Control device, control method, and control program
The control device adjusts tube voltage and current through processor-managed converters and inverters, ensuring precise matching at high frequencies, addressing adjustment limitations and enabling a compact design.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- FUJIFILM CORP
- Filing Date
- 2022-10-20
- Publication Date
- 2026-05-15
Smart Images
Figure 0007860141000001 
Figure 0007860141000002 
Figure 0007860141000003
Abstract
Description
Technical Field
[0001] The present disclosure relates to a control device, a control method, and a control program.
Background Art
[0002] There is known a control device that includes an inverter circuit that converts a DC voltage into an AC voltage, a booster circuit that boosts the AC voltage output from the inverter circuit, and a rectifier that rectifies the AC voltage output from the booster circuit into a DC tube voltage, and controls the tube voltage supplied to an X-ray tube that emits radiation.
[0003] As a technique related to such a control device, Japanese Patent Application Laid-Open No. 2020-115901 discloses a technique for adjusting the voltage value of DC power boosted by a preceding DC-DC converter and the frequency or duty ratio of the AC voltage converted by an inverter circuit so that the detected tube voltage matches a preset target tube voltage.
[0004] Japanese Patent Application Laid-Open No. 7-211485 also discloses a technique including an inverter control circuit that controls an inverter so that a target tube voltage matches the actual tube voltage of an X-ray tube, and a converter control circuit that controls the output voltage of a converter preceding the inverter so that it matches the target tube voltage.
Summary of the Invention
Problems to be Solved by the Invention
[0005] By the way, when supplying a tube voltage to an X-ray tube, in order to miniaturize the control device, it is desired to drive the inverter circuit at a high frequency. However, when driving the inverter circuit at a high frequency, it may not be possible to secure an adjustment range of the pulse width, and there may be cases where the supplied tube voltage and power cannot be sufficiently adjusted.
[0006] The present disclosure provides a small-sized control device, a control method, and a control program that can sufficiently adjust the tube voltage even when the inverter circuit is driven at a high frequency. [Means for solving the problem]
[0007] A control device according to a first aspect of the present disclosure comprises at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, and is a control device that controls the tube voltage and tube current supplied to the radiation tube that emits radiation, wherein the processor controls the converter to output a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current, and output If the target power is below the first threshold and above the second threshold which is lower than the first threshold, the DC voltage is fixed to the first voltage, the frequency of the inverter circuit is fixed, and the pulse width of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the second threshold, the DC voltage is fixed to the first voltage, the pulse width of the inverter circuit is fixed, and the frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the third threshold which is lower than the second threshold, the DC voltage is lowered to the second voltage which is lower than the first voltage, and the pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the output target tube voltage.
[0008] Furthermore, a control device according to a second aspect of the present disclosure comprises at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, and is a control device that controls the tube voltage and tube current supplied to the radiation tube that emits radiation, wherein the processor controls the converter to output a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current, If the output target power is below the first threshold and exceeds the second threshold which is lower than the first threshold, the DC voltage is fixed to the first voltage, the pulse width of the inverter circuit is fixed, and the frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the second threshold, the DC voltage is fixed to the first voltage, the frequency of the inverter circuit is fixed, and the pulse width of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the third threshold which is lower than the second threshold, the DC voltage is reduced to the second voltage which is lower than the first voltage, and the pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the output target tube voltage.
[0009] A control device according to a third aspect of the present disclosure may be a DC-DC converter in the control device according to the first or second aspect of the present disclosure.
[0010] A control device according to a fourth aspect of the present disclosure, in a control device according to any one of the first to third aspects, the processor may stepwise reduce the DC voltage from a first voltage to a second voltage.
[0011] Furthermore, a control method in a fifth aspect of the present disclosure is a control method executed by the processor of a control device that controls the tube voltage and tube current supplied to a radiation tube that emits radiation, comprising at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, wherein the processor controls the tube voltage and tube current supplied to the radiation tube that emits radiation, and controls the converter to output a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current. If the output target power is below the first threshold and exceeds the second threshold which is lower than the first threshold, the DC voltage is fixed to the first voltage, the frequency of the inverter circuit is fixed, and the pulse width of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the second threshold, the DC voltage is fixed to the first voltage, the pulse width of the inverter circuit is fixed, and the frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the third threshold which is lower than the second threshold, the DC voltage is lowered to the second voltage which is lower than the first voltage, and the pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the output target tube voltage.
[0012] Furthermore, a control method in a sixth aspect of the present disclosure is a control method executed by the processor of a control device that controls the tube voltage and tube current supplied to a radiation tube that emits radiation, comprising at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, wherein the processor controls the tube voltage and tube current supplied to the radiation tube that emits radiation, and controls the converter to output a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current. If the output target power is below the first threshold and exceeds the second threshold which is lower than the first threshold, the DC voltage is fixed to the first voltage, the pulse width of the inverter circuit is fixed, and the frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the second threshold, the DC voltage is fixed to the first voltage, the frequency of the inverter circuit is fixed, and the pulse width of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the third threshold which is lower than the second threshold, the DC voltage is lowered to the second voltage which is lower than the first voltage, and the pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the output target tube voltage.
[0013] Furthermore, a control program in a seventh aspect of the present disclosure is a control program to be executed by the processor of a control device that controls the tube voltage and tube current supplied to a radiation tube that emits radiation, the program to output a DC voltage to the converter according to the output target power derived from the output target tube voltage and the output target tube current, the converter outputs a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current, the program to output a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current to the converter. The system performs control to ensure that the output target power is below the first threshold and exceeds the second threshold which is lower than the first threshold. If this threshold is lower than the first threshold, the DC voltage is fixed to the first voltage, the frequency of the inverter circuit is fixed, and the pulse width of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the second threshold, the DC voltage is fixed to the first voltage, the pulse width of the inverter circuit is fixed, and the frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the third threshold which is lower than the second threshold, the DC voltage is lowered to the second voltage which is lower than the first voltage, and the pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the output target tube voltage.
