An Adaptive Reconfigurable Active Voltage Doubler/Rectifier for Extended-Range Inductive Power Transmission

We present an adaptive reconfigurable active voltage doubler (VD)/rectifier (REC) (VD/REC) in standard CMOS, which can adaptively change its topology to either a VD or a REC by sensing the output voltage, leading to more robust inductive power transmission over an extended range. Both active VD and REC modes provide much lower dropout voltage and far better power conversion efficiency (PCE) compared to their passive counterparts by adopting offset-controlled high-speed comparators that drive the rectifying switches at proper times in the high-frequency band. We have fabricated the active VD/REC in a 0.5- $\mu\hbox {m}$ 3-metal 2-poly CMOS process, occupying 0.585 $\hbox {mm}^{2}$ of chip area. In an exemplar setup, VD/REC extended the power transmission range by 33 $%$ (from 6 to 8 cm) in relative coil distance and 41.5 $%$ (from 53 $^{\circ}$ to 75 $^{\circ}$ ) in relative coil orientation compared to using the REC alone. While providing 3.1-V dc output across a 500- $\Omega$ load from 2.15- (VD) and 3.7-V (REC) peak ac inputs at 13.56 MHz, VD/REC achieved measured PCEs of 70 $%$ and 77 $%$ , respectively.