A symbolic, automatable, exact, ‘top-down’ algorithm for computing the transient and steady-state response of DC-to-DC converters is presented. The procedure is applicable to any DC-to-DC converter, regardless of its structural complexity, number of reactive elements, and number of electronic switching devices. Each linear switch configuration that the circuit goes through during a cycle is described by a set of state equations. Their solution represents the state variables waveforms which characterize the dynamic behaviour of the converter in the interval corresponding to the configuration taken into account. As the state variables are the same in all configurations, and the state is continuous across each switching change, the above partial solutions are alternatively used for computing the transient and steady-state response of the circuit. The result is exact and the continuous character of the converter variables is preserved. The method is illustrated by application to the computation of the dynamics of a boost-buck converter in optimal topology.