CAP003DG-TL [Power Integrations]

When AC voltage is applied, CAPZero™ blocks current flow in the X capacitor safety discharge resistors, reducing the power loss to less than 5 mW, or essentially zero1 at 230 VAC. When AC voltage is disconnected, CAPZero automatically discharges the X capacitor by connecting the series discharge resistors. This operation allows total flexibility in the choice of the X capacitor to optimize differential mode EMI filtering and reduce inductor costs, with no change in power consumption. Designing with CAPZero is simply a matter of selecting the appropriate CAPZero device and external resistor values for the X capacitor value being used. This design choice will provide a worst case RC time constant, when the AC supply is disconnected, of less than 1 second as required by international safety standards.