Isolated bias supply provides power to the different gate-driver circuits in HEVs and EVs. There are different topologies to design an isolated bias power supply. The most commonly used topologies are flyback, push-pull, LLC-resonant, and integrated transformer modules. Each topology provides specific advantages but at the same time has trade-offs and challenges. The choice of the topology depends largely on the overall architecture of the isolated bias power supply.

Isolated bias power supplies take power either from the low-voltage (LV) battery or from the high-voltage battery of the HEV, EV. Based on the power source, the isolated bias power supplies can be divided in two groups: low-voltage isolated bias power supplies and high-voltage isolated bias power supplies. The isolated bias supply circuit can be directly connected to the battery or connected to the battery using the pre-regulators. The pre-regulators are needed depending on the wide input voltage range capability of the device. Although, LV batteries are common as a power source for isolated bias power supplies, often both LV and HV batteries are used to provide redundancy in the system. A redundant power supply can lead to achieve higher functional safety of overall system. Figure 1-1 shows a traction inverter block diagram.

Figure 1-1 Traction Inverter Block Diagram