Energy saving USB receptacle

1. A universal serial bus (USB) charging system comprising:

a) a charging circuit comprising a power source comprising an enable/disable pin; and

b) a USB receptacle comprising USB terminals and a first shell side that is physically and/or electrically separated from a second shell side, wherein one of the shell sides is connected to a ground and the other shell side is electrically connected to an on/off logic circuit comprising a pull-up resistor, an inverter, or a transistor, and wherein the on/off logic circuit is electrically connected to the charging circuit comprising the power source and enable/disable pin;

wherein the charging circuit provides approximately 0 V to the USB terminals and/or consumes less than approximately 9 mW from the power supply when the USB receptacle is unmated with a USB plug; and wherein the charging circuit provides approximately 5 V DC to the USB terminals and/or consumes more than approximately 0.25 W from the power supply when a USB plug is mated with the USB receptacle and electrically connects the first shell side and the second shell side.

2. The USB charging system of claim 1 wherein the power supply is a source of direct current.

3. The USB charging system of claim 1 wherein the power supply is a battery.

4. The USB charging system of claim 1 wherein the power supply is a source of alternating current.

5. A method for charging a universal serial bus (USB) device, the method comprising:

a) providing a USB device comprising a USB plug;

b) providing a universal serial bus (USB) charging system comprising:

i) a USB receptacle comprising USB terminals and a first shell side physically and/or electrically separated from a second shell side;

ii) a charging circuit; and

iii) a power supply;

wherein the charging circuit provides approximately 0 V to the USB terminals and/or consumes less than approximately 9 mW from the power supply when the USB receptacle is unmated with a USB plug; and

c) mating said USB plug to said USB receptacle; wherein when the USB plug is mated to said USB receptacle, the charging circuit provides approximately 5 V DC to the USB terminals.

6. The method of claim 5 further comprising removing said USB plug from said USB receptacle after said USB device is partially or fully charged by the USB charging system.

7. The method of claim 5 wherein removing said USB plug from said USB receptacle reduces the power consumed by the charging circuit to less than approximately 9 mW and/or wherein removing said USB plug from said USB receptacle reduces the voltage at the USB receptacle to approximately 0 V.