PLL-Based Readout Circuit for SiC-MOS Capacitor Hydrogen Sensors in Industrial Environments

Area of Science:

• Materials Science and Engineering
• Electrical Engineering and Electronics
• Chemical Sensing Technologies

Background:

• Industrial gas sensors necessitate readout circuits with high accuracy, noise immunity, energy efficiency, and portability.
• Existing readout circuits may not fully meet the stringent requirements for reliable operation in diverse industrial environments.
• Silicon carbide metal-oxide-semiconductor (SiC-MOS) capacitor sensors offer potential for gas detection but require sophisticated readout electronics.

Purpose of the Study:

• To present an innovative readout circuit utilizing a phase-locked loop (PLL) architecture specifically designed for SiC-MOS capacitor gas sensors.
• To develop and validate a hydrogen detection system incorporating the proposed PLL-based readout circuit.
• To demonstrate the circuit's capability in converting sensor capacitance changes into a measurable output voltage proportional to hydrogen concentration.

Main Methods:

• Design, simulation, implementation, and experimental testing of a dedicated readout circuit based on PLL architecture.
• Integration of the SiC-MOS capacitor sensor within the voltage-controlled oscillator (VCO) of the PLL.
• Generation of a small AC signal (70 mV at 1 MHz) by the PLL block for sensor excitation and response acquisition.
• Experimental validation using hydrogen gas concentrations up to 1600 ppm.

Main Results:

• The proposed PLL circuit successfully converts the nonlinear small-signal capacitance of SiC-MOS sensors, influenced by hydrogen, into an output voltage.
• Experimental measurements showed PLL output voltage variations that closely correlated with capacitance-voltage (C-V) curves obtained from a semiconductor characterization system.
• The system demonstrated reliable performance across all tested SiC-MOS sensor samples for hydrogen detection.

Conclusions:

• The developed PLL-based readout circuit is a viable and effective solution for accurate and robust hydrogen detection using SiC-MOS capacitor sensors.
• The innovative architecture enhances sensor performance, meeting key industrial requirements for accuracy, noise robustness, and efficiency.
• This approach provides a promising pathway for advancing portable and energy-efficient gas sensing technologies in industrial settings.