Abstract: A resonant or semi-resonant voltage converter includes a synchronous rectification (SR) switch through which a current having a half-cycle sinusoidal-like shape is conducted when the SR switch is active. The current through the SR switch is modelled, and estimates of the SR switch current are generated by a digital estimator based on the model. The SR switch current estimates are updated at a fairly fast rate, as may be needed by a controller of the voltage converter. Analog converters are run at a slower rate, and generate error signals that are fed back into the digital estimator in order to improve future SR switch current estimates. Because the analog converters run at a fairly slow rate, power usage is minimal. However, the SR switch current estimates are updated at a rate that is fast enough to provide adequate control for the voltage converter.