[Arthur McGowan]

There is no such thing as “stored voltage.” That’s just the reporter talking. Like most laymen, the “volt” is the only electrical unit he knows the name of.

[Revel]

“There is no such thing as “stored voltage.””

Not sure what you mean. Voltage is the difference in potential that can cause current flow. Batteries and Capacitors store it. Also called a “Charge”.

I would say that this device would have to be a simple switching power supply storing a charge to a capacitor and then releasing it back through the 5V source.

[cynwoody]

There is no such thing as “stored voltage.” That’s just the reporter talking. Like most laymen, the “volt” is the only electrical unit he knows the name of.

Probably an inverter converting the DC USB supply to AC, feeding into a voltage multiplier charging a capacitor to 240v, at which time a thyristor is opened to discharge the capacitor back into the USB port, after which the cycle repeats. The frequency would depend on how much current can be drawn from the port and how big the capacitor is.

See here.