[0014] Furthermore, the control program of the eighth aspect of the present disclosure is a control program to be executed by the processor of a control device that controls the tube voltage and tube current supplied to the radiation tube that emits radiation, the program to output a DC voltage to the converter according to the output target power derived from the output target tube voltage and the output target tube current to the converter, the converter output a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current to the converter, the converter output a DC voltage corresponding to the output target power derived from the output target tube voltage and the output target tube current. The system performs control to ensure that the output target power is below the first threshold and exceeds the second threshold which is lower than the first threshold. If this threshold is lower than the first threshold, the DC voltage is fixed to the first voltage, the pulse width of the inverter circuit is fixed, and the frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the second threshold, the DC voltage is fixed to the first voltage, the frequency of the inverter circuit is fixed, and the pulse width of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is below the third threshold which is lower than the second threshold, the DC voltage is lowered to the second voltage which is lower than the first voltage, and the pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the output target tube voltage. [Effects of the Invention]
[0015] According to this disclosure, the tube voltage can be adequately adjusted even when the inverter circuit is driven at a high frequency, and the device can be made compact. [Brief explanation of the drawing]
[0016] [Figure 1] This is a side view showing an example of the configuration of a radiographic imaging device. [Figure 2] This is a block diagram illustrating an example of the configuration of a radiographic imaging apparatus according to an exemplary embodiment. [Figure 3] This is a functional block diagram of an example of the configuration of a control device in an exemplary embodiment. [Figure 4]This figure illustrates an example of pulse width, period, and pulse width control by a control device of an exemplary embodiment. [Figure 5] This is a diagram illustrating an example of target output power control information. [Figure 6] This flowchart shows an example of the flow of tube voltage control processing by the control device of the exemplary embodiment. [Figure 7] This figure illustrates other examples of pulse width, period, and pulse width control by the control device of the exemplary embodiment. [Figure 8] This figure illustrates other examples of pulse width, period, and pulse width control by the control device of the exemplary embodiment. [Modes for carrying out the invention]
[0017] Exemplary embodiments of this disclosure will be described in detail below with reference to the drawings.
[0018] First, with reference to Figure 1, the configuration of the mobile radiographic imaging apparatus 1 of this exemplary embodiment will be described. As shown in Figure 1, the radiographic imaging apparatus 1 includes a C-arm 20 having an arm portion 22 and a holding portion 24. One end of the arm portion 22 is provided with a radiation irradiation unit 10 that emits radiation R generated by a radiation source 12.
[0019] The radiation irradiation unit 10 houses a radiation source 12 and an irradiation field limiter 14. The radiation source 12 has a radiation tube 13 (see Figure 2) that generates radiation R, and emits the radiation R generated by the radiation tube 13. The radiation tube 13 has an electron gun (not shown) that emits electrons as a tube current when a tube voltage is applied. The irradiation field limiter 14 is a so-called collimator that limits the irradiation field F of the radiation R generated by the radiation tube. The irradiation field limiter 14 has a configuration in which, for example, four shielding plates made of lead or the like that shield the radiation R are arranged on each side of a rectangle, and a rectangular opening that allows radiation R to pass through is formed in the center. The irradiation field limiter 14 changes the irradiation field of radiation R by changing the size of the opening by changing the position of each shielding plate.
[0020] As shown in FIG. 1, a holding portion 24 is provided at the other end of the arm portion 22. The holding portion 24 holds the storage portion 16. The storage portion 16 stores a radiation detector 38 that detects radiation R and generates image data representing a radiation image. The C-arm 20 of this exemplary embodiment is configured to be able to change the angle of the radiation detector 38 with respect to the Z-axis direction (in the example of FIG. 1, the vertical direction) shown in FIG. 1.
[0021] The radiation detector 38 detects the radiation R that has passed through the subject. Specifically, the radiation detector 38 enters the storage portion 16, detects the radiation R that has reached the detection surface of the radiation detector 38, generates a radiation image based on the detected radiation R, and outputs image data representing the generated radiation image. Hereinafter, a series of operations of irradiating the radiation R from the radiation source 12 and generating a radiation image by the radiation detector 38 may be referred to as "imaging". The type of the radiation detector 38 is not particularly limited. For example, it may be an indirect conversion type radiation detector that converts radiation R into light and then converts the converted light into electric charges, or a direct conversion type radiation detector that directly converts radiation R into electric charges. Further, the radiation detector 38 can capture at least one of still images and moving images. Note that a radiation image captured as a moving image is also called a fluoroscopic image.
[0022] As shown in FIG. 1, a detection surface 17 for detecting the radiation R irradiated from the radiation irradiation portion 10 is provided opposite to the radiation irradiation portion 10 of the storage portion 16. In the radiation image capturing apparatus 1 of this exemplary embodiment, the so-called SID (Source Image Distance), which is the distance between the detection surface 17 and the radiation source 12 of the radiation irradiation portion 10, is set to a fixed value.
[0023] The C-arm 20 is held by a C-arm holder 26 so as to be movable in the direction of arrow A shown in Figure 1. The C-arm holder 26 also has a shaft 27, which connects the C-arm 20 to a bearing 28. The C-arm 20 is rotatable around the shaft 27 as its axis of rotation. The radiographic imaging device 1 also includes a main body 18 with a plurality of wheels 19 at its bottom. A support shaft 29 that extends and retracts in the Z-axis direction of Figure 1 is provided on the upper side of the housing of the main body 18. A bearing 28 is held above the support shaft 29 so as to be movable in the direction of arrow B.
[0024] Furthermore, a user interface section 35, including a display 36 and an operation section 37, is provided at the top of the main body 18. The display 36 and the operation section 37 function as a user interface. The display 36 presents the captured radiographic images and information related to the capture of radiographic images to the operator, such as a technician or physician, who is taking radiographic images with the radiographic imaging device 1. An example of the display 36 is a liquid crystal display. In this exemplary embodiment, a touch panel display integrating the display 36 and the operation section 37 is used. The operation section 37 is operated by the operator when giving instructions regarding the capture of radiographic images. Examples of the operation section 37 include various switches, a touch panel, a stylus, and a mouse. There may also be multiple operation sections 37; for example, the operation section 37 may include a touch panel and a foot switch operated by the operator with their foot.
[0025] Furthermore, the main body 18 houses a control device 30 that controls the tube voltage and tube current supplied to the radiation tube 13 of the radiation source 12, and a power supply unit 48 that supplies power to each part of the radiation imaging device 1.
