Self-Tuning Power Supply for Inductive Charging

Inductive power transfer (IPT) systems for electric vehicle (EV) charging often have to operate under a wide range of coupling factors and loads, potentially mistuning the primary power supply. This is especially a problem in dynamic applications where the vehicles are moving. This paper investigates the design of a self-tuning power supply by utilizing a switchable bank of capacitors with a push-pull tuning topology. The proposed power supply is able to handle operation under a wide range of coupling factors and loading conditions while achieving ZVS operation at a fixed frequency. A mathematical model is developed to model the system and an experimental system is built to test the design. The experimental system is able to deliver a constant 1 kW over a coupling factor range of 0.1-0.33. A detection circuit to monitor the state of tuning of the power supply is presented along with a control scheme to maintain optimal tuning.