JPH04284399A - Inverter type x-ray device - Google Patents

Abstract

PURPOSE:To stabilize X-ray output by providing a power source impedance measurement circuit for measuring the impedance of AC power source from device input voltage as well as input current. CONSTITUTION:Device input voltage as well as input current are detected by a power source impedance measurement circuit 12 through an insulating amplifier 13 and a current transformer 14, respectively. These outputs are converted into digital mode, and are stored in a digital storage circuit 15. Power source impedance is calculated by a no-load input calculation circuit 16 obtained by the circuit 15 based on the ratio of the difference between voltage effective value and a no-load input current effective value. When the input voltage of an inverter 5 is reduced, an X-ray condition that does not saturate inverter control parameter in a feedback circuit 11 is set. Since the saturation of the inverter control parameter is prevented, accuracy and reproducibility of X-ray output is improved.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an inverter-type X-ray apparatus equipped with an inverter that rectifies AC output from an AC power source and converts it into AC, and a feedback circuit that stabilizes the output voltage of this inverter. It is.

0002

[Prior Art] Generally, an inverter-type X-ray device is equipped with a feedback circuit that stabilizes the output voltage of the inverter, and even if the power supply voltage drops before or during X-ray exposure, the feedback function works and the X-ray It has a function that keeps the output constant.

However, if the power supply voltage drops beyond the limit of the feedback function, the accuracy and reproducibility of the X-ray output may be lost.

In order to prevent this phenomenon, conventional inverter type X-ray equipment measures the effective value of the AC power supply voltage (input voltage) at no load immediately before X-ray irradiation to detect a drop in the input voltage. By interlocking the exposure signal, X-ray exposure was prevented and the accuracy and reproducibility of X-ray output were prevented from deteriorating.

[0005] However, this method cannot estimate the drop in input voltage after the start of exposure, which varies depending on the output X-ray conditions, so the interlock boundary level is determined by assuming the voltage drop at the heaviest load. However, there is a problem in that it actually limits the range of X-ray conditions that can be output.

[0006] Here, the reason why it is not possible to estimate the drop in input voltage only from the AC power supply voltage under no load will be explained. If the inverter performs output adjustment such as phase difference control or pulse width control to feedback control the output voltage, even if the AC power supply voltage decreases and the inverter input voltage decreases, the inverter will maintain its own control parameters. Try to stabilize the output voltage by changing it. In other words, when viewed from the power supply side, it exhibits the characteristics of a constant power load. At this time, the input current of the inverter increases, so there is a reactance component X on the power supply side.
If s is present, the power supply voltage will further decrease. In other words, the input voltage drop necessary for the inverter varies depending on the impedance of the power supply, that is, the installation location, and its value is known only when it is under load, that is, when X-rays are exposed.

[0007] From these facts, it can be seen that the input voltage drop necessary for the inverter cannot be estimated only from the power supply voltage at no load, and it is necessary to accurately grasp the impedance of the power supply.

[0008] Conventionally, however, the impedance of the AC power source of the equipment was calculated by estimating it from the capacity of the power transformer and the thickness and length of the distribution line (general rules for medical X-ray high voltage equipment).
JISZ 4702), these are often unknown.

Furthermore, in reality, the impedance of the power supply varies depending on the spatial arrangement of the distribution lines, and the actual measured value often differs from the calculated value. Even when measuring this, regular voltmeters and ammeters require time to calculate the effective value of the measured value, so continuing to operate the X-ray equipment during that time places a burden on the X-ray tube. (overload) is the problem.

[0010] In addition, the method using a resistive load, which is often used when measuring power source impedance, requires a large amount of power to be consumed, so a resistor with an extremely large capacity is required, and measurements must be taken at each location where the X-ray equipment is installed. That was actually difficult.

