SWITCHING POWER SUPPLY DEVICE AND DISPLAY APPARATUS WITH THE SAME

PROBLEM TO BE SOLVED: To save energy in a switching power supply device, and suppress the manufacture cost of a display apparatus with the same. SOLUTION: In the switching power supply device 2, the voltage application to the primary winding T11 of a transformer T1 is switched by a switching element Q1, and an output circuit 4 outputs a flyback voltage induced hereby in a secondary winding T12 to a monitor 3. A control circuit 5 measures a differential voltage between its output voltage and a rated output voltage, and controls the switching operation. When a power switch SW1 sets the voltage output to the monitor 3 to OFF, a forced input circuit 6 inputs a forward voltage into the control circuit 5 for misreading the voltage as the differential voltage. Hereby, the duty ratio of the switching operation is made small, and an energy loss in the transformer T1 is reduced. Moreover, the output voltage of the output circuit 4 is made roughly zero, accordingly the monitor 3 need not be provided with a switch for break of current application linked with the power switch SW1. COPYRIGHT: (C)2011,JPO&INPIT