Effectively paralleling GaN FETs to achieve ultra-high efficiency in an isolated DC-DC converter

In order to increase the power handling capability and to realize high efficiency in power converters, paralleling of GaN FETs are essential. This paper discusses the challenges in paralleling of GaN devices in an isolated full bridge DC-DC converter. When they are used for parallel operation, equal sharing of current should be ensured in the devices. A 2.4 kW isolated full bridge converter is developed with extensive paralleling of GaN devices. Current measurement in these devices is almost impossible due to their packaging as well as to avoid any parasitic impedance introduced into the circuit. An infra-red camera and the gate source voltage are used to analyze the sharing of current in these devices. Experimental results verify that the paralleled GaN FETs shares the current appropriately. The proposed converter has achieved a measured peak efficiency of 98.8% at 1.3 kW output power.