[Manufacture of high frequency direct current dental X-ray machine]

This paper introduces five dental X-ray machines which are manufactured with IGBT to realize high frequency, real-time sampling and PWM to ensure the closed-loop control for tube current and Anodes's high voltage. These five machines also use microcomputer and combined X-ray tube for precise control. The sets don't have high voltage outside. The error of tube voltage is less than 1% and exposure time is less than 3%. The photos of pulp cavity and surrounding tissue can be seen clearly. These sets surely meet the requirements of perspective use in clinical.