之间外接的电阻值R D 决定。

把充电和放电回路分开，有利于通过R D 来调节死区的时间，因此是重大改进。

这时3525A 的振荡频率可表为：)R 3R 7.0(C 1f D T T S +=（3.1）在3525A 中增加了同步端3专为外同步用，为多个3525A 的联用提供了方便。

等级: 湖南工程学院课程设计课程名称电力电子技术课题名称 SG3525正弦波逆变电源设计专业班级学号姓名指导教师2013年12 月16 日湖南工程学院课程设计任务书课程名称单片机原理及应用课题智能密码锁设计专业班级学生姓名学号指导老师审批任务书下达日期2013 年12 月16 日设计完成日期2013 年12 月27 日设计内容与设计要求一．设计内容：1．电路功能：1）逆变就是将直流变为交流。

由波形发生器产生50Hz、幅度可变的正弦波，与锯齿波比较后，再通过PWM电路，输出SPWM波，经过驱动电路驱动逆变电路进行逆变，再经过高频变压器与滤波电路输出-50Hz的正弦波。

2）电路由主电路与控制电路组成，主电路主要环节：高频逆变电路、滤波环节。

控制电路主要环节：正弦信号发生电路、脉宽调制PWM、电压电流检测单元、驱动电路。

3）功率变换电路中的高频开关器件采用IGBT或MOSFET。

4）系统具有完善的保护2. 系统总体方案确定3. 主电路设计与分析1）确定主电路方案2）主电路元器件的计算及选型3）主电路保护环节设计4. 控制电路设计与分析1）检测电路设计2）功能单元电路设计3）触发电路设计4）控制电路参数确定二．设计要求：1．要求输出正弦波的幅度可调。

2．用SG3525产生脉冲。

3．设计思路清晰，给出整体设计框图；4．单元电路设计，给出具体设计思路和电路；5．分析所有单元电路与总电路的工作原理，并给出必要的波形分析。

6．绘制总电路图7．写出设计报告；主要设计条件1．设计依据主要参数1）输入输出电压：输入（DC）+15V、10V（AC）2）输出电流：1A3）电压调整率：≤1%4）负载调整率：≤1%5）效率：≥0.82. 可提供实验与仿真条件说明书格式1．课程设计封面；2．任务书；3．说明书目录；4．设计总体思路，基本原理和框图（总电路图）；5．单元电路设计（各单元电路图）；6．故障分析与电路改进、实验及仿真等。

基于SG3525的单相桥式逆变器的设计与仿真
 逆变器是指通过半导体功率器件（如GTR、MOSFET和IGBT等）的导
通与关断，将直流电能转换成交流电能，是整流器的反向变换装置。

 1．逆变电路的工作原理
 逆变器通过开关器件的有序导通与关断将直流变换为交流方波。

当交流侧接在电网上时，即交流电接有电源，称为有源逆变；当交流侧直接和负载连接时，称为无源逆变。

逆变器在工作过程中电流不断从一个支路流向另一个支路，这就是换流。

换流方式在逆变电路中占有突出的地位。

MOSFET属于全控型器件，可利用其自关断能力进行换流单相（器件换流）。

 图l中Ql～Q4是典型的桥式电路。

当Ql、Q4导通，Q2、Q3关断时，电流从Ql流向Q4，负载电压为正；同理，当Ql、Q4关断，Q2、Q3导通时，负载电压为负，这样就将直流电转变为交流电，改变两个臂导通的切换频率，即可改变输出交流电的频率，这就是逆变电路最基本的工作原理。

