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Does a high quality SMPS 'power brick' (Wall wart) exist?
Posted by
6SN7WGTB
on 07 Feb, 2022 19:02
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Having had a number of SMPS problems recently, tracked down to the usual component failures, is it actually possible to buy decent quality SMPS units that won't either blow up, wear out and/or pollute the street with RF?
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#1 Reply
Posted by
thm_w
on 07 Feb, 2022 23:20
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If you can get ahold of name brand laptop adapters, usually those will be good (Asus, sony, apple, dell, etc.), from thrift store or electronics recycler.
I have some quality 12V 4A units (WEIHAI), but doubt its worth shipping to UK just for that.
If you buy generic no-name from amazon you are almost guaranteed to get garbage.
What specific voltage and power are we talking about?
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#2 Reply
Posted by
Whales
on 08 Feb, 2022 00:48
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+1 to piggybacking the computer market. Genuine laptop chargers and off-the-shelf ATX power suppliers from good brands all tend to be very good.
I've opened up some off-brand laptop chargers and cheap ATX power supplies before, it's typical to see all of the input filtering (X caps & common mode chokes) missing. Recently I discovered some 12V wall power supplies I bought from a local supplier emitted so much conducted noise that my raspi zeros (after a 12->5V buck) would "work" but couldn't initialise their wifi chipsets. My scope showed something like intermittent 1Vp-p pulses coming from the wall wart
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#3 Reply
Posted by
Cerebus
on 08 Feb, 2022 05:51
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Meanwell produce inexpensive reliable supplies. They have quite an extensive range of wall warts and external power brick style supplies. I've not used any, but I've had good experiences with their OEM type enclosed and open frame supplies. Beware that there are quite a lot of Meanwell imitators/counterfeiters out there. As one of the few Chinese companies to have earned themselves a decent reputation they get ripped off a lot, so only buy through trusted channels.
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#4 Reply
Posted by
John B
on 08 Feb, 2022 06:20
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I purchase meanwell stuff from element14 (especially when they have voucher specials). They have the best prices that I can find. Other resellers aimed at "prosumer" markets tend to have quite a markup.
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#5 Reply
Posted by
6SN7WGTB
on 08 Feb, 2022 07:47
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I hate to rain on the parade, but this was a Mean Well product. Made in Taiwan.
And from RS Components too. Which is PRECISELY why I bought them - an OK make, an OK supplier and NOT made in china.
Having had it open I wouldn't say it was designed particularly well - the 450V cap was laid flat on the PCB: covering the opto-isolator and right across the Mains/ELV separation space, and so spewed its contents from the vent directly onto ELV components. Resistors and diodes right underneath the cap too. Very cool ventilated spot.
The actual circuit looks reasonable and with decent fuse/surge/XY and CM choke on the input. It's an IEC input socket so could have even used the earth for some Y class rejection, but hasn't.
EDIT: the SMPS was specified at 12V DC 1.5A. The actual consumer device was max 500mA. Plugged in 24x7, but zero quiescent draw and cycle time about 1 minute per week on.
In any event, as soon as chinese components go in, you take your chances on whether the make faked the specs that particular day.
Good idea re seeking out (good) laptop ones - I have on occasion bought Apple USB adapters to use for 5V supplies where you can get away without any 'handshaking' problems.
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#6 Reply
Posted by
6SN7WGTB
on 08 Feb, 2022 10:12
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Just plugged in the brand new and unused one.
It's already up to 53degC outer plastic case with no load, and this appears to be coming from the switching transistor.
I note also that the PCB has tracks to allow Y class caps to be added back to a vacant hole where the earth pin of the IEC could be wired.
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#7 Reply
Posted by
all_repair
on 08 Feb, 2022 10:47
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Get the SMPS rated for medical use if you want best afforable quality.
Most of the problems are created by dropshippers selling factory rejects and grade E bricks online. Their value-added is their English language abilities, and for most profits they sourced for the cheapest.
I have been running a cheap no-name Chinese 12V open frame SMPS 247 for many years. It is powering my NAS and network gears.
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#8 Reply
Posted by
6SN7WGTB
on 08 Feb, 2022 10:49
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You beat me to it - just looking through the 'medical' grade ones right this minute.
I doubt that they are any better, but there's a very tiny possibility if any are truthfully tested/labelled.
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#9 Reply
Posted by
Karel
on 08 Feb, 2022 10:50
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#10 Reply
Posted by
6SN7WGTB
on 08 Feb, 2022 11:59
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I would more than happily pay more for something that (a) might work for more than 6 months and (b) won't potentially kill me and/or my family!
However, I suspect most of the members here feel similarly, but we're the minority globally.
Consumer organisations should force legislation to display CoO on every item we buy. That would start to focus the mind on the source of the world's problems.
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#11 Reply
Posted by
ve7xen
on 08 Feb, 2022 19:09
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Consumer organisations should force legislation to display CoO on every item we buy. That would start to focus the mind on the source of the world's problems.
I would agree, but more because shipping things back and forth around the world isn't environmentally sustainable, so I would like to see more distributed production.
