JP3431985B2 - Inverter type X-ray high voltage device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention converts an AC power supply into a direct current, converts the direct current into a high-frequency alternating current using an inverter circuit, and boosts the output voltage. X-ray high-voltage apparatus for generating an X-ray by applying a current to an X-ray tube by rectifying the X-ray with the X-ray tube.
The present invention relates to an inverter type X-ray high voltage device suitable for a device using a small power supply of 0 V and several kVA. 2. Description of the Related Art Conventionally, an inverter type X-ray high voltage device of this kind has been configured as shown in FIG. That is,
An AC voltage from a commercial 100 V single-phase AC power supply 30 is converted to a DC voltage by a single-phase full-wave rectifier circuit 2 composed of a thyristor via an AC reactor 1, and the DC voltage is smoothed by a smoothing capacitor 3 and then converted to an IGBT ( Full-bridge type inverter circuit 4 using insulated gate bipolar transistor)
To enter. The inverter circuit 4 is disclosed in Japanese Patent Application Laid-Open No. 63-1905.
As described in Japanese Patent Publication No. 56, the phase difference and the frequency of the operation of the switching element of the inverter circuit 4 by utilizing the resonance phenomenon of the leakage inductance and the stray capacitance of the resonance capacitor 5 and the high-voltage transformer 6. Is controlled to output a voltage corresponding to the voltage applied to the X-ray tube 8 as a load. The AC voltage output from the inverter circuit 4 is boosted by the high-voltage transformer 6 and is increased. The direct current was converted to direct current by the rectifier circuit 7 and applied to the X-ray tube 8. A voltage (tube voltage) applied to the X-ray tube 8
Is controlled as follows. First, the set value VS ₁ of the tube voltage and the set value IS ₁ of the current (tube current) flowing through the X-ray tube 8.
The gate control circuit 10 sets a gate control phase angle for driving each thyristor of the single-phase full-wave rectifier circuit 2 in accordance with the above, and amplifies this with a gate drive circuit 9 to amplify the same.
Give to each thyristor gate. Thereby, the gate phase for driving each thyristor of the single-phase full-wave rectifier circuit 2 is controlled, and a voltage corresponding to the load condition is input to the inverter circuit 4. The inverter circuit 4 includes a single-phase full-wave rectifier circuit 2
Enter the smoothed direct current output by the smoothing capacitor 3 the output is converted into a high frequency alternating current while controlling so tube voltage becomes a set value VS _1. That is, the phase difference and frequency control circuit 12 receives the respective detected values VS ₂ and IS ₂ of the tube voltage and the tube current and their set values VS ₁ and IS ₁ , and the tube voltage becomes the set value. Thus, the frequency of the inverter circuit 4 and the phase difference between the switching elements 41 and 44 and between the switching elements 42 and 43 are feedback-controlled. The output signal of the phase difference / frequency control circuit 12 is amplified by the gate drive circuit 11 and applied to the gate of each IGBT of the inverter circuit 4 to drive them. Thereby, the inverter circuit 4
, While controlled so that the tube voltage becomes a set value VS _1, converts single-phase full-wave rectifier circuit 2, a DC output of the smoothing capacitor 3 into an AC high frequency. The control of the tube current is performed by controlling the heating amount of the filament of the X-ray tube 8, but the description is omitted here. [0006] Such an inverter type X-ray high voltage apparatus is mainly applied to a gastric mass examination apparatus, a surgical X-ray television apparatus and the like, which are powered by a commercial 100 V single-phase AC power supply. When a predetermined load range can be controlled by controlling the phase difference and the frequency of the inverter circuit 4, the thyristor of the rectifier circuit 2 may be replaced with a diode to make the input voltage to the inverter circuit 4 uncontrollable. [0007] The conventional inverter type X
In the line high-voltage device, since the phase of the gate control signal of the thyristor of the rectifier circuit 2 is given as a phase delayed from the phase of the AC power supply voltage, for example, as shown in FIG. The phase was delayed by φ, and the power factor decreased. Therefore, the reactive power is large, and the installed capacity of the AC power supply is correspondingly increased. In addition, the current waveform is also distorted, and there are many harmonic components, which may cause the harmonic current to flow into the power supply system, which may cause a disturbance to other devices connected to the power supply system. Especially in the case of fluoroscopy, X