[0026] Next, with reference to Figure 2, the hardware configuration of the control device 30 in this exemplary embodiment will be described. As shown in Figure 2, the control device 30 includes a CPU (Central Processing Unit) 31, a memory 32 as a temporary storage area, a non-volatile storage unit 33, an I / F (Interface) unit 34, a user interface unit 35 including a display 36 and an operation unit 37, and a high-voltage generation unit 40. The CPU 31, memory 32, storage unit 33, I / F unit 34, display 36, operation unit 37, and high-voltage generation unit 40 are connected to a bus 39. The radiation tube 13 and the irradiation field limiter 14 are also connected to the bus 39.
[0027] The storage unit 33 is implemented by an HDD (Hard Disk Drive), SSD (Solid State Drive), or flash memory, etc. The control program 33A is stored in the storage unit 33 as a storage medium. The CPU 31 reads the control program 33A from the storage unit 33, expands it into memory 32, and executes the expanded control program 33A.
[0028] Furthermore, the memory unit 33 stores target output power control information 33B for obtaining the target output power, which will be described in detail later.
[0029] The I / F unit 34 communicates various types of information with the radiation detector 38 via wireless or wired communication. The I / F unit 34 also communicates various types of information with external devices via wireless or wired communication over a network. Examples of external devices include a RIS (Radiology Information System) for managing imaging orders and a PACS (Picture Archiving and Communication System).
[0030] The high-voltage generation unit 40 has the function of generating tube voltage and tube current according to the exposure conditions and supplying them to the radiation tube 13. The high-voltage generation unit 40 will be described in detail later.
[0031] Next, the functional configuration of the control device 30 in this exemplary embodiment will be described with reference to Figure 3. As shown in Figure 3, the control device 30 comprises a high-voltage generation unit 40, a system control unit 60, an exposure condition control unit 62, and an analysis unit 64. As an example, the control device 30 functions as the system control unit 60, the exposure condition control unit 62, and the analysis unit 64 when the CPU 31 executes the control program 33A.
[0032] The analysis unit 64 performs image analysis on the radiation image to control the dose of radiation R. The exposure condition control unit 62 has the function of controlling the exposure conditions according to the results of the image analysis by the analysis unit 64. An example of image analysis by the analysis unit 64 is the process of generating a density histogram. For example, if the density histogram determines that the radiation image is darker than expected, the exposure condition control unit 62 derives exposure conditions so that the dose of radiation R is higher than the previous one when capturing the radiation image in the next frame of the video recording, and outputs the derived exposure conditions to the system control unit 60.
[0033] The system control unit 60 has the function of controlling the supply of tube voltage and tube current from the high voltage generation unit 40 to the radiation tube 13 in order to obtain the target output power, based on the exposure conditions input by the user using the user interface unit 35 or the exposure conditions output from the exposure condition control unit 62. The system control unit 60 derives the target output power from the target tube voltage and target tube current according to the exposure conditions, and outputs the target tube voltage, target tube current, and target output power to the high voltage control unit 70. In this exemplary embodiment, the target tube voltage, target tube current, and target output power are referred to as "target tube voltage," "target tube current," and "target output power," respectively.
[0034] The high-voltage generation unit 40 includes a high-voltage control unit 70, an output voltage change control unit 72, a DC (Direct Current)-DC converter 74, an inverter circuit 76, a boost circuit 78, a rectifier 80, and a real-time value FB (Feed Back) unit 82. As an example, the control device 30 functions as the high-voltage control unit 70 and the output voltage change control unit 72 when the CPU 31 executes the control program 33A.
[0035] The DC-DC converter 74 has the function of outputting a DC voltage from the DC power supply voltage supplied from the power supply unit 48. As shown in Figure 3, the power supply unit 48 in this exemplary embodiment includes an AC (Alternating Current)-DC power supply 50, a charging unit 52, a battery 54, and a switching unit 56. By connecting to the outlet of the facility power supply 2 of the facility where the radiographic imaging device 1 is installed, the AC-DC power supply 50 is supplied with an AC power supply voltage. The AC-DC power supply 50 converts the supplied AC power supply voltage into a DC power supply voltage. The battery 54 is a battery for wirelessly driving the radiographic imaging device 1, and the charging unit 52 charges the battery 54 with the DC power supply voltage supplied from the AC-DC power supply 50. The switching unit 56 has the function of switching the source of the DC power supply voltage supplied to the high voltage generation unit 40 to either the AC-DC power supply 50 or the battery 54.
[0036] In this exemplary embodiment, the DC-DC converter 74 converts the DC power supply voltage supplied from the power supply unit 48 into a DC voltage corresponding to the target output power, in accordance with the control of the output voltage change control unit 72, and outputs it to the inverter circuit 76. For example, in this exemplary embodiment, the power supply voltage supplied from the power supply unit 48 is lower than the DC voltage (target tube voltage) corresponding to the target output power. Therefore, the DC-DC converter 74 boosts the DC power supply voltage supplied from the power supply unit 48 to a DC voltage corresponding to the target output power and outputs it to the inverter circuit 76.
[0037] The inverter circuit 76 has multiple switching elements and functions to convert the DC voltage output from the DC-DC converter 74 into an AC voltage. The inverter circuit 76 may be of a resonant or non-resonant type.
[0038] The boost circuit 78 boosts the AC voltage output from the inverter circuit 76 according to the target tube voltage and outputs it.
[0039] The rectifier 80 rectifies the AC voltage output from the boost circuit 78 into a DC tube voltage and supplies it to the radiation tube 13.
[0040] The actual value FB unit 82 has the function of detecting the AC voltage after it has been boosted by the boost circuit 78 and feeding back the detected AC voltage to the high-voltage control unit 70 as the actual value of the tube voltage supplied to the radiation tube 13. Hereinafter, the actual value of the tube voltage will be referred to as the "actual tube voltage value".
[0041] The high-voltage control unit 70 has the function of controlling the high voltage generated by the high-voltage generation unit 40 by controlling the DC voltage output from the DC-DC converter 74 and the AC voltage output from the inverter circuit 76. Specifically, the high-voltage generation unit 40 outputs the target output power input from the system control unit 60 to the output voltage change control unit 72.
