| 摘要 |
PROBLEM TO BE SOLVED: To prevent rupture of a grid ON circuit even if an X-ray tube discharges during irradiation of an X-ray. SOLUTION: When an inverter circuit 3 is turned on by a timing circuit 4, high voltage generated from a high voltage rectifying circuit 16 is applied to an X-ray tube 9, and since a diode 10 sets grid voltage of the X-ray tube 9 to zero volt by becoming a forward bias, an electric current flows between an anode and a cathode of the X-ray tube 9, so that an X-ray is exposed. Simultaneously when turning on the inverter circuit 3, a grid ON circuit is turned on by the timing circuit 4, and a grid and the cathode of the X-ray tube 9 are held in zero volt to stabilize the grid voltage. When the X-ray tube 9 discharges during the irradiation of the X-ray, since the grid and the cathode are raised by a discharge current from a smoothing capacitor 718, a discharge protective curcuit 16 operates to short-circuit the grid and the cathode. Thus, high voltage is not applied on the grid ON circuit to prevent rupture of this circuit.
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