Powerful switching power supply for 5v circuit. DIY switching and analog power supply. Video about making a simple pulse power supply device

Simple DIY switching power supply

Hi all! Somehow I wanted to build an amplifier based on the TDA7294. And a friend sold the case for pennies. So black, so beautiful, and it once housed a satellite receiver from the 1995s. And as luck would have it, the TS-180 didn’t fit, it was literally 5 mm short in height. I started looking towards the toroidal transformer. But I saw the price, and somehow I immediately didn’t want it. And then the computer power supply caught my eye, I thought about rewinding it, but again there were a lot of adjustments, current protections, brrrr. I started googling circuits of switching power supplies, a large board, a lot of parts, I was too lazy to do anything at all. But by chance I found a topic on the forum about remaking Tashibra electronic transformers. I read it like this, it seems like nothing complicated.

The next day, a householder went and bought a couple of experimental subjects. One of these costs 40 UAH.

The one on top is BUKO.
Below is a copy of Tashibra, only the name has changed.
They differ slightly from each other. Tashibra, for example, has 5 turns in the secondary winding, and BUKO has 8 turns. The latter has a slightly larger board, with holes for installing additional ones. details.
But the finalization of both blocks is identical!
During modifications you need to be extremely careful, because There is mains voltage present on the transistors.
And if you accidentally short-circuit the output and the transistors make New Year’s fireworks, it’s not my fault, you do everything at your own peril and risk!


Let's look at the diagram:


All blocks from 50 to 150 watts are identical, differing only in the power of the parts.
What is the improvement?
1) It is necessary to add electrolyte after the network diode bridge. The bigger, the better. I set 100 uF at 400 volts.
2) It is necessary to change the current feedback to voltage feedback. For what? And then that the power supply starts only with a load, and without a load it won’t start.
3) Rewind the transformer (if necessary).
4) Install a diode bridge at the output (for example, KD213, imported Schottks are welcome) and a capacitor.


Current feedback coil in the blue circle. It is necessary to unsolder one end of it and close it on the board. Did you make a short circuit on the board? So let's move on!
Then we take a piece of twisted pair wire to the power transformer and wind it 2 turns and to the communication transformer we wind it 3 turns. We solder the ends to a 2.4-2.7 ohm 5-10W resistor. We connect a light bulb to the output and ALWAYS a 150-watt light bulb into the break in the network wire. We turn it on - the light bulb does not light up, remove it, turn it on again and see that the light bulb at the output lights up. And if it doesn’t light up, then you need to run the wire into the communication transformer from the other side. The light came on, now turn it off. BUT before you do anything, be sure to discharge the mains capacitor with a 470 ohm resistor!!
I assembled a power supply for stereo ULF on a TDA7294. Accordingly, I need to rewind it to a voltage of 2X30 volts.
The transformer has 5 turns. 12V/5vit.=2.8 vit/volt.
30V/2.8V=11 turns. That is, we need to wind 2 coils of 11 turns each.
We unsolder the transformer from the board, remove 2 turns from the trance, and wind up the secondary winding accordingly. Then I wound the coils with regular stranded wire. Immediately one coil, then the second. And we connect the beginnings of the windings or ends and get the middle tap.
That is, in this way we can wind the coil to the required voltage!
The frequency of the power supply with voltage feedback is 30 kHz.
Then I assembled a diode bridge from KD213, installed electrolytes and definitely need ceramics!!!
How to connect the coils, and what possible variations can be seen in the diagram from the adjacent article.

Remember- when the output of the power supply is closed, it lights up! I burned it myself once. The diodes, transistors and resistors in the base have burned out! I replaced them and the power supply started working safely! Well, now a couple of photos of the finished power supply for ULF.

Radio amateurs prefer to make many electronics with their own hands. This provides many advantages, both in terms of saving money and guaranteeing the quality of the assembled product.
Very often, radio amateurs prefer to make a power supply unit (PSU), since such a device is the basis of a home laboratory.

