A unified set of input-dependent coordinates is proposed for the description of parallel and series resonant converters. The description naturally leads to a hybrid feedback control strategy for self-oscillating behavior. We show through a hybrid representation that the ensuing dynamics admits a unique almost globally attractive hybrid limit cycle. A tuning parameter, the switching angle, is then numerically shown to lead to monotonic variation of the peak output current/voltage and of the self-induced switching frequency. Numerical simulations with high-accuracy software illustrate the desirable behavior of the self-oscillating scheme, and it robustness to unmodeled phenomena.