JPH04294099A - X-ray device - Google Patents

Abstract

PURPOSE:To provide an X-ray device which exhibits in early timing an excellent stability of X-ray tube voltage even though the width of the load to be handled is enlarged. CONSTITUTION:When the drive of an inverter circuit 4 is started, a rising control circuit 10 feeds a pulse width control circuit 9 with a reference voltage signal S13 which is generated by a reference voltage generator circuit and which gives the reference for a voltage rising from zero. The pulse width control circuit 9 makes feedback control on the basis of result from comparison of the sensed tube voltage signal S11 with the reference voltage signal S13, and an X-ray tube voltage rising from zero is impressed on an X-ray tube 7 in conformity to the reference voltage signal S13. When the X-ray tube voltage reaches the set value, the abovementioned rising control circuit 10 gives a set tube voltage signal S12 to the pulse width control circuit 9, which performs feedback control on the basis of result from comparison of the sensed tube voltage signal S11 with the fed set tube voltage signal S12, and an X-ray tube voltage equal to the set tube voltage is impressed on the X-ray tube 7.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray apparatus that performs feedback control of an X-ray tube voltage based on a comparison between the X-ray tube voltage and a set tube voltage.

0002

[Prior Art] In recent years, in X-ray equipment, the power supply supplied to the X-ray tube has become a switching power supply, and the X-ray tube voltage applied to the X-ray tube is generally controlled by PWM control of an inverter circuit. There is. Further, a method is adopted in which the input pulse width to the inverter circuit is controlled by feedback control based on a comparison between the X-ray tube voltage and the set tube voltage so that the X-ray tube voltage becomes equal to the set tube voltage.

[0003] It is desirable to perform X-ray imaging immediately after driving the inverter circuit from the viewpoint of imaging efficiency, but if a pulse with a width corresponding to the set tube voltage is suddenly input to the inverter circuit,
Ripples are added to the high-voltage waveform applied to the X-ray tube, resulting in a longer time to start imaging and a decrease in imaging efficiency. Therefore, as shown in FIG. 6, a soft start is performed using sequential control in which pulses W1 to W3 with increased constant pulse widths ΔW are sequentially input to the inverter circuit. By this soft start, when the X-ray tube voltage reaches the set tube voltage, the control is switched to feedback control. The conventional feedback control is only constant value control in which the X-ray tube voltage is controlled to be equal to a constant set tube voltage. Additionally, the maximum pulse width input to the inverter circuit is determined in accordance with the maximum load to be handled, to prevent unnecessary power supply.

0004

[Problems to be Solved by the Invention] According to the conventional device as described above, when the load is maximum as shown in FIG.
The X-ray tube voltage becomes constant at time t1 (approximately 0.1 seconds) after the inverter circuit is driven. On the other hand, when the load is small, the X-ray tube voltage becomes constant in time t2, which is shorter than time t1, but if the ripple R rides on the voltage waveform and it takes time t3, which is longer than time t1 when the load is maximum, to stabilize. There is also.

[0005] Particularly in the case of an X-ray apparatus such as an X-ray CT apparatus, which performs short imaging with a total imaging time of around 1 second, it is necessary that the imaging start time be as short as possible. Furthermore, in recent years, the range of loads handled has tended to widen, and the above problem has become a problem that cannot be ignored. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an X-ray apparatus that has excellent early stability of the X-ray tube voltage even when the range of loads handled is widened. [Structure of the invention]

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an X-ray apparatus that applies an X-ray tube voltage by driving an inverter circuit to an X-ray tube, and which provides an input set tube voltage. A pulse that performs feedback control so that the X-ray tube voltage becomes equal to the set tube voltage by controlling the input pulse width to the inverter circuit based on a comparison between the signal and the detected tube voltage signal of the X-ray tube voltage. The X-ray apparatus equipped with a width control circuit includes a reference voltage output circuit that outputs a reference voltage signal whose voltage increases from zero when the inverter circuit starts driving, and the X-ray tube voltage increases after the inverter circuit starts driving. The apparatus is characterized in that it includes a rise control circuit that inputs the reference voltage signal to the pulse width control circuit instead of the set tube voltage signal until the set tube voltage is reached.

