WO2015199218A1

WO2015199218A1 - High voltage device

Info

Publication number: WO2015199218A1
Application number: PCT/JP2015/068506
Authority: WO
Inventors: 祐樹河口; 庄司　浩幸; 浩和飯嶋; 美奈チャホン小川; 堂本　拓也
Original assignee: 株式会社日立メディコ
Priority date: 2014-06-27
Filing date: 2015-06-26
Publication date: 2015-12-30
Also published as: JP2016012397A; JP6463913B2

Abstract

Provided is a high voltage device in which the rise and fall times of the output voltage can be reduced while suppressing the switching loss during the normal period. The high voltage device is equipped with: an inverter connected between a DC power supply and a resonant circuit and converting DC voltage to AC voltage; said resonant circuit; a rectifier circuit connected between said resonant circuit and a load, rectifying the AC voltage, and supplying a DC voltage to the load; and a control means for controlling said inverter. In the high voltage device, said control means is equipped with: a first mode in which said inverter operates so that the frequency of resonant current supplied to said resonant circuit from said inverter becomes substantially equal to the frequency at which said inverter is driven; a second mode in which said inverter operates so that the frequency of resonant current supplied to said resonant circuit from said inverter becomes (natural number + 1) times the frequency at which said inverter is driven; and a switching means for switching between said first mode and said second mode.

Description

High voltage equipment

The present invention relates to an X-ray apparatus such as an X-ray CT apparatus and a general X-ray imaging apparatus, and a high voltage apparatus that supplies a high DC voltage to a load.

For example, in an X-ray apparatus such as an X-ray CT apparatus and a general X-ray imaging apparatus, it is necessary to supply a DC high voltage of about several tens of kV to 100 kV to an X-ray tube as a load. Therefore, for example, configurations disclosed in Patent Literature 1 and Patent Literature 2 are used as a high voltage device that supplies a high voltage to the X-ray tube.

In the X-ray high voltage apparatus described in Patent Document 1 and Patent Document 2, a converter that inputs a commercial power supply and outputs a DC voltage, an inverter that inputs a DC voltage and generates a high-frequency AC voltage, and boosts the AC voltage And a rectifier circuit (for example, a multi-stage voltage doubler rectifier circuit or a Cockcroft-Walton circuit) that generates a DC voltage by inputting an AC voltage, and supplies a DC high voltage to the X-ray tube. It is configured to supply.

In recent years, in the X-ray CT apparatus, from the viewpoint of reducing the exposure of the subject and improving the accuracy of the captured image, a multi-energy imaging technique for obtaining X-ray transmission data by irradiating an X-ray beam having different energy during scanning. Has been proposed. In the multi-energy imaging technology, it is necessary to switch the voltage of the X-ray tube (hereinafter referred to as tube voltage) at a high speed in a cycle of several hundreds μs during scanning, and the output voltage supplied to the X-ray tube also in a high voltage apparatus. There is a need for faster rise and fall times.

Since the rise and fall of the tube voltage largely depends on the smoothing capacitor capacity of the rectifier circuit, reducing the smoothing capacitor capacity is an effective means. However, since the X-ray apparatus needs to suppress the pulsation of the tube voltage to a specified value or less, the smoothing capacitor capacity of the rectifier circuit cannot be simply reduced.

As a means for solving this problem, it is known to increase the drive frequency of the inverter. By increasing the drive frequency of the inverter, the AC voltage supplied to the rectifier circuit can be increased, so that the capacitor capacity can be reduced while suppressing the pulsation of the tube voltage. By reducing the capacitor capacity, the rise and fall of the tube voltage can be speeded up. Further, the response speed of the output voltage can be improved by increasing the drive frequency of the inverter. However, if the drive frequency of the inverter is simply increased, the switching loss increases. Therefore, there is a problem that it becomes difficult to cool the switching element, particularly when shooting with a constant tube voltage maintained for a long time.

Non-Patent Document 3 is disclosed as means for speeding up the start-up of the X-ray high-voltage device. In the technique described in Non-Patent Document 3, in the rising period until the tube voltage reaches a predetermined value, the output power supplied from the inverter to the rectifier circuit is increased as compared with the steady period, so that the rising speed of the tube voltage is increased. We are trying to make it. As a result, it is possible to increase the rise of the tube voltage without increasing the drive frequency of the inverter.

Japanese Patent Laid-Open No. 10-41093 JP 2009-43571 A

However, in the technique described in Non-Patent Document 3, when the smoothing capacitor capacity is the same, it is necessary to increase the output current of the inverter in proportion to the increase in the rising speed of the tube voltage. There are challenges that will be difficult. Moreover, since the fall of the tube voltage depends on the equivalent resistance value of the X-ray tube and the time constant of the capacitance of the smoothing capacitor, the technique described in Non-Patent Document 3 speeds up the fall of the tube voltage. Is difficult.

