Wide bandgap power devices based high efficiency power converters for data center application

Wide band gap (WBG) power devices, such as Silicon Carbide (SiC) and Gallium Nitride (GaN) devices, have been innovatively applied in the data center power converters, which are based on the high voltage DC (HVDC) power distribution architecture, to evaluate the potential efficiency improvement. For the front-end AC-DC rectifier, a buck rectifier using SiC devices was implemented. The SiC devices were tested at first to obtain the static and switching characteristics. The number of devices in parallel, the switching frequency and the input/output filters were investigated. A prototype of 7.5 kW, 3 phase 480 VAC input, 400 VDC output front-end rectifier was built and tested. The peak efficiency reaches up to 98.55%, and the full load efficiency is 98.54%. For the intermediate DC-DC bus converter, the impact of the GaN devices on the LLC resonant converter efficiency was evaluated and compared with the Si counterparts. Based on the device loss analysis and the FEA simulation on the transformer winding loss, the GaN devices exhibited the reduced device loss, and also the capabilities to reduce the transformer winding loss. A 300 W, 400 VDC input, 12 VDC output GaN device based DC-DC bus converter was built and tested by 96.3% peak efficiency and 96.1% full load efficiency.