Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/08—Electrical details
  • H05G1/10—Power supply arrangements for feeding the X-ray tube

Definitions

• the present invention provides an inverter-type X-ray high-voltage device that converts a DC voltage into a high-frequency AC voltage using an inverter circuit and applies the output AC voltage to an X-ray tube via a transformer, and an X-ray device using the same. Brightness of the line device. Background art
• Recent medical X-ray high-voltage devices have been widely applied to general X-ray radiography devices, cardiovascular X-ray devices, X-ray CT devices, and the like.
• the demand for these X-ray high-voltage devices is to be able to stably supply the target tube voltage, but recently, in addition to this, the range of the tube voltage output range and the installation
• Japanese Patent Application Laid-Open No. Hei 9-190898 discloses an inverter type X-ray high voltage device using pulse modulation (pulse width and phase shift) to obtain a wide output for tube voltage control.
• a tube voltage is detected by a tube voltage detector or the like, and this and a target value are input to an inverter control circuit to determine and control the phase difference and frequency of the inverter circuit.
• the bias of the core of the high-voltage transformer (high-voltage transformer) and the magnetic saturation are dealt with by increasing the size of the core as described below.
• Magnetic flux density is determined by the magnitude, frequency, and core cross section of the current flowing through the primary side of the high-voltage transformer. Generally, to avoid this magnetic saturation, the cross-sectional area of the core of the high-voltage transformer is increased. When the frequency of the primary current of the high-voltage transformer is constant, the magnetic density is maximized when the current is the maximum, so the design is made so that the core does not reach the magnetic saturation region at this time. . However, in an inverter-type X-ray high-voltage device with a large load fluctuation range using an X-ray tube, the current flowing through the primary side of the high-voltage transformer is small. Magnetic saturation may occur in high voltage transformers. Therefore, even under light load, the above cross section may still be insufficient.
• the bias of the core of the high-voltage transformer (high-voltage transformer) is corrected so that the steady-state magnetization and the magnetic saturation of the core are reduced. It discloses that the size of the X-ray high-voltage device can be reduced by preventing the core size.
• the tube voltage is controlled by a DCZDC converter, and the magnetization is controlled by changing the pulse width.
• the switching width of the switching element is changed to control the magnetization. Can no longer be controlled.
• the increase in size due to the presence of a DCZDC converter is accepted to control the tube voltage, and the magnetization is controlled by modulating the pulses with an inverter circuit to control the high voltage transformer (high-voltage transformer).
• the high voltage transformer high-voltage transformer
• An object of the present invention is to provide an X-ray high-voltage device capable of achieving both a performance aspect such as a wide output range, a reduction in installation area, and a reduction in size and weight. More specifically, an inverter type X-ray converter that can omit the DCZDC converter for controlling the tube voltage and reduce the size of the device while controlling the demagnetization and downsize the core of the high-voltage transformer A voltage device is provided. Another object of the present invention is to provide an inverter-type X-ray high-voltage device capable of preventing magnetic saturation of a high-voltage transformer, which is mainly caused by variation in characteristics of switching elements, and capable of reducing the size of a high-voltage transformer core. Disclosure of the invention
• the present invention provides a DC power supply, an inverter circuit that has a plurality of semiconductor switching devices, is connected to the DC power supply, and converts a DC voltage to an AC voltage, and the plurality of semiconductor switching devices.
• a high-voltage transformer having a primary winding connected to the output side of the inverter circuit, and an X-ray tube connected to the secondary winding side of the high-voltage transformer.
• detection control means for controlling the output voltage of the inverter circuit and detection control means for controlling the X-ray tube voltage are further provided. Are also input to the drive circuit.
• the present invention provides an inverter circuit, wherein the output from the detection control means for controlling the output voltage of the inverter circuit is symmetric with the output voltage of the inverter circuit when the detection result that the inverter output voltage is asymmetric is positive or negative.
• the output from the X-ray tube voltage detection control means is for pulse-controlling the tube voltage in order to obtain the target tube voltage.
• the semiconductor switching devices are first to fourth semiconductor switching devices, and the first and second switching devices and the third and fourth switching devices are respectively connected to the DC power supply.
• the first and second switching devices and the third and fourth switching devices are connected in parallel with each other, and the first and second switching devices are connected to eliminate the positive / negative asymmetry of the output voltage.
