Derivation and Analysis of New Small-Signal Model for Active Clamp Forward Converter

Active clamp forward converter (ACFC) is widely used for low-voltage and high-current applications. Despite its extensive usage, the open-loop power stage characteristics of the converter have not been fully investigated and require further analyses. This paper reveals that the power stage dynamics of ACFC are different from those of either other buck-derived isolated converters or forward converters with different reset schemes. This paper presents a new small-signal model of the ACFC and provides the factorized expressions of the power stage transfer functions, which carry the useful information on the control design and performance evaluation. The accuracy of the small-signal model and the validity of the factorized transfer functions are verified both SIMPLIS simulations and experimental measurements.