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This paper presents a wide input range active rectifier using a bipolar-CMOS-DMOS (BCD) process with a high voltage conversion ratio (VCR) and high power conversion efficiency (PCE). The proposed rectifier ensures safe and robust operation under large input voltage variations, which can be caused by changes in the magnetic coupling or loading conditions. It supports an input voltage range 3–12 V with the adaptive delay-compensated active operation of the power switches. An active signal clamper and voltage-time hybrid gate control circuit with two compensation loops was proposed for the optimal gate transition of low-side NMOS switches. For high-side PMOS switches, a fully integrated low-power-consuming high-side driver is proposed to replace the conventional high-side gate driving structure. The proposed active rectifier was fabricated through a TSMC $0.18\mu \text{m}$ BCD process. The measurement results show that the proposed rectifier achieves stable and well-delay-compensated active operation, resulting in a high VCR and PCE with a wide output power range from 4.5 to 288 mW. Peak VCR and PCE of 96.8% and 93.7%, respectively, were achieved.

This study reports a miniaturised discontinuous conduction mode (DCM) variable on-time (VOT) buck converter providing an output of 1.8 V in the input range of 3–12 V to support applications with large wireless coupling. Conventionally, an additional large capacitor has been used as a bootstrap capacitor to drive the high-side switch of buck converters, which prevents minimisation. In this study, a standalone momentary power consumption level shifter is proposed to remove the additional bootstrap capacitor and increase the power conversion efficiency (PCE) in the buck converter. A Zener diode is utilised to reduce the power consumption of the level shifter. In addition, a dead-time-based off-time calibration circuit is proposed to further increase the PCE by reducing the low-side conduction loss. The proposed circuit is fabricated with a TSMC 0.18-µm BCD process, and the core circuit occupies an active area of 0.68 mm2 with two external components. It provides output currents in the range of 20 µA to 3 mA with a maximum switching frequency of 750 kHz. The maximum efficiency of the converter below 5 mW is 80.2%.

A key limitation inherent in wireless power transmission (WPT) systems using coils is a high sensitivity to the alignment between the transmitting and receiving coils. Moreover, the physical separation of the transmitting and receiving coils or any metallic barrier between them can notably reduce the efficiency. To overcome these limitations, a practical WPT system that is insensitive to the alignment between coils and metallic obstacles is proposed. It uses a printed circuit board-type antenna fabricated by reducing the structure of an antenna used in previous research and is designed to resonate at the target frequency through impedance matching. The proposed system uses surface-guided-mode resonance at the metal–air interface and transmits uniform power within 1.3 m. In addition, the proposed system satisfies the electromagnetic field international standard that is the electric field and magnetic field reference values are 152.5 V/m and 0.4 A/m, respectively at 4 MHz.

In this paper, a fully integrated active rectifier with triple feedback loops is proposed to enhance power conversion efficiency (PCE) over a wide loading range by calibrating both the gate transition timing and power switch size. The on- and off-transitions of the power switches are calibrated using a hybrid delay-based gate control circuit (HDGCC) with hybrid feedback loops. Conventional active rectifiers that only focused on calibrating the gate transition timing of a NMOS power switch with a fixed power switch size exhibit a low PCE when the loading condition deviates from the predetermined range. Thus, an automatic size selector based on a third feedback loop is proposed, which changes the power switch size based on the loading condition and ensures a stable operation of the hybrid loops by maintaining the voltage drop across the NMOS switches. An active rectifier was fabricated using the standard 0.18 μm CMOS process. The effectiveness and robustness of the two-dimensional calibration were verified through measurements under an AC input voltage ranging from 2.5 to 5.0 V and an output power ranging from 1.25 to 125 mW. The peak voltage conversion ratio and peak PCE were 97.6% and 95.0%, respectively, at RL = 500 Ω.

A decade ago, non-radiative wireless power transmission re-emerged as a promising alternative to deliver electrical power to devices where a physical wiring proved to be unfeasible. However, existing approaches are neither scalable nor efficient when multiple devices are involved, as they are restricted by factors like coupling and external environments. Zenneck waves are excited at interfaces, like surface plasmons and have the potential to deliver electrical power to devices placed on a conducting surface. Here, we demonstrate, efficient and long range delivery of electrical power by exciting nonradiative waves over metal surfaces to multiple loads. Our modeling and simulation using Maxwells equation with proper boundary conditions shows Zenneck type behavior for the excited waves and are in excellent agreement with experimental results. In conclusion, we physically realize a radically different power transfer system, based on a wave, whose existence has been fiercely debated for over a century., 16 pages, 4 figures. Article submitted to Nature Communications

We present a metasurface antenna comprising periodic arrangement of interconnected rectangular unit cells. The proposed antenna is designed to utilize evanescent mode resonance. The resonance is achieved by utilizing strong cavity mode oscillation, when the antenna is placed over a metallic surface. However, when the antenna is freely suspended in the air, in its natural state, the resonance is absent. At an optimized feed point, the antenna can be excited directly with a 50 ohm impedance line.

Using layers of mesh shaped and flat copper plate, this paper demonstrates single metal path power transfer system without return path through the surface of aluminum foil at 13.56MHz. Transceivers are isolated from the energy propagating medium but surface wave gets excited. This technology is free from co-alignment limitation between Tx and Rx, enabling free position of Rx with given metal plate environment. Around 20% power transfer efficiency was achieved with a LC matching network part.