A power supply apparatus and method are provided. A conversion component outputs a first current having a predetermined phase region, an output component outputs a load voltage, a sense component senses a second current value, and a switch element allows current to flow in a first state and impedes current in a second state. The switch element changes between states based on a drive signal forcing the switch into the second state when the first current is in the predetermined phase region and the second current value exceeds a threshold indicating an overcurrent condition. A region determination circuit determines whether the first current is in the predetermined phase region and produces a phase region signal. An overcurrent detection circuit senses the second current value, determines whether it exceeds an overcurrent condition threshold, and produces an overcurrent signal. A protection circuit causes the drive circuit to switch the drive signal.