Compact Hi-Link HLK-PM12 power supply

There are surprisingly few reviews of power supplies like this. That’s understandable: buyers are usually more interested in high-power models than in a tiny unit rated at just 3 W. But compact models are exactly what you need for various low-power devices, especially if they’re highly reliable. Today I’m reviewing just such a power supply, made by Hi-Link.


I ordered this power supply as an add-on to bring down the overall shipping cost, since shipping from this seller costs 75 cents but is split between items when you order several at once.
The listing offers three models:
HLK-PM01 - 5 V, 0.6 A
HLK-PM03 - 3.3 V, 0.9 A
HLK-PM12 - 12 V, 0.25 A.
The modules cost $2.16–2.32. The 5 V model is the cheapest, and the 12 V one is the most expensive.

Looking at the voltage and current ratings, it’s clear that these are 3 W modules. There are similar modules with other power ratings, as well as models from other manufacturers.
For example, the HLK-5Mxx series is rated at 5 W. Mean Well makes the IRM-02-xx, IRM-03-xx, IRM-05-xx, PM-05-xx, IRM-10-xx, PM-10-xx, IRM-15-x, PM-15-xx, IRM-20-xx and IRM-30-xx series, rated at 2, 3, 4, 10, 15, 20 and 30 W. There are even “monsters” like the IRM-45-xx and IRM-60-xx, rated at a whopping 45 and 60 W.
And that’s not even counting the many other manufacturers: Recom, Power Mate, Power-One, Motien, PEAK, Chinfa, Mean Well, Texas Instruments and Rohm. There’s a huge variety of package sizes and power ratings, starting at 0.25 W.


But Hi-Link modules have an advantage of their own: a pretty good balance of power, price and quality, which is why they’re also used quite often.
I ordered the 12 V module because I use that voltage more often than 3.3 or 5 V. I’d like to order several different models, though, just to keep them on hand.
They’re relatively small, though models both smaller and larger are available.


You can find the exact dimensions in the drawing for this series of power supplies.


The basic specifications are printed right on the case. I tried to find the full specs for the 12 V converters, but for some reason only the 5 V version’s specs are listed everywhere, so I haven’t copied them here.
There are four solder pins on the bottom. I was a little puzzled that the input pins are noticeably closer together than the output pins, when it would make more sense to do the opposite. The case is sealed, with solid potting compound visible on the bottom.


I won’t beat around the bush. There isn’t much to describe, so let’s get straight to the tests.
I used the following equipment for testing:
1. Electronic load
2. Oscilloscope
3. Multimeter
4. Thermal camera.

I put an HF filter in front of the oscilloscope probe, consisting of a 1 µF electrolytic capacitor and a 0.1 µF ceramic capacitor.


The power supply showed very good load regulation and output voltage stability.
The voltage only started to drop when the output current reached twice its rated value. At 650 mA, it fell below my preset limit of 9 V.


Ripple was also fairly low, measuring about 30 mV peak-to-peak up to a load current of 300 mA.


The ripple stayed around 50 mV up to nearly twice the rated current, then started rising sharply at a load current of 500 mA.


The voltage stays stable, as you can see from the graph.


I also ran a load test at up to 1200 mA. The power supply survived that too, with the output voltage dropping to 3.77 V, although I expected it to shut down. It also has short-circuit protection, by the way.


And, of course, I did a short thermal test. Along with checking the temperature, I measured how the output voltage changed as the unit heated up.
These power supplies have a slight negative temperature coefficient: as they warm up, the output voltage drops a little.
The photos below show:
1. Voltage at 250 mA at the start of the test.
2. Voltage after 20 minutes.
3. After 20 minutes, I increased the load current to 400 mA and ran it for another 20 minutes. The photo shows the voltage after 20 + 20 minutes.
4. After 40 minutes of testing—20 minutes at 250 mA plus 20 minutes at 400 mA—I removed the load. The output voltage rose, but remained below the initial 12.031 V measured with the power supply cold.


The power supply performed very well even at a load current of 400 mA, and the case only warmed up to 55 °C. I think this extra headroom is mainly useful when operating with a low input voltage. With our 220–230 V mains, the load current can be increased beyond the rated 250 mA.


I found a very detailed review of the 5 V version of this power supply online. Its efficiency is slightly lower because of the lower output voltage and higher current (600 mA). The review also includes thermal images taken at load currents of 600 mA and 1000 mA.


It also shows the 5 V version being taken apart. I decided not to break mine open, since I only have one and still plan to put it to use :)


The internals are pretty good. For obvious reasons, there’s no input EMI filter—it simply wouldn’t fit—but otherwise everything looks fine. I was pleased to see the generous clearance between the primary and secondary sides, the safety slot beneath the optocoupler, and the overall build quality.


The input has a 4.7 µF capacitor, which is perfectly adequate for the rated 3 W. There’s also an inductor on the output to reduce voltage ripple—just like on the “grown-up” power supplies, only smaller.


And here I can’t help quoting the famous line: “The little boy went to his father” :)
Don’t let the terminal blocks on the larger power supply fool you: both belong to the series of power supplies designed for mounting on a circuit board. The photo just shows the version with terminals; there’s also a version with solder pins.
Pictured is the IRM-60-24ST, rated at 20 times the power of the little unit under review.


To sum up, I liked this power supply. If you need something like this, I’d definitely recommend getting one.

That’s all from me. I hope you found the review useful. As usual, I’m looking forward to your questions in the comments—and perhaps someone can share a link to a better deal.