Wireless Charging System Using Resonant Inductor in Class E Power Amplifier for Electronics and Sensors

Abstract

This study aims to solve a problem that exists with impedance matching networks in terms of extra cost and power loss of electronic components in a four-coil wireless power transfer (WPT) system using class E power amplifier as power supply, which is not conducive to the improvement of system efficiency and output power. A design method of sharing the resonant inductor in class E power amplifier and the excitation coil in the four-coil WPT system is proposed. This method comprehensively considers the output power and transfer efficiency of the system, the number of coil turns, coil size and many other factors. Compared with the traditional four-coil system using a class E power amplifier as a power supply, the proposed method simplified the system structure by leaving out a resonant inductor and load matching circuit, which can reduce the power loss of system and improve efficiency. Moreover, the precisely tuning of resonant inductor was not necessary, which improved the stability of the system. The correctness and feasibility of the parameter design method were verified by experiments. The experimental results showed that the output power of the system was increased by 18.7%, the efficiency was increased by 11%, and the transmission distance was up to 0.7 m, which is suitable for wireless power supply of electronics and sensors.

An Off-Nominal Class E Amplifier—Design Oriented Analysis

“…The high efficiency of the Class E PA has inspired its use in many other applications, such as: industrial induction heaters, dc/dc converters, plasma generators, wireless power transmission systems (WPT) supplying energy to RFID tags, medical implants and endoscopic capsules, etc. [4][5][6][7][8][9][10][11]. Such a wide range of applications often requires Class E amplifiers to be optimized to operate efficiently in the given conditions.…”

Derivation of the Resonance Mechanism for Wireless Power Transfer Using Class-E Amplifier

“…Moreover, technical considerations and future trends for EV IPT have also been introduced such as enhancing the performance in terms of efficiency, power density, scalability, and reliability, adopting soft-switching technology, using wide bandgap device technology, and applying high-performance control schemes. Among the WPT topologies, the class-E power amplifier (PA) [3,4], which is simple yet highly efficient with high operating frequencies, is critical for various devices, such as drones [5], battery chargers [6], and electronics and sensors [7,8]. As to human physiology, the resonant frequency in the range of 3.8 to 6 MHz is regarded as a safe electromagnetic frequency for the human body to be exposed to, according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Institute of Electrical and Electronics Engineers (IEEE) standards [9].…”