JP4497640B2 - High voltage switch circuit and X-ray apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply device for X-ray generation for medical or industrial use, and when the emission of X-rays from the X-ray tube is stopped, the electric charge of a capacitor connected in parallel with the X-ray tube is suddenly discharged. The present invention relates to a technique for miniaturizing a high voltage switch circuit for dropping a voltage between an anode and a cathode of an X-ray tube (hereinafter referred to as tube voltage) at high speed, and an X-ray apparatus using the same.
[0002]
[Prior art]
Conventionally, an apparatus for controlling the tube voltage of an X-ray high voltage apparatus at high speed has been developed. In these X-ray high-voltage devices, the AC high-voltage output of a high-voltage transformer is usually rectified by a high-voltage rectifier, and this is added to the high-voltage side, the floating capacitance of a high-voltage cable, etc. The DC high voltage is applied to the X-ray tube after smoothing with the capacitor.
[0003]
In this case, since there is a high voltage rectifier, the discharge of the electric charge stored in the capacitor has only a route via the X-ray tube, so it is relatively easy to start up the tube voltage at a high speed. There is a technical problem that it is difficult to descend the vehicle at high speed.
[0004]
For this reason, high-speed pulsed tube voltage is required, such as cine imaging that captures blood flow in blood vessels on a cine film, and pulse fluoroscopy to obtain high-quality real-time images when operating a catheter in a blood vessel. In the X-ray high voltage apparatus, the waveform when the tube voltage drops (hereinafter referred to as the wave tail) becomes a problem. In other words, this wave tail has little effect on X-ray images formed on X-ray films and X-ray televisions, and in addition, a large amount of low-energy X-rays that are likely to be harmful exposure to the subject from the X-ray tube. Will be emitted. This is an ineffective exposure especially for medical practices under high-quality fluoroscopy represented by interventional radiology.
[0005]
Further, during the wave tail period of the tube voltage, the electric power stored in the capacitor in the X-ray tube is consumed, so that the internal temperature of the X-ray tube is increased by that amount, and the life of the tube is shortened. Problems such as restricting the allowable X-ray conditions after line output occur.
[0006]
As a method for solving such a problem, Japanese Patent Application Laid-Open No. 51-6689 discloses a method of shortening the wave tail by short-circuiting the anode and the cathode using a tetrode (quadrupole vacuum tube). However, with this method, the tetrode is large, which prevents the miniaturization of the X-ray high-voltage device. Also, the tetrode itself is expensive and is a consumable part, so it needs to be replaced regularly. It is disadvantageous. Therefore, as a method to solve these problems, a series connection body of a current limiting impedance and a high voltage switch is provided between the anode and cathode of the X-ray tube, and the charge accumulated in the capacitor on the high voltage side is discharged at high speed. This method is disclosed in JP-A-8-212948. In this method, a plurality of power semiconductor switching elements are connected in series, and a series connection circuit of a high-voltage switch for sequentially switching these switching elements and a current-limiting impedance is connected in parallel with the capacitor, and X-ray radiation is performed. When stopping, the high voltage switch is switched to rapidly discharge the electric charge accumulated in the capacitor, thereby lowering the tube voltage at a high speed.
[0007]
[Problems to be solved by the invention]
However, when the high voltage switch circuit disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-212948 is mounted and put into practical use in combination with an X-ray high voltage device, the high voltage switch circuit is very large in the conventional method. Will be. That is, in order to withstand the high voltage charged in the capacitor, the high-voltage switch circuit must connect a plurality of power semiconductor switching elements having a withstand voltage per element of several hundred volts or more in series. For example, if a MOSFET (Metal OXid Silicon Field Effect Transistor) with a withstand voltage of 1500 V is used as a power semiconductor switching element, an X-ray device with a maximum tube voltage of 150 kV has practically considered a 20% margin. Must withstand 180kV. In this case, when the voltage applied to the MOSFETs connected in series is set to 1000 V per element, at least 180 elements need to be connected in series in order to withstand the 180 kV. When the high voltage switch circuit having such a configuration is used by being connected to an X-ray apparatus, the 180 elements are generally mounted on a printed board, but are connected to the X-ray high voltage apparatus. High voltage switch circuits, unlike switch circuits in other fields, have the problem of high voltage insulation. For example, in order to meet the standard of 110V / mm, which is the standard of medical equipment UL2601-1 (Safety Problem Study Group (UL Study Group): May 1996; P140, Table 16), the insulation distance between elements is If this is about 9 mm and this is applied between the vertical and horizontal lines of 180 elements and between wiring patterns, the printed circuit board becomes large and impractical. In this case, it is conceivable to shorten the insulation distance by providing a slit or the like on the printed circuit board, but it becomes weak against bending and bending, and it is possible to ensure reliability such as breakage of the printed circuit board and disconnection of the signal line. It becomes difficult.
