Ripple voltage

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In electrical engineering, ripple voltage is the residual ripple of the electrical voltage , i.e. the remaining AC voltage component of a smoothed or regulated supply voltage after it has been rectified by a rectifier and smoothed by a capacitor and / or reduced to a lower level by a voltage regulator .

General

1) AC voltage rectified
2) pulsating DC / mixed voltage smoothed by an additional capacitor

Public power grids in Europe are operated with alternating voltage and a grid frequency of 50 Hz (in some countries 60 Hz). To operate entertainment electronics devices, a DC voltage that is as constant as possible is generally required. When converting AC voltage to DC voltage ( using the power supply unit with transformer ), it is therefore important to smooth the voltage fluctuations of the AC voltage caused by the phase curve (1st and 2nd figure on the right) as well as possible to a constant DC voltage level. However, there may still be residual ripple in the supply voltage, an alternating voltage component that can be heard in headphones or loudspeakers as a hum of 50 Hz (100 Hz for full-wave rectification) and is also referred to as mains hum .

If an alternating voltage is rectified with diodes, a voltage peak occurs in the middle of every half period , which drops back to zero (1st figure on the right) . This drop can be delayed with a capacitor, but not prevented. Thus, in every half period there is a difference between the peak voltage and the lowest point of the capacitor voltage before the rise again (2nd figure) . This resulting voltage difference is called the ripple voltage. It can be measured with a "coupled TRUE RMS measuring device" ( effective value ).

The ripple voltage can be minimized by using capacitors with the largest possible capacity. The capacitor should be dimensioned in such a way that it can cover the power requirements of the consumer in the low-voltage phase. With the additional use of a voltage regulator, which limits the output voltage constantly to a level that is below the lowest voltage supplied by the diode rectifier and capacitor, the ripple voltage can be almost completely eliminated. For this purpose, an AC voltage is required as the input signal, which on average is somewhat greater than the DC voltage required at the consumer.

See also

literature

  • Klaus Beuth and Wolfgang Schmusch: Electronics 3. Basic circuits . 10th expanded edition. Vogel-Fachbuch, Würzburg 1990, ISBN 3-8023-0555-8 . Pp. 45-50 + pp. 188-209 (448 pp.).
  • Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics 1st part. Basics of electronics . 8th edition. Verlag Europa-Lehrmittel, Wuppertal 1980, ISBN 3-8085-3178-9 .
  • Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics 3rd part. Communications electronics. 5th edition. Verlag Europa-Lehrmittel, Wuppertal 1980, ISBN 3-8085-3225-4 .
  • Fritz Kühne: Low-frequency amplifier with tubes and transistors . 13th edition. Franzis Verlag, Munich 1970.
  • Siegfried Wirsum: Nf tricks for the audio freak . 1st edition. Franzis Verlag, Munich 1990, ISBN 3-7723-3321-4 .