JPS63224195A - X-ray device with automatic intensity regulation mechanism - Google Patents

Abstract

PURPOSE:To make it possible to force automatic intensity regulation to rapidly follow the change of the thickness of an object to be photographed by connecting a voltage control means to a capacitor in series, thereby the means comprising a resistor and a switch for discharging electric charge on the capacitor of a voltage regulation circuit when dropping of the voltage of a high voltage direct current is controlled. CONSTITUTION:A voltage control means to discharge electric charge on a capacitor 33 provided on the output side of a chopper and to drop the voltage thereof comprises a resistor 63 and a transistor 62 and a diode 64 serving as means to intermittently control the resistor. Because, there is a difference of a voltage changing constant between the times of tube voltage rise and drop, a voltage of a voltage regulating circuit or a charged voltage of the capacitor 33 provided on the output side of a chopper rapidly drops, a voltage regulating circuit or a chopper can not control it when a voltage drops (the condition that a time ratio of thyristers 25a-25d of the voltage regulating circuit or the transistor 29 of the chopper becomes zero and the circuit or the chopper stops). Therefore, it is possible to rapidly regulate a tube voltage to an adequate value.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an X-ray apparatus, and more particularly, to a method for rapidly adjusting the brightness of an X-ray fluoroscopic image to a constant value and an easy-to-see level even when the thickness of a subject changes. The present invention relates to an X-ray apparatus with an automatic brightness adjustment mechanism that can be controlled.

[Prior art and problems to be solved by the invention] When performing X-ray fluoroscopy on a subject using an To keep the output brightness of an X-ray fluorochrome intensifier (image intensifier, hereinafter abbreviated as 1.I), which is a display device, constant, and to control the brightness of a monitor image of an X-ray television camera device to be constant is required. Such control is generally referred to as automatic brightness adjustment, and various methods have been put to practical use. Here are some typical control methods.

Method 1: A voltage adjustment circuit that converts AC voltage to an appropriate DC voltage, a smoothing circuit that reduces pulsations in the output voltage, a DC-AC converter that converts the DC output voltage to AC, and the AC Equipped with a high voltage transformer that boosts the output voltage and a high voltage generation circuit that rectifies the output and applies high voltage to the X-ray tube.

An X-ray fluoroscopic inspection system comprising a converter that converts X-ray information transmitted through a subject into a visible image, a device that captures an output image of the converter, and a display device.

When the output brightness of the converter that converts into the visible image changes and the output brightness of the display device changes due to a change in the thickness of the subject or an increase in the amount of X-ray opaque material used for X-ray contrast imaging, etc. , automatic brightness that detects the output brightness of the converter to convert into a visible image and feeds it back to the voltage adjustment circuit to control it and adjust the DC output voltage to adjust the voltage applied to the X-ray tube. Adjustment method Method 2: In an X-ray fluoroscopy inspection system having a high voltage generation circuit with a DC-DC converter that variably adjusts the DC voltage between the smoothing circuit and the DC-AC converter in Method 1, Automatic brightness adjustment that detects the output brightness of the converter that converts it into a visual image, feeds it back to the DC-DC converter, controls it, adjusts the DC output voltage, and adjusts the voltage applied to the X-ray tube. There is a method.

FIG. 2 shows an embodiment according to the first method. The input voltage from the AC power supply 1 is input to a full-wave rectifier circuit comprising semiconductor control elements (hereinafter referred to as thyristors) 25a to 25d. In the full-wave rectifier circuit, the phase angle of the thyristor is controlled by the drive signals from the drivers 26a and 26b, and the output voltage is adjusted with respect to the input voltage and outputted. This smoothing circuit consisting of the output beam handle 27 and the capacitor 28 reduces voltage pulsations. A circuit including transistors 36a to 36d, diodes 37a to 37d, and drivers 38a to 38d constitutes a DC-AC converter (hereinafter referred to as an inverter).

The inverter includes drivers 38a, 38d and driver 38b from an inverter control circuit (not shown).

A drive signal is alternately input to 38c, and transistors 36a, 36d and transistor 36c.

36b is alternately turned on and off, thereby converting the input DC voltage into rectangular wave AC. This AC voltage is input to the first side of the high-voltage transformer 39 and boosted, and then rectified by a high-voltage rectifier consisting of diodes 40a to 40d.
The X-rays are applied to the X-ray tube 41 and X-rays are emitted. The X-rays that have passed through the subject 8 are converted into visible light in step 1.1.9, and the image of the output phosphor screen is displayed on the monitor 12 captured by the television camera 11 via the optical system 10. On the other hand 1. I.

