Abstract

This article presents a single-input–dual-output (SIDO) wireless power transfer (WPT) system that maintains high link efficiency across both heavy and light load conditions. Conventional SIDO architectures employ a fixed matching network, which leads to significant efficiency degradation when the load changes. To address this limitation, the proposed system classifies the two outputs into heavy-load and light-load domains and employs dedicated matching networks optimized for each operating condition, thereby maximizing link efficiency during charging of either load. To minimize the power overhead of mode switching while enabling single-stage AC–DC regulation, a charging-phase controller, a full/half-window mode controller, and an adaptive window generator are employed. Furthermore, an active rectifier with a slowdown unit cell (SUC)-based on/off controller (SOOC) is proposed to improve power conversion efficiency (PCE). In addition, an early turn-on switching (ETS) is implemented to achieve higher PCE compared to conventional zero-voltage switching (ZVS). Fabricated in a 0.18- μ m BCD process, the system is implemented as two chips, a standalone rectifier for accurate PCE measurement and a SIDO integrating the same rectifier. The SIDO demonstrates stable full/half-window operation without multiple pulsing. Measured link efficiency reaches 94.4% at 3mA and 92.7% at 30mA at a coupling coefficient k = 0.2, confirming the effectiveness of the load-optimized matching. The rectifier achieves 94.5% peak PCE and maintains above 92.3% PCE across a 2.5–5.0V input range. 

A new wireless charging technology promises to enhance the safety and longevity of implantable medical devices, such as pacemakers and neural stimulators. Led by Professor Franklin Bien of the Department of Electrical Engineering, the research team developed a system that employs load-specific matching networks and adaptive control to optimize power delivery.

Implantable devices often incorporate circuits with varying power demands—high-current circuits for stimulation and low-current circuits for data processing. Traditional wireless chargers rely on fixed configurations, which can lead to inefficiencies and heat buildup, potentially damaging surrounding tissue. The new system detects changes in load and switches between dedicated matching networks tailored for high and low power conditions, thereby optimizing energy transfer.

Furthermore, the team improved the efficiency of the rectifier circuit that converts received alternating current (AC) into direct current (DC). By precisely controlling switching points during power conversion, they minimized energy loss and enhanced overall performance.

Experimental results demonstrated a link efficiency of 94.4% at a low load of 3mA and 92.7% at a high load of 30mA. The active rectifier achieved a peak power conversion efficiency of up to 94.5%, maintaining above 92% even as input voltage varied from 2.5V to 5V.

The research team anticipates that this technology will extend the operational lifespan of implantable devices, reducing the need for frequent surgical replacements and associated risks. It also holds promise for application in wearable electronics and compact Internet of Things (IoT) devices that require reliable, low-loss wireless power.

The findings of this research were published online in the IEEE Transactions on Very Large Scale Integration (VLSI) Systems on April 29, 2026. The study has been s upported by the Ministry of Science and ICT (MSIT) and the Institute for Information & Communications Technology Planning & Evaluation (IITP).

Journal Reference

Sungmin Shin, Seongbin Kwon, Geonwoo Baek,   et al ., “A Single-Input Dual-Output Wireless Power Transfer System With Load-Optimized Matching Network,”   IEEE TVLSI. , (2026).