| 摘要 |
PURPOSE:To prevent a switching transistor (TR) from being damaged by detecting voltage applied to both the ends of a load and controlling the ON/OFF operation of the TR. CONSTITUTION:An ionization vacuum gage 10 in an emission control device is constituted of a filament 11, a glid 12 and a collector 13 and an ion current measuring circuit 14 and a glid constant voltage circuit 15 are connected to the vacuum gage 10. Power is supplied from a power source 21 to the filament 11 through a switching driving circuit 22. Emission current is detected by a resistor R4. In addition, a Schmitt circuit consisting of an operational amplifier 23 and a reference voltage power supply 24, a photocoupler 25, etc., are arranged in the device. Since the voltage applied to both the terminals of the load is reduced as compared to a normal voltage when the load is shorted, the abnormality of the load is detected and power supply to the load is automatically stopped. |
