| 摘要 |
PURPOSE:To stabilize the potential of a shield or grid of an electric charger for a copying machine or the like by detecting the voltage between the shield or grid and gland by resistance division, subjecting the detected voltage to current amplification, further amplifying the same with a high-voltage transistor and connecting a varister and the high-voltage TR in parallel. CONSTITUTION:The voltage divided by resistors R1-R3 is inserted between the shield 2a or grid 2b and the gland G is connected via a current amplifying transistor TR1 to the high-voltage transistor TR2. The emitter of the TR2 is maintained at a constant voltage by a constant voltage diode ZD. The voltage V1 of the shield 2a or grid 2b is V1=(VZ+2VBE).(R1+R2+R3)/R3 if the voltage of the diode ZD is designated as VZ and the sum of the base-emitter voltages of the TR1, TR2 is designated as 2VBE. Said voltage, therefore, has the constant potential. The varister 7 is for breakdown protection of the TR2. |
