Somehow recently I came across a diagram on the Internet that was very simple block power supply with voltage regulation. The voltage could be adjusted from 1 Volt to 36 Volt, depending on the output voltage on the secondary winding of the transformer.

Take a close look at the LM317T in the circuit itself! The third leg (3) of the microcircuit is connected to capacitor C1, that is, the third leg is INPUT, and the second leg (2) is connected to capacitor C2 and a 200 Ohm resistor and is an OUTPUT.

Using a transformer from mains voltage 220 Volts we get 25 Volts, no more. Less is possible, no more. Then we straighten the whole thing with a diode bridge and smooth out the ripples using capacitor C1. All this is described in detail in the article on how to obtain constant voltage from alternating voltage. And here is our most important trump card in the power supply - this is a highly stable voltage regulator chip LM317T. At the time of writing, the price of this chip was around 14 rubles. Even cheaper than a loaf white bread.

Description of the chip

LM317T is a voltage regulator. If the transformer produces up to 27-28 volts on the secondary winding, then we can easily regulate the voltage from 1.2 to 37 volts, but I would not raise the bar to more than 25 volts at the transformer output.

The microcircuit can be executed in the TO-220 package:

or in D2 Pack housing

It can pass a maximum current of 1.5 Amps, which is enough to power your electronic gadgets without voltage drop. That is, we can output a voltage of 36 Volts with a current load of up to 1.5 Amps, and at the same time our microcircuit will still output 36 Volts - this, of course, is ideal. In reality, fractions of volts will drop, which is not very critical. With a large current in the load, it is more advisable to install this microcircuit on a radiator.

In order to assemble the circuit, we also need a variable resistor of 6.8 Kilo-Ohms, or even 10 Kilo-Ohms, as well as a constant resistor of 200 Ohms, preferably from 1 Watt. Well, we put a 100 µF capacitor at the output. Absolutely simple scheme!

Assembly in hardware

Previously, I had a very bad power supply with transistors. I thought, why not remake it? Here is the result ;-)

Here we see the imported GBU606 diode bridge. It is designed for a current of up to 6 Amps, which is more than enough for our power supply, since it will deliver a maximum of 1.5 Amps to the load. I installed the LM on the radiator using KPT-8 paste to improve heat transfer. Well, everything else, I think, is familiar to you.

And here is an antediluvian transformer that gives me a voltage of 12 volts on the secondary winding.

We carefully pack all this into the case and remove the wires.

So what do you think? ;-)

The minimum voltage I got was 1.25 Volts, and the maximum was 15 Volts.

I set any voltage, in this case the most common are 12 Volts and 5 Volts

Everything works great!

This power supply is very convenient for adjusting the speed of a mini drill, which is used for drilling circuit boards.

Analogues on Aliexpress

By the way, on Ali you can immediately find a ready-made set of this block without a transformer.

Too lazy to collect? You can buy a ready-made 5 Amp for less than $2:

You can view it at this link.

If 5 Amps is not enough, then you can look at 8 Amps. It will be enough for even the most seasoned electronics engineer:

This review of the channel “Reviews of parcels and homemade products from jakson” is about a simple circuit of a bipolar power supply with an output voltage of 15 volts. The circuit that we will assemble does not require many parts. The main thing is to find 2 regulators 7815 and 7915. They can be ordered in China.

Radio components and boards can be purchased with free delivery in this Chinese store.

As a result, the output should be plus 15 and minus 15 volts of bipolar power supply. To do this, we need a special transformer, at the output of which we can obtain bipolar power with a midpoint.

This can be achieved in two ways. For example, if a transformer is built in such a way that between its two contacts (in our case +15 and -15) there is a middle point, which is the contact of the middle of the secondary winding. The voltage between the middle and first contacts will be 15 volts, and between the middle and last contacts will also be 15. Between the first and last - 30 volts.

If the design of the transformer does not provide the point we need, we can take two secondary windings with the same voltage. The midpoint between them will be the midpoint of our 2-polar power supply. Let's do so. There will be not 2 windings, but 4, since there are many secondary windings in this transformer, we will connect several to obtain the required voltage.

An old Soviet military transformer will be used, which is over 30 years old. Despite this, it works great and essentially there is nothing to break, since it is completely flooded and sealed. Perhaps its quality will be even better than that of modern Chinese transformers. But its power is only 60 watts.