In today's article we will talk about such a power supply as a switching power supply of an regulated type. Many craftsmen make it with their own hands.

Device information

In life, situations very often arise when you need a device such as a power supply. This product can power many electrical appliances. Of course, in such a situation, you can use various analogues, for example, car batteries. But they have a big drawback, which is the supply of a constant voltage of 12 V. And this is not enough to power standard household equipment.
An excellent solution in such situations would be to use a pulse current converter (regulated power supply). The peculiarity of such a device is the ability to convert the existing voltage, for example 12 V, into the one we need - 220 V.
This became possible thanks to a special operating principle. It consists of converting the alternating voltage available in the network with a frequency of 50 Hz into a similar rectangular type. After this, the voltage is transformed to achieve the required value, rectified and filtered. The operating diagram of such a device is as follows.

The power supply has increased power (thanks to the transistor) and can simultaneously act as a switch and a pulse transformer, converting the current voltage.
Note! The efficiency of the power supply (regulated type) is increased by the frequency rise input. Its increase makes it possible to significantly reduce the weight and size of the steel core used inside the product.
Switching type power supply can be of two types:

  • controlled from outside. This power supply is used in most electrical appliances;
  • pulse-type self-generators.

Factory model

The assembly diagram for each type of power supply will be different.
At the same time, produced serial models may have different power ratings and dimensions. It all depends on the specifics of their use.

Factory devices of this type operate in the frequency range from 18 to 50 kHz. But such a model can be made with your own hands if desired. Some electronics hobbyists can even repurpose an old power supply to meet new needs. For beginners, there is a simple scheme that will allow even a completely inexperienced person to cope with it. Such a modification will be in no way inferior in quality and technical parameters to the purchased model.

Where are they used?

The scope of use of an regulated type of switching power supply is expanding every year. This is due to the advent of ever new equipment and new areas of human activity.
Switching power supplies are used in the following areas:

  • providing energy for all types of electrical appliances (computer equipment and household appliances);
  • uninterruptible power supply to chargers applied to batteries;
  • providing power to low-voltage lighting systems. These types of lighting include the use of LED strips.

Ceiling lighting

In all these situations, a self-assembled device will function no worse than factory models. At the same time, you can make it more versatile. A simple type of DIY power supply will become an indispensable part of your home laboratory.

Advantages and disadvantages

Transformer

The switching regulated power supply has the following advantages:

  • light weight. This is due to the fact that it requires a smaller transformer;
  • more convenient design of the converter;
  • the presence of a filter for the output voltage, which also has small dimensions;
  • the highest efficiency rate, which can reach up to 90-98%. Thanks to this, this type of device has minimal energy loss;
  • the degree of reliability of stabilizers is an order of magnitude greater;
  • extended frequency range. This parameter also applies to voltage. Typically, such capabilities are found in expensive linear units;
  • mass production of components, and hence the affordable cost of assembling the unit.

In addition, this type of device may have several degrees of protection against:

  • power outages;
  • voltage drops;
  • lack of output load;
  • short circuit.

But in addition to the advantages, this product also has disadvantages:

  • Repairing such a device is somewhat complicated. This is due to the fact that the power supply elements operate without galvanic isolation;
  • high frequency interference may occur;
  • increased sensitivity to interference.

There is also a limitation on the minimum power at which the power supply will start working. The circuitry used to assemble the product yourself can consume a significant amount of power.

Complex circuit

Also, the assembly circuit may require bipolar power supply. To power larger electrical systems, a separate power supply with the required number of poles and power should be used. At the same time, specific indicators must also be determined for voltage. Therefore, to assemble it yourself, if you are an amateur, you need a circuit diagram of a simple unipolar low-power device.

