In which devices is a rectifier used


Lexicon> letter G> rectifier

Definition: a device that generates direct current from alternating or three-phase current

Alternative term: AC / DC converter

Counter-term: inverter

English: rectifier

Category: electrical energy

Author: Dr. RĂ¼diger Paschotta

How to quote; suggest additional literature

Original creation: 09/11/2012; last change: 15.05.2021


Rectifier are a type of power converter that can generate direct current from alternating current or three-phase current. They are often used in power supplies to rectify the low-voltage AC voltage obtained in a transformer. An alternative name is AC / DC converter: a device that can convert AC (alternating current) to DC (direct current).

The is especially used for single-phase alternating current Bridge rectifier, which contains four semiconductor diodes, while simple half-wave rectifiers manage with a single diode. In the latter case, there is a contribution to the output voltage and power only for the half-waves of the voltage with a certain polarity, while a bridge rectifier has a Full wave rectification enables. Various other rectifier circuits are used in special cases. The diodes let electrical current through in one direction, but block it in the other direction. First, a pulsating DC voltage is created (i.e. with a level that fluctuates over time), which can be smoothed over time with an additional smoothing capacitor.

Diodes based on vacuum tubes can also be used in rectifiers, but have hardly been used for a long time. The same applies to mercury vapor rectifiers. On the other hand there is in high voltage technology controlled rectifier with thyristors instead of diodes. These only allow the flow of current when they have been prompted to do so by a control voltage.

Since a voltage drop occurs on the semiconductor diodes used, part of the electrical energy is lost during rectification. Nevertheless, the efficiency of rectifiers, at least at higher voltages, at which the voltage drop in the diodes is of little consequence, is usually quite high (usually well over 90%). For low voltage devices, the voltage drop can be greatly reduced by using MOSFETs instead of diodes. The use of such switchable components also offers the possibility of using the same device either as a rectifier or as an inverter - for example as part of a vehicle drive, in which either energy from a battery is fed to a three-phase motor (operation as an inverter) or within the framework of braking energy recovery Battery is being charged (rectifier operation).

There are so-called inverters for converting direct current into alternating or three-phase current.

Applications of rectifiers

A large number of small rectifiers are built into power supply units that generate small devices with DC voltage. There are also very large and powerful rectifiers for coupling AC and DC networks. This technology is important for high-voltage direct current transmission (HVDC).

In switched-mode power supplies, the line voltage is usually rectified first, followed by a change in the level of the electrical voltage, often with galvanic isolation.

When charging electric cars, or more precisely their batteries, the rectification takes place either in the charging station (DC charging) or in the charger inside the vehicle (AC charging).

Rectification is not always about energy transfer. For example, small rectifiers also serve as envelope demodulators in analog radio receivers.

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See also: direct current, alternating current, power converter, power supply unit, switching power supply unit, inverter
as well as other items in the electrical energy category