Another 12 volt power supply, but for 1 amp.
In the previous review, I said something about there being two items in the package. Today I will show you what else came to me. This power supply was ordered for a very specific purpose, but I will write about that at the end. The review will be very similar to the previous one, if you want to know more about it, feel free to click here.
Как я написал в аннотации, блок питания пришел в компании с первым. Но он не только пришел вместе, а как я понял, они еще и одного производителя, об этом говорит и внешний вид и качество изготовления (хотя у этого БП оно несколько похуже) и маркировка. У предыдущего была маркировка XK-2412DC , что означает 24
The power supply specifications. Input voltage: AC85-265V or DC100-370V Output voltage: DC 12V Output current: 1A (the site mistakenly specified 1-2A) Output power: 12 watts. In the title it was also announced about the low ripple, but we will check that separately 
I will begin by tradition with the package and hide it under a spoiler. There is nothing very interesting there and you can safely skip this point.
The power supply came in a standard antistatic bag, with standard stickers, the store number and a warning.
After unpacking it I did not see anything criminal, everything is neat, except that he was traveling dangling in a package (on this I wrote in a previous review).
The power supply is really small, a little bigger than a matchbox. The dimensions are 62.5x31x23mm, the last dimension – height, can be reduced by another 1mm because I measured with transformer pins that stick out a bit.
This power supply also has a line filter and inrush current limiter, but the filter is cut down, there is no filter capacitor before the choke. Also there is no connector, just two holes with 5mm pitch. But in this PSU the capacitor in PWM power supply circuit is 33 uF and not 10 uF as in previous PSU.
From another angle you can see the output diode and the output capacitors with the choke. The heatsinks are not provided here, and they are not really needed with this power. The diode is for 3 Ampere 100 Volt, brand SR3100, everything is as it should be.
And here is the first remark, a serious one. We used a common capacitor for 1KV as an interwinding capacitor, not Y1 which is supposed to be used in such circuits. The fact is that the Y1 capacitor is placed in such circuits for safety reasons, if it breaks down, it always breaks down, because a short circuit in such a circuit is fraught with consequences. I strongly recommend to replace it, you can unsolder it from any switching power supply, rating is not critical, the main thing is the class of capacitor.
The power transistor is “hidden” somewhere in the depth of the board, between the input choke and transformer, it has no radiator, the case is small, but about this I will say separately.
As last time, the drawing with the dimensions of the board and mounting holes.
The board is made and assembled very high quality, no complaints, moreover, here the manufacturer even fixed the SMD elements with glue, it can be seen in the place to install the output diode in the SMD housing instead of the lead wire, and you can see the other elements. This is a plus. The board is double layer, the mounting is double sided and quite tight, a couple of resistors are even under the transceiver.
As a PWM controller I used unknown to me chip 63D39, the name is very similar to the chip 63D12 from this review. As far as I understand, the closest analogue is FAN6862. The resistors, as in the last review, are as good as 1%.
For the sake of experiments I decided to connect terminal blocks to the input and output of the board. The input was a standard 5mm terminal, but I had to bend it a bit near the choke, but it can be installed without it (the photo shows it that way). On the output holes with a pitch of 3.75mm, but the terminal block was not there, the output choke is in the way.
Like last time I decided to check the characteristics of the installed capacitors. What can I say, here everything is worse, the remark to the ESR of the capacitors, as to the capacitance and voltage there are no complaints. Capacitors 470mcf x25 volts, the capacitance is normal at the rate of 1000mcf per 1 amp of output current. ESR is noticeably overestimated, about 140mOhm.
To the input capacitor complaint about ESR also applies, although to a lesser extent, but with the capacity is fine, 22 instead of calculated (for 220 volts) 12 is very good.
The first test run. It started without any problems. Startup time was a little bit delayed, about 1.5-2 seconds, because of the increased capacitance in the PWM power supply circuit of the controller.
When describing the installed components, I forgot to specify the transistor. To tell the truth, I had to literally dig it out. What you can’t do for science It was a 2N60C from fairchild. Of course the transistor is small, but experiments will show it.
