This paper describes an efficient simulation approach of a DSP controlled series-parallel resonant high frequency DC-DC power converter system. Proposed power conversion circuit simulation approach is based on a circuit equation, modeled by substituting time-varying switched resistor circuit in place of all the controllable and uncontrollable power semiconductor switching blocks of power converter circuits. An algebraic algorithm transforms the matrices of the circuit equation into the matrices of the state vector equation. Solution of state equation is by 3rd order Runge Kutta numerical integration method. Simulation results are illustrated and discussed together with experimental results.