High-Performance High-Power Inductor Design for High-Frequency Applications

Magnetic components significantly impact the performance and size of power electronic circuits. This is especially true at radio frequencies (RF) of many MHz and above. In the high-frequency (HF, 3-30 MHz) range, coreless (or “air-core”) inductors are conventionally used. These inductors have typical quality factors (Qs) of 200-500. However, their uncontrolled magnetic fields can induce electromagnetic interference (EMI) and eddy current losses in surrounding components, limiting system miniaturization. This makes them a major contributor to overall system loss and size. With recent advances in high-frequency magnetic materials, there is interest in design of cored inductors to achieve improved combinations of size and loss. This work investigates an approach to achieving high-power, high-frequency, high-Q cored inductors. The proposed design approach leverages high-frequency magnetic materials, core geometry, quasi-distributed gaps, and a copper shield to realize high-frequency inductors that emit little f lux outside their physical volume. Design guidelines for such inductors are introduced and experimentally verified with a 155 kVA, 570 nH inductor (Q = 1150) designed to operate at 13.56 MHz with a peak ac current of up to 80 Amps. A high-efficiency and compact back-to-back L-match is used to demonstrate the high-performance and self-shielding capability of this prototype inductor.