当负载为电阻时，负载电流和电压的波形相同，相位也相同；当负载为电感时，电流相位滞后于电压，两者波形也不相同。

 图1 全桥逆变电路。

湖南工程学院课 程 设 计课程名称 电力电子技术 课题名称 SG3525正弦波逆变电源设计专 业 班 级 学 号姓 名指导教师2013年12 月 16 日湖南工程学院课程设计任务书课程名称单片机原理及应用课题智能密码锁设计专业班级学生姓名学号指导老师审批任务书下达日期 2013 年 12 月 16 日设计完成日期 2013 年 12 月 27 日第1章概述 (1)1.1课题来源 (1)1.2解决方法 (1)1.3设计的优点 (2)第2章系统总体设计 (2)2.1 系统设计总体思路 (2)2.1 系统基本工作原理 (3)2.3 系统设计框图 (4)第3章系统主电路设计 (5)3.1 系统主电路结构设计 (5)3.2 系统保护电路设计 (5)第4章单元电路设计 (6)4.1 正弦信号发生电路设计 (6)4.2 宽度调制PWM电路设计 (7)4.3 电压电流检测电路设计 (11)4.4 光耦合驱动电路设计 (12)第6章总结与体会 (13)附录1 总电路图 (14)附录2 参考文献 (15)附录3 课程设计成绩评分表 (16)第1章概述1.1课题来源电力逆变电源有着广泛的用途，它可用于各类交通工具，在太阳能及风能发电领域，逆变器有着不可替代的作用。

电力控制系统的可靠程度是电力系统和设备可靠、高效运行的保证，而电力控制系统必须具备安全可靠的控制电源。

电力系统中为保证变电所的诸如后台机、通讯设备等能在交流电源停电后不间断工作，工程做法一般采用UPS电源作为主要解决方案，但UPS电源存在容量小、价格贵、故障率高等不足，因此综合自动化变电所中可采用电力正弦波逆变电源来代替常规不间断UPS电源。

1.2解决方法逆变电源是一种采用电力电子技术进行电能变换的装置，它从交流或直流输入获得稳压恒频的交流输出。

利用逆变电源可以解决UPS电源存在的各种缺点，可以很好的运用在一些不能断电的场合。

本相正弦波SPWM逆变电源的设计以SG3252为核心，采用了运算放大器、二极管、功率场效应管、电容和电阻等器件来组成电路。

基于SG3525的开关电源设计第一篇：基于SG3525的开关电源设计基于SG3525的开关电源设计摘要介绍了SG3525芯片的内部结构，分析了其特性和工作原理，设计了一款基于SG3525可调占空比的推挽式DC／DC开关电源，给出了系统的电路设计方法以及主要单元电路的参数计算，并对该电源进行了性能测试。

实验表明，该电源具有效率高、输出电压稳定等优点。

关键词 SG3525；高频变压器；PWM；开关电源随着电能变换技术的发展，功率MOSFET被广泛应用于开关变换器中。

为此，美国硅通用半导体公司(Silieon General)推出了SG3525，以用于驱动n沟道功率MOSFET。

SG3525是电流控制型PWN控制器，可在其脉宽比较器的输入端直接用流过输出电感线圈信号与误差放大器输出信号进行比较，从而调节占空比，使输出的电感峰值电流跟随误差电压变化而变化。

由于结构上有电压环和电流环双环系统，因此，开关电源无论是电压调整率、负载调整率和瞬态响应特性都有提高，是目前比较理想的新型控制器。

介绍了由SG3525芯片为控制核心的500 W高频开关电源模块，该电源模块可应用于车载逆变电源的前级升压。

SG3525的结构特性SG3525脉宽调制控制器，不仅具有可调整的死区时间控制功能，而且还具有可编式软起动，脉冲控制封锁保护等功能。

通过调节SG3525第5脚上CT的电容和第6脚RT上的电阻就可以改变输出控制信号PWM的频率，调节第9脚COMP的电压可以改变输出脉宽，这些功能可以改善开关电源的动态性能和简化控制电路的设计。

1．1 SG3525内部结构SG3525的内部结构如图1所示，由基准电压调整器、振荡器、误差放大器、比较器、锁存器、欠压锁定电路、闭锁控制电路、软起动电路和输出电路构成。

1．2 欠压锁定功能基准电压调整器的输入电压为15脚的输入电压VC，当VC低于8 V时，基准电压调整器的输出精度值就得不到保证，由于设置了欠压锁定电路，当出现欠压时，欠压锁定器输出一个高电平信号，再经过或非门输出转化为一个低电平信号输出到T1和T5的基极，晶体管T1和T5关断，SG3525的13脚输出为VC，11脚和14脚无脉冲输出，功率驱动电路输出至功率场效应管的控制脉冲消失，变换器无电压输出，从而实现欠压锁定保护的目的。