Assembly

Many radio amateurs use other models of old converters to create a regulated switching power supply. For example, a computer power supply is perfect for these purposes. Here you will need only a third of his circuit.
The assembly looks like the following algorithm:

  • we remove the circuit from the old converter;
  • the part that goes to the transformer should be cut out of it;

Approximate view of the diagram

  • Next, transistors should be removed from the block to amplify the signal coming from the high-frequency generator;
  • in order to make a generator, you can use the simplest circuits;
  • for a transformer, if it cannot be disassembled, you can use a core with an internal cross-section of the rod of 25-30 mm2. For the primary winding we use 40 turns, and for the secondary winding - 2x8 turns;

Note! To avoid the penetration of extraneous high-frequency noise, the transformer should be filled with varnish.

  • We also take the isolation transformer from the computer unit. It can be wound on any small-sized core. We use a thin wire for this;
  • For cooling we install a fan. It will turn on when the current reaches 1.5 A. At lower values, natural cooling will be sufficient. To turn on the fan, install resistor R20.

All parts must be installed on the printed circuit board.

After this, you need to unsolder all the parts and install them in the case. Now all that remains is to install the voltmeter and ammeter. As a result, you will get a simple switching power supply with the ability to regulate voltage.

Ready power supply

As a result, the device voltage will be from 2V to the voltage on the secondary winding.
You can make a switching power supply of an regulated type using different circuits. In this case, you need to accurately follow the chosen diagram and correctly solder all the components onto the board. Using high-quality parts, you will make the necessary power supply with your own hands and will be able to use it in a wide variety of areas, connecting household and computing devices to it.


Homemade adjustable transistor power supplies: assembly, practical application

!
In this article, together with Roman (author of the YouTube channel “Open Frime TV”), we will assemble a universal power supply on the IR2153 chip. This is a kind of “Frankenstein” that contains the best qualities from different schemes.

The Internet is full of power supply circuits based on the IR2153 chip. Each of them has some positive features, but the author has not yet encountered a universal scheme. Therefore, it was decided to create such a diagram and show it to you. I think we can go straight to it. So, let's figure it out.


The first thing that catches your eye is the use of two high voltage capacitors instead of one 400V capacitor. This way we kill two birds with one stone. These capacitors can be obtained from old computer power supplies without spending money on them. The author specially made several holes in the board for different sizes of capacitors.








If the unit is not available, then the prices for a pair of such capacitors are lower than for one high-voltage one. The capacitance of the capacitors is the same and should be at the rate of 1 µF per 1 W of output power. This means that for 300W of output power you will need a pair of capacitors of 330uF each.




Also, if we use this topology, there is no need for a second decoupling capacitor, which saves us space. And that is not all. The voltage of the decoupling capacitor should no longer be 600 V, but only 250 V. Now you can see the sizes of capacitors for 250V and 600V.




The next feature of the circuit is power supply for IR2153. Everyone who built blocks on it encountered unrealistic heating of the supply resistors.




Even if you put them on during recess, a lot of heat is released. An ingenious solution was immediately applied, using a capacitor instead of a resistor, and this gives us the fact that there is no heating of the element due to the power supply.


The author of this homemade product saw this solution from Yuri, the author of the YouTube channel "Red Shade". The board is also equipped with protection, but the original version of the circuit did not have it.






But after tests on the breadboard, it turned out that there was too little space to install the transformer and therefore the circuit had to be increased by 1 cm, this gave extra space for which the author installed protection. If it is not needed, then you can simply install jumpers instead of the shunt and not install the components marked in red.




The protection current is regulated using this trimming resistor:


Shunt resistor values ​​vary depending on the maximum output power. The more power, the less resistance needed. For example, for power below 150 W, 0.3 Ohm resistors are needed. If the power is 300 W, then 0.2 Ohm resistors are needed, and at 500 W and above we install resistors with a resistance of 0.1 Ohm.


This unit should not be assembled with a power higher than 600 W, and you also need to say a few words about the operation of the protection. She's hiccupping here. The starting frequency is 50 Hz, this happens because the power is taken from an alternator, therefore, the latch is reset at the mains frequency.




