A Simple ZVS Detection Method for a Dual Active Bridge Converter

Zero voltage switching (ZVS) in dual active bridge (DAB) converter decreases the switching losses and proves to be more efficient while the converter operates at high switching frequency. In order to extend the ZVS range for achieving lower switching losses at light loads, detection of ZVS becomes important in DABs. This paper presents a simple approach to ZVS detection technique for a single phase shift (SPS) control based DAB. The proposed technique uses the voltage information of the switching device during the start of turn-on transient for detecting the ZVS condition. The proposal makes use of the idea that the voltage across the switching device is negative at the start of turn-on transient following a ZVS state while the same is positive following a hard switching state. The detection circuit is employed using a single resistor, a single D flip-flop, single op-amp based comparator and two schottky diodes - resulting in fewer components, cost effective and simpler design. The proposed method gives an added advantage wherein a single ZVS detection circuit is sufficient for ZVS detection of one full bridge of the DAB structure. The operation of the proposed ZVS detection technique was tested in Matlab/Simulink environment for a 2 kW DAB converter. The principle operation of the developed ZVS detection circuit was also tested in hardware by using a constant voltage in the place of the switching device.