[0011]

[Problem to be Solved by the Invention] Due to these circumstances, in the above-mentioned prior art, the power supply equipment at the location where the X-ray device is installed,
In particular, depending on the power supply voltage, the device may not work, or even if it does work, it may not be possible to obtain X-ray output with accuracy higher than a predetermined level (minimum necessary for diagnosis), or it may require a great deal of effort and time. There was a problem that it was necessary.

[0012] These things are especially true when it is necessary to use an X-ray device, such as in an emergency, and when it is sufficient to have the minimum level of accuracy required for diagnosis (more accurate than high accuracy). (If there is a strong need for urgency)
However, it could not be used in practice, and there were problems in terms of its ability to respond to emergency shooting.

[0013] An object of the present invention is to easily set X-ray conditions with at least the minimum degree of accuracy required for diagnosis even if the power supply equipment at the location where the equipment is installed, especially its power supply voltage status, cannot be known in advance. An object of the present invention is to provide an inverter-type X-ray device that can improve the ability to respond to emergency imaging, especially when the X-ray device must be used in an emergency.

[0014]

[Means for Solving the Problems] The above object is to provide a rectifier circuit that rectifies AC output from an AC power source, an inverter that converts the rectified output of this rectifier circuit to AC, and feedback that stabilizes the output voltage of this inverter. In an inverter-type X-ray apparatus equipped with a circuit, by providing a power supply impedance measurement circuit that detects the apparatus input voltage and input current, converts them into digital values and calculates them, and measures the impedance of the AC power supply. achieved.

[0015] In addition to the above-mentioned power source impedance measurement circuit, the above object is to provide a new system that adjusts the set values of the tube current and imaging time when the input voltage of the inverter decreases, and prevents the inverter control parameters in the feedback circuit from becoming saturated. an X-ray condition adjustment means for setting X-ray conditions, and an X-ray condition change display means for displaying that the X-ray conditions have been changed to new X-ray conditions by the X-ray condition adjustment means; This can be achieved more satisfactorily by providing an X-ray condition display means for displaying the new X-ray conditions set by the adjustment means.

[0016]

[Operation] The power source impedance measuring circuit instantaneously measures the impedance of an AC power source by digital calculation. If you adjust the X-ray conditions based on this measurement result,
Even if the power supply equipment at the location where the X-ray device is installed, especially its power supply voltage state, cannot be known in advance, it is possible to easily set the X-ray conditions with at least the minimum degree of accuracy required for diagnosis.

The power supply impedance measuring circuit includes an apparatus input voltage detector and an input current detector within the X-ray apparatus. The instantaneous waveforms of these detector outputs are stored in a memory, and the effective values at no-load and under load are calculated from these instantaneous waveforms.

The effective value of the no-load power supply voltage before X-ray exposure is Vso, and the effective value of the loaded power supply voltage during X-ray exposure is VsL.
Assuming that the input current of the power supply during load is IsL, the impedance Zs of the power supply can be expressed as shown in the following equation (1).

Zs = (Vso-Vs
L)/IsL・
(1) From this, by simply outputting X-rays once when the X-ray device is installed, the device can measure the voltage and current of the power supply and estimate the power supply impedance of the power supply system. If there is a change in the power supply system, such as when another X-ray device is installed, measurements can be taken again each time.

Next, the power that the X-ray device can output is Pma
x, the efficiency (output power/input power) of the X-ray device is η, and the maximum value of the current that can be supplied from the power source is IsLmax, then the following equation (2) holds true.

Pmax=η{Vso
IsLmax −Zs IsLmax 2 } ・・
-(2) The second term on the right side of this equation (2) represents the power drop due to power supply impedance.

Maximum value Im of tube current that can be output by the X-ray device
ax can be expressed as in the following equation (3), where the set value of the tube voltage is Vset.

Imax=Pmax
/Vset
(3) From this equation (3), the maximum value of the tube current that can be output in the power supply equipment in which the X-ray apparatus is installed can be determined according to the set tube voltage. X to use
If the tube current condition limited by the ray tube or X-ray device is smaller than ImaX, that value takes precedence.