The output luminance of the output phosphor screen 9 is detected by a detector (not shown) built into the optical system 10, and converted into an electrical signal by a photomultiplier tube 13. The output signal of the photomultiplier tube 13 is amplified by an amplifier 14, and the amplified signal vX is compared by a comparator 16 with the output of a reference signal generator 15, which is set in advance in accordance with the brightness of the monitor 12, and an error signal V is generated. .

occurs. This error signal Vo is supplied to a Vg reference signal generator 5 which determines the operating center of the phase control angle of the thyristor in advance.
4 is added by an adder 55 to output the Va reference signal. The reference signal Vg and the voltage V- detected by the resistors 34 and 35 that detect the output voltage of the rectifier circuit are compared by a comparator 56 to output an error signal VF. 57 is a phase control angle adjustment circuit that adjusts the phase control angle of the thyristor from the error signal; as the error signal VF becomes larger, the phase control angle becomes smaller and the rectifier circuit output voltage vc1 increases.

As explained earlier, when the object thickness increases, 1,
Il1 degree output V! becomes smaller, the error output Vn of the comparator 16 increases, and the Vg reference signal also increases.

When the error output VF of the comparator 56 also increases and the phase control angle of the one-phase control angle adjustment circuit 57 becomes smaller with respect to the drivers 26a and 26b, the rectifier circuit output voltage V c z increases and the tube voltage Vgv increases. As the tube voltage increases, 1. I brightness output V! gradually increases, and the monitor brightness returns to the state before the change in object thickness.

When adjusting the tube voltage in this way, automatic brightness adjustment is possible by controlling the phase angle of the thyristor of the rectifier circuit.

FIG. 3 shows an embodiment according to the second method.

The AC power supply 1 is rectified by a rectifier circuit including thyristors 25a to 25d and thyristor drivers 26a and 26d. The reactor 27 and the capacitor 28 constitute a smoothing circuit to reduce voltage pulsations. Transistor 29. Transistor driver 30. Diode 32. Reactor 31. The circuit made up of the capacitor 33 is a DC/DC conversion circuit (hereinafter referred to as a chopper). transistor 29
By changing the time ratio between the ON period and the OFF period, a DC voltage proportional to the duty ratio can be obtained at the capacitor 33. Resistor 3 connected in parallel with capacitor 33
The series circuit of 4 and 35 constitutes a chopper output voltage detector. A reference voltage Ve proportional to a predetermined chopper output voltage
Comparing the output V- of the chopper output voltage detector with the comparator 43° oscillation circuit (0, S, C) 44. and comparator 43
A pulse width modulation circuit (PW) generates a signal that determines the on and off periods of the transistor 29 from the error signal of the output of the
M) 45 is a chopper control circuit, which operates so that the detected voltage Va is always the same with respect to the set reference voltage Vc. In this way, the chopper always outputs a stable DC voltage in response to input voltage fluctuations and load fluctuations. A circuit including transistors 36a to 36d and diodes 37a to 37d is a DC-AC converter (hereinafter referred to as an inverter).

). The details are the same as those explained in FIG.

The X-rays that have passed through the subject 8 are converted into visible light in step 1.1.9, and an image of the output fluorescent surface is captured by a television camera 11 via an optical system 10 and displayed on a monitor 12. On the other hand, the output brightness of the output fluorescent surface of 1.1.9 is detected by a detection section (not shown) built into the optical system 10, and converted into an electric signal by the photomultiplier tube 13. Photomultiplier tube 1
The output signal of No. 3 is amplified by an amplifier 14, and the amplified signal V is compared by a comparator 16 with the output of a reference signal generator 15, which is set in advance in accordance with the brightness of the monitor 12, to generate an error signal Vo. . This error signal VD is added by an adder 46 to the output of a KV reference signal generator 47, which determines the center point of operation of tube voltage change in advance, to create a reference signal Vc.

In a system configured in this manner, when the thickness of the subject changes as explained in the first method, the chopper output voltage can be adjusted by changing the duty ratio of the transistor 29, thereby adjusting the tube voltage. . In other words, automatic brightness adjustment is possible.

Let us examine the problems of the conventional control methods as described above. In the first method shown in Figure 2, the factors that determine the responsiveness of the widthwise brightness adjustment are the responsiveness of the control system after the brightness detector in 1.1.9, and the responsiveness of the voltage adjustment circuit and smoothing circuit. Can be classified. However, the response of the control system is fast and can be ignored. The selection of the smoothing circuit accelerator 27 and the capacitor 28 is important for increasing the response speed.

