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In this paper, a small-signal model for a new singleswitch single-stage switched-mode power-factor-correction (PFC) converter is presented. The model is obtained by applying the small-signal perturbation technique to the circuit equations derived from the state-space averaging method. By applying the perturbation and averaging techniques over one switching cycle, the dc and small-signal equivalent circuit representations of this converter are derived. The result shows that this converter exhibits the transfer characteristics of a second-order low-pass system for the output-to-input transfer function and that of a combined second-order low-pass and band-pass system for the output-to-control transfer function. The validity of the proposed mathematical model was verified by the given experimental results for a specified design example.

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One-stage power factor correction (PFC) with output electrical isolation. The converter has a configuration of combining a boost circuit and a forward circuit in one power stage. To relieve the voltage spike caused by the leakage inductance of the power transformer, two bulk storage capacitors are used. The same power switch is shared by the PFC circuit and the power conversion circuit. Due to its simplified power stage and control circuit, this converter presents a better efficiency (87%), lower cost and higher reliability. Detailed steady state analysis results show this novel converter has both good power factor correction and excellent regulation capabilities. With PSPICE simulation and experimental results, a measured power factor of 0.99 was obtained by this single switch converter.

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