[0042] The output voltage change control unit 72 has the function of controlling the DC voltage output from the DC-DC converter 74. Specifically, it changes the DC voltage output from the DC-DC converter 74 by controlling the degree of voltage boost in the DC-DC converter 74 according to the target output power instructed by the high voltage control unit 70.
[0043] Furthermore, the high-voltage control unit 70 performs at least one of PFM (Pulse Frequency Modulation) to control the frequency of the AC power converted by the inverter circuit 76 and PWM (Pulse Width Modulation) to control the pulse width, so that the actual tube voltage value input from the actual value FB unit 82 matches the target tube voltage input from the system control unit 60.
[0044] Here, the control of the target output power by the control device 30 of this exemplary embodiment will be described. The control device 30 controls the frequency and pulse width of the DC voltage output from the DC-DC converter 74 and the AC power converted by the inverter circuit 76, according to the target output power.
[0045] As shown in Figure 4(1), the inverter circuit 76 outputs AC power having pulses with period T and pulse width P. The frequency f of this AC power is expressed by the following equation (1). f = 1 / T ... (1)
[0046] Increasing the pulse width P increases the AC power. Also, increasing the frequency f, or in other words, shortening the period T, increases the AC power. Therefore, when it is desired to increase the AC power output from the inverter circuit 76, that is, when the actual tube voltage is smaller than the target tube voltage, the high-voltage control unit 70 performs at least one of the following: increasing the frequency f (shortening the period T) or increasing the pulse width P. As shown in Figure 4 (2), the maximum pulse width Pmax is predetermined. For example, the maximum pulse width Pmax is determined according to the period T and the dead time D. The dead time D is the time required when the positive and negative polarity of the AC power switches.
[0047] Also, as the maximum pulse width Pmax, when the actual tube voltage value is smaller than the target tube voltage, the output voltage change control unit 72 increases the DC voltage output from the DC-DC converter 74. As a result, as shown in (3) of FIG. 4, the height of the pulse becomes larger (higher). The height H1 of the pulse of the AC power shown in (3) of FIG. 4 is higher than the height H of the pulse of the AC power shown in (2) of FIG. 4 (H1 > H).
[0048] On the other hand, by reducing the pulse width P, the AC power becomes smaller. Also, by making the frequency f low, that is, by making the period T long, the AC power becomes smaller. Therefore, when it is desired to reduce the AC power output from the inverter circuit 76, that is, when the actual tube voltage value is smaller than the target tube voltage, the high voltage control unit 70 performs at least one of the control to increase the frequency f (shorten the period T) or the control to increase the pulse width P. Note that, as shown in (4) of FIG. 4, the minimum pulse width Pmin is predetermined.
[0049] Also, in this exemplary embodiment, as the minimum pulse width Pmin, when the actual tube voltage value is larger than the target tube voltage, the output voltage change control unit 72 reduces the DC voltage output from the DC-DC converter 74. As a result, as shown in (5) of FIG. 4, the height of the pulse becomes smaller (lower). The height H2 of the pulse of the AC power shown in (5) of FIG. 4 is lower than the height H of the pulse of the AC power shown in (4) of FIG. 4 (H2 < H2).
[0050] It is preferable to determine the maximum pulse width Pmax and the minimum pulse width Pmin with a margin with respect to the period T for the pulse width P. In the example shown in (1) of FIG. 4, the maximum pulse width Pmax is set as the pulse width P1, and the minimum pulse width Pmin is set as the pulse width P2.
[0051] In this exemplary embodiment, the control device 30 fixes the pulse width of the inverter circuit 76 and lowers the frequency using PFM control. When adjustment by frequency becomes difficult, it switches to PWM control and reduces the pulse width. When adjustment by pulse width becomes difficult, it lowers the DC voltage output from the DC-DC converter 74.
[0052] Specifically, in this exemplary embodiment, the control device 30, when the output target power is below a first threshold and exceeds a second threshold lower than the first threshold, fixes the DC voltage output from the DC-DC converter 74 to a first voltage, fixes the pulse width of the inverter circuit 76, and performs PFM control to control the frequency of the inverter circuit 76 so that the actual tube voltage matches the output target tube voltage. Furthermore, when the output target power is below a second threshold, the control device 30 fixes the DC voltage output from the DC-DC converter 74 to a first voltage, fixes the frequency of the inverter circuit 76, and performs PWM control to control the pulse width of the inverter circuit 76 so that the actual tube voltage matches the output target tube voltage. In addition, when the output target power is below a third threshold lower than the second threshold, the control device 30 lowers the DC voltage output from the DC-DC converter 74 to a second voltage lower than the first voltage, and performs PWM control to control the pulse width of the inverter circuit and PFM control to control the frequency so that the actual tube voltage matches the output target tube voltage.
[0053] As an example, in this exemplary embodiment, the memory unit 33 stores target output power control information 33B, which represents the correspondence between the target output power, the DC voltage output from the DC-DC converter 74, and whether to perform PWM control or PFM control, as information for operating as described above. Figure 5 shows an example of target output power control information 33B.
[0054] In the target output power control information 33B shown in Figure 5, if the target output power is 2.0 kW or less and exceeds 1.2 kW, the output voltage change control unit 72 causes the DC-DC converter 74 to output a DC voltage of 310 V. The high voltage control unit 70 also performs PFM control on the inverter circuit 76, keeping the pulse width fixed, so that the actual tube voltage matches the target tube voltage. Furthermore, if the target output power is 1.2 kW or less and exceeds 1.0 kW, the output voltage change control unit 72 causes the DC voltage output by the DC-DC converter 74 to be reduced to 290 V. When reducing the DC voltage output by the DC-DC converter 74, it may be reduced in steps or continuously using an analog voltage. Note that reducing the DC voltage in steps allows for a simpler circuit and miniaturization of the high voltage generation unit 40 compared to continuous reduction. Furthermore, the number of steps for reducing the DC voltage output by the DC-DC converter 74 is not limited to this exemplary embodiment, and the DC voltage may be changed more finely than in this exemplary embodiment, for example, by setting it to 10 steps.
