Protective circuit for limiting the input power applied to an x-ray tube and method of operation

Claim 2

An X-ray tube protective system for preventing the substantially instantaneous input power applied to an X-ray tube from exceeding a predetermined level and comprising: first continuously variable circuit means for applying a voltage signal of a preselected value to an X-ray tube; second continuously variable circuit means for applying a current signal of a preselected value to the X-ray tube; voltage monitoring circuit means for developing a first signal having a value representative of the value of the applied voltage signal; current monitoring circuit means for developing a second signal having a value representative of the value of the applied current signal; multiplying circuit means coupled to said voltage monitoring circuit means and said current monitoring circuit means for developing an output signal having a value representative of the value of the power represented by the mathematical product of said first and second signals; compensating circuit means coupled to said multiplying circuit means for developing a control signal indicating when said output signal exceeds a predetermined value indicating the predetermined power level; and, actuatable circuit means coupled to said compensating circuit means for, in response to said control signal, limiting the value of one of the current and voltage signals applied to the X-ray tube to a level sufficiently low to prevent input power in excess of said predetermined power level from being applied to said X-ray tube, while still permitting adjustment of the level of said limited signal within a range less than said sufficiently low level.

Claim 3

An apparatus as defined in claim 1 wherein said multiplying circuit means includes impedance means having input circuit means for varying the impedance of said impedance means in accordance with the value of a signal applied to said input circuit means and output circuit means for developing an output signal having a value which varies in accordance with variations in the impedance of said impedance means; said current monitoring circuit means coupled to said input circuit means of said impedance means so that said impedance varies in accordance with the value of said second signal; and said output circuit means of said impedance means being coupled to said compensating circuit means.

Claim 4

An apparatus as defined in claim 1 wherein said voltage monitoring circuit means is coupled to said output circuit means of said impedance means so that a signal developed by said output circuit means varies in accordance with variations in the impedance of said impedance means and with variations in the value of said first signal.

Claim 7

A method as defined in claim 4 including the step of decreasing the value of the current signal applied to the X-ray tube when the value of the output signal exceeds a predetermined level to thereby prevent excessive output from being applied to the X-ray tube.

Claim 8

An X-ray tube protective system for preventing the substantially instantaneous input power applied to an X-ray tube froM exceeding a predetermined level and comprising: first variable circuit means for applying a voltage signal of a preselected value to a said X-ray tube; second variable circuit means for applying a current signal of a preselected value to a said X-ray tube; voltage monitoring circuit means for developing a first signal having a value representative of the value of the applied voltage signal; current monitoring circuit means for developing a second signal having a value representative of the value of the applied current signal; multiplying circuit means coupled to said voltage monitoring circuit means and said current monitoring circuit means for developing an output signal having a value representative of the value of the mathematical product of said first and second signals; compensating circuit means coupled to said multiplying circuit means for developing a control signal indicating when the power represented by said mathematical product and by the value of said output signal exceeds a predetermined value; and, actuatable circuit means coupled to said compensating circuit means for, in response to said control signal, limiting the maximum attainable value of one of said current and voltage signals to be applied to a said X-ray tube to a level less than or equal to that level necessary to attain said predetermined power level, while simultaneously permitting variation of one of said current and voltage signals for operation of the tube at power levels less than that represented by said predetermined value of said output signal.

Claim 9

An X-ray tube protective system for preventing the substantially instantaneous input power applied to an X-ray tube froM exceeding a predetermined level and comprising: first variable circuit means for applying a voltage signal of a preselected value to a said X-ray tube; second variable circuit means for applying a current signal of a preselected value to a said X-ray tube; voltage monitoring circuit means for developing a first signal having a value representative of the value of the applied voltage signal; current monitoring circuit means for developing a second signal having a value representative of the value of the applied current signal; multiplying circuit means coupled to said voltage monitoring circuit means and said current monitoring circuit means for developing an output signal having a value representative of the value of the mathematical product of said first and second signals; compensating circuit means coupled to said multiplying circuit means for developing a control signal indicating when the power represented by said mathematical product and by the value of said output signal exceeds a predetermined value; and, actuatable circuit means coupled to said compensating circuit means for, in response to said control signal, limiting the maximum attainable value of one of said current and voltage signals to be applied to a said X-ray tube to a level less than or equal to that level necessary to attain said predetermined power level, while simultaneously permitting variation of one of said current and voltage signals for operation of the tube at power levels less than that represented by said predetermined value of said output signal.

