| Switching losses and the resulting thermal relieve problem prevent power supply from having a higher frequency operation which can lead to smaller size and less weight. Soft switching technology is an effective tool for reducing switching losses, so it can improve efficiency and raise operation frequency, which is now widely used in power supply.Firstly, this paper presents a summarization for soft switching technology, introducing its operation principal and history, and emphasizes the latest control type soft switching. In the second chapter, the full bridge topology is analyzed in detail. The operation principal and switching losses of full bridge hard switching topology are studied for comparison. Then two methods of soft switching technology are studied: ZVS and ZVZCS. Several common topologies are analyzed including their working principal, the way they achieve soft switching, soft switching range and the overall efficiency. Both merits and demerits are listed and the selection guide is given for different application. In the third chapter, two control strategy phase-shifted control and limited doubled-polarity are compared on their realization method and their influence on ZVS. After that, voltage mode control, peak current mode control and average current mode control are listed. The average current mode control is analyzed for detail and the design procedure is given too. Finally, the small-signal mode of the soft switching full bridge is given. The effect of the soft switching technology is analyzed which makes the small-signal mode slightly different from that of the traditional PWM hard switching topology. The fourth chapter gives the detailed design procedure for the 5kW full bridge converter. The fifth chapter analyzes the experimental waveforms and data, which verify the correctness of the above theory and design procedure.
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