Although the power input to the tube is as small as several hundred W, the power factor is so low that the current flowing in the AC power supply reaches several tens of amperes, and the time is long and the power supply has a capacity of several kVA. It was a heavy burden for us. These problems were substantially the same even when the thyristor of the rectifier circuit 2 was replaced with a diode. SUMMARY OF THE INVENTION An object of the present invention is to provide a rectifier circuit for converting an AC power supply into a DC power supply and a rectifier circuit capable of improving a power factor and converting an AC input current into a sine wave, thereby reducing the power supply equipment capacity and achieving higher harmonics. An object of the present invention is to provide an inverter-type X-ray high-voltage device capable of removing a failure due to current. The above object is achieved by a first rectifier circuit for rectifying an AC power supply, a smoothing capacitor for smoothing an output voltage of the first rectifier circuit, and an output of the smoothing capacitor. An inverter circuit for converting into a high-frequency AC, a high-voltage converter for boosting the output voltage of the inverter circuit, and a second rectifier circuit for rectifying the output of the high-voltage transformer; In the inverter type X-ray high-voltage device for generating X-rays by applying the output voltage of (1) to an X-ray tube, the first rectifier circuit is connected to a self-extinguishing switching element and anti-parallel to the switching element. A full-wave bridge including at least two or more connection bodies with a diode, an AC reactor is provided between the full-wave bridge and the AC power supply, and the current of the AC power supply is only provided during fluoroscopy. And a pulse width modulation control of the switching element of the first rectifier circuit in accordance with an error between the phase difference of the voltage and the set value of the output voltage of the smoothing capacitor, to make the phases of the current and the voltage of the AC power supply coincide with each other. A current and voltage control circuit for controlling the output voltage of the smoothing capacitor to a set value; inputting the output voltage of the smoothing capacitor to the inverter circuit; By inputting a voltage smoothed by the smoothing capacitor to the inverter circuit. In particular, during imaging, the output is large but the exposure time is short, so the power at this time is obtained by using the energy charged in the smoothing capacitor as a power source. In the case where power is supplied from the AC power supply only for a long time, a self-extinguishing switching element of the first rectifying circuit uses a small-capacity element in accordance with the power supplied at the time of fluoroscopy. By keeping this element off, the power factor during fluoroscopy can be improved, and this object can be achieved. The current / voltage control circuit controls the switching element of the first rectifier circuit in accordance with the phase difference between the current and the voltage of the AC power supply and the set value of the output voltage of the smoothing capacitor. Then, the line current of the AC power supply and the phase of the phase voltage are made to coincide with each other, and the output voltage of the smoothing capacitor is controlled to a set value. As a result, the current and the voltage of the AC power supply have the same phase and have a sine wave without distortion. Therefore, the power factor is improved, the apparent power is reduced, the power supply capacity is reduced, and power supply harmonics are also eliminated. In addition, when the power during imaging is supplied from the smoothing capacitor and the power is supplied from the AC power supply only during fluoroscopy, an element having a small current rating can be used as the self-extinguishing switching element. So it will be more economical. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of an inverter type X-ray high voltage device according to the present invention. In this FIG.
Reference numeral 30 denotes a single-phase AC power supply, 1 denotes an AC reactor, 3 denotes a smoothing capacitor, 4 denotes a full-bridge type inverter circuit using an IGBT, 5 denotes a resonance capacitor, 6 denotes a high-voltage transformer, and 7 denotes a high-voltage rectifier circuit ( A second rectifier circuit), 8 is an X-ray tube as a load, 11 is a second gate drive circuit, 12
Is a phase difference and frequency control circuit of the inverter circuit 4, 13 is a first rectifier circuit (single-phase full-wave rectifier circuit), 14 is a current detector of the single-phase AC power supply 30, and 15 is a voltage detector of the single-phase AC power supply. , 16 is a first gate drive circuit, 17 is a current and voltage control circuit for controlling the current of the single-phase AC power supply 30 and the output voltage of the first rectifier circuit 13, and 32 is a console for setting each condition. is there. The first rectifier circuit 13 rectifies an AC voltage input from the single-phase AC power supply 30 via the AC reactor 1 into a DC voltage, and includes a switching element capable of self-extinguishing. here with constituting a full-bridge combination of four switching elements _131-134 consisting of an IGBT (insulated gate bipolar transistor) may reverse the diode D ₁ to D ₄ in their respective switching elements _131-134 These are connected in parallel.