[0024] As a result, the allowable load range of the X-ray device can be automatically determined according to the power supply equipment at the location where the X-ray device is installed, so the maximum X-ray conditions that can be output with the current power supply voltage can be accurately calculated. X
Accuracy and reproducibility of line output are improved.

Further, the X-ray condition adjustment means adjusts the set values of the tube current and imaging time when the input voltage of the inverter decreases, and sets new X-ray conditions that do not saturate the inverter control parameters in the feedback circuit. do.

[0026]The X-ray condition change display means displays that the X-ray condition adjustment means has changed to a new X-ray condition, or the X-ray condition display means displays that the X-ray condition adjustment means has changed to a new X-ray condition. The new X-ray conditions will be displayed. According to this, it becomes possible to respond more quickly in an emergency or the like.

[0027]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an inverter type X-ray apparatus according to the present invention. In this Figure 1, 1
is a commercial AC power supply, which is shown in the figure as an ideal AC voltage source 1a with an impedance (Zs) 1b added thereto. This impedance 1b is the ideal AC voltage source 1
The impedances of distribution transformers, distribution lines, etc. existing between a and the X-ray device power supply connection terminals 2 and 3 are collectively shown as power supply impedance Zs. 4 is a rectifier circuit that rectifies the AC output from the AC power supply 1; 5 is an inverter that converts the rectified output of the rectifier circuit 4 into high-frequency AC; 6 is a high-voltage transformer that boosts the output voltage of the inverter 5; 7 8 is a high-voltage rectifier that rectifies the output of the high-voltage transformer 6, and 8 is an X-ray tube to which the rectified output of the high-voltage rectifier 7 is applied. Reference numeral 9 denotes a voltage divider for detecting tube voltage, which together with a comparator 10 forms the main component of a feedback circuit 11 that stabilizes the output voltage of the inverter 5.

12 is the impedance 1 of the AC power supply 1
A power supply impedance measurement circuit that measures b, an isolation amplifier 13 that detects the device input voltage (AC input voltage), and a current transformer 14 that detects the device input current (AC input current),
These outputs are time-divided during no-load and load times,
A digital storage circuit 15 that stores digital data, and a ratio of the difference between the effective value of input voltage at no load and the effective value of input voltage at load obtained by this digital storage circuit 15 and the effective value of input current at load to calculate the power supply impedance. and an arithmetic circuit 16 for calculation.

Here, the digital storage circuit 15 includes a multiplexer 17, an oscillator 18, an A/D transformer 19, a RAM (random access memory) 20 and a C
The arithmetic circuit 16 is composed of the CPU 21. 22 is an EPROM that stores the calculated power supply impedance Zs.

23 is an operating device, here a display device 24
and an X-ray control device 25. This X-ray control device 25 has the same configuration as the conventional device, and here, when the input voltage of the inverter 5 decreases, the set values of the tube current and imaging time are adjusted, and the feedback circuit 11 An X-ray condition adjusting means is provided for setting new X-ray conditions that do not saturate the inverter control parameters. The display device 24 has the same configuration as the conventional device, and includes an X-ray condition change display means for displaying that the X-ray condition adjustment means has changed to a new X-ray condition, and the X-ray condition adjustment means. New X set by means
and X-ray condition display means for displaying the X-ray conditions.

Next, the operation will be explained. The AC voltage Vs inputted from the power supply connection terminals 2 and 3 is converted into DC by the rectifier circuit 4, and the inverter 5 converts it into high frequency AC.

The converted high frequency alternating current is transferred to a high voltage transformer 6.
After being boosted by the high-voltage rectifier 7, the voltage is converted to direct current again by the high-voltage rectifier 7, and then applied to the X-ray tube 8 as a tube voltage. This tube voltage is detected by a voltage divider 9 and compared with a tube voltage set value Vset by a comparator 10. The feedback circuit 11 functions so that the two match, the control parameters of the inverter 5 are changed, and the output is stabilized.

