Transphorm's TDTTP4000W066B 4 kW bridgeless totem-pole PFC evaluation board achieves very high efficiency single-phase AC-DC conversion. Using GaN FETs in the fast-switching leg of the circuit and low-resistance MOSFETs in the slow-switching leg of the circuit results in improved performance and efficiency. The TDTTP4000W066B-KIT is for evaluation purposes only.