Stabilized power supply with an output voltage of 5 volts. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

 Comments on the article

Consider a number of power supplies using integrated voltage regulators.

Three-terminal integral stabilizers are widely used, designed to obtain various levels of output voltages and currents. The circuit described in this paragraph uses the 7805 integrated voltage regulator. The last two digits in the designation indicate the value of the output voltage. An even number at the beginning of the designation, consisting of two digits - 78, indicates that the regulator is designed to obtain a positive output voltage relative to the common output of the integrated circuit; an odd number indicates a negative output voltage. Therefore, the designation 7905 indicates that the three-terminal regulator provides a negative output voltage of 5 V. Similarly, the index 7812 indicates that the regulator is designed to produce a positive output voltage of 12 V.

Three-pin stabilizers, as the name implies, have three pins for connecting to external circuits: input, output and common. The common terminal is usually connected to the body ("ground") of the power supply. The input voltage is applied between the input and common terminals, the output voltage is taken between the output and common terminals. To ensure the normal operation of the stabilizer, the input voltage value at maximum load must be at least 2,5 V higher than the output voltage value. Therefore, with an output voltage of 5 V, the input unregulated voltage should not be less than 7,5 V. The maximum input voltage for the 78XX and 79XX stabilizers is 30 V. But it should be remembered that an increase in the input voltage leads to an increase in the power released in the stabilizer, and, therefore, , to increase the operating temperature. The stabilizer has a built-in overload protection: an increase in the output current in excess of the rated current leads to a decrease in the output voltage and spontaneous shutdown of the stabilizer.

Most often, it is necessary to install stabilizers on heat-removing radiators to prevent overheating. The latter can cause the stabilizer to fail.

With output currents of several hundred milliamps, ordinary metal plates can be used as radiators. However, at currents above 500 mA, it is necessary to use standard finned heat sinks, which allow to remove a large amount of heat generated in the stabilizer.

The power supply circuit is shown in fig. 5.69 It uses the following components: electrolytic capacitor C1 - 10000 microfarads, 35 V; diodes VD1-VD4 - 50 V, 3 A; fuse F1 - 0,2 A; stabilizer U1 - 7605, 7805. The voltage on the secondary winding of the transformer at a rated current of 3 A is 6,3 V. The circuit uses a full-wave bridge rectifier. The capacitive filter provides an unstabilized voltage of 8,5 V. Increasing the voltage on the secondary winding of the transformer is undesirable, as it will increase the power released in the stabilizer. The nominal value of the output current of the transformer is determined by the output power of the stabilizer.

When assembling the source, position the components so that the field connections are as short as possible. Care must be taken to ensure that the voltage stabilizer heatsink has sufficient cooling surface. The source can be used to power various electronic circuits, in particular devices based on integrated logic circuits. TTL-type (transistor-transistor logic circuits).

Stabilized power supply with a negative output voltage of 5 V.

A power supply circuit with a negative output voltage is shown in fig. 5.70. It differs from the previous one in that it uses the integrated regulator 7905, in which the common pin 3 is "grounded", as well as the positive output of the full-wave bridge rectifier. The output voltage of the rectifier negative with respect to ground is the input voltage of the regulator. The parameters of the components in the last two diagrams are completely identical.

Stabilized voltage sources with an output voltage of 12 V.

If in the scheme shown in Fig. 5.69, instead of the 7805 integrated regulator, use the 7812 three-terminal regulator, then we get a power supply with a positive output voltage of 12 V. Of course, this requires a number of changes regarding the parameters of some components. In particular, it is necessary to use a transformer with a higher secondary voltage, as the output voltage level of the power supply increases.

Taking into account fluctuations in the mains voltage (115 V) and the required value of the input voltage of the stabilizer, which must be at least 2,5 V higher than the output voltage, we can conclude that the effective value of the voltage of the secondary winding of the transformer must be at least 11 C. You can then reduce the filter capacitor to 7000 uF, and the fuse current rating must be increased to 0,5 A.

Applying components with the same parameters in the circuit shown in Fig. 5.70, and using the integrated regulator, 7912, we get a source with a negative output voltage, the absolute value of which is also equal to 12 V. Note that in both cases it is quite possible to use diodes with the same parameters: a reverse voltage of 50 V and a direct current 3 A.

These sources can be used to power a wide variety of electronic devices designed to operate with similar supply voltage levels, in particular for any automotive devices.

Author: Treister R.

See other articles Section Power Supplies.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive Apple will increase the battery capacity of the powerful version of the new iPad 03.01.2012 Apple is preparing two versions of the iPad 3 - cheaper and simplified (for the mass market) and more powerful and expensive (for the high-end market). Taiwanese sources say that the battery capacity of the powerful version of Apple's tablet will be increased to 14000 mAh, that is, twice as compared to the 2 mAh battery used in the iPad 6500 today. Apple battery suppliers Simplo Technology and Dynapack have not commented on the rumors. Meanwhile, adoption of lithium-polymer batteries like those used in the iPad 2 is expected to reach 2012% in 15, up from 5% in 2011. Global production of lithium polymer cells will reach 400 million units in 2012, and individual cell costs will remain high, at about the same level as they are today (a 20 percent increase in average cell costs occurred in the second quarter of 2011).

Other interesting news:

▪ Metals in champagne

▪ Dyson Solarcycle Morph Desk Light

▪ head grows

▪ Electric flying taxi tested

▪ Mars helicopter Ingenuity sets altitude record

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the Radio Control website. Article selection

▪ article Nothing in the eyes. Popular expression

▪ article Why is the asteroid Icarus named after the son of Daedalus? Detailed answer

▪ article Operator of computers. Job description

▪ article So are mosquitoes afraid of ultrasound? Encyclopedia of radio electronics and electrical engineering

▪ article Universal Cube. Focus Secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024