[0033] Here, the AC input current Is is
is detected and converted into a voltage as appropriate. Further, the AC input voltage Vs is detected by the isolation amplifier 13 while being isolated from the power supply wiring, and then outputted as an appropriate voltage. These Vs and Is are input to the multiplexer 17, and the multiplexer 17 outputs Vs when the output of the oscillator 18, which is oscillating at a frequency sufficiently higher than the power supply frequency, is H, and similarly outputs Is when it is L. Output.

The output of the multiplexer 17 is an analog value, which is converted into a digital value by the A/D converter 19 and sent to the CPU 21. A/D converter 19, C
Both PU21 operates in synchronization with the output of the oscillator 18, and the CP
U21 divides the alternately received Vs and Is data into two and sequentially sends them to two areas in the RAM 20.
Memorize each. The two areas Vs and Is in the RAM 20 always have a capacity to store data for two cycles of the AC power supply 1, and as soon as they become full, data is replaced starting from the first area.

When the X-ray exposure signal EXP is input to the CPU 21, data acquisition is stopped after one cycle from that point. Therefore, data for one cycle before the start of exposure and one cycle after the start of exposure are saved. That is, the state of the AC power supply 1 during no load and under load can be maintained.

The CPU 21 calculates the root mean square value of the instantaneous values of Vs and Is at each time, ie, the effective values VsL and IsL, for the first half cycle of the power supply after the input of the X-ray exposure signal EXP. Similarly, the X-ray exposure signal EX
Also for the last half cycle before P input, the effective value of Vs
Calculate o. However, the half cycle of the power supply is the period from the first zero cross of the voltage waveform to the next zero cross.

FIG. 2 shows a time chart of the measurement period of the effective values (VsL, IsL, and Vso). In FIG. 2, VsL is the effective value measurement period of Vs for the first half cycle of the power supply after the X-ray exposure signal EXP is input;
IsL is the effective value measurement period of Is for the first half cycle of the power supply after the X-ray exposure signal EXP is input, and Vso is
Vs also for the last half cycle before inputting the radiation exposure signal EXP.
is the effective value measurement period.

The power supply voltage Vso at no load, the power supply voltage VsL at load, and the power supply current IsL measured in this way
From this, the CPU 21 calculates the power supply impedance Zs using the above equation (1). This value is unique to each power supply equipment, so it shows the same value even if the voltage or current is different. Therefore, in order to save the calculation time from the next time, the above Z
s as EPRO, which is a rewritable non-volatile memory.
Store it in M22. This work only needs to be done once when installing the X-ray apparatus, and thereafter there is no need to do it unless there is a change in the AC power supply system.

Next, in the CPU 14, the equations (2) and (3) shown above are used.
), the maximum tube current value Imax that can be currently output is calculated. At this time, the above Zs uses a value stored in the EPROM 22, and the above η and IsLmax are values determined by the X-ray apparatus. Further, the no-load power supply voltage Vso is constantly detected and the latest value is used.

[0040] This operation is automatically performed before each X-ray irradiation. Furthermore, even when the X-ray conditions are changed, this operation is automatically performed to confirm whether the new conditions can be output. If at these points, this calculation result is
If the value is smaller than the permissible X-ray conditions determined by the X-ray device, the display device 24 of the operating device 23 displays that output cannot be performed due to the conditions of the power source 1, and the operator is notified. Furthermore, I, which is the maximum tube current that can be output at this point,
max is displayed on the display device 24 as a new set tube current value, and the set time is also changed so that the set mAs becomes the same as the old set value. These are performed by the X-ray condition adjustment means provided in the X-ray control device 25, the X-ray condition change display means and the X-ray condition display means provided in the display device 24.

