Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-05-25
2001-01-30
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S133000
Reexamination Certificate
active
06181580
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to power supplies and, more particularly, to single-power-supply circuitry for providing gridding and biasing functions suitable, for example, for electron tube applications, such as x-ray tubes or electron beam guns.
In one application, gridding circuits are employed for controlling x-ray tubes in pulsed fluoroscopy in order to reduce radiation exposure to patients resulting from decaying x-ray tube current. In particular, x-ray tube gridding involves rapid application and removal of a high-voltage (in the range of a few kilovolts) to a cathode cup, the cup functioning as a grid in conventional electron tubes. Upon grid voltage turn-off, the x-ray beam is turned on, and vice versa. The length of the on and off periods are typically measured in tens of milliseconds. High-voltage isolation is required for such applications, as the gridding circuit is referenced to a cathode potential of up to −70 kV in standard tubes and up to −140 kV in grounded anode tube designs.
In addition to grid control, an x-ray tube also requires bias control, i.e, for controlling the focal spot size of the x-ray beam. Hence, a grid-controlled x-ray tube typically has two control electrodes for providing the gridding and biasing voltages. Typically, two separate power supplies are used to provide the two voltages.
Accordingly, it is desirable to provide a single power supply circuit capable of providing both the gridding and biasing functions. To be practicable, it is further desirable that such circuitry be relatively simple, small in size, and reliable.
BRIEF SUMMARY OF THE INVENTION
A single power supply circuit, comprising a push-pull input converter stage and a voltage-controlled latch (VCL) circuit output stage isolated from each other by a transformer, provides both voltage gridding and biasing functions in, for example, an x-ray tube application. In the gridding mode, a first voltage level supplies the push-pull converter to provide an output voltage that is sufficiently high to trigger the VCL circuit and thereby provide grid control via a grid control electrode. In the biasing mode, a lower voltage level supplies the push-pull converter such that the output voltage is insufficient to trigger the VCL circuit. As a result, a voltage divider provides a predetermined biasing voltage on a bias control electrode. The two voltage levels may be provided by using a switch for switching in the voltage levels as desired, or by using two primary windings on the isolation transformer.
REFERENCES:
patent: 4366395 (1982-12-01), Gillard et al.
patent: 4593371 (1986-06-01), Grajewski
patent: 4661896 (1987-04-01), Kobayashi et al.
patent: 4680693 (1987-07-01), Carron
patent: 4783795 (1988-11-01), Yahata
patent: 4805080 (1989-02-01), Nieminen
patent: 5107412 (1992-04-01), Fuchs
patent: 5969955 (1999-10-01), Laskai et al.
patent: 6021051 (2000-02-01), Laskai et al.
patent: 100874 (1976-11-01), None
patent: 2 709 396 (1993-08-01), None
patent: 2 718 599 (1994-04-01), None
“Generators and Tubes in Interventional Radiology,” E. Ammann; G. Wiede, Syllabus: A Categorical Course in Physics, 8thScientific Assembly and Annual Meeting of the Radiological Society of North America, Nov. 26-Dec. 1, 1995, pp. 59-74.
Ilic Milan Zarko
Laskai Laszlo
Breedlove Jill M.
General Electric Company
Stoner Douglas E.
Vu Bao Q.
Wong Peter S.
LandOfFree
Single-supply gridding and biasing circuitry does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Single-supply gridding and biasing circuitry, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Single-supply gridding and biasing circuitry will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2516003