JP5216270B2 - High voltage switch control circuit and X-ray apparatus using the same - Google Patents

Description

  The present invention relates to a high voltage switch control circuit equipped with a technology for improving a function of suppressing a steep voltage change at the time of turn-off of a power semiconductor switching element, and an X-ray apparatus using the same.

  In recent years, a flat panel detector (referred to as “FPD”) made of a semiconductor material is often used as an X-ray detector of an X-ray apparatus. FPD requires a readout period for reading out X-ray detection data after X-ray exposure. In order to ensure the reading period of the X-ray detection data, an X-ray irradiation method called pulse X-ray that intermittently irradiates X-rays from the X-ray source is adopted. In the pulse X-ray irradiation method, the waveform of the voltage of the high voltage power source (referred to as “tube voltage”) supplied to the X-ray source is pulsed.

By the way, with pulsed X-rays, the voltage supply to the X-ray source is not completely cut off for a while even after switching from the X-ray irradiation state to the stop state, and continues to emit low-energy X-rays. It is known that a phenomenon called “Namio” occurs. There is a concern that the prolonged “wave tail” phenomenon may be affected by ineffective exposure to the subject and image quality degradation of the X-ray image. Therefore, “wave tail blocking” of the X-ray source is adopted as a technique for blocking the wave tail as early as possible. An example of the wave tail blocking technique is disclosed in Patent Document 1.
In the disclosed technique, the conduction of the semiconductor switching element for power series connection is provided with a heat scan Hysteresis characteristic unit such that above a predetermined value, thereby preventing the fine erroneous discharge, such as operation in the X-ray tube.

Japanese Patent Laid-Open No. 2001-284095

  The above disclosed technique still has an unresolved problem that a stable circuit operation cannot be performed even under various voltage conditions such as a sudden voltage change.

  An object of the present invention is to provide a high voltage switch control circuit capable of stable circuit operation even under various voltage conditions and an X-ray apparatus using the same.

In order to achieve the above object, a high-voltage switch control circuit according to the present invention includes a plurality of semiconductor switches connected in series, connected in series, and a control terminal of the semiconductor switch, and one end of the semiconductor switch is connected. A first resistor connected between the other end of the other semiconductor switch, a first capacitor, a diode connected in parallel to the first resistor, and a parallel to the first capacitor. A high-voltage switch control circuit comprising: a second resistor connected to the control circuit; and a control circuit that controls conduction of the remaining semiconductor switch by controlling conduction of one of the plurality of semiconductor switches. And a third resistor connected in parallel to all of the plurality of semiconductor switches, and a second capacitor, and a discharge time constant of the first capacitor As remote discharge time constant of the second capacitor is increased, and sets at least one of the capacitance of the second capacitor, or the third resistance value of the resistor.

The X-ray apparatus of the present invention is connected to a single-phase AC power source and converts an AC voltage into a DC voltage, an inverter that converts the converted DC voltage into a high-frequency AC voltage, and the converted high-frequency AC. A high-voltage transformer that boosts the voltage; a high-voltage rectifier that converts the boosted high-frequency AC high voltage to a DC high voltage; an X-ray tube to which the converted DC high voltage is supplied; and the high-voltage rectifier In the X-ray apparatus, the high-voltage switch includes: a wave-tail cutoff unit connected in parallel to the X-ray tube; The means is the high voltage switch control circuit.

  According to the present invention, it is possible to provide a high voltage switch control circuit capable of stable circuit operation even under various voltage conditions and an X-ray apparatus using the same.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment of the invention, and the repetitive description thereof is omitted.

FIG. 1 is a diagram showing a configuration example of an X-ray apparatus common to each embodiment of the present invention.
As shown in FIG. 1, the X-ray apparatus of the present invention is composed of the following components. The rectifier 11 is connected to the single-phase AC power supply 10 and converts a commercial AC voltage supplied from the single-phase AC power supply 10 into a DC voltage. The smoothing capacitor 12 is connected to the rectifier 11, removes the pulsating component contained in the DC voltage converted by the rectifier 11, and smoothes it. The inverter circuit 13 is connected to the smoothing capacitor 12 and converts the DC voltage smoothed by the smoothing capacitor 12 into a high-frequency AC voltage. The high voltage transformer 14 is connected to the inverter circuit 13 and boosts the high-frequency AC voltage converted by the inverter circuit 13. The high voltage rectifier 15 is connected to the high voltage transformer 14 and rectifies the high frequency AC voltage boosted by the high voltage transformer 14 to convert it into a DC high voltage. The high voltage capacitor 16 is connected to the high voltage rectifier 15 to remove and smooth the pulsation component contained in the DC high voltage converted by the high voltage rectifier 15. The X-ray tube device 17 is connected to the high voltage capacitor 16, supplied with a DC high voltage smoothed by the high voltage capacitor 16, and exposes X-rays. The control circuit 18 instructs the X-ray tube device 17 to perform X-ray exposure. Here, it is assumed that an X-ray exposure signal 19 which is an X-ray exposure command signal is output from the control circuit 18. The wave tail cutoff circuit 1 is connected in parallel to the high voltage capacitor 16, and cuts off the DC high voltage supplied to the X-ray tube device 17, that is, the wave tail.

{Embodiment 1}
FIG. 2 is a diagram illustrating the first embodiment as an example of the configuration of the wave tail cutoff circuit 1. FIG.
Here, the semiconductor switch is formed by connecting a plurality of MOS-FET (Metal Oxide SilicON Field Effect TranSiStor) switches in series. The switches connected in multiple stages are S (1) to S (n) (n is a positive integer). The switch S (1) is arranged on the most cathode (K) side, and a drive signal 5 is given between the gate and source of the switch S (1) to control conduction of the switch S (1). The switch S (2) is connected in series to the drain side of the switch S (1), the switch S (3) is connected in series to the drain side of the switch S (2), and the switch S (n) is Connected in series to the drain side of the switch S (n-1). The switches S (2) to S (n) are controlled so as to follow the operation of the switch S (1). Zener diodes Dza (2) to Dza (n) are connected between the sources and gates of the other switches S (2) to S (n−1) sequentially connected in series to the switch S (1).

The first current limiting means Rg (1) to Rg (n) have diodes Da (1) to Da (n) such that the anode (A) side is the gate side of the switches S (3) to S (n). ) Are connected in parallel. Balance resistors Rb (1) to Rb (n) are connected in parallel to the first capacitors Cb (1) to Cb (n) so that the voltage applied to each switch is divided. The diode DL is connected in series to the drain side of the switch S (n) and prevents reverse current. In this case, the discharge resistor RD is directly connected to the anode (A) side of the diode DL, and consumes the discharge current from the X-ray tube device 17.

  Between the drains and sources of the switches S (1) to S (n), the second capacitors Cs (1) to Cs (n) and the second current limiting means Rs (1) to Rs (n) A series circuit consisting of The electrical characteristics of elements such as S, Cb, CS, Rg, Rb, Da, and Dza, which are indicated by the same symbols, are almost the same.

  Next, the operation of the high voltage switch circuit 3 will be described. The switch S (1) is cut off when the drive signal 5 applied between its gate and source is not positive. Since the other switches S (2) to S (n) operate following the switch S (1), they are in the cut-off state similarly to the switch S (1).

  That is, since the switches S (1) to S (n) are all cut off, the high voltage switch circuit 3 is in the off state. When a voltage is applied between the anode (A) and the cathode (K), the high voltage switch circuit 3 in the off state divides the voltage applied by the balance resistors Rb (1) to Rb (n), The capacitors Cb (1) to Cb (n) are charged with voltages almost evenly. The switches S (1) to S (n) share the voltage almost equally.

  Next, when the drive signal 5 applied between the gate and source of the switch S (1) is positive, the switch S (1) starts to conduct. Due to this conduction start, the charge of the first capacitor Cb (1) is discharged through the first current limiting means Rg (1), the gate and source of the switch S (2), and the drain and source of S (1). Be started. When discharge of the second capacitor Cs (1) is started, discharge is started via the second current limiting means Rs (1) and the drain and source of the switch S (1). With this discharge start, a voltage sufficient to start conduction is applied to the switch S (2) between the gate and source of the switch S (2). By applying this voltage, the switch S (2) starts to conduct.

