JPS598300A - X-ray generator - Google Patents

Abstract

PURPOSE:To properly control concentration of an X-ray photography and improve its reducibility by setting a switching circuit which can be cut-off at an arbitrary phase, and even if it is cut-off at an arbitrary phase, it can select a making phase and reduce exciting rush current of a high voltage transformer. CONSTITUTION:When a cut-off signal 71 is inputted in an a.c. switch 10, a thyristor 27 is ignited with a gate circuit 30, and a capacitor 26 is discharged to transfer the current of a thyristor 24 to a series circuit of a reactor 25, the capacitor 26, and the thyristor 27. When dischrge is finished and energy accumulated in the circuit is absorbed in the capacitor 26, the cut-off is completed. A synchronizing signal from a syncyronizing signal generator 13 is inputted into a making phase judging device 11, and a signal which delayed pi/2 with a delay circuit 11 is outputted into a counter and an AND circuit. When the cut-off signal 71 is inputted, a making phase is judged and is outputted into a making phase controller 12. Even if a circuit is cut-off at an arbitrary phase, a making phase is selected and magnetic flux density of a high voltage transformer is controlled so as to not greatly exceed steady values to reduce an exciting rush current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single-phase X-ray generator, and particularly to a single-phase X-ray generator equipped with a switch circuit that can be shut off at any phase.

A conventional single-phase X-ray generator is shown in FIG. In the figure,
1 is a commercial AC power supply; 2 is an autotransformer that adjusts the voltage applied to the X-ray tube 7; 3 and 4 are thyristors for opening/closing switches that control the application of voltage to the high-voltage transformer 5 for step-up; 7 is a rectifier circuit for full-wave rectification of the output of the high voltage transformer 5;
is an X-ray tube.

In the conventional device, a thyristor is used as an on/off switch element, so as shown in Figure 2, the thyristor remains on even if the irradiation signal is no longer present, and the output voltage (tube voltage) of ) in the same figure remains unchanged. could not be turned off until the polarity of the voltage was reversed. For this reason, especially when shooting with X
Even if the irradiation signal disappears when the photographic density of the radiograph becomes appropriate, the X-ray continues to be irradiated, resulting in overexposure.

An object of the present invention is to provide a single-phase X
To provide a line generator.

The problem that the switch circuit of the X-ray generator can be cut off at any phase can be handled by adding a Cyrisk forced commutation circuit or using a switching element with a self-extinguishing function. However, what poses the greatest problem when shutting off at an arbitrary phase is the excitation inrush phenomenon of the high-voltage transformer.

The magnetizing inrush phenomenon of a high-voltage transformer is a phenomenon in which the iron core of the high-voltage transformer undergoes magnetic saturation when power is applied to the high-voltage transformer, resulting in an excessive magnetizing inrush current. When the excitation inrush current flows, the magnitude of the input voltage decreases due to the voltage drop in the first source impedance, and therefore the output voltage decreases. The magnetic saturation of the iron core is closely related to the residual magnetic flux density BR of the iron core and the time integral of the applied voltage. For this reason, the residual magnetic flux of the iron core changes depending on the cutoff phase, so the phase of the applied RE pressure (
If the input phase and E1 phase are random, the excitation inrush phenomenon due to the magnetic saturation of the core will not occur, and the output will change every time an image is taken, resulting in a loss of reproducibility in X-ray images. .

The present invention attempts to reduce the influence of the magnetizing inrush direct current by selecting the turning on phase even when the turning off occurs at an arbitrary phase.

In order to suppress the magnetic saturation of the iron core, it is sufficient to prevent the magnetic flux density of the iron core from greatly exceeding the maximum value in the normal state. Since the magnetic flux density B is proportional to the time integral of the applied voltage,
As shown in FIG. 3, the phase is delayed by i from the applied voltage E. Therefore, when the magnetic flux density B is positive, that is, when the voltage phase is cut off at 1 to -π 2 , the voltage is turned on at a voltage phase π at which the magnetic flux density changes to negative. Further, when the magnetic flux density is negative, that is, when the voltage phase is cut off from π to 2π or from 0 to i, the voltage is turned on at the voltage phase 0 where the magnetic flux density B changes to positive. As described above, even if the power is cut off at an arbitrary phase, the magnetizing inrush current can be reduced by selecting the power-on phase so that the magnetic flux density does not greatly exceed a steady value.

