Patent ID: 7330024

Claim:
A power supply device for supplying source current to an electronic device comprising: a current output unit for outputting output current including at least said source current as a component of the current thereof; a connection resistor which electrically connects said current output unit and said electronic device for supplying said source current from said current output unit to said electronic device; a low-pass filter having a cut-off frequency lower than the frequency at which said source current applied to said electronic device changes, for allowing the output voltage of said current output unit to pass through while suppressing components frequencies higher than said cut-off frequency; a differential detection unit for detecting the electric potential difference between the output voltage of said low-pass filter and the electric potential at the device-side terminal of said connection resistor, which is closer to said electronic device; and a parallel load unit which is connected to the output terminal of said current output unit in parallel with said connection resistor, and which has a function of consuming a partial current which is a part of said output current of said current output unit in a case that said electric potential difference detected by said differential detection unit is smaller than a predetermined value, and which has a function of stopping reception of said partial current from said current output unit in a case that said electric potential difference detected by said differential detection unit has become greater than a predetermined value, wherein said parallel load unit includes a switch for performing opening/closing actions according to the output of said differential detection unit, and wherein said power supply device further includes a time measurement unit for measuring on-time, for which said switch is in the on-state, or off-time, for which said switch is in the off-state, in a measurement period for the average consumed current of said electronic device.