A continuous, low-frequency, small-signal averaged model for the tapped-inductor boost converter with input filter is developed and experimentally verified, from which the dc transfer function and the small-signal line input and duty ratio input describing functions can easily be derived. A new effect due to storage-time modulation in the transistor switch is shown to explain observed excess filter damping resistance without associated loss in conversion efficiency. The presence of an input filter can cause a severe disturbance, even a null, in the control duty ratio describing function, with consequent potential performance difficulties in a converter regulator.
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