USB Charger

Author	Message
Mixtel90 Guru Joined: 05/10/2019 Location: United Kingdom Posts: 8964	Posted: 09:20pm 08 Oct 2023       Your guess is as good as mine. If it's a decent make then it's probably ok. If it's a super-cheap Chinese thing then I'd be very wary. The circuit is a switching converter. The possible danger arises in the distance between the tracks on the PCB and in the quality of the HF isolating transformer used. Some are fine, others are next to lethal. Try plugging it in and measuring the voltage between the USB shell and mains earth. Try it with and without a shell=earth load of about 1K. If you get any voltage in the latter case then there's almost certainly too much leakage to consider it safe. You can get away with a tiny bit of leakage for a charger but not if you are going to keep putting your fingers on it. You could try linking negative output to mains earth but that might stress the transformer.