Digital Regulation of Wireless Power Transfer Systems Using an Embedded Lock-In Amplifier

Abstract

High-performance operation of inductive wireless power transfer (WPT) systems requires judicious tuning of the inverter connected to the transmission hardware for high-performance operation and reliability. In many applications, disturbances to both the coupling condition and the secondary-side load reshape the system dynamics, motivating the design of closed-loop regulation and impedance detection techniques. Although several analog methods have been presented, they require multiple additional components and are dependent upon fixed component values and operating frequency. In this article, a novel digital approach is presented for use in series–series compensated WPT systems. The proposed system extracts both the phase and the magnitude of the primary current in real time. Through closed-loop regulation, zero-voltage switching is sustained without additional compensation components, while the output current is controlled. By utilizing a digital framework, no additional analog components are required, improving system reliability and cost. The state identification method is self-tuning, providing robust suppression of switching noise even with a variable switching frequency. A computationally efficient construction ensures a fast converging measurement and enables high-frequency operation. Analysis, simulations, and experimental results are included to comprehensively verify these characteristics.