英语翻译INTRODUCTIONNow,most inverters are two-stage inverters i

英语翻译
INTRODUCTION
Now,most inverters are two-stage inverters including a DC/DC converter with high frequency transformer and a DC/AC inverter.Compared with the older topology with low-frequency transformer,this kind of inverter has the better performances in acoustic noise,efficiency,size,weight and dynamic response.How ever,it has the following drawbacks:(1) it is too complex and reliability is relatively low; (2) its efficiency is low because of the three-stage conversion.
In order to overcome the above draw backs,two strategies have been proposed.one is the application of soft switching.In this technique,soft switching is used to decrease switching loss and to increase the switch frequency.The other one provides a simple and reliable power circuit scheme.Resonant technique and soft switching,which are the content of many researches,can increase the switch frequency to some extent.But the structural complication prevents the improvement of many characteristics such as reliability.So this paper presents two kinds of new type simple inverters to improve the performances of the supply with single-stage and less components.
1 HALF-BRIDGE SINGLESTAGE INVERTER SUITABLE FOR HIGH INPUT VOLTAGE
Fig.1 shows a schematic circuit of a half-bridge single-stage inverter suitable for high input voltage and T1 is a high-frequency transformer.
Operational principle
This kind of inverter is based on the fly-back converter.The switches V1,V2,V3 and V4 are modulated,there are four operating modes A,B,C and D.Under each mode the scheme is equivalent to a fly-back scheme.The principle of operation is as follows: