JP3736917B2 - Inverter X-ray high voltage device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter type X-ray high voltage apparatus, in particular, an X-ray high voltage apparatus for converting a direct current from a direct current power source into an alternating current using an inverter, boosting it, supplying it to an X-ray tube and emitting X-rays. The present invention relates to an inverter type X-ray high voltage apparatus suitable for preventing interruption of X-ray irradiation due to a slight discharge of a ray tube and preventing interruption of inspection and re-inspection.
[0002]
[Prior art]
The discharge of the X-ray tube includes a large discharge that reaches the end of life and a small discharge that does not reach the end of life (fine discharge). When this discharge occurs, the short circuit between the anode and cathode of the X-ray tube, or the short circuit between the anode and ground or the cathode and ground, that is, the secondary side of the high voltage transformer is short circuited, and the output current of the inverter increases rapidly. Depending on the case, the switching element of the inverter circuit may be thermally destroyed. For this reason, the current (tube current) flowing through the X-ray tube and the inverter output current are detected (not shown), and when this exceeds a predetermined value, it is regarded as an overcurrent and the discharge of the X-ray tube is detected, and the inverter circuit The method of stopping X-ray emission was stopped.
[0003]
However, many of the above discharges are fine discharges that do not reach the end of their lives, and in many cases, the above-mentioned overcurrent detection level is not reached by this fine discharge.
In this case, since the tube voltage feedback control is performed so that the actual tube voltage becomes the set tube voltage, in order to control the tube voltage suddenly dropped by this slight discharge (a in FIG. 4) to become the set tube voltage. As soon as the fine discharge is completed (b in FIG. 4), the tube voltage rapidly increases.
[0004]
Accordingly, the tube voltage overshoots as shown in FIG. 4c to become an overvoltage, and an overvoltage detection circuit (not shown) for detecting an abnormality of this voltage is operated to stop the X-ray emission. .
[0005]
[Problems to be solved by the invention]
As described above, the X-ray emission is stopped even in the case of a fine discharge that does not reach the life of the X-ray tube in the conventional method. Therefore, imaging is performed in accordance with the injection of the contrast agent, such as an angiographic examination using a contrast agent. When performing such a fine discharge, if an error occurs during imaging and the examination is interrupted, the examination will be re-examined, resulting in a great burden on the patient.
[0006]
Therefore, it is desired that photographing can be continuously performed with a fine discharge below an overcurrent detection level that does not require protection of the apparatus.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to continue photographing with a fine discharge below an overcurrent detection level.
[0007]
[Means for Solving the Problems]
The purpose is to provide a direct current power supply, an inverter that converts direct current from the direct current power supply into alternating current, a high voltage transformer that boosts the alternating voltage from the inverter, and a high voltage that rectifies the output voltage of the high voltage transformer. A rectifier, an X-ray tube that emits X-rays when a DC voltage is applied from the high-voltage rectifier, and a tube voltage that is connected to the X-ray tube and detects a voltage (abbreviated as tube voltage) of the X-ray tube A detector, a tube voltage for controlling the inverter so that at least a desired target tube voltage signal and a tube voltage detection signal from the tube voltage detector are inputted, and the tube voltage of the X-ray tube becomes a desired tube voltage. in the inverter type X-ray high voltage apparatus, comprising: a feedback control unit, and a weak discharge detecting means for detecting a weak discharge of the X-ray tube overcurrent detection level below that protection does not require the device, this weak discharge End of A weak discharge end detecting means for detecting until said detects the end of the weak discharge in the fine discharge detecting means Teka detects weak discharge al the weak discharge end detecting means, the weak discharge detection starting tube voltage feedback control amount a tube voltage control amount holding means for holding the previous value, is achieved by having a.
[0008]
The tube voltage control amount for controlling the actual tube voltage output from the tube voltage feedback control device to be the set tube voltage is normally left as it is so that no discharge occurs, and the discharge signal is output from the discharge detection means. Is input, the tube voltage control amount is held and the feedback circuit input is shut off to stop the feedback control process.
[0009]
When the discharge is finished and the discharge end signal is input from the discharge end detection means, the hold of the tube voltage control amount is released, and the feedback of the tube voltage control amount is output by connecting the input of the feedback circuit. To do.
[0010]
According to the above, even if a slight discharge occurs, the output of the inverter is kept in the state at the time of the discharge occurrence, and the feedback control process is stopped, and the X-ray irradiation can be continued without increasing the inverter output after the discharge is finished. Can continue shooting.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention using a microcomputer, and FIG. 3 is a flowchart showing the operation of FIG.
[0012]
First, the outline of the configuration and operation of the present invention will be described with reference to FIG.
1 is a DC power source, 2 is an inverter that converts this DC power source into high-frequency AC, 3 is a high-voltage transformer that boosts the output voltage of the inverter 2, and 4 is a high-voltage rectifier that rectifies the output voltage of the high-voltage transformer, Reference numeral 5 denotes an X-ray tube that applies the output voltage of the high-voltage rectifier and emits X-rays, and 6 is a tube voltage detector that detects the voltage of the X-ray tube.
[0013]
The actual tube voltage detected by the tube voltage detector 6 is input to the feedback circuit 12 through the sample hold A7, the comparison unit A8, the comparison unit B9, and the switch circuit 13.
[0014]
The sample hold A7 samples and stores the actual tube voltage by the clock signal that determines the inverter operating frequency from the control unit 14, and holds it for one period of the inverter clock signal.
[0015]
The comparison means A8 compares the current tube voltage with the output of the sample hold A7, checks the amount of change in the tube voltage during one cycle of the inverter clock signal, and resets the flip-flop 10 if the difference is small, Continue normal control.
[0016]
If the drop of the tube voltage is large during one period of the inverter clock signal, the flip-flop 10 is set. Thereby, the start of the fine discharge is detected.
The comparison means B9 compares the actual tube voltage with the set tube voltage value from the control unit 14, and resets the flip-flop 10 if the actual tube voltage is high or the difference is small.
Thereby, it is checked whether or not the operation is normal.
[0017]
Normally, the flip-flop 10 is reset, the switch circuit 13 is turned on, the set tube voltage value and the actual tube voltage from the control unit 14 are input to the feedback circuit 12, and the sample hold B11 is fed back to the feedback circuit 12. Is output to the inverter circuit 2 as it is.
[0018]
When the tube voltage drops abruptly due to the slight discharge and the flip-flop 10 is set, the switch circuit 13 is turned OFF, and the actual tube voltage that is input to the feedback circuit 12 and the set tube voltage value from the control unit 14. The sample hold B11 holds the tube voltage control amount so far.
[0019]
Next, an embodiment in which such an operation is realized by the microcomputer 200 will be described with reference to FIGS. In FIG. 2, a CPU 201 for controlling various operations, an AD converter 202 for converting an actual tube voltage detected by the tube voltage detector 6 into a digital quantity, a ROM 203 for storing a program for the CPU 201, and a program for the CPU 201 are operated. A necessary RAM 204 and a DA converter 205 that converts a tube voltage control amount into an analog amount and outputs the analog amount are configured. Using the microcomputer 200 having such a configuration, the present invention is processed based on the flowchart shown in FIG.
[0020]
The operation will be described below with reference to the flowchart of FIG. The process shown in FIG. 3 is started in synchronization with the inverter clock signal, and is executed once in one cycle of the inverter clock signal.
(A) Step 301
The actual tube voltage is input after AD conversion.
(B) Step 302
When the actual tube voltage is compared with the set tube voltage value and the actual tube voltage is low and the difference from the set tube voltage is large (for example, 5 kV or more), the process proceeds to step 304 (possibility of occurrence of discharge). If so, the process proceeds to step 303 (no discharge occurs).
(C) Step 303
The discharge flag is reset (OFF) and set to perform tube voltage feedback control processing.
(D) Step 304
When the actual tube voltage is input at the previous step 301 when it was activated last time and compared with the previous actual tube voltage stored at the previous step 306, the actual tube voltage is greatly lower than the previous time (for example, 5 kV or more). The process proceeds (discharge occurs).
