This thesis presents an algorithm for generating a SPICE macromodel for series, parallel and series-parallel resonant converters. The algorithm is derived from the averaged time-invariant state-space equations obtained from Fourier transforms. The model developed is based solely on the fundamental Fourier component with all but the fundamental harmonic discarded. The single macromodel allows DC, AC and transient analyses to be carried out in a fast, easy, and familiar manner. It also permits the converter to be incorporated alongside its control circuitry into an entire system. The simulation results of the model are compared with the results of full circuit transient simulations for the three types of converters. The agreement is found to be excellent, with the macromodel simulation running at 37 to 4700 times faster than the full transient simulation. The accuracy of the macromodel is demonstrated by comparing its predictions with physical measurements made on a 600W series resonant converter. Simple loss models of the power devices are proposed. With the loss models, simulation results of the macromodel also give excellent agreement with the measurements. Further, the macromodel shortens the time for full circuit transient simulations and makes the calculation of stability regions of resonant converters driving a complex load possible on a circuit simulator. Limitations and further improvements of the model are also discussed. The enhanced macromodel, if successfully developed, will be able to model almost all kinds of resonant converters operating in all conduction modes. This, hopefully, will pave the way for the future development of more efficient and cost-effective power converters.