The switching elements _131-134 are controlled by operating only when fluoroscopy as follows. That is, the current / voltage control circuit 17 generates a pulse width modulation control pulse so that the phase of the current of the single-phase AC power supply 30 matches the phase of the voltage, and the output voltage of the first rectifier circuit 13 is controlled to a set value. and, it is amplified by the first gate drive circuit 16 is supplied to the gates of the switching elements _131-134, a switching element _131-134 is switching control. FIG. 2 is a diagram showing a specific example of the current / voltage control circuit 17 together with its peripheral circuits. Here, the current / voltage control circuit 17 is a single-phase sine wave generator 20, an error amplifier 21, a multiplier, 22, an error amplifier 23, a saw-tooth wave generator 24, and a comparator 25, and operate as follows. First, the output voltage of the first rectifier circuit 13, i.e., detects the voltage VS ₄ the smoothing capacitor 3, which the set value VS ₃ and (tube voltage is set in accordance with the tube current), the voltage feedback control The comparison and amplification are performed by an error amplifier 21 for performing the comparison. On the other hand, the voltage of the single-phase AC power supply 30 is detected by the voltage detector 15, and the detected voltage is input to the single-phase sine wave generator 20 to generate a single-phase sine wave reference signal synchronized with the power supply voltage. This single-phase sine wave reference signal is multiplied by a signal from the error amplifier 21 by a multiplier 22 to provide a current reference signal for controlling the current of the single-phase AC power supply 30 (a sinusoidal waveform synchronized with the voltage waveform of the AC power supply 30). , And a current signal (actual current waveform) from the current detector 14 is input to the error amplifier 23, and the current feedback control deviation (the current command waveform and the actual current An error signal with the waveform is generated. The control deviation and the sawtooth wave from the sawtooth wave generator 24 are compared by a comparator 25 to create a modulated wave signal.
This is connected to the switching element 13 _{1 of} the first rectifier circuit 13.
And outputs as a signal for determining the timing of to 13 _fourth switching. This modulated wave signal is amplified by the first gate drive circuit 16 and the switching element (IGBT) 13
_1-13 give a _fourth gate (the voltage of the smoothing capacitor 3) an output voltage of the first rectifier circuit 13 VS ₄ set value VS ₃
Equally, and switching control of the switching elements _131-134 as the phase of the current and voltage of the single-phase AC power source 30 matches. FIG. 3 shows the current C of the single-phase AC power supply 30 and the pulse width modulation signal (current to the first gate drive circuit 16, output pulse of the voltage control circuit 17. The fundamental wave of this signal is in phase with the power supply voltage. It is a waveform diagram of d. When the inverter circuit 4 operates to supply electric power to the X-ray tube 8 and the inverter circuit input voltage (the voltage of the smoothing capacitor 3) drops below its set value, the waveform of the current c indicates the power supply voltage. In phase, power is supplied from the AC power supply 30 to the smoothing capacitor 3 side. When the input voltage of the inverter circuit rises above the set value, the waveform of the AC current c has a phase opposite to that of the power supply voltage, and the power is regenerated from the smoothing capacitor 3 to the AC power supply 30. Although the ripple component corresponding to the PWM frequency is also included in the pulse width modulation (PWM) control of Masahiro wave, smoothness can be obtained by inserting a filter (not shown) on the AC power supply 30 side or increasing the PWM frequency. A sinusoidal current is obtained. Returning to FIG. 1, the inverter circuit 4
Is to receive the DC voltage thus obtained, convert it to an AC voltage, and control the power supplied to the X-ray tube 8 using the resonance phenomenon. together constituting the full bridge by combining elements 41, 42, 43 and 44, in which their respective switching elements 41 to 44 formed by antiparallel connected diodes D ₇ to D _10. The capacitor 5 is one of resonance elements for generating a resonance current by the output voltage of the inverter circuit 4. The high voltage transformer 6 has its primary winding connected in series with the capacitor 5, causes resonance with the capacitor 5 and the leakage inductance, and boosts its resonance output. The second rectifier circuit 7 includes the high-voltage transformer 6