  Note that the voltage between the gate and source of the switch S (2) in the zener diode Dza (2) is suppressed to a predetermined value or less. The switches S (3) to S (n) are sequentially turned on similarly to the switch S (2), and the switches S (1) to S (n) are turned on.

  If the drive signal 5 applied between the gate and source of the switch S (1) is negative, the switch S (1) is cut off and no current flows. At this time, when a voltage is applied between the anode (A) and the cathode (K), current flows between the source and gate of the switch S (2), the diodes Da (1) to Da (n), and the first capacitor Cb ( 1) and the second current limiting means Rs (1) and the second capacitor Cs (1). When the electric charge stored between the gate and source of the switch S (2) is discharged, the switch S (2) is cut off. The switches S (3) to S (n) are sequentially cut off in the same manner as the switch S (2), and the switches S (1) to S (n) are turned off.

  Next, the fluctuation of the tube voltage and the cause of malfunction will be described with reference to FIG. FIG. 3 is an equivalent circuit in which the junction capacitance existing in the switch of FIG. 2 showing the first embodiment is replaced with a capacitor, and the leakage current is replaced with a resistor. Specifically, each switch has a junction capacitance between drain and source, Coss (1) to Coss (n), and even when each switch is off, the leakage current exists in the resistor Rdss ( 1) to Rdss (n) can be substituted.

  When the high voltage switch circuit 3 is in an off state and a stable voltage is supplied between the anode (A) and the cathode (K), the balance resistance Rb (1) is applied to the switches S (1) to S (n). ) To Rb (n). Due to the voltage dividing action of these balance resistors Rb (1) to Rb (n), the voltages are almost evenly applied to the respective first capacitors Cb (1) to Cb (n) and the switches S (1) to S (n). Be shared. At this time, the current flowing through the Zener diodes Dza (2) to Dza (n) is negatively applied in the forward direction of the Zener diodes Dza (2) to Dza (n) between the gates and sources of the switches S (2) to S (n). Is generated. This negative potential is equal to the voltage drop caused by the Zener diodes Dza (2) to Dza (n), and the cut-off state of the switches S (2) to S (n) is robust.

  In addition to the current when the tube voltage is stable even if the tube voltage is increased, the switch junction capacitances Coss (1) to Coss (n) and the first capacitors Cb (1) to Cb (n ) And charging current to the second capacitors Cs (1) to Cs (n) are only added. At this time, the shut-off state of the switches S (2) to S (n) does not change, so that the off state of the switches S (1) to S (n) can be maintained.

  However, when the voltage applied between the anode (A) and the cathode (K) changes in the negative direction and becomes lower than the voltage stored in the switches S (1) to S (n), The diode DL that prevents the reverse current is cut off, and no current flows. As a result, discharge starts from the CR circuit inside the switches S (1) to S (n). Here, the CR circuit means the first capacitors Cb (1) to Cb (n), the second capacitors Cs (1) to Cs (n) and the junction capacitance between the drain and source of each switch Coss (1) ~ Coss (n), balance resistance Rb (1) ~ Rb (n) and resistance Rdss (1) ~ Rdss (n) replaced with leakage current of each switch. Also, consider the case where the discharge time constant of Cb (1) to Cb (n) is longer than the discharge time constant of Coss (1) to Coss (n). In this case, the potential of Cb (1) to Cb (n) is larger than the potential of Coss (1) to Coss (n), and the potential of the difference is the gate and source of the switches S (2) to S (n). The switch S (2) to S (n) is charged with a voltage sufficient to start conduction, and the switch may malfunction.

  Therefore, in this embodiment, a second discharge time constant control circuit in which the second capacitors Cs (1) to Cs (n) and the second current limiting means are connected in series is added. As a result, the discharge time constant becomes longer, and thus the malfunction of the high voltage switch 3 can be prevented.

