JPS5937560B2 - X-ray device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray apparatus, and particularly to improvements in its switching control means.

FIG. 1 shows an example of the configuration of an X-ray apparatus using a three-phase alternating current as a power source, which has been widely used in the past.

In the figure, 1 is a 3-phase AC power supply, 2 is a Y-connected 3-phase half-turn transformer that adjusts the voltage of each phase of the 3-phase AC power supply 1, and 3
has a primary winding 3a that is Y-connected on the primary side and the neutral points of each phase winding are separated and derived without being commonly connected, and a secondary Y-winding that is Y-connected on the secondary side. A three-phase high-voltage lance is constructed with a wire 3b and a secondary delta winding 3c connected in delta, and the output of the three-phase half-turn I-lance 2 is given to the primary winding 3a, and 4 is a three-phase high-voltage lance. A first 3-phase full-wave rectifier circuit which full-wave rectifies the output obtained from the secondary Y winding 3b of the transformer 30 to obtain a positive voltage output, 5 is the secondary Δ winding 3 of the 3-phase high voltage l/lance 3
The second three-phase full-wave rectifier circuits 6 and 7 which obtain a negative voltage output by full-wave rectifying the output obtained from first and second capacitors to which the outputs of the wave rectifier circuits 4 and 5 are applied, and 8 an X-ray to which the positive and negative voltages obtained from the first and second three-phase full wave rectifier circuits 4 and 5 are applied. tube, 9 is 3
A third three-phase full-wave rectifier circuit in which the separated end derived from the primary winding 3a of the phase high-voltage transformer 3 is connected to the three-phase AC input side, and 10 is the DC output of the third three-phase full-wave rectifier circuit 9. The high voltage that is connected to the ends of the X-ray tube 8 is connected with the illustrated polarity (by turning on/off the voltage applied to the primary side of the three-phase high-voltage transformer 3) and turns on/off the X-ray irradiation. a first thyristor, 11 and 12, for X-ray switching;
13 is a second thyristor and a diode connected in series with each other with the polarities shown and provided in parallel with the first thyristor 10 to turn off the first thyristor 10; 13 is provided in parallel with the second thyristor 11; A resonant circuit 14 for turning off the first thyristor 10, consisting of a series circuit of a capacitor and a coil, is provided in parallel with the resonant circuit 13, and is turned off when the first and second thyristors io and i1 are turned off, that is, X-ray exposure is turned off. When the third three-phase full-wave rectifier circuit 9
This charging circuit is charged with the DC output of the first thyristor 10 and serves as a supplementary power source for the resonant circuit for turning off the first thyristor 10.

In this configuration, the first thyristor 10 is used for switching on, and the twentieth thyristor 11 is used for switching on the first thyristor 10.
It is used for the purpose of turning off the thyristor 10, that is, for switching on the thyristor 10.

In this case, the first thyristor 10 is gate-controlled and turned on, and a voltage is rapidly applied to the three-phase high-voltage transformer 3, so that when the switch is turned on, as shown in the tube voltage waveform of the X-ray tube 8 in FIG. Overshoot occurs.

Therefore, the output side of the first and second full-wave rectifier circuits 4 and 5 has a capacitance of about 0.02 to 0.1 μF, for example.
Condenser 6. γ was connected to absorb the overshoot.

The tube voltage waveform of the X-ray tube 8 at this time is shown in FIG. 3a.

However, the configuration shown in FIG. 1 has the following problems.

That is, as can be seen from FIG. 3a, the rise and fall of the high voltage waveform applied to the X-ray tube 8 are delayed, so that the actual conduction period of the first thyristor 10 shown in FIG.
The actual high pressure generation period, that is, the period in which the high pressure applied to the X-ray tube 8 as shown in C in the same figure maintains its peak value, or d in the same figure.
There is a large difference between the total period during which high pressure is applied to the X-ray tube 8 shown in FIG.

Moreover, the rise time and fall time of this high voltage waveform vary greatly depending on the load (tube current, etc.), and even when the conduction period of the first thyristor 10 is the same, a high voltage is applied to the X-ray tube 8. The period, that is, the X-ray exposure time increases (changes) depending on the tube current, etc.

The present invention was made based on these circumstances, and
An object of the present invention is to provide an X-ray apparatus that enables accurate control of the high-pressure generation period applied to a ray tube, that is, the X-ray exposure time, and that can effectively prevent overshoot at the rise of a high-pressure waveform.

That is, the present invention is characterized in that in an X-ray apparatus in which X-ray switching is performed at the neutral point of the Y-connection on the primary side of the high-voltage trough, the first
and a second switching element, these switching elements of the power cylinder 2 are used for main switching, and a series circuit of the first switching element and a resistor is connected in parallel to the second switching element, and the first switching element and the resistor are connected in parallel. First, by turning on the first switching element, a voltage is applied to the primary side of the high voltage transformer through the resistor, and then after a preset extremely short time delay (corresponding to the time when overshoot occurs). The second switching element is turned on.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 4 shows the configuration of an embodiment of the present invention, and in this figure, the same parts as in FIG.

