This paper presents a novel predictive digital control method for boundary conduction mode PFC converters without the need for detecting the inductor current. In the proposed method, the inductor current is predicted by analytical equations instead of being detected by a sensing-resistor. The predicted zero-crossing point of the inductor current is determined by the values of the input voltage, output voltage and predicted inductor current. Importantly, the prediction of zero-crossing point is achieved in just a single switching cycle. Therefore, the errors in predictive calculation caused by parameter variations can be compensated. The prediction of the zero-crossing point with the proposed method has been shown to have good accuracy. The proposed method also shows high stability towards variations in both the inductance and output power. Experimental results demonstrate the effectiveness of the proposed predictive digital control method for PFC converters.

The purpose of this paper is to present a influences of parameter deviations on operation of a novel current sensorless AC-DC converter are discussed. The off time is calculated based on the equations of each operating state for boundary current control mode. The relationship among the THD, power factor and efficiency, and circuit parameter errors are discussed. When the circuit parameter varies from designed parameters, the predicted off-time can also be deviated from the optimum value. The characteristics of sensorless ac-dc converter won't change a lot when an error occurs between the main circuit and the designed parameters of the inductor.

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