Output and loss caused by load changes in MOSFET RF power inverter

The drain efficiency of the full-bridge SEPP power inverter is analyzed numerically. Expressions for the drain loss when the load changes are described, and then the drain efficiency, output power, and drain loss are calculated in terms of the load VSWR (virtual standing wave ratio) and frequency. Calculated and experimental results are in good agreement. They show that the drain efficiency in the inductive load decreases only a few percent or less if compared with that for the matched resistive load, but the drain power loss in the capacitive load is much greater than that in the inductive load due to the short-circuit current caused by the charges stored in the parasitic p-n junction diode of each MOSFET. The drain efficiency decreases over 10% in the capacitive load compared with that for the matched resistive load.<>