A Study of Switching Frequency Impact on Reliability of DC-DC PoL Converters with Discrete Transistors

Using a buck converter to regulate voltage, PoL DC-DC converters involve an inherent switching action via switching frequency f
sw
. The value of the switching frequency can influence the entire performance of the converter and this justifies the importance of this study. This paper is analyzing the influence of switching frequency on the reliability of the DC-DC PoL converter. This is demonstrated in terms of efficiency, thermal response, and ripple. In addition, several bench test results are shown for a switching frequency variation in a range of 50 kHz to 500 kHz, using a discrete SiMOSFET based PoL synchronous buck converter evaluation board. The switching loss in power devices, as well as the driver loss, are directly influenced by the switching frequency. The reliability calculation is based on the temperature of the device when the converter is working on a common load. A thermal scanning of the MOSFET surface is herein based on infrared photography. A modern prediction standard, like IEC-TR-62380, takes into account the concept of mission profile and it has been used to deliver information about the reliability of the converter as close as possible to reality.