Generally, the fluoroscopic load conditions in a diagnostic X-ray apparatus are a maximum tube voltage of 125 KV, a tube current of about 4.0 mA, and therefore a power of about 500 W. On the other hand, during photographing, the output ranges from 30KW to 100KW.

The rate of pulsation in the smoothing circuit also appears in the boosted tube voltage. This results in pulsations in synchronization with the power supply frequency, resulting in a decrease in X-ray dose generation efficiency. Therefore, the smoothing circuit must sufficiently reduce voltage pulsations, resulting in a large LC product. For example, at around 100Kυ, the beam axle is 0.1m.
H~1.0mH, capacitor is constant between 50mF~200mF.

Let us consider the responsiveness of automatic brightness adjustment in the case of such a constant.

When the object thickness increases, the phase control angle of the thyristor becomes smaller and the rectifier circuit output voltage V CL responds to increase. Responsiveness at this time is determined by two factors. The thyristor phase angle control depends on the frequency of the power supply 1, and when the power supply frequency is 507, the control is performed every 10 m5ec, and a dead time element is included. Also, charging is performed in the smoothing circuit using the time constants of the reactor and capacitor. On the other hand, when the object thickness decreases, the phase angle control of the thyristor is similarly controlled every IQmsec, but the discharge time constant of the smoothing circuit becomes a problem. The equivalent resistance R of the X-ray tube during fluoroscopy is, for example, 100 KV 2. At OmA, R = 50MΩ, and assuming the turns ratio of the high voltage transformer is 400, converting to the primary winding side of the high voltage transformer, R' = 50MΩ/400”
=312.5 04. - Become. Inverter is DC-AC
Since the power value is only converted and the power value is not changed, the converted resistance value can be replaced by an equivalent resistance R' for the portion after the inverter as shown in FIG. Assuming that the rectifier circuit output voltage detection resistor is sufficiently large compared to the equivalent resistor R' and can be ignored, the discharge time constant of the capacitor C is CR'. When using the above capacitor capacity, the time constant is 15.6s
ec~62.5 sec, resulting in a very slow response.

Therefore, when increasing the tube voltage in response to a change in object thickness, the response is determined by the phase control of the thyristor and the time constant of the smoothing circuit, and is on the order of several milliseconds to several tens of milliseconds.

On the other hand, when decreasing the tube voltage, the thyristor is turned off, so the smoothing circuit capacitor C and the X-ray tube load condition are considered as equivalent resistances, and the time constant is determined by the resistance value R' substituted on the primary side of the high voltage transformer. The speed is extremely slow, and when considered from a clinical perspective, the monitor image causes halation, making it extremely difficult to see and hindering diagnosis.

Next, let us consider the second method shown in FIG.

The factors that determine the responsiveness in this case can be classified into the responsiveness of the control system after the brightness detector in 1.1.9 and the responsiveness of the chopper, as in the first method. However, although there is a rectifier circuit and a smoothing circuit in FIG. 3 as well as in FIG. 2, it is assumed that they operate to always generate a constant output voltage and are not related to responsiveness. It is assumed that the responsiveness of the control system can be ignored as in the first method. In FIG. 3, it is assumed that the rectifier circuit and smoothing circuit' are a power source E that generates a constant DC output voltage. Also, the circuits after the inverter are replaced with equivalent circuits as discussed in the first method.

FIG. 5 shows the equivalent circuit. Here we will briefly explain the operation of the chopper. The sixth time chart explains the operation.
As shown in the figure. The output of the oscillator (0, S, C) 44 causes P
, W, M signal generating circuit (P, W, M) 45 generates a ramp signal. On the other hand, the signal VE from the control circuit is P, W,
A comparator inside the M signal circuit compares it with the ramp signal and generates the P, W, and M signals.6 As can be seen from the waveforms after time t2, as vI: increases, the P, W, and M signals become signals with large duty ratios. generate. The P, W, and M signals are amplified by a driver to drive the transistor 29. Assuming that the power supply E, which is the input voltage, is constant, the output voltage V c
z increases as the duty ratio increases. On the other hand, when the signal VE is lowered, the operation is opposite to that described above. The operation up to the generation of the error signal VE will be briefly explained using FIG. The X-rays transmitted through the object 8 are 1. I,9 is converted into a visible image. The output brightness of the output phosphor screen is detected by a detection unit built into the optical system 10 and converted into an electrical signal by a photomultiplier tube 13. Photomultiplier tube 13
The output signal of Vl is amplified by the amplifier 14, and the output signal Vl
occurs. Vl is the output of the reference signal generator 15, which is set in advance according to the brightness of the monitor 12, and the comparator 1.
6 and the error signal V.

occurs.

