Another power supply, this time 12 V, 50 A, or 600 W

This power supply was ordered together with its 24 V, 20 A “brother.” Since the two power supplies are very similar, I’ll sometimes refer to its review, so here’s the link right away.

This review will be written in a style my readers are more used to, though with a few changes.
Anyway, let’s get to the description.

This power supply arrived in exactly the same packaging as the previous one. From the outside, the only difference is the label visible through the box’s window.


The power supply’s design and dimensions are identical to the previous model, as well as to the 360 W power supply I reviewed recently.
From left to right: 360, 480, and 600 W.


Last time, I wrote that the terminal cover wouldn’t open all the way. The metal part of the cover on the previous power supply was slightly bent, preventing the terminals from being fully exposed.
This time everything is fine, so the problem wasn’t with the power supply but with the packaging or shipping.
By the way, this isn’t the first time I’ve noticed that one of the protruding corners on the bottom of the case gets bent during shipping on power supplies I receive, although I wouldn’t call them flimsy.


According to the label, the power supply is rated for 600 W at 12 V; that’s the information given in the review title.
But if you look closely at the second label, you’ll see that the manufacturer doesn’t recommend loading it beyond 80% of its maximum power. Put simply, you could say that 600 W is the peak rating and 480 W is the continuous rating, but I’ll come back to that later.

There’s also a warranty seal, but it’s damaged. I don’t think anyone opened the power supply; it was more likely damaged in transit. The power supply was made in January and I received it in March, so it’s fair to call it pretty fresh.


The terminal block has three pairs of output terminals. In my opinion, that’s a bit too few for currents this high, giving around 16–17 A per pair.
To the left of the terminal block is a trimmer for adjusting the output voltage.

As with the previous model, this power supply has active cooling. Fan speed control is claimed, but in practice it runs in two modes: low and high. The high-speed mode kicks in at a load of around 50 W.
The fan is quite powerful, at least for a unit of this size. It’s hard to say how noisy it is: you can definitely hear it, though calling it loud would be a stretch.


Undo a couple of screws and remove the top cover.


I suspected the previous power supply and this one would be very similar, but I didn’t expect them to be this alike... They’re practically twins.
Actually, on closer inspection, there’s a small but significant difference: the output load resistor has been moved. This should make the output voltage more stable as the unit heats up; I pointed out this design flaw in the previous review. That said, it only showed up when running without the fan. There were no problems in normal operation.


A comparison of the 360, 480, and 600 W power supplies.
The first uses a classic two-switch topology with a half-bridge, while the second and third use single-ended forward converters.


Having learned the hard way, I now always check how firmly the transistors and diode assemblies are pressed against the case before taking anything apart. There were no problems here, and there’s thermal paste between the components and the thermally conductive pad.


But let’s take a look at the design.
There is an input filter, though I should point out right away that the input bridge rectifier is a very budget option. It uses discrete diodes rated for 3 A, while the power supply’s input current is also around 3 A. In reality, two pairs of diodes conduct alternately in the bridge, but I won’t get into the weeds here. Simply put, the bridge rectifier is just barely adequate.
I wouldn’t call the input filter particularly good either, but the fact that it’s there is already a plus.


As with the previous model, the installed capacitors are rated at 470 µF. They’re connected in a 2S2P configuration, i.e. series-parallel. In this configuration, the filter capacitance is equal to that of a single capacitor, or 470 µF, which is too little for 600 W.


The output filter uses three 3300 µF capacitors rated at 25 V. The capacitors are also marked LowESR. The capacitor manufacturer clearly isn't a well-known brand, though, so I took that claim with a grain of salt.
A voltage rating of 25 V is fine, but the capacitance is clearly on the low side: about 10000 µF for a current of 50 A.


All right, let's get the turtle out of its shell pull the board out of the case and continue the inspection.
Last time, a screw fell out of the case at this stage. Everything was fine here, but that doesn't change the fact that you should inspect any no-name power supply before using it.


The safety-critical circuits use proper Y capacitors, so no issues there. But between the output negative and the ground conductor there's a plain high-voltage capacitor (it's right at the top of the photo). This is also fairly common and safe in this application.


