Smoothing
A rectifier's output flows one way but rises and falls between zero and a maximum. Most electronic devices need a steady voltage like a battery's.
Smoothing
A large capacitor connected in parallel across the rectifier's output reduces the variation: smoothing. As the voltage rises the capacitor charges; as it falls the capacitor gives its stored charge back, so the output falls only a little and never to zero. The diode stops the capacitor discharging back through it.
Figure to be added
Half-wave, smoothed
The capacitor has a whole cycle to discharge, so the ripple is larger.
Full-wave, smoothed
It is recharged every half-cycle, so the output is smoother still.
| t (cycles) | 0.25 | 1.25 |
|---|---|---|
| V | 1 | 1 |
| t (cycles) | 0.25 | 0.75 | 1.25 | 1.75 |
|---|---|---|---|---|
| V | 1 | 1 | 1 | 1 |
In each graph the solid line is the smoothed output and the dashed line the unsmoothed pulses. Large capacitors, such as 1000 µF or 2000 µF, are used; the larger the capacitance, the smoother the output.