Patent ID: 7719139

Claim:
A power-supply unit comprising: a main power-supply circuit and a secondary power-supply circuit, both connected to an alternating current power supply; an input current control circuit provided in the main power-supply circuit; a circuit current detection element provided in the input current control circuit; a first rectifying circuit connected between the alternating current power supply and the input current control circuit, the first rectifying circuit provided in the main power-supply circuit; a second rectifying circuit connected to the alternating current power supply, the second rectifying circuit provided in the secondary power-supply circuit; and a smoothing circuit connected to an output of the second rectifying circuit, the smoothing circuit provided in the secondary power-supply circuit; wherein a current of a summation of an input current supplied to the main power-supply circuit and an input current supplied to the secondary power-supply circuit flows in the circuit current detection element; and the input current control circuit controls the input current supplied to the main power-supply circuit such that harmonic current is suppressed in the current flowing in the circuit current detection element.