In order to solve the above problems, the present invention is connected between a DC power source and a resonance circuit, and is connected between an inverter that converts a DC voltage into an AC voltage, the resonance circuit, and the resonance circuit and a load. A high voltage apparatus comprising: a rectifier circuit that rectifies an AC voltage and supplies a DC voltage to a load; and a control unit that controls the inverter, wherein the control unit resonates from the inverter to the resonance circuit. The first mode in which the frequency of the current operates to be substantially equal to the frequency for driving the inverter, and the frequency of the resonance current supplied from the inverter to the resonance circuit is the (natural number + 1) of the frequency for driving the inverter. ) A second mode that operates so as to be doubled, and a switching unit that switches between the first mode and the second mode.

According to a preferred embodiment of the present invention, it is possible to reduce the smoothing capacitor capacity while suppressing an increase in switching loss of the inverter in a steady period. Furthermore, since the drive frequency of the inverter can be increased only during the rising period of the output voltage, a high voltage device that achieves both low inverter loss during the steady period and high speed of rising and falling of the output voltage. Can be provided.

1 is a circuit configuration diagram of a high voltage device according to Embodiment 1. FIG. 3 is a flowchart for explaining the operation of the high-voltage device according to the first embodiment. FIG. 4 is a waveform diagram for explaining the operation of the high voltage device according to the first embodiment. FIG. 4 is a waveform diagram for explaining the operation of the high voltage device according to the first embodiment. FIG. 4 is a waveform diagram for explaining the operation of the high voltage device according to the first embodiment. FIG. 3 is a circuit configuration diagram of a high voltage device according to a second embodiment. The wave form diagram explaining operation | movement of the high voltage apparatus of Example 2. FIG. FIG. 6 is a circuit configuration diagram of a high voltage device according to a third embodiment. FIG. 6 is a waveform diagram for explaining the operation of the high voltage device according to the third embodiment. FIG. 6 is a circuit configuration diagram of a high voltage device according to a fourth embodiment. 10 is a flowchart for explaining the operation of the high voltage device according to the fourth embodiment. The figure explaining operation | movement of the high-voltage apparatus of Example 4. FIG. The figure explaining operation | movement of the high-voltage apparatus of Example 4. FIG. The figure explaining operation | movement of the high-voltage apparatus of Example 4. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, an X-ray diagnostic imaging apparatus using an X-ray tube as a load will be described as an example.

Example 1 of the present invention will be described with reference to FIGS. FIG. 1 is a circuit configuration diagram of a high-voltage device according to Embodiment 1 of the present invention. This high-voltage device includes a DC power source 1 as a power source, and includes an inverter 2, a resonance circuit 3, a rectifier circuit 4, a control unit 5, and a voltage detection unit 6. A DC voltage is supplied to an X-ray tube 7 as a load. Supply high voltage.

The inverter 2 receives the DC power source 1 and outputs an AC voltage having an arbitrary frequency to the resonance circuit 3, and is composed of switching elements Q1 to Q4 connected in a bridge, and each of the switching elements Q1 to Q4 has a reverse polarity. Parallel diodes D1 to D4 are connected.

The resonant circuit 3 includes a transformer 31 and a parallel resonant capacitor Cp connected in parallel to both ends of the secondary winding N2, and supplies high-frequency AC power to the rectifier circuit 4. The transformer 31 includes a resonant inductor Lr connected in series with the primary winding N1, a primary winding N1, a magnetic core T1, and a secondary winding N2.

The rectifier circuit 4 includes bridge-connected rectifier diodes Dr1 to Dr4 and a smoothing capacitor Cm. The rectifier circuit 4 rectifies and smoothes the AC voltage output between the terminals of the parallel resonant capacitor Cp and supplies the DC voltage to the load 7. . At this time, since a high voltage of about several tens to one hundred kV is applied to the rectifier diodes Dr1 to Dr4, a configuration in which a plurality of elements are connected in series is used. Thus, when a rectifier circuit is configured by connecting a plurality of elements in series, a balancing capacitor for equalizing the voltage applied to the elements may be connected in parallel with the elements.

The control means 5 controls the switching elements Q1 to Q4, and includes a gate signal generation means 51 for generating gate signals of the switching elements Q1 to Q4, a basic resonance mode 53, an N-fold resonance mode 54, and a switching means. 52.

The control means 5 is connected to the voltage detection means 6 and can detect the voltage of the X-ray tube 7 (hereinafter referred to as tube voltage). The switching unit 52 switches between the basic resonance mode 53 and the N-fold resonance mode 54 based on the tube voltage detected from the voltage detection unit 6.