If you need a snap-on option, then in this case the power supply for the IR2153 microcircuit must be taken constant, or rather from high-voltage capacitors. The output voltage of this circuit will be taken from a full-wave rectifier.


The main diode will be a Schottky diode in a TO-247 package; you select the current for your transformer.


If you don’t want to take a large case, then in the Layout program it’s easy to change it to TO-220. There is a 1000 µF capacitor at the output, it is sufficient for any currents, since at high frequencies the capacitance can be set to less than for a 50 Hz rectifier.




It is also necessary to note such auxiliary elements as snubbers in the transformer harness;


smoothing capacitors;


as well as a Y-capacitor between the high and low side grounds, which dampens noise on the output winding of the power supply.


There is an excellent video about these capacitors on YouTube (the author attached the link in the description under his video (SOURCE link at the end of the article)).


You cannot skip the frequency-setting part of the circuit.


This is a 1 nF capacitor, the author does not recommend changing its value, but he installed a tuning resistor for the driving part, there were reasons for this. The first of them is the exact selection of the desired resistor, and the second is a slight adjustment of the output voltage using frequency. Now a small example, let's say you are making a transformer and see that at a frequency of 50 kHz the output voltage is 26V, but you need 24V. By changing the frequency, you can find a value at which the output will have the required 24V. When installing this resistor, we use a multimeter. We clamp the contacts into crocodiles and rotate the resistor handle to achieve the desired resistance.




Now you can see 2 prototype boards on which tests were carried out. They are very similar, but the protection board is slightly larger.


The author made the breadboards in order to order the production of this board in China with peace of mind. In the description under the author's original video, you will find an archive with this board, circuit and signet. There will be two scarves, both the first and second options, so you can download and repeat this project.

After ordering, the author was impatiently waiting for the payment, and now they have already arrived. We open the parcel, the boards are packed quite well - you can’t complain. We visually inspect them, everything seems to be fine, and immediately proceed to soldering the board.








And now she is ready. It all looks like this. Now let’s quickly go through the main elements not previously mentioned. First of all, these are fuses. There are 2 of them, on the high and low sides. The author used these round ones because their sizes are very modest.




Next we see the filter capacitors.


They can be obtained from an old computer power supply. The author wound the choke on a T-9052 ring, 10 turns with 0.8 mm wire, 2 cores, but you can use a choke from the same computer power supply.
Diode bridge - any, with a current of at least 10 A.


There are also 2 resistors on the board for discharging the capacitance, one on the high side, the other on the low side.


Switching power supplies are often used by radio amateurs in homemade designs. With relatively small dimensions, they can provide high output power. With the use of a pulse circuit, it became possible to obtain output power from several hundred to several thousand watts. Moreover, the dimensions of the pulse transformer itself are no larger than a matchbox.

Switching power supplies - operating principle and features

The main feature of pulsed power supplies is their increased operating frequency, which is hundreds of times higher than the network frequency of 50 Hz. At high frequencies with a minimum number of turns in the windings, high voltage can be obtained. For example, to obtain 12 Volts of output voltage at a current of 1 Ampere (in the case of a mains transformer), you need to wind 5 turns of wire with a cross-section of approximately 0.6–0.7 mm.

If we talk about a pulse transformer, the master circuit of which operates at a frequency of 65 kHz, then to obtain 12 Volts with a current of 1A, it is enough to wind only 3 turns with a wire of 0.25–0.3 mm. That is why many electronics manufacturers use a switching power supply.

However, despite the fact that such units are much cheaper, more compact, have high power and low weight, they have electronic filling, and therefore are less reliable when compared with a network transformer. It is very simple to prove their unreliability - take any switching power supply without protection and short-circuit the output terminals. At best, the unit will fail, at worst, it will explode and no fuse will save the unit.

Practice shows that the fuse in a switching power supply burns out last, first of all the power switches and the master oscillator fly out, then all parts of the circuit one by one.

