PFC inductor selection made easy by “PL product”

In recent years, power factor correction (PFC) has been gaining momentum. While the U.S. does not have any existing regulatory requirements, in Europe, the employment of PFC in power supplies is necessary to meet the European EN61000-3-2 regulatory standard. As the U.S. government continues to emphasize energy conservation and efficiency, speculation among power supply designers is such that the domestic requirement for PFC is not far from the horizon. Inductors play a critical role in the boost pre-regulator for PFC. Faced with today´s challenge of balancing power requirements, switching frequency, and efficiencies, circuit designers find it necessary to understand a PFC inductor´s operating characteristics and its effect on the PFC circuit as design criteria changes. This has been difficult due to the lack of an effective way for magnetic manufactures to relate the performance of PFC inductors. To address this inadequacy, a figure of merit known as the PL product has been developed to better characterize PFC inductors over a range of output power. Based on desired circuit operating parameters, designers can calculate the PL product required for their application and correlate it to the PL curves of various PFC inductors. This will not only simplify the design process by making inductor selection easier, but also allow circuit and PFC inductor characteristics to be realized under various operating conditions. In order to demonstrate and validate the applicability of PL product, a 400 Watt PFC inductor is tested in a continuous conduction mode (CCM) PFC circuit with output power ranging from 325 to 475 Watt. Measured data of temperature rise and ripple percentage are compared and verified against those calculated based on the PL product at 25 Watt increments.