I have made a bench power supply from an old PSU and added a USB port connected directly to the 5V rail (leaving the data pins disconnected).
When I connected a TP4056 charging board (like this), the TP4056 smoked and blew up.
I am trying to understand if the board was defective (or I messed up with the wiring) or if the USB must not provide more than 1A (the 5V rail of the PSU provides something like 25A).
As far as I know it does not matter how many amps the USB can provide since the connected device always draws what it needs, but I like a confirmation from someone more expert than me 🙂
Cheers
Best Answer
USB ports are supposed to limit current somehow. This can be totally disconnecting power for a while when overcurrent is detected (like a resettable fuse), or current limit. However, no device should rely on this.
Being able to providing more than the maximum normal current should be OK, as long as the device is working properly. Most likely, your output wasn't supplying 5 V. Check it with a voltmeter.
Of course you should have done that before plugging in something that could get smoked by the higher voltage.