[0055] Furthermore, the high-voltage control unit 70 performs PFM control on the inverter circuit 76 while keeping the pulse width fixed so that the actual tube voltage matches the target tube voltage. Also, when the output target power is 1.0kW or less and exceeds 0.9kW, the output voltage change control unit 72 keeps the DC voltage output by the DC-DC converter 74 fixed at 290V. Furthermore, the high-voltage control unit 70 performs PWM control on the inverter circuit 76 while keeping the frequency fixed so that the actual tube voltage matches the target tube voltage. Also, when the output target power is 0.9kW or less and exceeds 0.6kW, the output voltage change control unit 72 causes the DC voltage output by the DC-DC converter 74 to be reduced to 280V. Furthermore, the high-voltage control unit 70 performs PFM control on the inverter circuit 76 while keeping the pulse width fixed so that the actual tube voltage matches the target tube voltage. Furthermore, if the output target power is 0.6W or less, the output voltage change control unit 72 keeps the DC voltage output by the DC-DC converter 74 fixed at 280V. Also, the high voltage control unit 70 performs PWM control on the inverter circuit 76 while keeping the frequency fixed so that the actual tube voltage matches the target tube voltage.
[0056] In the target output power control information 33B, the output target powers of 1.2kW and 0.9kW are examples of the first threshold, the output target powers of 1.0kW and 0.6kW are examples of the second threshold, and the output target power of 0.8kW is an example of the third threshold.
[0057] Next, the operation of the control device 30 in this exemplary embodiment will be described with reference to Figure 6. The CPU 31 executes the control program 33A, which in turn executes the tube voltage control process shown in Figure 6. The tube voltage control process shown in Figure 6 is executed, for example, when an instruction to start taking a radiographic image is input to the control device 30.
[0058] In step S100 of Figure 6, the system control unit 60 acquires exposure conditions, including the output target tube voltage and the output target tube current.
[0059] In the next step S102, the system control unit 60 derives the output target power from the output target tube voltage and output target tube current obtained in step S100.
[0060] In the next step S104, the system control unit 60 outputs the target tube voltage and target tube current corresponding to the exposure conditions acquired in step S100, and the output target power derived in step S102, to the high-voltage control unit 70.
[0061] In the next step S106, the output voltage change control unit 72 derives the DC voltage to be output from the DC-DC converter 74 from the target output power. As an example, as described above, the output voltage change control unit 72 refers to the target output power control information 33B and derives the DC voltage corresponding to the target output voltage.
[0062] In the next step S108, the output voltage change control unit 72 controls the DC-DC converter 74 to output the DC voltage derived in step S106 from the DC-DC converter 74. As a result, the DC voltage output from the DC-DC converter 74 is converted into AC power by the inverter circuit 76, boosted by the boost circuit 78, rectified into a DC tube voltage by the rectifier 80, and supplied to the radiation tube 13. The actual value FB unit 82 also detects the actual value of the tube voltage boosted by the boost circuit 78.
[0063] Therefore, in the next step S110, the high-voltage control unit 70 obtains the actual tube voltage value from the actual value FB unit 82.
[0064] In the next step, S112, the high-voltage control unit 70 determines whether the actual tube voltage and the target tube voltage match (actual tube voltage = target tube voltage). Note that the actual tube voltage and the target tube voltage do not need to match perfectly; it is sufficient if they can be considered to match considering the error. If the actual tube voltage and the target tube voltage match, the determination in step S112 becomes a positive determination, and the process proceeds to step S120. On the other hand, if the actual tube voltage and the target tube voltage do not match, the determination in step S112 becomes a negative determination, and the process proceeds to step S114.
[0065] In step S114, the high-voltage control unit 70 determines whether or not to perform frequency control (PFM). As an example, the high-voltage control unit 70 refers to the target output power control information 33B as described above and determines whether the control corresponding to the target output voltage is PFM or PWM. If frequency control (PFM) is to be performed, the determination in step S114 becomes affirmative, and the process proceeds to step S116. In step S116, the high-voltage control unit 70 performs frequency control (PFM) on the inverter circuit 76 while keeping the pulse width fixed, and then proceeds to step S120. Specifically, if the actual tube voltage is greater than the target tube voltage, the high-voltage control unit 70 lowers the frequency of the inverter circuit 76. On the other hand, if the actual tube voltage is less than the target tube voltage, the high-voltage control unit 70 raises the frequency of the inverter circuit 76.
[0066] On the other hand, if frequency control (PFM) is not performed, the determination in step S114 becomes a negative determination, and the process proceeds to step S118. In step S118, the high-voltage control unit 70 performs pulse width control (PWM) on the inverter circuit 76 while keeping the frequency fixed, and then proceeds to step S120. Specifically, if the actual tube voltage is greater than the target tube voltage, the high-voltage control unit 70 reduces the pulse width of the inverter circuit 76. On the other hand, if the actual tube voltage is less than the target tube voltage, the high-voltage control unit 70 increases the pulse width of the inverter circuit 76.
[0067] In step S120, the system control unit 60 determines whether or not to terminate the tube voltage control process shown in Figure 6. In this exemplary embodiment, the tube voltage control process shown in Figure 6 is terminated if a predetermined termination condition is met. A predetermined termination condition is, for example, terminating the tube voltage control process to end radiation irradiation when a predetermined exposure time is reached. If the predetermined termination condition is not met, the determination in step S120 is negative, and the system proceeds to step S122.
[0068] In step S122, the system control unit 60 determines whether or not to change the exposure conditions. As described above, for example, when capturing a radiation image in the next frame during video recording, the exposure conditions may be changed to change the dose of radiation R from the dose of radiation R that was irradiated immediately before. Based on the analysis results of the analysis unit 64, the system control unit 60 determines whether or not it has been instructed by the exposure condition control unit 62 to change the exposure conditions. If the exposure conditions are not to be changed, the determination in step S122 becomes a negative determination, and the process returns to step S110, and steps S110 to S120 are repeated. On the other hand, if the exposure conditions are to be changed, the determination in step S122 becomes a positive determination, and the process proceeds to step S124.
[0069] In step S124, the system control unit 60 derives the output target power from the output target tube voltage and output target tube current corresponding to the exposure conditions that were changed in step S122.
[0070] In the next step S126, the system control unit 60 outputs the target tube voltage and target tube current corresponding to the exposure conditions changed in step S122, and the output target power derived in step S124, to the high-voltage control unit 70.