With this configuration, the inverter 2 operates as a resonant inverter in which the inverter output current I1 (hereinafter referred to as the resonant current I1) supplied to the resonant circuit 3 is sinusoidal.

In the basic resonance mode 53, the inverter 2 is operated so that the frequency of the resonance current I1 supplied from the inverter 2 to the resonance circuit 3 is substantially equal to the drive frequency of the inverter 2. Here, being approximately equal means that the relationship between the drive frequency fsw of the inverter 2 and the frequency fr of the resonance current I1 operates as a general resonance inverter that satisfies the equation (1).

In the N-fold resonance mode 54, the inverter 2 is operated so that the frequency of the resonance current I1 supplied from the inverter 2 to the resonance circuit 3 is N times the drive frequency of the inverter 2. Here, N (hereinafter referred to as a multiple) represents (natural number + 1). In this embodiment, a case where N = 3 will be described.

FIG. 2 is a flowchart showing the logic of the operation from the rising period of the high voltage device of FIG. 1 to the transition to the steady period. However, S100 to S105 in FIG. 2 indicate Step 100 to Step 105. FIG. 3 shows changes of the output voltage V1, the resonance current I1, and the tube voltage Vx of the inverter 2 with time t. FIG. 4 shows an enlarged operation waveform in the vicinity of time t1 in FIG. 3, depending on the time t of the gate signals G1 to G4 for controlling the switching elements Q1 to Q4, the output voltage V1 of the inverter 2, the resonance current I1, and the tube voltage Vx. It shows a change. Here, the currents in all the operation waveform diagrams including FIG. 3 are positive in the current flowing from the left to the right in each element in the circuit diagram of FIG.

Hereinafter, the operation of the high voltage apparatus according to the first embodiment of the present invention will be described with reference to FIGS.
<Description of Operation of Example 1>
A case where the tube voltage target value Vx1 at the time of photographing instructed from the host system and the tube voltage switching command value Vx2 for determining the timing for switching the operation mode are the same (Vx1 = Vx2) will be described.

At this time, the drive frequency fsw of the inverter and the constants of the resonance circuit 3 are set so that the frequency of the resonance current I1 in the basic resonance mode 53 and the frequency of the resonance current I1 in the N-fold resonance mode 54 shown in FIG. Set. In the present embodiment, the constant of the resonance circuit 3 is the same in the basic resonance mode 53 and the N-fold resonance mode 54.
(Step 100)
Here, when the tube voltage target value Vx1 at the time of photographing is input, a tube voltage switching command value Vx2 that determines the timing for switching the operation mode is set. In this embodiment, the target value Vx1 and the switching command value Vx2 are set to the same voltage value (Vx1 = Vx2). However, the target value Vx1 and the switching command value Vx2 may be set to different values.
(Step 101)
When the tube voltage target value Vx1 and the switching command value Vx2 are determined in step 100, the switching means 52 sets the inverter 2 to the basic resonance mode 53 and starts the operation (period t0 to t1 in FIG. 3). . At this time, the drive frequency fsw of the inverter 2 operates at a predetermined constant value fsw1.
(Step 102)
Here, the voltage detection means 6 compares the tube voltage Vx and the switching command value Vx2, and determines the switching of the operation mode of the inverter 2. When the tube voltage Vx has not reached the switching command value Vx2 (Vx <Vx2), the operation in the basic resonance mode 53 is continued.
(Step 103)
If it is determined in step 102 that the tube voltage Vx has reached the switching command value Vx2 (time t1 in FIG. 3), the switching means 52 switches the inverter 2 to the N-fold resonance mode 54 (from time t1 to time t1 in FIG. 3). timing of t3). At this time, as shown in FIG. 4, the switching means 52 is synchronized with the operation period of the basic resonance mode 53 (the H signal or L signal of the gate signals G1, G4 and the H signal or L signal of the gate signals G2, G3). The operation mode is shifted at the timing of switching.

By controlling the gate signals G1 to G4 in this way, the pulsation of the tube voltage Vx that occurs at the operation mode switching timing can be suppressed, so that a smooth rise is possible. At this time, the drive frequency fsw of the inverter 2 operates at a value set in advance according to the tube voltage target value Vx1. As shown in FIG. 3, although the pulsation ΔVx of the tube voltage Vx occurs at the operation mode switching timing, it is considered that there is no problem because it is a rising period.
(Step 104)
Here, the inverter 2 is operated in the N-fold resonance mode 54, the tube voltage Vx detected by the voltage detection means 6 is compared with the target value Vx1, and the transition to the steady period is determined.
(Step 105)
In step 104, when the tube voltage Vx reaches the target value Vx1 (time t2 in FIG. 3), it is determined that the tube voltage has shifted to the steady period, and the flow proceeds to step 105. In step 105, although not shown in FIG. 1, an instruction to start photographing is transmitted from the control means 5 to the host system. At this time, the inverter 2 continues to operate in the N-fold resonance mode 54.

As described above, the high voltage device of this embodiment suppresses the pulsation of the tube voltage without increasing the drive frequency fsw of the inverter 2 by setting the operation mode of the inverter 2 in the steady period to the N-fold resonance mode 54. However, the smoothing capacitor capacity of the rectifier circuit 4 can be reduced. Further, in the rising period, the driving frequency fsw1 in the rising period is changed to the driving frequency fsw2 in the steady period by switching the operation mode of the inverter 2 to the basic resonance mode 53 and the N-fold resonance mode 54 according to the tube voltage condition. Compared with this, the frequency can be increased. By increasing the drive frequency fsw of the inverter 2, the response speed of the output voltage can be improved.
<Modification of Example 1>
A modification of the first embodiment will be described with reference to FIG. FIG. 5 shows an example in which the tube voltage target value Vx1 at the time of photographing instructed by the host system and the tube voltage target value Vx2 for determining the timing for switching the operation mode of the inverter 2 are different conditions (Vx1 ≠ Vx2). Show.

In FIG. 5, the tube voltage switching command value Vx2 is set to a value lower than the target value Vx1. As shown in FIG. 5, by setting the switching command value Vx2 to be lower than the target value Vx1, the pulsation width ΔVx of the tube voltage Vx generated at the switching timing of the operation mode can be suppressed to a small value. Compared with the condition of FIG. 3 in which the command value Vx2 is the same, the rise of the tube voltage can be further increased.

As described above, in the present embodiment, by switching the operation mode of the inverter to the basic resonance mode and the N-fold resonance mode according to the tube voltage condition, the rise of the tube voltage is suppressed while suppressing the loss of the inverter in the steady period. The speed can be increased.

In this embodiment, since the drive frequency of the inverter in the rising period is higher than that in the steady period, the switching loss increases. However, there is no problem because the rising period is sufficiently shorter than the steady period. . In the present embodiment, the switching timing between the basic resonance mode and the N-fold resonance mode is determined based on the value of the tube voltage, but is not limited thereto. For example, a counter may be provided inside the control means, and the operation mode may be changed based on the elapsed time from the start of each operation mode. In this embodiment, the multiple of the N-fold resonance mode is set to N = 3. However, N = 4 or N = 5 may be set according to the tube voltage target value Vx1.

Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 6 is a circuit configuration diagram of a high voltage device according to the second embodiment of the present invention. FIG. 7 shows operation waveforms of the high voltage device of FIG. Similar to the high voltage device of the first embodiment, this high voltage device uses a DC power source 1 as a power source, and includes an inverter 2, a resonance circuit 203, a rectifier circuit 204, a control means 205, and a voltage detection means 6. The high voltage of direct current is supplied to the X-ray tube 7 which is a load.

The difference from the first embodiment is that a series resonant capacitor Cs connected in series with the primary winding N11 is connected to the resonance circuit 203, a point that the cock croft circuit is connected in multiple stages in the rectifier circuit 204, and control. The N-fold resonance mode 54 in the means 205 is provided with a feedback loop of the tube voltage Vx.

Hereinafter, the operation of the high voltage apparatus according to the second embodiment of the present invention will be described with reference to FIG.
<Description of operation>
(Mode 1) Times t0 to t21 in FIG.
In the period from time t0 to t21 in FIG. 7, the inverter 2 operates in the basic resonance mode 53 as in the period from time t0 to t1 in FIG. At this time, the drive frequency fsw of the inverter 2 operates at a predetermined constant value.
(Mode 2) Times t21 to t22 in FIG.
When the tube voltage Vx reaches the switching command value Vx2 at time t21, the switching means 52 causes the inverter 2 to shift to the N-fold resonance mode 54. Here, the drive frequency fsw of the inverter 2 is set to a value calculated based on the difference between the detected tube voltage Vx and the command value Vx1.

In this case, PI control may be used as a method for calculating the drive frequency fsw, or it is derived from a table showing the relationship between the prepared difference between the tube voltage Vx and the command value Vx1 and the drive frequency fsw of the inverter 2. Also good. In the present embodiment, as shown in FIG. 7, the resonance current I1a in the rising period may be larger than the resonance current I1b in the steady period. In this regard, there is no problem because the time is shorter than the entire operation period.
(Mode 3) Times t22 to t23 in FIG.
When the tube voltage Vx reaches the target value Vx1 at time t22, the control unit 205 determines that the tube voltage has reached the steady period, and transmits a command to start imaging to the host system. At this time, the inverter 2 is continuously operated in the N-fold resonance mode 54.

