21.2.4—The effect of a single capacitor in smoothing

A capacitor across a rectifier load charges when input exceeds its voltage and discharges through the load between peaks, reducing ripple.

Larger C or lighter load slows discharge; check the polarity and allow for diode conduction only near peaks.

A full-wave rectifier with a reservoir capacitor has smaller ripple intervals than a half-wave circuit at the same input frequency.

Smoothing does not make voltage perfectly constant, and an infinitely large capacitor would create unrealistic charging currents.