180-nm CMOS Wideband Capacitor-Free Inductively Coupled Power Receiver and Charger

• Published in: IEEE journal of solid-state circuits 2013-11, Vol.48 (11), p.2839-2849
• Main Authors: Lazaro, Orlando, Rincon-Mora, Gabriel Alfonso
• Format: Article
• Language: English
• Subjects: Applied sciences; Batteries; Capacitors; Coils; Contactless charging; Design. Technologies. Operation analysis. Testing; Dielectric, amorphous and glass solid devices; Diodes; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Exact sciences and technology; inductive power transmission; inductively coupling; Integrated circuits; Logic gates; low-threshold rectifier; Magnetic resonance; Receivers; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Switches; wireless power transfer
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2013.2280053

Wireless microsystems like biomedical implants and embedded sensors derive energy from tiny in-package sources that, unfortunately, exhaust easily, which means that operational life is short. Periodically coupling power wirelessly is one way of replenishing onboard batteries, except that small receiver coils suffer from low coupling factors k C and induce low electromotive-force voltages. Today, receivers store and resonate incoming energy between the receiving coil and an off-chip capacitor until the voltage rises sufficiently high for a diode-bridge rectifier to steer power into a battery. The capacitor, however, requires board space and constrains the source to a particular frequency. The 180-nm CMOS power receiver presented in this paper removes the diode bridge, which establishes a minimum voltage below which the system cannot derive power, so that neither tuning nor a resonating capacitor is necessary. Experimental measurements show that the system draws power from 30-mV signals when k C is 0.0046 and coil separation is 11.35 mm, and this threshold voltage only changes 13.6 mV across 100-150 kHz, which is a 27.1% lower threshold voltage that is 36 × less sensitive than its resonating counterpart. The peak efficiency of the receiver when rectifying to 1.2 V is 82% at 224 μW and 125 kHz and average efficiency is 76% for 90-386-mV coil voltages.