[0007]

[Operation] The operation of the above-mentioned device configured as described above will be explained.

After the inverter circuit starts to be driven until the X-ray tube voltage reaches the set tube voltage, the operation is as follows. First, when the inverter circuit starts to be driven, the reference voltage generation circuit generates a reference voltage signal whose voltage increases from zero. The rise control circuit does not input a set tube voltage signal to the pulse width control circuit, but inputs a reference voltage signal. The pulse width control circuit controls the input pulse width to the inverter circuit based on a comparison between the input reference voltage signal and the detection tube voltage signal. A pulse width control circuit performs feedback control based on the reference voltage signal and the detection tube voltage signal, and an X-ray tube voltage is applied to the X-ray tube whose voltage increases from zero in response to the reference voltage signal.

After the X-ray tube voltage reaches the set tube voltage,
It works as follows. The rise control circuit does not input a reference voltage signal to the pulse width control circuit, but inputs a set tube voltage signal. The pulse width control circuit controls the input pulse width to the inverter circuit based on a comparison between the input set tube voltage signal and the detected tube voltage signal. A pulse width control circuit performs feedback control based on the set tube voltage signal and the detected tube voltage signal, and an X-ray tube voltage equal to the set tube voltage is applied to the X-ray tube.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of an X-ray apparatus 1 according to an embodiment of the present invention. This device 1 includes an AC power source 2,
A rectifier smoothing circuit 3 that converts AC voltage to DC voltage, an inverter circuit 4 that converts the DC voltage output of the rectifier smoothing circuit 3 to AC voltage, and a high voltage transformer 5 that boosts and outputs the AC voltage output of the inverter circuit 4. , a high-voltage rectifier circuit 6 that converts high-voltage AC voltage into high-voltage DC voltage and applies it to the X-ray tube 7, kV signal S1, mA signal S2, and X-ray exposure signal S3.
The inverter control circuit 8 controls the inverter circuit 4 based on the kV
It is roughly composed of an operator console (not shown) that generates signals such as the signal S1, the mA signal S2, and the X-ray exposure signal S3.

The high voltage transformer 5 is equipped with a tube voltage detection circuit that detects the X-ray tube voltage actually applied to the X-ray tube 7, and outputs the detected detection tube voltage signal S11 to the pulse width control circuit 9. That's what I do. The inverter control circuit 8 includes a pulse width control circuit 9 that controls the pulse width of the pulse signal S15 input to the inverter circuit 4, and a rise control circuit 10 that controls the pulse width control circuit 9 at the time of rise.

FIG. 2 shows an example of the configuration of the inverter control circuit 8. The pulse width control circuit 9 of the inverter control circuit 8 includes a selector 11 and a comparison circuit 12. The selector 11 receives the input kV signal S1, m
Setting tube voltage signal S of the corresponding voltage based on the A signal S2
12. For example, if 120 kV is set, a set tube voltage signal S12 of a DC voltage of 12 V proportional to this set tube voltage (120 kV) is output. The comparison circuit 12 includes an amplifier 13 and a high voltage transformer 5.
The voltage difference between the detected tube voltage signal S11 detected by the tube voltage detection circuit and the set tube voltage signal S12 or reference voltage signal S13 (described later) output from the selector 11 is generated as an error signal S14.

The rise control circuit 10 includes a reference voltage generation circuit 1 comprising a switch 16, an amplifier 17, and a capacitor 18.
4, a switching circuit 15 comprising a switch 19 and an amplifier 20
It is equipped with. The reference voltage generation circuit 14 generates a reference voltage signal S13 whose voltage increases from zero in response to the input X-ray exposure signal S3. Also, switching circuit 1
5 is a reference voltage signal S generated by the reference voltage generation circuit 14.
When the voltage No. 13 reaches the voltage of the set tube voltage signal S12, the control is switched to constant value control. Next, the operation of the embodiment device 1 configured as described above will be explained.

