As well as these time-varying phenomena, there is a frequency domain ripple that arises in some classes of filter and other signal processing networks. Ripple is wasted power, and has many undesirable effects in a Ripple frequency of half wave rectifier circuit: it heats components, causes noise and distortion, and may cause digital circuits to operate improperly. Ripple may be reduced by an electronic filter, and eliminated by a voltage regulator.

The initial step in AC to DC conversion is to send the AC current through a rectifier. AC voltage minus the forward voltage of the rectifier diodes. In the case of a SS silicon diode, the forward voltage is 0. Please expand the section to include this information. Further details may exist on the talk page. Reducing ripple is only one of several principal considerations in power supply filter design. The filtering of ripple voltage is analogous to filtering other kinds of signals.

DC power conversion as well as DC power generation, high voltages and currents or both may be output as ripple. The majority of power supplies are now switched mode. The filtering requirements for such power supplies are much easier to meet owing to the frequency of the ripple waveform being very high. The number of reactive components in a filter is called its order. A common arrangement is to allow the rectifier to work into a large smoothing capacitor which acts as a reservoir. At that point the rectifier conducts again and delivers current to the reservoir until peak voltage is again reached. If the RC time constant is large in comparison to the period of the AC waveform, then a reasonably accurate approximation can be made by assuming that the capacitor voltage falls linearly.

A further useful assumption can be made if the ripple is small compared to the DC voltage. For the rms value of the ripple voltage, the calculation is more involved as the shape of the ripple waveform has a bearing on the result. Assuming a sawtooth waveform is a similar assumption to the ones above. Another approach to reducing ripple is to use a series choke.

A choke has a filtering action and consequently produces a smoother waveform with fewer high-order harmonics. There is a minimum inductance which is relative to the resistance of the load required in order for a series choke to continuously conduct current. If the inductance falls below that value, current will be intermittent and output DC voltage will rise from the average input voltage to the peak input voltage – in effect, the inductor will behave like a capacitor. R is the load resistance and f the line frequency. For that reason, a choke input filter is almost always part of an LC filter section, whose ripple reduction is independent of load current.