Compact built-in PLF12A-12 power supply, 12 V, 1 A

It's been a while since I reviewed a power supply, so I decided to make up for that by buying a few different compact units. As usual, this review will cover the inspection, tests, and conclusions.

I actually bought more than just power supplies. A few days ago, I stopped by a radio parts store in Kharkiv, better known as Kosmodrom. It's on my way home from work, but I never seem to have enough time to go in, so I came home with a big bag of assorted hardware. Almost everything is for various reviews, but some items are just things I picked up, while others are components for high-power electronic loads, modifications, and so on. I think you'll be seeing all of this fairly soon.


While putting together my order list, I noticed a series of power supplies from SANMIM and picked up three models with different power ratings to try out. If I like them, or if you're interested in power supplies from this manufacturer or other products from the Kosmodrom store, send me links. I'll buy them to test and show you what they're like.
Since the store only ships within Ukraine, I'll try to find and post AliExpress links at the end of the review for readers in other countries.


I'll start with the smallest one, the PLF12A-12. I liked it right away because the manufacturer provides a fairly detailed datasheet, though unfortunately it's in Chinese: link.


There are actually three power supplies in this range: the PLF12B-12, PLF12A-xx, and PLE12C-xx series, where xx indicates the output voltage.
The series look very similar, and it's easy to mix them up at a glance. The difference is that the power supplies have slightly different layouts. The PLE12C-xx has no X-type EMI suppression capacitor and a lower input filter capacitor value, but it does allow adjustment of the output voltage. The price is about the same. The PLF12B is the cheapest, but it has neither an input X capacitor nor output voltage adjustment.


The build looks very neat: everything is installed straight, and the larger components are secured with sealant.


The only thing is, there are no terminal blocks or connectors on the board. The assumption is that you'll solder the connections or install connectors yourself.
The input uses an NS39-W3P connector, but without the middle contact. For the output, use any suitable terminal block with a 4 or 2.5 mm pitch.


This series comes in five output voltage options: 5, 9, 12, 15, and 24 V. I wanted to buy the 15 V version, but unfortunately it was out of stock.


The datasheet also includes a drawing with the overall dimensions.


And, of course, here's a comparison with a standard matchbox.


At this point, the power supply reminded me a lot of another model with the same specs, 12 V, 1 A, which I reviewed some time ago: review. Though it's probably more similar to the PLF12B-12, which is actually a little cheaper.


Anyway, I've gotten a bit sidetracked. Time for a closer inspection.
1. It has both an input filter and a fuse with a thermistor. The only thing missing for a complete setup is probably a varistor.
2, 3. The input capacitor is 15 µF, which is more than enough for 12 W at an input voltage of 198–242 V, but there's no headroom for a 115 V input. The capacitor is made by Aishi. I've come across them before; they're a decent Chinese manufacturer. At any rate, I'd rather see these capacitors than Chinese counterfeits labeled "Rubicon" and "Nichicon".
4. The high-voltage transistor is an SVF4N65MJ, rated for 650 V and 4 A: datasheet.
5. The output uses capacitors from the same manufacturer, rated at 680 + 470 µF and 25 V. There's also a Y-type interwinding EMI suppression capacitor.
6. There is also an output inductor to reduce ripple, so overall, everything looks great so far.


All the other components are on the underside of the circuit board: the bridge rectifier, PWM controller, and feedback components.


I couldn't identify the PWM controller, but its pinout is the same as the 63D39 or FAN6862.
Judging by the resistor markings, they're probably precision resistors, but we can check that later by looking at how the power supply performs.


The circuit is almost identical to the one in the XK-1205DC from my old review, but this one has a few extra components in the feedback circuit, a more powerful transistor, and resistors in parallel with the input X capacitor—as well as the capacitor itself.


As I already mentioned, the output voltage is fixed and measures 12.07 V with no load.


Load tests.
The power supply handles a load current of up to 1.5 A without any problems. Even after running warm for an hour, the output voltage remains very stable, varying by just 10–20 mV.


When cold, the power supply delivered 1.6 A, or almost 20 W, without any problems. It shuts down abruptly on overload rather than gradually as the current increases.


Next came the usual warm-up cycle and temperature measurements, but I found that this power supply has a quirk.
First, I ran it at 0.5 A for half an hour, then at 1 A for another 20 minutes. Since it was performing so well, I raised the current to 1.25 A, and after about 10 minutes the power supply shut down. Trying to restart it immediately triggered the protection again. After letting it cool for about half a minute, it delivered 1.25 A without any problems.
You might think the overtemperature protection is kicking in, but as far as I know, the temperature sensor on PWM controllers like this is usually external and connected to the third pin. Here, there's just a resistor.
My only guess is that temperature somehow affects the current protection threshold.

In any case, the protection is there and it works.


Power supply temperature after 30 minutes at 0.5 A, after 20 minutes at 1 A, and during a repeat test just before shutdown when the overtemperature protection kicked in.
In all modes, component temperatures stayed below critical levels. For example, the transformer never got hotter than 70–80 degrees, while the transistor and output diode ran hottest, reaching 90 degrees at 1.25 A.


I also measured efficiency. Below are the power consumption figures with no load and at 1 A and 1.5 A.


Efficiency plotted as a graph. The measurement points are spaced at 200 mA increments of load current, except for the last one, which was taken at 1.5 A instead of 1.6 A.


An equally important, if not more important, test is measuring output ripple. This is where most cheap power supplies fall down.
The oscilloscope probe was connected directly to the power supply's output terminals.


The datasheet specifies ripple of no more than 100 mV, but in reality the ripple is about 7–10 times lower.
1. No load
2. 0.5 A
3. 1 A
4. 1.5 A
5, 6. No load and at 1.5 A, using a different time base.

In all modes, the oscilloscope was set to its lowest available setting—5 mV per division—and ripple was around 10 mV, which is an excellent result.



After testing, I can say without hesitation that I like this power supply, both for its build quality and components, as well as its performance. It easily meets its rated specs, and its output ripple is excellent. It also has overload, short-circuit, and overtemperature protection.
You could say that its price-to-power ratio isn't great, and that for a little more money you can get a much more powerful power supply. But this one is designed for applications where size matters, and that's a whole different story.

This power supply is also available on AliExpress, where it costs $4.24

That's all for now. I hope you found this useful.