Cheap Power Supply

[LunarMist]

I have a device that uses one of the ubiquitous Chinese wall warts. Unfortunately it becomes quite hot in use in the US, so you can imagine I'm a bit concerned how it will perform in the desert with no A/C and at 240V.

Are such cheap supplies more likely to fail at 240V than 120V? On the one hand at the higher mains voltage the input filtering cap may die more easily and on the other wouldn't the output take more stress at 120V? It's been decades since I was building power supplies, but I always used components rated well over needed voltages or currents, made sure inductors were nowhere near saturation, etc. How sophisticated are the circuits used in the cheap power supplies?

 

[CougTek]

How sophisticated are the circuits used in the cheap power supplies?

The cheaper they are, the simpler they generally are too. The cheaper ones almost always use low-quality components, especially capacitors, that barely do the job.

I don't think cheap power supplies are more likely to fail at 240V than at 120V. I think they are more likely to fail, period. They are more likely to bring other components with them too when they'll fail.

 

[jtr1962]

Most power supplies tend to be slightly more efficient at 240V than 120V, and hence generate less heat. That said, Cougtek is right-these supplies often use marginal components and/or have poor quality of assembly. I've taken apart some cheap supplies which failed and more often than not it's the electrolytic capacitors. If you use cheap ones with high ESR that tends to mean more heat and eventual failure from electrolyte drying out. Better supplies use ceramic and solid polymer caps.

 

[LunarMist]

Most power supplies tend to be slightly more efficient at 240V than 120V, and hence generate less heat. That said, Cougtek is right-these supplies often use marginal components and/or have poor quality of assembly. I've taken apart some cheap supplies which failed and more often than not it's the electrolytic capacitors. If you use cheap ones with high ESR that tends to mean more heat and eventual failure from electrolyte drying out. Better supplies use ceramic and solid polymer caps.

Yeah. I've been the victim of exploding caps on multiple occasions. Once on the head and once the ceilings.
There are not many fine PS options other than bulky or heavy stuff or do it yourself. Is there an online source for decent wall warts that you use?

 

[ddrueding]

There are not many fine PS options other than bulky or heavy stuff or do it yourself. Is there an online source for decent wall warts that you use?

I would love to have an answer to this as well. In situations where reliability is critical and some component has a wall wart, I've been known to put in mid-range scientific power supplies.

 

[LunarMist]

The usage is travel so weight is an issue.