Study of the Impedance of the Bypassing Network of a Switching Cell – Influence of the Positioning of the Decoupling Capacitors

Abstract

Mechanisms responsible for ringing and oscillations in power converters at transistors turn-offs are, first, studied using small signal modelling. It is explained why a 50% derating must be applied to high-speed transistors. Experimental measurements validate the analytical predictions. The influence of the distance between a switching cell and its decoupling capacitors is then studied; it appears that using a low-inductance – though simple – layout results in a stray inductance as low as 11 nH when the capacitor is 30 cm away from the switching cell, enabling degrees of freedom for thermal management.