Reservoir capacitor

The pulsating DC from an AC rectifier (either half-wave or full-wave) usually needs to be smoothed before use. This can be done using a Reservoir capacitor.

Performance with low impedance source

The above diagram shows reservoir performance from a near zero impedance source, such as a mains supply. As the rectifier voltage increases, it charges the capacitor and also supplies current to the load. At the end of the quarter cycle the capacitor is charged to its peak value Vm of the rectifier voltage. Following this the rectifier voltage starts to decrease as it enters the next quarter cycle. This initiates the discharge of the capacitor through the load, Above about the Reservoir capacitor information content.

Performance with significant impedance source

These circuits are very frequently fed from transformers, and these have significant resistance. Transformer resistance modifies the reservoir capacitor waveform, changes the peak voltage and introduces regulation issues, Above about the Reservoir capacitor information content.

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