Power supply 0 30V. Radio for everyone - LBP unipolar. LM317T AC Voltage Regulator

Today we will collect laboratory block DIY food. We will understand the structure of the block, select the right components, learn how to solder correctly, and assemble elements onto printed circuit boards.

This is a high-quality laboratory (and not only) power supply with variable adjustable voltage from 0 to 30 volts. The circuit also includes an electronic output current limiter that effectively regulates the output current to 2 mA from the circuit's maximum current of 3 A. This characteristic makes this power supply indispensable in the laboratory, as it makes it possible to regulate power, limit the maximum current that the connected device can consume, without fear of damage if something goes wrong.
There is also a visual indication that this limiter is in effect (LED) so you can see if your circuit is exceeding its limits.

The schematic diagram of the laboratory power supply is presented below:

Technical characteristics of laboratory power supply

Input voltage: ……………. 24 V-AC;
Input current: ……………. 3 A (max);
Output voltage: …………. 0-30 V - adjustable;
Output current: …………. 2 mA -3 A - adjustable;
Output voltage ripple: .... 0.01% maximum.

Peculiarities

- Small size, easy to make, simple design.
— Output voltage is easily adjustable.
— Output current limitation with visual indication.
— Protection against overload and incorrect connection.

Principle of operation

Let's start with the fact that the laboratory power supply uses a transformer with a secondary winding of 24V/3A, which is connected through input terminals 1 and 2 (the quality of the output signal is proportional to the quality of the transformer). The AC voltage from the secondary winding of the transformer is rectified by a diode bridge formed by diodes D1-D4. The ripples of the rectified DC voltage at the output of the diode bridge are smoothed by a filter formed by resistor R1 and capacitor C1. The circuit has some features that make this power supply different from other units in its class.

Instead of using feedback To control the output voltage, our circuit uses an operational amplifier to provide the required voltage for stable operation. This voltage drops at the output of U1. The circuit operates thanks to the D8 - 5.6 V Zener diode, which here operates at zero temperature coefficient of current. The voltage at the output of U1 drops across the diode D8 turning it on. When this happens, the circuit stabilizes and the voltage of the diode (5.6) drops across resistor R5.

The current that flows through the opera. the amplifier changes slightly, which means the same current will flow through resistors R5, R6, and since both resistors have the same voltage value, the total voltage will be summed up as if serial connection. Thus, the voltage obtained at the output of the opera. amplifier will be equal to 11.2 volts. Chain from oper. amplifier U2 has a constant gain of approximately 3, according to the formula A = (R11 + R12) / R11 increases the voltage of 11.2 volts to approximately 33 volts. Trimmer RV1 and resistor R10 are used to set the voltage output so that it does not drop to 0 volts, regardless of the value of other components in the circuit.

Another very important characteristic of the circuit is the ability to obtain the maximum output current that can be obtained from the p.s.u. To make this possible, the voltage drops across a resistor (R7), which is connected in series with the load. The IC responsible for this circuit function is U3. An inverted signal to input U3 equal to 0 volts is supplied through R21. At the same time, without changing the signal of the same IC, you can set any voltage value through P2. Let's say that for a given output the voltage is several volts, P2 is set so that there is a signal of 1 volt at the input of IC. If the load is increased output voltage will be constant and having R7 in series with the output will have little effect due to its low magnitude and due to its position outside the control circuit's feedback loop. As long as the load and output voltage are constant, the circuit operates stably. If the load is increased so that the voltage on R7 is greater than 1 volt, U3 is turned on and stabilizes to its original parameters. U3 operates without changing the signal to U2 through D9. Thus, the voltage through R7 is constant and does not increase above a predetermined value (1 volt in our example), reducing the output voltage of the circuit. This device is capable of maintaining the output signal constant and accurate, which makes it possible to obtain 2 mA at the output.

