A 1-kV Input SiC LLC Converter With Split Resonant Tanks and Matrix Transformers

Abstract

A 1-kV input SiC LLC converter with the matrix planar transformers is proposed to achieve high efficiency and high power density. With fast switching speed 140 ns of SiC mosfet s at 1-kV input voltage, high dv/dt of 11.8 kV/ μ s can cause large displacement current via the parasitic capacitance between the primary and secondary sides of high-frequency planar transformers. The displacement current via the interwinding capacitance can distort the resonant current seriously. This causes the control mosfet s not to realize ZVS and induces high switching loss at 1 kV. An LLC topology with split resonant tanks is proposed for high input voltage applications. The resonant tank is split into two identical resonant tanks to provide symmetrical resonant current with the same impedance. Compared with the conventional LLC converters, the input and output current of the resonant tank is symmetrical, avoiding the current distortion. Therefore, all of the control mosfet s can realize ZVS. The transformer interwinding capacitance modeling and a reduction solution are presented, which reduces the waveform distortion by 68%. Two SiC prototypes of 3 and 4 kW with an input of 1 kV and output of 32 and 48 V were built, respectively. The efficiency is 94.9% at full load at 300 kHz for a 3-kW module and 96.0% at full load for a 4-kW module. The power density is 3.87 kW/L (63.4 W/in3) and 4.11 kW/kg for the 4-kW module.