FIG. 3 will be described with specific numerical values. For example, a switch connected in series in a plurality of stages is designed to be cut off by a switch in which 100 voltages of 50 kV are connected in series. Other numerical values are as follows.

  The resistance to cut off the wave tail is 100kΩ, and the time to keep the wave tail cut off is 20mS. The output junction capacitance Coss of the switch is 125 pF and the leakage current is 200 μA (per drain-source voltage of 500 V). Rdss = 2.5MΩ, and the gate voltage for conducting the switch is 4-15V. The balance resistors Rb (1) to Rb (n) are 500 kΩ or more. This is because the balance resistors Rb (1) to Rb (n) have a large loss because a current always flows, and therefore must be suppressed to 0.5 W (per number of balance resistors) or less.

  The first capacitors Cb (1) to Cb (n) have a capacity of 20 nF or more. This is because, in order to maintain the gate voltage during the wave tail cut-off operation, the discharge time constant with the potential of the first capacitors Cb (1) to Cb (n) as the time gate voltage range must be 10mS or more. This is because the discharge of Cb (1) to Cb (n) is mainly caused by the balance resistors Rb (1) to Rb (n).

  In addition, the discharge time constant of the output junction capacitance Coss of each switch is only about 125pF x 2.5MΩ = 0.3mS, which is shorter than the discharge time constant 10mS of Cb (1) to Cb (n), which may cause malfunction. There is. To eliminate this malfunction, add the second capacitors Cs (1) to Cs (n).

  According to this embodiment, it is possible to provide an X-ray apparatus capable of stable circuit operation even under various voltage conditions. Also, the unique effect of the first embodiment is that, for example, when CS is added with a capacity of 4 nF, this discharge time constant is 4 nF × 2.5 MΩ = 10 mS, and when combined with the output junction capacitance Coss of each switch, the discharge of Cb It can be longer than the time constant. Such a long discharge time constant can prevent malfunction.

  The switches S (1) to S (n) have a junction capacitance in the diode DL that prevents reverse current. For this reason, a reverse current may flow through the switches S (1) to S (n). As described above, the voltage applied between the anode (A) and the cathode (K) changes in the negative direction, and is lower than the voltage stored in the switches S (1) to S (n). Considering the case, the potential difference is applied to the diode DL in reverse, and the junction capacitance of the diode DL is charged in the reverse direction. This current is supplied by a current flowing in the reverse direction from the switches S (1) to S (n). That is, the junction capacitances Coss (1) to Coss (n) between the drain and source of each switch and the current that discharges the second capacitors Cs (1) to Cs (n) are supplied. The voltage change due to this current is determined by the ratio of these capacities. That is, the ratio between the junction capacitance of the diode DL and the combined capacitance of the junction capacitors Coss (1) to Coss (n) between the drain and source of each switch and the second capacitors Cs (1) to Cs (n). .

  Here, the description will be made using specific numerical values as described above. The junction capacitance of the diode DL is 4 pF, and the combined capacitance between the drain and source of each switch Coss (1) to Coss (n) and the second capacitors Cs (1) to Cs (n) is 41.25 pF. is there.

  Therefore, when the voltage E0 applied between the anode (A) and the cathode (K) of the switches S (1) to S (n) drops to E1 at time t, the diode DL (D) −cathode (K) Assuming that the potential between them drops to E2, discharge from the combined capacitance Co of the junction capacitances Coss (1) to Coss (n) between the drain and source of each switch and the second capacitors Cs (1) to Cs (n) Current io = Co * (E0-E2) / t, current iDL = CDL * (E2-E1) / t discharged from the junction capacitance of the diode DL, and io = iDL, so Co / CDL = (E2- E1) / (E0-E2). When 10kV is reduced from E0 = 50kV to E1 = 40kV, E2 = (Co * E0 + CDL * E1) / (Co + CDL) = 49.12kV, which is 0.88kV lower. As described above, the electric charge stored in the junction capacitances Coss (1) to Coss (n) between the drain and source of each switch and the second capacitors Cs (1) to Cs (n) is the leakage current of the aforementioned switches. The discharge is performed with a time constant that is faster than the discharge by the resistors Rdss (1) to Rdss (n) replaced with. For this reason, a malfunction is assumed unless the capacitance of the second capacitor CS is larger than that calculated by the above calculation. To prevent this malfunction, the junction capacitance Coss between the drain and source of each switch calculated from the shortest discharge time constant in the load such as an X-ray tube and the junction capacitance of the diode DL that prevents reverse current (1) -Coss (n) and the first capacitor to hold the gate voltage during the wave tail cut-off operation using the discharge time constant of the charge stored in the second capacitors Cs (1) -Cs (n) It must be longer than the discharge time constant of Cb (1) to Cb (n).