[0008]
In addition, there is a method of dividing the printed circuit board to reduce the area per printed circuit board, dividing the 180 elements into a number corresponding to the divided printed circuit board, and mounting these 180 elements on the printed circuit board. In this case as well, in order to withstand the above-mentioned high voltage, it is necessary to secure a sufficient insulation distance between the divided printed circuit boards. Therefore, the distance between the printed circuit boards and the semiconductor elements mounted between these printed circuit boards The distance of the wiring connecting is increased. As described above, the above-described method of dividing the printed circuit board also increases the size of the high-voltage switch circuit and increases the length of the signal line for driving the serially connected semiconductor elements. There is concern about malfunction.
[0009]
As described above, in order to obtain a high-speed pulsed tube voltage such as cine imaging and pulse fluoroscopy, the large high-voltage switch circuit is used in combination with an X-ray high-voltage device. The X-ray apparatus is very large. In particular, the X-ray high voltage device is very small due to the adoption of the inverter type, and the X-ray device combining this and the above high voltage switch circuit becomes large, and the inverter type X-ray high voltage device. The advantage of downsizing, which is one of the features, is lost.
[0010]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a high-voltage switch circuit constituted by connecting in series a highly reliable power semiconductor switching element that is downsized and does not malfunction, and uses the high-voltage switch circuit for an X-ray high-voltage device. An object of the present invention is to provide an X-ray apparatus capable of reducing exposure by reducing the tube voltage at a high speed and adapting to a technique such as pulse fluoroscopy.
[0011]
[Means for Solving the Problems]
The above object is achieved by the following means.
[0012]
(1) It is provided with a series connection body of a plurality of power semiconductor switching elements, and a conduction control means for controlling conduction of the power semiconductor switching elements of the series connection body. In a high-voltage switch circuit that performs a switching operation by conducting a semiconductor switching element for a power supply, the series connection body includes a connection body in which a plurality of divided series connection bodies are connected in series, and the power semiconductors of these divided series connection bodies A switching element and a circuit for controlling conduction thereof are divided and mounted on a plurality of mounting means corresponding to the divided series connection body, and the plurality of mounting means are stacked.
[0013]
(2) The plurality of mounting means of (1) above are stacked by rotating 90 degrees or 180 degrees alternately up and down.
[0014]
(3) The terminals for connecting the plurality of mounting means in (2) in series are arranged at positions where the connection lines do not intersect.
[0015]
(4) A series connection body of a plurality of power semiconductor switching elements, and a conduction control means for controlling conduction of the power semiconductor switching elements of the series connection body, and a plurality of electric powers of the series connection body by the conduction control means. In a high-voltage switch circuit that performs a switching operation by conducting a semiconductor switching element for a power supply, the series connection body includes a connection body in which a plurality of divided series connection bodies are connected in series, and the power semiconductors of these divided series connection bodies A switching element and a circuit for controlling conduction thereof are divided and mounted on both surfaces of a plurality of mounting means corresponding to the divided series connection body, and an insulating material is sandwiched between the plurality of mounting means.
[0016]
(5) The mounting means of (4) above is stacked by rotating 90 degrees or 180 degrees alternately up and down.
[0017]
(6) The terminals for connecting the mounting means of (5) in series are arranged at the same position in both the upper and lower connection lines.
[0018]
(7) A series connection body of a plurality of power semiconductor switching elements, and conduction control means for controlling conduction of the power semiconductor switching elements of the series connection body. In a high-voltage switch circuit that performs a switching operation by conducting a semiconductor switching element for a power supply, the series connection body includes a connection body in which a plurality of divided series connection bodies are connected in series, and the power semiconductors of these divided series connection bodies A switching element and a circuit for controlling conduction thereof are alternately mounted and arranged on both the front and back surfaces of a plurality of mounting means corresponding to the divided series connection body, and stacked with an insulator interposed between the plurality of mounting means. To do.
