A new method for small-signal analysis of switching power converters is developed and implemented in a computer program. The method is derived for systems where the nonlinearities can be described by elements that can take on one of two values, based upon a controlling variable. Another requirement is that the system be periodic. The method is shown by examples to be very accurate, even at high frequencies. It predicts the subharmonic oscillation that can occur in converters with constant-frequency current-mode control. It is implemented using the COSMIR program to solve for the state equations and for steady-state, making a general power supply simulation program. / Ph. D.