A Time-Interleaved Resonant Voltage Mode Wireless Power Receiver with Delay-Based Tracking Loops for Implantable Medical Devices

This article proposes a resonant voltage mode receiver (RVM-Rx) as a new topology of a wireless power receiver for battery charging. With a resonant capacitor interleaving scheme, an LC tank in the receiver can always be configured and isolated from the output, leading to optimal power transfer regardless of the operation phase. Thus, the power transfer efficiency is not sensitive to load conditions, such as battery voltage variation. In the RVM-Rx, a diode-based voltage peak time detection (VPTD) technique enables the system operation at a high resonant frequency. Also, a delay-based control scheme with a minimum diode time tracking loop (MDTL) and an optimum duty tracking loop (ODTL) leads to efficient power conversion by adaptively adjusting the operation state. The RVM-Rx prototype in a 0.18 μm CMOS process can operate at a high resonant frequency of 13.56 MHz with a small R_X coil (7 mm × 7 mm), while achieving a maximum receiver power efficiency of 67.8% for battery charging.