That is, in this case, the first and second capacitors 6.7 in FIG. 1 are removed, and the third thyristor 15 as the first electrical signal switching element is connected in series with the variable resistor 16 whose resistance value can be selectively adjusted. The circuit is connected in parallel to a first thyristor 10 as a second electric signal switching element when viewed from the power source 1 side.

In such a configuration, when irradiating X-rays, the third thyristor 1 is turned on before the first thyristor 10 is turned on.
5, first turn on the primary winding 113a of the high pressure lance 3.
A voltage is applied to the third thyristor 15 and the variable resistor 16 connected in series with the thyristor 15, and the first thyristor 10 is turned on after a delay of, for example, 2 to 5 msec.

Then, when the exposure is stopped, if the second thyristor 11 is turned on, the first thyristor 10 and the third thyristor 1 are turned on.
5 turn-offs are performed simultaneously.

Here, the time from turning on the third thyristor 15 to turning on the first thyristor 10 is 2 to 5 ms.
ec is appropriately adjusted and selected in accordance with the period during which overshoot occurs in FIG.

Although the overshoot size and amplitude) and length of time vary slightly depending on the circuit configuration of the high-voltage transformer 3 and high-voltage generator, etc., the X-ray input phase is always kept constant (usually zero-phase input). The device is in a stable state with the same configuration and under the same load conditions.

Therefore, if the resistance value of the variable resistor 16 is appropriately selected depending on the load condition, for example, the tube current, the tube voltage value during the overshoot occurrence period (that is, the period when only the third thyristor 15 is conducting) can be It can be arbitrarily adjusted as shown in FIGS. 5a, b, and c.

The variable resistance 1
Adjust the resistance value of 6 and shorten the conduction period of the first thyristor 10 by the conduction period of the third thyristor 15 (if you do so, the rise and fall characteristics will be good as shown in Figure 5C and there will be no overshoot. A stable high voltage (kVp value) without any noise can be supplied to the X-ray tube 8 for a scheduled time.

Note that it is practically sufficient to change the resistance value of the variable resistor 16 according to the tube current value only, but strictly speaking, the overshoot value also varies depending on the tube voltage. If the third thyristor 15 is also switched over, more accurate control can be achieved than with a higher voltage value during the conduction period of the third thyristor 15.

That is, when the resistance value of the variable resistor 16 is switched only by the tube current, depending on the value of the tube voltage, the tube voltage value when only the third thyristor 15 is on is determined as shown in FIG. Normal voltage value, i.e. first thyristor 1
A case may also occur where the voltage value is lower than the voltage value when only the third thyristor 15 is on, as shown in a in the same figure, for any tube voltage value. (It is preferable to set the voltage value in advance so that it does not occur.) However, even in such a case, there will be no significant improvement compared to the configuration shown in Figure 1. This can be easily understood by comparing Figure 3a and Figure 5.

Of course, if the resistance value of the variable resistor 16 is changed according to both the tube current and tube voltage, an ideal high voltage waveform can be obtained as shown in FIG. 5C for any tube current or tube voltage. becomes possible.

Furthermore, in an X-ray apparatus that uses a constant tube current value, etc., the variable resistor 16 may be a fixed resistor.

As described above, according to the present invention, it is possible to accurately control the high voltage generation period applied to the X-ray tube, that is, the X-ray exposure time, and to effectively prevent overshoot at the rise of the high voltage waveform. An X-ray device can be provided.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without changing the gist thereof.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of the configuration of a conventional X-ray device, Fig. 2 is a high voltage waveform diagram to explain the occurrence of overshoot in a conventional X-ray device, Fig. 3 is a t b I C
2d is a diagram for explaining the high voltage waveform according to the configuration shown in FIG. 1, FIG. 4 is a circuit diagram of an embodiment of the present invention, and FIGS. It is a high voltage waveform diagram for explanation. 1...3-phase AC power supply, 2...3-phase half-turn transformer, total...high voltage transformer 1.3a...
...Primary winding, 3b...Secondary Y winding, 3 c-
...Secondary Δ winding, 4,5°9...3-phase full-wave rectifier circuit, 8...X-ray tube, 10°11.1
5... Thyristor, 12... Diode, 13... Resonant circuit, 14... Charging circuit, 16... Variable resistor.

Claims (1)

[Claims] 1. The neutral point common connection end of each Y-connected phase winding has a separate primary winding, and a high voltage l-
A three-phase full-wave rectifier circuit in which a separated end of the primary winding of the high-voltage transformer is connected to an AC input end, and a DC output end of the three-phase full-wave rectifier circuit are connected in series with each other. A series circuit consisting of a first electrical signal switching element that is first applied in response to an X-ray exposure command and a resistor for overshoot absorption, and after the first electrical signal switching element that is provided in parallel with this series circuit is made conductive. An X-ray apparatus comprising: a second electric signal switching element to be input; a rectifier circuit that rectifies the secondary high voltage output of the high voltage transformer; and an X-ray tube to which the output of the rectifier circuit is applied. 2. The X-ray apparatus according to claim 1, wherein the overshoot absorbing resistor inserted in series with the first electric signal switching element has a variable resistance value.