Of course before starting the experiments a schematic was drawn. The scheme is necessary not only for the review, but also to help those who will buy it, as it is unlikely that life happens. Before testing it is good to know what to do next, if it burns out in the process of torture
As in the last time I have prepared different things to check. The list is almost the same as the previous one, the only difference is in the ratings of the load resistors. For the load I used a 27 Ohm resistor, a 15.3 Ohm resistor made up of three 5.1 Ohm resistors in series with a 10 Ohm resistor (added later) and a 1 Amp load, which I told you about in my battery test review.
I will be testing everything exactly the same way. Output voltage under different loads and ripple. Multimeter and oscilloscope connected directly to the output of the PSU, the load is connected to the terminals, put out on a small cable. The dropout on the cable is small, but I will take it into account in my calculations later. This time I took the recommendation of my colleague Ksiman and adjusted synchronization on the oscilloscope. So: 1. Idle mode. 2. Load 27 Ohm, current about 0.44 Ampere.
1. Load 15.3 ohms, current about 0.78 Ampere. 2. 1 Ampere load All parameters are normal, ripple about 30mV, the oscilloscope probe divider is set to 1:1, I will describe the thermal mode later.
Next I decided not to dwell on what I had received, as the temperatures were quite normal. 1. A load of 10 ohms, a current of about 1.19 Ampere. 2. 1 Amp load + 27 Ohms in parallel, current of about 1.44 Amp Everything works fine. About the ripple, it feels like it even went down, at this point I even checked if the dipstick was really at 1:1 and ran the sync back and forth, but no, everything is correct, no error.
Since I wanted to continue the experiment further, but the heating began to go beyond the allowable limits (in my opinion), I decided first to modify the power supply a bit. I cut out a plate from 1mm thick textolite, tinned it and soldered it to the power transistor. In the picture you can see that I had to trim the corner a bit. It is not a pretty solution, but it is better than nothing. In general it is not recommended to connect the metal pin of the transistor body, in this configuration, to the heatsink, this can increase electromagnetic interference. But since the plate is small and the transistor is even smaller, I thought it would be no big deal.
I wrote at the beginning of the review that there is an error on the store page about the specified current of 2 Amps. It is a mistake because even outwardly such PSU just fundamentally will not give that kind of current for a long time, besides the title of the product says 1 Amp, the description says 12 Watts of power (the same 1 Amp). If I don’t forget, I will write to the manager about the mistake.
So 1 Amp load + 15.3 Ohm resistor, total current is about 1.78 Amp. The voltage sometimes jumped to 11.90, but most of the time it was 11.91 volts, as in no-load mode. But after a few minutes or so I noticed that the LED on the board blinks with a frequency of about one time per second, the PSU went into overload protection. After disconnecting the 15.3 ohm resistor it stopped blinking and went on.
By the way, a piece of laminate, lying under the board, performs a very important function, it protects my desktop from the consequences of BP explosions.
But the oscillogram became worse, there were peaks, the total amplitude of pulsations was about 50-60mV. I would say that this is a very good result, and taking into account the fact that the PSU works in overload mode, it is excellent.
During testing I measured temperatures as I did last time. The only problem was measuring the temperature of the transistor, because it was impossible to reach it with a non-contact thermometer 
I measured the temperature of two capacitors and the choke next to them. It was impossible to measure the temperature at maximum load, the PSU went into protection before it was warmed up.
In the beginning of the review I wrote, that the PSU was bought with a specific purpose. Not so long ago I wrote a review about the converter chip and assembled a board to measure the current on the shunt. I had already wrote a review about converter chip and assembled there a board for measuring shunt current. So the power supply is intended for the same device, the batteries were also intended, but they are not suitable for me In my future device I would like the supply voltage a little more than 12 volt, because after it goes down to 8.5 volt. I decided to change the output voltage of this PSU by putting another resistor in parallel to the resistor of the lower arm of the OS divider. The closest thing I had on hand was a 20k resistor.
