Accurately Determine Steady-State Output for a Periodically Driven RC Filter

摘要

A recent idea for Design showed a graphical technique for determining the output of an RC filter driven by a pulse-width modulation (PWM) pulse train.1 It requires the manipulation of infinite series with a limit. Therefore, it does not yield steady-state results with confidence. A better approach uses the concept of continuity of states and steady-state "wrap-around" to eliminate this shortcoming, since current and voltage values in a real circuit cannot change instantaneously. Current and voltage are variables with continuous values in time, from moment to moment. For a circuit structure that is switched periodically among several states repeatedly, the end state of one structure serves as the starting state of the next.