Pulsating direct current
A pulsating direct current is a direct current (dc) that changes in value over short periods of time.
A pulsating direct current may change in value, i.e., be always present but at different levels, or it may be interrupted completely. The changes may be irregular or at regular intervals (at a specific frequency), but the current never changes direction.
Pulsating currents are commonly the consequence of using diode rectifiers, or DC sources of lower amplitude connected in series with AC sources. It can be smoother, if a large value capacitor is used in parallel with the rectified source.
Pulsating direct current is used on PWM controllers.
Difference from AC
Pulsating direct current has an average value equal to a constant (DC) along with a time-dependent pulsating component added to it, while the average value of alternating current is zero in steady state (or a constant if it has a DC offset, value of which will then be equal to that offset).
References
- This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C".