Interesting teardown here of a very cheap AC -to -USB charger:
“… The UL has complex safety specifications on how much distance (known as ”creepage” and “clearance”) there must be between the primary and secondary sides to prevent a shock hazard.[6] The rules are complicated and I’m no expert, but I think at least 3 or 4 mm is required. On this power supply, the average distance is about 1 millimeter. The clearance distance below R8 on the right is somewhat less than one millimeter (notice that white line crosses the PCB trace to the left of R8).
…. this sub-millimeter gap is all that’s protecting you and your phone from potentially-lethal 340 volts. I also took the transformer apart and found only single layers of insulating tape between the windings, rather than the double layers required by the UL. After looking inside this charger, my recommendation is to spend a bit more on a charger, and get one that has UL approval and a name-brand manufacturer……”
My recommendation is to read HKJ’s reviews, and act accordingly. :bigsmile: He includes 5000 volts tests (amongst others) when he reviews these products.
Yes, these things are terrible.
I had one that consisted of a 5W cement resistor as current limiter, followed by a free running oscillator. No regulation whatsoever.
Isolation distance is often catastrophic small with these things, and the parts are not necessarily rated for mains voltage . . .
Some things you better don’t buy to cheap.
In the EU we have the Low Voltage Directive (2006/95/EC) making it illegal to sell electrical goods that don’t have CE conformity. However, now with Ebay and Amazon and other portals it is possible for end-users to buy potentially dangerous equipment directly from China.
In my opinion it’s overrated, come visit Africa and you will see electrical installations that would make you hair stand up on end, I believe India is similar.
Yet no one bothers or cares its the African way, the average shack where people live , they steal the electricity from the overhead street lighting to avoid paying, then the multi plug and extension leads that go into housing with no fuses or circuit breakers!
I come from an electrical background and most power supplies sold in Africa come direct from china with no safety rating, and sold in superstores as a daily stock item.
The standard 2 pin EU power pack is common here and they modify it in many ways to fit, or use a multi adaptor to convert to our 3 prong system , this often ends up with multi multi adaptors before the power supply is connected.
Safety agh what’s that , non existent!