[0019]
(8) The mounting means of (7) above is laminated by rotating 90 degrees or 180 degrees alternately up and down.
[0020]
(9) The terminals for connecting the plurality of mounting means in (8) in series are arranged such that the connection lines are in the same position both above and below.
[0021]
The high voltage switch circuit can be downsized by the means (1) to (9). The object of the present invention is achieved by the following means.
[0022]
(10) An AC voltage source, a high voltage transformer connected to the AC voltage source and boosted by the primary winding, and a boosted AC voltage connected to the secondary winding of the high voltage transformer In parallel with the capacitor of the X-ray high-voltage apparatus comprising a high-voltage rectifier for converting to a high voltage, a capacitor connected to the high-voltage rectifier and smoothing the DC high voltage, and an X-ray tube connected to the capacitor. The high voltage switch circuits (1) to (9) are connected through the current limiting impedance.
[0023]
With this configuration, the X-ray exposure due to low energy X-rays that do not contribute to X-ray photography can be reduced by causing the high-voltage switch circuit to perform a switching operation when X-ray emission is stopped to drastically lower the tube voltage.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing an example in which the high voltage switch circuit of the present invention is applied to an inverter type X-ray high voltage apparatus. 1 is a book for obtaining high-speed pulsed tube voltage, such as cine imaging for imaging blood flow in blood vessels on a cine film, and pulse fluoroscopy for obtaining high-quality real-time images when operating a catheter in a blood vessel. The wave tail cutting circuit by the high voltage switch circuit of the invention is connected in parallel with a capacitor on the high voltage side connected in parallel with the X-ray tube as will be described later.
[0025]
10 is a single-phase AC power source, 11 is a rectifier that is connected to the single-phase AC power source 10 and converts this AC voltage to DC, 12 is a capacitor that is connected to the rectifier 11 and smoothes this DC voltage, and 13 is connected to this capacitor 12 An inverter circuit that converts the smoothed DC voltage into an AC voltage having a high frequency (hereinafter abbreviated as a high frequency), 14 is connected to the inverter circuit 13 and is a high voltage transformer that boosts the high frequency AC voltage, and 15 is this high voltage A high-voltage rectifier connected to the secondary side of the voltage transformer 14 and rectifies the boosted AC voltage, 16 is a high-voltage capacitor connected to the high-voltage rectifier 15 and smoothes its output voltage. And a stray capacitance of a high voltage cable connecting the X-ray tube described below, and an additional capacitor for smoothing added as necessary, and is connected in parallel with the wave tail cutting circuit 1. 17 is an X-ray tube connected to the high voltage capacitor 16, 18 is a control circuit for instructing X-ray emission from the X-ray tube 17, and 19 is an X-ray emission signal output from the control circuit 18. . The wave tail cutting circuit 1 is provided with terminals 2a, 2b, 2c and 2d, which are connected to a high voltage rectifier 15 and a high voltage capacitor 16.
[0026]
FIG. 2 is a block diagram of the wave tail cutting circuit 1. The impedance 5 for limiting the current when discharging the charge of the high voltage capacitor 16 at the time of wave tail cutting of the tube voltage, and the high voltage connected in series with this impedance. Based on the X-ray radiation signal from the control circuit 18, the semiconductor switching element of the high-voltage switch circuit 6 is controlled to be conductive or non-conductive based on the pulse cutoff circuit unit 4 constituted by the switch circuit 6 and the diode 7. It comprises a drive control circuit unit 3 for generating a drive signal, and the wave tail cutting circuit 1 is provided with terminals 2a and 2c at one end, terminals 2b and 2d at the other end, and the terminals 2a and 2b. Is connected to the DC high voltage side of the high voltage rectifier 15 and terminals 2c and 2d are connected to both ends of the high voltage capacitor 16.
[0027]
FIG. 3 shows an example of a specific circuit of the high voltage switch circuit 6 shown in FIG. This high voltage switch circuit 6 uses MOS field effect transistor MOSFETs (Metal OXid Silicon Field Effect Transistors) as switching elements, and these switching elements Q1 to Qn are connected in series, and the first element Q1 of this series connection is connected. From this (hereinafter, this element is referred to as the lowermost element) to the final element Qn (hereinafter, this element is referred to as the uppermost element) is sequentially conducted to have a function as a high voltage switch.
