Comparison of averaging and harmonic balance methods for switched DC-DC converters

Line-to-output and Control-to-output frequency responses describe behavior of DC-DC converters under small-signal perturbation of the input voltage or the duty ratio. The responses are routinely obtained using the state space averaging method, which represents a certain simplification. The paper deals with validity of the obtained responses. Using the harmonic balance method as the reference it will be shown that the responses may be valid even above the Nyquist frequency depending on the structure of state matrices. The analysis has been made for all major types of converters.