As described above, in this embodiment, the N-fold resonance mode 54 of the control unit 205 is provided with a feedback loop of the tube voltage Vx. As a result, it is possible to shorten the period (the period from time t21 to t22 in FIG. 7) until the tube voltage reaches the target value Vx1 after the operation mode of the inverter 2 is switched to the N-fold resonance mode 54. Compared to 1, the rise of the tube voltage Vx can be further increased.

Next, a third embodiment of the present invention will be described with reference to FIGS.

FIG. 8 is a circuit configuration diagram of the high voltage device according to the third embodiment of the present invention. FIG. 9 shows operation waveforms of the high voltage device of FIG. Similar to the high voltage device of the second embodiment, this high voltage device uses a DC power source 1 as a power source, and includes an inverter 2, a resonance circuit 303, a rectifier circuit 304, a control means 305, and a voltage detection means 6. The high voltage of direct current is supplied to the X-ray tube 7 which is a load.

The difference from the second embodiment is that the secondary winding of the transformer in the resonance circuit 303 is divided into the secondary winding N21 and the secondary winding N22, and the secondary winding N21 and the secondary winding are configured. A point in which parallel resonant capacitors Cp21 and Cp22 are connected in parallel between the terminals of N22, a point in which the voltage doubler rectifier circuit is connected in multiple stages in the rectifier circuit 304, and a resonance supplied from the inverter 2 to the resonance circuit 303 The current detection means 8 for detecting the current I1 is provided, and the basic resonance mode 53 in the control means 305 is provided with a feedback loop for the resonance current I1 and a feedback loop for the tube voltage Vx. The current detection means 8 detects the average value or peak value of the resonance current I 1 and inputs it to the control means 305.

Hereinafter, the operation of the high voltage device according to the third embodiment of the present invention will be described with reference to FIG.
(Mode 1) Period from Time t0 to t32 In the period from Time t0 to t32 in FIG. 9, the inverter 2 operates in the basic resonance mode 53. At this time, the basic resonance mode 53 is based on the difference between the resonance current I1 detected by the current detector 8 and the target value I1ref so that the resonance current I1 approaches the target value I1ref by using a feedback loop of the resonance current I1. The drive frequency fsw of the inverter 2 is determined. In the operation of FIG. 9, the target value I1ref is set so that the resonance current I1a in the rising period becomes a value (I1a> I1b) larger than the resonance current I1b in the steady period. This period is continued until the tube voltage Vx reaches the command value Vx22.
(Mode 2) Period from Time t32 to t33 When the tube voltage Vx reaches the command value Vx22 at the timing of time t32, the basic resonance mode 53 is switched to a feedback loop of the tube voltage Vx. During this period, the drive frequency fsw of the inverter 2 is determined based on the difference between the tube voltage value Vx detected by the voltage detection means 6 and the switching command value Vx2. This period is continued until the tube voltage Vx reaches the switching command value Vx2.
(Mode 3) Time t33 to t34
When the tube voltage Vx reaches the switching command value Vx2 at the timing of time t33, the switching unit 52 switches the operation mode of the inverter 2 from the basic resonance mode 53 to the N-fold resonance mode 54. At this time, the N-fold resonance mode 54 becomes a feedback loop of the tube voltage Vx, and the drive frequency fsw of the inverter 2 is the difference between the tube voltage detection value Vx and the target value Vx1 so that the tube voltage Vx approaches the target value Vx1. To be determined.
(Mode 4) Time t34 to t35
When the tube voltage Vx reaches the target value Vx1 at the timing of time t34, the control unit 305 determines that the tube voltage Vx has shifted to the steady period and issues an instruction to start photographing to the host system. At this time, the inverter 2 is continuously operated in the N-fold resonance mode 54.

As described above, in this embodiment, the basic resonance mode 53 is provided with the feedback loop of the resonance current I1 and the feedback loop of the tube voltage Vx. Thus, the basic resonance mode period can be shortened by setting the target value of the resonance current so that the resonance current during the rising period becomes larger than the steady period. It is possible to further increase the speed of the rise.

In the present embodiment, the current detection means 8 detects the average value or peak value of the resonance current I1, but the zero cross point of the resonance current I1 may be detected. By detecting the zero-cross point of the resonance current, it is possible to determine whether the drive frequency fsw of the inverter 2 and the resonance current frequency have a predetermined relationship. Further, in the high voltage device of the present embodiment, the operation mode of the inverter 2 is switched by detecting the tube voltage Vx, but the present invention is not limited to this. For example, the voltage across the smoothing capacitor Cm1 of the rectifier circuit 204 may be detected, and the operation mode of the inverter 2 may be switched according to the value of the voltage across the smoothing capacitor Cm1. In this embodiment, only the basic resonance mode 53 is provided with the feedback loop for the resonance current I1, but the N-fold resonance mode 54 may also be provided with a feedback loop for the resonance current I1. By providing the feedback loop of the resonance current I1 in the N-fold resonance mode 54, it is possible to determine whether the relationship between the drive frequency fsw of the inverter 2 and the frequency of the resonance current I1 is N times.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.