When the operator operates a console (not shown) to set a low load tube voltage (for example, 80 kV) and tube current, the console sends a kV signal S1 to the selector 11.
, mA signal S2 is input. The selector 11 selects a voltage (for example, 8V) corresponding to the set tube voltage (80kV).
) is outputted to the reference voltage generation circuit 14 and the switching circuit 15. Since the switch 16 of the reference voltage generation circuit 14 is located at the contact point 16b, and the switch 19 of the switching circuit 15 is located at the contact point 19b, the set tube voltage signal S12 does not flow in each circuit 14, 15.

After the inverter circuit 4 starts to be driven until the X-ray tube voltage reaches the set tube voltage, the operation is as follows. When the operator operates the X-ray exposure switch on the console (not shown), the inverter circuit 4 is driven, and the console
The radiation exposure signal S3 is input to the reference voltage generation circuit 14. The switch 16 of the reference voltage generation circuit 14 operates at the contact 16a. At this stage, the switch 19 of the switching circuit 15 is still operating at the contact 19b, so the set tube voltage signal S12 from the selector 11 is not directly input to the comparison circuit 12, but flows through the reference voltage generation circuit 14. . The reference voltage generation circuit 14 inputs to the comparison circuit 12 a reference voltage signal S13 whose voltage increases from zero based on the input set tube voltage signal S12. The comparison circuit 12 converts the voltage difference between the input reference voltage signal S13 and the detected tube voltage signal S11 detected by the tube voltage detection circuit of the high voltage transformer 5 into an error signal S1.
Occurs as 4. The pulse width control circuit 9 inputs a pulse signal S15 whose pulse width is controlled based on the error signal S14 to the inverter circuit 4. The inverter circuit 4 converts the DC voltage converted by the rectifying and smoothing circuit 3 into an AC voltage based on the input pulse signal S15, and inputs the AC voltage to the high voltage transformer 5. The high voltage transformer 5 boosts the AC voltage output of the inverter circuit 4 and outputs it to the high voltage rectifier circuit 6.
High pressure is applied to the X-ray tube 7. Until the X-ray tube voltage reaches the set tube voltage, the pulse width control circuit 9 performs feedback control based on the reference voltage signal S13 and the detection tube voltage signal S11, so the X-ray tube 7 receives the reference voltage signal. Corresponding to S13, an X-ray tube voltage increasing from zero is applied.

After the X-ray tube voltage reaches the set tube voltage,
It works as follows. The amplifier 20 of the switching circuit 15 compares the voltages of the set tube voltage signal S12 from the selector 11 and the reference voltage signal S13 from the switch 16 of the reference voltage generation circuit 14, and when the voltages match, the amplifier 20 switches the switch 19 of the switching circuit 15. is operated at contact 19a. The tube voltage signal S12 from the selector 11 is input directly to the comparison circuit 12 without passing through the reference voltage generation circuit 14, and the comparison circuit 12 calculates the difference between the input detected tube voltage signal S11 and the set tube voltage signal S12. A voltage is generated as an error signal S14. The pulse width control circuit 9 inputs a pulse signal S15 whose pulse width is controlled based on the error signal S14 to the inverter circuit 4. Each part 4, 5, 6 acts in the same manner as described above, and high pressure is applied to the X-ray tube 7. After the X-ray tube voltage reaches the set tube voltage, the pulse width control circuit 9 switches to fixed value control, and the pulse width control circuit 9 performs feedback control based on the set tube voltage signal S12 and the detected tube voltage signal S11. Therefore, an X-ray tube voltage equal to the set tube voltage is applied to the X-ray tube 7.

