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Power Integrations has launched Capzero, two-terminal, automatic X capacitor discharge ICs that eliminate power losses while allowing power supplies to comply with safety standards.

X capacitors are typically positioned across a power supply’s input terminals to filter differential EMI noise.

Alone, these components could present a safety hazard because they can store unsafe levels of high-voltage energy for long periods of time after the AC is disconnected.

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 230V AC.

When the AC voltage is disconnected, Capzero automatically and safely discharges the X capacitor by closing the circuit through the bleed resistors and directing the energy away from the exposed AC plug.

This approach provides engineers with total flexibility in their choice of the X capacitor used to optimise differential-mode EMI filtering without worrying about the effect of the required bleed resistors on system no-load and standby power budget.

The two-terminal design meets international safety standards for all open and short-circuit fault tests, allowing Capzero to be used before or after the system input fuse.

Power Integrations

Power Integrations is the leading supplier of high-voltage integrated circuits used in energy-efficient power conversion. The company’s innovative technology enables compact, energy-efficient power supplies in a wide range of electronic products, in AC-DC, DC-DC and LED lighting applications. Since its introduction in 1998, Power Integrations’ EcoSmartä energy-efficiency technology has saved an estimated $4.5 billion of standby energy waste and prevented millions of tons of CO2 emissions. The company’s Green Room web site provides a wealth of information about “energy vampires” and the issue of standby energy waste, along with a comprehensive guide to energy-efficiency standards around the world. Reflecting the environmental benefits of EcoSmart technology, Power Integrations is included in clean-technology stock indices sponsored by the Cleantech Group (Amex: CTIUS) and Clean Edge (Nasdaq: CELS).

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