A 6.6kW SiC Bidirectional On-board Charger

This paper proposes a bidirectional architecture to implement an on-board charger (OBC) including an interleaved totem bridgeless PFC and Mode-Switched (MS) DC-DC converter. In the charging mode with the relay on, the MS DC-DC converter behave as a high efficiency Pulse Frequency Modulation (PFM) LLC converter since the charging mode is the most majority application scenario for the OBC. The PFC output voltage is regulated between 360 V to 400 V feeding into the DC-DC converter, so that 900 V SiC MOSFETs can be used both in the AC-DC and DC-DC stage to realize high frequency and high efficiency owing to the fast switching speed and high voltage rating with low on-resistance. The synchronous rectification (SR) is applied on the secondary side MOSFETs of the LLC converter to further improve the efficiency taking advantage of the bidirectional full-bridge topology. In the discharging mode with the relay off, the MS DC-DC stage is a two-stage converter. The reverse operation of the LLC converter operates as a DC-DC transformer (DCX) at the resonant point, and its output voltage is regulated to the bus voltage by a boost converter because the reverse gain of the LLC converter is lower than 1. A 6.6 kW SiC MS bidirectional OBC of DC-DC stage is built. In the charging mode, the peak efficiency is 96.37% at 6.6 kW with 380 V input voltage and 336 V output voltage. In the discharging mode, the peak efficiency is 96.87% at 3.3 kW with 346 V input voltage and 380 V output voltage.