Protective circuit for X-ray generator
First Claim
1. A high voltage system for an X-ray tube having an anode and a cathode comprising:
- (a) a DC power source;
(b) a high voltage transformer having a primary winding and first and second secondary windings, said first secondary winding being connected to provide a positive voltage to the anode and said second secondary winding being connected to provide a negative voltage to the cathode, each voltage being referenced to a common ground potential;
(c) a full bridge transistor inverter connected for providing switched current to said primary winding from said DC source, said inverter having at least four transistors forming two current paths through said primary windings;
(d) control means for providing pulse-width modulated (PWM) gating signals to at least one of said transistors in each of said current paths;
(e) means for providing a signal representative of a desired voltage between the anode and cathode of the X-ray tube;
(f) means for providing first and second feedback signals representative, respectively, of the voltage at the anode and the cathode of the X-ray tube;
(g) means for combining said first and second feedback signals to obtain a summed signal representative of the anode to cathode voltage;
(h) means for comparing said summed signal to said desired voltage signal for generating an error signal for application to said control means such that said control means is effective to vary said PWM signals in a manner to minimize said error signal; and
(i) means for comparing said error signal to a predetermined reference value and for inhibiting said PWM signals when said error signal exceeds said reference value.
1 Assignment
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Accused Products
Abstract
An inverter receives a d.c. voltage and delivers to an X-ray tube, by way of a high-voltage transformer, filter, and rectifier, a high-voltage d.c. output. The inverter is driven in response to control signals which are responsive to the difference between a voltage demand signal and a voltage feedback signal. The control signals are also responsive to various status conditions of the system which are monitored by a microprocessor. Inputs to the microprocessor include various signals which are indicative of voltage or current conditions. In this way, such conditions as an over-voltage at the output, an unbalance between the anode and cathode with respect to ground, or an excessive current flow are detected and precautionary measures are quickly taken to prevent further damage to the system.
51 Citations
11 Claims
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1. A high voltage system for an X-ray tube having an anode and a cathode comprising:
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(a) a DC power source; (b) a high voltage transformer having a primary winding and first and second secondary windings, said first secondary winding being connected to provide a positive voltage to the anode and said second secondary winding being connected to provide a negative voltage to the cathode, each voltage being referenced to a common ground potential; (c) a full bridge transistor inverter connected for providing switched current to said primary winding from said DC source, said inverter having at least four transistors forming two current paths through said primary windings; (d) control means for providing pulse-width modulated (PWM) gating signals to at least one of said transistors in each of said current paths; (e) means for providing a signal representative of a desired voltage between the anode and cathode of the X-ray tube; (f) means for providing first and second feedback signals representative, respectively, of the voltage at the anode and the cathode of the X-ray tube; (g) means for combining said first and second feedback signals to obtain a summed signal representative of the anode to cathode voltage; (h) means for comparing said summed signal to said desired voltage signal for generating an error signal for application to said control means such that said control means is effective to vary said PWM signals in a manner to minimize said error signal; and (i) means for comparing said error signal to a predetermined reference value and for inhibiting said PWM signals when said error signal exceeds said reference value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification