Power supply design for performance and reliability

Abstract

This paper presents the results obtained from a study conducted to evaluate the long-term operational reliability of dc-dc power converters used in computer and telecom applications. A full-bridge, phase-shifted zero voltage switching (ZVS) PWM converter was investigated experimentally and theoretically it is shown that under low-load conditions, the intrinsic body diode of the MOSFET undergoes dynamic avalanching during its reverse recovery with an associated high dv/dt. This phenomenon results in an excessive power loss in the circuit and increased switching stress for the MOSFET. The converter failure under low-load conditions can be associated with this mechanism as one of the potential causes. The paper also presents experimental results obtained on dc-dc power converter prototypes smeared with zinc whiskers. It is shown that power supply arcing under these conditions is a potential cause of failure.