This thing is a power supply that works from USB. It is under 12 dollar on aliexpress, I bought it here: link. If a proper USB-C source is used (that can deliver up to 12V) it can deliver 15W of power, and 2A. From a normal 5V USB supply it can deliver much less power (it stopped at 1A when powering a SST20 led), but it can boost voltage up to 30V if needed. This is enough for many little hobby-tasks like checking leds or even powering a driver to see if it works. It has a very nice display that gives you good control over what is going on.
I had one before, the red one in the picture, but that one had physical adjustments pots that did not provide direct feedback, they were very unhandy and I never had them working well.
The new black one in contrast allows entering the settings digitally, and it monitors everything well, in practice that is a big leap forward in usuability, even though the power supply hardware at the core may not be very different from the red version.
I hoped that this power supply would work with very low currents, but although you can set it and read it out as low as 1mA and it does function that low, under 10mA the supply is not very stable, if a led is connected you can see random flickering every now and then.
I checked the displayed current reading on the device at various set currents with a multimeter in the circuit, with a led as load, the multimeter agreed with the display within 2% or so that is fine.
I kept the thing at 2A powering a SST20 led for a few minutes without problem. The input power was 12.5W, output power was 6.9W, so the power dissipation of the thing was 5.6W.
I could check more things, and there is many things I can not check (I’m not HKJ, just someone with a solder iron who knows Ohm’s law and not much else), but what I noticed so far is making it useful for what I want from it: small tasks in my flashlight hobby 
