DIY spot welding timer circuit. Homemade spot welding. Making your own resistance welding from a microwave

Nowadays, it is rare that anyone introduces a mains transformer into a home-made amplifier design, and rightly so - a switching power supply is cheaper, lighter and more compact, and a well-assembled one produces almost no interference into the load (or interference is minimized).

Of course, I don’t argue that a network transformer is much, much more reliable, although modern impulse generators, stuffed with all kinds of protections, also do a good job of their task.

IR2153 is, I would say, a legendary microcircuit that is used very often by radio amateurs and is being implemented specifically in network switching power supplies. The microcircuit is a simple half-bridge driver and in power supply circuits it works as a pulse generator.

Based on this microcircuit, power supplies from several tens to several hundred watts and even up to 1500 watts are built; of course, as the power increases, the circuit will become more complicated.

However, I don’t see the point in doing IIP high power with the use of this particular microcircuit, the reason is that it is impossible to organize output stabilization or control, and not only the microcircuit is not a PWM controller, therefore there can be no talk of any PWM control, and this is very bad. Good IPs do what they do right push-pull microcircuits PWM, for example TL494 or its relatives, etc., and the block on IR2153 is more of a beginner-level block.

Let's move on to the design itself pulse source nutrition. Everything is assembled according to the datasheet - a typical half-bridge, two half-bridge capacitors, which are constantly in a charge/discharge cycle. The power of the circuit as a whole will depend on the capacity of these capacitors (well, of course, not only on them). The calculated power of this particular option is 300 watts, I don’t need more, the unit itself is for powering two UHF channels. The capacity of each capacitor is 330 μF, the voltage is 200 Volts, any computer power supply contains just such capacitors, in theory, the circuit diagram of computer power supplies and our unit is somewhat similar, in both cases the topology is half-bridge.

At the input of the power supply, everything is also as it should be - a varistor for surge protection, a fuse, a surge protector and, of course, a rectifier. A full-fledged diode bridge, which you can take ready-made, the main thing is that the bridge or diodes have reverse voltage at least 400 Volts, ideally 1000, and with a current of at least 3 Amperes. Separating capacitor - film, 250 V or better 400, capacity 1 μF, by the way - can also be found in a computer power supply.

Transformer Calculated according to the program, the core is from a computer power supply unit, alas, I cannot indicate the overall dimensions. In my case, the primary winding is 37 turns with a 0.8mm wire, the secondary winding is 2 x 11 turns with a bus of 4 0.8mm wires. With this situation, the output voltage is around 30-35 Volts, of course, the winding data will be different for everyone, depending on the type and overall dimensions core.

Many people know how much I like to deal with different power supplies. This time I have a somewhat unusual power supply on my desk, at least I haven’t tested one yet. And by and large, I’ve never seen reviews of power supplies of this type before, although the thing is interesting in its own way and I’ve made similar power supplies myself before.
I decided to order it out of pure curiosity, I decided that it might be useful. However, more details in the review.

In general, it’s probably worth starting with a short lyrical introduction. Many years ago, I was quite keen on audio technology, and went through both completely homemade versions and “hybrids”, which used PAs with a power of up to 100 Watts from the store Young technician, and half-disassembled Radiotekhnika UKU 010, 101 and Odyssey 010, then there was Phoenix 200U 010S.
I even tried to assemble Sukhov’s UMZCH, but something didn’t work out then, I don’t even remember what exactly.

The acoustics were also different, both homemade and ready-made, for example Romantika 50ac-105, Cleaver 150ac-009.

But most of all I remember Amfiton 25AC 027, although they were slightly modified. Along with minor changes in the circuit and design, I replaced the original 50 GDN speakers with 75 GDN ones.
This and the previous photos are not mine, since my equipment was sold a long time ago, and then I switched to Sven IHOO 5.1, and then generally began to listen only to small computer speakers. Yes, this is such a regression.

But then thoughts began to wander in my head, to do something, for example, a power amplifier, perhaps just like that, perhaps to do everything differently. But in the end I decided to order a power supply. Of course I can do it myself, moreover, in one of the reviews I not only did it, but also posted detailed instructions, but I’ll come back to this later, but for now I’ll move on to the review.