FIG. 4 is a diagram showing the second embodiment as an example of the configuration of the wave tail cutoff circuit 1. In FIG. In the second embodiment, the circuit of the first embodiment is arranged between the gates of the switches S (1) to S (n) and the first current limiting means Rg (1) to Rg ( n) as the hysteresis characteristic means. Zener diodes Dzb (1) to Dzb (n) are connected.

  Thus, according to the second embodiment, it is possible to provide an X-ray apparatus capable of stable circuit operation even under various voltage conditions. In addition, the specific effect of the second embodiment is that, for example, by detecting a sudden drop between the anode (A) and the cathode (K) due to the partial discharge of the X-ray tube device 17, a minute amount from the X-ray tube device 17 is reduced. The reliability of the high-voltage switch circuit can be improved by preventing the malfunction of the switch due to noise generated due to a rapid discharge.

{Embodiment 3}
FIG. 5 is a diagram showing the third embodiment as an example of the configuration of the wave tail cutoff circuit 1. FIG. In the third embodiment, the second capacitors Cs (1) to Cs (n) of the circuit shown in the first embodiment are connected to the ground potential such as the drains and the cathodes (K) of the switches S (1) to S (n). This is an example of connection. In this example, it is connected to the ground potential, but it may be connected to the cathode (K) such as a housing instead of the ground potential.

  According to this embodiment, it is possible to provide an X-ray apparatus capable of stable circuit operation even under various voltage conditions. A unique effect of the third embodiment is that the number of circuit elements can be reduced by using the stray capacitance generated between the housing and the like as the second capacitors Cs (1) to Cs (n).

{Embodiment 4}
FIG. 6 is a diagram showing the fourth embodiment as an example of the configuration of the wave tail cutoff circuit 1. In FIG. In the fourth embodiment, as shown in FIG. 6, the switches S (1) to S (n) make the drive signal 5 positive between the gate and source of the switch S (1), and the switch S (1) is made conductive. Thus, the charge stored in the first capacitors Cb (1) to Cb (n) sequentially applies a voltage between the gates and sources of the switches S (2) to S (n), and the high voltage switch circuit It is controlled to be in the on state.

  Thus, according to the fourth embodiment, an X-ray apparatus capable of stable circuit operation even under various voltage conditions can be provided. The characteristic effect of the fourth embodiment is that the charge time constant of the voltage applied to the switches S (1) to S (n) is set by storing charges in the second capacitors Cs (1) to Cs (n). It can be set longer than the discharge time constant of one capacitor Cb (1) to Cb (n). This setting can prevent malfunction of the high voltage switch.

{Embodiment 5}
FIG. 7 is a diagram showing the fifth embodiment as an example of the configuration of the wave tail cutoff circuit 1. In FIG. In the fifth embodiment, as shown in FIG. 7, a discharge resistor RD ′ is added on the cathode (K) side of the switch S (1). The stray capacitance CS described below is equivalent to the second capacitor.

