Simulations of two types of constant-frequency resonant power converters using SPICE-2/I-G SPICE are performed. The first one is a parallel resonant converter (PRC) using a controlled output rectifier. The PRC is operated at a constant frequency and its output voltage is regulated by controlling the firing angle of the output rectifier. The other circuit is the phase-controlled dual resonant converter (DRC) which employs two PRCs with their output (Capacitor voltages) connected in series. In the scheme, again the PRCs are operated at a constant frequency. By controlling the phase delay of the two PRCs, regulation of the output voltage is achieved. The behaviors of these two types of constant frequency resonant converters have been analyzed in details recently by Tsai and documented in his thesis. The objectives of the present work is to verify some of Tsai's key findings via computer simulations. First of all, the DC output characteristics of the parallel resonant converter (PRC) using the conventional acontrol (phase control) scheme and the new a-control scheme are simulated. The a-control scheme is implemented by monitoring the delay angle of the output controlled rectifier and the zero-crossing of the resonant capacitor voltage waveform while the a control is implemented by monitoring the delay angle of the output controlled rectifier with respect to the switching instance of the input inverter. The current and voltage ratings of different circuit components as a function of the control parameter-a angle are shown. The control-to-output characteristics are verified. The advantages of acontrol scheme is demonstrated. Simulation results of the phase-controlled dual resonant converter (DRC) are presented under various operating conditions. A comprehensive understanding of the behavior complex of the DRC are obtained. The ability to regulate the link voltage of the DRC is demonstrated. Boundary conditions of the DRC for natural commutation ( line or load) of the power devices are also verified. Some comments on SPICE-2/I-G SPICE simulation of the resonant circuits are presented. / M.S.