The DC supply is required only in the active?single?switch topology. A higher DC voltage generally improves the accuracy of detection because this type of voltage reduces the relative impact of the voltage of the AC line on the measurement. A boost converter is commonly employed to obtain this higher voltage from the low?voltage battery of the vehicle (typically 12V, with a range of 8V–16V).

The TPS61170?Q1 boost converter offered by TI operates at 1.2MHz, can deliver up to 38V, and maintains good efficiency even at light loads, making the device a potentially cost?effective way to generate a stable VDC for the insulation monitoring circuit.

Another alternative is to add an extra winding to the transformer that supplies isolated bias power for the gate drivers. While this alternative eliminates the need for a separate boost converter, this option complicates the transformer design and makes voltage regulation more difficult, especially under light?load conditions.