[0028]
Each element Q1 to Qn has a series connection body composed of a capacitor C (C1 to Cn), a resistor Rg (Rg1 to Rgn), a hysteresis element, and a Zener diode 21 in this case, for sequentially conducting these elements. And the cathode of the element preceding this element. In the uppermost element Qn, a series connection body composed of the capacitor Cn, the resistor Rgn, and the hysteresis element 21 is connected in parallel between the anode and the cathode, and the anode is connected to the cathode of the diode 7 shown in FIG. Zener diodes ZD1 to ZDn for preventing overvoltage are connected between the gate and cathode of each element Q1 to Qn, and connected in parallel to each element to balance the voltage sharing when each element Q1 to Qn is non-conductive. The resistance to be omitted is omitted. Further, the + (plus) terminal is connected to the cathode of the diode 7 in FIG. 2, the − (minus) terminal is connected to the connection point between the terminals 2b and 2d and the high voltage switch 6 in FIG. The drive signal from the drive control circuit 3 is inputted, and the X-ray radiation signal from the control circuit 18 is inputted to the drive control circuit 3 for generating the drive signal, and the element Q1 is turned on when the X-ray exposure is stopped. Then, a signal for conducting the elements after Q1 sequentially is generated. The diode 7 in series with the switching elements Q1 to Qn is for preventing the switching element from malfunctioning even if the tube voltage drops rapidly during fluoroscopy or photographing, but this diode 7 alone is not sufficient. Therefore, a Zener diode 21 having hysteresis characteristics is further provided in series with the gates of the switching elements Q1 to Qn, and the switching elements Q1 to Qn are switched when the gate voltage of the Q1 to Qn becomes a certain voltage or more. It is made to conduct so that it can be reliably operated without malfunction even when the tube voltage suddenly drops. Next, the operation of the circuits of FIGS. 1 to 3 configured as described above will be described.
[0029]
When an X-ray emission stop signal is output from the control circuit 18, the drive control circuit 3 generates a drive voltage for conducting the high voltage switch, and this drive voltage is applied to the gate of the element Q1 at the lowest stage of the MOSFET series connection body. Applied between sources. When a drive voltage is applied, Q1 becomes conductive, and the voltage charged in the capacitor C1 is charged to the gate of the next-stage element Q2 via the resistor Rg1 and the Zener diode 21 as a hysteresis element. At this time, the voltage of the gate of Q2 is not charged until the Zener voltage of the Zener diode 21 exceeds the Zener voltage by the action of the Zener diode 21.
[0030]
Q2 conducts when the gate voltage of Q2 reaches a voltage sufficient to conduct Q2. In this way, the conduction from Q3 to the uppermost element Qn is sequentially performed, and the switching operation of the high voltage switch is completed. The charge of the high voltage capacitor 16 is suddenly discharged through the current impedance 5, and the tube voltage is suddenly lowered. Cut the high voltage wave tail. When the tube voltage is applied to the pulse cutoff circuit 4, the capacitors C1 to Cn are charged with 1 / n of the tube voltage. When the tube voltage drops rapidly, the voltage across the high voltage switch becomes higher than the tube voltage by the drop voltage. A voltage corresponding to 1 / n of the voltage is an extra voltage for C1 to Cn. Due to this voltage difference, a current flows in the charging direction as described above, but no current flows through the gate until the Zener voltage of the Zener diode 21 is reached. For this reason, even when the tube voltage drops rapidly and the diode 7 performs reverse recovery operation, the gate voltage can be prevented from rising and the MOSFET can be operated normally. In this operation, the time until the Zener voltage is reached is a dead zone, and therefore the operation at the positive voltage and the negative voltage has a hysteresis characteristic, and this hysteresis characteristic is determined by the Zener voltage of the Zener diode 21. The Zener voltage of the Zener diode 21 that determines this hysteresis characteristic may be arbitrarily determined according to the fluctuation rate of the tube voltage. The high voltage switch circuit 6 having the above configuration is generally mounted on a printed circuit board. However, the high voltage switch circuit 6 has a problem of high voltage insulation unlike switch circuits in other fields. Therefore, the insulation method in which a predetermined distance is provided between elements as in the case of the switch circuit in the other field increases the size and is not practical.
