Patent ID: 7882371
Filing Date: 2011-02-01
Classification: G03G

Abstract:
1. A power supply unit comprising: a first power supply of a constant-voltage output to supply a power to a load by using a power supplied from an external source as an input source; a capacitor for charging a power; a second power supply of a constant-current output to supply a power to the load based on a control signal by using the power from the capacitor as an input source; and a signal generating unit including a current detector disposed at a position between the load and an output from the first power supply and an output from the second power supply, and a converting unit that converts a load current detected by the current detector flowing in the load into a current signal, wherein the signal generating unit generates the control signal which controls the second power supply to supply the power to the load to compensate for a shortfall of the load current indicated by the generated current signal when the load current exceeds an upper limit of an output current of the first power supply, wherein the first power supply includes a voltage detector which detects a voltage at a position between the current detector and the load which is fed back into a constant-voltage controller of the first power supply which controls an output voltage therefrom and to maintain, at a set value, a voltage of a power supply line that is provided at a position between the load and the current detector.