π 3 In addition, the cutoff phase is set to 1 to -π and 2 to π2 2
The boundary of the cutoff phase that is divided into two other than 2 2 can be allowed within a range of about ±20% depending on the hysteresis characteristics of the iron core. Further, the input phase can also be selected within a range that does not affect the output voltage with respect to 0 and π.

FIG. 4 shows the configuration of a single-phase X-ray generator according to the present invention. In FIG. 4, 1o is an AC switch that can cut off alternating current at an arbitrary phase, 11 is a closing phase determiner that determines the closing phase, and 12 is a closing phase controller that controls the closing phase according to the output of 11. A synchronizing signal generator that outputs pulses when the phase of the input AC source is 0 and π. 1, 2.5 to 7 are included in the package shown in FIG. Further, 70 is a 1/V firing signal, 71 is a stop/off signal, 72 is a synchronization signal, 73 is an input phase trust signal, and 74 is a firing start signal.

FIG. 5 shows an example of an AC switch that can operate at any phase. 20 to 23 are rectifying elements, 24.27 are thyristors, 25 are reactors, 26 are capacitors, 2
8 is the charging circuit of 26, and 29° and 30 are the gate circuits.

In accordance with the exposure start signal 74, 24 is ignited by 29 and the circuit is closed. According to the cutoff signal 71, 2 by 3oVC
When 7 is ignited, 26 charged by 28 is discharged,
That energy generates 24 direct currents of 25.26°27
Transfer to a series circuit. When the discharge of 26 is completed and the energy stored in the circuit is absorbed by 26, step 101 is completed. Note that 75 is an AC i source.

FIG. 6 shows another embodiment of an AC switch that can be cut off at any phase. 20 to 23 are the same as those in Fig. 5, 40 is a controlled rectifier collector with a self-extinguishing function, and 41 is 4
This is a gate circuit for igniting and extinguishing 0. According to the exposure start signal 74 and cutoff signal 71, 41
0 is turned on and off.

FIG. 7 shows an embodiment of the closing phase controller.

51 is a counter that alternately outputs signals of "1" and 10 according to the output number 50; 52 to 56 are AND circuits;
57 is an OR circuit, 58 is "1" according to the set signal
This is a flip-flop that outputs "0" according to the reset signal.

FIG. 9 shows an embodiment of the closing phase determiner.

61 is a phase detector, 61a is a delay circuit that outputs a signal that is delayed by Σ compared to Irunotsuki δ, 61b is a counter of the same type as 51, 62.63 is an AND circuit, and 64 is the same as 58. It is a solid flop.

Next, the operation will be explained.

In FIG. 7, the υ synchronization signal a from 13 is input to 51. One output of 51 is ``1'' and 10'' according to a.
are alternately output to 52. The other output of 51 is the opposite output to the above output, that is, when the output is 11, it becomes 0.
","OJ's output "1" to 53. 52 and 5
:3 Since Ktd a is input, the output of 52 is the 81st! mb outputs a pulse to 54 only when the positive phase is 0, and 53 outputs a pulse when the voltage phase is π as shown in Figure 8C.
A pulse is output to 55 only at the throat. At this time, if the input phase signal is "l", the human power of one of the 54 is "0"
Therefore, the output of 54 is "0" and one input of 55 is "1", so the output C of 53 is directly converted to 15.
Output to 7. 571rl logical sum times M, so 55
output to 56. A pulse that is output only when the voltage phase is π is input to the terminal υ, 56.

When the exposure signal 70 is input to the set input of 58 at any time, the output of 58 becomes "1" as shown in FIG.
Output to 6. At this time, when a pulse is input from 57 to 56 when the voltage phase is π, 56 outputs a pulse and starts exposure tM 74. Fully ignite.

Note that if the input phase signal is "0", the output of 57 will be a pulse that is output only when the voltage phase is O, so the exposure start signal 74 will be the first one after the exposure signal 70 is input. It is output when the phase of the voltage becomes 0.

