Multilevel Cascaded H-Bridge Linear Amplifier with Unequal DC Capacitor Voltages Using a DC Voltage Source

Abstract

This study discusses a multilevel cascaded linear amplifier that includes multiple H-bridges. The amplifier operates the MOSFETs in the switch mode and active state. The MOSFETs in the switch mode change the voltage level to reduce the ripple voltage, which is filtered using the MOSFETs in the active state. Thus, the conversion efficiency of the amplifier is improved. The MOSFETs in the switch mode also control the charging state of the capacitor on the DC-side of each H-bridge to maintain the DC capacitor voltages. The amplifier can perform real power conversion with one DC voltage source as it can regulate the DC capacitor voltage of each H-bridge. Moreover, DC capacitor voltages are regulated at various values to further reduce the ripple filtered by MOSFETs in the active state. Lastly, DC capacitor voltage control was verified through a experiment using three H-bridges, and the measured conversion efficiency of the amplifier with unequal DC capacitor voltages was 87.9%.