Signal V! corresponding to detected brightness! the negative polarity.

The output of the reference signal generator 15 has a positive polarity.

Now, assuming that both are balanced and in an optimal state,
Both output signals VD are zero. In this state, subject 8
If the permeability increases, such as becoming thinner, 1. ! , 9 increases, and the detector output V! The output level increases, and the error signal VD, which is the polarity inverted output of the comparator 16, increases to negative polarity.

Vo is K that determines the operating center point of tube voltage change in advance.
The signals are added by the V reference signal generator 47 (positive polarity) and the adder 46, and the polarity is inverted. Therefore, the output Vc of the adder 46 decreases with negative polarity. vc is the output detection voltage V
- in a comparator 43, and generates an output VE with inverted polarity. however.

The negative output is clamped to the pulse width modulation circuit 45 so that only positive polarity is output.

When Vc decreases, VE decreases, and the pulse width modulation circuit 4
5, the on period of the transistor 29 is reduced and the output voltage Vex is reduced.

If the detection signal Vl suddenly increases, such as when direct X-rays that do not pass through the object 8 suddenly enter, the comparator 43
The output becomes zero, transistor 29 is turned off, and voltage control is not performed. The voltage drop operation in this case is expressed by the equivalent circuit shown in FIG. 5, as described above.

When the load resistance R' is large and the capacitance of the capacitor C2 is large, the drop in the output voltage V C2 is determined by the discharge time constant C of Cz.
z, determined by R'. Here, the selection of capacitor C2 is determined based on the chopper operating frequency and output voltage ripple. In general, power transistors range from several tens of kW to 10 kW.
For reasons of economy, bipolar transistors are used in systems with a capacity of 0 KW. Since this type of chopper has an on time of several microseconds and an off time of about ten or more microseconds, the maximum operating frequency of the chopper is several kilohertz. As a characteristic of the chopper, the higher the operating frequency, the lower the capacitance of the capacitor Cz, the faster the response, and the lower the pulsation.

However, as mentioned above, since the frequency is low, capacitor C2
The capacitance of 0.1 mF to 0.5 is inevitable.
It has a capacitance of mF. For this reason, the above-mentioned discharge time constant is 1 for example at 100 KV and 2.0 mA when the discharge time constant is 0.31 seconds to
It becomes 1.56 seconds. As explained above, in the chopper, the time constant that changes is different when increasing the output voltage and when decreasing the output voltage. For example, consider a case where the change is made by 20%. It takes a few milliseconds when going up, but it takes 70 milliseconds to 0.35 seconds when going down. For this reason, during fluoroscopy, it is not possible to respond quickly to sudden changes in the subject, but the response is good to changes in body position that correspond to an increase in the subject's tube voltage.
The response to changes corresponding to a drop in tube voltage is slow, and the brightness of the monitor image of the X-ray television camera equipment causes halation.
This makes it extremely difficult to see and prevents diagnosis.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic brightness adjustment mechanism that has high-speed response to changes in object thickness when performing automatic brightness adjustment during fluoroscopy.

[Summary of the invention]

As mentioned above, the present invention focuses on the fact that there is a difference in the voltage change time constant when the tube voltage rises and falls. In order to provide high-speed follow-up response when the time ratio of the chopper becomes zero and the chopper stops, the chopper is equipped with a voltage adjustment circuit or a voltage control means that rapidly lowers the capacitor charging voltage on the output side of the chopper. It is characterized by

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In the figure, the same components as those described so far are indicated by the same reference numerals. Voltage control means for discharging the charge in the capacitor 33 on the chopper output side and lowering the voltage is composed of a resistor 63 and a transistor 62 and a diode 64 as switching means for controlling the resistor 63 on and off. 61
is a driver that drives the transistor 62. , 60
is a control circuit that generates a signal for controlling the transistor 62 from the error signal VE which is the output of the comparator 43. FIG. 7 shows detailed circuits of the pulse width modulation circuit (PWM) 45, the control circuit 6o, and the drive circuit 61.

