1-kV Input 300-kHz SiC LLC converters with Matrix Transformers

A 1-kV input SiC LLC converter with the matrix planar transformers is proposed to achieve high efficiency and high power density. As 1 kV input voltage, high dv/dt of 11.8 kV/μs causes large displacement current via the parasitic capacitance between the primary side and secondary side of the planar transformers. The displacement current through the interwinding capacitances distorts the resonant current. This causes the control FETs cannot realize zero voltage switching (ZVS), which causes extremely high frequency switching loss. To solve this problem, a split resonant tanks topology is proposed for high input voltage SiC LLC converters. The resonant tank in the LLC converter is split into two identical resonant tanks. The circuit provides symmetrical resonant current with the same impedance. Compared with the conventional LLC converters, the input and output current of the resonant tank is the symetrical avoiding the current distortion. Therefore, all of the MOSFETs can realize ZVS. The mechanism analysis of the distorted resonant current is presented. A solution of the transformer interwinding capacitance modeling and reduction is proposed. The proposed solution reduces the waveform distortion by 68% in the example. A prototype of 3 kW SiC converter with input of 1 kV and output of 32 V/ 3 kW for tethered drone and vessel applications was built. The converters achieve the efficiency of 94.9 % at full load with the diode rectification. The power density of 3.87 kW/ L, 63.4 W/ in
³
and 4.11 kW/ kg.