Capacitor C8 makes the circuit more stable. Q3 is needed to control the LED whenever you use the limiter indicator. To make this possible for U2 (changing the output voltage down to 0 volts) it is necessary to provide a negative connection, which is done through the circuit C2 and C3. The same negative connection is used for U3. Negative voltage is supplied and stabilized by R3 and D7.

To avoid uncontrollable situations, there is a kind of protection circuit built around Q1. The IC is internally protected and cannot be damaged.

U1 is a reference voltage source, U2 is a voltage regulator, U3 is a current stabilizer.

Power supply design.

First of all, let's look at the basics of building electronic circuits on printed circuit boards - the basics of any laboratory power supply. The board is made of a thin insulating material covered with a thin conductive layer of copper, which is formed so that the circuit elements can be connected by conductors as shown in schematic diagram. Needs to be designed correctly printed circuit board to avoid malfunction of the device. To protect the board from oxidation in the future and keep it in excellent condition, it must be coated with a special varnish that protects against oxidation and makes soldering easier.
Soldering elements into a board - the only way Assemble a laboratory power supply efficiently and the success of your work will depend on how you do it. This is not very difficult if you follow a few rules and then you will not have any problems. The power of the soldering iron you use should not exceed 25 watts. The tip should be thin and clean throughout the entire operation. To do this, there is a damp sponge of sorts and from time to time you can clean the hot tip to remove all the residues that accumulate on it.

DO NOT attempt to clean a dirty or worn tip with a file or sandpaper. If it cannot be cleaned, replace it. There are many different types of soldering irons on the market, and you can also buy a good flux to get a good connection when soldering.
DO NOT use flux if you are using solder that already contains it. A large amount of flux is one of the main causes of circuit failure. If, however, you must use additional flux as when tinning copper wires, you must clean the work surface after finishing the job.

In order to solder the element correctly, you must do the following:
— Clean the terminals of the elements with sandpaper (preferably with a small grain).
— Bend component leads at the correct distance from the housing exit to convenient location on the board.
— You may encounter elements whose leads are thicker than the holes in the board. In this case, you need to widen the holes a little, but do not make them too large - this will make soldering difficult.
— The element must be inserted so that its leads protrude slightly from the surface of the board.
- When the solder melts, it will spread evenly throughout the entire area around the hole (this can be achieved by using the correct soldering iron temperature).
— Soldering one element should take no more than 5 seconds. Remove excess solder and wait until the solder on the board cools naturally (without blowing on it). If everything was done correctly, the surface should have a bright metallic tint, the edges should be smooth. If the solder appears dull, cracked, or bead-shaped, it is called dry soldering. You must delete it and do everything again. But be careful not to overheat the traces, otherwise they will lag behind the board and break easily.
— When you solder a sensitive element, you need to hold it with metal tweezers or tongs, which will absorb excess heat so as not to burn the element.
- When you complete your job, trim off the excess from the element leads and you can clean the board with alcohol to remove any remaining flux.

Before you start assembling the power supply, you need to find all the elements and divide them into groups. First, install the ICs sockets and external connections pins and solder them in place. Then resistors. Be sure to place R7 at a certain distance from the PCB as it gets very hot, especially when high current is flowing, and this can damage it. This is also recommended for R1. then place the capacitors not forgetting the polarity of the electrolytic and finally solder the diodes and transistors, but be careful not to overheat them and solder them as shown in the diagram.
Install the power transistor in the heatsink. To do this you need to follow the diagram and remember to use an insulator (mica) between the transistor body and the heatsink and a special cleaning fiber to insulate the screws from the heatsink.

Connect an insulated wire to each terminal, being careful to make a good quality connection as there is a lot of current flowing here, especially between the emitter and collector of the transistor.
Also, when assembling the power supply, it would be nice to estimate where each element will be located, in order to calculate the length of the wires that will be between the PCB and the potentiometers, the power transistor and for the input and output connections.
Connect the potentiometers, LED and power transistor and connect two pairs of ends for input and output connections. Make sure from the diagram that you are doing everything correctly, try not to confuse anything, since there are 15 external connections in the circuit and if you make a mistake, it will be difficult to find it later. It would also be a good idea to use wires of different colors.