基于sg3525逆变器的设计与实现基于SG3525逆变器的设计与实现SG3525是一款常用的电源管理集成电路，常被用于逆变器的设计与实现。

逆变器是将直流电转换为交流电的装置，广泛应用于太阳能发电系统、不间断电源等领域。

本文将介绍基于SG3525逆变器的设计原理和实现方法。

一、设计原理SG3525是一款双路可调节脉宽调制（PWM）控制器，其主要功能是产生可调的PWM信号，用于控制Mosfet开关管的导通和断开，从而实现对输出电压和频率的调节。

逆变器的设计原理是通过将直流电输入通过开关器件切割成一系列短脉冲，然后经过滤波电路转换为交流电。

具体实现方法如下：1. 输入电压稳压逆变器的输入电压一般是直流电压，需要通过稳压电路将其稳定在一定的范围内。

常用的稳压电路有电流限制电路和过压保护电路等，可以根据实际需求选择合适的稳压电路。

2. SG3525控制电路SG3525芯片的引脚包括输入电压Vcc、GND和反馈引脚FB，以及控制引脚如频率控制引脚CT、脉冲宽度调节引脚RT等。

通过调节这些引脚的电压，可以实现对输出电压和频率的调节。

3. Mosfet开关管逆变器的核心部件是Mosfet开关管，它负责将输入电压切割成一系列短脉冲。

Mosfet开关管有导通和断开两个状态，通过控制其导通和断开的时间，可以调节输出电压和频率。

4. 输出滤波电路逆变器的输出是由一系列短脉冲组成的交流电，需要通过滤波电路将其转换为平滑的交流电。

常用的滤波电路有LC滤波器和RC滤波器等，可以选择适当的滤波电路来实现输出电压的稳定。

二、实现方法基于SG3525逆变器的设计与实现需要按照以下步骤进行：1. 确定输出功率和电压需求，选择合适的Mosfet开关管和滤波电路。

2. 按照SG3525的管脚连接图，连接SG3525芯片和外部元件，包括稳压电路、Mosfet开关管和滤波电路等。

3. 根据输出功率和电压需求，调节SG3525的控制引脚电压，确定输出电压和频率。

基于SG3525设计单相正弦波SPWM逆变电源外文翻译外文文献Switched-mode power supplyA switched-mode power supply (also switching-mode power supply, SMPS, or simply switcher) is an electronic power supply unit (PSU) that incorporates a switching regulator. While a linear regulator maintains the desired output voltage by dissipating excess power in a pass power transistor, the switched-mode power supply switches a power transistor between saturation (full on) and cutoff (completely off) with a variable duty cycle whose average is the desired output voltage. It switches at a much-higher frequency (tens to hundreds of kHz) than that of the AC line (mains), which means that the transformer that it feeds can be much smaller than one connected directly to the line/mains. Switching creates a rectangular waveform that typically goes to the primary of the transformer; typically several secondaries feed rectifiers, series inductors, and filter capacitors to provide various DC outputs with low ripple.The main advantage of this method is greater efficiency because the switching transistor dissipates little power in the saturated state and the off state compared to the semiconducting state (active region).Other advantages include smaller size and lighter weight (from the elimination of low frequency transformers which have a high weight) and lower heat generation due tohigher efficiency. Disadvantages include greater complexity, the generation of high amplitude, high frequency energy that the low-pass filter must block to avoid electromagnetic interference (EMI), and a ripple voltage at the switching frequency and the harmonic frequencies thereof.A note about terminologyAlthough the term "power supply" has been in use since radios were first powered from the line/mains, that does not mean that it is a source of power, in the sense that a battery provides power. It is simply a device that (usually) accepts commercial AC power and provides one or more DC outputs. It would be more correctly referred to as a power converter, but long usage has established the term.1ClassificationSMPS can be classified into four types according to the input and output waveforms: AC in, DC out: rectifier, off-line converter input stageDC in, DC out: voltage converter, or current converter, or DC to DC converter AC in, AC out: frequency changer, cycloconverter, transformer DC in, AC out: inverterInput rectifier stageIf the SMPS has an AC input, then the first stage is to convert the input to DC. This is called rectification. The rectifier circuit can beconfigured as a voltage doubler by the addition of a switch operated either manually orautomatically. This is a feature of larger supplies to permit operation from nominally 120 volt or 240 volt supplies. The rectifier produces an unregulated DC voltage which is then sent to a large filter capacitor. The current drawn from the mains supply by this rectifier circuit occurs in short pulses around the AC voltage peaks. These pulses have significant high frequency energy which reduces the power factor. Special control techniques can be employed by the following SMPS to force the average input current to follow the sinusoidal shape of the AC input voltage thus the designer should try correcting the power factor. An SMPS with a DC input does not require this stage. An SMPS designedfor AC input can often be run from a DC supply (for 230V AC this would be 330V DC), as the DC passes through the rectifier stage unchanged.It's however advisable to consult the manual before trying this, though most supplies are quite capable of such operation even though nothing is mentioned in the documentation. However, this type of use may be harmful to the rectifier stage as it will only utilize half of diodes in the rectifier for the full load. This may result in overheating of these components, and cause them to fail prematurely.If an input range switch is used, the rectifier stage is usually configured to operate as a voltage doubler when operating on the low voltage (~120 VAC) range and as a straight rectifier when operating on the high voltage (~240 VAC) range. If an input range switch is not used,then a full-wave rectifier is usually used and the downstream inverter stage is simply designed to be flexibleenough to accept the wide range of dc voltages that will be produced by the rectifier stage. In higher-power SMPSs, some form of automatic range switching may be used.Inverter stageThe inverter stage converts DC, whether directly from the input or