Patent ID: 7525259

Claim:
A power supply system comprising: an input terminal operable to receive an input voltage; a transformer coupled to the input terminal and defining a primary side and a secondary side; an output terminal coupled to the secondary side of the transformer and connectable to a load for providing current thereto; and means for regulating the power supply system from the primary side so that the current provided to the load at the output terminal is substantially constant, wherein the means for regulating comprises: a control circuit having a power switch through which drain current flows; and the feedback circuit coupled to the control circuit; wherein the control circuit and the feedback circuit are operable to regulate a voltage at the output terminal in a steady-state operation of the power supply system and further operable to provide a constant current output to the load when a voltage at the output terminal is lower than a certain value; wherein the transformer comprises a first and second primary side winding and a secondary side winding, wherein the power switch of the control circuit is coupled to the first primary side winding, and wherein the output terminal is coupled to the secondary side winding.