According to the above embodiment device 1, as shown in FIG. 4, when the load is maximum, the inverter circuit is driven for a time t1 (approximately (0.1 seconds), the X-ray tube voltage becomes constant. In addition, when the load is small, X
Although the line tube voltage is constant, there is a ripple R as shown in Figure 5.
Because it does not ride on the voltage waveform, the shooting start time can be made shorter than before, and the shooting efficiency can be improved.

FIG. 3 shows an inverter control circuit 38 that is another example of the inverter control circuit 8 shown in FIG. The inverter control circuit 38 shown in FIG. 3 includes a selector 11 similarly to the inverter control circuit 8 shown in FIG.
1 and a tube voltage detection circuit (not shown) of the high voltage transformer 5 are connected to the input side, and a detection amplifier 33a, and a differential circuit 3.
1 and a reference rate-of-change signal output circuit 32 connected to the input side, and a signal selection circuit 34 connected to the output side of each amplifier 33a, 33b.

The detection amplifier 33a outputs the voltage difference between the set tube voltage signal S12 inputted from the selector 11 and the detected tube voltage signal S11 inputted from the tube voltage detection circuit of the high voltage transformer 5 as an error signal S33a. It is something. The differentiating circuit 31 outputs a differential signal S31 obtained by differentiating the detection tube voltage signal S11, and the reference rate of change signal output circuit 32 outputs a reference rate of change signal S32 in which the voltage increases from zero. Also, the reference amplifier 33b
outputs the voltage difference between the differential signal S31 inputted from the differentiating circuit 31 and the reference rate-of-change signal S32 inputted from the reference rate-of-change signal output circuit 32 as an error signal S33b. The signal selection circuit 34 outputs the error signal S33b from the reference amplifier 33b until the voltages of the two input error signals S33a and S33b match, and after that, outputs the error signal S33a from the detection amplifier 33a. It is designed to output .

The X-ray apparatus using the inverter control circuit 38 configured as described above provides the same functions and effects as the X-ray apparatus 1 using the inverter control circuit 8 shown in FIG. Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways without changing the gist thereof.

[0022]

According to the present invention described in detail above, feedback control is performed not only after the X-ray tube voltage reaches the set tube voltage after driving the inverter circuit, but also before reaching the set tube voltage. Since ripples are less likely to be added to the X-ray tube voltage waveform depending on the magnitude of the voltage, it is possible to provide an X-ray apparatus with excellent early stability of the X-ray tube voltage even if the range of loads handled is widened.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an X-ray apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a main part of an inverter control circuit of the device shown in FIG. 1;

FIG. 3 is a main part circuit diagram showing another example of the inverter control circuit shown in FIG. 1;

FIG. 4 is a waveform diagram of the X-ray tube voltage applied to the X-ray tube of the apparatus shown in FIG. 1;

FIG. 5 is a waveform diagram of an X-ray tube voltage applied to an X-ray tube of a conventional X-ray apparatus.

FIG. 6 is a diagram showing pulses input to an inverter circuit of a conventional X-ray apparatus.

[Explanation of symbols]

1. X-ray device 4 Inverter circuit 7. X-ray tube 8 Inverter control circuit 9 Pulse width control circuit 10 Rise control circuit 14 Reference voltage output circuit S12 Setting tube voltage signal S13 Reference voltage signal

Claims (1)

[Claims] [Claim 1] Drive an inverter circuit to the X-ray tube to
An X-ray apparatus that applies a ray tube voltage, the X-ray apparatus controlling an input pulse width to the inverter circuit based on a comparison between an input set tube voltage signal and a detected tube voltage signal of the X-ray tube voltage. The X-ray tube includes a pulse width control circuit that performs feedback control so that the X-ray tube voltage becomes equal to the set tube voltage.
The x-ray apparatus includes a reference voltage output circuit that outputs a reference voltage signal whose voltage increases from zero when the inverter circuit starts driving, and the X-ray tube voltage reaches the set tube voltage after the inverter circuit starts driving. An X-ray apparatus further comprising a rise control circuit that inputs the reference voltage signal to the pulse width control circuit instead of the set tube voltage signal.