Patent ID: 7339805

Claim:
A power supply for receiving an alternating current (AC) input voltage having any magnitude within a wide range of AC input voltage magnitudes and producing therefrom a direct current (DC) output voltage, said power supply comprising: a rectifier that receives and rectifies an AC input voltage having a magnitude within said wide range; a transformer comprising a first winding and a second winding, wherein the first winding is connected to receive the rectified AC input voltage so that current flows through the first winding, and wherein a voltage across the second winding defines the output of the power supply; a switching member connected to the first winding for permitting and preventing the flow of current through the first winding in response to a control signal; a controller connected to the switching member that generates the control signal in response to a signal representative of the output of the power supply; and a voltage blocking clamp comprising at least one transistor connected between the rectifier and the transformer and switching member that limits the amount of the rectified AC input voltage applied to the transformer and switching member to a predetermined amount when the rectified input voltage exceeds that predetermined amount, wherein when the rectified input voltage exceeds the predetermined amount, the amount of the rectified input voltage above the predetermined amount is applied to the at least one transistor instead of the transformer and switching member.