Patent ID: 8218338

Claim:
A universal input switching power supply comprising: the rectifier having multiple inputs adapted to couple to an external AC power and an output, wherein the rectifier converts the external AC power and output the first DC power to the output thereof; a signal detecting unit connected to the output of the rectifier to detect a voltage of the first DC power and output a detecting signal; a PFC circuit having multiple outputs and inputs connected to the output of the rectifier and the signal detecting unit to obtain the first DC power and receive the detecting signal, wherein the PFC circuit converts the first DC power to a second DC power with different voltage according to the detecting signal; and a parallel and serial type DC to DC converter having a transformer having a primary and secondary coils, input terminals and output terminals, wherein the input terminals thereof are connected to the outputs of the PFC circuit and the signal detecting units to obtain the second DC power and receives the detecting signal, wherein the parallel and serial type DC to DC converter the second Dc power to a third DC power and physically changes a turn ratio of the primary and secondary coils of a transformer thereof according to a voltage ratio of the second DC power and the third DC power, wherein the turn ratio is in direct ratio to the voltage ratio.