FIG. 10 is a circuit configuration diagram of a high voltage device according to the fourth embodiment of the present invention. FIG. 11 is a flowchart of the operation logic until the operation pattern of the high voltage device shown in FIG. 10 is determined. However, S400 to S408 in FIG. 11 indicate Step 400 to Step 408. FIGS. 12 to 14 are diagrams showing operation patterns 1 to 3 of the high-voltage device of FIG. 10 and show changes of the inverter drive frequency fsw, inverter output voltage V1, inverter output current I1, and tube voltage Vx with time t. ing.

Similar to the high voltage device of the third embodiment, this high voltage device uses a DC voltage 1 as a power source, and includes an inverter 2, a resonance circuit 303, a rectifier circuit 304, a control means 405, and a voltage detection means 6. The high voltage of direct current is supplied to the X-ray tube 7 which is a load.

The differences from the third embodiment are that an operation mode switching unit 455 and an operation pattern determination unit 456 are provided in the switching unit 452 and a photographing pattern selection unit 9 is provided.

Hereinafter, the operation of the high voltage apparatus according to the fourth embodiment of the present invention will be described with reference to FIGS. (Step 400)
In step 400, arbitrary shooting pattern information corresponding to the shooting location and the condition of the subject is input to the shooting pattern selection unit 9 from the outside. The shooting pattern selection means 9 extracts the pattern of the tube voltage Vx from the start to the stop of the high voltage device based on the input shooting pattern information.
(Step 401)
In step 401, the tube voltage pattern extracted in step 400 is transmitted to the operation pattern determining means 456 inside the switching means 452. Then, the process proceeds to step 402.
(Step 402)
In step 402, the operation pattern determination means 456 determines whether or not the tube voltage Vx is switched based on the tube voltage Vx pattern transmitted from the imaging pattern selection means 9. If it is necessary to switch the tube voltage Vx (S401: YES), the process proceeds to step 404. If it is not necessary to switch the tube voltage (S401: NO), the process proceeds to step 403.
(Step 403)
In step 403, the operation pattern 1 determined by the operation pattern determination unit 456 is transmitted to the operation mode switching unit 455. When the transmission of the operation pattern is completed, the process proceeds to step 407.
(Step 404)
In step 404, the tube voltage switching period T and the determination value Tb are compared based on the pulse pattern of the tube voltage Vx transmitted from the imaging pattern selection means 9. As the determination value Tb, a value determined in advance based on the output voltage characteristics of the high-voltage device acquired in advance is used.
(Step 405)
If it is determined in step 404 that the tube voltage switching period T is longer than the determination value Tb (T> Tb) (S403: NO), the process proceeds to step 405. In step 405, the operation pattern 2 determined by the operation pattern determination unit 456 is transmitted to the operation mode switching unit 455. When the transmission of the operation pattern is completed, the process proceeds to step 407.
(Step 406)
If it is determined in step 404 that the tube voltage switching period T is T <Tb (S403: YES), the process proceeds to step 406. Here, the operation pattern 3 determined by the operation pattern determination unit 456 is transmitted to the operation mode switching unit 455. When the transmission of the operation pattern is completed, the process proceeds to step 407.
(Step 407)
In step 407, it is detected that an operation pattern has been transmitted to the operation mode switching means 455, and an operation mode at the time of activation is set based on the designated operation pattern.
(Step 408)
When the setting of the operation mode is completed in step 407, the operation of the high voltage device is started.

As described above, in the present embodiment, the operation pattern of the high voltage device is set based on the information of the preset shooting pattern.

