| 摘要 |
PURPOSE:To prevent heating due to the abnormality of a fly-back transformer by connecting a protecting huse to the low voltage coil of the above-mentioned transformer and melting this huse based on the size relation of the primary side current and secondary side current of the above-mentioned transformer. CONSTITUTION:A protecting huse 25 is connected to a low voltage side coil 12 of a fly-back transformer 8 and a primary side current detecting circuit 19 and a secondary side current detecting circuit 23 are provided to detect the currents in the primary side and secondary side of the above-mentioned transformer. When the detecting value of the above-mentioned primary side current detecting circuit 19 goes to be larger than the detecting value of the above-mentioned secondary side current detecting circuit 23, a detecting value comparator 26 outputs an operating signal to a gate circuit 24. The protecting huse 25 is melted when the gate circuit 24 is turned on and interrupts voltage impression to the fly-back transformer 8. Thus, the fly-back transformer 8 is prevented from being abnormally heated by a rare-short. |