The voltage I got is about 13 volts, I think that’s enough. This board will still be used in one of the future reviews and with this modification, so who is interested, I advise to make a mark in the margin Generally speaking the voltage of such PSUs can be safely increased by 10-15%, maximum 20%, but I think 10 is enough for me.
And here is a comparison of two power supplies, the first thing that came to my mind when looking at this picture, the words from the poem Mayakovsky – Krokha son to his father came :)))
So summary: Pros: Good enough workmanship Very good electrical parameters Compliance with the declared parameters and even exceeding them. The price, well, the price as a price, it is hard to judge, in my opinion, normal, at least for such a quality.
Minuses Wrong interwinding interference suppression capacitor, quite a big, but easily correctable minus. The output electrolytes could have been of better quality, although the capacitance is fine.
My opinion. In my opinion the PSU is quite decent, though tiny. Yes, the current is ridiculous, you can hardly power the backlight in the kitchen from it, but the quality is pretty good. As a built-in power supply for some appliance, it is more than sufficient. I was pleased with very low ripple, but was very upset by the interwinding suppression capacitor, it is necessary to change, but it costs a penny and is found in all switching power supplies. The complexity of its rewiring is commensurate with soldering the input/output wires.
The power supply for the review was provided by banggood store.
I think that there will be people who are looking for a similar PSU, and just interested in the structure of such things and my review will be helpful to them. Questions and suggestions are always welcome in the comments:)
12 volt 0.5 (1) amp power supplies
Many readers know how I like to write reviews about power supplies. And so it just so happens that I have gotten my hands on some of these devices. The thing is that not so long ago a variety of power supplies “off-the-shelf” appeared in one well-known store, and I’ll tell you about one of them today.
Some time ago I wrote in the comments that I was going to review various PSUs and I meant exactly these PSUs. I ordered several kinds of them, three small “used ones” and one new one, quite powerful. I will tell you about them “by seniority”, so I will start with the smallest one. Since I use power supplies often, I ordered them in lots of three, but there are lots of 1, 5, and 10. This power supply is no exception and will be used in one of the reviews I plan to prepare relatively soon.
The power supplies are shipped in separate large packages, not three in one package as I originally thought. That is, in fact, the warehouse just puts a mark on how many items to put in the cart. There were no complaints about the packaging, everything is generously wrapped with polyethylene foam.
In the header I wrote the current of 0.5 (1) Amps. I will explain what this means as the review progresses. The product page said 12 volt, 1 amp, which is more than understandable. It also says that the power supplies are disassembled, i.e. not new, but forged from somewhere. My experience is that such PSUs are often of better build quality and circuitry than new ones.
The PSUs are quite compact with actual size of about 57x35x19mm.
The board layout is pretty tight, partially filled with silicone which I had to cut off in some places later. Since the board is a CU, you can see the cut wires.
The boards have different color of goethinax, and released at different times, but all three in the range of 2007-2008.
Also on the boards was found and the model marking – 3A-064WU12, by which I found their real characteristics. 12 Volt, 0.5 Amp, 6 Watts, efficiency at 115 Volt – 74%. There is also the name of the manufacturer there – Eng Electric Co., LTD. So the power supplies are quite brand name.
The product page also mentions 0.5 Amps, but it is mentioned in passing. I think what is meant is 0.5 rated, 1.0 short term. But in any case, these characteristics are correct and should be specified in the characteristics section, not in the name of the product.
Ok, back to our power supplies. 1. On the input is a 1 Amp fuse. The fuse is delayed (T- Trage – slow German), this is due to the pulsed nature of the current when the power supply is turned on. 2. Also present at the input is a varistor, 7mm in diameter and rated for an amplitude voltage of 470 volts. Next to it you can see a 0.1μF X-type suppression capacitor. Next is the in-phase choke and the diode bridge. 4. The primary and the secondary side are connected via a Y type capacitor with a capacity of 2.2 nF. Generally it would be possible to give five points for the filter, if not for two disadvantages: 1. No thermistor, but maybe there is no point, the capacitance of the input capacitors is not very high. 2. It has no discharge resistor in parallel to the capacitor type X. Without it the PSU can “pinch” if you take the plug out of the socket and immediately grab the pins.
