Is it possible to power the usb hub from molex?

Question

Electronics

Good afternoon.

There is a usb hub 2.0 with external power supply 5v.2a in a separate round connector, but its native power supply has stopped working.

Question. Is it possible to power it from a computer by taking 5v from a molex?

In theory, external power is replaced by power from the computer's power supply, and this is even a plus, when the computer is turned off, the hub will also turn off.

Answer 1

Of course it is possible

Answer 2

If from the point of view of purely power supply, then it is possible. But it is not recommended, and the reason is the unwanted reverse power supply of +5 volts through the USB cable from the hub to the computer port. If the USB port is powered normally, through the motherboard, then its current passes through a self-resetting fuse (with a trip current of about 1 A), and in some motherboards it also passes through a device for monitoring this current. But if power from a common PSU is supplied to the port from the outside, then the above devices are shorted through the PSU and stop working. The USB port will still work, but without short circuit protection and without current tracking.
Of course, since no current is consumed from the port with such a power supply, then it (the port) does not care. And nevertheless, it must be borne in mind that this mode is abnormal, and may lead to incomprehensible glitches.