Harmonic analysis of voltage-fed full-bridge converter for TET application

A Transcutaneous energy transfer (TET) system provides a new way to powering implantable biomedical devices without wires penetrating through the skin. The system implements high frequency (e.g. 180kHz) switching, so careful attention must be paid to design aspect of such a system to comply with EMC and safety requirements. This paper presents the harmonics analysis of a voltage-fed full-bridge TET system. A nonlinear model is established and analyzed by equivalent small parameter and stroboscopic mapping methods. Steady state analytical results show that at the zero current soft switching (ZCS) resonant frequency, the voltage-fed LCL type converter not only has least switch current distortion, but also can deliver much higher power compared to operating at conventional fixed nominal resonant frequency without achieving full ZCS. The research results obtained are very useful for EMI analysis, characterization and design of voltage-fed LCL type converters for TET applications.