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EP-4742837-A1 - ELECTRONIC CIRCUIT AND METHOD FOR PROVIDING A HIGH TUBE VOLTAGE FOR AN X-RAY TUBE, METHOD FOR OPERATING AN X-RAY TUBE, X-RAY TUBE SYSTEM AND MEDICAL IMAGING DEVICE

EP4742837A1EP 4742837 A1EP4742837 A1EP 4742837A1EP-4742837-A1

Abstract

The invention relates to an electronic circuit (1) for providing a high voltage (17) for an X-ray tube (18). The electronic circuit (1) comprises a first inverter unit (4) configured to obtain an input DC voltage (2) and convert it into a first AC voltage (8) depending on a first control variable (10), and a second inverter unit (5) configured to convert the input DC voltage (2) into a second AC voltage (9) depending on a second control variable (11). A further circuit section (3) is configured to generate the high voltage (17) for the tube depending on the first and the second AC voltages (8, 9). A control arrangement (24) is set up to determine a controlled variable (25) and to change the first manipulated variable (10) and/or the second manipulated variable (11) depending on the controlled variable (25), and to determine the controlled variable (25) depending on a first alternating current (6) and a second alternating current (7) and/or a first direct current (43) and a second direct current (44).

Inventors

  • OTT, LEOPOLD
  • WAFFLER, STEFAN

Assignees

  • Siemens Healthineers AG

Dates

Publication Date
20260513
Application Date
20241106

Claims (15)

