Research Of Passive Lossless Soft-switching Technology For Switching Converters

To reduce the volume, weight and improve the dynamic characteristics of Power electronic circuits, the important way is to increase the switching frequency of the circuits. However, With the enhancement of frequency, the dissipation of the main power switch, Electro-Magnetic Interference (EMI) problem increases as well. Too much switching loss will lower the efficiency of converters; serious EMI noise will affect the control of converters. How to improve the working condition of power switches, lower switching loss and Electro-Magnetic Interference (EMI) problem, reduce the current and voltage stress and the du/dt&di/dt of the switch, has been one of the focus people study.Traditional RCD snubber transfers the energy of switching to resistance and consumes, but the energy loss still exists. Therefore, lossless soft switching technology is studied an applied to reduce the loss, and improve the switching performance of Power electronic circuits. Lossless soft switching technology can be separated into passive lossless soft switching technology and active lossless soft switching technology origin to whether or not the active switch exists. Though active lossless soft switching technology can reduce switching loss, the structure and the control are complex. Passive lossless soft switching technology just adds some passive component to converter and transfers or feedback energy to achieve the lossless effect. It can not only reduce switching loss, switch stress, EMI noise, but also has simple circuit, it needn't additional switch and control circuit, also it's cheap and has high reliability, so passive lossless soft switching technology is regarded the better replacement of the active lossless soft switching technology, received widely focus and study during recent years.This thesis summarizes the improvement and actuality of soft switching technology based on reading a great lot of literature. It starts with the basic theoretic, discuss the formative ideology and process of the passive lossless soft switching topology, it also has summarized the principle of building passive lossless soft switching topology, interpreted universal soft-switching cells for various PWM converters. On the base of theoretic study, this thesis applies the passive lossless soft switching technology into DC/DC and DC/AC PWM converters, analyses the working mode of the circuits and shows the rules of parameter design. This thesis has made the simulation of the passive lossless converters using Saber software and built passive lossless boost converters and half-bridge inverter. Theoretic analyses, simulation and experimental result indicate, passive lossless soft switching technology owns the performance of lowering switching loss, reducing the du/dt & di/dt of switch and EMI noise.