Small - Signal Analysis of Open - oop PWM

A6s t~ac t A flyback dc-dc converter is obtained from t h e conventional buck-boost converter by replacing t h e inductor with an isolation transformer. A transformer in the flyback converter is used to achieve a d c isolation between t h e input and the o u t p u t of t h e converter. This paper presents dc and small-signal circuit models for t h e flyback converter for continuous conduction mode (CCM). T h e parasitic components a re included in these models. T h e d c model is used to derive t h e equations for t h e d c voltage transfer function and the efficiency. T h e small-signal model is used t o derive the equations for t h e open-loop small-signal transfer functions, such as control-to-output transfer function, inputto-output transfer function, input impedance, and o u t p u t impedance. Bode plots a r e also given for the small-signal transfer functions.