S-180-12 180W 12V / 15A power supply in an unusual form factor

In my previous review of a power supply, I mentioned that I’d ordered two units for review. Today I’ll tell you about the second one.
It’s interesting in its own way and well made, but it does have some drawbacks.
As always, all the details are below the fold.

I’ve already reviewed a power supply with the same power rating and output voltage, but these two power supplies are radically different. That’s what prompted me to get this one for testing.
The review will follow the same format as always, but the comments and conclusions will be quite different.

Today I’ll start in an unusual way: with the packaging :)))
As before, the power supply came in its own little cardboard “house.” This time, though, the packaging was marked “LED power supply,” even though it has nothing to do with powering LEDs specifically, since it works as a voltage source, not a current source. In this case, however, that doesn’t really matter.
The side also shows the power rating. I immediately noticed that “150 W” had been highlighted first, then crossed out and replaced with “180 W.” But we’ll come back to that.


The first thing that sets this power supply apart is its form factor. It’s built around a U-shaped aluminum chassis that also serves as a heatsink. Power supplies are usually built around an L-shaped chassis with a perforated cover.
This design should improve cooling for the power components and reduce the unit’s size, but we’ll get to the temperature test later.


The power supply is quite compact: 200 mm long, 59 mm wide, and 36 mm high.


The connectors for 220 V input and ground, as well as the 12 V output, are located at the ends of the unit.
The output terminals are doubled, with two contacts for each polarity.
That’s because the output current is fairly high—up to 15 A—and this arrangement makes it easier to connect a load.


Each terminal block has a protective cover. In my previous review of a 180 W power supply, someone asked whether the cover opens all the way, because they’d had trouble with theirs.
The cover has fairly stiff latches, but it opens to 90 degrees.


The manufacturer lists the following specifications:
Input voltage — 110/220 V ± 15% (which is odd, since the power supply has no voltage selector)
Output voltage — 12 V
Output current — 15 A.


There’s nothing else interesting on the outside, so I opened it up.
It’s very easy to take apart: there are four screws on the sides, and once you remove them, the top cover comes off without any trouble.
The first thing that caught my eye was that the power supply uses a single-ended topology.
In my personal opinion, a 180 W power supply built around this topology is already on the borderline between good and bad.
The thing is, this topology works great at low power levels, but at higher power, push-pull, full-bridge, or half-bridge designs take over (the latter topology is used in most computer power supplies).
This power supply sits roughly on the boundary between those “spheres of influence.”


The power supply handled its first power-up just fine, which is nice in itself :)
It was initially set to 12.21 V (I only figured out why later).
The adjustment range isn't very wide: 11.75 V at the low end and 12.63 V at the high end.
After checking the adjustment range, I set the power supply to the specified 12 V.


A few photos of the power supply's main components.
1. The input filter. This time there's an NTC thermistor to limit the inrush current when the power supply is switched on. There's also a spot for a protective varistor, but they “forgot” to solder one in.
2. The input capacitor is rated at 150 µF and looks more like a branded part. It's also rated for a maximum temperature of 105 degrees. If it weren't for the undersized capacitance, I'd say it's excellent; as it is, it's only good.
3. The high-voltage transistor is held against the heatsink with an L-shaped plate. Thermal paste is present, and it looks like silicone paste.
4. There are two diode assemblies on the output, also held against the other side of the case with a metal plate and thermal paste.


Let's take it apart further. The board is secured with a single screw and sits in slots in the case. It can only be inserted or removed together with the insulating sheet.
You can see that the board is almost empty, with only the large components mounted on the top side.
That's how branded power supplies are usually made (at least, that's what it reminded me of).


The circuit board.


A couple of more detailed photos of the circuit board.
The secondary side uses precision resistors, which is good. The feedback circuit layout is also interesting; you can see that some thought went into the routing. By the way, this power supply was made by the same manufacturer as the previous 24 V model.


The primary side.


The PWM controller is an LD7575, which I hadn't come across before.
I did notice, though, that the manufacturer placed a ceramic capacitor in parallel with the electrolytic capacitor in this IC's power supply circuit. You don't see that very often, though you should.
The current-sense shunt is made up of six resistors connected in parallel.


The schematic differs slightly from that of the previous power supply.
Some component designators on the schematic are written like this: 22 (11), followed by a component number made up of several digits. This means that several components are connected in parallel, with their combined value shown in parentheses.