Switching power supplies have a number of protections both at the input and output, but they do not always save. In order to limit the current surge when starting the circuit, almost all SMPS with a power of more than 50 Watts use a thermistor, which is located at the input of the circuits.

Let's now look at the TOP 3 best switching power supply circuits that you can assemble with your own hands.

Simple DIY switching power supply

Let's look at how to make the simplest miniature switching power supply. Any novice radio amateur can create a device according to the presented scheme. It is not only compact, but also operates over a wide range of supply voltages.

A homemade switching power supply has a relatively low power, within 2 Watts, but it is literally indestructible and is not afraid of even long-term short circuits.


Circuit diagram of a simple switching power supply


The power supply is a low-power switching power supply of the self-oscillator type, assembled with just one transistor. The autogenerator is powered from the network through a current-limiting resistor R1 and a half-wave rectifier in the form of a diode VD1.


Transformer of a simple switching power supply


A pulse transformer has three windings, a collector or primary winding, a base winding and a secondary winding.


An important point is the winding of the transformer - both the printed circuit board and the diagram indicate the beginning of the windings, so there should be no problems. We borrowed the number of turns of the windings from a transformer for charging cell phones, since the circuit diagram is almost the same, the number of windings is the same.

First we wind the primary winding, which consists of 200 turns, the wire cross-section is from 0.08 to 0.1 mm. Then we put insulation and use the same wire to wind the base winding, which contains from 5 to 10 turns.

We wind the output winding on top, the number of turns depends on what voltage is needed. On average, it turns out to be about 1 Volt per turn.

Video about testing this power supply:

Do-it-yourself stabilized switching power supply on SG3525

Let's take a step-by-step look at how to make a stabilized power supply using the SG3525 chip. Let's immediately talk about the advantages of this scheme. The first and most important thing is stabilization of the output voltage. There is also a soft start, short circuit protection and self-recording.



First, let's look at the device diagram.


Beginners will immediately pay attention to 2 transformers. In the circuit, one of them is power, and the second is for galvanic isolation.

Don't think that this will make the scheme more complicated. On the contrary, everything becomes simpler, safer and cheaper. For example, if you install a driver at the output of a microcircuit, then it needs a harness.



Let's look further. This circuit implements microstart and self-powering.


This is a very productive solution, it eliminates the need for a standby power supply. Indeed, making a power supply for a power supply is not a very good idea, but this solution is simply ideal.


Everything works as follows: the capacitor is charged from a constant voltage and when its voltage exceeds a given level, this block opens and discharges the capacitor to the circuit.





Its energy is quite enough to start the microcircuit, and as soon as it starts, the voltage from the secondary winding begins to power the microcircuit itself. You also need to add this output resistor to the microstart; it serves as a load.


Without this resistor the unit will not start. This resistor is different for each voltage and must be calculated based on considerations such that at the rated output voltage, 1 W of power is dissipated on it.

We calculate the resistance of the resistor:

R = U squared/P
R = 24 squared/1
R = 576/1 = 560 Ohm.


There is also a soft start on the diagram. It is implemented using this capacitor.


And current protection, which in the event of a short circuit will begin to reduce the PWM width.


The frequency of this power supply is changed using this resistor and connector.



Now let's talk about the most important thing - stabilizing the output voltage. These elements are responsible for it:


As you can see, 2 zener diodes are installed here. With their help you can get any output voltage.

Calculation of voltage stabilization:

U out = 2 + U stab1 + U stab2
U out = 2 + 11 + 11 = 24V
Possible error +- 0.5 V.


For stabilization to work correctly, you need a voltage reserve in the transformer, otherwise, when the input voltage decreases, the microcircuit simply will not be able to produce the required voltage. Therefore, when calculating a transformer, you should click on this button and the program will automatically add voltage to you on the secondary winding for reserve.



Now we can move on to looking at the printed circuit board. As you can see, everything here is quite compact. We also see a place for the transformer, it is toroidal. Without any problems, it can be replaced with an W-shaped one.