[0031]
Therefore, in the present invention, the switching elements Q1 to Qn of the high voltage switch circuit 6 and the electric components (capacitors C1 to Cn, resistors Rg1 to Rgn, Zener diode 21, ZD1 to ZDn, etc.) for driving them are divided. The printed circuit board is mounted on a printed board, and the divided printed circuit boards themselves are used as insulators. By alternately laminating the printed base plates, the insulation distance is shortened and the size is reduced.
[0032]
4A and 4B show a first embodiment of the present invention of a high voltage switch circuit 6 using this method. FIG. 4A is a front view and FIG. 4B is a side view.
[0033]
In Fig. 4 (a), the printed circuit board is made of alumina ceramic, which has a high dielectric strength and is thin, and one printed circuit board is equipped with four MOSFETs, and these MOSFETs rotate counterclockwise. They are arranged sequentially.
[0034]
Connect the positive (+) terminal of the output terminal of the drive signal output from the drive control circuit 3 to the G1 terminal at the lower right of the first printed circuit board, and connect it to the S1 terminal at the upper right of the first printed circuit board. Connects the minus (−) terminal of the output terminal of the drive signal output from the drive control circuit 3, and inputs the drive signal from the drive control circuit 3 to the gate of the MOSFET (Q1).
[0035]
The drain terminal of the MOSFET (Q1) is connected to the source terminal of the MOSFET (Q2), and in this way, it is sequentially connected up to the fourth-stage MOSFET (Q4). The drain terminal of the fourth-stage MOSFET (Q4) is connected to the lower left D4 terminal of the first printed circuit board, which is connected to the lower left S5 terminal of the second printed circuit board, and the source terminal of the MOSFET (Q5) Connect to (S5). The G5 terminal at the upper left of the first printed circuit board is connected to the G5 terminal at the upper left of the second printed circuit board, and is connected to the gate terminal of the MOSFET (Q5) on the second printed circuit board. The second printed circuit board is connected in the same manner as the first printed circuit board, and is connected to the third printed circuit board by such a method until the nth printed circuit board is connected. Here, the first to n-th printed circuit boards are laminated by rotating the same printed circuit board by 180 degrees. In addition, the terminals (D4 and S5, G5 and G5) for connecting each printed circuit board are placed at the same position so that the connection lines to which high voltage is applied do not cross each other. The distance between the copper wires, that is, the printed circuit boards, is selected so as to be the shortest distance in consideration of the height of the electric components mounted on the printed circuit board and the insulation distance. FIG. 4B shows a high-voltage switch circuit mounted in this manner. This circuit further increases insulation and strength by taking a method such as molding with resin and reinforcement with insulating paper. Increased benefits in implementation.
[0036]
FIG. 5 shows a second embodiment of the present invention showing the arrangement of MOSFETs on the printed circuit board of the high voltage switch circuit 6 and the method for connecting the printed circuit boards.
[0037]
The material of the printed circuit board, the number of mounted MOSFETs, and the arrangement are the same as in the first embodiment.
[0038]
Here, when the printed circuit board is square, the positive terminal (+) of the drive signal is connected to the G1 terminal on the front of the first printed circuit board, and the negative (-) terminal is the front of the first printed circuit board. The drive signal is input between the gate and source of the MOSFET (Q1).
[0039]
The drain terminal of the MOSFET (Q1) is connected to the source terminal of the MOSFET (Q2), and the MOSFET (Q4) in the fourth stage is sequentially connected by this method. The drain terminal of the fourth-stage MOSFET (Q4) is connected to the D4 terminal on the lower left side of the first printed circuit board and to the S5 terminal on the lower left side of the second printed circuit board. The source terminal of the MOSFET (Q4) is connected to the G5 terminal at the left center of the first printed circuit board, and this terminal is connected to the G5 terminal at the left center of the second printed circuit board. The driving signal from the MOSFET (Q4) is input between the gate and source of the MOSFET (Q5). Connect the MOSFETs (Q5) to (Q8) in the second printed circuit board in the same way as the first one. The drain terminal of the MOSFET (Q8) is connected to the D8 terminal on the left side of the rear side of the second printed circuit board. This terminal is connected to the source terminal (S9) of the MOSFET (Q9) via the S9 terminal on the left side of the rear part of the third printed circuit board (not shown).
