| 摘要 |
PURPOSE:To prevent the failure of an element even though a deflecting electrode comes of a short-circuit state, by a method wherein two sets of the circuits respectively having the current control action capable of turning on and off are connected in series and the deflecting electrode is connected to that connecting point via a resistance. CONSTITUTION:The circuit part consisting of a bias power source A11, a switch element A12, a base resistance A13, an emitter resistance A14, and a transistor A15, and a high voltage d.c. power supply 2 operate when a deflecting electrode is charged. If the switch element is turned off, bias current flows through the base of the transistor A15, current flows from the high voltage d.c. power supply 2, and the deflecting electrode 1 and a floating electrostatic capacitor 56 start to be charged. When the current increases and the voltage drop due to the emitter resistance A14 approaches a base bias voltage, the base current decreases and the charging is continued in a fixed current state. The circuit part consisting of a bias power source B21, a switch element B22, a base resistance B23, an emitter resistance B24, and a transistor B25 is used when the charge stored in the deflecting 1 and the floating electrostatic capacitor 56 is discharged. Thereby, the discharge time can be shortened. |