CoO says essentially nothing about quality. Consumers demand low prices, and suppliers everywhere will engineer products to satisfy them. I will agree it is hard to identify quality products these days, as neither price nor CoO is much of an indicator, as witnessed by your Taiwan-made product that is apparently junk, but simply labelling CoO isn't a good proxy. Practically everything is assembled in China, from the dangerously low cost products to the most lauded-for-quality brands, it has nothing to do with nationality and everything to do with 'sort by price'.
Laptop PSUs are generally higher than 12V. For quality 12V supplies, look for monitor, network equipment or thin client power supplies from OEM vendors like Dell, HP, Juniper, and Cisco. Often manufactured by Delta or LiteOn.
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Having had a number of SMPS problems recently, tracked down to the usual component failures, is it actually possible to buy decent quality SMPS units that won't either blow up, wear out and/or pollute the street with RF?
Stuff from mainstream distributors is usually Ok - in the UK : CPC, Rapid, Farnell,RS or Stontronics for volume orders.
Also run them well below their specified power for best lifetime
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Plug packs from IKEA are one of the best options to get good consumer level power adapters. Much better and more consistent than regular hardware/electronics store. See detailed test/teardown here
lygte-info, Ikea Koppla USB 5V 2A
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#14 Reply
Posted by
wraper
on 08 Feb, 2022 20:38
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Having had it open I wouldn't say it was designed particularly well - the 450V cap was laid flat on the PCB: covering the opto-isolator and right across the Mains/ELV separation space, and so spewed its contents from the vent directly onto ELV components. Resistors and diodes right underneath the cap too. Very cool ventilated spot.
Those primary caps almost never vent, especially with spewing electrolyte. Unless overvolted, which very likely was the case.
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#15 Reply
Posted by
thm_w
on 08 Feb, 2022 23:31
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Just plugged in the brand new and unused one.
It's already up to 53degC outer plastic case with no load, and this appears to be coming from the switching transistor.
I note also that the PCB has tracks to allow Y class caps to be added back to a vacant hole where the earth pin of the IEC could be wired.
This makes no sense, the good units I have draw <0.1W in standby, so do not heat up at all, which is a requirement from most countries energy standards.
What is the part number?
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#16 Reply
Posted by
John B
on 09 Feb, 2022 00:41
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Something sounds amiss. I have a whole bunch of the Meanwell GST series adapters in various voltages and currents and have had no failures, also they run cool under load, so they must be far more efficient than the no-name brand cheap adapters they replaced.
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#17 Reply
Posted by
6SN7WGTB
on 09 Feb, 2022 07:34
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Here you go.
Quick and dirty standby check shows 2W/5VA. Current is 28mA at 238V.
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#18 Reply
Posted by
6SN7WGTB
on 09 Feb, 2022 07:41
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(a) The top was bulged, and there appeared to be a small crack along one of the vent lines when examined closely. Not 'exploded' but vented' so my word 'spewed' was perhaps ill advised.
(b) There was some staining in line with the cap top on two LV components
(c) There's residue everywhere, concentrated in the vicinity of the cap top direction.
Just reporting what I am finding. We all know it "shouldn't" but it "has".
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#19 Reply
Posted by
SteveyG
on 09 Feb, 2022 08:47
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XP Power is pretty much the highest quality from all the testing I've had to do at work. They're also mainly UK based which is nice. Stontronics, Friwo and MeanWell would be 2nd in line from my experience.
MeanWell have very differing product lines however, so whilst they make some brilliant and reliable medical power supplies, they also make some really cheap ones that will fail.
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#20 Reply
Posted by
6SN7WGTB
on 09 Feb, 2022 09:46
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Opened up the unused spare.
Admittedly with the heatsink (a very small thin strip of steel) removed in order to open it, the transistor on the input side runs very hot with no load.
Let it cool off for 5 mins then putting 1A on as load, rapidly heated up again so no different aside the output device starts to heat up as well (as you'd expect).
The cap in the unused one tests fine for value, ESR and leakage, albeit only tested to 160V DC.
The cap in the dud is completely open circuit.
I did have a Doh! moment - there are two small plastic plugs in the base which can be extracted with something sharp to reveal two fixing screws... No need for the hacksaw.
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#21 Reply
Posted by
thm_w
on 09 Feb, 2022 22:55
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I’m using a Mean Well GST18A12-P1J in very close proximity to a weak signal RF system where maintaining a low noise environment is important. I can’t (easily) prove how well the Mean Well is enhancing or inhibiting performance of the overall system but the system seems to be working on par.
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#23 Reply
Posted by
wraper
on 10 Feb, 2022 09:19
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Mean Well makes PSU of a very different quality for different price ranges. Cheapest stuff comes with cheap components and not very good specs. More expensive has all Japanese caps, and high efficiency.
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#24 Reply
Posted by
6SN7WGTB
on 10 Feb, 2022 09:20
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Mean Well makes PSU of a very different quality for different price ranges. Cheapest stuff comes with cheap components and not very good specs. More expensive has all Japanese caps, and high efficiency.
Do you know which ones?