Stress analysis of a full bridge ZVS DC-DC converter

This paper presents the MOSFET electrical stresses in a full bridge (FB) ZVS DC-DC converter with a detailed study of the MOSFET body diode reverse recovery stress under normal and low load operating conditions. Experimental results are presented under normal and low load operation for a 350 V-3.5 V, 225 A FB ZVS DC-DC converter. Two-dimensional (2-D) numerical simulation results of internal dynamics of the device during switching prove that the MOSFET body diode reverse recovery under no load conditions is stressful as opposed to the reverse recovery under normal operating condition. A test circuit is also designed to characterize the body diode reverse recovery performance. A detailed failure analysis for the MOSFETs failed in the reverse recovery test circuit under high stress conditions is also presented.