Patent ID: 8559203

Claim:
A power source apparatus, comprising: a first alternating current line; a second alternating current line; an electric power inputting portion including a rectifying circuit for rectifying an alternating current voltage supplied from an alternating current power source, said electric power inputting portion serving to output the rectified voltage to each of said first and second alternating current lines; a first converter including a switching element for converting the alternating current voltage into a first direct current voltage; a second converter for converting the first direct current voltage obtained in said first converter into a second direct current voltage; and a control circuit for carrying out control for driving at least said switching element of said first converter so as to be turned ON or OFF, said first converter including an output node, a choke coil having a first choke coil winding part and a second choke coil winding part operably associated with the first choke coil winding part, said first choke coil winding part disposed in said first alternating current line, one end of said first choke coil winding part being connected to an output terminal of said rectifying circuit, the second choke coil winding part connected at one end thereof to said second alternating current line and an opposing end thereof to said control circuit, a diode connected between an opposing end of said first choke coil winding part and said output node so that a forward direction is obtained from the other end side of said choke coil toward said output node, said switching element connected between said first alternating current line on the other end side of said choke coil, and said second alternating current line, and an output capacitor connected between said output node and said second alternating current line, wherein said control circuit controls an ON-time for said switching element in accordance with at least an output voltage from said first converter, and an activation state of said second converter, wherein when detecting that no current is caused to flow through said choke coil, said control circuit turns ON said switching element, and determines the ON-time for said switching element in accordance with the output voltage from said first converter and wherein said control circuit includes: a voltage inputting portion configured to receive the output voltage from said first converter; an ON-time controlling portion configured to determine the ON-time for said switching element in accordance with a level of an output signal from said voltage inputting portion; a monitoring circuit for monitoring the level of the output signal from said voltage inputting portion in a plurality of stages; and a clamp controlling circuit for clamping the output signal from said voltage inputting portion in accordance with a monitoring result obtained in said monitoring circuit.