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About Rectifiers
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What was rectifier?
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The development of rectifiers
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How do rectifiers work?
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Can rectifiers do more?
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Which rectifiers can you find at Conrad?
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What should you pay attention to when using rectifiers?
What was rectifier?
The power supply network supplies an alternating voltage of 230 Volt with the mains frequency of 50 Hertz at the domestic socket. In some countries, other voltages (110 volts) and line frequencies (60 hertz) are common.
This allows many home appliances to be operated directly, provided they are designed for this voltage. However, if electronic control components come into play, DC voltage is required. The operation of various electrical devices such as different amplifiers and electronic controls also requires direct voltage .
As the end user, you usually don't get much of it because the required supply voltage of the type and height is provided by components in the devices concerned by means of power supplies. Starting from the sinusoidal mains voltage, the required voltage level is provided by means of a transformer. To convert this still sinusoidal AC voltage into the required DC voltage, rectifiers are used in combination with other electronic components.
The development of rectifiers
The first rectifiers, which have been developed by various scientists already in the outgoing 19. Developed and patented in the 19th century, only suitable for small currents. In order to meet the requirements of the growing use of electrical energy, various methods have been tried over time to convert AC voltage into DC voltage. These included electromechanical solutions with AC and DC motors on a shaft, switching techniques that revealed their weaknesses through contact burn.
The dry rectifiers with their typical panel design, based on the chemical element selenium, have been developed over many, partly experimental, ways, among others using tubes and glow lamps.
Only with the invention of the transistor shortly after the Second World War, the so-called p-n-transition (positive-negative) became usable, by allowing a applied voltage to flow through the semiconductor crystal in only one direction, while the current flow in the opposite direction is blocked. This made very small rectifier components possible on a semiconductor basis, first in the form of germanium diodes and then silicon diodes. The latter are more temperature-resistant than their chemical “relatives”.
How do rectifiers work?
Depending on the direction of the rectifier diode, the applied AC voltage can pass through the rectifier with the positive half-wave, for example, while the negative half-wave is blocked (pause). To buffer the "pauses" in the power supply, capacitors are used on the DC side that "jump in" when the negative half-wave is locked.
In order to make the rectifier process more effective, German physicist Leo Graetz developed the bridge rectifier, which is named after it as a Graetz circuit and is equipped with four defined interconnected diodes.
Only the positive half-waves arrive after the rectification without pause due to negative half-waves. This results in ripple that doubles the frequency of the original AC voltage was used, which reduces the amount of smoothing required.
A similar effect is provided by the so-called center rectifier , in which a transformer with center point tap is required. This form of rectification has the advantage that only two diodes are required.
Three-phase AC converters are used, for example in automotive alternators, where the smoothing is carried out by the car battery.
Can rectifiers do more?
If the rectifier diodes are equipped with a controller that informs them when they should pass through the respective half-wave, voltage controls can be implemented. The are ranked under the technical term "phase control". The components for this are called thyristor.
Voltage duplication and duplication are also possible by selective interconnection of diodes and capacitors. This technology was used, for example, in TV sets with picture tubes to generate high anode voltages.
Practical advice
Semiconductor components are temperature sensitive . Therefore, when soldering the rectifiers, make sure that the diodes are not thermally overloaded and that there is no mechanical stress on the connections. In the hobby area, it is recommended to use soldering stations with which a reliable soldering temperature can be set.
Which rectifiers can you find at Conrad?
The rectifiers in our shop are divided into:
Diode Bridges
Bridge rectifiers combine the Graetz circuit mentioned above in one housing. They are available for voltages from 40 to 1,800 volts. The number and interconnection of the diodes are listed under the menu item "Configuration (diode)". There are various housing designs.
Diode Array Bridges
Rectifier diode arrays also combine several diodes in one housing, however they are not built in a bridge circuit, but are available via the external connections for use according to the requirements of the respective electronic circuit. There are also many different housing shapes for these rectifiers.
The “Schottky diode” is to be mentioned. It consists of a metal-semiconductor junction, which is particularly well-proven in high-frequency applications – for example, in switched-mode power supplies. This development was named after the German physicist Walter Schottky. Many of these components are designed for industrial processing techniques.
What should you pay attention to when using rectifiers?
When using rectifier elements, the country-specific laws and regulations must be observed . In addition, various diodes are suitable for use in office machines, communication equipment, measuring devices and household applications. For use in areas with special safety requirements, such as aircraft, motor vehicles and life-saving equipment, many manufacturers offer separate components.
It is important to always use the rectifiers with the appropriate electrical parameters. Please also refer to the manufacturer's data sheets in order to comply with restrictions or operating conditions. The data sheets are available for download free of charge on the respective product page.
For experimentation with rectifiers, use only small voltages from special power supplies and not a 230-volt mains voltage.