Printed circuit board of a laboratory power supply, below there will be a link to download the signet in .lay format:

Layout of elements on the power supply board:

Connection diagram of variable resistors (potentiometers) to regulate the output current and voltage, as well as connection of the contacts of the power transistor of the power supply:

Designation of transistor and operational amplifier pins:

Terminal designations on the diagram:
— 1 and 2 to the transformer.
— 3 (+) and 4 (-) DC OUTPUT.
- 5, 10 and 12 on P1.
- 6, 11 and 13 on P2.
- 7 (E), 8 (B), 9 (E) to transistor Q4.
— LED must be installed on the outside of the board.

When all external connections are made, you need to check the board and clean it to remove any remaining solder. Make sure there is no connection between adjacent tracks that could lead to a short circuit and if everything is fine, connect the transformer. And connect the voltmeter.
DO NOT TOUCH ANY PORTION OF THE CIRCUIT WHILE IT IS LIVE.
The voltmeter should show a voltage between 0 and 30 volts depending on the position of P1. Turning P2 counterclockwise should turn on the LED, indicating that our limiter is working.

List of elements.

R1 = 2.2 kOhm 1W
R2 = 82 Ohm 1/4W
R3 = 220 Ohm 1/4W
R4 = 4.7 kOhm 1/4W
R5, R6, R13, R20, R21 = 10 kOhm 1/4W
R7 = 0.47 Ohm 5W
R8, R11 = 27 kOhm 1/4W
R9, R19 = 2.2 kOhm 1/4W
R10 = 270 kOhm 1/4W
R12, R18 = 56kOhm 1/4W
R14 = 1.5 kOhm 1/4W
R15, R16 = 1 kOhm 1/4W
R17 = 33 Ohm 1/4W
R22 = 3.9 kOhm 1/4W
RV1 = 100K trimmer
P1, P2 = 10KOhm linear potentiometer
C1 = 3300 uF/50V electrolytic
C2, C3 = 47uF/50V electrolytic
C4 = 100nF polyester
C5 = 200nF polyester
C6 = 100pF ceramic
C7 = 10uF/50V electrolytic
C8 = 330pF ceramic
C9 = 100pF ceramic
D1, D2, D3, D4 = 1N5402,3,4 diode 2A - RAX GI837U
D5, D6 = 1N4148
D7, D8 = 5.6V Zener
D9, D10 = 1N4148
D11 = 1N4001 diode 1A
Q1 = BC548, NPN transistor or BC547
Q2 = 2N2219 NPN transistor - (Replace with KT961A- everything is working)
Q3 = BC557, PNP transistor or BC327
Q4 = 2N3055 NPN power transistor ( replace with KT 827A)
U1, U2, U3 = TL081, op. amplifier
D12 = LED diode

As a result, I assembled a laboratory power supply myself, but in practice I encountered something that I considered necessary to correct. Well, first of all, this is a power transistor Q4 = 2N3055 it urgently needs to be crossed out and forgotten. I don’t know about other devices, but it is not suitable for this regulated power supply. The fact is that this type transistors fail instantly when short-circuited and the current of 3 amperes does not draw at all!!! I didn’t know what was wrong until I changed it to our native Soviet one KT 827 A. After installing it on the radiator, I didn’t know any grief and never returned to this issue.

As for the rest of the circuitry and parts, there are no difficulties. With the exception of the transformer, we had to wind it. Well, this is purely because of greed, half a bucket of them is in the corner - don’t buy it =))

Well, in order not to break the good old tradition, I am posting the result of my work for the general court :) I had to play around with the column, but overall it turned out not bad:

The front panel itself - I moved the potentiometers to left side on the right there is an ammeter and a voltmeter + a red LED to indicate the current limit.

