Inductance cancellation in RF resonant power converters

Abstract

Parasitic inductance cancellation is employed in order to operate a resonant power inverter at 27.12 MHz using a TO-220 through-hole package. A Cauer-type 1 LC network permits the coupling of inductors to achieve cancellation of multiple parasitic inductances and reduces semiconductor device stress in the same way as the Φ 2 inverter topology. The elimination of parasitic inductances allows for system cost reduction, increased power handling, and/or relaxation of PCB layout constraints. The inductance cancellation technique is demonstrated through two prototypes (based upon the same silicon MOSFET die) providing 60 W of RF power to a 50 Ω load from a 48 V DC input: one prototype utilizes a small surface-mount package, and another a larger through-hole TO-220 package. (Without inductance cancellation, the lead inductance of the TO-220 is too large and cannot be used in a 27.12 MHz resonant application.) Inductance cancellation was verified through comparing impedances, operating waveforms, and efficiencies between the prototypes with different MOSFET packages.