Note that the CPU 21 in FIG. 1 is a DSP (Digital Signal P
If the feedback for stabilizing the output of the inverter 5 is also digitally controlled,
Faster operation is possible.

Further, in the above embodiment, the inverter 5 is used as an AC converting means for converting the rectified output of the rectifier circuit 4 into AC.
Although the explanation was given using a circuit using only a rectifier circuit 4 as an example, the rectifier circuit 4
Of course, the present invention can also be applied to a so-called PAM (Pulse Amplitude Modulation) circuit configuration in which a chopper circuit is provided between the AC converter and the inverter 5 to serve as the AC converting means, and the output voltage is stabilized. It is.

According to the above embodiment, the maximum X-ray conditions that can be output with the current power supply voltage are accurately calculated, so there is no unnecessary restriction on exposure, and saturation of the inverter control parameters is prevented. This has the effect of improving the accuracy and reproducibility of X-ray output.

[0044]

[Effects of the Invention] According to the present invention, the impedance of the AC power supply at the location where the X-ray device is installed is automatically measured, and it is possible to easily know the permissible range of the X-ray conditions according to the power supply equipment. The maximum X-ray conditions that can be output with a power supply voltage of 2 are accurately calculated, eliminating unnecessary restrictions on exposure. Therefore, even if the power supply equipment at the location where the equipment is installed, especially its power supply voltage status, cannot be known in advance, it is possible to set the X-ray conditions with at least the minimum degree of accuracy necessary for diagnosis, especially in an emergency. This has the effect of improving the ability to respond to emergency imaging in cases where the use of an X-ray device is unavoidable.

Furthermore, according to the X-ray condition adjustment means, saturation of the inverter control parameters can be prevented, so the accuracy and reproducibility of the X-ray output is improved. According to the means, effects such as being able to respond more quickly in an emergency etc. can also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the device of the present invention.

FIG. 2 is a time chart for explaining the operation of the device of the present invention.

[Explanation of symbols]

1 Commercial AC power supply 4 Rectifier circuit 5 Inverter 8 X-ray tube 11 Feedback circuit 12 Power supply impedance measurement circuit 13
Isolation amplifier (equipment input voltage detector) 14 Current transformer (equipment input current detector) 15 Digital storage circuit 16 Arithmetic circuit (CPU 21) 24 Display device (X-ray condition change display means, X-ray condition display means)

Claims (4)

[Claims] [Claim 1] A rectifier circuit that rectifies AC output from an AC power source, and a rectifier circuit that converts the rectified output of the rectifier circuit into AC.
In an inverter-type X-ray apparatus equipped with at least an AC converter equipped with an inverter and a feedback circuit that stabilizes the output voltage of the AC converter, the input voltage and input current of the apparatus are detected and converted into digital values. An inverter-type X-ray apparatus characterized by comprising a power source impedance measurement circuit that converts and calculates and measures the impedance of the AC power source. 2. The power supply impedance measurement circuit comprises:
A device input voltage detector and an input current detector, and the outputs of both these detectors are time-divided during no-load and load times,
A power supply impedance is calculated using a digital storage means for storing digital data, and a ratio of the difference between the effective value of input voltage during no-load and the effective value of input voltage during load obtained by this digital storage means and the effective value of input current during load. An inverter-type X-ray apparatus comprising calculation means. 3. X-ray condition adjustment means for adjusting set values of tube current and imaging time when the input voltage of the inverter decreases, and setting new X-ray conditions that do not saturate the inverter control parameters in the feedback circuit. and an X-ray condition change display means for displaying that the X-ray condition adjustment means has changed to a new X-ray condition. . 4. X-ray condition adjustment means for adjusting set values of tube current and imaging time when the input voltage of the inverter decreases, and setting new X-ray conditions that do not saturate the inverter control parameters in the feedback circuit. and an X-ray condition display means for displaying the new X-ray conditions set by the X-ray condition adjustment means. Device.