Hereinafter, the operation patterns 1 to 3 of the high voltage device of FIG. 10 will be described with reference to FIGS. The operation pattern 1 is an example of the operation of the high voltage device in the general imaging mode in which imaging is performed with the tube voltage being constant, and the operation pattern 2 and the operation pattern 3 are multi-energy imaging in which imaging is performed by switching a plurality of tube voltage values. 2 shows an example of the operation of a high voltage device in mode. Here, in the operation patterns 1 to 3, the constants of the resonance circuit 303 are the same.
(Operation pattern 1)
Here, the operation pattern 1 will be described with reference to FIG. An operation pattern 1 shows an operation pattern of the high voltage device when the tube voltage Vx1 during the photographing period is constant. In the operation pattern 1, the inverter 2 is operated in the N-fold resonance mode 54 in the period from the start of the high voltage device to the end of photographing (period from time 0 to time t42 in FIG. 12). When the predetermined shooting period ends at the timing of time t42, the inverter 2 enters a stop mode in which the switching operation is stopped, and continues until the tube voltage becomes zero. In this stop mode, since the switching operation of the inverter 2 is stopped, the falling period depends on the capacitances of the smoothing capacitors Cm1 and Cm2 of the rectifier circuit 304 and the time constant of the equivalent resistance value of the X-ray tube. In the N-fold resonance mode 54, the drive frequency fsw of the inverter 2 is set to 1 / N of the basic resonance mode 53. Therefore, the response speed of the tube voltage is lower than that in the basic resonance mode 53. However, since the switching loss of the inverter 2 can be suppressed, it can be said that it is suitable for long-term imaging with a constant tube voltage. In the operation pattern 1 of the present embodiment, the entire period from the start to the end of imaging is operated in the N-fold resonance mode 54, but the present invention is not limited to this. For example, the inverter 2 may be operated in the basic resonance mode 53 when it is necessary to rapidly increase the tube voltage, such as when the tube voltage sharply decreases during imaging due to abnormal discharge of the X-ray tube.
(Operation pattern 2)
Here, the operation pattern 2 will be described with reference to FIG. The operation pattern 2 shows the operation of the high voltage device when the tube voltage is switched during the photographing period. In the operation pattern 2, basically, the tube voltage rising period (time t0 to t51 in FIG. 13 and time t55 to 56) is operated in the basic resonance mode 53, and the steady period (time t51 in FIG. 13). To t53, time t54 to t55, time t56 to t58, and time t59 to t60) in the N-fold resonance mode 54. During the falling period of the tube voltage (periods t53 to t54, times t58 to t59, and times t60 to 61 in FIG. 13), the inverter 2 is set to the stop mode. In the operation pattern 2, the inverter 2 is operated in the basic resonance mode 53 only during the rising period of the tube voltage. For this reason, compared with the operation pattern 1, the rise of the tube voltage can be speeded up. Further, the switching loss can be suppressed by operating the inverter 2 in the N-fold resonance mode during the steady period. As described above, the operation pattern 2 is an operation pattern in which both the rise of the tube voltage is accelerated and the loss of the inverter is reduced, and it can be said that the operation pattern 2 is suitable for an imaging mode in which the tube voltage is switched at a relatively long cycle.
(Operation pattern 3)
The operation pattern 3 will be described with reference to FIG. The operation pattern 3 shows the operation of the high-voltage device when the tube voltage is switched during the photographing period as in the operation pattern 2. In the operation pattern 3, compared with the operation pattern 2, the tube voltage switching width ΔVx14 is larger (ΔVx14> ΔVx13), and the tube voltage switching period Tm43 is shorter (Tm43 <Tm42). For this reason, the operation pattern 3 requires a faster rise in tube voltage than the operation pattern 2. Therefore, in the operation pattern 3 in FIG. 14, the tube voltage rise period (time t600 to t601 and time t604 to t605 in FIG. 14) and steady period (time t601 to t602, time t603 to t604 in FIG. During the period from time t605 to t606 and from time t607 to 608), the inverter 2 is operated in the basic resonance mode 53 that can increase the response speed of the tube voltage compared to the N-fold resonance mode 54. The tube voltage falling period (time t602 to t603 and time t606 to 607 in FIG. 14) is set to a stop mode in which the switching operation of the inverter 2 is stopped, similarly to the

operation patterns

1 and 2. In the operation pattern 3, since the inverter 2 in the rising period and the steady period is operated in the basic resonance mode 53, the switching loss increases. However, in order to periodically switch between the stop mode in which the switching operation of the inverter 2 is stopped during the photographing period and the operation period under the low tube voltage condition (periods from time t603 to t604 and time t607 to 608 in FIG. 14), It is considered that there is no problem that it becomes difficult to cool the switching element as compared with the operation mode 1 and the operation mode 2. Thus, it can be said that the operation pattern 3 is suitable for the imaging mode in which the switching range of the tube voltage is large and the tube voltage is switched at high speed in a short cycle.

As described above, in the present embodiment, the operation pattern of the high voltage device suitable for the set load condition can be selected by switching the operation mode of the inverter based on the preset load condition. As a result, it is possible to provide a high voltage device that can cope with various load patterns such as a load pattern that outputs a constant voltage for a long period of time and a load pattern that switches the output voltage at high speed in a short cycle. In the present embodiment, the constants of the resonance circuit 303 are the same in the basic resonance mode 53 and the N-fold resonance mode 54, but different constants may be used in the basic resonance mode 53 and the N-fold resonance mode 54. For example, a switch and a capacitor may be connected in parallel with the series resonance capacitor Cs, and the resonance circuit may be changed by switching the switch on / off depending on the operation mode of the inverter 2.

