Robust Body Diode Characteristics of the Latest Power MOSFETs, UniFETTM II for Resonant Converters

Resonant converters are one of the most exciting power supply topologies. These converters are popular for many applications because the performance increases power efficiency, minimizes components count, and reduces Electromagnetic Interference (EMI) over older power supply topologies. Soft switching is the representative feature of resonant converters. [1][2] However, use of the body diode in resonant converters sometimes leads to system failures. The stored charge in the body diode should be completely removed to avoid high current and voltage spikes, including high dv/dt and di/dt, in these topologies. Therefore, critical parameters of power MOSFETs; such as Coss(er), Qrr, and reverse-recovery dv/dt; directly affect dynamic performance of resonant converters A new power MOSFET, called UniFETTM II, is optimized for resonant converters. It provides better reliability and higher efficiency in resonant converters.