The assembly of the block will be carried out on a breadboard printed circuit board good quality. The diode bridge contains IN 5408 diodes. There will be enough of them to spare. We will also need four electrolytic capacitors. Two of them are 2200 microfarads, 25 volts and the other are 100 microfarads, 35 volts. Two 0.1 µF capacitors. Also the regulators discussed above. When soldering the regulators, be careful, as they have different pinouts.

There are two LEDs in the circuit - indicators that are not particularly needed; they can be omitted.

Discussion

1. Why these stabilizers and all this extra stuff? A transformer with a midpoint, two arms of 18 volts each, is what you need. Just straighten the two phases, pass them through the containers and onto the amplifier. Why do you need these 1-amp stabilizers to choke the microcircuit and heat up in addition? With such success, you can simply install the car radio at 12 volts and it will give out more. According to the tda 7294 characteristic, +/-27 volts per 4 ohm speaker.
2. The power is not enough to power the amplifier. The stabilizers produce about 1.5 Amperes of current, while heating up like hell! The radiators in the video are not enough for cooling. This circuit can only be used to power small loads.
3. Question from a stranger.)) Why do you need bipolar power? What’s worse than connecting two 15 volts in parallel (increasing the current) and assembling two identical amplifiers independent of each other and powering them with one plus and one minus? I have two 7296 microcircuits, I want to make two amplifiers out of them, for the left and right channels and for the sub from an Ali mono amp for 60 watts class D. And power it all with one output from the transformer

The power supply does not require any setup; it works well immediately after assembling the circuit; when turned on, the output voltage should be smoothly regulated by the variable resistor R1 from 0 to 15 Volts. To ensure reliable operation under heavy loads, install the output transistor VT2 and the diode bridge VDS-1 on a cooling radiator of sufficient area; the remaining radio elements practically do not heat up and can be operated without cooling.

Every radio amateur and designer will find a use for this device; a power supply built according to this scheme is very useful when setting up various radio circuits, testing low-voltage equipment that changes its parameters when adjusting the supply voltage, and so on... If you connect an ammeter to the output of the device, then it can be successfully used to charge car batteries, while controlling the charging current.

How to assemble a simple power supply and a powerful voltage source yourself.
Sometimes you have to connect various electronic devices, including homemade ones, to a 12 volt DC source. The power supply is easy to assemble yourself within half a weekend. Therefore, there is no need to purchase a ready-made unit, when it is more interesting to independently make the necessary thing for your laboratory.


Anyone who wants to can make a 12-volt unit on their own, without much difficulty.
Some people need a source to power an amplifier, while others need a source to power a small TV or radio...
Step 1: What parts are needed to assemble the power supply...
To assemble the block, prepare in advance the electronic components, parts and accessories from which the block itself will be assembled....
-Circuit board.
-Four 1N4001 diodes, or similar. Diode bridge.
- Voltage stabilizer LM7812.
-Low-power step-down transformer for 220 V, the secondary winding should have 14V - 35V alternating voltage, with a load current from 100 mA to 1A, depending on how much power is needed at the output.
-Electrolytic capacitor with a capacity of 1000 µF - 4700 µF.
-Capacitor with a capacity of 1uF.
-Two 100nF capacitors.
-Cuttings of installation wire.
-Radiator, if necessary.
If you need to get maximum power from the power source, you need to prepare an appropriate transformer, diodes and a heatsink for the chip.
Step 2: Tools....
To make a block, you need the following installation tools:
-Soldering iron or Soldering Station
-Pliers
-Installation tweezers
- Wire strippers
-Device for solder suction.
-Screwdriver.
And other tools that may be useful.
Step 3: Diagram and others...


To obtain 5 volt stabilized power, you can replace the LM7812 stabilizer with an LM7805.
To increase the load capacity to more than 0.5 amperes, you will need a heatsink for the microcircuit, otherwise it will fail due to overheating.
However, if you need to get several hundred milliamps (less than 500 mA) from the source, then you can do without a radiator, the heating will be negligible.
In addition, an LED has been added to the circuit to visually verify that the power supply is working, but you can do without it.

