A generalised state-space averaging technique particularly suited to resonant convertor analysis is applied to a parallel resonant convertor topology which produces high frequency power from a DC source. The convertor uses two power transistors configured in a low-cost push-pull arrangement that features low RFI emission and high efficiency owing to the zero voltage switching and absence of circulating current in the devices. Linear state-space models for the convertor describing its harmonic and transient characteristics are derived and compared with those obtained analytically and by experiment. Good agreement is observed in both cases thus validating the models.