High-voltage bias power supply circuits have a high-voltage battery as a power source in HEVs and EVs. As a high-voltage battery, 400V and 800V voltage batteries are generally the most common battery in EVs. The isolated bias supply connected to the high-voltage battery needs to support a wider input voltage range. The range of wide input voltage requirements for HV batteries is similar to the range of wide input voltage requirements for LV batteries for different SoC and load dump scenarios. Based on the SoC of the battery, a wider input voltage range must be supported. For example, the voltage ranges of 240V–450V are commonly considered for a 400V battery and 550V–950V are commonly considered for an 800V battery. However, this voltage range can be different depending on the OEM requirement.

Although the high-voltage battery can be used as a primary source for the isolated bias power supply, the battery is mostly used to provide redundancy. Flyback topology is usually selected for such a high and wide input voltage range from a technical perspective and with regard to potentially minimizing costs.