Power supply circuit 12V 30A.
When using one 7812 stabilizer as a voltage regulator and several powerful transistors, this power supply is capable of providing an output load current of up to 30 amperes.
Perhaps the most expensive part of this circuit is the power step-down transformer. The voltage of the secondary winding of the transformer must be several volts higher than the stabilized voltage of 12V to ensure the operation of the microcircuit. It must be borne in mind that you should not strive for a larger difference between the input and output voltage values, since at such a current the heat sink of the output transistors increases significantly in size.
In the transformer circuit, the diodes used must be designed for a high maximum forward current, approximately 100A. The maximum current flowing through the 7812 chip in the circuit will not be more than 1A.
Six composite transistors Darlington type TIP2955 connected in parallel provide a load current of 30A (each transistor is designed for a current of 5A), such a large current requires an appropriate size of the radiator, each transistor passes through one sixth of the load current.
A small fan can be used to cool the radiator.
Checking the power supply
When you turn it on for the first time, it is not recommended to connect a load. We check the functionality of the circuit: connect a voltmeter to the output terminals and measure the voltage, it should be 12 volts, or the value is very close to it. Next, we connect a 100 Ohm load resistor with a dissipation power of 3 W, or a similar load - such as an incandescent lamp from a car. In this case, the voltmeter reading should not change. If there is no 12 volt voltage at the output, turn off the power and check the correct installation and serviceability of the elements.
Before installation, check the serviceability of the power transistors, since if the transistor is broken, the voltage from the rectifier goes directly to the output of the circuit. To avoid this, check the power transistors for short circuits; to do this, use a multimeter to separately measure the resistance between the collector and emitter of the transistors. This check must be carried out before installing them in the circuit.

Power supply 3 - 24V

The power supply circuit gives adjustable voltage in the range from 3 to 25 volts, with a maximum load current of up to 2A, if you reduce the current-limiting resistor to 0.3 ohms, the current can be increased to 3 amperes or more.
Transistors 2N3055 and 2N3053 are installed on the corresponding radiators; the power of the limiting resistor must be at least 3 W. Voltage regulation is controlled by an LM1558 or 1458 op amp. When using a 1458 op amp, it is necessary to replace the stabilizer elements that supply voltage from pin 8 to 3 of the op amp from a divider on resistors rated 5.1 K.
The maximum DC voltage for powering op-amps 1458 and 1558 is 36 V and 44 V, respectively. Power transformer must produce a voltage at least 4 volts higher than the stabilized output voltage. The power transformer in the circuit has an output voltage of 25.2 volts alternating current with a branch in the middle. When switching windings, the output voltage decreases to 15 volts.

1.5 V power supply circuit

The power supply circuit to obtain a voltage of 1.5 volts uses a step-down transformer, a bridge rectifier with a smoothing filter and an LM317 chip.

Diagram of an adjustable power supply from 1.5 to 12.5 V

Power supply circuit with output voltage regulation to obtain voltage from 1.5 volts to 12.5 volts; the LM317 microcircuit is used as a regulating element. It must be installed on the radiator, on an insulating gasket to prevent a short circuit to the housing.

Power supply circuit with fixed output voltage

Power supply circuit with a fixed output voltage of 5 volts or 12 volts. The LM 7805 chip is used as an active element, LM7812 is installed on a radiator to cool the heating of the case. The choice of transformer is shown on the left on the plate. By analogy, you can make a power supply for other output voltages.

20 Watt power supply circuit with protection

The circuit is designed for a small transceiver homemade, by DL6GL. When developing the unit, the goal was to have an efficiency of at least 50%, a nominal supply voltage of 13.8V, maximum 15V, for a load current of 2.7A.
According to what scheme: pulse source power supply or linear?
Switching power supplies are small-sized and have good efficiency, but it is unknown how they will behave in a critical situation, surges in the output voltage...
Despite the shortcomings, a linear control scheme was chosen: a fairly large transformer, not high efficiency, cooling required, etc.
Parts from homemade block 1980s power supply: radiator with two 2N3055. The only thing missing was a µA723/LM723 voltage regulator and a few small parts.
The voltage regulator is assembled on a µA723/LM723 microcircuit with standard inclusion. Output transistors T2, T3 type 2N3055 are installed on radiators for cooling. Using potentiometer R1, the output voltage is set within 12-15V. Using variable resistor R2, the maximum voltage drop across resistor R7 is set, which is 0.7V (between pins 2 and 3 of the microcircuit).
A toroidal transformer is used for the power supply (can be any at your discretion).
On the MC3423 chip, a circuit is assembled that is triggered when the voltage (surge) at the output of the power supply is exceeded, by adjusting R3 the voltage threshold is set on leg 2 from the divider R3/R8/R9 (2.6V reference voltage), the voltage that opens the thyristor BT145 is supplied from output 8, causing a short circuit leading to tripping of fuse 6.3a.

