Naively buying a 12V power supply from an ebay supplier, rated at 15 Amp, I note that the voltage drops to 10 v under load. Obviously junk, but I wonder if the voltage adjust pot's range could be extended to adjust this out?
I later found a source of TDK Lambda supplies which have wide voltage adjustability and good specs.
I think the most likely reason that the voltage falls under load is that they skimped on the inductor. Given that the supply is junk, it's reasonable to assume they also skimped on the switch, so by trying to increase duty cycle beyond whatever the original maximum was by messaging with the adjust pot I think there's a risk of damaging the switch.
I see the paraphrenalia of a buck supply - including a big inductor on a cylinder core. It's not even close to specs. The TDK by contrast is the real deal - 20A at 12 V adjustable 9-16, 20A at 48-60 V. There is a lot of crap on ebay... OTOH, if you are technically proficient, you can write intelligent specs and do very well. Most of these sellers don't know first thing about what they are selling.
Sounds like it was a rhetorical question. The same problem happens outside of auction sites too, I've just encountered equally hopeless claims about a flow switch. If someone followed their advice to use it for mains shower p ump switching they could land in prison.
The hell if it does...usually that happens with multi-output supplies where the loading must be balanced (as a % of FL) on all the outputs. Obviously the feedback is not taken from the single output you're using.
If it was the Pyle Audio rating scale, it would produce over 1000W of power from a 9V battery.
I've used the AC -> DC Meanwell power supplies that can be found on the shelf at some electronics hobby and prototyping stores. They've been better than rated and they handle abuse gracefully. They're power factor corrected so they're bulky as hell, though.
I haven't bought any pre-made DC-DC inverters. Modern chips are so amazing that I just buy a strip of them to keep ready for projects. Some TI Simple Switcher chips have a built-in inductor. The TPS6211x is efficient from < 0.0001 to 1.5 amps and needs only an LC filter and a feedback divider. They've all performed at least as well as rated, with the exception of some exploding from regeneration over-voltage because they didn't shut down like their the specs claimed they would.
I don't know what you paid for it, but I have found ebay vendors are
*very* concerned about their rating. I expect you can return it and if the shipping is close to what you paid for the unit they may not want you to return it. I had a couple of USB serial port dongles that were not as advertised and when I talked to the vendor they ended up telling me to keep them rather than have to pay for the shipping. I've had this happen several times. Once I just wrote to ask about a driver and rather than answer the question they refunded the three bucks.
Some products on ebay are ok. The trick is knowing which is which.