A 6.78 MHz Maximum Efficiency Tracking Active Rectifier with Load Modulation Control for Wireless Power Transfer to Implantable Medical Devices

This paper presents a novel integrated wireless power transfer receiver for implantable medical devices, including a load-modulation feedback loop and an active rectifier with maximum efficiency tracking technique. The feedback loop enables the control of the power delivered to the load by means of a frequency modulation of the receiver load, introducing an efficiency loss of only 1.64 %. The active rectifier maximizes the efficiency of the link through a second feedback calibration loop of the off-transition of the active diodes, showing a Voltage Conversion Ratio of 0.98 and a Power Conversion Efficiency between 0.86 and 0.91 for a wide range of load conditions. The chip was designed in the 180 nm BCD-on-SOI XFAB technology and evaluated with accurate electrical simulations and Monte Carlo runs.