27.3 A 90.8%-Efficiency SIMO Resonant Regulating Rectifier Generating 3 Outputs in a Half Cycle with Distributed Multi-Phase Control for Wirelessly-Powered Implantable Devices

Wirelessly-powered implantable medical devices (IMDs) have recently embraced a 1-stage resonant regulating rectifier (R3) to enhance power conversion efficiency (PCE), replacing the prior 2-stage structure comprising an ac-dc rectifier followed by a regulator. Furthermore, to address the specific power requirements of IMDs that need multiple supplies, recent works have proposed dual-output R3 topologies that can provide two separate output voltages [1-5], as illustrated in Fig. 27.3.1 (top). The first technique involves segmenting several cycles into two groups, each responsible for generating either regulated high voltage or low voltage [3]. When generating low voltage, the power pass PMOS transistor operates with a low VSG (VINN - VSG leading to an increase in on-resistance (RON) and the possibility of entering sub-threshold mode. This, in turn, negatively affects PCE and limits the output voltage range. Additionally, as the pulse frequency increases, the output ripple of the secondary regulated low voltage worsens. To mitigate the issue of high output ripple, another approach separates the positive and negative cycles to generate two distinct regulated outputs [4]. Since it employs the half-wave rectification for each output instead of full-wave rectification, this still suffers from low power delivered to the load (PDL) and high output ripple. Similarly, dual-output voltage doubler still has these issues and encounters a maximum difference between the two output voltages at VIN,peak [5].