The next photo shows the rear view. Here I wanted to show how to install a cooler with a radiator from motherboard. A power transistor is placed on the back side of this radiator.

Here it is, the KT 827 A power transistor. Mounted on the rear wall. I had to drill holes for the legs, lubricate all contact parts with heat-conducting paste and secure them with nuts.

Here they are....the insides! Actually everything is in a heap!

Slightly larger inside the body

Front panel on the other side

Taking a closer look, you can see how the power transistor and transformer are mounted.

Power supply board on top; Here I cheated and packed low-power transistors at the bottom of the board. They are not visible here, so don't be surprised if you don't find them.

Here is the transformer. I rewound it to 25 volts of the TVS-250 output voltage. Rough, sour, not aesthetically pleasing, but everything works like a clock =) I didn’t use the second part. Left room for creativity.

Somehow like this. A little creativity and patience. The unit has been working great for 2 years now. To write this article I had to disassemble it and reassemble it. It's just awful! But everything is for you, dear readers!

Designs from our readers!

Characteristics of the power supply: Output voltage is adjustable from 0 to 30 volts. Output current 5 amperes. The voltage drop at a current of 1 to 6 amperes is negligible and is not reflected in the output indicators. This power supply contains three main units: an internal power supply unit VD1-VD4, C1-C7, DA1, DA2, an overload and short-circuit protection unit on VS1, R1-R4, VD3 and the main unit - an adjustable voltage stabilizer VT2-VT7, VD4-VD5, R4-R14, C8. Diode HL1 indicates overcurrent or short circuit in the load.

The main unit is an adjustable voltage stabilizer of the compensation type. It contains an input differential stage on transistors VT5, VT7, two amplification stages on transistors VT3 and VT2, and a control transistor VT 1. Elements VT4, VT6, VD4, VD5, R5 - R8, R10 form current stabilizers. Capacitor C8 prevents self-excitation of the unit. The output voltage is regulated by resistor R13. The upper voltage limit is set by trimming resistor R14. Construction and details. The power of transformer T1 must be at least 100 - 160 watts, the current of winding II must be at least 4 - 6 amperes. Winding current III is within 1...2 amperes. Transistor VT1 should be installed on finned aluminum radiators with an area of more than 1450 sq.cm. Resistor R4 is selected experimentally, based on the protection operation current.
Resistors R 7 and R 14 are multi-turn SP5-2. Resistor - R13 any variable. Microcircuits DA1 and DA2 can be replaced with similar domestic ones KR142EN5A and KR1162EN5A. Their power allows a stabilized voltage of ± 5 volts to power external loads with a current consumption of up to 1 ampere. This load is a digital panel, which is used for digital indication of voltage and current in power supplies. If you do not use a digital panel, then DA1 and DA2 chips can be replaced with 78L05 and 79L05 chips. Diodes VD3 - VD5 can be replaced with KD522B diodes. The digital panel consists of an input voltage and current divider, a KR572PV2A microcircuit and an indication of four seven-segment LED indicators. Resistor R4 of the digital panel consists of two pieces of constantan wire = 1 mm and 50 mm long. The difference in resistor value should exceed 15 - 20%. Resistors R2 and R6 brand SP5-2 and SP5-16VA. P2K type voltage and current indication mode switch. The KR572PV2A microcircuit is a converter with 3.5 decimal places, operating on the principle of sequential counting with double integration, with automatic zero correction and determination of the polarity of the input signal. Imported LEDs were used for display seven segment indicators KINGBRIGT DA56 - 11 SRWA with common anode. It is advisable to use film capacitors C2 - C4 of type K73-17. Instead of imported seven-segment LEDs, you can use domestic ones with a common anode of the ALS324B type.
All radio components of the device:
VD1 - VD4 - RS600
VD5 - VD8 - KS407A
VD9 - AL307B
VD10 - KD102A
VD11 - 1N4148
VD12 - 1N4148
C1 - 10000 uF x 50 volts
C2 - 100 µF
C3 - 100 µF
C4 - 10 µF
C5 - 10 µF
C6 - 10 n
C7 - 10n
C8 - 33 n
R1 - 330 Ohm
R2 - 3 kOhm
R3 - 33 Ohm
R4 - 2.4 kOhm
R5 - 150 Ohm
R6 - 2.2 kOhm
R7 - 10 kOhm
R8 - 330 kOhm
R9 - 6.8 kOhm
R10 - 1 kOhm
R11 - 5.1 kOhm
R12 - 5.1 kOhm
R13 - 10 kOhm
R14 - 2.2 kOhm
VT1 - KT827A
VT2 - KT815G
VT3 - KT3107A
VT4 - KT3102A
VT5 - KT315D
VT6 - KT315D
VT7 - KT315D

