A 12 V, 6–8 A power supply that pleasantly surprised me.

In one of my reviews, I showed how to build a decent power supply yourself and complained about how rarely good power supplies are available for sale. I liked this one just from the picture, but since pictures can be misleading, I decided to take a closer look and put it through its paces.
The review includes a description, photos, tests, and an analysis of a small design mistake.
Read on for the rest.

My readers probably remember the review “12 V 5 A power supply, or how it could have been made.” This power supply reminded me of the one I built at the end of that review :)

But tests and checks are all well and good. As usual, though, I’ll start with how it was shipped and how it arrived.
The power supply didn’t arrive alone; I’ll tell you about the other item another time. I think it’ll be just as interesting. It shipped quickly and took 8 days to arrive, according to the tracking.
I did have an issue with the packaging, but since not everyone likes packaging photos, I’ll hide a few under a spoiler.

Quick specs:
Input voltage: 85–265 V
Output voltage: 12 V
Load current: 6 A rated, 8 A maximum.
Output power: 100 W (maximum)

The board is fairly compact, measuring 107 × 57 × 30 mm.


There’s a drawing with more precise dimensions, which I think will be useful.


The board itself looks very neat and matches the store photo exactly, which pleasantly surprised me.


The board has fairly large heatsinks and is an open-frame design, meaning it’s intended to be installed inside some device and doesn’t have its own enclosure.
I didn’t buy it on a whim :) I have an idea for modifying one of my devices, but since I wasn’t sure about the quality of this power supply, I decided to order and try just the power supply first. So there’ll be more to come. Well, at least I hope so.


The board has an input filter, an inrush current limiter, and a screwless terminal block for the 220 V input.
The power transformer has a DC12V-8 sticker.
The transformer’s output winding is made up of 5 wires.


The soldering is very neat, the leads are trimmed quite short, nothing is sticking out, and all the flux has been cleaned off. No components are missing.
The board is double-sided, with components mounted on both sides.
There is one minor issue, though: only one mounting tab on each heatsink is soldered in place.
I don't think that's a good idea. It's unclear why they didn't solder both.
And the product photos in the store show exactly the same thing.
One thing worth noting is that the output voltage is measured at a point as close as possible to the output connector. That's a plus, as it helps maintain the output voltage accurately.


A closer look at the board's main components.
It uses a CR6842S PWM controller, which is a direct equivalent of the better-known SG6842 controller.
Almost all the resistors are precision parts, rated to within 1%, as indicated by their four-digit markings.


The power transistor is an Infineon SPW20N60S5, rated at 600 V and 20 A, with an on-resistance of 0.19 Ω.
One more minor issue: the mounting screw was tightened too much and pressed the insulating sleeve in. The transistor is still insulated from the heatsink, and the heatsink itself is isolated from the other components, but it does detract from the overall impression a bit.
The transistor is insulated from the heatsink with a mica sheet.

A slight digression: you can see a small electrolytic capacitor in the photo. Judging by the soldering, it was either installed later or replaced. This had no effect on operation (or almost none).
The thing is, if the load suddenly jumps from zero to 4 A or more, the power supply may shut down for 0.5 seconds. I'd recommend replacing this electrolytic capacitor with something like 47 µF, 50 V.
If you don't expect to use it under those conditions, you can leave it as is.


The output rectifier is an ST stps41h100ct, rated at 100 V and 2 × 20 A.
The heatsink is actually flat; it just looks that way in the photo :)


You can also see a pair of 1000 µF, 35 V output capacitors, the output filter inductor, and the power-on indicator LED.
This one has a standard screw terminal installed.
Though if you ask me, connectors are completely unnecessary on a board that's meant to be built into something.


The output capacitors have plenty of voltage headroom, which is great.
While I was at it, I checked their capacitance and ESR, and the results were pretty good too.
The meter showed the combined capacitance and ESR. Dividing that between the two capacitors gives roughly 1050 µF and 30 mΩ each.
The capacitors probably aren't from a well-known brand, but their specs are perfectly decent. I was pleased to see a 35 V rating; I usually use 25 V capacitors in my own power supplies.


And, while I was at it, I checked the input electrolytic capacitor too.
It's marked 82 µF, 400 V, 105 °C.
The capacitance is almost within spec, and the ESR is fine.
The capacitor is made by Taicon.


And of course, I drew up the schematic for this power supply. The component designators mostly match those on the circuit board.


For testing the power supply, I put together this pile of assorted stuff :)
Nothing unusual:
Three 10 Ω load resistors and one resistor bank totaling 3 Ω (five 15 Ω resistors connected in parallel), plus a fan.
Multimeter
Non-contact thermometer
Oscilloscope
Various connectors and wires.



Summary:
Pros
High-quality construction
Components are quite good quality and have plenty of headroom.
Meets the stated specifications.
Excellent output voltage regulation accuracy
I don't see any need for modifications.
Low price.

Cons
A note about the packaging (the store's fault)
One of the mounting contacts on the heatsink wasn't soldered.

My opinion.
To be honest, I liked the look of this power supply as soon as I saw the store photo, and I already had some confidence about what I would get in the end. But seeing something is one thing; trying it out is another.
The power supply left me with a positive impression. It would be a great fit for building into a DIY device.
Of course, it has a few drawbacks, but they're minor compared with the advantages.

The power supply for this review was provided by the banggood store.

I hope my review will be useful.
Of course, you could say I'm singing the product's praises, but I've been working with power supplies for about 15 years. I've built more than 1,000 of them in that time, and I've lost count of how many I've repaired and modified. So when I see a good product, I can't help praising it. I've seen better ones, especially industrial-grade power supplies, but they come with a different price tag.
You can also consider an option for this kind of power supply, but with lower power.