Posted on 01 October 2019

High Performance PFC Inductor

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Core with low losses to minimize temperature rise

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.

By David Anderson, Chief Engineer, Precision


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, to minimize audible noise from magnostriction, to maximize self resonant frequency (SRF), and to provide stable inductance over the operating current range. The single-layer winding and compact size make a very good presentation on the demo 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 highperformance inductor, met all of the 300 Watt circuit requirementsof the IR 1150 Demo Board. It is capable of 100 KHz switching frequency, a peak current of 6.2A and a continiuous RMS current 3.8A. The low core loss and high 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.

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Precision’s (and IR´s) Design Considerations

Key considerations include: inductance, peak current, operating frequency, ripple current, physical size, temperature rise, audible noise, and cost. The trade-off’s in design are driven by the priorities of the application, this effects proper core selection, wire and winding configuration.

Part of Precision’s design approach begins with listening to the customer and gaining a thorough understanding of their unique application needs. The approach continues with review of the design theory and device trade-offs, samples for design verification and a review of global manufacturing and delivery alternatives. The goal is to respond with solutions on a timely basis by clearly reviewing and understanding all key considerations.

A number of considerations are examined during Precisions’ design approach for PFC inductors:

1) Balanced Performance/Cost - Toroid Design Alternative. A lower performance core will provide inductance stability over the current range and achieve required inductance in the same physical package. This will increase the core loss and introduce the possibility of audible noise under high ripple current conditions.

2) Efficient Cost - Toroid Design Alternative. This design will produce low core loss with low temperature rise and good magnetostriction characteristics. Alternative core materials can yield a lower cost. A larger size may be needed to achieve the required inductance.

3) E-core Alternative: The variety of sizes and materials offer a wide range of form factors. Bobbin construction simplifies manufacturing and mounting to the PCB.

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A Family of New Products

Precision has PFC Inductors that are used with all popular PFC controllers. They are releasing products that encompass toroid and E-core configurations, as well as less expensive options for the IR controller. The new PFC inductor products work with a wide variety of power levels, as well as other PFC applications.

Precision has PFC inductors that are used on all popular PFC controllers. The company produces many custom PFC inductor designs for applications up to 4,000 Watts and beyond. They can provide a variety of performance and cost options for any PFC application, including lower cost/performance alternatives.

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.



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