High-Frequency High-Density Bidirectional EV Charger

Due to the rapid adoption of Electric Vehicles (EVs) worldwide, On-Board/ Off-Board Battery Chargers are facing numerous. One challenge is charging time since petrol and diesel vehicles are charged 10 times faster than electric vehicles. A second challenge is power density especially for the on-board chargers where minimal space for installation is allocated inside the vehicles. Another challenge is the wide battery voltage range which makes it difficult to optimize the converter over the entire battery voltage range and efficiency drops when either the battery voltage is too high or too low. Finally, the bi-directional operation is a challenge to allow the EV to support the grid in peak periods or even standalone loads. In this paper, a 6.6 kW two-stage structure is proposed utilizing a variable dc-link voltage operation. One of the most promising challenges in high-power applications is implementing the magnetics component into Printed Circuit Boards (PCBs). PCB winding transformers are widely in use in low power applications. Compared with conventional litz-wire transformers, the manufacturing process is greatly simplified and the parasitic is easier to control. However, due to the limitation of high winding loss and high multi-layer PCB cost in high power applications, the transformer design with PCB winding becomes a challenge. Emerging wide-bandgap devices provide the opportunity to adopt PCB transformers into high power applications. In addition, the low inductance requirement brought by high frequency also makes possible the realization of magnetic integration in PCB transformers.