  1. Electronic circuit (1) for providing a tube high voltage (17) for an X-ray tube (18), comprising the electronic circuit (1) - a first inverter unit (4) configured to receive an input DC voltage (2) and to convert the input DC voltage (2) into a first AC voltage (8) depending on a first control variable (10); and - a second inverter unit (5) configured to maintain the input DC voltage (2) and to convert the input DC voltage (2) into a second AC voltage (9) depending on a second control variable (11); and - a further circuit section (3) which is configured to generate the tube high voltage (17) depending on the first AC voltage (8) and the second AC voltage (9) and to make the tube high voltage (17) available on the output side; and - a control arrangement (24) configured to determine a controlled variable (25) and to change the first manipulated variable (10) and/or the second manipulated variable (11) depending on the controlled variable (25) in order to control the controlled variable (25) to a predetermined setpoint (26), wherein the control arrangement (24) is configured to determine the controlled variable (25) depending on i) a first alternating current (6) resulting from the first alternating voltage (8) and a second alternating current (7) resulting from the second alternating voltage (9) and/or ii) a first DC current (43) resulting from the input DC voltage (2) at the first inverter unit (4) and a second DC current (44) resulting from the input DC voltage (2) at the second inverter unit (5).
  2. Electronic circuit (1) according to claim 1, wherein the controlled variable (25) depends on a difference between the first alternating current (6) and the second alternating current (7) and/or a difference between the first direct current (43) and the second direct current (44).
  3. Electronic circuit (1) according to claim 1, wherein - the control arrangement (24) is configured to determine a first characteristic value (27) from the first alternating current (6) and a second characteristic value (28) from the second alternating current (7); - the controlled variable (25) depends on the first characteristic value (27) and the second characteristic value (28) or the controlled variable (25) depends on a difference between the first characteristic value (27) and the second characteristic value (28); - the first characteristic value corresponds to a first effective value, a first rectified mean value, or a first peak value; and - the second characteristic value corresponds to a second effective value, a second rectified mean value, or a second peak value.
  4. Electronic circuit (1) according to claim 3, wherein the control arrangement (24) is configured to determine a maximum characteristic value depending on the first characteristic value (27) and the second characteristic value (28), and - to change the first manipulated variable (10) depending on the controlled variable (25) when the first characteristic value (27) is less than the largest characteristic value; and - to change the second manipulated variable (11) depending on the controlled variable (25) when the second characteristic value (28) is less than the largest characteristic value.
  5. Electronic circuit (1) according to one of the preceding claims 1 to 3, wherein the control arrangement (24) is configured to determine a controller manipulated variable (37) depending on the controlled variable (25) and the predetermined setpoint (26), and - the first manipulated variable (10) depends on a difference between a given initial value (40) and the controller manipulated variable (37); and/or - the second manipulated variable (11) depends on a sum of the given initial value (40) and the controller manipulated variable (37).
  6. Electronic circuit (1) according to one of the preceding claims, wherein the further circuit part (3) includes a voltage transformer (15) which is configured to obtain on the primary side a primary AC voltage (14) resulting from the first AC voltage (8) and/or the second AC voltage (9) and to convert the primary AC voltage (14) into a secondary AC voltage (29), wherein the tube high voltage (17) is dependent on the secondary AC voltage (29).
  7. Electronic circuit (1) according to claim 6, wherein the further circuit part (3) includes a rectifier (16) which is configured to convert the secondary AC voltage (29) into the tube high voltage (17).
  8. Electronic circuit (1) according to one of the preceding claims, wherein - the further circuit section (3) contains a first resonant circuit (12) which is coupled on the input side to an output of the first inverter unit (4) and on the output side to an output of the further circuit section (3), which is configured to provide the tube high voltage (17); and - the further circuit part (3) contains a second resonant circuit (13) which is coupled on the input side to an output of the second inverter unit (5) and on the output side to the output of the further circuit part (3) which is set up to provide the tube high voltage (17).
  9. Electronic circuit (1) according to claim 8, wherein an output of the first resonant circuit (12) and an output of the second resonant circuit (13) are coupled together.
  10. Electronic circuit (1) according to one of the preceding claims, wherein the electronic circuit (1) comprises at least one further inverter unit (30), wherein - each further inverter unit (30) of which at least one further inverter unit (30) is configured to obtain the input DC voltage (2) and to convert the input DC voltage (2) into a respective further AC voltage (31) depending on a respective further control variable (33); - the further circuit part (3) is set up to generate the tube high voltage (17) depending on the further alternating voltages (31); - the control arrangement (24) is set up to determine the controlled variable (25) depending on i) the first alternating current (6), the second alternating current (7) and any further alternating current (32) resulting from the further alternating voltages (31) and/or ii) the first direct current (43), the second direct current (44) and each further direct current resulting from the input direct voltage (2) at each further inverter unit (30) of the at least one further inverter unit (30).
  11. X-ray tube system comprising the electronic circuit (1) according to one of the preceding claims and the X-ray tube (18).
  12. Medical imaging system comprising the X-ray tube system according to claim 11.
  13. Method for providing a tube high voltage (17) for an X-ray tube (18), wherein: - an input DC voltage (2) is converted into a first AC voltage (8) depending on a first control variable (10); - the input DC voltage (2) is converted into a second AC voltage (9) depending on a second control variable (11); - the tube high voltage (17) is generated and provided depending on the first alternating voltage (8) and the second alternating voltage (9); - a controlled variable (25) is determined depending on i) a first alternating current (6) resulting from the first alternating voltage (8) and a second alternating current (7) resulting from the second alternating voltage (9) and/or ii) a first DC current (43) resulting from the input DC voltage (2) at the first inverter unit (4) and a second DC current (43) resulting from the input DC voltage (2) at the second inverter unit (4); and - the first manipulated variable (10) and/or the second manipulated variable (11) is changed depending on the controlled variable (25) in order to control the controlled variable (25) to a predetermined setpoint (26).
  14. Method according to claim 13, wherein the controlled variable (25) depends on a difference between the first alternating current (6) and the second alternating current (7) and/or on a difference between the first direct current (43) and the second direct current (44), or the controlled variable (25) depends on a difference between a first characteristic value (27) of the first alternating current (6) and a second characteristic value (28) of the second alternating current (7), wherein - the first characteristic value corresponds to a first effective value, a first rectified mean value, or a first peak value; and - the second characteristic value corresponds to a second effective value, a second rectified mean value, or a second peak value.
  15. Method for operating an X-ray tube (18), wherein the method is carried out according to one of claims 13 or 14 and X-ray radiation is generated by means of the X-ray tube (18) depending on the tube high voltage (17).

