A 120 W Class-E Power Module with an Adaptive Power Combiner for a 6.78 MHz Wireless Power Transfer System

Abstract

In this article, a highly efficient power module is presented with two class-E power amplifiers and an adaptive power combiner for transmitting output powers >100 W at 6.78 MHz in a wireless power transfer system. The losses caused by the combiners and interstage matching circuits or mismatching between the amplifier, and the combiners can significantly reduce the overall efficiency of the power module. To achieve an efficient combination of the output amplifier signals, the adaptive power combiner is proposed based on the consideration of the optimum load impedance characteristics of the power amplifiers. The input impedance of the combiner is designed using series capacitors and resistors between the two input ports of the combiner and the two output signals of the class-E amplifiers at the optimum load condition. The output performances of the proposed module can decrease based on the component mismatch between the two power amplifiers. The proposed power module was implemented on an FR4 PCB, with a 15 mm metal heat sink, and demonstrated an output power of 123.3 W, a power-added efficiency of 85.7%, and a power gain of 25.6 dB at 6.78 MHz. The second harmonic suppression of the module was 37 dBc.

2.45 GHz Active Isolator based on asymmetric coupler

“…A LDMOS BLC2425M10 240 transistor manufactured by Ampleon was used in the amplifier. The high design accuracy of the amplifier and asymmetric coupler using EM-circuit cosimulation at the operating frequency was verified in the previous studies [14,21]. Figure 4 shows the Sparameter results when the amplifier is biased at the drain voltage of 13.5 V and gate voltage of 1.85 V. The input and output return losses at the operating frequency of 2.45 GHz are simulated to be 10.3 and 30 dB, respectively.…”

“…The EM-circuit co-simulation method is a useful method and is commonly used to show accurate circuit characteristics and performances by considering the exact characteristics of RF active and passive devices, both parasitic components and coupling effects in the implementation based on electromagnetic wave analysis [17][18][19][20][21][22]. Figure 3 presents a layout design with a dimension of 87 × 94 mm 2 for EM-circuit co-simulation using Keysight ADS Momentum.…”

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

“…Advance research and technology implemented the Class-E amplifier for wireless power transfer (WPT) application, from a low frequency [3] to a high frequency field [4] includes a charging applications [5] [6]. Furthermore, research studies related to adaptive and controllable power combiner were also offered [7] [8]. It is difficult to change the regeneration frequency due to the limitation of the ISM band for MHz WPT.…”