DC analysis technique for inductive power transfer pick-ups

Abstract

Inductively coupled power transfer (ICPT) systems are now being used in applications where their efficiency and stability are critically important. In this paper, an ICPT pick-up is analyzed under conditions where the pick-up tuning is assumed to be essentially perfect, and all diodes are assumed to have continuous current flow in them. The analysis proceeds by replacing the existing parallel resonant tank and rectifier circuit with a DC source and transformer equivalent, thereby reducing the complexity of the circuit, and eliminating the diodes. The DC equivalent is shown to have the same energy storage and power capability as the original circuit and is accurate under all loadings for both transient and steady-state conditions. With this simplification, analytic transfer functions for the pick-up with respect to its excitation current and its control switch duty cycle are developed. The ICPT system model is shown to have multiple poles, with complex zeroes on the right half plane. The model allows a sophisticated controller to be designed to give the ICPT system the required stability at high efficiency.