Voltage Balance Switching Scheme for Series-Connected SiC MOSFET LLC Resonant Converter

Abstract

To achieve high efficiency and power density, silicon carbide (SiC)-based Inductor-Inductor-Capacitor (LLC) resonant converters are applied to the DC/DC converter stage of a solid-state transformer (SST). However, because the input voltage of an SST is higher than the rated voltage of a commercial SiC device, it is essential to connect SiC devices in series. This structure is advantageous in terms of voltage rating, but a parasitic capacitance tolerance between series-connected SiC devices causes voltage imbalance. Such imbalance greatly reduces system stability as it causes overvoltage breakdown of SiC device. Therefore, this paper proposes a switching scheme to solve the voltage imbalance between SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). The proposed scheme sequentially turns off series-connected SiC MOSFETs to compensate for the turn-off delays caused by parasitic capacitor tolerances. In addition, dead-time selection methods to achieve voltage balance and zero voltage switching simultaneously are provided in detail. To verify the effectiveness of the proposed scheme, experiments were conducted on a 2 kW series-connected SiC MOSFET LLC resonant converter prototype.

A Comprehensive Overview in Control Algorithms for High Switching-Frequency LLC Resonant Converter

“…This area is widely used in the light load and the soft-start duration. Therefore, the LLC resonant converter has been widely used in various industrial fields such as renewable energy, home appliances, and servers in data centers [11][12][13][14][15]. In addition, the LLC resonant converter is good to obtain high switching frequency operations because it has small switching losses using the ZVS and ZCS capabilities.…”

Optimal Design of LLC Resonant DC Transformer under Adaptive Frequency Tracking Strategy

“…Therefore, more attention has been paid to DC transformers with electrical isolation. The dual active bridge (DAB) converter has a simple structure, can achieve soft switching (ZVS) characteristics, and energy flows in both directions [3,4]. However, its ZVS range is limited, and the switch also has a high turn-off current, resulting in a reduction in power conversion efficiency [5].…”