, And converts the output AC voltage to DC. The X-ray tube 8 serves as a load of the apparatus of the present invention, and generates X-rays when the output voltage of the second rectifier circuit 7 is applied. Next, the operation of the apparatus of the present invention will be described. Conditions such as fluoroscopy, imaging, tube voltage, and tube current are set on the console 32, and these are input to the apparatus. First,
At the time of fluoroscopy, the current of the first rectifier circuit 13, the phase difference between the voltage control circuit 17 and the inverter circuit 4,
A setting signal such as a tube voltage and a tube current during fluoroscopy is input to the frequency control circuit 12. The voltage and current control circuit 17 is a tube voltage,
Set the input voltage VS ₃ of the inverter circuit 4 corresponding to the set value VS _1, IS ₁ tube current, to compare with the feedback control of the input voltage VS ₄ of the actual inverter circuit 4 and which, as described above And the phase of the voltage and current of the single-phase AC power supply 30 are matched, and the input voltage VS of the inverter circuit 4 is
₄ so that the set value VS _3, the switching elements _131-134 of the first rectifier circuit 13 for switching control. The inverter circuit 4 converts the DC output of the first rectifier circuit 13 (smoothing capacitor 3), while controlling so tube voltage becomes a set value VS ₁ to a high frequency alternating current. That is, the phase difference and frequency control circuit 12 detects the detected values VS ₂ and IS ₂ of the tube voltage and the tube current and the set values V
S ₁ and IS ₁ are input, and for the tube voltage, the frequency of the inverter circuit 4 and the phase difference between the switching elements 41 and 44 and the phase difference between 42 and 43 are feedback-controlled so that the tube voltage becomes the set value VS ₁ . This phase difference and frequency control circuit 1
2 is amplified by the second gate drive circuit 11 and applied to the gates of the switching elements 41 to 44 of the inverter circuit 4 to drive them. These from the inverter circuit 4, while controlling so tube voltage becomes a set value VS _1, the first rectifier circuit 13 (the smoothing capacitor 3)
Is converted to a high-frequency alternating current. The control of the tube current is performed by controlling the heating amount of the filament of the X-ray tube 8. Next, at the time of photographing, when photographing conditions are set on the console 32, the fluoroscopic ON signal is output from the current / voltage control circuit 17
Not input to which the output of the gate drive circuit 16 is turned off, the switching element _131-134 of the first rectifier circuit 13 is kept off. That is, at the time of photographing, the first rectifier circuit 13 forms a single-phase full-wave rectifier circuit of diodes D _{1 to} D ₄ , and a voltage obtained by smoothing the full-wave rectified voltage of the AC power supply 30 with the smoothing capacitor 3 This is the input voltage. Then, the phase and the frequency of the inverter circuit 4 are controlled in the same manner as described above so that the tube voltage and the tube current according to the photographing conditions are obtained. Accordingly, since the time of photographing photographing time is very short (approximately 0.1 seconds), without a pulse width modulation control of the switching elements _131-134 as during fluoroscopy effect on power than during fluoroscopy small. As described above, in the apparatus of the present invention, the voltage of the AC power supply 30 and the current are in phase, the power factor is 1, and the current can be controlled to a sine wave. And also eliminates power supply harmonic interference. In particular, a single-phase 100
By applying the present invention to a case where light is irradiated from a power supply having a small capacity of V, several kVA for a long time such as during fluoroscopy, it is possible to greatly improve the power factor and reduce power supply harmonics.
