Study On A Novel Zero-Voltage And Zero-Current Three-Level Full-Bridge Converter

It becomes an important developing direction of power electronic technology today that power equipments have fine environmental protecting performance. Boost power factor correction is used to reduce the pollution of current harmonic. But it leads that output voltage is higher than the peak value of input voltage. It makes that voltage stress of switchs of latter DC converter increases greatly. The advantage of three-level DC converter is that the voltage stress is only the half of input voltage. Associated with soft-switched, it is very suitable for the occasions of high input voltage, middle or large power. Analyzing the pluses and minuses to all kinds of TL soft-switched converters appearing at present, a novel zero-voltage and zero-current (ZVZCS) pulse-width modulation (PWM) TL converter is put forward. And the converter can eliminate or improve the phenomenon of duty losing, improve efficiency and practicability of converter. Compared with similar ZVZCS PWM TL converter, it reduces the use of the magnetic device and design difficulty, and improves the efficiency and dependability. In this dissertation, the operation principle and the equivalent circuit structures in different periods of time of the novel ZVZCS PWM TL converter are analyzed. The input and output characteristics of the circuit are derived. And the qualification and tactic of achieving soft-switched are also derived. Based on the above analyse, the parameter choice of the main components and the method of PWM control are analyzed. The emulation result proves that the circuit structure and control method are valid. The small-signal model, close-loop block diagram and transmission functions of ZVZCS PWM TL of converter are derived for the first time. It offers theoretic foundation of the close-loop design on detail circuit. The design and analyses of compensator are carried out with the emulation data of converter. A test prototype has been designed. The experimental result shows that the novel ZVZCS PWM TL converter is feasible in practical application. It testifies that the theory and emulation analyses are of validity and the converter has higher project value.