Description

The invention relates to an electronic circuit for providing a high voltage to an X-ray tube. The invention also relates to an X-ray tube system with such an electronic circuit and a medical imaging system with such an X-ray tube system. Furthermore, the invention relates to corresponding methods. An X-ray tube is a special type of electron beam tube used to generate X-rays. X-ray tubes are used in various imaging techniques and offer a wide range of applications, including in modern medicine. X-rays are generated using an X-ray tube. Free electrons are required, which are accelerated from a cathode to an anode by means of a defined high voltage applied by the tube. The electrons released per unit of time, i.e., charges, flowing from the cathode to the anode are called the tube current. The high voltage is typically in the range of 25 kV to 600 kV. When the accelerated electrons strike the anode, they release energy, resulting in bremsstrahlung and characteristic radiation. Since the incident electrons can be deflected or scattered in all directions, they release varying amounts of energy as bremsstrahlung depending on the deflection angle. This produces a continuous X-ray spectrum. The overall efficiency, meaning the radiation output relative to the input energy, of an X-ray tube system can be very low. Therefore, it may be necessary to supply the X-ray tube with a very high power output, for example, on the order of 100 kW. Conventionally, X-ray tubes are powered via a power electronic conversion chain. This first converts, for example, a single- or three-phase AC supply voltage into a DC input voltage, also known as the intermediate circuit voltage. In a further step, this intermediate circuit voltage is converted into a high-frequency signal (e.g., 30 kHz - 300 kHz) via an inverter stage. An alternating voltage of adjustable amplitude is generated, which feeds a transmission circuit to the X-ray tube. This transmission circuit can include a resonant circuit, a high-voltage transformer, and high-voltage rectification. The amplitude of the high-frequency alternating voltage can be adjusted, for example, by actively regulating the intermediate circuit voltage, by driving at least one bridge branch of an inverter with a phase shift, or by varying the frequency of the alternating voltage. The purpose of this transmission circuit is to generate a high-voltage direct current between the anode and cathode inside the tube. This accelerates free electrons from a suitably heated emitter, also known as a filament, on one side of the cathode, thus shaping the current within the X-ray tube. This current flow, in turn, generates high-energy X-rays upon striking the anode, which can be used for medical imaging. Since X-ray tubes, especially those used in CT and radiography applications, can have maximum beam powers of 100 kW and above, the power transmission may be distributed across multiple stages, for example, due to thermal stress on the inverter components. This can lead to an asymmetrical current and thus power distribution due to unavoidable tolerances in different stages, such as tolerances in components of the transmission circuit, which is disadvantageous. One object of the present invention is to reduce the asymmetry of the load distribution in multi-stage supply circuits for the high voltage of an X-ray tube. This problem is solved by the respective subject matter of the independent claims. Advantageous further developments and preferred embodiments are the subject matter of the dependent claims, the following description, and the figures. The invention is based on the idea of ensuring a more symmetrical load distribution of the multi-stage supply circuit by means of output-side control within the framework of AC voltage generation. According to one aspect of the invention, an electronic circuit for providing a high voltage to an X-ray tube is presented. The electronic circuit has a The electronic circuit includes a first inverter unit configured to receive an input DC voltage and convert it into a first AC voltage depending on a first control variable. It also includes a second inverter unit configured to receive the input DC voltage and convert it into a second AC voltage depending on a second control variable. Furthermore, the electronic circuit includes another circuit section configured to generate the tube high voltage depending on the first and second AC voltages and to make this high voltage available at an output of the second circuit section. Finally, the electronic circuit includes a control arrangement configured to determine a controlled variable and to modify the first and/or second control variables depending on the controlled variable in order to regulate the controlled variable to a predetermined setpoint. The control arrangement is configured to determine the controlled variable depending on... i) a first alternating current resulting from the first alternating voltage and a second alter