Initial Resonant Current Control for Extra-LC Auxiliary Resonant Snubber Soft-Switching Inverter Without Filter Inductor Current Sensor

The initial resonant current in the extra-LC auxiliary resonant snubber inverter (ELCARSI) is the key parameter to realize soft switching and improve output quality. However, the initial resonant current is related to the filter inductor current. Thus, an extra filter inductor or capacitor current sensor is required, which increases the cost and hardware complexity. Besides, the traditional control strategy using load current to calculate the initial resonant current doesn’t require the extra sensor. However, the current stress and output distortion is increased. Thus, an initial resonant current control strategy without filter inductor current sensor is proposed in this paper. The operating principle of ELCARSI is introduced. The output quality and soft switching influenced by the initial resonant current are analyzed. Besides, the proposed sensorless control with estimation of filter inductor current is introduced. A prototype was developed to verify the effectiveness of the control method. The output distortion is close to that of the control with extra sensor.