Effect of class E power amplifier loading network on output power and efficiency of inductive powering system for implantable medical devices

Class E power amplifier is a prominent solution for driving transmitting coil in wireless inductive energy transfer systems. Proper tuning of this amplifier ensures zero voltage switching of the switching transistor and, therefore, leading to highly efficient power amplification, in theory reaching 100%. However, specifics of wireless powering, namely, existing misalignments of transmitting and receiving coils must be considered when designing inductive energy transfer systems with class E amplifier. In this work effect of residual reactance and series capactitance in loading network of the amplifier on output power, end-to-end energy transfer efficiency and switching losses are examined. It is shown that only output power are affected by the variation of the reactance. Class E loading network reactance only affects output power and have negligibly small effect on the power losses and efficiency. Additionally, estimation of number of turns and radii of the receiving coil effect on inductive energy transfer system parameters is demonstrated.