Thermal Management Strategies for a High-Frequency, Bi-Directional, On-Board Electric Vehicle Charger

This work investigates thermal management strategies for a high-density on-board SiC-based 6.6 kW charger with grid-to-vehicle (G2V), vehicle-to-house (V2H), vehicle-to-grid (V2G) and vehicle-to-vehicle(V2V) power transfer capabilities. At the peak operating condition, the electrical design, which includes a DC-DC and a DC-AC power-stage on a printed circuit board (PCB), dissipates 200W from 16 surface-mount Silicon Carbide (SiC) MOSFETs and 176.1W from the magnetics (three inductors and one transformer). At the core of the cooling system is a liquid-cooled cold plate with a water-glycol coolant onto which the PCB is mounted. Using thermal simulations and experimental tests, this paper investigates three pathways for heat transfer from the MOSFETs to the cold plate, as well as two options for cooling the magnetic components. In the first option, air is recirculated within the enclosure of the charger while exchanging heat with the heat sink through an assembly of aluminum fins and heat pipes. In the second option, the magnetics are submerged in thermal potting epoxy that exchanges heat to the heat sink through an assembly of heat pipes. Simulations show that adding thermal vias below the MOSFET's drain and attaching a heat sink on the other side of the PCB is the most effective method to maintain their temperature. In-plane conduction methods using copper PCB traces or even the MOSFET's drain impose much higher thermal resistance. Simulations also showed that the potting magnetics was better at maintaining temperatures and this was validated experimentally.