Digital Control of an Isolated Dual Half Bridge Converter

Abstract

Dual Half Bridge (DHB) converter offers bidirectional power flow and galvanic isolation between the primary and the secondary sides. It can be used in different applications requiring level conversion of DC voltage such DC micro-grids, electric vehicles and uninterrupted power supplies. In most case, the two legs of this converter are controlled with a 50% duty cycle. The voltage ratio between the primary and the secondary sides is imposed by the phase-shift between the gate signals of high-side transistors. Different hardware solutions can be found in literature for controlling the phase-shift. This paper proposes a simple control method for controlling the voltage level at the output of the DHB converter. A fully-digital solution is proposed for phase shift generation without additional external circuitry. The operating principles and design considerations are presented in the first part of the paper. Then, the proposed method for phase shift generation is discussed. The validity of this method is verified through experimental implementation on a low cost microcontroller.