As mentioned above, although embodiment of this invention was described, this invention is not limited to these. For example, in all the embodiments, the high voltage device configured with one inverter and the rectifier circuit has been described. However, the present invention can be applied even to a high voltage device including two or more inverters and a rectifier circuit, for example. Is possible. In all the embodiments, the present invention can also be applied to a DC power supply as an output of an AC-DC converter or a DC-DC converter.

The high voltage device of the present invention can be applied to a power supply device that supplies a high DC voltage to a load, such as an X-ray diagnostic imaging device or a vacuum deposition electron gun.

DESCRIPTION OF SYMBOLS 1 ... Power supply, 2 ... Inverter, 3, 3, 203, 303 ... Resonance circuit, 4, 204, 304, Rectifier circuit, 5, 205, 305, 405 ... Control means, 6 ... Voltage detection means, 7 ... X-ray tube, 8 ... Current detection means, 9 ... Imaging pattern selection means, 51 ... Gate signal generation means, 52, 452 ... Switching means, 53 ..Basic resonance mode, 54 ... N-fold resonance mode, 455 ... operation mode switching means, 456 ... operation pattern determination means, Q1 to Q4 ... switching elements, D1 to D4 ... diodes, Dr1 to Dr4, Dr11 to Dr18 ... rectifier diode, Lr ... series resonant inductor, N1, N11 ... primary winding, N2, N21, N22 ... secondary winding, T1, T2 ... Core, Cm, Cm1, Cm2, And smoothing capacitor, Cp, Cp1, Cp2 ··· parallel resonant capacitor, Cs ··· series resonant capacitor, Cd1 ~ Cd4 ··· rectification capacitor

Claims

A resonant circuit;
An inverter connected between a DC power source and the resonance circuit and converting a DC voltage into an AC voltage;
A rectifier circuit connected between the resonant circuit and a load, rectifying the AC voltage, and supplying a DC voltage to the load;
In a high voltage device comprising a control means for controlling the inverter,
The control means includes
A first mode that operates so that a frequency of a resonance current supplied from the inverter to the resonance circuit is substantially equal to a drive frequency of the inverter;
A second mode in which a frequency of a resonance current supplied from the inverter to the resonance circuit is (natural number + 1) times a drive frequency of the inverter;
A high voltage apparatus comprising: switching means for switching between the first mode and the second mode.
The high voltage device according to claim 1,
The control means operates in the first mode until the output voltage output from the rectifier circuit and supplied to the load reaches a predetermined value, and the output voltage reaches the predetermined value. In the subsequent period, the switching means is controlled to operate in the second mode.
The high voltage device according to claim 2,
An output voltage detecting means for detecting the output voltage;
The high-voltage device, wherein the switching unit switches between the first mode and the second mode based on a voltage value detected by the output voltage detection unit.
The high voltage device according to claim 1,
The inverter is composed of at least one switching element,
The high voltage apparatus, wherein the switching unit switches the first operation mode and the second operation mode at a timing at which the switching element is turned on or off during a switching cycle.
The high voltage device according to claim 1,
The switching means switches between the first mode and the second mode based on a predetermined output voltage pattern of the rectifier circuit.
The high voltage device according to claim 5,
The control means includes
When the output voltage is switched to a plurality of values to operate, the inverter operates in the first mode,
When operating with the output voltage being substantially constant, the inverter operates in the second mode.
The high voltage device according to claim 1,
The high-voltage device according to claim 1, wherein a frequency of the resonance current in the first mode is substantially equal to a frequency of the resonance current in the second mode.
The high voltage device according to claim 1,
Current detection means for detecting the resonance current output from the inverter;
The high voltage device according to claim 1, wherein the current detection means detects a zero cross point of the resonance current.
The high voltage device according to claim 1,
The high voltage device according to claim 1, wherein a driving frequency of the inverter changes in the first operation mode or the second operation mode.
The high voltage device according to claim 1,
The resonance circuit includes a transformer, a series resonance inductor connected in series to the primary winding of the transformer, and a parallel resonance capacitor connected in parallel to both ends of the secondary winding of the transformer. High voltage device to do.
The high voltage device according to claim 1,
The resonant circuit includes a transformer, a series resonant capacitor and a series resonant inductor connected in series with a primary winding of the transformer, and a parallel resonant capacitor connected in parallel between terminals of the secondary winding of the transformer. A high voltage device characterized by that.
The high voltage device according to claim 1,
The rectifier circuit is a cockcroft circuit.
The high voltage device according to claim 1,
The rectifier circuit is a voltage doubler rectifier circuit.
The high voltage device according to claim 1,
The high voltage apparatus according to claim 1, wherein the load is an X-ray tube.