Redesigning cell phone chargers

[thornza]

Hi,

Just wanted to know from any electrical engineers out there why it would be hard to redesign the common cellphone chargers to not draw current when the device is plugged out of it.

My EE knowledge is not great, but wouldn't it be possible to put a "switch" before the primary coil that was only completed when the cell phone gets plugged in. Maybe run another wire pair from the gap in the circuit before the primary coil down to the connection that gets plugged into the cell phone - when the connection gets plugged in the circuit can be completed.

I know that would involve running high voltage AC down to that wire to the device, but would that be such a big deal?

cheers,

thornza

 

[Floid]

It would not be that hard to redesign a cellphone charger to include a switch when the device wasn't plugged in, but there are many reasons why it is not done:

1.) A cell phone charger doesn't draw much current when it isn't charging a cell phone. So the benefits of adding this feature are negligible.

2.) It increases the cost of the cell phone charger.

3.) It increases the mean time between failure of the cell phone charger (makes them less reliable).

4.) Increases the size of the charger (have to install a high voltage switch/extra wiring).

5.) The switching will draw current, so while you have decreased current draw when no cell phone is plugged in you have increased current draw when the cell phone is plugged in.


"I know that would involve running high voltage AC down to that wire to the device, but would that be such a big deal?"

It would as soon as someone touched the connector and got shocked or dropped the dangling connector in some water.