That said, a plus to the manufacturer for having a noise filter and varistor.
1. Two capacitors with 6.8 uF each are installed at PSU input, total capacitance is 13.6 uF, which is quite normal for the declared capacity of 6 watts. 2. But the capacitors are not just connected in parallel, there is an additional choke between them. In the photo you can not see the color marking brown-black-red-gold. 3. A quite famous VIPer-12A PWM controller controls the power supply. 4. Next to the controller is the power supply filter capacitor of this controller. Often these capacitors can malfunction and “drink blood” unnoticed, since they appear to be normal. If the PSU is a CU, I recommend replacing them first.
The silicone that the board is filled with has a slight yellow tint to it. At first I thought it was because of the heating of the components, but the color is the same even near the components that are not heated.
As I said before I used a VIPer series PWM controller. This is a family of integrated PWM controllers. Inside the chip there are not only PWM controller but also high voltage transistor, overload, overheat and overvoltage protection circuits. I usually use similar controllers from another, not less famous company – Power Integrations, I like them better. But by and large they are very similar in many ways. It is stated that for the DIP-8 case the power is 13 watts in the narrow range (230 volts) and 8 watts in the wide range (115-230 volts). Since the PSU is declared as 115-230, it turns out that the real power is up to 8 watts.
The block diagram shows the output transistor as well as the protection circuits. Basically I could tell you more about all this, but in my opinion this is more of a topic for a separate article.
The secondary part of the power supply contains: 1. A 2 Amp Schottky output diode, which again indicates a maximum output current of no more than 650-700mA. A ferrite bead is present on one of the diode leads. 2. The output capacitors are two, 470 and 220µF, as in the case of the input capacitors manufacturer Samxon. I can not say that the capacitors are high class, rather average, originally it is an OEM from Matsushita sold under its brand. I was personally disappointed by the fact that they are rated at 16 volts, not 25 as they should be at this voltage. 3. There is room between the capacitors for a choke to reduce ripple, but a jumper is installed instead. 4. 4. The regulation circuit is standard, a regulated AZ431 (TL431 analog) and an EL817 optocoupler (PC817 analog).
There are two things I did not like about the output circuit: 1. 2. The capacitors are 16 volt and not 25.
Otherwise it was pretty well done.
The quality of the soldering is pretty tolerable. At the bottom are the rest of the components as well as a couple of stabilizing diodes which I will talk about below. The distance between the high voltage side and the low voltage side is quite sufficient. There are no protection slots, but since the PSU was originally designed to be installed in a closed case, it is acceptable to do so as well.
The power supply schematic is generally standard and is actually made according to the PWM controller datasheet. Of the extra little things that are very useful in terms of load safety I will note a couple of stabilizing diodes. ZD1 – 14 Volt, parallel to the output, designed to keep the output voltage from going above 14-14.5 Volt. ZD2 – 16 Volt, parallel to the optocoupler transistor, to limit the output voltage in case of a feedback break or failure.
I have been told several times in the comments that I did not approach the ripple level tests correctly. Well, I have taken the information to heart and will try to do it more correctly this time, and next time as well.
The thing is, when measuring, I usually connect using the “wrong” way, as it is more convenient. In this case, the ground wire of the probe works partly as an antenna, on which interference is induced and distorts the oscillogram. This method is not very important for the overall evaluation, but it is indeed incorrect. The picture below is from the description of the power supply test methodology.
To get a correct waveform you must connect the probe without long wires directly to the output of the power supply.
As you can see from the photo, the oscilloscope probe in addition to the ground wire with the crocodile has the ability to connect right next to the probe itself. Using “sticks and ropes” I made some kind of special probe for checking power supplies, the most uncomfortable was to connect to the central contact, because it has a conical shape. Two capacitors are connected in parallel to the input, an electrolytic 1μF 63V and a ceramic 0.1μF.