• Pulse control is performed on at least one of the third and fourth switching devices so that the output voltage of the inverter is positive-negative symmetric, and the tube voltage is the same as that of the first and second switching devices. It is characterized in that pulse control is performed by a phase shift between the third and fourth switching devices.
• the invention is characterized in that the switching device is an IGBT, a MOS-FET, or a bipolar transistor.
• the present invention provides the detection control means for controlling the output voltage of the inverter circuit, wherein at least a current detector or a voltage detection means provided on the output side of the inverter circuit is provided. It is characterized in that one of the steps is included.
• the detection control means for controlling the output voltage of the inverter circuit includes at least one of a DC component detection circuit and an output voltage pulse unbalance detector.
• the present invention also provides a current detector included in the detection control means for controlling the output voltage of the inverter circuit, wherein the current detector includes any one of an RC finoleter, a first-order lag filter, a second-order lag filter, or a second-order or higher-order lag filter It is characterized by using.
• the present invention provides an X-ray source, an X-ray detector arranged opposite to the X-ray source, and a rotary drive around the subject holding the X-ray source and the X-ray detector.
• an X-ray CT apparatus having an X-ray high-voltage apparatus provided with the apparatus.
• the present invention provides an X-ray source, an X-ray receiving means opposed to the X-ray source with a subject interposed therebetween, and an X-ray high-voltage device having the above function for supplying a tube current to the X-ray source.
• An X-ray apparatus having:
• the magnetic saturation of the high-voltage transformer which occurs when the magnetic flux density is small and the load condition varies, causes the output voltage of the inverter circuit to be completely symmetrical due to the characteristic variation of the semiconductor switching device of the inverter circuit.
• the core of the high-voltage transformer is demagnetized, and it is determined that the demagnetization is accumulated due to the hysteresis characteristics of the core and eventually reaches the magnetic saturation region of the core.
• a detector is provided to directly or indirectly detect that the output voltage of the circuit is positive or negative asymmetric, and the inverter circuit is controlled so that the output voltage of the inverter circuit becomes positive and negative symmetric at least when the detection by this detector is performed.
• Inverter due to characteristic variation of the semiconductor switching device that constitutes the inverter circuit Can correct the asymmetrical positive and negative output voltage, to suppress the biased magnetization of the high-voltage transformer becomes remarkable in light load condition, it can be miniaturized to prevent magnetic saturation of the high voltage transformer.
• the magnetic saturation of the high-voltage transformer generated under a load condition with a small magnetic flux density is caused by the characteristic variation of the semiconductor switching device of the inverter circuit.
• the output voltage of the inverter circuit may not be completely symmetrical, so that the core of the high-voltage transformer may be demagnetized, and this demagnetization may be accumulated due to the hysteresis characteristic of the core, and eventually the core may be magnetically saturated.
• a detector is provided on the output side of the inverter circuit to detect that the output voltage of the inverter circuit is positive or negative asymmetry.
• a phase shifter applied to the semiconductor switching device of the inverter circuit so as to be symmetrical is provided with correction means for correcting the PWM signal. Corrects the asymmetry of the output voltage of the inverter circuit due to variations in the characteristics of the constituent semiconductor switching devices. Phase shift PWM signal can be corrected to suppress the biased magnetization of the high-voltage transformer becomes remarkable Te light load conditions smell, it can be reduced in size to prevent the magnetic saturation of the high voltage transformer.
• FIG. 1 is a block diagram of an inverter type X-ray high voltage device according to an embodiment of the present invention.
• FIG. 2 is a circuit diagram showing a DC component detection circuit in the inverter type X-ray high voltage device shown in FIG.
• FIG. 3 is a characteristic diagram showing the inverter output current and the like in the inverter type X-ray high voltage device shown in FIG.
• FIG. 4 is a block diagram of an inverter type X-ray high voltage device according to another embodiment of the present invention.
• FIG. 5 is an operation characteristic diagram of the inverter type X-ray high-voltage device shown in FIG. 1 when characteristics are varied in each semiconductor switching device.
• FIG. 1 is a block diagram of an inverter type X-ray high voltage device according to an embodiment of the present invention.
• FIG. 6 is an operation characteristic diagram of each semiconductor switching device at the time of correction in the inverter type X-ray high voltage device shown in FIG.
