Scheme and detailed description of a homemade power supply. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Electrician

Scheme and detailed description of a homemade power supply. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Power supply. Power supplies

Comments on the article

It is often required in everyday life to connect one or another electrical device using a power supply with a step-down transformer, but it is not always possible to find a ready-made unit in a store, so you often have to think about a home-made design.

To facilitate this task, we will talk about the simplest calculations that will allow you to select the necessary parts for the power supply, depending on the requirements for it.

scheme the proposed power supply that provides the desired DC output voltage is shown in fig. 1.

It uses a power transformer that is connected by the primary winding (I) to a 220-volt AC outlet and lowers the voltage (it is removed from winding II) to a predetermined value, a full-wave rectifier on diodes VD1-VD4 and capacitor C1, smoothing out the ripple of the rectified voltage.

The resulting almost constant voltage (it will still ripple when the load is connected) is removed from contacts XS1 and XS2.

Scheme and detailed description of a homemade power supply

Rice. 1. Scheme of a homemade power supply

Rectifier calculation

It is necessary to correctly select the rectifier diodes and the filter capacitor, as well as determine the required alternating voltage removed for rectification from the secondary (II) winding of the mains transformer.

The initial data for calculating the rectifier are the required voltage at the load (Un) and the maximum current consumed by it (In)

Calculation procedure

Coefficient	Load current, A
Coefficient	0,1	0,2	0,4	0,6	0,8	1,0
В	0,8	1,0	1,2	1,4	1,5	1,7
С	2,4	2,2	2,0	1,9	1,8	1,8

First, determine the alternating voltage that should be on the secondary winding of the transformer:

Un - constant voltage at the load, V; B - coefficient depending on the load current, which is determined from the table

The load current determines the maximum current flowing through each diode of the rectifier bridge:

Id - current through the diode, A; In - maximum load current, A; C - coefficient depending on the load current and determined from the table

Next, we calculate the reverse voltage that will be applied to each rectifier diode:

Uobr - reverse voltage, V; Un - voltage at the load, V.

Rectifier diodes must be selected, in which the values of the rectified current and the permissible reverse voltage are equal to or exceed the calculated ones.

In conclusion, we determine the capacitance of the filter capacitor:

Cf - capacitance of the filter capacitor, uF; In - maximum load current, A; Un - voltage at the load, V; Kp - ripple coefficient of the rectified voltage (ratio of the amplitude value of the variable component with a frequency of 100 Hz at the output of the rectifier to the average value of the rectified voltage).

The ripple coefficient is chosen independently, depending on the expected load, which allows DC power supply of a well-defined "purity".

- small-sized transistor radios and tape recorders

- radio and intermediate frequency amplifiers

- preliminary stages of audio frequency amplifiers and microphone amplifiers

In the future, when you build such rectifiers with subsequent stabilization of the rectified voltage by a transistor stabilizer, the calculated capacitance of the filter capacitor can be reduced by 5 ... 10 times.

Calculation of the supply transformer

For him, you already have the necessary data, the voltage on the secondary winding (UII) and the maximum load current (In)

First, determine the maximum value of the current flowing through the secondary winding:

I_II - current through the winding II of the transformer, A; In - maximum load current, A.

Next, determine the power consumed by the rectifier from the secondary winding of the transformer:

P_II - maximum power consumed from the secondary winding, W; UII - voltage on the secondary winding, V; III - maximum current through the secondary winding, A.

We calculate the power of the supply transformer:

Ptr - transformer power, W; PII - maximum power consumed from the secondary winding of the transformer, W.

If a transformer is made with several secondary windings, then their total power is first calculated, and then the power of the transformer itself.

We calculate the current flowing through the primary winding of the transformer:

I_I - current through the winding I, A; Ptr - calculated power of the transformer, W; UI - voltage on the primary winding of the transformer (mains voltage), V.

We calculate the required cross-sectional area of the core of the magnetic circuit:

S - cross section of the core of the magnetic circuit, sq.cm; Ptr - transformer power, W.

We determine the number of turns of the primary (network) winding:

W_I - number of winding turns; U_I - voltage on the primary winding, V; S - cross section of the core of the magnetic circuit, sq.cm

Determine the number of turns of the secondary winding:

W_II - number of turns of the secondary winding; UII - voltage on the secondary winding, V; S - cross section of the magnetic circuit, sq.cm

Determine the diameter of the winding wire:

D - wire diameter, mm; I - current through the winding, mA.

You can choose the wire according to the finished table

Ichange, mA	25	25 60 ...	60 100 ...	100 160 ...	160 250 ...	250 400 ...	400 700 ...	700 1000 ...
D, mm	0,10	0,15	0,20	0,25	0,30	0,40	0,50	0,60

According to the data obtained, it is possible to select suitable iron, wire and manufacture a transformer. True, it is useful to first estimate whether the wire will fit on the frame of the future transformer with these W-shaped plates - after all, plates of the same type (along the width of the middle part) have an unequal window area. It is enough to multiply the previously calculated transformer power by 50 and compare the result obtained (this is the required window area in mm2) with the measured window area of the existing plates

When choosing the core of the magnetic circuit, one more rule should be followed - the ratio of the width of the middle part of the core to the thickness of the set (the ratio of the sides of the core) should be within 1 ... 2

Transformer, diodes and filter capacitor, place in a case of suitable dimensions. On the front panel of the case, strengthen the output contacts, the power switch, and place the fuse holder with the FU1 fuse on the back wall (its current depends on the current through the primary winding of the transformer). Through the hole in the rear wall, bring out the power cord with a power plug.

Publication: electro.narod.ru

See other articles Section Power supply. Power supplies.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Major risk factor for gambling addiction 07.05.2024

Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Random news from the Archive

Parsley for a thousand euros per bunch 25.08.2012

Such parsley, as well as spinach and peppermint at a price of 50 thousand euros per kilogram, are grown in Germany. Instead of the usual carbon isotope C-12, these green vegetables contain the heavier C-13. It is not radioactive, but mass spectrometry can detect it wherever it goes after eating a vegetable.

Biologists want to trace how the plant substances absorbed by the human body are distributed and how they behave in the human body. They are especially interested in the fate of flavonoids, which, according to a common hypothesis, save the body from active radicals and thus prevent many diseases.

Precious vegetables grow in a special sealed greenhouse, where carbon dioxide based on C-13 is supplied to the air. When harvesting, "gardeners" are forbidden to breathe so that the natural isotope released with exhalation does not blur the picture. Therefore, they act very quickly.

Other interesting news:

▪ Climate windshield Volkswagen

▪ Smart vest Carhartt X-1

▪ Toshiba Wireless Hard Drive Solution

▪ Crossover Genesis GV60 recognizes its owner by face

▪ The danger of global warming for aircraft

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Parameters, analogues, marking of radio components. Article selection

▪ article Under the sly. Popular expression

▪ Where Did Dinosaurs Live? Detailed answer

▪ article Operator on automatic and semi-automatic lines, engaged in facing the edges of shields. Standard instruction on labor protection

▪ article Semiautomatic device for an eternal lamp. Encyclopedia of radio electronics and electrical engineering

▪ article Amazing Chinese cabinet. Focus secret

Leave your comment on this article:

All languages of this page

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