Efficiency evaluation of a SiC-based bidirectional boost converter using TCM-ZVS with different voltage conversion ratios

The design-oriented analysis of an 800V-output voltage SiC-based bidirectional boost dc-dc converter is presented in this paper. The main objective is to obtain high efficiency among the wide power range thanks to the Zero Voltage Switching (ZVS) achieved with Triangular Current Mode (TCM) operation. In fact, TCM enhances the high efficiency from high power levels to low power levels, but it requires a variable switching frequency operation and a large inductor current ripple. These two drawbacks can be overcome by using SiC (Silicon Carbide) MOSFETs and interleaved techniques between different bidirectional boost dc-dc modules.Operating in TCM at very low power levels, specific values of both the negative peak inductor current and dead-time are mandatory to achieve ZVS. An analytical study is presented in order to minimize the dead-time power losses by selecting an adequate negative peak inductor current value and dead-time value when input voltage vary. Traditionally, the dead-time power losses have been neglected because it is assumed that they have low impact in total power losses. However, this fact could be different at high switching frequency operation, especially if SiC MOSFETs are used because they present high reverse conduction voltage drop. For this reason, this paper proposes the inclusion of the dead-time power losses in traditional power loss models. Finally, an experimental prototype of a 10 KW SiC-based bidirectional boost dc-dc converter is tested to check the selection of the optimum values of dead-time and minimum negative peak inductor current in order to minimize power losses, and to extend the high efficiency among the wide power range.