from the 2rectifier stage described above, to AC by running it through a power oscillator, whose output transformer is very small with few windings at a frequency of tens or hundreds of kilohertz (kHz). The frequency is usually chosen to be above 20 kHz, to make it inaudible to humans. The output voltage is optically coupled to the input and thus very tightly controlled. The switching is implemented as a multistage (to achieve high gain) MOSFET amplifier. MOSFETs are a type of transistor with a low on-resistance and a high current-handling capacity. Since only the last stage has a large duty cycle, previous stages can be implemented by bipolar transistors leading to roughly the same efficiency. The second last stage needs to be of a complementary design, where one transistor charges the last MOSFET and another one discharges the MOSFET. A design using a resistor would run idle most of the time and reduce efficiency. All earlier stages do not weight into efficiency because power decreases by a factor of 10 for every stage (going backwards) and thus the earlierstages are responsible for at most 1% of the efficiency. This section refers to the block marked Chopper in the block diagram.Voltage converter and output rectifierIf the output is required to be isolated from the input, as isusually the case in mains power supplies, the inverted AC is used todrive the primary winding of a high-frequency transformer. This converts the voltage up or down to the required output level on its secondary winding. The output transformer in the block diagram serves this purpose.If a DC output is required, the AC output from the transformer is rectified. For output voltages above ten volts or so, ordinary silicon diodes are commonly used. For lower voltages, Schottky diodes are commonly used as the rectifier elements; they have the advantages offaster recovery times than silicon diodes (allowing low-loss operationat higher frequencies) and a lower voltage drop when conducting. Foreven lower output voltages, MOSFETs may be used as synchronousrectifiers; compared to Schottky diodes, these have even lowerconducting state voltage drops.The rectified output is then smoothed by a filter consisting of inductors and capacitors. For higher switching frequencies, components with lower capacitance and inductance are needed.Simpler, non-isolated power supplies contain an inductor instead ofa transformer. This type includes boost converters, buck converters, and the so called buck-boost converters. These belong to the simplest classof single input, single output converters which utilize one inductor and one active switch. The buck converter reduces the3input voltage in direct proportion to the ratio of conductive timeto the total switching period, called the duty cycle. For example anideal buck converter with a 10 V input operating at a 50% duty cyclewill produce an average output voltage of 5 V. A feedback control loopis employed to regulate the output voltage by varying the duty cycle to compensate for variations in input voltage. The output voltage of aboost converter is always greater than the input voltage and the buck-boost output voltage is inverted but can be greater than, equal to, or less than the magnitude of its input voltage. There are many variations and extensions to this class of converters but these three form thebasis of almost all isolated and non-isolated DC to DC converters. By adding a second inductor the ?uk and SEPIC converters can be implemented, or, by adding additional active switches, various bridge converters can be realised.Other types of SMPSs use a capacitor-diode voltage multiplierinstead of inductors and transformers. These are mostly used for generating high voltages at low currents (Cockcroft-Walton generator). The low voltage variant is called charge pump. RegulationA feedback circuit monitors the output voltage and compares it witha reference voltage, which is set manually or electronically to the desired output. If there is an error in the output voltage, the feedbackcircuit compensates by adjusting the timing with which the MOSFETs are switched on and off. Thispart of the power supply is called the switching regulator. The Chopper controller shown in the block diagram serves this purpose. Depending on design/safety requirements, the controller may or may not contain an isolation mechanism (such as opto-couplers) to isolate itfrom the DC output. Switching supplies in computers, TVs and VCRs have these opto-couplers to tightly control the output voltage.Open-loop regulators do not have a feedback circuit. Instead, theyrely on feeding a constant voltage to the input of the transformer or inductor, and assume that the output will be correct. Regulated designs compensate for the parasitic capacitance of the transformer or coil. Monopolar designs also compensate for the magnetic hysteresis of the core.The feedback circuit needs power to run before it can generate power, so an additional non-switching power-supply for stand-by is added.Transformer designSMPS transformers run at high frequency. Most of the cost savings (and space savings) in off-line power supplies come from the fact that a high frequency 4transformer is much smaller than the 50/60 Hz transformers formerly used.There are several differences in the design of transformers for 50Hz vs 500 