Power Supply

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 constant voltage source. The power supply is easy to assemble on your own within half a day off. Therefore, there is no need to purchase a ready-made block, when it is more interesting to independently make the necessary thing for your laboratory.

Anyone who wants to be able to make a 12-volt block on their own, without much difficulty.
Someone needs a source to power an amplifier, and someone needs to power a small TV or radio ...
Step 1: What parts are needed to assemble the power supply ...
To assemble the unit, prepare in advance the electronic components, parts and accessories from which the unit itself will be assembled ....
-Circuit board.
-Four diodes 1N4001, or similar. The bridge is diode.
-Voltage stabilizer LM7812.
-Low-power step-down transformer for 220 V, the secondary winding should have 14V - 35V AC voltage, with a load current from 100 mA to 1A, depending on what power you want to get at the output.
-Electrolytic capacitor with a capacity of 1000mkF - 4700mkF.
-Capacitor with a capacity of 1uF.
-Two 100nF capacitors.
-Cutting the assembly wire.
-Radiator, if necessary.
If it is necessary to obtain maximum power from the power source, for this it is necessary to prepare an appropriate transformer, diodes and a radiator for the microcircuit.
Step 2: Tools ....
For the manufacture of the block, installation tools are required:
-Soldering iron or soldering station
-Nippers
-Mounting tweezers
- Wire strippers
- A device for suction of solder.
-Screwdriver.
And other tools you might find helpful.
Step 3: Schematic and others ...

To get a 5 volt stabilized power supply, you can replace the LM7812 regulator with the LM7805.
To increase the load capacity of more than 0.5 amperes, you need a radiator for the microcircuit, otherwise it will fail from overheating.
However, if you need to get several hundred milliamperes (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.
Using one 7812 regulator as a voltage regulator and several high-power transistors, this power supply can provide 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 in order to ensure the operation of the microcircuit. It must be borne in mind that one should not strive for a greater difference between the input and output voltage values, since at such a current the heat sink of the output transistors significantly increases in size.
In the transformer circuit, the diodes used must be designed for a large maximum forward current, approximately 100A. Through the 7812 microcircuit, the maximum current flowing in the circuit will not exceed 1A.
Six composite Darlington transistors of the TIP2955 type 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 heatsink size, each transistor passes one sixth of the load current through itself.
A small fan can be used to cool the radiator.
Checking the power supply
When switching on for the first time, it is not recommended to connect the load. We check the performance of the circuit: we connect the voltmeter to the output terminals and measure the voltage value, it should be 12 volts, or the value is very close to it. Next, we connect a load resistor of 100 Ohm, 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 voltage of 12 volts 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 when 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 a short circuit, for this measure the resistance between the collector and the emitter of the transistors with a multimeter. This check must be carried out before installing them in the circuit.

Power supply 3 - 24v

The power supply circuit produces an 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 ohm, 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 op-amp LM1558 or 1458. When using op-amp 1458, it is necessary to replace the stabilizer elements that supply voltage from pin 8 to 3 op-amps from a divider with 5.1 K resistors.
The maximum constant voltage for supplying the op-amp 1458 and 1558 is 36 V and 44 V, respectively. The power transformer must deliver at least 4 volts more than the regulated output voltage. The power transformer in the circuit has an output of 25.2 volts AC with a center tap. When switching the windings, the output voltage is reduced to 15 volts.

1.5V power supply circuit

The power supply circuit for obtaining a voltage of 1.5 volts, a step-down transformer, a bridge rectifier with a smoothing filter and an LM317 microcircuit are used.

Regulated power supply circuit diagram from 1.5V to 12.5V

A power supply circuit with an output voltage adjustment to obtain a voltage from 1.5 volts to 12.5 volts, an 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 case.

Fixed output voltage power supply circuit

A power supply circuit with a fixed output voltage of 5 volts or 12 volts. An LM 7805 microcircuit 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 of the plate. By analogy, you can make a power supply for other output voltages.

20 Watt power supply circuit with protection

The circuit is for a small homemade transceiver, by DL6GL. When developing the unit, the task was to have an efficiency of at least 50%, a nominal supply voltage of 13.8V, a maximum of 15V, for a load current of 2.7a.
Which scheme: switching power supply or linear?
Switching power supplies are small-sized and have good efficiency, but it is not known how they will behave in a critical situation, output voltage surges ...
Despite the shortcomings, a linear control scheme was chosen: a sufficiently large transformer, not high efficiency, cooling is necessary, etc.
Used parts from a homemade power supply from the 1980s: a heatsink with two 2N3055s. The only thing missing was the µA723 / LM723 voltage regulator and a few small parts.
The voltage regulator is assembled on a microcircuit µA723 / LM723 in a standard connection. Output transistors T2, T3 of type 2N3055 for cooling are installed on radiators. Potentiometer R1 sets the output voltage in the range of 12-15V. With the variable resistor R2, the maximum voltage drop across the 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 (it can be any at your discretion).
On the MC3423 microcircuit, a circuit is assembled that is triggered when the voltage (surges) is exceeded at the output of the power supply, by adjusting R3, the voltage triggering threshold on the leg 2 from the divider R3 / R8 / R9 (2.6V reference voltage) is set, the voltage that opens the thyristor BT145 is supplied from the output 8, causing a short circuit causing the 6.3A fuse to blow.

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

Homemade 3.3v power supply

If a powerful 3.3 volt power supply is needed, then it can be made by remaking an old power supply from a pc or using the above diagrams. For example, in the 1.5 V power supply circuit, replace a 47 ohm resistor of a larger value, or put a potentiometer for convenience, adjusting it to the desired voltage.

Transformer power supply for KT808

Many radio amateurs have old Soviet radio components that are lying around idle, but which can be successfully applied and they will serve you faithfully for a long time, one of the well-known UA1ZH circuits, which walks around the Internet. Many spears and arrows were broken on the forums when discussing which field-effect transistor or ordinary silicon or germanium is better, what temperature of the crystal will they withstand and which of them is more reliable?
Each side has its own reasons, 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 gave 50A to the load, while the filter capacitor capacitance was 120,000 microfarads, the voltage of the secondary winding was 19v. It must be borne in mind that the relay contacts must switch such a high current.

Provided correct installation, the output voltage drop does not exceed 0.1 volts

Power supply unit for 1000v, 2000v, 3000v

If we need to have a constant voltage source for high voltage to power the lamp of the output stage of the transmitter, what to use for this? There are many different power supply circuits on the Internet for 600V, 1000V, 2000V, 3000V.
First: for high voltage, circuits with transformers are used for both one phase and three phases (if there is a three-phase voltage source in the house).
Second: to reduce the size and weight, a transformerless power supply circuit is used, directly a 220 volt network with voltage multiplication. The biggest drawback of this circuit is that there is no galvanic isolation between the mains and the load, as the output is connected to this voltage source, observing the 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. diodes when charging capacitors, switching is applied through damping resistors R21 and R22.
The diodes in the high-voltage circuit are shunted by resistors in order to evenly distribute Urev. Calculation of the nominal value according to the formula R (Ohm) = PIVx500. C1-C20 to eliminate white noise and reduce surges. As diodes, you can also use bridges of the KBU-810 type by connecting them according to the indicated scheme and, accordingly, taking the required amount without forgetting about shunting.
R23-R26 for capacitor discharge after mains disconnection. To equalize the voltage on the series-connected capacitors, equalizing resistors are placed in parallel, which are calculated from the ratio for every 1 volt there is 100 ohms, but at high voltage the resistors turn out to be of sufficiently high power and here you have to maneuver, taking into account that the open circuit voltage is 1 more, 41.