Methods, control apparatus and series resonant or LLC power conversion systems are presented in which a resonant series circuit current is compared with a threshold during a portion of a modulation switching cycle following turn on of a corresponding switching device and one or more indications or remedial actions are undertaken to modify modulation control of a switching circuit in response to a determination that the resonant current is below the threshold to facilitate our promote zero voltage switching or near-zero voltage switching and provide current reversal protection.