A Switching Converter Losses Decreasing Method

Authors: Nepomnyaschiy O. V., Krasnobaev Yu. V., Sazonov I. E., Yablonskiy A. P.

Annotation: A signal timing calculation method to control power switches of bidirectional switching converter (SC) with high efficiency is proposed. The method is applicable for MOSFET-based cascaded boost-buck converter, which has a negative offset current flow at the beginning of each conversion period. This current allows to perform turning on switches under zerovoltage and zero current switching condition to minimize switching losses. Meanwhile, the delay time between halfbridge transistors’ switching points is needed, when transistors’ output capacitances recharging takes place with following anti-parallel body diode of transistor is being turned on unlocking. A proposed method is based on a switching delay time of input stage transistors valuation for the worst case of SC’s components’ parameters scatter, and provides guaranteed turning on of the upper transistor of the input stage under zero voltage and zero current condition. A clarified offset current calculation method is provided which introduces described time delays and SC’s input voltage.

Keywords: switching converter, mosfet, driver circuit, switching losses, zero voltage switching, zero current switching, digital control