In regular ICE vehicles additional loads were driven directly by the engine, either through belts or, for agricultural vehicles, a power takeoff shaft. These include the water and hydraulic pumps, air and A/C compressor, and alternator. In an EV cabin heating must be provided as waste heat from the engine is no longer available.
When moving to an electric vehicle, these loads must be powered electrically. Due to the high-power levels (kW’s) it is lower cost and more efficient to utilize the HV system voltage to do this.
Auxiliary HV DC-DC converters provide the low voltage supply rails from the, up to 950 V, HV system voltage for the control electronics driving each of these modules. In addition, there are other applications such as contactor control and on-board convenience inverters (for 120/240 VAC outlets) which are also powered from the HV system.
Both non-isolated buck and flyback and reinforced isolated flyback solutions from Power Integrations are ideal here, providing very low part count and small footprint solutions.