[0040]
The G9 terminal on the rear center side of the second printed circuit board is connected to the G9 terminal on the rear center side of the third printed circuit board (not shown), and this terminal is connected to the MOSFET (Q9) gate terminal of the third printed circuit board. Are connected, and the drive signal from the MOSFET (Q8) is input between the MOSFET (Q9) gate and source of the third printed circuit board. In this way, the MOSFETs and the electrical components of the circuit that drives them are sequentially connected up to the nth sheet. Here, the first to n-th printed circuit boards are each rotated by 90 degrees and stacked.
[0041]
Also, the terminals for connecting each printed circuit board (D4 and S5, G5 and G5 in the case of the first and second printed circuit boards) are located at the same position so that the connection lines to which high voltage is applied do not intersect In order to connect the printed circuit boards, high-strength copper wires are used, and the length is selected in consideration of the height of the electrical components mounted on the printed circuit boards and the insulation distance. In the second embodiment, since the connection lines between the printed circuit boards are wired on the four surfaces of the laminated printed circuit boards, the strength is higher than that of the first embodiment.
[0042]
FIG. 6 is a third embodiment of the present invention showing the arrangement of MOSFETs on the printed circuit board of the high voltage switch circuit 6 and the method of connection between the printed circuit boards.
[0043]
MOSFETs (Q1 to Qn) and electrical components for driving them (capacitors C1 to Cn, resistors Rg1 to Rgn, Zener diode 21, ZD1 to ZDn, etc.) are mounted and arranged on both sides of the printed circuit board 8, and each printed circuit board Each MOSFET and electrical component are connected to the front and back surfaces of the board, respectively, and the uppermost MOSFET and electrical components on the front side are connected to the bottom MOSFET and electrical components on the back side to form a series-connected high-voltage switch circuit. To do. Then, the plurality of divided printed boards are rotated by 180 degrees and stacked. The terminals connecting the printed circuit boards are rotated by 180 degrees, and both printed circuit boards need to be in the same position. When laminating by such a method, an insulating material 9 such as insulating paper, resin, or ceramic is sandwiched between the printed boards so as to ensure a predetermined withstand voltage.
[0044]
It is to be noted that the same effect can be obtained even if each printed circuit board is rotated 90 degrees and laminated as in the second embodiment of the present invention shown in FIG. Also in this case, the terminals for connecting the printed boards need to be in the same position.
[0045]
FIG. 7 shows a fourth embodiment of the present invention showing the arrangement of MOSFETs on the printed circuit board of the high voltage switch circuit 6 and the method for connecting the printed circuit boards.
[0046]
MOSFETs (Q1 to Qn) and electrical components for driving them (capacitors C1 to Cn, resistors Rg1 to Rgn, Zener diode 21, ZD1 to ZDn, etc.) are mounted and arranged on both sides of the printed circuit board 8, and these MOSFETs And electrical parts are connected alternately on the front and back sides.
[0047]
The connection between printed circuit boards, that is, the connection between the lower printed circuit board and the upper printed circuit board is connected to the terminal to which the MOSFET and the electrical component are connected at the closest distance between the upper and lower printed circuit boards. Connecting. In the embodiment of FIG. 7, the lowermost MOSFET (Q1) and the electrical components of the high voltage switch circuit 6 are connected to the lowermost printed circuit board 8. ₂ Therefore, the uppermost MOSFET (Q6) and electrical components arranged on the back surface of the printed circuit board are the printed circuit board 8. ₁ Upper printed circuit board 8 ₂ Connect to the bottom MOSFET (Q7) and electrical components placed on the surface of the. Then, the upper printed circuit board is rotated by 180 degrees and laminated with respect to the lower printed circuit board, and the terminals connecting these printed circuit boards are arranged so that the printed circuit boards are in the same position even when rotated by 180 degrees. To do. Furthermore, when laminating, insulation is performed so that a predetermined withstand voltage can be secured by sandwiching an insulating material 9 such as insulating paper, resin, or ceramic between the printed boards. By such a method, MOSFETs and electrical components are connected in series to form a high-voltage switch circuit, so that the potential difference between each MOSFET and electrical components is reduced, and insulation that is advantageous for miniaturization can be achieved.
[0048]
Each printed board can be rotated 90 degrees as in the second embodiment of the present invention, and the same effect can be obtained even when stacked. In this case, it is necessary that the terminals connecting the printed circuit boards have the same position between the printed circuit boards.
