Design of 40.68 MHz Single-Stage WPT Receiver Using 2X/0X R ³ Rectifier for Biomedical Implants

A 40.68 MHz single-stage 2X/0X reconfigurable resonant regulating <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{R}^{3})$</tex> rectifier is proposed for improving the power conversion efficiency (PCE) of a wireless power transfer (WPT) receiver. AC to DC rectification and voltage regulation are achieved in one stage using only two power MOS transistors. AC to DC rectification is realized by a full-wave rectifier with an embedded voltage-doubler consisting of only two active diodes, with one using a PMOS and the other an NMOS power transistor. Turn-on delay, reverse current, and multiple-pulsing are eliminated using low-power digital techniques. Mode-switching for voltage regulation is realized through pulse width modulation (PWM) control, and Type-II compensation is used to achieve fast transient response. The proposed design is implemented with a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.13 \mu \mathrm{m}$</tex> CMOS process. The output voltage is regulated at 1.2 V. The measured PCE of the single-stage receiver reaches 90.7%. The measured undershoot and overshoot are lower than 95 mV, and the settling time is less than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$25 \mu \mathrm{s}$</tex> when the load switches between 1.2 mA and 12 mA.