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Off The Shelf and Non-Compliant Power Supplies (from Amazon)

A customer had purchased some power supplies from Amazon UK to get started with the development on their product. And why not? There are lots of cheap products available and everyone has a budget to meet. The chances are that they’ll get damaged, lost or broken anyway.

They were happy with the (perceived) quality of the PSU so approached the manufacturer directly for bulk pricing for volume production. However, the Amazon sample made it’s way to Unit 3 Compliance for EMC pre-compliance testing where the fun began…

infographic comparing two power supplies

Externally, the only way to tell the difference between the compliant and non-compliant versions is a slight difference in the length of the barrel connector and a slightly different shape of strain relief grommet.

These devices are being marketed as the same device on the outside and yet are completely different on the inside!

I’ve not been able to subsequently find this exact power supply on Amazon but there are similar looking variants still available.

 

A Real Problem

Crucially, it’s not just EMC that is being sacrificed. This “race to the bottom” of extracting every last penny from products has more serious consequences.

More dangerously for consumers, electrical safety is also being compromised as shown in this study from Electrical Safety First on Apple chargers.

At a previous employer, an inspection was performed on 50 power supplies (again, bought from Amazon) that one of the project teams had purchased for powering various development platforms within the company. This revealed some serious safety problems (creepage and clearance) resulting in the entire batch being quarantined and scrapped for recycling.

Another aspect to consider – if the manufacturer has two different, almost indistinguishable products then how does your supply chain guarantee that you will receive the correct one? What is to stop the manufacturer from swapping out the more expensive compliant power supply halfway through production?

The principle of caveat emptor still applies. Disingenuous product markings are being used to falsely indicate compliance.

 

What To Do?

The obvious way round this is only to buy small quantity power supplies from trusted suppliers. I know from working with other customers that suppliers like RS and Farnell / Element 14 take compliance seriously. Buying from these sources is more expensive financially but what price do you put on your own safety?

If you are relying on buying a pre-approved power supply always ask for the EMC and safety test reports and the Declaration of Conformity. A supplier who cannot readily supply these readily should be disregarded.

Compare the details in the reports with the physical sample in front of you. Especially for safety reports, photos of the unit are generally included, inside and out. Look for any differences between the two.

Differences in EMC performance are not obvious. The only way to be sure of the quoted performance is to perform some quick tests, conducted and radiated emissions being the two main ones.

 

How We Can Help.

Here at Unit 3 Compliance we can give you some peace of mind that your power supply isn’t going to cause you any issues. Some of the things we do include:

  • Provide full EMC testing for all off the shelf products
  • Electrical safety analysis and testing
  • Help you understand the compromises and
  • We can review test reports and compare to physical samples with an experienced eye
  • Every incoming customer power supply is given a HiPot test as standard to help catch any problems

Please get in touch to reduce your stress levels.