[0049]
FIG. 8 shows a fifth embodiment in which the high voltage switch circuit of each of the above embodiments according to the present invention is divided into two sets and connected in parallel between the anode and the earth of the X-ray tube 17 shown in FIG. is there. Also in this embodiment, the same effects as those in the above embodiments can be obtained.
[0050]
【The invention's effect】
As described above, according to the present invention, in a high-voltage switch circuit constituted by a plurality of power semiconductor switching elements and a series connection body for driving the power semiconductor switching elements, the series connection body is divided into a plurality of layers and stacked in series. Since it is configured to be connected, the high voltage switch circuit can be made very small as compared with the conventional non-stacked method, and a highly reliable high voltage switch circuit that does not malfunction can be provided. Then, by using this high voltage switch circuit for an X-ray high voltage device, the tube voltage is lowered at a high speed (cutting off the wave tail of the tube voltage), which is harmful to the subject who does not contribute to the X-ray image. There is an effect that it is possible to contribute to the reduction in size and the high reliability of an X-ray apparatus having functions such as pulse exposure using the wave tail cutting circuit.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example in which a high voltage switch circuit of the present invention is applied to an inverter type X-ray high voltage device.
FIG. 2 is a configuration diagram of the wave tail cutting circuit of FIG. 1;
3 is an example of a specific circuit diagram of the high voltage switch circuit of FIG. 2;
FIG. 4 is a first embodiment of the present invention showing mounting of a printed circuit board of a high voltage switch circuit.
FIG. 5 is a diagram of a second embodiment of the present invention showing mounting of a printed circuit board of a high voltage switch circuit.
FIG. 6 is a diagram of a third embodiment of the present invention showing mounting of a printed circuit board of a high voltage switch circuit.
FIG. 7 is a diagram of a fourth embodiment of the present invention showing mounting of a printed circuit board of a high voltage switch circuit.
FIG. 8 is a diagram of a fifth embodiment in which the high voltage switch circuit of each embodiment of the present invention is divided into two sets and these are connected in parallel between the anode and the earth of the X-ray tube and to the earth and the cathode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Wave tail cutting circuit, 2a, 2c Anode side terminal, 2b, 2d Cathode side terminal, 3 Drive control circuit, 4 Pulse interruption circuit, 5 Current limiting impedance, 6 High voltage switch circuit 7 Diode 8 Printed board 9 Insulator 10 AC Power supply, 11 Rectifier, 12 First capacitor, 13 Inverter circuit, 14 High voltage transformer, 15 High voltage rectifier, 16 High voltage capacitor, 17 X-ray tube, 18 Control circuit, 19 X-ray exposure signal, 21 Zener diode Q1-Qn Power semiconductor switching element, C1-Cn capacitor, Rg1-Rgn resistance, ZD1-ZDn Zener diode

Claims (2)

A series connection body of a plurality of power semiconductor switching elements, and conduction control means for controlling conduction of the power semiconductor switching elements of the series connection body, the plurality of power semiconductor switching of the series connection body by the conduction control means In the high-voltage switch circuit that performs switching operation by conducting the element, the series connection body includes a connection body in which a plurality of divided series connection bodies are connected in series, and the power semiconductor switching elements of these divided series connection bodies are The terminals of the two power semiconductor switching elements, which are arranged on the printed circuit board in a fixed circulation direction and are the endmost parts of the divided series connection body, are respectively arranged in the vicinity of the 90 degrees different sides of the printed circuit board. In addition, the printed circuit boards are sequentially rotated by 90 degrees and stacked, and the divided series connection bodies on the adjacent printed circuit boards are connected to each other with a high-strength conductive portion. High voltage switch circuit, characterized in that it comprises the series connection connected in series through. An AC voltage source , a high voltage transformer connected to the AC voltage source with a primary winding to boost the voltage, and a boosted AC voltage connected to the secondary winding of the high voltage transformer to a DC high voltage a high voltage rectifier which converts the capacitor for this is connected to the high voltage rectifier smoothing the high DC voltage, current limiting in parallel with the capacitor of the X-ray high voltage apparatus comprising a connected X-ray tube to the condenser An X-ray apparatus comprising the high-voltage switch circuit according to claim 1 connected through an impedance.

Images