Of course, what I have shown above can be called a hack, but even quite well-known companies (the same Power Integrations) are not exempt from doing such things, though they use a connector for it, but I didn’t have it :(. The photo from the application description of PWM TOP series controllers from Power Integrations, the ratings of elements are taken from the same place.
The oscilloscope probe was connected directly to the output pins of the power supply, the load to an additional soldered wire. During the preparation I compared the oscillogram at idling speed with and without load, there was no difference.
The first thing that surprised me when I turned it on was the output voltage of 12 volts to at least the second digit. By and large it doesn’t matter and even if the voltage was in the 11.5-12.5 volt range, I would say that’s fine, but it’s still nice. 1. Idle. 2. 0.25 Amps 3. 0.5 Amp 4. 0.75 Amp 5. 1 Amp 6. 1.2 Amps.
You can see that the output voltage began to drop only when the load current is above 0.75 Ampere, which is one and a half times the stated voltage. Before that the voltage was very accurate and dropped about 0.001 Volts for every 0.25 Ampere load.
I would not call the ripple level small, at 0.5 Ampere rated current it was 100mV, but even with overload it was not higher than 140mV.
Research showed that the maximum current at which the power supply holds the output voltage is 0.9 Ampere. And that is for a non-new PSU and at almost twice the output current.
I have also been told that it is wrong to test power supplies using electronic loads. In this case I disagree with this conclusion, because in linear mode the load’s field-effect transistors are essentially the same resistors, but with feedback. In any case, for the sake of experiment I compared the behavior of the power supply when loaded with an ordinary 10 ohm resistor (that I had on hand). In the photo you can see that the plus load probe is not connected. The voltage of course dropped, because the current is clearly higher than the calculated.
On the left is an oscillogram of a 1 Amp load using an electronic load, on the right 1.08 Amp and a resistor as a load. I would not say that there is any global difference.
The next step, the heat test. For this I covered the power supply with a makeshift “case” and loaded it with 0.25 Amp to 0.9 Amp in series. A current of 0.9 Ampere was chosen because at this current the PSU still holds the output voltage normally. Each test took 20 minutes, total time of the test was 1 hour and 20 minutes.
All data were tabulated and a new line was added and now the voltage at the beginning of the test (V1) and at the end (V2) is shown. This addition makes it possible to trace the voltage drop from the warm-up. At first the voltage itself may seem less stable than in the test above, but there I connected directly to the contacts of the PSU, here using a piece of wire, so the difference came out. But I can say, that there is practically no temperature dependence of the output voltage. But it turned out, that with a load current of 0.9 Ampere the PSU reduced the output voltage after about 5-7 minutes.
The maximum temperature of the components after the test was about 100 degrees for the transformer and 118 for the PWM controller. With current up to 0.75 Ampere (1.5 of rated), there was no overheating.
This was what the output power limit looked like. I repeated the test on the already warmed up PSU to make it more obvious. I started, in 6 minutes the voltage had some drops, at the 20 minute mark I took off the cover, voltage had some increase, in about 15 minutes I blew on the board and it came back to normal again.
Above I complained about the lack of output choke, so I decided to compare this defect, and at the same time to compare how the result will change. I used a small homemade choke, literally whatever was on hand. The size is small, wound with 0.68mm wire.
The result, as they say, is plain to see. 1, 2. 0,5 Amp, left without choke, right with choke. 3, 4. 1.0 Ampere.
I should warn you right away, the choke should not have a large inductance, because by increasing the inductance the ripple on the first filter capacitor will start to grow strongly and it will be harmful both for the capacitor itself and for the protective stabilitron, installed in parallel to it. You will have to change the capacitor to a similar one, but with 25 volts, and to move the stabilitron to the output of the PSU.
That’s all. In short the power supplies even if they have some disadvantages, mentioned in the review, but in general they are pretty good and can be used for various home-built devices, which do not need much power (6-8 Watts). The power supplies are quite branded and of relatively high quality. They are a bit more expensive so if you buy them by the lot 3 or 5.
I hope this review was helpful and I will always be happy to get any questions in the comments.
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