I'll start with a list of declared technical characteristics:
Supply voltage - 200-240 Volts
Output power - 500 Watt
Output voltages:
Basic - ±35 Volts
Auxiliary 1 - ± 15 Volt 1 Ampere
Auxiliary 2 - 12 Volt 0.5 Ampere, galvanically isolated from the rest.
Dimensions - 133 x 100 x 42 mm

The channels ± 15 and 12 Volts are stabilized, the main voltage ± 35 Volts is not stabilized. Here I will probably express my opinion.
I am often asked which power supply to buy for one or another amplifier. To which I usually answer - it’s easier to assemble it yourself based on the well-known IR2153 drivers and their analogues. The first question that follows after this is that they don’t have voltage stabilization.
Yes, in my personal opinion - voltage stabilization UMZCH power supply not only unnecessary, but sometimes even harmful. The fact is that a stabilized power supply usually makes more noise at HF ​​and, in addition, there may be problems with the stabilization circuits, because the power amplifier does not consume energy evenly, but in bursts. We listen to music, not just one frequency.
A power supply without stabilization usually has a slightly higher efficiency, since the transformer always operates in optimal mode, has no feedback and is therefore more similar to a regular transformer, but with lower active resistance of the windings.

Here we actually have an example of a power supply for power amplifiers.

The packaging is soft, but wrapped in such a way that it is unlikely to be damaged during delivery, although the confrontation between the post office and sellers will probably be eternal.

Externally it looks beautiful, you can’t really complain.

The size is relatively compact, especially when compared with a conventional transformer of the same power.

More clear sizes are available on the product page in the store.

1. There is a connector installed at the input of the power supply, which turned out to be quite convenient.
2. There is a fuse and a full-fledged input filter. But they forgot about the thermistor, which protects both the network and the diode bridge with capacitors from current surges, this is bad. Also in the area of ​​the input filter there are contact pads that must be closed to transfer the power supply to a voltage of 110-115 Volts. Before turning on for the first time, it is better to check whether the sites are closed if your network is 220-230.
3. Diode bridge KBU810, everything would be fine, but it does not have a radiator, and at 500 watts it is already desirable.
4. The input filter capacitors have a declared capacitance of 470 µF, but the actual capacitance is about 460 µF. Since they are connected in series, the total input filter capacitance is 230 µF, not enough for an output power of 500 watts. By the way, the board requires the installation of one capacitor. But in any case, I would not recommend raising the container without installing a thermistor. Moreover, to the right of the fuse there is even a place for a thermistor, you just need to solder it and cut the track under it.

The inverter uses IRF740 transistors, although they are far from new transistors, but I have also used them widely in similar applications before. Alternatively, IRF830.
The transistors are installed on separate radiators; this was done partly for a reason. The radiators are connected to the transistor body, not only at the mounting location of the transistor itself, but also the mounting pins of the radiator are connected on the board itself. In my opinion, this is a bad decision, since there will be excess radiation into the air at the conversion frequency; at least I would disconnect the lower transistor of the inverter (in the photo it is farther away) from the radiator, and the radiator from the circuit.

An unknown module controls the transistors, but judging by the presence of a power resistor, and just my experience, I think that I won’t be much mistaken if I say that there is a banal IR2153 inside. However, why to make such a module remains a mystery to me.

The inverter is assembled using a half-bridge circuit, but the middle point is not the connection point of filtering electrolytic capacitors, but two film capacitors with a capacity of 1 μF (in the photo, two parallel to the transformer), and the primary winding is connected through a third capacitor, also with a capacity of 1 μF (in the photo, perpendicular to the transformer) .
The solution is well-known and convenient in its own way, since it makes it very easy not only to increase the capacity of the input filter capacitor, but also to use one at 400 Volts, which can be useful when upgrading.

The size of the transformer is very modest for the declared power of 500 watts. Of course, I will also test it under load, but I can already say that in my opinion its real long-term power is more than 300-350 watts.

On the store page, in the list key features, it was indicated -

3. Transformers 0.1 mm * 100 multi-strand oxygen-free enameled wire, heat is very low, efficiency is more than 90%.

Which in translation means - the transformer uses a winding of 100 pieces of oxygen-free wires with a diameter of 0.1 mm, heating is reduced and the efficiency is above 90%.
Well, I’ll check the efficiency later, but it’s a fact about the fact that the winding is multi-wire. Of course, I didn’t count them, but the harness is pretty good and this winding option really has a positive effect on the quality of operation of the transformer in particular and the entire power supply unit in general.