[0071] In the next step S128, the output voltage change control unit 72 derives the DC voltage to be output from the DC-DC converter 74 from the target output power. As an example, as described above, the output voltage change control unit 72 refers to the target output power control information 33B and derives the DC voltage corresponding to the target output voltage.
[0072] In the next step S130, the output voltage change control unit 72 determines whether or not to change the DC voltage output from the DC-DC converter 74. If the DC voltage derived in step S128 is the same as the DC voltage currently output from the DC-DC converter 74, the determination in step S130 is negative, and the process returns to step S110. On the other hand, if the DC voltage derived in step S128 is not the same as the DC voltage currently output from the DC-DC converter 74, the determination in step S130 is positive, and the process returns to step S108. Note that when changing the exposure conditions while video recording is in progress, there is a time lag between the change in tube current and the change in filament current, so it is preferable to change the DC voltage output from the DC-DC converter 74 taking this time lag into consideration.
[0073] On the other hand, if the predetermined termination conditions are met, the determination in step S120 becomes a positive determination, and the tube voltage control process shown in Figure 6 is terminated.
[0074] As described above, the control device 30 of this exemplary embodiment controls the DC-DC converter 74 to output a DC voltage corresponding to the target output power derived from the target output tube voltage and target output tube current. When the target output power is less than or equal to a first threshold and exceeds a second threshold lower than the first threshold, the control device 30 fixes the DC voltage output from the DC-DC converter 74 to a first voltage, fixes the pulse width of the inverter circuit 76, and performs PWM control to control the frequency of the inverter circuit 76 so that the actual tube voltage matches the target output tube voltage. Furthermore, when the target output power is less than or equal to the second threshold, the control device 30 fixes the DC voltage output from the DC-DC converter 74 to a first voltage, fixes the frequency of the inverter circuit 76, and performs PFM control to control the pulse width of the inverter circuit 76 so that the actual tube voltage matches the target output tube voltage. Furthermore, if the output target power is below a third threshold, which is lower than the second threshold, the control device 30 lowers the DC voltage output from the DC-DC converter 74 to a second voltage, which is lower than the first voltage, and performs PFM control to control the pulse width of the inverter circuit and PWM control to control the frequency so that the actual tube voltage matches the output target tube voltage.
[0075] When the inverter circuit 76 is driven at a high frequency, the period T becomes shorter, which narrows the pulse width adjustment range. Therefore, there is a trade-off between driving the inverter circuit 76 at a high frequency and controlling the pulse width, and it may not be possible to adjust the tube voltage sufficiently. In contrast, the control device 30 of this exemplary embodiment controls the DC voltage output from the DC-DC converter 74 according to the target output voltage, and also controls the tube voltage in combination with PWM control and PFM control, so that the tube voltage can be adjusted sufficiently even when the inverter circuit 76 is driven at a high frequency. Furthermore, since the inverter circuit 76 can be driven at a high frequency, the size of the transformer in the boost circuit 78 can be reduced, and the high-voltage generation unit 40 can be miniaturized.
[0076] In the above exemplary embodiment, the control device 30 fixed the pulse width of the inverter circuit 76, reduced the frequency using PFM control, switched to PWM control when adjustment by pulse width became difficult, reduced the pulse width, and when adjustment by pulse width became difficult, reduced the DC voltage output from the DC-DC converter 74. However, the control device is not limited to this embodiment. For example, the control device 30 may also be configured to fix the frequency of the inverter circuit 76, reduce the pulse width using PWM control, switch to PFM control when adjustment by pulse width became difficult, reduce the frequency, and when adjustment by frequency became difficult, reduce the DC voltage output from the DC-DC converter 74.
[0077] Specifically, in this exemplary embodiment, the control device 30 fixes the DC voltage output from the DC-DC converter 74 to a first voltage, fixes the frequency of the inverter circuit 76, and performs PWM control to control the pulse width of the inverter circuit 76 so that the actual tube voltage matches the output target tube voltage, when the output target power is below a first threshold and exceeds a second threshold that is lower than the first threshold. Furthermore, when the output target power is below a second threshold, the control device 30 fixes the DC voltage output from the DC-DC converter 74 to a first voltage, fixes the pulse width of the inverter circuit 76, and performs PFM control to control the frequency of the inverter circuit 76 so that the actual tube voltage matches the output target tube voltage. In addition, when the output target power is below a third threshold that is lower than the second threshold, the control device 30 lowers the DC voltage output from the DC-DC converter 74 to a second voltage that is lower than the first voltage, and performs PWM control to control the pulse width of the inverter circuit and PFM control to control the frequency so that the actual tube voltage matches the output target tube voltage.
[0078] Figure 7 shows an example of the target output power control information 33B in this case. In the target output power control information 33B shown in Figure 7, if the target output power is 2.0 kW or less and exceeds 1.2 kW, the output voltage change control unit 72 causes the DC-DC converter 74 to output a DC voltage of 310 V. The high voltage control unit 70 also performs PWM control on the inverter circuit 76 while keeping the frequency fixed so that the actual tube voltage matches the target tube voltage. If the target output power is 1.2 kW or less and exceeds 1.0 kW, the output voltage change control unit 72 causes the DC voltage output by the DC-DC converter 74 to be reduced to 290 V. The high voltage control unit 70 also performs PWM control on the inverter circuit 76 while keeping the frequency fixed so that the actual tube voltage matches the target tube voltage. If the target output power is 1.0 kW or less and exceeds 0.9 kW, the output voltage change control unit 72 keeps the DC voltage output by the DC-DC converter 74 fixed at 290 V. Furthermore, the high-voltage control unit 70 performs PFM control on the inverter circuit 76 while keeping the pulse width fixed so that the actual tube voltage matches the target tube voltage. Also, if the output target power is 0.9kW or less and exceeds 0.6kW, the output voltage change control unit 72 causes the DC voltage output by the DC-DC converter 74 to be reduced to 280V. Also, the high-voltage control unit 70 performs PWM control on the inverter circuit 76 while keeping the frequency fixed so that the actual tube voltage matches the target tube voltage. Also, if the output target power is 0.6W or less, the output voltage change control unit 72 keeps the DC voltage output by the DC-DC converter 74 fixed at 280V. Also, the high-voltage control unit 70 performs PFM control on the inverter circuit 76 while keeping the pulse width fixed so that the actual tube voltage matches the target tube voltage. In the target output power control information 33B shown in Figure 7, the target output powers of 1.2kW and 0.9kW are examples of the first threshold, the target output powers of 1.0kW and 0.6kW are examples of the second threshold, and the target output power of 0.8kW is an example of the third threshold.