After turning on the power and error-free installation, if the parts are in working order, the indication segments HG1-HG3 should light up. Using a voltmeter, resistor R2 at pin 36 of the KR572PV2 microcircuit sets the voltage to 1 volt. The power supply is connected to legs (a) and (b). At the output of the power supply, set the voltage to 5...15 volts and select a resistor R 10 (roughly), replacing it, temporarily, with a variable one.

Using resistor R8, a more accurate voltage reading is established. After that, a variable resistor with a power of 10 ... 30 watts is connected to the output of the power supply, the current is set to 1 ampere using the ammeter, and the value on the indicator is set with resistor R 6. The reading should be 1.00. At a current of 500 mA - 0.50, at a current of 50 mA - 0.05. Thus, the indicator can indicate a current of 10 mA, that is, 0.01.
The maximum current indication value is 9.99 amperes. For a larger display capacity, you can use the circuit on the KR572PV6. Contact pads U and I on the printed circuit board of the digital panel are connected using flexible conductors to the points of the corresponding indicators HG 2 and HG 1. The KR572PV2A microcircuit can be replaced with an imported ICL7107CPL microcircuit.

The DIY laboratory power supply built according to a standard scheme, however, with a not entirely standard connection of the LM723 voltage regulator. As a result of this connection, it was possible to achieve that at the output of the power supply, the lower level of the output voltage is only 30 mV, which can actually be considered zero.

Description of a powerful laboratory power supply based on LM723

Technical parameters of laboratory power supply

Output voltage: 0 - 30 volts.
Maximum load current: 4 amperes.

It is recommended to use a composite transistor VT2. Resistance R10 sets the upper level of the output voltage. The short circuit protection unit is built on transistors of different conductivities and, in fact, are an alternative to a thyristor. Resistance R1 sets the threshold for overcurrent protection. In some cases, you may have to select resistance R4.

Resistance R4 - 5 watts at 0.22 ohms. The protection unit protects the laboratory power supply from both short circuit and overcurrent. Resistance R8 is used with a linear dependence.

Many amateur radio power supplies (PS) are made on KR142EN12, KR142EN22A, KR142EN24, etc. microcircuits. The lower limit of adjustment of these microcircuits is 1.2...1.3 V, but sometimes a voltage of 0.5...1 V is necessary. The author offers several technical solutions PSU based on microcircuit data.

The integrated circuit (IC) KR142EN12A (Fig. 1) is an adjustable compensation-type voltage stabilizer in the KT-28-2 package, which allows you to power devices with a current of up to 1.5 A in the voltage range 1.2...37 V. This integrated circuit The stabilizer has thermally stable current protection and output short circuit protection.

Rice. 1. IC KR142EN12A

Based on the KR142EN12A IC, you can build an adjustable power supply, the circuit of which (without a transformer and diode bridge) is shown in Fig. 2. The rectified input voltage is supplied from the diode bridge to capacitor C1. Transistor VT2 and chip DA1 should be located on the radiator. Heat sink flange DA1 is electrically connected to pin 2, so if DA1 and transistor VD2 are located on the same radiator, then they need to be isolated from each other. In the author's version, DA1 is installed on a separate small radiator, which is not galvanically connected to the radiator and transistor VT2.

