Dual Output Regulating Rectifier for an Implantable Neural Interface

Abstract

This paper presents the design of a power management circuit consisting of a dual output regulating rectifier configuration featuring pulse width modulation (PWM) and pulse frequency modulation (PFM) to control the regulated output of 1.8 V, and 3.3 V from a single input ac voltage. The PFM control feedback consists of feedback-driven regulation to adjust the driving frequency of the power transistors through the buffers in the active rectifier. The PWM mode control provides a feedback loop to accurately adjust the conduction duration. The design also includes an adiabatic charge pump (CP) to power stimulators in an implantable neural interface. The adiabatic CP consists of latch up and power saving topologies to enhance its energy efficiency. Simulation results show that the dual regulating rectifier has a voltage conversion efficiency 94.3% with an ac input magnitude of 3.5 Vp. The power transfer efficiency of the regulated 3.3 V output voltage is 82.3%. The dual output regulating rectifier topology is suitable for multi-functional implantable devices. The adiabatic CP has an overall efficiency of 92.9% with an overall on-chip capacitance of 60 pF. The circuit was designed in a 180-nm CMOS technology.

Demystifying Regulating Active Rectifiers for Energy Harvesting Systems: A Tutorial Assisted by Verilog-A Models

“…The one-stage regulation was adopted in several works among the state-of-the-art of EH PMUs that work under resonance conditions [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26]. The selfregulating rectifier solution allows avoiding the use of the post-regulation stage and, as a consequence, increasing the PCE of the entire PMU.…”

“…[18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32]. Battery charging via WPT is an attractive solution because it can deliver a wide range of power and helps the devices to be water-/dust-proof.…”

“…Battery charging via WPT is an attractive solution because it can deliver a wide range of power and helps the devices to be water-/dust-proof. Moreover, WPT enables battery-less IMDs, thus avoiding the toxicity of wires, reducing the implant dimensions, and increasing the longterm operation of the device [1], [2], [3], [4], [6], [8], [9], [10], [11], [16], [17], [20], [21], [25], [29], [30], [31], [32].…”

“…Therefore, the regulating active rectifier (RAR) scheme depicted in Fig. 2 has been introduced in literature, where, thanks to an additional feedback control loop, the regulation of the output voltage is included in the AR to achieve higher power conversion efficiency while reducing the chip area [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26]. Although exiled from the proposed topic, is worth to mention that the regulation of the output voltage can be achieved also at the TX level of the WPT [37], [38], [39], [41], [43].…”