| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply which is capable of switching a power supply voltage to a secondary-side control IC in accordance with a level of an input voltage and for which it is not necessary to be produced separately for each destination while protecting the secondary-side control IC.SOLUTION: The switching power supply includes: a transformer 10 which is provided at the side of a secondary coil 12 and includes an auxiliary coil 14 including a tap 14c with the same winding direction as a primary coil 11; a control circuit which is connected to a high voltage side end 14a and the tap 14c of the coil 14 and is driven by receiving supply of the power supply voltage from the coil 14; a voltage monitor circuit 30 for monitoring a voltage between both ends 14a and 14b of the coil 14; and a switch circuit 40 which is provided between the high voltage side end 14a and the control circuit and switches conduction and disconnection between the high voltage side end 14a and the control circuit. The switch circuit 40 is connected with the voltage monitor circuit 30 and disconnects the high voltage side end 14a and the control circuit in the case where the circuit 30 detects a voltage equal to or higher than a predetermined voltage.SELECTED DRAWING: Figure 1 |
