A High-efficiency High-density Wide Bandgap Device-based Bidirectional On-board Charger
The LLC converter is the most suitable topology for DC/DC converters in server and telecom applications. In order to increase the output power and reduce the input and output current ripples, the three-phase interleaved LLC converter is becoming more and more popular. By conecting the three phases of the converter in a certain way, the three-phase LLC converter has the benefit of automatic current sharing. Different topologies of three-phase LLC converters are surveyed in this paper. And A new topology suitable for high-frequency operation is proposed, as shown in Fig. 1. The proposed LLC converter employs a delta-connected resonant capacitor network in the primary side to achieve automatic current sharing, full-bridge secondary side due to high-frequency operation, and shielding technique to reduce common mode (CM) noise. The three-phase LLC converter suffers the drawback of numerous and bulky magnetics. A novel magnetic structure is proposed to integrate three inductors and three transformers into one magnetic core. 600V GaN devices from Panasonic Corporation and 80V GaN devices from Efficient Power Conversion Corporation EPC will be employed for the primary and secondary, respectively. By pushing the switching frequency up to 1MHz, all the windings for the magnetic structure can be implemented with 4-layer PCB winding. And Additional 2-layer shielding is integrated in the PCB windings to reduce CM noise. A 1MHz 3kW 400V/48V three-phase LLC converter with the proposed magnetic structure is designed with an estimated peak efficiency >98%, as shown in Fig. 2, and a power density of > 200 W/in3.