kHz. Firstly a low frequency transformer usually transfersenergy through its core (soft iron), while the (usually ferrite) core of a high frequencytransformer limits leakage. Since the waveforms in a SMPS are generally high speed (PWM square waves), the wiring must be capable of supporting high harmonics of the base frequency due to the skin effect, which is a major source of power loss.Power factorSimple off-line switched mode power supplies incorporate a simplefull wave rectifier connected to a large energy storing capacitor. Such SMPSs draw current from the AC line in short pulses when the mains instantaneous voltage exceeds the voltage across this capacitor. During the remaining portion of the AC cycle the capacitor provides energy to the power supply.As a result, the input current of such basic switched mode power supplies has high harmonic content and relatively low power factor. This creates extra load on utility lines, increases heating of the utility transformers and standard AC electric motors, and may cause stability problems in some applications such as in emergency generator systems or aircraft generators. Harmonics can be removed through the use of filter banks but the filtering is expensive, and the power utility may require a business with a very low power factor to purchase and install the filtering onsite.In 2001 the European Union put into effect the standardIEC/EN61000-3-2 to set limits on the harmonics of the AC input current up to the 40th harmonic for equipment above 75 W. The standard defines four classes of equipment depending on its type and current waveform. The mostrigorous limits (class D) are established for personal computers, computer monitors, and TV receivers. In order to comply with these requirements modern switched-mode power supplies normally include an additional power factor correction (PFC) stage.Putting a current regulated boost chopper stage after the off-line rectifier (to charge the storage capacitor) can help correct the power factor, but increases the complexity (and cost).Quasiresonant ZCS/ZVSA quasiresonant ZCS/ZVS switch (Zero Current/Zero Voltage) is a design where "each switch cycle delivers a quantized 'packet' of energy to the converter output, and switch turn-on and turn-off occurs at zero current and voltage, resulting in an5essentially lossless switch."EfficiencyHigher input voltage and synchronous rectification mode makes the conversion process more efficient. Higher switch frequency allows component size to be shrunk, but suffer from radio frequency (RF) properties on the other hand. The power consumption of the controller also has to be taken into account.ApplicationsSwitched-mode PSUs in domestic products such as personal computers often have universal inputs, meaning that they can accept power from most mains supplies throughout the world, with rated frequencies from 50 Hz to 60 Hz and voltages from 100 V to 240 V (although a manual voltage range switch may be required). In practice they will operate from a much wider frequency range and often from a DC supply as well. In 2006, at an Intel Developers Forum, Google engineers proposed the use of a single 12 V supply inside PCs, due to the high efficiency of switch mode supplies directly on the PCB.Most modern desktop and laptop computers already have a DC-DC converter on the motherboard, to step down the voltage from the PSU or the battery to the CPU core voltage, as low as 0.8 V for a low voltage CPU to 1.2-1.5 V for a desktop CPU as of 2007. Most laptop computers also have a DC-AC inverter to step up the voltage from the battery to drive the backlight, typically around 1000 Vrms.Certain applications, such as in automobile industry where ordinary cars often use 12 V DC and in some industrial settings, DC supply is chosen to avoid hum and interference and ease the integration of capacitors and batteries used to buffer the voltage. Most small aircraft use 28 V DC, but larger aircraft like Boeing-747 often use up to 90 kVA 3-phase at 200 V AC 400 Hz, though they often have a DC bus as well. Even fighter planes like F-16 use 400 Hz power. The MD-81 airplane has an 115/200 V 400 Hz AC and 28 V DC power system generated by three 40kVA AC generators. Helicopters also use the 28 V DC system. Some submarines like the Soviet Alfa class submarine utilized two synchronous generators providing a variable three-phase current, 2 x 1500 kW, 400 V, 400 Hz. The space shuttle uses three fuel cells generating 30 - 36 V DC. Some is converted into 400 Hz AC power and 28 V DC power. The International Space Station uses 120 V DC power. Larger trucks uses 24 V DC.See also: Avionics, Airplane ground support6In the case of TV sets, for example, one can test the excellent regulation of the power supply by using a variac. For example, in some models made by Philips, the power supply starts when the voltage reaches around 90 volts. From there, one can change the voltage with the variac, and go as low as 40 volts and as high as 260 (known such case that voltage was 360), and the image will show absolutely no alterations.TerminologyThe term switchmode was widely used until Motorola trademarked SWITCHMODE(TM), for products aimed at the switching-mode power supply market, and started to enforce their trademark.7外文翻译开关模式电源开关模式电源(也开关式电源，开关电源，或只是交换机)是一种电子电源供应器(电源)，包含了开关稳压器。

