Class E Power Amplifier Design and Optimization for the Capacitive Coupled Wireless Power Transfer System in Biomedical Implants

Abstract

Abstract:The capacitive coupled wireless power transfer (CCWPT) operating at megahertz (MHz) frequency is broadly considered as the promising solution for low power biomedical implants. The class E power amplifier is attractive in MHz range wireless power transfer (WPT) applications due to zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS) properties. The existing design of class E amplifier is investigated only for inductive resonant coupled (IRC) WPT systems; the modelling and optimization of the class E amplifier for CCWPT systems are not deliberated with load variation. Meanwhile, the variations in the coupling distance and load are common in real time applications, which could reduce the power amplifier (PA) efficiency. The purpose of this paper is to model and optimize the class E amplifier for CCWPT systems used in MHz range applications. The analytical model of PA parameters and efficiency are derived to determine the optimal operating conditions. Also, an inductive-capacitive-inductive (LCL) impedance matching network is designed for the robust operation of the PA, which improves the efficiency and maintains required impedance compression. The maximum efficiency of the proposed design reached up to 96.34% at 13.56 MHz and the experimental results are closely matched with the simulation.

Wireless Power Transfer Techniques for Implantable Medical Devices: A Review

“…An inductance-capacitance-inductance (LCL) impedance matching network (L 1 , L 2 and C) is also used to improve the PA efficiency under the variable load condition. In [59], a maximum PA efficiency of 96.34% was claimed for 13.56 MHz operating frequency. The primary design concern of the proposed system is the power consumption of the TPS28226 driver at higher frequencies.…”

“…A description of NRCC-specific RX power circuitry, including rectifier and regulator, is rare in the literature. In [59], a nominal condition-based class-E power amplifier (PA) is proposed for NRCC presenting a load resistance RL, as shown in Figure 3. The class-E power amplifier (PA) is designed with a CSD13380F3 N-channel MOSFET switch with a TPS28226 high-frequency driver.…”

Scaling-Factor and Design Guidelines for Shielded-Capacitive Power Transfer

“…Four parts of the circuit model comprise a WPT system with a capacitive coupling interface. A switch network can be implemented by a single-ended Class-E power amplifier, half-bridge, or full-bridge inverter system [27][28][29][30]. A 50 Ω coaxial cable is used in the proposed system, and a balanced-to-unbalanced (Balun) transformer is coupled to the resonant inductors, providing a balanced condition of the voltage waveform and a stable ground reference to the coupling system [31].…”

Preliminary study of 50 W Class-E GaN FET amplifier for 6.78 MHz capacitive wireless power transfer

“…Two couples of metal plate work as a capacitive interface between the primary and the secondary side. Several researches related to an implementation of the CPT have been conducted, such as biomedical sensor and implantable devices to a living object [10] [11], drone application [12] [13], and electric vehicle charging system [14] [15].…”