Precision design approach results in high performance PFC inductor for International Rectifier's demo board.

Authored By: David Anderson, Chief Engineer – Precision, Inc.

When International Rectifier wanted a high performance power factor correction (PFC) inductor that showed well on their IR1150 reference design, they turned to Precision, Inc. The two companies have successfully collaborated on a number of applications over the years. Precision has proven to be very responsive in designing and building the ideal magnetics for specific applications on a timely basis and has developed devices for use in many other International Rectifier power conversion designs.

Devices like PFCs are boost circuits that bring current in phase with voltage, to create acceptable power factor front ends for power supplies. The role of the inductor is to store energy, and reduce ripple current.

Design Requirements
International Rectifier wanted to highlight the new controller chip for their IRAC1150-300 watt demo board application. Their requirements for the new PFC inductor included: A high-performance core with low losses to minimize temperature rise, minimize audible noise from magnetostriction, maximize self resonant frequency (SRF) and provide stable inductance over the current range. The single-layer winding and compact size make a very good presentation on the board.

The Precision (and IR) Recommendation

Precision worked with International Rectifier to balance the trade-offs to develop the Inductor, Part #019-4120-00, a very high-performance inductor, met all of the 300 Watt circuit requirements of the IR 1150 Demo Board. It is capable of 100 kHz switching frequency, a  peak current of 6.2A  and a continuous RMS current of 3.8A. The low core loss and SRF were achieved by selecting the right core material and winding configuration.

This design also yields low audible noise and a minimal temperature rise.During the process some options were also considered, including a number of cost and performance variations. One of these includes a bias winding on the PFC choke to supply power for the PFC control circuitry.