The cutoff signal 71 is input at 10°11, as shown in FIG. 10, the circuit is opened according to the cutoff signal 71. On the other hand, at 11, the synchronization signal a from 13 is input to 60, as shown in FIG.

51a is 7 from the input synchronization signal a as shown in FIG.
The delayed signal e is output to 61b.

The two outputs of 61b alternately output 11'' and 0 to 62 or 63 as shown in f9g of FIG. 10 according to e.

The cutoff signal is input to 62 and 63. The cutoff signal is S in Figure 10! When input when f is "1" as in 62
outputs a pulse to 64. Since the output of 62 becomes the reset input of 64, the output of 64 becomes "0". The closing phase signal becomes "0" and is input to 12, and the next closing phase e becomes 0.

When a cutoff signal is input as in 82 when g is 11'', 63 outputs a pulse to 64. The output of 63 is 640
When set manually, the output of r64 becomes "1". The input phase signal becomes "1" and is input to 12, and the next input phase becomes π.

As described above, in the present invention, it is possible to cut off at any point in the single-phase X-ray generator, and the excitation inrush current of the high voltage transformer can be reduced.

In addition, in FIG. 9, the phase difference between the input No. 14 of 61a and the output signal can be selected within a range of about ±20% with respect to i, depending on the hysteresis characteristics of the iron core used in the high-voltage transformer. .

As another example, a method may be considered in which a pulse generated by detecting the point in time when the circuit is actually opened by monitoring the voltage of the switching element 10 is used as the cutoff signal inputted to the circuit 11. With this method, a greater effect of suppressing biased magnetism can be obtained.

According to the present invention, it is possible to cut off at any phase in a single-phase X generator, and it is possible to reduce fluctuations in the output voltage caused by the inrush phenomenon of a high-voltage transformer, so that the photographic density in an X-ray photograph can be appropriately adjusted. This has the effect of being controllable and improving reproducibility.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional single-phase X-ray generator, Figure 2 is a diagram showing the relationship between the irradiation signal and output voltage in the conventional equipment, and Figure 3 is a diagram showing the relationship between the applied voltage of a high voltage transformer and magnetic flux density. , 4th
5 is a block diagram of an embodiment of a single-phase X-ray generator according to the present invention, FIG. 5 is a block diagram of an embodiment of an AC switch, FIG. 6 is a block diagram of another embodiment of an AC switch, and FIG. 8 is a time chart explaining the operation of FIG. 7, FIG. 9 is a configuration diagram of an embodiment of the closing phase determiner, and FIG. 10 is a block diagram of an embodiment of the closing phase controller. 9 is a time chart explaining the operation of FIG. 9; 2... Auto transformer, 5... High voltage transformer, 6... Single phase full wave rectifier, 7... X-ray tube, 10... AC switch, 11... Closing phase determiner , 12... closing phase controller, 13... synchronous signal generator. Meat 1 mouth 20 3rd closing 1 also 40 Shima - 7 eyes opening 8U; 3 74 ” Miq's live 10ro

Claims (1)

[Claims] 1. In a single-phase X-ray generator equipped with a high-voltage generation circuit that boosts and rectifies AC voltage adjusted by a voltage regulating transformer using a high-voltage transformer, an opening/closing device that opens and closes the low-voltage side. A phase detector whose output changes according to the phase of the power supply, a block whose output changes according to the output of the phase detector and the signal for opening the switch or the phase when the switch is opened. First thing to do
An X-ray generator comprising: a controller; and a second controller that controls closing or the phase of closing and opening of the switch in accordance with the output signal of the first controller. 2. The switch according to claim 1 includes at least a rectifier, and a first switch for short-circuiting the output of the rectifier.
An X-ray generator comprising: a switching element; and a rectifier circuit for forcibly commutating the first switching element. 3. An X-ray generator characterized in that the switch according to claim 1 includes at least a rectifier, and a switching element for short-circuiting the output of the rectifier has a self-extinguishing function. 4. The phase detector according to claim 1 is an X-ray generator characterized in that the output changes when the phase of the power supply is - or near it, and when JπA2 or near it.