| 摘要 |
PURPOSE:To obtain a protecting circuit even though a horizontal oscillating circuit and other circuits are not charged, by providing a secondary winding to a coil for stable working at a low ringing level, and using the output of said secondary winding as a detecting signal. CONSTITUTION:The flyback pulse emerges at the secondary winding of a coil L1 for stable working at a low ringing level in a normal active mode. This output voltage, however, does not make a Zener diode D6 conduct, therefore, an overvoltage protecting circuit 4 is not operated. If an abnormal current flows to a flyback transformer T1, the both-end voltage of the coil L1 rises up. Thus the pulse voltage emerging at the secondary winding of the L1 also rises up. When the voltage obtained by rectifying the pulse voltage exceeds the working voltage of the diode D6, the circuit 4 works to stop the output of a horizontal primary driving circuit 5. This prevents the destruction of insulation of the transformer T1. In such a way, a protecting circuit can be constituted even though a horizontal oscillating circuit 3, the circuits 4 and 5, etc. are not charged. |