Rice. 2. Adjustable power supply on IC KR142EN12A

The power dissipated by a chip with a heat sink should not exceed 10 W. Resistors R3 and R5 form a voltage divider included in the measuring element of the stabilizer, and are selected according to the formula:

U out = U out.min (1 + R3/R5).

A stabilized negative voltage of -5 V is supplied to capacitor C2 and resistor R2 (used to select the thermally stable point VD1). In the author’s version, the voltage is supplied from the KTs407A diode bridge and the 79L05 stabilizer, powered from a separate winding of the power transformer.

To protect against short circuits in the output circuit of the stabilizer, it is enough to connect resistor R3 in parallel electrolytic capacitor with a capacity of at least 10 μF, and resistor R5 is shunted with a KD521A diode. The location of the parts is not critical, but for good temperature stability it is necessary to use the appropriate types of resistors. They should be located as far as possible from heat sources. The overall stability of the output voltage consists of many factors and usually does not exceed 0.25% after warming up.

After turning on and warming up the device, the minimum output voltage of 0 V is set with resistor Rext. Resistors R2 (Fig. 2) and resistor Rext (Fig. 3) must be multi-turn trimmers from the SP5 series.

Rice. 3. Connection diagram Rext

The current capabilities of the KR142EN12A microcircuit are limited to 1.5 A. Currently, there are microcircuits on sale with similar parameters, but designed for a higher load current, for example LM350 - for a current of 3 A, LM338 - for a current of 5 A. Data on these microcircuits can be found on the National Semiconductor website.

Recently, imported microcircuits from the LOW DROP series (SD, DV, LT1083/1084/1085) have appeared on sale. These microcircuits can operate at reduced voltage between input and output (up to 1...1.3 V) and provide a stabilized output voltage in the range of 1.25...30 V at a load current of 7.5/5/3 A respectively. The closest domestic analogue in terms of parameters, type KR142EN22, has a maximum stabilization current of 7.5 A.

At the maximum output current, the stabilization mode is guaranteed by the manufacturer with an input-output voltage of at least 1.5 V. The microcircuits also have built-in protection against excess current in the load of the permissible value and thermal protection against overheating of the case.

These stabilizers provide output voltage instability of 0.05%/V, output voltage instability when the output current changes from 10 mA to a maximum value of no worse than 0.1%/V.

In Fig. Figure 4 shows a power supply circuit for a home laboratory, which allows you to do without transistors VT1 and VT2, shown in Fig. 2. Instead of the DA1 KR142EN12A microcircuit, the KR142EN22A microcircuit was used. This is an adjustable stabilizer with a low voltage drop, allowing you to obtain a current of up to 7.5 A in the load.

The maximum power dissipation at the output of the stabilizer Pmax can be calculated using the formula:

P max = (U in - U out) I out,
where Uin is the input voltage supplied to the DA3 microcircuit, Uout is the output voltage at the load, Iout is the output current of the microcircuit.

For example, the input voltage supplied to the microcircuit is U in = 39 V, the output voltage at the load U out = 30 V, the current at the load I out = 5 A, then the maximum power dissipated by the microcircuit at the load is 45 W.

Electrolytic capacitor C7 is used to reduce the output impedance by high frequencies, and also reduces the noise voltage level and improves ripple smoothing. If this capacitor is tantalum, then its nominal capacity must be at least 22 μF, if aluminum - at least 150 μF. If necessary, the capacitance of capacitor C7 can be increased.

If the electrolytic capacitor C7 is located at a distance of more than 155 mm and is connected to the power supply with a wire with a cross-section of less than 1 mm, then an additional electrolytic capacitor with a capacity of at least 10 μF is installed on the board parallel to the capacitor C7, closer to the microcircuit itself.

