POWER INTEGRATIONS: CAPZero eliminates input power losses in AC/DC Designs


AC/DC power supplies usually need X-Capacitors in the input to comply with safety standards and to filter EMI noise.

X capacitors are typically positioned across a power supply's input terminal to filter differential EMI noise. To meet safety standards, resistors are commonly used in parallel with the X capacitor and across the AC line to provide a discharge path. However, these discharge resistors produce a constant power loss while the AC is connected and are a significant contributor to no-load and standby input power consumption.

CAPZero acts as a smart high-voltage switch when placed in series with discharge resistors. When AC voltage is applied, CAPZero blocks current flow in the X capacitor safety discharge resistors, reducing the power wasted in these components to zero at 230 VAC. When the AC voltage is disconnected, CAPZero automatically and safely discharges the X capacitor through the bleed resistors and directing the energy away from the exposed AC plug. By using CAPZero the input filters can be designed flexible according to safety requirements while eliminating the usual losses.

With use of CAPZero in series with the input-resistors no-load consumption can be easily reduced by >100mW.

Details can be found here.

For further information please contact Thomas Berner.

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