A Family of IPT Battery Chargers With Small Clamp Coil for Configurable and Self-Sustained Battery Charging Profile

Abstract

To self-sustain the constant current (CC) output to constant voltage (CV) output transition for inductive power transfer (IPT) chargers, the clamp coil assisted IPT battery chargers are better than the existing solutions due to the merits of no additional switching components, sensors, and control circuits. However, the clamp coil of these IPT chargers is bulky and hard to design, as the mutual inductances between the clamp coil and the main coupler coils are significant to the output performances. To facilitate the small clamp coil in the transmitter, this paper proposes a family of IPT battery chargers with a proper secondorder compensation network on the secondary side. The output thresholds of the IPT charger with the proper compensation can be readily configured to cope with the desired charging profile, and the clamp coil can be designed very small to decrease the corresponding cost and size. In addition, the proposed threecoil IPT charger still features automatic and smooth CC-to-CV transition to eliminate wireless communication, near unity power factor to minimize voltage-ampere (VA) ratings, soft switching to improve transfer efficiency, and open-circuit protection during CC charging. An experimental prototype of a 48 V/2.5 A battery charger is built to verify the analysis.