| 摘要 |
PURPOSE:To perform detection with high accuracy and at high speed before changing of output voltage by sensing a voltage induced on a secondary side during an ON period to detect an undervoltage on a primary side. CONSTITUTION:A switching power source is constituted by the connection of a series circuit of a smoothing capacitor 3, a primary winding of transformer 5 and a switch circuit 4 between positive and negative side terminals 12 of a DC power. A secondary side winding of this transformer 5 is furnished with three taps, of which output is inputted to a stabilization circuit 10 via diodes 6, 7 and capacitors 8, 9. In this case, a voltage-detecting circuit 11 for sensing an undervoltage is provided to compare an output S 11 from a tap 5e of the transformer 5 via diode 12, capacitor 13 and resistance 14 with a reference voltage by a converter 16. As a result, if the output S11 is under the reference voltage Vref, it is outputted to a terminal 17 as an undervoltage detection signal SL.
|
