Operating Principle, Analytical Modeling, and Design Calculations of a GaN-Based Class-D Inverter with Resonant Pi-Filter

High-frequency, high-efficiency DC-AC power conversion requires power semiconductor devices with minimal switching losses and low parasitic ON-state resistance, paired with high-order resonant filters capable of suppressing carrier switching harmonics. This manuscript provides an analytical design, mathematical modeling, and simulation study of a full-bridge Class-D inverter utilizing 650 V Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs - GS66508B) integrated with a symmetrical resonant Pi-filter stage. Operating under a 100 V DC bus, 100 kHz sinusoidal target frequency, and 1.5 MHz SPWM carrier excitation (mf = 15, Ma = 1.0), the converter achieves >40 dB attenuation of carrier harmonics, near-ideal sinusoidal output (THD < 1.5%), and an output power of 505.35 W across a 25-Ohm resistive load with minimal semiconductor conduction losses (1.012 W).