They didn’t forget about the capacitor connecting the “hot” and “cold” sides of the power supply, and installed it of the correct (Y1) type.

The output rectifier of the main channels uses diode assemblies MUR1620CTR and MUR1620CT (16 Amperes 200 Volts), and the manufacturer did not collectively farm “hybrid” options, but supplied, as expected, two complementary assemblies, one with a common cathode, and the other with a common anode. Both assemblies are mounted on separate heatsinks and, just like in the case of transistors, they are not isolated from the components. But in this case, the problem can only be in terms of electrical safety, although if the case is closed, then there is nothing wrong with that.
The output filter uses a pair of 1000 µF x 50 Volt capacitors, which in my opinion is not enough.

In addition, to reduce ripple, a choke is installed between the capacitors, and the capacitors after it are additionally shunted with 100 nF ceramic.
In general, on the product page it was written -

1. All high-frequency low-impedance electrolytic capacitors specifications, low ripple.

In translation, all capacitors have low impedance to reduce ripple. In general, this is how it is, Cheng-X is used, but this is essentially just a slightly improved version of ordinary Chinese capacitors and I would rather use my favorite Samwha RD or Capxon KF.

There are no discharge resistors parallel to the capacitors, although there is space on the board for them, so “surprises” may await you, since the charge lasts quite a long time.

Additional power channels are connected to their own windings of the transformer, and the 12 Volt channel is galvanically isolated from the rest.
Each channel has independent voltage stabilization, chokes to reduce interference, and ceramic output capacitors. But you probably noticed that there are five diodes in the rectifier. The 12 Volt channel is powered by a half-wave rectifier.

At the output, as well as at the input, there are terminal blocks, and they are of very good quality and design.

On the product page there is a photo at the top where you can see everything at once. It was only later that I noticed that in all the photos in the store there were mounting stands; mine did not have them :(

The printed circuit board is double-sided, the quality is very high, fiberglass is used, and not the usual getinax. A protective slot is made in one of the bottlenecks.
A pair of resistors were also found at the bottom, I assume that this is a primitive overload protection circuit, which is sometimes added to drivers on IR2153. But to be honest, I wouldn't count on it.

Also at the bottom of the printed circuit board there are output markings and output voltage options for which these boards are manufactured. Two things intrigued me a little - two identical ± 70 Volt options and a custom option.

Before moving on to the tests, I’ll tell you a little about my version of such a power supply.
About three and a half years ago I posted an regulated power supply unit, which used a power supply assembled in approximately the same way.

When assembled it also looked pretty similar, sorry for the poor quality of the photo.

If we remove from my version everything “unnecessary”, for example, a unit for adjusting fan speed depending on temperature, as well as a more powerful transistor driver and an additional power supply circuit from the inverter output, then we will get the circuit of the reviewed power supply.
In essence, this is the same power supply, only there are more output voltages. In general, the circuit design of this power supply is quite simple, only a banal self-oscillator is simpler.

In addition, the reviewed power supply is equipped with a primitive output power limiting circuit; I suspect that it is implemented as shown in the selected section of the circuit.

But let’s see what this circuit and its implementation in the reviewed power supply are capable of.
It should be noted here that since there is no stabilization of the main voltage, it directly depends on the voltage in the network.
With an input voltage of 223 Volts, the output is 35.2 in idle mode. The consumption is 3.3 watts.

In this case, there is noticeable heating of the transistor driver power resistor. Its nominal value is 150 kOhm, which at 300 Volts gives a power dissipation of about 0.6 Watts. This resistor heats up regardless of the load on the power supply.
A slight heating of the transformer is also noticeable; the photo was taken approximately 15 minutes after switching on.

For the load test, a structure was assembled consisting of two electronic loads, an oscilloscope and a multimeter.
The multimeter measured one power channel, the second channel was controlled by a voltmeter of the electronic load, which was connected with short wires.