The load on the power supply can be significantly reduced. Further, in the case of a load having a low tube voltage and a small tube current, conventionally, the input voltage of the inverter circuit 4 is controlled to be equal to or less than the peak value of the power supply voltage by the thyristor of the single-phase full-wave rectifier circuit 2 in FIG. Although the inverter circuit 4 is controlled only by the phase difference, in the present invention, not only the phase difference of the inverter circuit 4 but also the frequency is controlled to expand the control range of the inverter circuit 4, so that a wide range Can respond to. In the embodiment shown in FIG. 1, an example has been described in which the switching elements 13 _{1 to} 13 ₄ and the diodes D _{1 to} D ₄ of the first rectifier circuit are individually used. If used, the diode D ₁₁ to D ₁₄ in the module series as shown in FIG. 6, may be connected to D ₁₅ to D ₁₈ in parallel. That is,
Since the anti-parallel diode D ₁ to D ₄ of the switching element _131-134 is built to the present invention is used only during fluoroscopy, as the diode D ₁ to D ₄ are not conducting at the time of shooting, and this in the opposite direction to connect the diode D ₁₁ to D _14,
Inputs the full-wave rectification voltage of the AC power supply voltage by the diode D ₁₅ to D ₁₈ in the inverter circuit at the time of photographing. By doing so, the switching elements 13 _{1 to} 13 ₄
In the power module including the diodes D _{1 to} D _4, an element having a small current rating can be used according to the power at the time of fluoroscopy, so that a more economical device can be realized. The first rectifier circuit of the embodiment shown in FIGS. 1 and 6 has been described with respect to an example in which a self-extinguishing switching element is used for all arms of a full bridge.
Alternatively, as shown in FIG. 8, two arms on the AC side or two arms on the DC side
It may be used only for the arm. By doing so, in addition to obtaining substantially the same effects as in the above embodiment, a more economical device can be provided. As described above, according to the present invention, the voltage and the current of the AC power supply have the same phase and the power factor is 1, the apparent power is reduced, the power supply equipment capacity is reduced, and the power supply is reduced. Equipment costs and electricity charges can be saved. Further, since the waveform of the power supply current also becomes a sine wave, power supply harmonic interference is eliminated. In particular, when a power supply of 100 V AC and several kVA is used as in a mass examination device for stomach, these advantages are exhibited more.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing one embodiment of the device of the present invention. FIG. 2 is a diagram showing a specific example of a current and voltage control circuit in FIG. 1 together with peripheral circuit portions thereof. FIG. 3 is a waveform diagram of a current of a single-phase AC power supply and a pulse width modulation signal in FIG. 2; FIG. 4 is a circuit diagram of a conventional device. FIG. 5 is a waveform diagram of current and voltage of a single-phase AC power supply in a conventional device. FIG. 6 is a circuit diagram showing another embodiment of the device of the present invention. FIG. 7 is a circuit diagram showing another embodiment of the device of the present invention. FIG. 8 is a circuit diagram showing another embodiment of the device of the present invention. [Description of Signs] 1 AC reactor 2 Single phase by thyristor 3 Smoothing capacitor 4 Full-bridge type inverter circuit using IGBT 5 Resonance capacitor 6 High voltage transformer 7 High voltage rectifier circuit 8 X-ray tube 11 Gate drive circuit ( Second gate drive circuit) 12 Phase difference of inverter circuit, frequency control circuit 13 First rectifier circuit (single-phase full-wave rectifier circuit using IGBT) 14 Current detector of single-phase AC power supply 15 Voltage detection of single-phase AC power supply Device 16 first gate drive circuit 17 current for controlling the current of the AC power supply and the output voltage of the first rectifier circuit, voltage control circuit 20 single-phase sine wave generator 21 error amplifier 22 multiplier 23 error amplifier 24 sawtooth wave Generator 25 Comparator 30 Single-phase AC power supply 32 Operation console

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) H05G 1/00-2/00 Practical file (PATOLIS) Patent file (PATOLIS)

Claims (1)

(57) [Claim 1] A first rectifier circuit for rectifying an AC power supply,
A smoothing capacitor for smoothing the output voltage of the first rectifier circuit, an inverter circuit for converting the output of the smoothing capacitor into a high-frequency AC, a high-voltage transformer for boosting the output voltage of the inverter circuit, A second rectifier circuit for rectifying the output of the transformer, wherein the output voltage of the second rectifier circuit is applied to an X-ray tube to generate X-rays. Rectifier circuit is constituted by a full-wave bridge including at least two or more connected bodies of a switching element capable of self-extinguishing and a diode connected in anti-parallel with the switching element. With an AC reactor in between,
Only during fluoroscopy, the switching element of the first rectifier circuit is subjected to pulse width modulation control according to the phase difference between the current and voltage of the AC power supply and the set value of the output voltage of the smoothing capacitor, and the current of the AC power supply is controlled. And control the output voltage of the smoothing capacitor to a set value.
Current, comprising a voltage control circuit, the switching device is an inverter type X-ray high voltage apparatus, characterized in that left off at the time of shooting.