SG3525的纯硬件SPWM驱动板制作实例SG3525的纯硬件SPWM驱动板制作实例SG3525的纯硬件SPWM驱动板制作实例电源网讯自去年我做了一款用3525的纯硬件SPWM驱动后，关注的网友比较多,老寿颇感欣慰，但毕竟是实验性的，存在的问题还不少，如:50HZ基波振荡器的失真和温漂问题，反馈稳压问题等等。

就象一个学书法的人，练了一段时间书法，再回过头去看看原先写的字，才感觉到原先写的那些字实在不行，学电子也同样，现在我再回过头去看看自已原先设计的东西，才知道有很多方面的不成熟。

当然，用单片机产生SPWM是很方便的，也是今后发展的趋向，但单片机不是人人都能驾驭的，象我这样的不懂单片机编程的人很多，就是能编程的，也不是人人都能写出好的SPWM程序来。

当然，用单片机的SPWM具有性能稳定，一致性好等优点。

所以，我觉得用单片机的SPWM比较适合做产品，如果要玩的话，可能还是纯硬件具有挑战性。

就象现在的汽车有了自动档，但也有很多人还是喜欢开手动档，认为只有手动档才有驾驶的感觉云云。

这几天做的这款用3525的硬件SPWM 驱动器，有如下特色：1.取消了双电源，用单电源12V供电，供电比较简单；2.解决了文氏振荡器的温漂问题，现在我用1000W电吹风吹它，它的幅度变化在0.1Vpp左右，而第一版电路，在电吹风下要变化40%；3.提高了正弦波的精度，用失真仪测第一版的正弦波，失真在2.5%以上，难怪看上去波头都有点歪，现在的正弦波精度提高到0.4%，经还原后的失真度在0.7%左右，波形很漂亮了。

4.改进了稳压电路，第一版采用的是用误差放大器稳压，主要是一个相位差的问题难解决，稳压精度很低。

现在，我用了直流反馈的方式，用电压控制的放大器来闭环稳压，精度大大提高，如果其它元件选取合理，输出电压可以稳定在正负2V之内。

还有一个好处，因为用了直流反馈稳压，所以反馈电路的干扰大大的减小了，调试也显得十分简单。

5.有商用价值，广州那边，已经有人用我的这个图纸把电路封装成厚膜电路，用在商用逆变器上。