The capacitance of filter capacitor C1 can be determined approximately at the rate of 2000 μF per 1 A of output current (at a voltage of at least 50 V). To reduce the temperature drift of the output voltage, resistor R8 must be either wire-wound or metal-foil with an error of no worse than 1%. Resistor R7 is the same type as R8. If the KS113A zener diode is not available, you can use the unit shown in Fig. 3. The author is quite satisfied with the protection circuit solution given in , as it works flawlessly and has been tested in practice. You can use any power supply protection circuit solutions, for example those proposed in. In the author’s version, when relay K1 is triggered, contacts K1.1 close, short-circuiting resistor R7, and the voltage at the power supply output becomes 0 V.

The printed circuit board of the power supply and the arrangement of elements are shown in Fig. 5, the appearance of the power supply is in Fig. 6. Dimensions of the printed circuit board are 112x75 mm. The radiator chosen is needle-shaped. The DA3 chip is isolated from the radiator by a gasket and attached to it using a steel spring plate that presses the chip to the radiator.

Rice. 5. Printed circuit board of the power supply and arrangement of elements

Capacitor C1 type K50-24 is made up of two parallel-connected capacitors with a capacity of 4700 μFx50 V. You can use an imported analogue of a capacitor type K50-6 with a capacity of 10000 μFx50 V. The capacitor should be located as close to the board as possible, and the conductors connecting it to the board should be as short as possible. Capacitor C7 manufactured by Weston with a capacity of 1000 μFx50 V. Capacitor C8 is not shown in the diagram, but there are holes for it on the printed circuit board. You can use a capacitor with a nominal value of 0.01...0.1 µF for a voltage of at least 10...15 V.

Rice. 6. Appearance BP

Diodes VD1-VD4 are an imported RS602 diode microassembly, designed for a maximum current of 6 A (Fig. 4). The power supply protection circuit uses the RES10 relay (passport RS4524302). In the author's version, resistor R7 of the SPP-ZA type is used with a spread of parameters of no more than 5%. Resistor R8 (Fig. 4) should have a spread from the specified value of no more than 1%.

The power supply usually does not require configuration and starts working immediately after assembly. After warming up the block, resistor R6 (Fig. 4) or resistor Radd (Fig. 3) is set to 0 V at the nominal value of R7.

This design uses a power transformer of the OSM-0.1UZ brand with a power of 100 W. Magnetic core ШЛ25/40-25. Primary winding contains 734 turns of 0.6 mm PEV wire, winding II - 90 turns of 1.6 mm PEV wire, winding III - 46 turns of 0.4 mm PEV wire with a tap from the middle.

The RS602 diode assembly can be replaced with diodes rated for a current of at least 10 A, for example, KD203A, V, D or KD210 A-G (if you do not place the diodes separately, you will have to remake the printed circuit board). Transistor KT361G can be used as transistor VT1.

Literature

national.com/catalog/AnalogRegulators_LinearRegulators-Standardn-p-n_PositiveVoltageAdjutable.html
Morokhin L. Laboratory power supply//Radio. - 1999 - No. 2
Nechaev I. Protection of small-sized network power supplies from overloads//Radio. - 1996.-№12

I needed a high-quality power supply to test amplifiers, which I am a big fan of assembling. The amplifiers are different, the power supply is different. Output: you need to make a laboratory power supply with an adjustable output voltage from 0 to 30 Volts.
And in order to experiment safely for health and for hardware ( powerful transistors not cheap) the power supply must also regulate the load current.
So, what I wanted from my PSU:
1. Short circuit protection
2. Current limitation according to the set limit
3. Smoothly adjustable output voltage
4. Bipolarity (0-30V; 0.002-3A)

Here is one of the latest amplifiers - Lanzar. It's quite powerful
I started making LBP for my home laboratory using it