[0079] The control device 30, by referring to the target output power control information 33B and executing the tube voltage control process shown in Figure 6, controls the DC voltage output from the DC-DC converter 74 according to the target output voltage, as described above. Furthermore, since it controls the tube voltage in combination with PWM control and PFM control, it is possible to adjust the tube voltage sufficiently even while maintaining high-frequency drive of the inverter circuit 76. In addition, since the inverter circuit 76 can be driven at a high frequency, the size of the transformer in the boost circuit 78 can be reduced, and the high-voltage generation unit 40 can be miniaturized.
[0080] Furthermore, to prevent abrupt changes in the DC voltage output from the DC-DC converter 74 and the switching between PWM control and PFM control of the inverter circuit 76, hysteresis may be provided by overlapping the target output power thresholds, as shown in the target output power control information 33B in Figure 8, thereby giving the target output power a range. In this case, the target output power threshold will differ depending on whether the target output power is lowered from the current target output power or raised from the current target output power. Therefore, in the tube voltage control processing, when changing the target output power, the high voltage control unit 70 and the output voltage change control unit 72 determine whether the changed target output power will be higher or lower than the current target output power, and then refer to the target output power control information 33B to perform their respective controls.
[0081] Furthermore, since the tube current changes with filament temperature, the above tube voltage control process can also be applied during calibration to adjust the relationship between the filament current and tube current of the radiation tube 13. For example, the filament current is gradually increased, and the actual value of the tube current is monitored. If the output power corresponding to the actual tube voltage and tube current detected by the actual value FB unit 82 exceeds a threshold, control is performed to increase the DC voltage output from the DC-DC converter 74. In each of the above embodiments, a configuration in which the control device 30 performs control using pre-obtained target output power control information 33B has been described, but a configuration in which control is performed without using the target output power control information 33B is also possible. For example, the control device 30 may acquire the actual pulse width and period in the inverter circuit 76 and control the acquired pulse width and period to adjust them within a predetermined range. For example, a configuration in which the DC voltage output from the DC-DC converter 74 is controlled when the pulse width P falls outside the pulse widths P2 to P1 shown in Figure 4 (1) is also possible. In this case, considering the reproducibility and degree of variation of the tube current, the DC voltage output from the DC-DC converter 74 may be controlled when the number of times the pulse width P falls outside the pulse width P2 to P1 exceeds a specified number.
[0082] In the above-described configuration, the high-voltage generation unit 40 is equipped with a DC-DC converter 74 that outputs a DC voltage from a DC power supply voltage. However, instead of the DC-DC converter 74, the system may also be equipped with an AC-DC converter that outputs a DC voltage from an AC power supply voltage.
[0083] In the above-described embodiment, the radiographic imaging device 1 is described as a mobile radiographic imaging device having a C-arm, but the radiographic imaging device 1 is not limited to this embodiment. For example, it may be a configuration in which a mobile cart having a radiation irradiation unit 10 is used in combination with a radiation detector 38 which is a so-called electronic cassette. Alternatively, for example, it may be a portable radiographic imaging device 1 that is carried and moved by an operator. Furthermore, it is not limited to a mobile radiographic imaging device 1, but may also be a stationary radiographic imaging device 1.
[0084] Furthermore, in the above configuration, for example, the hardware structure of the processing unit that performs various processes such as the system control unit 60, the exposure condition control unit 62, and the analysis unit 64. The following types of processors can be used. As mentioned above, processors include CPUs, which are general-purpose processors that execute software (programs) and function as various processing units, as well as programmable logic devices (PLDs), such as FPGAs (Field Programmable Gate Arrays), whose circuit configurations can be changed after manufacturing, and dedicated electrical circuits, such as ASICs (Application Specific Integrated Circuits), which have circuit configurations specifically designed to perform particular processing.
[0085] A single processing unit may consist of one of these various processors, or it may consist of a combination of two or more processors of the same or different types (for example, a combination of multiple FPGAs, or a combination of a CPU and an FPGA). Alternatively, multiple processing units may be composed of a single processor.
[0086] Examples of configuring multiple processing units with a single processor include, firstly, a configuration where one or more CPUs and software combine to form a single processor, as exemplified by client and server computers, and this processor functions as multiple processing units. Secondly, a configuration using a processor that realizes the functions of the entire system, including multiple processing units, on a single IC (Integrated Circuit) chip, as exemplified by System-on-a-Chip (SoC). Thus, various processing units are configured, in terms of hardware structure, using one or more of the above-mentioned processors.
[0087] Furthermore, the hardware structure of these various processors can more specifically utilize electrical circuits, which are combinations of circuit elements such as semiconductor devices.
[0088] Furthermore, although the above embodiments describe a configuration in which the control program 33A is pre-stored (installed) in the storage unit 33, the invention is not limited to this. The control program 33A may be provided in the form of a recording medium such as a CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), or USB (Universal Serial Bus) memory. Alternatively, the control program 33A may be provided in the form of a download from an external device via a network.
[0089] The disclosure of Japanese Patent Application No. 2021-172693, dated October 21, 2021, is incorporated herein by reference in its entirety.
[0090] All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.
Claims
1. At least one processor, A converter that outputs a DC voltage from the power supply voltage, An inverter circuit that converts the DC voltage output from the converter into an AC voltage, A boost circuit that boosts the AC voltage output from the inverter circuit, A rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, A radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, Equipped with, A control device for controlling the tube voltage and tube current supplied to a radiation tube that emits radiation, The aforementioned processor, The converter is controlled to output a DC voltage corresponding to the target output power derived from the target output tube voltage and target output tube current. If the output target power is less than or equal to the first threshold and exceeds a second threshold that is lower than the first threshold, The DC voltage is fixed to the first voltage, The frequency of the inverter circuit is fixed, The pulse width of the inverter circuit is controlled so that the actual tube voltage value matches the output target tube voltage. If the output target power is less than or equal to the second threshold, The DC voltage is fixed to the first voltage, The pulse width of the inverter circuit is fixed, The frequency of the inverter circuit is controlled so that the actual tube voltage value matches the target output tube voltage. If the output target power is less than or equal to the third threshold, which is lower than the second threshold, The DC voltage is reduced to a second voltage that is lower than the first voltage. The pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the target output tube voltage. Control device.
