32.1 A 13.56MHz Current-Mode Wireless Power and Data Receiver with Efficient Power Extracting Controller and Energy-Shift Keying Technique for Loosely Coupled Implantable Devices

To supply power to implantable systems, wireless power transfer (WPT) is an attractive solution. There are two types of WPT receivers (RXs), voltage-mode (VM) RX [1], [2] and current-mode (CM) RX [3], [4]. The VM-RX is suitable when the coupling coefficient $(\mathrm{k}_{12})$ between the transceiver (TX) and the RX coils is sufficiently high. However, in many practical cases, the $\mathrm{k}_{12}$ is low because of a considerably small implanted RX coil and/or the relatively long distance between the TX and RX coils, as shown in Fig. 32.1.1 (top). In this case, the CM-RX is more suitable. To receive a lower power from the TX, the CM-RX stores power in its LC tank by resonance and transfers the energy to a battery when the energy reaches the optimal level.