Statistical Evaluation of Current Imbalance in Parallel Devices

Abstract:
The concept of paralleling plays a fundamental role in high power applications. A source of concern is the imbalance of current due to varying parameters of devices or components. As was already stated in [U.Scheuermann: Paralleling of Chips – From the Classical ‘Worst Case’ Consideration to a Statistical Approach, Proc. PCIM Europe 2005, 455-460.], worst-case assumptions overestimate the consequences. However, the statistical method applied in this publication was incorrect. In this paper, the current and temperature imbalance of paralleled freewheeling diodes caused by a distribution in forward voltage drop will be analyzed on a correct statistical basis. The results confirm the general conclusions related to worst-case assumptions and give estimations for derating factors at defined statistical probabilities of occurrence.