To prepare the power supply for operation (the 6.3A fuse is not yet involved), set the output voltage to, for example, 12.0V. Load the unit with a load; for this you can connect a 12V/20W halogen lamp. Set R2 so that the voltage drop is 0.7V (the current should be within 3.8A 0.7=0.185Ωx3.8).
We configure the operation of the overvoltage protection; to do this, we smoothly set the output voltage to 16V and adjust R3 to trigger the protection. Next, we set the output voltage to normal and install the fuse (before that we installed a jumper).
The described power supply can be reconstructed for more powerful loads; to do this, install a more powerful transformer, additional transistors, wiring elements, and a rectifier at your discretion.

Homemade 3.3v power supply

If you need a powerful power supply of 3.3 volts, then it can be made by converting an old power supply from a PC or using the above circuits. For example, replace a 47 ohm resistor of a higher value in the 1.5 V power supply circuit, or install a potentiometer for convenience, adjusting it to the desired voltage.

Transformer power supply on KT808

Many radio amateurs still have old Soviet radio components that are lying around idle, but which can be successfully used and they will serve you faithfully for a long time, one of the well-known UA1ZH circuits that is floating around the Internet. Many spears and arrows are broken on forums when discussing which is better field-effect transistor or ordinary silicon or germanium, what temperature of crystal heating will they withstand and which one is more reliable?
Each side has its own arguments, but you can get the parts and make another simple and reliable power supply. The circuit is very simple, protected from overcurrent, and when three KT808 are connected in parallel, it can produce a current of 20A; the author used such a unit with 7 parallel transistors and delivered 50A to the load, while the filter capacitor capacity was 120,000 uF, the voltage of the secondary winding was 19V. It must be taken into account that the relay contacts must switch such a large current.

Given that correct installation, output voltage drop does not exceed 0.1 volt

Power supply for 1000V, 2000V, 3000V

If we need to have a high voltage DC source to power the transmitter output stage lamp, what should we use for this? On the Internet there are many different power supply circuits for 600V, 1000V, 2000V, 3000V.
First: for high voltage, circuits with transformers for both one phase and three phases are used (if there is a three-phase voltage source in the house).
Second: to reduce size and weight, they use a transformerless power supply circuit, directly a 220-volt network with voltage multiplication. The biggest drawback of this circuit is that there is no galvanic isolation between the network and the load, as the output is connected to a given voltage source, observing phase and zero.

The circuit has a step-up anode transformer T1 (for the required power, for example 2500 VA, 2400V, current 0.8 A) and a step-down filament transformer T2 - TN-46, TN-36, etc. To eliminate current surges during switching on and protection diodes when charging capacitors, switching is used through quenching resistors R21 and R22.
The diodes in the high-voltage circuit are shunted by resistors in order to uniformly distribute Urev. Calculation of the nominal value using the formula R(Ohm) = PIVx500. C1-C20 to eliminate white noise and reduce surge voltages. You can also use bridges like KBU-810 as diodes by connecting them according to the specified circuit and, accordingly, taking the required amount, not forgetting about shunting.
R23-R26 for discharging capacitors after a power outage. To equalize the voltage on series-connected capacitors, equalizing resistors are placed in parallel, which are calculated from the ratio for every 1 volt there are 100 ohms, but at high voltage the resistors are sufficient high power and here we have to maneuver, taking into account that the tension idle move more by 1.41.

More on the topic

Transformer power supply 13.8 volts 25 A for a HF transceiver with your own hands.

Repair and modification of the Chinese power supply to power the adapter.

Prologue.

I have two multimeters, and both have the same drawback - they are powered by a 9-volt Krona battery.

