A Dual-Mode Highly Efficient Class-E Stimulator Controlled by a Low-Q Class-E Power Amplifier Through Duty Cycle

Abstract

This paper presents the design flow of two high-efficiency class-E amplifiers for the implantable electrical stimulation system. The implantable stimulator is a high-Q class-E driver that delivers a sine-wave pulsed radiofrequency (PRF) stimulation, which was verified to have a superior efficacy in pain relief to a square wave. The proposed duty-cycle-controlled class-E PRF driver designed with a high-Q factor has two operational modes that are able to achieve 100% DC-AC conversion, and involves only one switched series inductor and an unchanged parallel capacitor. The measured output amplitude under low-voltage (LV) mode using a 22% duty cycle was 0.98 V with 91% efficiency, and under high-voltage (HV) mode using a 47% duty cycle was 2.95 V with 92% efficiency. These modes were inductively controlled by a duty-cycle detector, which can detect the duty-cycle modulated signal generated from the external complementary low-Q class-E power amplifier (PA). The design methodology of the low-Q inductive interface for a non-50% duty cycle is presented. The experimental results exhibits that the 1.5-V PA that consumes DC power of 14.21 mW was able to deliver a 2.9-V sine wave to a 500 Ω load. The optimal 60% drain efficiency of the system from the PA to the load was obtained at a 10-mm coupling distance.

A power‐efficient current‐mode neural/muscular stimulator design for peripheral nerve prosthesis

“…in which V load (t) is the voltage over the load, V stim (t) is the stimulation voltage, and I o (t) is the resultant current in the output stage, respectively. It is known that the voltage-mode stimulation provides the highest PE 19,20 because ideally, V load equals to V stim at the output stage of the stimulator. Nonetheless, its uncontrolled or inaccurate controlled current and charge injection makes the voltage-mode stimulation inappropriate for clinical applications.…”