The inverter uses two high-voltage transistors, SPW20N60S5, made by Infineon. They're decent transistors; the one disappointing thing is that there's almost no voltage headroom, since they're rated for 600 V. And once again, they're different from each other. On the other hand, last time the supply had IRFP460s, which are only rated for 500 V, and it passed the test just fine.

The output diode assemblies are another matter. The installed MBR4060PTs are rated for 60 V and 40 A according to the datasheet. The question is whether that 40 A rating applies to the whole assembly or to each diode, since it varies from one part to another.
You might ask: but there are two assemblies. The thing is, in power supplies with this topology, the diode assemblies aren't connected in parallel; they operate alternately, and each one carries the full output current, or even more.
If the current rating applies to each diode, there's almost no headroom. If it applies to the whole assembly, it'll be significantly overloaded.


Although the power supply is rated at 600 W, the output inductor is exactly the same size as the one in the 480 W version. What's more, it's also wound with four wires of roughly the same gauge. The difference is that last time the current was 20 A, and now it's 50 A.


There are no changes on the underside at all. The power supply's “heart” is still the familiar UC2845 PWM controller.


As last time, I found no issues with the input circuitry or the feedback loop, but I did spot a safety concern.
I've highlighted the problem area in the photo. It was there last time too, but I didn't notice it.
On closer inspection, you can see that the primary-side traces run quite close to the power supply's output negative conductor (almost in the center of the highlighted area).
To the right, the high-voltage and low-voltage sections are separated by a ground conductor and are generally safe when the supply is grounded. But a small section has been left unprotected.


On the other hand, the manufacturer really went to town on increasing the trace cross-section: several heavy-gauge wires have been soldered on top.


This time I didn't redraw the power supply schematic, since it's practically identical to the 480 W version. The only differences are a few components, which I've marked in color.
There may be other minor differences, so I can't guarantee a 100% match, but I did check most of it.


Of course, there are tests to run, but first, a preliminary check.
The voltage was a little high on first power-up, but the adjustment range turned out to be quite limited: you can't set it below 12 V.
I couldn't raise it much either. Above 13.5 V output, the power supply started making suspicious noises. It did manage to reach about 16 V, but I only did that briefly, since I didn't want to kill it before its time.
One positive change is the very low output-voltage drift: after five minutes, the voltage had changed by just 0.003 V.


As I mentioned above, the input capacitors were rated at 470 µF, and I complained that “that's not going to be enough.” Their actual capacitance turned out to be even lower, just about 350 µF, which is really poor for 600 W.
The output capacitors match the stated value, measuring about 10500 µF in total.


The biggest problem while preparing this review was the load test. My regular electronic load can handle about 350 W continuously, or 500–600 W for short periods. But I wasn't interested in a short test, so I needed something to load the power supply with.
My first thought was to build four simple current regulators using powerful KT825 transistors, which would have been the right solution. I even found these transistors at home (although it would have been more convenient to use a KT827, but I only had one) and four large heatsinks. But I also needed low-resistance 0.1 Ω resistors rated at around 5 W, and I didn't have any at home.


Then I remembered that about 9 years ago, when we were renovating and installing the lighting, I had stocked up on some halogen bulbs. As it turned out, none of them had burned out in those 9 years, so the spares had just been sitting around.
So I grabbed four 12 V, 50 W bulbs, which should have provided the missing 200 W in total.


This is the test setup I ended up with. The heatsinks came in handy too, though in a slightly different role: as stands for the bulbs, so they wouldn't accidentally burn anything.


The first test was with no load; for the second, I connected all four bulbs.


At first, the bulbs drew about 18.2 A, but a repeat measurement a few minutes later gave exactly 18 A. At 12 V, that's 216 W.


About 20 minutes later, I brought the electronic load into play and used it to add almost another 16.8 A. That brought the total load current to 34.8 A. I ran some tests later, though, and I'm inclined to think the actual current was closer to 34.7 A.
At 11.95 V, that's 414 W.


