Based On The Parallel Flow Technology Of High-frequency Soft Switching Power Supply

With the development of Soft-switching PWM and paralleling current sharing, the research on large capacity and high-frequency switching power has already become the main research field of power electronics. Each parallel module can take its share of the load and the current stress of power switch can be reduced greatly. The demand on characteristic, capacity, weight, volume, efficiency and reliability can also be achieved. The main content of this paper is to develop a 110V high-frequency and soft-switching power supply based on paralleling current sharing, which is great meaning for improving the technique level of locomotive power supply.The theory of phase-shifted full-bridge ZVS PWM DC/DC converter circuit is studied and analyzed. The method of achieving ZVS for the lagging arm and the loss of duty cycle are discussed. And a novel full bridge topology based on secondary active clamp circuit is proposed. This topology can achieve an extreme wide load range under soft switching for both legs and satisfy the demand of the large capacity very well. Soft, switching power supply module is the important part for the system, which is controlled by the phase-shifted controller UC3875. Based on the IGBT working in the soft-switching condition, the design of power supply module's main circuit and the Selection of apparatus's parameters are completed. Besides the control circuit, protect circuit and the supvise and communicate unit of the power supply system are analyzed and designed.A few measures of current sharing are discussed and compared. The method of the most current automatic current sharing is particulary introduced. Then, based on the work principium, the startup characteristic and analysis of stability, the current-sharing circuit of the power is designed, which used the current-sharing controller UC3907 to realized paralleling multi-module system.Finally, experimental result of the power supply module and measured data are presented in paralleling operation, which proved the exactness of the theory analyses and the rationality of the design.