Grounded AC to DC converter for charging multiple 5V devices via USB

[mjsummers]

I have a small dilemma regarding the standard AC-DC converter circuit that I am adapting for a custom 5V charging station. The circuit will be using a 5V conditioner plus a full-wave rectifier and a USB Host controller. If I want to use a fuse (~15A) to protect the circuit, should the fuse be installed before the transformer?

 

[andre_luis]

If I want to use a fuse (~15A) to protect the circuit, should the fuse be installed before the transformer?

From a safety perspective, as more devices are covered by the protection fuse, the better, so at the circuit entry should be suitable. Imagine for example an EE transformer that has accidentally been dropped and lost part of the winding varnish insulation. If this wire touch the metallic chassis of the equipment box, it may short-circuit it with the phase of the electric network, but would not fire any fuse at the transformer secundary windings.

 

[mjsummers]

thanks for the info, was debating on whether or not to have the circuit ground tie back into the ground on the cable from the wall.

 

[andre_luis]

Are you considering to tie the 5v ground reference with the mains earth ? If yes, I still do not see this as a good decision, particularly if the USB will be used with HID, what mean that will not have a proper safety protection for end user against several disturbances on the mains.

 

[mjsummers]

The USB interface is meant for charging Bluetooth devices, along with other handheld products (Mobile Phones, Tablets, and/or PS3 Wireless controllers), no upstream connection