Another 20 minutes later, I raised the load current to the power supply's maximum.
Since the voltage had dropped slightly, the current through the bulbs fell to 17.8 A. That's what I meant by correcting the previous measurement: if it was 18 A initially and 17.8 A at full load, the average is 17.9 A.
So the bulbs were drawing 17.8 A, and I dialed in the remaining 32.2 A with the electronic load, for a total of 50 A. The output voltage dropped to 11.91 V, and the total power was 595 W.


I ran the test in this mode for about another 20 minutes, bringing the total test time to 1 hour.
I usually measure component temperatures during a test, but this time I had to break with that habit. Opening up a power supply that's not only switched on but also sitting between the electronic load and four bulbs—and then leaving it without cooling while I take measurements—didn't seem like a good idea. To be honest, I didn't do it for two reasons:
1. At the very least, it's unsafe.
2. At worst, it's pointless: components start heating up rapidly as soon as they're left without cooling, so I'd measure anything but their actual operating temperature.

Besides, when there's a 700 W heater humming away on the table next to you and you're constantly expecting surprises, you don't feel much like experimenting :)

I did take measurements in the end, just a little differently.
First, I used a thermal camera to "look" at the temperatures through the gaps in the case.
1. At a load of about 400 W
2. At maximum power.

3. At the end of the test, I removed the load, quickly opened the cover (it wasn't screwed on) and took a few thermal images.
First, an overall view.


Then I checked various components. The power supply was already cooling down, so the measured temperatures were dropping too.
1. Transformer core: 77 degrees; winding: 107
2. Output inductor: 87.
3. Here I tried to check the output diode assemblies, but they were noticeably cooler than the other components.

Overall, as far as heating goes, the air coming out of the power supply was noticeably warm. There was also a smell of overheated varnish while it was running, though the bulbs and electronic load could have been the source of the smell too.
All of this happened at maximum power. At 2/3 of maximum, things were quite acceptable overall.


As for ripple, I can start by saying that it's fairly high, reaching 250 mV. But considering the output current was 50 A and the power was 600 W, I'd say it's quite acceptable—I expected worse.
1. No load.
2. 1/3 power
3. 2/3 power
4. Maximum power.


And the last test—or, more precisely, calculation—was the power supply's efficiency.
1. No load.
2. 1/3 power: output 216 W, input 243 W, efficiency 88%
3. 2/3 power: output 414 W, input 473 W, efficiency 87%
4. 100% power — 595 W output, 709 W input, 84% efficiency.
Of course, this measurement has a fairly large margin of error, but in my opinion, the efficiency remains at a pretty decent level.


That’s it for the inspection and testing; time to sum things up.
In my opinion, the manufacturer has clearly overstated this unit’s power rating. It would be more accurate to call it a power supply rated for 450–480 W continuous output, but capable of delivering up to 600 W for a while. One possible use would be heating something, where a higher power level is needed initially to warm it up, followed by a lower level to maintain the temperature.
It’s worth noting, though, that this power supply doesn’t seem particularly reliable over the long term. The first components likely to fail are the output capacitors and the fan. Like many other budget power supplies, this unit also has no protection against overheating or fan failure. If the cooling system fails under a load above 50%, the consequences could be serious.
I was a little surprised that the output inductor is clearly overloaded with current: its winding wire is obviously too thin for currents of 40–50 A. I’d even say its operating current is closer to 30 A, but the power supply passed the test, and that’s a fact.

As for its electrical performance, the power supply proved capable of delivering even the claimed 600 W, not to mention the caveat on the label that it’s rated for 80% of the maximum. However, some components are operating at the edge of their safe limits.

If you’re going to modify this power supply, you should:
1. Increase the input filter capacitance
2. Replace the bridge rectifier with a higher-power one
3. Rewind the output inductor
4. Replace the output capacitors with higher-quality ones, possibly increasing their capacitance at the same time.

Why did I go into all this detail? In my opinion, at a price of $27, this power supply might interest someone as a modification project, but that’s just my personal opinion.

That’s all for now. As always, I look forward to your questions and comments. I hope you found this review useful.