I won’t bore the reader with a large list of tests, so I’ll go straight to the oscillograms.
1, 2. Different output points of the power supply to the diode assemblies, and from at different times scans. The inverter operating frequency is 70 kHz.
3, 4. Ripple before and after the 12 Volt channel choke. After Krenka, everything is generally smooth, but there is a problem, the voltage at this point is only about 14.5 Volts without load on the main channels and 13.6-13.8 with load, which is not enough for a 12 Volt stabilizer.

The load tests went like this:
First, I loaded one channel by 50%, then the second by 50%, then the load of the first was raised to 100%, and then the second. The result was four load modes - 25-50-75-100%.
First, the RF output, in my opinion, is very good, the ripple is minimal, and when installing an additional choke, it can be reduced to almost zero.

But at a frequency of 100 Hz everything is quite sad, the input capacitance is too small, too small.
The total ripple swing at 500 watts of output power is about 4 volts.

Load tests. Since the voltage sagged under load, I gradually increased the load current so that the output power roughly corresponded to the range 125-250-375-500 Watts.
1. First channel - 0 Watt, 42.4 Volts, second channel - 126 Watts, 33.75 Volts
2. The first channel - 125.6 Watts, 32.21 Volts, the second channel - 130 Watts, 32.32 Volts.
3. The first channel - 247.8 Watts, 29.86 Volts, the second channel - 127 Watts, 30.64 Volts.
4. The first channel is 236 Watts, 29.44 Volts, the second channel is 240 Watts, 29.58 Volts.

You probably noticed that in the first test the voltage of the unloaded channel is more than 40 Volts. This is due to voltage surges, and since there is no load at all, the voltage gradually rose, even a small load returned the voltage to normal.

At the same time, consumption was measured, but since there is a relatively large error in measuring output power, I will also give the calculated efficiency values ​​approximately.
1. 25% load, efficiency 89.3%
2. 50% load, efficiency 91.6%
3. 75% load, 90% efficiency
4. 476 Watt, about 95% load, efficiency 88%
5, 6. Just out of curiosity, I measured the power factor at 50 and 100% power.

In general, the results are approximately similar to the stated 90%

Tests showed pretty good performance of the power supply and everything would have been great if not for the usual “fly in the ointment” in the form of heating. At the very beginning, I estimated the power of the power supply at approximately 300-350 Watts.
During the usual test with gradual warming up and intervals of 20 minutes, I found out that at a power of 250 watts the power supply behaves just fine, heating the components approximately as follows:
Diode bridge - 71
Transistors - 66
Transformer (magnetic core) - 72
Output diodes - 75

But when I raised the power to 75% (375 Watt), then after 10 minutes the picture was completely different
Diode bridge - 87
Transistors - 100
Transformer (magnetic core) - 78
Output diodes - 102 (more loaded channel)

After trying to figure out the problem, I found out that goes strong overheating of the transformer windings, as a result of this the magnetic circuit warms up, its saturation induction decreases and it begins to enter saturation, as a result, the heating of the transistors sharply increases (later I recorded the temperature up to 108 degrees), then I stopped the test. At the same time, “cold” tests with a power of 500 watts passed normally.

Below are a couple of thermal photos, the first at 25% load power, the second at 75%, respectively, after half an hour (20+10 minutes). The temperature of the windings reached 146 degrees and there was a noticeable smell of overheated varnish.

In general, I will now summarize some results, some of which are disappointing.
The overall workmanship is very good, but there are some design nuances, such as installing transistors without insulation from the heatsinks. Pleased with the large number of output voltages, for example 35 Volts to power the power amplifier, 15 for preamp and independent 12 Volts for all service devices.

There are circuit defects, for example, the absence of a thermistor at the input and the low capacitance of the input capacitors.
In the specifications it was stated that additional 15 Volt channels can produce a current of up to 1 Ampere, in reality I would not expect more than 0.5 Ampere without additional cooling of the stabilizers. The 12 Volt channel most likely will not produce more than 200-300 mA at all.

But all these problems are either not critical or can be easily solved. The most difficult problem is heating. The power supply can supply up to 250-300 Watts for a long time, 500 Watts only for a relatively short time, or you will have to add active cooling.

