Consideration of flyback converter using GaN devices

This paper presents the analysis and design of gallium nitride (GaN) devices based flyback converter. It is critical to optimize power loop and gate loop for flyback converter due to high dv/dt of GaN device. EPC devices with 200V/12A were used in flyback converter. Because GaN device has no avalanche voltage and is sensitive to gate voltage, one need pay more attention to design of gate driver and selection snubber circuits. Different snubber circuits for GaN based flyback converter were compared in this paper. Magnetics selection for high frequency (HF) transformer was discussed in view of size, frequency, turn ratio and loss. A detailed power loss breakdown has been executed with core loss, cooper loss, leakage inductance loss, conduction loss and switching loss. Performance, such as current/voltage stress, voltage spike, efficiency, ect., were analyzed and compared under continuous conduction mode (CCM), boundary conduction mode (BCM), discontinuous conduction mode (DCM), and BCM with valley switching. Experimental results show highest efficiency is achieved under BCM with valley switching.