Research And Engineering Applications Of Ull-Bridge Phase-Shifted Soft-Switching Converters

Full-bridge phase-shifted soft-switching PWM converters, because of their good advantage, are most commonly used in middle and high power occasions. The intensive study of its operating principle and operating process will help optimize the design, but also gives rise to thoughts and ideas to improve the circuit. Combining operating waveforms, the paper first carries out a detailed analysis of the operating principle of basic full-bridge phase-shifted zero-voltage soft-switching PWM converter.Full-bridge phase-shifted zero-voltage soft-switching PWM converters make use of the parasitic circuit parameters - switch tube parasitic capacitance and high-frequency transformer leakage inductance to achieve zero-voltage switching, which are parasitic parameters in traditional hard-switching PWM circuit, do not want to need. Full-bridge phase-shifted zero-voltage soft-switching PWM converter with constant frequency operation, simple control, not many components, etc., is very suitable for engineering applications. However, the full-bridge phase-shifted zero-voltage soft-switching PWM converter also has several important drawbacks: the duty cycle is lost; soft-switching can be achieved only within the framework of a certain load to full load; transformer primary side series inductor and second-side rectifier diode parasitic capacitance oscillates, and so on. In order to overcome these shortcomings, the researchers propose ways to improve the full-bridge phase-shifted soft-switching PWM converter topology. In this paper, several common improved topologies are described, which are:the use of saturable inductor at primary side to reduce duty loss, the use of transformer excitation current to extend the load range of ZVS, the use of the energy of the output inductor to extend the load range of ZVS, paralleling auxiliary network to strengthen the ZVS of lagging bridge, full-bridge phase-shifted ZVZCS PWM converter with blocking capacitor which is very suitable for the work of IGBT, and so on. In addition, combining operating waveforms, the paper carries out a detailed analysis and description of two basic types of full-bridge phase-shifted zero-voltage soft-switching PWM converter with clamping diodes at primary side. Full-bridge phase-shifted zero-voltage soft-switching PWM converters with clamping diodes at primary side,because of small additional components and simple circuit, are applied widely in engineering fields. Full-bridge converters need to add DC-blocking capacitors in main circuit due to a slight difference of turn-on time of each switch tube which can cause transformer DC bias, so that full-bridge phase-shifted zero-voltage soft - switching PWM converter with clamping diodes at primary side can be extended to four types of circuits. In this paper, four types of circuit features are list to be compared, and we can conclude that the Tr-lag TC type circuit best suits for engineering applications.Based on above theoretical analysis, we use the Tr-lag TC type circuit to design a 3KW power module. The choice of main components parameter, and the design of magnetic components, and the design of control and protection circuit, is introduced. Finally, the simulation analysis and experimental results are given.