Along the way, I had a small question for the respected public. There are thoughts about making your own amplifier, according to the reviews. But which one would be more interesting, a power amplifier, a preliminary amplifier, if a PA, then at what power, etc. Personally, I don’t really need it, but I’m in the mood to dig deeper. The reviewed power supply has little to do with this :)

That's all for me, I hope that the information was useful and, as usual, I look forward to questions in the comments.

The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.

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Other articles devoted to the construction of this ULF.

Schematic diagram of the power supply.

The power supply is assembled according to one of standard circuits. Bipolar power supply is selected to power the final amplifiers. This allows the use of inexpensive, high-quality integrated amplifiers and eliminates a number of problems associated with supply voltage ripple and turn-on transients. https://site/

The power supply must provide power to three microcircuits and one LED. Two TDA2030 microcircuits are used as final power amplifiers, and one TDA1524A microcircuit is used as a volume control, network base and tone.

Electrical diagram of the power supply.

VD3... VD6 – KD226

C1 – 680mkFx25V C3... C6 – 1000mkFx25V

A bipolar, full-wave rectifier with a midpoint is assembled using diodes VD3...VD6. This connection circuit reduces the voltage drop across the rectifier diodes by half compared to a conventional bridge rectifier, since in each half-cycle the current flows through only one diode.

Electrolytic capacitors C3...C6 are used as a rectified voltage filter.

The IC1 chip contains a voltage stabilizer to power the electronic volume, stereo and tone control circuits. The stabilizer is assembled according to a standard design.

The use of the LM317 chip is due only to the fact that it was available. Here you can use any integral stabilizer.

The protective diode VD2, indicated by a dotted line, is not necessary to use when the output voltage on the LM317 chip is below 25 Volts. But, if the input voltage of the microcircuit is 25 Volts or higher, and resistor R3 is a tuning resistor, then it is better to install a diode.

The value of resistor R3 determines the output voltage of the stabilizer. During prototyping, I soldered a trimmer resistor in its place, used it to set the voltage to about 9 Volts at the output of the stabilizer, and then measured the resistance of this trimmer so that I could install a constant resistor instead.

The rectifier feeding the stabilizer is made according to a simplified half-wave circuit, which is dictated by purely economic considerations. Four diodes and one capacitor are more expensive than one diode and one slightly larger capacitor.

The current consumed by the TDA1524A microcircuit is only 35mA, so this circuit is quite justified.

LED HL1 – amplifier power-on indicator. A ballast resistor for this indicator is installed on the power supply board - R1 with a nominal resistance of 500 Ohms. The LED current depends on the resistance of this resistor. I used a green LED rated at 20mA. When using a red LED type AL307 with a current of 5mA, the resistance of the resistor can be increased by 3-4 times.

Printed circuit board.

The printed circuit board (PCB) is designed based on the design of a specific amplifier and available electrical elements. The board has only one hole for mounting, located in the very center of the PCB, which is due to its unusual design.

To increase the cross-section of copper tracks and save ferric chloride, the areas free from tracks on the PP were filled using the “Polygon” tool.

Increasing the width of the tracks also prevents the foil from peeling off the fiberglass laminate when damaged. thermal regime or when repeatedly resoldering radio components.

According to the drawing given above, a printed circuit board was made from foil fiberglass with a cross section of 1 mm.

To connect the wires to the printed circuit board, copper pins (soldiers) were riveted into the holes of the board.

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And this is the already assembled printed circuit board of the power supply.

To see all six views, drag the picture with the cursor or use the arrow buttons located at the bottom of the picture.

The mesh on the PP copper tracks is the result of using this technology.

When the board is assembled, it is advisable to test it before connecting the final amplifiers and the regulator unit. To test the power supply, you need to connect an equivalent load to its outputs, as in the diagram above.

Resistors of the PEV-10 type at 10-15 Ohms are suitable as a load for the +12.8 and -12.8 Volt rectifiers.

It’s a good idea to look at the voltage at the output of a stabilizer loaded onto a resistor with a resistance of 100-150 Ohms with an oscilloscope to ensure there is no ripple when the alternating input voltage decreases from 14.3 to 10 Volts.

P.S. Refinement of the printed circuit board.

During commissioning printed circuit board I had to supply the power supply.

