Output Impedance Analysis of PWM DC-to-DC Converters

The output impedances of pulse width modulated (PWM)dc-to-dc converters, which dictate the outcomes of the dynamic interaction between dc-to-dc converters and their load subsystem, are analyzed in a general and unified manner. This paper presents the analytical expressions of the output impedances of three basic PWM dc-to-dc converters operating with current mode control. It also provides a comprehensive reference for future dynamic interaction analyses requiring knowledge of the converters output impedances. The theoretical predictions are all supported by measurements on prototype dc-to-dc converters. The use of the presented results is demonstrated via practical application examples, which deals with current-mode controlled buck and boost converters connected with practical load subsystems.