(E) Step 305
The discharge flag is set (ON), and the tube voltage control amount is set to be output without performing the tube voltage fordback.
(F) Step 306
The actual tube voltage is saved for use in step 304 the next time it is activated.
(G) Step 307
If the discharge flag is OFF, the process proceeds to step 308, and if it is ON, the process proceeds to 311.
(H) Step 308
Performs tube voltage feedback calculation (for example, proportional / integral / derivative feedback calculation).
(I) Step 309
The tube voltage control amount calculated in step 308 is saved for use in the next activation or subsequent step 311.
(J) Step 310
The tube voltage control amount calculated in step 308 is output to the DA converter, and the process ends.
(K) Step 311
The tube voltage control amount saved in the previous activation or previous step 309 is output to the DA converter, and the process is terminated.
[0021]
As described above, when a slight discharge below the overcurrent detection level occurs in the X-ray tube (point 5-a in FIG. 5) and a sudden drop in tube voltage due to the small discharge is detected (step 304), feedback control processing is performed. The operation is stopped and the tube voltage control amount to the inverter circuit 2 is held at the value at the time when the slight discharge occurs.
[0022]
Therefore, when the tube voltage is lowered and the fine discharge is finished (point in FIG. 5B) and the fine discharge is stopped, the tube voltage is recovered to the value at the time of occurrence of the discharge.
When it is detected (step 302) that the tube voltage has recovered to near the set value (point d in FIG. 5), the feedback control process is resumed.
[0023]
As described above, in the apparatus of the present invention, since the slight discharge which does not reach the life of the X-ray tube is detected by the change amount of the tube voltage and the tube voltage control is continued, the radiographing is performed without stopping the X-ray emission. Can do.
[0024]
In the first and second embodiments, the amount of change in the tube voltage is used to detect the slight discharge. However, the present invention is not limited to this, and the tube current and the physical quantity corresponding thereto may be detected.
For example, when the tube current is used, the tube current at the time of the fine discharge becomes larger than the normal tube current, so that the detection point is set slightly larger and detected.
[0026]
【The invention's effect】
As described above, according to the present invention , since the radiographing is continued in the slight discharge below the overcurrent detection level that does not require the protection of the apparatus , the radiographing can be performed without stopping the X-ray emission. This has the effect of preventing inspection interruption and re-inspection.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a block diagram showing a second embodiment of the present invention.
FIG. 3 is a flowchart showing the operation of FIG. 2;
FIG. 4 is a tube voltage waveform diagram at the time of conventional fine discharge.
FIG. 5 is a tube voltage waveform diagram during slight discharge in the present invention.
[Explanation of symbols]
1 DC power supply 2 Inverter 3 High voltage transformer 4 High voltage rectifier 5 X-ray tube 6 Tube voltage detector 7 Sample hold A
8 Comparison means A
9 Comparison means B
10 Flip-flop 11 Sample hold B
12 Feedback Control Device 13 Switch Circuit 14 Control Unit 201 CPU
202 AD converter 203 ROM
204 RAM
205 DA converter

Claims (1)

A direct current power supply, an inverter that converts direct current from the direct current power supply into alternating current, a high voltage transformer that boosts the alternating voltage from the inverter, a high voltage rectifier that rectifies the output voltage of the high voltage transformer, and An X-ray tube that emits X-rays when a DC voltage from a high-voltage rectifier is applied; a tube voltage detector that is connected to the X-ray tube and detects a voltage (abbreviated as tube voltage) of the X-ray tube; Tube voltage feedback control means for controlling the inverter so that at least a desired target tube voltage signal and a tube voltage detection signal from the tube voltage detector are input and the tube voltage of the X-ray tube becomes a desired tube voltage ; in the inverter type X-ray high voltage apparatus and a weak discharge detecting means for detecting a weak discharge of the X-ray tube overcurrent detection level below that protection does not require the device, detecting the end of this weak discharge fine to A conductive end detecting means, wherein in the fine discharge detecting means Teka detects weak discharge al the weak discharge end detecting means to the detection of the end of the weak discharge, a tube voltage feedback control amount the weak discharge detection start previous value An inverter type X-ray high voltage apparatus, comprising:

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