With the development of semiconductor devices (mainly active switch devices), the switching frequency of PWM (Pulse Width Modulation) converters becomes higher, which makes PWM converters (mainly high-frequency transformers, inductors and capacitors in converters) smaller, and this will benefit design and application of them. What's more, higher switching frequency will reduce the audio-frequency noise and improve dynamic response of PWM converters.However, conventional PWM-conversion is a kind of hard-switching technology. That is to say, active switch device is turned on with non-zero voltage, and turned off with non-zero current. And then, as switching frequency becomes higher, the dissipation of active switch devices will increase quickly, which will lower circuit efficiency, weaken power-processing ability, and increase EMI of PWM converter. In detail, hard-switching PWM converter meets problems in turn-on and turn-off dissipation, turn-off with inductive load, capacitive turn-on, reverse recovery of diodes, and so on.Soft-switching is the main solution to above problems of PWM converter at present. It can be divided into two main types, i.e. active soft-switching and passive soft-switching, and passive soft-switching includes RC snubber and PLSS (Passive Lossless Soft-Switching).This paper studies application of PLSS in PWM power converter. On basis of synthesis and analysis of existing PLSS-PWM converters, this paper presents a PLSS-bridge inverter circuit, and makes theoretical and simulation study of it. In the end, an experiment of this novel PLSS-bridge inverter is made. The main jobs and conclusions as follows:Firstly, a novel PLSS-bridge inverter circuit was proposed, and its operation principle was analyzed. This circuit can realize soft-switching of active switching devices and energy of ZVC feeds back to the load directly, so its operation principle is simple and efficiency is high. This novel PLSS-bridge inverter works with 8 additional passive devices. Judged from existing related research documents, this is one of the PLSS-bridge inverter with least devices.Secondly, operation conditions of this novel PLSS-bridge inverter is analyzed and obtained: with correct power supply, load current, and dead-time, ZVC can be reset, and zero-voltage turn-off of active switchs will be achieved. Otherwise, only zero-currentturn-on of them can be achieved.Thirdly, simulation study of this novel PLSS-bridge inverter is made, and simulation waveforms reveal that all active switches' zero-current turn-on and zero-voltage turn-off can be achieved in correct operation conditions.Fourthly, experiment study of the PLSS-bridge inverter is made based on theoretical and simulation analysis, and experiment results verify the correctness of above theoretical and simulation study.Fifthly, this paper analyzed a PLSS-boost converter. Operation principle and process of the PLSS-boost converter are analyzed and main electrical variables' expressions are derived. These electrical variables' theoretical and simulation waveforms are given, which proves that this PLSS-boost converter can realizes active switch's zero-current turn-on and zero-voltage turn-off, and this converter's control mode won't be influenced.
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