  Here, the charging voltage of the stray capacitance Cs (0) is instantaneously discharged simultaneously with the conduction of the switch S (1). At this time, the internal resistance of the switch S (1) is slightly discharged, but most of the charging voltage is shared and charged to the remaining stray capacitances Cs (1) to Cs (n). Even when the switch S (2) is turned on, the charging voltage of the stray capacitance Cs (1) is discharged, but most of the charging voltage is shared and charged by the stray capacitances Cs (2) to Cs (n). That is, the switches S (1) to S (n) are sequentially turned on, and the switches S (1) to S (n) are turned on as much as the stray capacitances Cs (0) to Cs (n) of the part are discharged. The voltage charged in any of the stray capacitances Cs (0) to Cs (n) in the part that is not increased. As a result, when the charging voltage of any of Cs (0) to Cs (n) exceeds the rated voltage of the switches S (1) to S (n), it is performed ten to several dozen times per second. In some wave tail cutting operations, the life of the switch S (n) may be shortened. Therefore, by connecting the discharge resistor RD ′ between the switch S (1) and the cathode (K), the stray capacitance CS existing in each switch S (1) to S (n) is changed to the switch S (1) to When discharging is performed simultaneously with the conduction of S (n), it is discharged via the discharge resistor RD ′.

  As a result, the characteristic effect of the fifth embodiment can reduce the voltage charged in the stray capacitance CS present in the non-conductive switch S.

{Embodiment 6}
FIG. 8 is a diagram showing the sixth embodiment as an example of the configuration of the wave tail cutoff circuit 1. In FIG. In the sixth embodiment, as shown in FIG. 8, in addition to the circuit configuration of the fifth embodiment, a discharge resistor RD is added between adjacent switches.

  Here, since the voltage charged in the stray capacitance CS becomes higher as it is closer to the anode side, the discharge voltage RD having a fixed impedance value may not be able to discharge the charge voltage of the stray capacitance CS.

  Therefore, by adding a discharge resistor RD between adjacent switches, the discharge current is discharged with an impedance obtained by adding the two discharge resistors RD. When the last switch S (n) is turned on, the discharge current is discharged with an impedance obtained by adding all the discharge resistors RD connected to the respective switches.

  Thereby, the characteristic effect of the sixth embodiment can reduce the voltage charged in the stray capacitance CS existing in the non-conducting switch S. In addition, since the discharge resistance is dispersed and the heat source is also dispersed in the housing of the wave tail cutting device 1, the heat radiation effect by the housing wall surface can be improved.

{Embodiment 7}
FIG. 9 is a diagram illustrating the seventh embodiment as an example of the configuration of the wave tail cutoff circuit 1. FIG. In the seventh embodiment, as shown in FIG. 9, in addition to the circuit configuration of the fifth embodiment, the connection of the wave tail cutting circuit is changed between the anode (A) -cathode (K) to the anode (A) -ground and to the ground. -Changed between cathodes (K).

  As a result, the characteristic effect of the seventh embodiment can reduce the voltage charged in the stray capacitance CS present in the non-conducting switch S. Further, since the discharge current due to the stray capacitance flows to the ground, the influence of noise is reduced and the reliability is improved.

{Embodiment 8}
FIG. 10 is a diagram illustrating the eighth embodiment as an example of the configuration of the wave tail cutoff circuit 1. FIG. In the eighth embodiment, as shown in FIG. 10, in addition to the circuit configuration of the sixth embodiment, the connection of the wave tail cutting circuit is connected from the anode (A) -cathode (K) to the anode (A) -ground and to the ground. -Changed between cathodes (K).

  Thereby, the characteristic effect of the eighth embodiment can reduce the voltage charged in the stray capacitance CS present in the non-conducting switch S. In addition, since the switches are divided into the anode and the cathode to perform the switching operation at the same time, all the high-voltage switches are turned on, and the time is reduced to half as compared with the circuit of FIG. Therefore, the discharge efficiency can be improved by adjusting the value of the discharge resistance as compared with the sixth embodiment.

  In the above embodiment, the resistors Rs (1) to Rs (n) are illustrated in series with the capacitors Cs (1) to Cs (n). The resistor is inserted to suppress the short-circuit current when the switches S (1) to S (n) short-circuit the charges of Cs (1) to Cs (n). For this reason, it does not necessarily need to be a resistor, and can be omitted if the internal impedance and short circuit tolerance of the switches S (1) to S (n) are allowed.