• FIG. 7 is a block diagram of an inverter type X-ray high voltage device according to still another embodiment of the present invention.
• FIG. 8 is a view showing an X-ray CT apparatus equipped with the inverter type X-ray high voltage apparatus according to the present invention.
• FIG. 9 is a view showing an X-ray apparatus equipped with the inverter type X-ray high voltage apparatus according to the present invention.
• 1 is a commercial power supply
• 2 is a rectifier circuit
• 3 is a smoothing capacitor
• 4 is an inverter circuit
• 5 is a high voltage transformer
• 6 is a high voltage rectifier
• 7 is a tube voltage detector
• 8 is an X-ray tube
• Numeral 12 indicates a semiconductor switching device
• 17 indicates a DC component detection circuit
• 18 indicates a phase shift PWM signal circuit
• 19 indicates a tube voltage feedback control circuit
• 22 indicates a current detector.
• FIG. 1 is a block circuit diagram showing an inverter type X-ray high voltage device according to one embodiment of the present invention.
• a rectifier circuit 2 is connected to the three-phase or single-phase commercial power supply 1, and a smoothing capacitor 3 is connected to an output side of the rectifier circuit 2.
• a smoothing capacitor 3 is connected to an output side of the rectifier circuit 2.
• an inverter circuit 4 having semiconductor switching devices 9 and 10 and semiconductor switching devices 11 and 12 in a full-bridge configuration is connected.
• an IGBT, a MOS-FET, a bipolar transistor, or the like can be used.
• the primary side of the high-voltage transformer 5 is connected between the semiconductor switching devices 9 and 10 and between the semiconductor switching devices 11 and 12.
• a current detector 22 is connected to the primary side of the high-voltage transformer 5, and the current detector 22 detects the output current of the inverter circuit 4 configured by the semiconductor switching devices 9 to 12. ing.
• a high-voltage rectifier 6 is connected to the secondary side of the high-voltage transformer 5, and a tube voltage detector 7 and an X-ray tube 8 are connected to the output side of the high-voltage rectifier 6.
• the X-ray high-voltage device having such a configuration converts the DC voltage from the rectifier circuit 2 into a high-frequency AC voltage using the inverter circuit 4 and boosts the output voltage via the high-voltage transformer 5.
• the DC voltage is supplied to the X-ray tube 8 after being rectified by the high-voltage rectifier 6 to emit X-rays.
• the voltage applied to the X-ray tube 8 is detected by the tube voltage detector 7, and the detected tube voltage detection value 21 is compared with the tube voltage target value 20 in the tube voltage feedback control circuit 19, and the X-ray tube is detected. Thereafter, a phase shift PWM signal is transmitted from the phase shift PWM signal circuit 18 so that the voltage applied to 8 becomes a desired voltage.
• This signal is supplied to each of the semiconductor switching devices 9 to 12 as a drive signal by the drive circuits 13 to 16.
• the primary side of the high-voltage transformer 5 has a current transformer that can detect the DC component. (DC-CT) etc., and when the DC component detection circuit 17 detects that the output current of the inverter circuit 4 includes a DC component detected by the current detector 22, the semiconductor switch Correction means for correcting the phase shift PWM signal of the switching device.
• DC-CT DC component detection circuit
• the semiconductor switching device 9 and the semiconductor switching device 9 It is configured to input to the drive circuits 13 and 14 of the switching device 10 to correct the phase shift PWM signal.
• the DC component detection circuit 17 that extracts a direct current component from the output current of the inverter circuit 4 flowing on the primary side of the high-voltage transformer 5 will be described with reference to the circuit diagram shown in FIG.
• FIG. 4D shows the detection of the maximum value and the minimum value of the output current of the inverter circuit 4, and the deviation of the output current of the inverter circuit 4 can be detected from the difference therebetween.
• the DC component detection circuit 17 is not limited to these examples, and may be any circuit that extracts a DC component from the output current of the inverter circuit 4.
• Such a DC component detection circuit 17 detects a deviation in the output current of the inverter circuit 4, and a correction means corrects the phase shift PWM signal for controlling the semiconductor switching devices 9 to 12 so as to eliminate the deviation.
• a correction means corrects the phase shift PWM signal for controlling the semiconductor switching devices 9 to 12 so as to eliminate the deviation.
• This correction changes, for example, the duty factor (duration) of the semiconductor switching devices 9 and 10 in the left arm of the inverter circuit 4 according to the average bias in the output current of the inverter circuit 4.