2. The aforementioned converter is a DC-DC converter. The control device according to claim 1.
3. The aforementioned processor, The DC voltage is gradually reduced from the first voltage to the second voltage. The control device according to claim 1.
4. At least one processor, A converter that outputs a DC voltage from the power supply voltage, An inverter circuit that converts the DC voltage output from the converter into an AC voltage, A boost circuit that boosts the AC voltage output from the inverter circuit, A rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, A radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, Equipped with, A control device for controlling the tube voltage and tube current supplied to a radiation tube that emits radiation, The aforementioned processor, The converter is controlled to output a DC voltage corresponding to the target output power derived from the target output tube voltage and target output tube current. If the output target power is less than or equal to the first threshold and exceeds a second threshold that is lower than the first threshold, The DC voltage is fixed to the first voltage, The pulse width of the inverter circuit is fixed, The frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is less than or equal to the second threshold, The DC voltage is fixed to the first voltage, The frequency of the inverter circuit is fixed, The pulse width of the inverter circuit is controlled so that the actual tube voltage value matches the target output tube voltage. If the output target power is less than or equal to the third threshold, which is lower than the second threshold, The DC voltage is reduced to a second voltage that is lower than the first voltage. The pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the target output tube voltage. Control device.
5. The aforementioned converter is a DC-DC converter. The control device according to claim 4.
6. The aforementioned processor, The DC voltage is gradually reduced from the first voltage to the second voltage. The control device according to claim 4.
7. A control method executed by the processor of a control device that controls the tube voltage and tube current supplied to a radiation tube that emits radiation, comprising at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, wherein the processor controls the tube voltage and tube current supplied to the radiation tube that emits radiation, The converter is controlled to output a DC voltage corresponding to the target output power derived from the target output tube voltage and target output tube current. If the output target power is less than or equal to the first threshold and exceeds a second threshold that is lower than the first threshold, The DC voltage is fixed to the first voltage, The frequency of the inverter circuit is fixed, The pulse width of the inverter circuit is controlled so that the actual tube voltage value matches the output target tube voltage. If the output target power is less than or equal to the second threshold, The DC voltage is fixed to the first voltage, The pulse width of the inverter circuit is fixed, The frequency of the inverter circuit is controlled so that the actual tube voltage value matches the target output tube voltage. If the output target power is less than or equal to the third threshold, which is lower than the second threshold, The DC voltage is reduced to a second voltage that is lower than the first voltage. The pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the target output tube voltage. Control method.
8. A control method executed by the processor of a control device that controls the tube voltage and tube current supplied to a radiation tube that emits radiation, comprising at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, wherein the processor controls the tube voltage and tube current supplied to the radiation tube that emits radiation, The converter is controlled to output a DC voltage corresponding to the target output power derived from the target output tube voltage and target output tube current. If the output target power is less than or equal to the first threshold and exceeds a second threshold that is lower than the first threshold, The DC voltage is fixed to the first voltage, The pulse width of the inverter circuit is fixed, The frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is less than or equal to the second threshold, The DC voltage is fixed to the first voltage, The frequency of the inverter circuit is fixed, The pulse width of the inverter circuit is controlled so that the actual tube voltage value matches the target output tube voltage. If the output target power is less than or equal to the third threshold, which is lower than the second threshold, The DC voltage is reduced to a second voltage that is lower than the first voltage. The pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the target output tube voltage. Control method.
9. A control program to be executed by the processor of a control device that controls the tube voltage and tube current supplied to a radiation tube that emits radiation, comprising at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, wherein the control device controls the tube voltage and tube current supplied to the radiation tube that emits radiation, The converter is controlled to output a DC voltage corresponding to the target output power derived from the target output tube voltage and target output tube current. If the output target power is less than or equal to the first threshold and exceeds a second threshold that is lower than the first threshold, The DC voltage is fixed to the first voltage, The frequency of the inverter circuit is fixed, The pulse width of the inverter circuit is controlled so that the actual tube voltage value matches the output target tube voltage. If the output target power is less than or equal to the second threshold, The DC voltage is fixed to the first voltage, The pulse width of the inverter circuit is fixed, The frequency of the inverter circuit is controlled so that the actual tube voltage value matches the target output tube voltage. If the output target power is less than or equal to the third threshold, which is lower than the second threshold, The DC voltage is reduced to a second voltage that is lower than the first voltage. The pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the target output tube voltage. Control program.
10. A control program to be executed by the processor of a control device that controls the tube voltage and tube current supplied to a radiation tube that emits radiation, comprising at least one processor, a converter that outputs a DC voltage from a power supply voltage, an inverter circuit that converts the DC voltage output from the converter into an AC voltage, a boost circuit that boosts the AC voltage output from the inverter circuit, a rectifier that rectifies the AC voltage output from the boost circuit into a DC tube voltage, and a radiation tube having an electron gun that emits electrons as a tube current when a tube voltage is applied, wherein the control device controls the tube voltage and tube current supplied to the radiation tube that emits radiation, The converter is controlled to output a DC voltage corresponding to the target output power derived from the target output tube voltage and target output tube current. If the output target power is less than or equal to the first threshold and exceeds a second threshold that is lower than the first threshold, The DC voltage is fixed to the first voltage, The pulse width of the inverter circuit is fixed, The frequency of the inverter circuit is controlled so that the actual tube voltage matches the output target tube voltage. If the output target power is less than or equal to the second threshold, The DC voltage is fixed to the first voltage, The frequency of the inverter circuit is fixed, The pulse width of the inverter circuit is controlled so that the actual tube voltage value matches the target output tube voltage. If the output target power is less than or equal to the third threshold, which is lower than the second threshold, The DC voltage is reduced to a second voltage that is lower than the first voltage. The pulse width and frequency of the inverter circuit are controlled so that the actual tube voltage matches the target output tube voltage. Control program.