The Study Of High-Power High-Frequency Soft-Switching Parallel Power-Supply Module

The limited double-polarity soft-switching control scheme is presented in this thesis. The principle is analyzed. Cooperated with a capacitor and a saturatable inductor, the current in the transformer's primary side is forced to decline near to zero before the switches in the lagging leg are closed, so the Zero-current switching (ZCS) is realized. And the zero-voltage switching (ZCS) is implemented in the leading leg with the help of paralleled capacitors on the switches. Based on this scheme, the soft switching in full load range is reached for all the switches but the complexity of the control circuit is almost as same as the previous ones. The duty ratio lost in the conventional Phase-Shifted Full-Bridge PWM (PS-FB-PWM) control scheme is avoided;and the power density, the efficiency of the transformer is improved with the reducing of energy loss.Secondly, the driver circuit, the control circuit, magnetic component of the power supply are designed and optimized. With the strategy of the UC3525 core as well as an inner current-loop and an outer voltage-loop control, the output stable voltage and limited current are realized very well. And the control parameters including the PI controller is designed for the two closed loops using the method of the small signal model analyzing.Then, some popular means of current sharing are introduced and compared. Particularly, the method using the maximal current sharing one is studied in detail. The specific controller UC3907 is adopted to share the output current in balanced among the all connected modules, therefore to compose higher power supply than single module.Simulations with software ORCAD and SABER are carried out, and two 15 kW experiment prototypes in parallel connected based on the above theories are built to validate the aforementioned analysis. The results show that the converters have perfect soft switching characteristic;and the system gets a perfect dynamic current share feature with the imbalance less than 3%. So the correctness of the above mentioned analysis is verified.