• the output current of the inverter circuit 4 is corrected to a stable waveform as shown in FIG.
• correction means for correcting the phase shift PWM signal for controlling the semiconductor switching devices 9 to 12 will be described more specifically.
• the semiconductor switching devices 9 and 10 operate at a duty factor of 50% without being simultaneously turned on. Even at 12, the duty factor is operated at 50% without being turned on at the same time. If the semiconductor switching devices 9 to 12 have ideally the same characteristics, the ON / OFF control is performed as shown by the solid line in the figure, and the output voltage of the inverter circuit 4 is exactly symmetric with the same pulse width.
• the DC component detecting circuit 17 that has detected the DC component corrects the phase-shifted PWM signal input to the driving circuits 13 and 14 of the semiconductor switching device 9 and the semiconductor switching device 10 according to the DC component. That is, the duty factor of the semiconductor switching device 9 is increased and the duty factor of the semiconductor switching device 10 is decreased in accordance with the detected DC component as shown by the dotted line in FIG. As a result, the inverter output voltage is corrected to a positive / negative symmetrical waveform as shown by the dotted line in FIG. 6, eliminating the bias in the high-voltage transformer 5 and generating magnetic saturation. Can be prevented.
• Such an inverter-type X-ray high-voltage device is provided with correction means for controlling the inverter circuit 4 so that the DC component approaches zero at least when the DC component is detected by the current detector 22.
• Magnetic saturation in the transformer 5, especially in inverter type X-ray high voltage equipment with a large load fluctuation range, is used when the current value flowing through the primary side of the high voltage transformer 5 is small, that is, when used under load conditions where the magnetic flux density is small.
• the driving time of the semiconductor switching devices 9 to 12 is short, an inverter circuit in which the length of time due to the characteristic variation of each of the semiconductor switching devices 9 to 12 is relatively larger than the original signal length It becomes possible to prevent the magnetic saturation which becomes remarkable under the condition of light load where the output of 4 is small. Therefore, the magnetic coupling between the primary side and the secondary side can be kept good, the function of the high voltage transformer 5 can be used effectively, and the output current of the inverter circuit 4 caused by magnetic saturation can be prevented from increasing. Can be.
• a current detector 22 is provided on the output side of the inverter circuit 4 to detect that the output voltage is asymmetrical.
• the output voltage of the inverter circuit 4 is symmetrical at least when the current detector 22 detects the current.
• the correction means for correcting the phase shift PWM signal applied to the semiconductor switching devices 9 to 12 of the inverter circuit 4 is provided so as to satisfy the following condition.
• the phase-shifted PWM signal can be corrected to correct the positive / negative asymmetry of the output voltage of the inverter circuit 4 due to the characteristic variation of the semiconductor switching devices 9 to 12 that constitute the inverter circuit 4. Therefore, it is possible to reduce the size of the high-voltage transformer by suppressing magnetic bias and preventing magnetic saturation of the high-voltage transformer.
• the phase shift PWM signal is corrected for the semiconductor switching devices 9 and 10 in the left arm of the inverter circuit 4, but this correction is performed by the inverter circuit 4. This may be performed on the semiconductor switching devices 11 and 12 in the right arm of the right side, or may be performed on each of the left and right side arms.
• FIG. 4 is a block diagram showing an inverter type X-ray high voltage device according to another embodiment of the present invention.
• FIG. 2 is a configuration diagram of a mouthpiece, in which equivalents to those in the embodiment shown in FIG.
• the inverter circuit 4 having a half-bridge structure is used, and the semiconductor switching devices 11 and 12 are connected in series except for the inverter circuit 4 having a full-bridge structure shown in FIG.
• the primary winding of the high-voltage transformer 5 is connected between the smoothing capacitors 3a and 3b and between the semiconductor switching devices 9 and 10.
• a DC component detection circuit 17 that detects a DC component from a current detector 22 provided on the primary side of the high-voltage transformer 5 corrects a phase-shifted PWM signal input to the drive circuits 13 and 14 of the semiconductor switching devices 9 and 10. I am trying to do it.
• an inverter circuit 4 that performs PWM control such as a push-pull structure
• a shunt resistor is used instead of a current transformer (DC-CT), or the magnetic flux of a transformer is detected.
