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One of the major drawbacks of high-ratio step-up transformers is the high value of their secondary side capacitor. This value is reflected at the primary side giving rise to a non-desirable one. There are some converters which include this capacitor in the topology and can cope with it, and even more, they need it. Particularly, in high-voltage applications, we will find transformers with a large capacitance value, since they use high-ratio step-up transformers. In this kind of applications, it is always interesting not to have inductors at the output filter, with single-capacitor filters being preferred instead. Thus, one the simplest topologies, is the parallel resonant converter (PRC) with single capacitor output filter. It can be controlled by switching frequency and/or duty cycle, and makes feasible to have ZVS (zero voltage switching) in the power switches. In this paper, the PRC modelling and design, plus experimental results are shown in a prototype delivering 3.5 kV, 260 W.