Design Of A Soft-Switching Power Operating Supply

As important devices, power operating supplies provide DC power for loads in power plants and substations. Phase-shifted full-bridge soft-switching converter has been widely employed to improve the efficiency and performance of power operating supply.A 2.2kW power operating supply prototype has been designed based on a modified phase-shifted full-bridge zero-voltage-switching converter in this thesis. Principles of the power stage, control system and protection circuits were discussed in detail, and the design procedure together with methods for choosing parameters were introduced at the same time.The power stage circuit topology was improved in two ways: one was placing a blocking capacitor in series with primary windings of the transformer, and the other was the application of a current dubler rectifier in secondary side. Zero-voltage-switching were realized by making full use of leakage inductance of the transformer. It was the blocking capacitor that solved flux-imbalance problem and contributed to stability of the whole converter. In the current dubler rectifier, diodes commuted naturally, which avoided voltage spikes and oscillations.The control system included two loops: an outer voltage loop and an inner current one which operated in peak-current control mode. A simple small-signal model was derived for the system, as the power stage could be treated as a first-order system in dual-loop control mode. Voltage controller was designed by adding a pole to the PI regulator. Based on highest current automatic current sharing technique, a load sharing control circuit was designed.As proved by experimental results, all power switches in the converter realized soft-switching, and that low switching losses together with EMC were acquired. The...