The optocoupler and zener diodes are located near the microcircuit, and not at the output.


Well, there was nowhere to put them on the way out. If you don't like it, make your own PCB layout.

You may ask, why not increase the fee and make everything normal? The answer is as follows: this was done so that it would be cheaper to order the board in production, since boards larger than 100 square meters. mm are much more expensive.

Well, now it’s time to assemble the circuit. Everything is standard here. We solder without any problems. We wind the transformer and install it.

Check the output voltage. If it is present, then you can already connect it to the network.


First, let's check the output voltage. As you can see, the unit is designed for a voltage of 24V, but it turned out a little less due to the spread of the zener diodes.


This error is not critical.

Now let's check the most important thing - stabilization. To do this, take a 24V lamp with a power of 100W and connect it to the load.



As you can see, the voltage did not sag and the block withstood without problems. You can load it even more.

Video about this switching power supply:


We reviewed the TOP 3 best switching power supply circuits. Based on them, you can assemble a simple power supply, devices on TL494 and SG3525. Step-by-step photos and videos will help you understand all installation issues.

But not one, but four at once. This material will present you with several circuits of switching power supplies made on the popular and reliable IR2153 microcircuit. All these projects were developed by famous user Nem0. Therefore, I will write here on his behalf. All the schematic solutions shown here were personally assembled and tested by the author a couple of years ago.

In general, let's start with the so-called “high-voltage” power supply:

The circuit is traditional, which Nem0 uses in most of its impulse designs. The driver receives power directly from the mains through a resistor. This, in turn, helps to reduce the power dissipated at this resistance, compared to supplying voltage from a 310v circuit. Switching power supply circuit has a smooth voltage switching function, which significantly limits the starting current. The soft start module is powered through capacitor C2, which reduces the mains voltage of 230v.

The power supply provides effective protection to prevent short circuits and peak loads in the secondary power path. The role of a current sensor is performed by a constant resistor R11, and the protection response current is adjusted using the trimmer R10. When the current is cut off by the protection, the LED lights up, indicating that the protection has tripped. The output bipolar rectified voltage is +/-70v.

The transformer is made with one primary winding, consisting of fifty turns, and 4 secondary windings, each containing twenty-three turns. The diameter of the copper core and the magnetic circuit of the transformer are calculated depending on the specified power of a specific power supply.

Now consider the following power supply:

This version of the power supply is very similar to the circuit described above, although there are significant differences. The fact is that here the supply voltage to the driver comes from a special winding of the transformer, through a ballast resistor. All other components in the design are almost the same.

The output power of this power supply is determined both by the characteristics of the transformer and the parameters of the IR2153 microcircuit, but also by the life of the diodes in the rectifier. This circuit used KD213A diodes, which have a maximum reverse voltage of 200v and a maximum forward current of 10A. To ensure correct operation of diodes at high currents, they must be installed on a radiator.

The T2 throttle deserves special attention. It is wound on a joint ring magnetic core; if necessary, another core can be used. Winding is done with enamel wire with a cross-section calculated according to the current in the load. Also, the power of the pulse transformer is determined depending on what output power you want to receive. It is very convenient to make calculations of transformers using special computer calculators.

Now the third circuit of a switching power supply based on powerful field-effect transistors IRFP460:

This version of the circuit already has a specific difference compared to previous models. The main differences are that the short circuit and overload protection system is assembled here using a current transformer. And there is one more difference, this is the presence in the circuit of a pair of BD140 pre-output transistors. It is these transistors that make it possible to cut off a large input capacitance of powerful field switches relative to the driver output.

There is also a small difference, this is a voltage-quenching resistor related to the soft-start module; it is installed in the 230v circuit. In the previous diagram it is located in the +310v power path. In addition, the circuit has an overvoltage limiter that serves to dampen the residual pulse of the transformer. In all other respects, this one no longer has any differences between the above schemes.