EP0146875A2 — X-ray generator with voltage feedback control

Claim 1

Independent Claim 170 words

1 . A power generator for use in applying a high voltage between the anode and cathode of an X-ray tube comprising: (a) a power inverter for connection to a d.c. power source, said inverter being capable of producing an alternating current, square-wave output from the d.c. power source; (b) a high-voltage transformer connected to said inverter for receiving said alternating current output for and delivering a high-voltage output ; (c) a high-voltage rectifier connected to receive said high-voltage output and to deliver a high-voltage d.c. output to the X-ray tube; (d) control means for operating said inverter in response to control signals to selectively vary the pulse width of said inverter square-wave output; and (e) a voltage feedback circuit connected between the X-ray tube and said control system, said circuit being responsive to the voltage level between the anode and the cathode of the X-ray tube for generating feedback control signals to be applied to the control means for maintaining a predetermined voltage level across the anode and cathode.

Claim 2

Dependent Claim 170 words

1 . A power generator for use in applying a high voltage between the anode and cathode of an X-ray tube comprising: (a) a power inverter for connection to a d.c. power source, said inverter being capable of producing an alternating current, square-wave output from the d.c. power source; (b) a high-voltage transformer connected to said inverter for receiving said alternating current output for and delivering a high-voltage output ; (c) a high-voltage rectifier connected to receive said high-voltage output and to deliver a high-voltage d.c. output to the X-ray tube; (d) control means for operating said inverter in response to control signals to selectively vary the pulse width of said inverter square-wave output; and (e) a voltage feedback circuit connected between the X-ray tube and said control system, said circuit being responsive to the voltage level between the anode and the cathode of the X-ray tube for generating feedback control signals to be applied to the control means for maintaining a predetermined voltage level across the anode and cathode.

Claim 3

Dependent Claim 31 words

A power generator as set forth in Claim 1 wherein said control means is responsive to selectively vary the frequency of the inverter output as well as the pulse width thereof.

Claim 4

Dependent Claim 47 words

A power generator as set forth in Claim 1 wherein said control means includes means for generating a voltage error signal, which is a function of a difference between the feedback control signal and a voltage demand level which is generated in response to an operator control.

Claim 5

Dependent Claim 46 words

A power generator as set forth in Claim 3 wherein said voltage error signal generating means includes a phase advance feature which causes the voltage error signal to vary during a predetermined rise time to thereby protect against overshoot at the end of the rise time.

Claim 6

Dependent Claim 32 words

A power generator as set forth in Claim 4 wherein said voltage error signal generating means further includes a phase-lag means to compensate for the noise introduced by said phase advance feature.

Claim 7

Dependent Claim 38 words

A power generator as set forth in Claim 1 wherein said control means includes a sawtooth generator with an output whose frequency and slope are variable in response to predetermined control signals to thereby modulate said control means.

Claim 8

Dependent Claim 49 words

A power generator as set forth in Claim 6 and including an anti-saturation circuit which is responsive to the current flow in said high-voltage transformer to sense a saturation condition in said power inverter and to responsively provide a signal to said sawtooth generator to diminish the saturation condition.

Claim 9

Dependent Claim 22 words

A power generator as set forth in Claim 1 wherein said power inverter comprises a power-transistor bridge controlling a high-voltage, high-frequency transformer.

Claim 10

Dependent Claim 26 words

A power generator as set forth in Claim 1 wherein said d.c. power source comprises a three-phase a.c. source with a three-phase non-controlled rectifier connected thereto.

Claim 11

Dependent Claim 27 words

A power generator as set forth in Claim 1 wherein said power inverter operates at a relatively high frequency in the range between 1 - 15 kilohertz.

Claim 12

Dependent Claim 139 words

A high-voltage generator for the application and control of a high voltage across the anode and cathode of an X-ray tube comprising: (a) a d.c. source; (b) an inverter for changing the output of the d.c. source to an a.c. voltage to feed a high-tension transformer; (c) means for rectifying the output of said high tension transformer for application to the X-ray tube; (d) means for sensing the voltage level across the anode and cathode of the X-ray tube and for generating signals representative of the actual voltage; (e) means for generating signals representative of a desired voltage across the anode and cathode; and (f) control means for operating in response to said actual voltage-representative signals and said desired voltage-representative signals to selectively switch said inverter on and off in such a manner as to maintain said desired voltage.

Claim 13

Dependent Claim 139 words

A high-voltage generator for the application and control of a high voltage across the anode and cathode of an X-ray tube comprising: (a) a d.c. source; (b) an inverter for changing the output of the d.c. source to an a.c. voltage to feed a high-tension transformer; (c) means for rectifying the output of said high tension transformer for application to the X-ray tube; (d) means for sensing the voltage level across the anode and cathode of the X-ray tube and for generating signals representative of the actual voltage; (e) means for generating signals representative of a desired voltage across the anode and cathode; and (f) control means for operating in response to said actual voltage-representative signals and said desired voltage-representative signals to selectively switch said inverter on and off in such a manner as to maintain said desired voltage.

Claim 14

Dependent Claim 43 words

A high-voltage generator as set forth in Claim 11 wherein said sensing means includes a bleeder circuit with a dual-purpose capacitor serving as both the high-voltage capacitor in the bleeder circuit and as the filter capacitor at the output of the rectifying means.

Claim 15

Dependent Claim 46 words

A high-voltage generator as set forth in Claim 11 wherein said control means includes a microprocessor which receives said actual voltage-representative signals through a d-a converter and provides a voltage-demand signal by way of an a/d converter to then be compared with said actual voltage-representative signals.

Claim 16

Dependent Claim 20 words

A high-voltage generator as set forth in Claim 11 wherein said inverter is a square-wave inverter, operating in pulse-width-modulation fashion.

Claim 17

Dependent Claim 23 words

A high-voltage generator as set forth in Claim 14 wherein said inverter is comprised of a power-transistor bridge controlling a high-voltage, high-frequency transformer.

X-ray generator with voltage feedback control

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