| 摘要 |
PURPOSE:To prevent a pulse transformer from heating and being a very high temperature by preventing a driving circuit from continuing to turn on for a certain constant time or above even when a control circuit is troubled and the condition that a signal to cause a pulse current to flow at the pulse transformer is outputted is continued. CONSTITUTION:When a high level continues to be outputted as an output (a) of a control circuit 1, a current i1 to flow at a capacitor 16 comes to be a differentiated waveform port. When the current i1 approaches to 0, a transistor 5 is turned off. At this time, a current to flow at the collector of the transistor 5, first, flows by 71.4mA only due to the function as the transformer of a pulse transformer 9, soon, the pulse transformer generates a magnetic saturation, the function as the transformer is eliminated, and a current limited only by the direct current resistance of a secondary coil starts to flow at 500 mA. Since the current i1 to flow at the capacitor 16 approaches 0, and then the transistor 5 is turned off, the collector current of the transistor 5 is also returned to 0. Thus, the heating of the pulse transformer caused by the trouble of the control circuit can be prevented.
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