Patent ID: 7154762

Claim:
A power source apparatus comprising: a conversion circuit ( 40 , 60 , 34 , 32 , 91 , 100 , 80 ) which performs conversion of an input voltage into an output voltage different from the input voltage; and a driving power source ( 33 ) which is charged with the input voltage to drive said conversion Circuit ( 40 , 60 , 34 , 32 , 91 , 100 , 80 ), wherein: said conversion circuit ( 40 , 60 , 34 , 32 , 91 , 100 , 80 ) includes a transformer ( 32 a , 32 b ) which has a primary winding and a secondary winding which are inductively coupled to each other, a switching circuit ( 40 , 60 , 34 , 80 ) which applies the input voltage to said primary winding intermittently, a rectifier circuit ( 91 ) which rectifies a voltage which is induced in said secondary winding, a detection circuit ( 100 ) which detects that a standby signal is supplied, and supplies a detection signal representing a detection result to said switching circuit ( 40 , 60 , 34 , 80 ) via a predetermined signal line; and a feedback circuit ( 104 , 105 ) which generates a feedback signal comprising a current that increases as the output voltage increases, and which supplies the generated feedback signal to said switching circuit ( 40 , 60 , 34 , 80 ) via said signal fine; said switching circuit ( 40 , 60 , 34 , 80 ) determines whether or not said detection circuit ( 100 ) supplies the detection signal representing that the standby signal is detected; in a case where determining that the standby signal is not detected, said switching circuit ( 40 , 60 , 34 , 80 ) starts applying the input voltage intermittently when a voltage of said driving power source ( 33 ) rises to a first turn-on voltage, stops applying the input voltage when the voltage of said driving power source ( 33 ) lowers to a predetermined turn-off voltage, and sets timings of intermittence of the input voltage based on the feedback signal so that the output voltage may be stabilized at a predetermined first value; and in a case where determining that the standby signal is detected, said switching circuit ( 40 , 60 , 34 , 80 ) stabilizes the output voltage at equal to or lower than a predetermined second value which is lower than the first value, by starting applying the input voltage intermittently when the voltage of said driving power source ( 33 ) rises to a second turn-on voltage which is lower than the first turn-on voltage and higher than the turn-off voltage, and by stopping applying the input voltage when the voltage of said driving power source ( 33 ) lowers to the turn-off voltage.