Bus Voltage Control of Cascaded Buck-Boost Power Amplifier Driving Inductive Load With 2.3-kW Peak Power

Abstract

Voltage of a bus capacitor in a cascaded buck-boost power amplifier is controlled to shape current in an inductive load. Switch-mode converter and inverter output higher power with higher efficiency than linear amplifiers. However, controlling current in the inductive load with low damping is not straightforward due to its inherent instability. Voltage-mode control of a front-end buck converter adjusts the envelope of the load current through a downstream resonant boost inverter and stabilizes the system. The resonant boost inverter is modeled into a low-frequency equivalent circuit, and a control loop is designed to avoid interaction between the buck converter and resonant boost inverter. Experimental results proved that the buck converter with the voltage loop of which bandwidth and phase margin are 150 kHz and 67 degrees shaped the envelope of load current into 10-kHz (23.5-kHz) sine wave when the average output power was 320W(90 W). Instantaneous maximum power of the prototype circuit was 2.3 kW and estimated efficiency was 96%.