| 摘要 |
PURPOSE:To protect a high voltage transformer by conducting a semi-conductor switching element upon increase of primary current and blowing a fuse off thereby stopping current supply to a high voltage coil. CONSTITUTION:Upon increase of primary current IB, voltage drop across a current detection resistor R1 increases. When the voltage drop exceeds over a predetermined level, a semi-conductor switching element SCR is conducted. The semi-conductor element SCR is connected between the neutral point of the primary coil N1 and the source side EB of the fuse F1, and forming a closed circuit. Upon conduction of the semi-conductor switch SCR, pulses occurring at the neutral point of the primary coil N1 are shortcircuited to cause a large current. The fuse F1 is blown off by the large current and current supply to a high voltage transformer 10 is interrupted. By such arrangement, heating or firing of the high voltage transformer 10 can be prevented reliably. |