A few photos of the power supply's main components.
1. Input power filter components, an interference-suppression capacitor and an inductor.
2. Inrush current limiting thermistor and KBL406 bridge rectifier; this time it's a 4 A, 600 V bridge rectifier.
3. Additional interference-suppression capacitors, of the proper Y type.
4. High-voltage transistor svd12n65f. The transistor has an insulated package and is rated for currents up to 12 A and voltages up to 650 V. In my opinion, a more powerful one could have been used, but testing showed that this one is doing just fine.


1. The interwinding capacitor is also the proper Y type, which has become rare lately.
There's an empty spot next to it for another capacitor of the same type, connecting the output negative to the power supply case, but that one was also “forgotten.” I wouldn't say it's essential, but it wouldn't hurt to have it.
2. Output diode assemblies MBR20100CT; no issues here, their ratings match the power supply's output current and voltage.
A few words about the transformer. It's made properly: you can see that the primary winding uses two wires and is split into two sections (this is desirable for better coupling between the windings). The output winding uses four wires, although at these currents a litz-wire winding would be a better choice.


The output capacitors are made up of five units. Three 1000 µF, 25 V capacitors are installed before the inductor, and two 1000 µF, 16 V capacitors after it. I think they should all have been rated for at least 25 V. Ideally, the ones before the inductor would be rated for 35 V and those after it for 25 V, but even branded power supplies rarely do this.
The output inductor was disappointing. There's room for one with higher inductance and a higher current rating. I'd recommend replacing it with a more suitable one.
A quick capacitance measurement showed that the actual values match the stated ones.


That wraps up the construction and components overview. Now we can move on to testing.
For this, I put together the same kind of “test bench” as in the previous review. It included:
The power supply under test.
Electronic load
Oscilloscope
Multimeter
Non-contact thermometer


The test procedure is pretty much standard by now.
Power on, apply a load, let it warm up for 20 minutes, increase the load current, let it warm up for another 20 minutes, and so on until we reach the maximum current or the power supply gives its last squeak.
The oscilloscope probe was set to 1:1, and the oscilloscope scale was set to 0.1 V per division.
1. First, a no-load check: output voltage was 11.98 V.
2. Increased the load current to 3 A; the voltage dropped sharply to 11.65 V.


When I saw the output voltage drop sharply under a relatively light load, I immediately remembered that it had initially been set to 12.21 V.
Apparently, the load resistors on the power supply's output aren't doing their job quite well enough, so the output voltage rises at no load.
I had to adjust the output voltage to 11.99 V at a current of 3 A.
I didn't touch the adjustment any further.


1. Load current: 6 A, voltage: 12 V; voltage ripple of about 0.4 V is visible
2. Load current: 9 A, voltage: 11.92 V; the ripple amplitude has barely changed, but the ripples are more frequent.


1. Load current: 12 A, voltage: 11.84 V; ripple voltage is about 0.5 V
2. Load current: about 14 A (the load won't go any higher), voltage has dropped to 11.8 V, and the ripple has increased quite significantly, reaching 0.65 V.


As I mentioned above, component temperatures were recorded every 20 minutes.
The first reading was taken at idle, after running at 10 A for about 20–30 seconds (it just worked out that way); the following readings were taken before each increase in current.
The final reading was taken after an additional 20 minutes of warm-up to assess the rate of temperature rise. The total test time was 2 hours.
Temperatures were measured for:
The high-voltage transistor, transformer, output diodes, and output capacitors.
The hotter of the two readings was used as the output diode temperature (one diode assembly was a few degrees hotter).


At nearly the maximum load current, the power supply gets noticeably hot, so you shouldn't count on using it above 12 A.

At the end of the experiment, I captured the temperature distribution across the entire power supply. Unfortunately, I don't have a thermal camera yet, so this is the best I could do.


Summary.
Pros
A good, well-thought-out design.
It has an input filter with the right types of capacitors.
Most components are correctly selected and appropriately rated for the power supply's output.

Cons
High ripple; this could perhaps be improved by replacing the output inductor.
It gets very hot at maximum current, and unfortunately this can't be fixed with simple modifications.

My take: At the very beginning, I said I'd come back to the power rating originally stated on the packaging. I believe the original rating of 150 W is the power level at which this power supply can operate quite safely.
I was pleased with the solid design, the full input filter, and the right capacitors (which affect safety). But the high temperatures were disappointing: while they're normal for semiconductors, they're dangerous for the transformer and output capacitors.
In my opinion, the capacitors are somewhat undersized and are better suited to 150 W than 180 W.
So, in the end, this is a perfectly decent, well-made 144 W power supply—or, put another way, 12 V at 12 A.

I hope this review was useful and helps you make the right choice.

The product was provided by the store for review.