Extended ripple analysis of PWM DC-to-DC converters

By employing a Taylor series expansion of the state, simplified expressions are derived for the first- and second-order terms of the state ripple of any pulse-width-modulated (PWM) DC-to-DC power converter operating in continuous conduction mode. Under the assumption that the ripple is dominated by its lowest-order nonzero component, along with the ripple order relationships between state variables, these expressions may be used on any PWM power converter to derive design guidelines for optimum ripple performance. An example is given of a fourth-order boost-type power converter in which, after determining conditions by which the first two lowest-order components in the output voltage ripple are nulled, further conditions are derived that minimize the third-order component, resulting in enhanced ripple performance. The results are verified by simulation