Power Line Energy Harvesting System for GaN Transistors Monitoring

Gallium nitride (GaN) transistors are a highly promising technology, with applications in high-frequency, high-temperature, and high-efficiency power systems. However, they are susceptible to various electromagnetic hazards. As a result, in-situ state-of-health (SOH) active monitoring of the device during operation is necessary, with various efforts focusing on non-invasive approaches. This study presents the design and testing of a complete, in-situ, non-invasive monitoring system powered by energy harvested from the GaN transistor’s power line (PL). Experimental results show that an external low-power load of approx. 3.6 W, such as a standard server fan, is sufficient to generate approximately 16 μW and 64 μW (i.e., for two different GaN transistors) of radiated power at the transistor’s drain connection with the PL. This emitted energy, harvested using a 100 mH inductor, is capable of powering a remote SOH monitoring system consisting of a Microchip PIC24F 16-bit microcontroller, three MCP9700 temperature sensors, and an MRF89XA 868 MHz transceiver. The resulting system is able to collect sensor data and, after a brief energy accumulation period (the system’s warm-start charging cycle), wirelessly transmit it to a base station. To further illustrate the practicality of the proposed SOH monitoring solution, the two GaN transistors were intentionally driven into a thermal runaway regime while operating in low-power mode on a 12 W load. Under these conditions, the harvested energy/emmited radiation increased to approximately 620 μW and 3,216 μW, representing about 38 and 50 times the values observed in the previous low-power demonstration, respectively.