• a current detector 4 that can detect an output current including a DC component such as an output current may be used.
• FIG. 7 is a block diagram showing an inverter type X-ray high-voltage device according to still another embodiment of the present invention.
• the same components as those of the embodiment shown in FIG. Description is omitted.
• a voltage detector 23 is provided on the output side of the inverter circuit 4, that is, on the primary side of the high-voltage transformer 5, and the output voltage of the inverter circuit 4 detected by the voltage detector 23 is output as an output voltage pulse.
• Input to unbalance detector 24 The output voltage pulse imbalance detector 24 detects the difference in the pulse width between the positive side and the negative side of the inverter output voltage shown in FIG.
• the correction means that operates when the output voltage pulse unbalance detector 24 detects the pulse width imbalance is configured in the same manner as in the previous embodiment.
• the phase shift PWM signal input to the drive circuits 13 and 14 of the semiconductor switching devices 9 and 10 is corrected according to the imbalance, and the inverter circuit 4 is controlled so that the inverter output voltage is symmetrical.
• the output voltage of the inverter circuit 4 shown in FIG. The imbalance between the negative side and the negative side is detected by the current detector 22 provided on the output side from the DC component of the output current of the inverter circuit 4 shown in FIG. 3, but in this embodiment, The imbalance between the positive side and the negative side of the output voltage of the inverter circuit 4 shown in FIG. 5 is detected from the pulse width of the output voltage of the inverter circuit 4 by a voltage detector 23 provided on the output side. Also in this embodiment, the same effect as in the embodiment shown in FIG. 1 can be obtained.
• either one of the current detector 22 or the voltage detector 23 can be used as the detector provided on the primary side of the high-voltage transformer 5, and the inverter circuit 4 shown in FIG. Correction means for directly or indirectly detecting the imbalance between the positive and negative sides of the output voltage of the inverter and controlling the inverter circuit 4 so that the inverter output voltage becomes symmetrical when the detection is detected. What is necessary is just to comprise.
• the DC component shown in FIG. 3A is reduced to zero by the correction means, or the difference between the positive and negative pulse widths of the output voltage of the inverter circuit 4 is zero.
• Each phase-shifted PWM signal was corrected so that the DC component or the pulse width difference at which the demagnetization in the high-voltage transformer 5 had no adverse effect was set as a predetermined target value.
• the phase shift PWM signal may be corrected as follows.
• the inverter type X-ray high voltage apparatus of the present description it is possible to achieve both performance aspects such as a wide output range, reduction in installation area, and reduction in size and weight. Furthermore, while eliminating the need for a DO / DC converter to control the tube voltage and reducing the size of the device, it is also possible to control the magnetization and reduce the size of the core of the high-voltage transformer. It also prevents magnetic saturation of the high-voltage transformer caused by variations in the characteristics of the switching elements, and suppresses the magnetic bias of the high-voltage transformer, which is remarkable under light load conditions, to prevent magnetic saturation of the high-voltage transformer. In addition, it is possible to downsize the high-voltage transformer and the inverter-type X-ray high-voltage device using the same.
• FIG. 8 illustrates the best mode for carrying out the present invention for an X-ray CT apparatus.
• reference numeral 103 denotes a rotating disk that holds an X-ray source 101 and an X-ray detector 102 and is driven to rotate around a subject 104.
• Reference numeral 105 denotes image reconstruction means for imaging a tomographic image of the subject based on the X-ray intensity detected by the X-ray detector 102.
• Reference numeral 100 denotes an inverter-type X-ray high-voltage device that supplies a tube current to the X-ray source 101, and has the configuration and functions described in the above embodiment.
• FIG. 9 illustrates the best mode for carrying out the present invention for an X-ray apparatus.
• 101 is an X-ray source
• 106 is an X-ray image receiving means.
• Reference numeral 100 denotes an inverter-type X-ray high-voltage device that supplies a tube current to the X-ray source 101, and has the configuration and functions described in the above embodiment.

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• 2002
  • 2002-06-04 JP JP2002162549A patent/JP4343491B2/ja not_active Expired - Lifetime
• 2003
  • 2003-06-04 CN CNB038130483A patent/CN100340139C/zh not_active Expired - Lifetime
  • 2003-06-04 WO PCT/JP2003/007081 patent/WO2003103347A1/ja not_active Ceased

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