The power supply apparatus includes a switching element connected to a primary winding of a transformer to which an input voltage is applied; a feedback unit configured to output a first feedback voltage according to an output voltage, the output voltage induced in a secondary winding of the transformer and output to a load; a current detection unit for detecting a current flowing to the switching element and output a second feedback voltage according to the current detected; a limiting unit for limiting the first feedback voltage so that the current flowing to the switching element is below a predetermined current value; an output unit for outputting a driving signal for the switching element based on the first feedback voltage limited by the limiting unit and on the second feedback voltage; and a control unit for controlling the switching element according to the driving signal output from the output unit.