A Simplified Power Control Scheme for Resonant Inverter with Purely Resistive Load

This paper presents a simplified power control scheme for resonant inverter with purely resistive load and low-harmonic output waveforms. The control scheme was implemented in the power control of radio-frequency generator-the power source of an electro surgical unit. As the proposed control scheme does not conform to standard feedback control scheme, the standard controller design technique can not directly be applied. By applying small- signal perturbation and linearization technique to the simplified control scheme, its small-signal model does reveal power feedback, and the standard controller design procedure can be used. The proposed control scheme features feed forward of power control signal, and only voltage controller design is required. Steady-state errors and transient responses of the proposed control scheme were investigated. The theoretical calculations were verified by computer simulations and hardware realization.