The Output Voltage Estimator for Primary-Side Regulated Active-Clamp Forward Converter

This paper proposes an output voltage estimator for primary-side regulation of active-clamp forward converter (ACFW) to regulate its output voltage tightly. The proposed method is simple to implement as it does not require signal isolation or additional winding of the transformer. The proposed method estimates the output voltage by a polynomial function of input voltage, clamp capacitor voltage, and input current. A closed-loop control compares this estimated value to the reference to determine the duty ratio. The small-signal model of the proposed PSR method is obtained and the system is stabilized by using the model. The effectiveness of the proposed method is verified experimentally with a 100-kHz 200-W prototype ACFW.