  Further, although the switches S (1) to S (n) are shown as MOS-FETs, they are not necessarily required, and any semiconductor switching element that can constitute a high-voltage switch that can be sequentially driven by series connection may be used.

The block diagram of the inverter type | mold X-ray apparatus using the high voltage switch circuit in each embodiment of this invention. FIG. 3 is an explanatory diagram of an example of a high voltage switch circuit according to the first embodiment of the present invention. FIG. 4 is an explanatory diagram of an equivalent circuit of the high voltage switch circuit of FIG. FIG. 6 is an explanatory diagram of a high voltage switch circuit example according to the second embodiment of the present invention. FIG. 6 is an explanatory diagram of a high voltage switch circuit example according to the third embodiment of the present invention. FIG. 7 is an explanatory diagram of a high voltage switch circuit example according to the fourth embodiment of the present invention. FIG. 6 is an explanatory diagram of a high voltage switch circuit example according to the fifth embodiment of the present invention. FIG. 10 is an explanatory diagram of a high voltage switch circuit example according to the sixth embodiment of the present invention. FIG. 10 is an explanatory diagram of a high voltage switch circuit example according to the seventh embodiment of the present invention. FIG. 10 is an explanatory diagram of a high voltage switch circuit example according to an eighth embodiment of the present invention.

Explanation of symbols

  1 Wave tail cutoff circuit, 2 Current limiting means, 3 High voltage switch circuit, 4 Drive circuit, 5 Drive signal, 10 Single-phase AC power supply, 11 Rectifier, 12 (Low voltage side) capacitor, 13 Inverter circuit, 14 High voltage transformer , 15 High voltage rectifier, 16 High voltage capacitor, 17 X-ray tube device, 18 Control circuit, 19 Exposure signal, S (1) to S (n) Semiconductor switch, Cs (0) to Cs (n) Second Capacitor (including stray capacitance), Rs (1) to Rs (n) Second current control means (resistance).

Claims (5)

A plurality of semiconductor switches connected in series, a first terminal connected in series, and connected between the control terminal of the semiconductor switch and the other end of the other semiconductor switch to which the semiconductor switch and one end are connected. A first capacitor, a diode connected in parallel to the first resistor, a second resistor connected in parallel to the first capacitor, and one of the plurality of semiconductor switches. In a high voltage switch control circuit having a control circuit that controls conduction of the remaining semiconductor switches by controlling conduction of two semiconductor switches,
A third resistor and a second capacitor connected in series and connected in parallel to all of the plurality of semiconductor switches, and the second capacitor is more than the discharge time constant of the first capacitor. The high voltage switch control circuit is characterized in that at least one of the capacitance of the second capacitor and the resistance value of the third resistor is set so that the discharge time constant becomes longer . 2. The high voltage switch control circuit according to claim 1, wherein a semiconductor element having hysteresis characteristics is connected between the control terminal of the semiconductor switch and the first resistor. The high-voltage switch control circuit according to claim 1 or 2, wherein the plurality of semiconductor switches connected in series are connected to each other through a discharging resistor. 4. The high voltage switch control circuit according to claim 1, wherein the plurality of semiconductor switches are MOS type FETs. A rectifier connected to a single-phase AC power source for converting AC voltage to DC voltage; an inverter for converting the converted DC voltage to high-frequency AC voltage; a high-voltage transformer for boosting the converted high-frequency AC voltage; A high-voltage rectifier that converts the boosted high-frequency AC high voltage into a DC high voltage; an X-ray tube that is supplied with the converted DC high voltage; and a wave-tail cutoff means that is connected in parallel to the high-voltage rectifier. An X-ray apparatus comprising: a control means for controlling a high voltage switch means included in the wave tail cutoff means according to an exposure signal of the X-ray tube;
5. The X-ray apparatus according to claim 1, wherein the high voltage switch means is a high voltage switch control circuit according to any one of claims 1 to 4.

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