A dual-mode highly efficient class-E stimulator controlled by a low-Q class-E power amplifier through duty cycle

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Power Electronics

Background:

• Implantable electrical stimulation systems require efficient power amplifiers.
• Sine-wave pulsed radiofrequency (PRF) stimulation shows superior efficacy for pain relief compared to square waves.
• Existing class-E amplifiers face challenges in achieving high efficiency across different voltage modes.

Purpose of the Study:

• To design and present two high-efficiency class-E amplifiers for implantable electrical stimulation.
• To enable sine-wave PRF stimulation for enhanced pain relief.
• To achieve high DC-AC conversion efficiency in both low-voltage and high-voltage modes.

Main Methods:

• Developed a duty-cycle-controlled class-E PRF driver with a high-Q factor.
• Implemented two operational modes (LV and HV) using a single switched series inductor and an unchanged parallel capacitor.
• Utilized a duty-cycle detector and a complementary low-Q class-E power amplifier (PA) for inductive control.
• Presented a design methodology for a low-Q inductive interface for non-50% duty cycles.

Main Results:

• Achieved 91% efficiency at 0.98 V output in LV mode (22% duty cycle).
• Achieved 92% efficiency at 2.95 V output in HV mode (47% duty cycle).
• A 1.5-V PA delivered 2.9-V sine wave to a 500 Ω load with 14.21 mW DC power consumption.
• Obtained optimal 60% drain efficiency at a 10-mm coupling distance.

Conclusions:

• The proposed duty-cycle-controlled class-E PRF driver effectively delivers high-efficiency sine-wave stimulation for implantable systems.
• The dual-mode operation and inductive control mechanism enable versatile and efficient power delivery.
• The design methodology facilitates the development of efficient inductive interfaces for non-conventional duty cycles in biomedical applications.