A Dual-Output Single-Stage Regulating Rectifier With PWM and Dual-Mode PFM Control for Wireless Powering of Biomedical Implants
Reza Erfani, Fatemeh Marefat, Pedram Mohseni
Abstract
This paper presents a reconfigurable, dual-output, regulating rectifier featuring pulse width modulation (PWM) and dual-mode pulse frequency modulation (PFM) control schemes for single-stage ac-to-dc conversion to provide two independently regulated supply voltages (each in 1.5-3 V) from an input ac voltage. The dual-mode PFM controllers feature event-driven regulation as well as frequency division. The former incorporates stable, fast, digital feedback loops to adaptively adjust the driving frequency of four power transistors, MP1~4, based on the desired output power level to perform voltage regulation and deliver fast, transient, load currents. The latter sets the driving frequency of MP1~4 to a user-defined fraction (1/1 ~ 1/32) of the input frequency (1-10 MHz). The PWM controllers incorporate stable, analog, feedback loops to accurately adjust the conduction duration of MP1~4 for voltage regulation and can be combined with PFM frequency division for an extended operation dynamic range. Fabricated in 0.18 μm 1P/6M CMOS, the regulating rectifier features power conversion efficiency (PCE) of >83.8% at 2 and 5 MHz, with the first output channel delivering ~1 mW from VDD of 1.5 V and the second output channel delivering variable power from VDDH of 2.5 V to a load in the range of 0.1 to 1 kΩ. Peak PCE values of 90.75% (2 MHz, 100 Ω) and 90.7% (5 MHz, 200 Ω) are also measured. The regulating rectifier is suitable for the emerging modality of capacitive wireless power transfer to biomedical implants.