| 摘要 |
PURPOSE:To obtain a sufficient tube voltage variable range in photographing and fluoroscopy, and to prevent heat generation and noise in fluoroscopy by connecting in series a resistance value variable auxiliary resistance circuit and a capacity value variable capacitor in the middle of current supply to the primary winding of a transformer. CONSTITUTION:By appropriately setting values of an auxiliary resistance 8 and a capacitor 7 for resonance inserted into a resonance circuit, and by performing the phase control of the third switch 11 and the periodic variation of thyristors 17, 18, X-ray tube voltage control in photographing and fluoroscopy modes is made possible. In case of short time exposure in photographing, switches 8, 10 are selectively switched so that the resistance value of auxiliary resistance group 8 in the resistance circuit is increased with tube current is decreased, and the capacity value of resonance capacitor group 7 is decreased. In addition, ignition timing of thyristors 17, 18 is shortly set to increase X-ray tube voltage. On the other hand, in case of long time exposure in fluoroscopy, the switches are selected so that resistance value of auxiliary resistance group 8 is more increased and the capacity value of the resonance capacitor group 7 is more decreased.
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