During modification, we had to cut one track, item 1, and add one contact, item 2, to connect the transformer winding that powers the voltage stabilizer.

For the manufacture of power supplies for power amplifiers, low-frequency 50-Hz transformers are usually used. They are reliable, do not create high-frequency interference and are relatively simple to manufacture. But there are also disadvantages - dimensions and weight. Sometimes such shortcomings turn out to be decisive and we have to look for other solutions. Partially, the issue of overall dimensions (more precisely, only height) is solved by using a toroidal transformer. But such a transformer costs a lot of money due to the complexity of manufacturing. And yet it still has significant weight. A solution to this problem can be to use pulse block nutrition.

But it has its own characteristics: difficulty in manufacturing or alteration. To adapt the mind to power supply computer unit power supply, you need to resolder half of the board and most likely rewind the secondary winding of the transformer. But modern Chinese industry produces large quantities 12-volt Tashibra power supplies and the like, promising decent output power, 50, 100, 150 W and above. At the same time, the cost of such power supplies is ridiculous.

In the picture there are a couple of such blocks, above BUKO, below Ultralight, but essentially the same Tashibra. They have slight differences (perhaps they were made in different provinces of China): the Tashibra secondary winding has 5 turns, while the BUKO has 8 turns. In addition, the Ultralight has a slightly larger board, with space for installing additional parts. Despite this, they are remade identically. During the modification process, you must be extremely careful, since the board contains high voltage, after the diode bridge it is 300 volts. In addition, if you accidentally short-circuit the output, the transistors will burn out.

Now about the scheme.

The circuit of power supplies from 50 to 150 watts is the same, the only difference is in the power of the parts used.

What needs to be improved?
1. Need to solder electrolytic capacitor after the diode bridge. The capacitor capacity should be as large as possible. For this modification, a 100 µF capacitor was used for a voltage of 400 volts.
2. It is necessary to replace current feedback with voltage feedback. What is it for? In order for the power supply to start without load.
3. If necessary, rewind the transformer.
4. It will be necessary to straighten the output AC voltage diode bridge. For these purposes, you can use domestic KD213 diodes, or imported high-frequency ones. Better, of course, than Schottky. It is also necessary to smooth out the ripple at the output with a capacitor.

Here is a diagram of the converted power supply.

The blue circle marks the current feedback coil. To turn it off, you must unsolder one end so as not to create a short-circuited winding. After this, you can safely close the coil contact pads on the board. After this, it is necessary to organize voltage feedback. To do this, take a piece of twisted pair wire and wind 2 turns onto the power transformer. Then the same wire is wound 3 turns onto the communication transformer T1. After this, a 2.4 - 2.7 Ohm resistor with a power of 5 - 10 Watts is soldered to the ends of this wire. A 12-volt light bulb is connected to the output of the converter, and a 220-volt, 150-watt light bulb is connected to the power wire. The first bulb is used as a load, and the second as a current limiter. We turn on the converter to the network. If the power light does not light up, then everything is fine with the converter and you can remove the light. We plug it back into the network, this time without it. If the 12-volt light bulb on the load does not light up, it means that the direction of winding the coupling coil on the T1 coupling transformer was not correct and it will need to be wound in the other direction. Don’t forget to discharge the mains capacitor with a 1 kOhm resistor after turning off the power.

The power supply for ULF is usually bipolar; in this case, you need to get 2 voltages of 30 volts each. The secondary winding of the power transformer has 5 turns. With an output voltage of 12 volts, this results in 2.4 volts per turn. To get 30 volts, you need to wind 30 Volts/2.4 Volts = 12.5 turns. Therefore, it is necessary to wind 2 coils of 12.5 turns each. To do this, you need to unsolder the transformer from the board, temporarily wind up two turns of voltage feedback and wind up the secondary winding. After this, the calculated two secondary windings are wound with a simple stranded wire. First one coil is wound, then the other. The two ends of different windings are connected - this will be the zero output.
If it is necessary to obtain a different voltage, more/fewer turns are wound.

The operating frequency of the power supply with the voltage coupling coil is about 30 kHz.

Then a diode bridge is assembled, electrolytes and ceramic capacitors in parallel with them are soldered to dampen high-frequency interference. Here are more options for connecting the secondary windings.