I always tried to have a fresh 9-volt battery in stock, but for some reason, when it was necessary to measure something with an accuracy higher than that of a pointer instrument, the Krona turned out to be either inoperative or only lasted for a few hours of operation.

The procedure for winding a pulse transformer.

It is very difficult to wind a gasket onto a ring core of such small dimensions, and winding a wire onto a bare core is inconvenient and dangerous. The wire insulation may be damaged by the sharp edges of the ring.

To prevent the turns from running apart when laying the wire, it is useful to cover the core with a thin layer of “88N” glue and dry it before winding.

First, the secondary windings III and IV are wound (see converter diagram). They need to be wound into two wires at once. The coils can be secured with glue, for example, “BF-2” or “BF-4”.

I did not have a suitable wire, and instead of a wire with a calculated diameter of 0.16 mm, I used a wire with a diameter of 0.18 mm, which led to the formation of a second layer of several turns.

Then, also in two wires, primary windings I and II are wound. The turns of the primary windings can also be secured with glue.

I assembled the converter using the hinged mounting method, having previously connected the transistors, capacitors and transformer with cotton thread.

The input, output and common bus of the converter were connected with a flexible stranded wire.

Setting up the converter.

Tuning may be required to set the desired output voltage level.

I selected the number of turns so that at a battery voltage of 1.0 Volts, the output of the converter would be about 7 Volts. At this voltage, the low battery indicator lights up in the multimeter. This way you can prevent the battery from being discharged too deeply.

If instead of the proposed KT209K transistors, others are used, then the number of turns of the secondary winding of the transformer will have to be selected. This is due to the different magnitude of the voltage drop across p-n junctions at various types transistors.

I tested this circuit using KT502 transistors with unchanged transformer parameters. The output voltage dropped by a volt or so.

If generation does not occur, check the phasing of all coils. The dots on the converter diagram (see above) mark the beginning of each winding.

To avoid confusion when phasing the coils of the ring magnetic circuit, take as the beginning of all windings, For example, all leads coming out from the bottom, and beyond the end of all windings, all leads coming out from the top.

Final assembly of a pulse voltage converter.

Before final assembly, all elements of the circuit were connected with stranded wire, and the circuit's ability to receive and transmit energy was tested.

To prevent short circuits, the pulse voltage converter was insulated on the contact side with silicone sealant.

Then all the structural elements were placed in the Krona body. To prevent the front cover with the connector from being recessed inside, a celluloid plate was inserted between the front and back walls. After which, the back cover was secured with “88N” glue.

To charge the modernized Krona, we had to make an additional cable with a 3.5mm jack plug at one end. At the other end of the cable, to reduce the likelihood of a short circuit, standard device sockets were installed instead of similar plugs.

Refinement of the multimeter.

The DT-830B multimeter immediately started working with the upgraded Krona. But the M890C+ tester had to be slightly modified.

The fact is that most modern multimeters have an automatic power-off function. The picture shows part of the multimeter control panel where this function is indicated.

The Auto Power Off circuit works as follows. When the battery is connected, capacitor C10 is charged. When the power is turned on, while capacitor C10 is discharged through resistor R36, the output of comparator IC1 is held at a high potential, which causes transistors VT2 and VT3 to turn on. Through the open transistor VT3, the supply voltage enters the multimeter circuit.

As you can see, for normal operation of the circuit, you need to supply power to C10 even before the main load turns on, which is impossible, since our modernized “Krona”, on the contrary, will turn on only when the load appears.

In general, the whole modification consisted of installing an additional jumper. For her, I chose the place where it was most convenient to do this.

Unfortunately, the element designations on electrical diagram did not match the markings on the printed circuit board of my multimeter, so I found the points for installing the jumper this way. By dialing, I identified the required output of the switch, and identified the +9V power bus using the 8th leg of the operational amplifier IC1 (L358).

Small details.

It was difficult to purchase just one battery. They are mostly sold either in pairs or in groups of four. However, some kits, for example, “Varta”, come with five batteries in a blister. If you are as lucky as I am, you will be able to share such a set with someone. I bought the battery for only $3.3, while one “Krona” costs from $1 to $3.75. There are, however, also “Crowns” for $0.5, but they are completely stillborn.