Claim 10

An apparatus as defined in claim 6 wherein said multiplying circuit means includes impedance means having input circuit means for varying the impedance of said impedance means in accordance with the value of a signal applied to said input circuit means and output circuit means for developing an output signal having a value which varies in accordance with variations in the impedance of said impedance means; said current monitoring circuit means coupled to said input circuit means of said impedance means so that said impedance varies in accordance with the value of said second signal; and said output circuit means of said impedance means being coupled to said compensating circuit means.

Claim 11

An apparatus as defined in claim 7 wherein said voltage monitoring circuit means is coupled to said output circuit means of said impedance means so that a signal developed by said output circuit means varies in accordance with variations in the impedance of said impedance means and with variations in the value of said first signal.

Claim 12

An X-ray tube protective system for preventing the input power applied to an X-ray tube from exceeding a predetermined maximum level and comprising: first variable circuit means for applying a continuously variable voltage signal to a said X-ray tube; second variable circuit means for applying a continuously variable current signal to a said X-ray tube; voltage monitoring circuit means for developing a first signal having a value representative of the value of the applied voltage signal; current monitoring circuit means for developing a second signal having a value representative of the value of the applied current signal; multiplying circuit means coupled to said voltage monitoring circuit means and said current monitoring circuit means for developing an output signal having a value representative of the value of the instantaneous power represented by the mathematical product of said current and voltage signals; compensating circuit means coupled to said multiplying circuit means for developing a control signal indicating when the power represented by said output signal exceeds a predetermined value; and, actuatable circuit means coupled to said compensating circuit means for, in response to said control signal, limiting the maximum attainable value of said current signal to be applied to a said X-ray tube to a level less than or equal to that Level necessary to attain said predetermined maximum power level, while simultaneously permitting variation of said current signal below said maximum attainable value for operation of the tube at power levels less than predetermined maximum level.

Claim 13

An X-ray tube protective system for preventing the input power applied to an X-ray tube from exceeding a predetermined maximum level and comprising: first variable circuit means for applying a continuously variable voltage signal to a said X-ray tube; second variable circuit means for applying a continuously variable current signal to a said X-ray tube; voltage monitoring circuit means for developing a first signal having a value representative of the value of the applied voltage signal; current monitoring circuit means for developing a second signal having a value representative of the value of the applied current signal; multiplying circuit means coupled to said voltage monitoring circuit means and said current monitoring circuit means for developing an output signal having a value representative of the value of the instantaneous power represented by the mathematical product of said current and voltage signals; compensating circuit means coupled to said multiplying circuit means for developing a control signal indicating when the power represented by said output signal exceeds a predetermined value; and, actuatable circuit means coupled to said compensating circuit means for, in response to said control signal, limiting the maximum attainable value of said current signal to be applied to a said X-ray tube to a level less than or equal to that Level necessary to attain said predetermined maximum power level, while simultaneously permitting variation of said current signal below said maximum attainable value for operation of the tube at power levels less than predetermined maximum level.

Claim 14

An apparatus as defined in claim 9 wherein said multiplying circuit means includes impedance means having input circuit means for varying the impedance of said impedance means in accordance with the value of a signal applied to said input circuit means and output circuit means for developing an output signal having a value which varies in accordance with variations in the impedance of said impedance means; said current monitoring circuit means coupled to said input circuit means of said impedance means so that said impedance varies in accordance with the value of said second signal; and said output circuit means of said impedance means being coupled to said compensating circuit means.