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I was working on a project recently that required a 24V power supply. I found some really cheap ones on eBay selling for a few dollars shipped from China. This made me wonder - are they any good?
I wanted to answer the question myself, so I did a comparison and teardown between a brand-name $85 retail made-in-Japan Cosel power supply vs. the cheap $8 Chinese one. Some of my friends also expressed interest in knowing what was inside these common power supplies, so I made a video:
To summarize - yes there is a big difference between the internal and external construction. However, most surprisingly was that the output ripple seems to be better for the Chinese power supply! However, there are loads of other things I didn't / cannot test, such as transient response, overload protection, safety, long-term reliability, precision, isolation, etc... and keep in mind that this is only at a single test point, and its performance will change with varying loads, so I am aware of the limitations of my test but I hope it serves as a quick example.
So while the chinese supply does indeed work, I would still very much prefer to use a brand-name power supply.
See higher resolution photos here:
Finally, I recently did a teardown of an adjustable bench SMPS over here as well: which I think makes for an educational comparison, such as the differences in SMPS topology.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Based on the equipment for repair that we do at work, I say it's almost impossible to predict which one will last longer and perform better, without stress testing.
On average it's overheating that kills most smpsu so a 'quality' 24V 10A supply may not be as reliable as a cheap 24V 15 or 20A smpsu used at 10A.
I've seen no end of dc/dc converters and smpsu failed because a designer used them at rated capacity.
Some people asked me if I could review a mid-priced unit instead. So I bought a $18 Delta power supply (yes the company that makes computer fans!), as a step up from the eBay supply, but not as expensive as the Cosel. Delta is in fact one of the largest SMPS manufacturer on the planet!
Check it out here:
After playing with it a bit more extensively, I think I'll be using more Delta supplies in the future. I haven't had a failure with any of my eBay power supplies yet, but I think I'll swap them out for Delta units for more reliability :)
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Are cheap Ebay switch-mode Power Supply Units any good?
However, there are loads of other things I didn't / cannot test, such as transient response, overload protection, safety, long-term reliability, precision, isolation, etc... and keep in mind that this is only at a single test point, and its performance will change with varying loads, so I am aware of the limitations of my test but I hope it serves as a quick example.
