Design of a resonant inverter with variable voltage and constant frequency

A series inverter circuit is proposed that provides constant output frequency and a wide range of output voltage control. This circuit overcomes one of the major disadvantages of series inverters normally providing only a small range of voltage control at varying frequency. The circuit is a combination of two basic inverter circuits. The voltage control is achieved by phase-shifting the output voltages of the basic inverters. The authors provide a circuit analysis and a model to study the unsymmetrical operation of the two basic inverters in the combined circuit. Based on the analysis, the inverter performance is evaluated and design rules are established to achieve good regulation of the output voltage, low harmonic distortion and optimal inverter rating. The theoretical results are verified experimentally.<>