A circuit consisting of an operational amplifier OP le OP z and a transistor Trx surrounded by a dashed line is a ramp function generating circuit that generates a ramp signal C. Oscillation circuit (0, S,
C) Signal A from 44 is inverted by inverter IC48, and one-shot multivibrator (MM) 49 generates reset signal F that turns on transistor Trs. The output C of the ramp function generating circuit and the error signal VE shown in FIG. 1 are used by a comparator 50 to generate pulse width modulation signals having different pulse widths. This signal is inverted and amplified by a transistor (Trz) 51 and then generated as a PWM output.

Here, when the chopper is operating and a constant power is always supplied to the high voltage transformer 39□, the PWM output output is outputting a signal with a constant pulse width, so the error signal VE
A certain voltage is generated.

Variable resistor Rrt generates a reference voltage Vh corresponding to the lowest error signal in the fluoroscopic load. The operational amplifier OPa is a comparator, and when the error signal 7 days falls below the reference voltage Vh, it generates a positive voltage at its output and turns on the transistor Tra.

The photocoupler PC is for insulating the control circuit system and the circuit system including the transistor 62.

The output phototransistor is turned on. Photocoupler P
C and the transistor Tra constitute a driver 61 of the transistor 62.

Transistor Tr4 is turned off and transistor 62 is turned on. As a result, the resistor 63 and transistor 6 shown in FIG.
A short circuit is formed between the capacitor 2 and the capacitor 33, and a discharge circuit is formed for the capacitor 33.If the resistance value of the resistor 63 is made much smaller than the equivalent resistance R' of the X-ray tube, the voltage of the capacitor 33 can be rapidly dropped.

FIG. 8 is an operation waveform diagram for explaining the above operation. As mentioned above, the straight X-rays that do not enter the subject 8 are 1
．． 1.9, the detection signal V! When the error signal VE increases rapidly, the error signal VE rapidly decreases and becomes below the lowest error signal level, reaching zero volts. In this state, the operational amplifier OPa outputs +Vcc, and the transistor (Trz) 51 is turned on. state and PWM signal E
is not output. Therefore, the transistor 29 is turned off and no power is supplied to the capacitor 33.

The charge in the capacitor 33 is transferred to the X-ray tube 41 via an inverter.
In addition to being supplied to
decreases. When the detection signal Vt again becomes equal to the output of the reference signal generator 15 and VD becomes zero, the output Vc of the adder 46 increases, and the detector outputs V- and Vc stabilize in a different state than before, A constant error signal VE is generated and again applied to the PWM output. When the error signal Vg becomes equal to or higher than the reference voltage 77, the operational amplifier OP4 outputs zero volts again, turns off the transistor Tr3, turns on the transistor Tr4, turns off the short circuit transistor TrB (62), opens the short circuit, and outputs a PWM output. The output rising transistor 29 starts operating.

As described above, the voltage of the capacitor 33 rapidly drops and the tube voltage reaches an appropriate value, so that the halation state of the monitor image of the television camera device can be shortened and an easy-to-see image can be obtained.

FIG. 9 is a diagram for explaining another embodiment.

Figure 9 is a circuit in which the chopper is omitted from Figure 1,
This is a method in which voltage adjustment is performed by controlling the phase angle of a thyristor in a rectifier circuit constituted by thyristors 25a to 25d. Output of reference signal generator 15 and photomultiplier tube 13
The comparator 16 compares the amplified output with the output Vl, and outputs an error signal Vo. This error signal Vo determines in advance the operating center of the phase control angle of the thyristor v
It is added to the output of the i reference signal generator 54 by an adder 55 to output a Va reference signal. Detection voltage v4 by resistors 34 and 35 that detects the reference signal Va and the rectifier circuit output voltage
are compared by a comparator 56 and output an error signal VF.

Discharging the charge in the rectifier circuit output side capacitor 28,
The voltage control means for lowering the voltage includes a resistor 63, a transistor 62 as a switch means for intermittent control, and a flywheel diode 64.

FIG. 10 shows a circuit diagram of the phase control angle adjustment circuit 57, the control circuit 60, and the driver 61. FIG. 11 shows operating waveforms. A low-voltage AC voltage vAc is input from the AC power supply 1 to a zero-cross detector 66 via a transformer 65 to generate a zero-cross signal Vz, which is input to a ramp generation circuit 67 . A voltage of opposite polarity (-V
p) is added by operational amplifier OP1'. Inverted output V
L is compared with the error signal VF by the operational amplifier OP2'.

A phase control angle signal Va is obtained as an output. This signal is input to the thyristor driver, and during the period when V& is output,
An on-gate signal is output to the thyristor, making it conductive.

Reference signal V corresponding to the lowest error signal in the fluoroscopic load
h is set by resistor R11. The error signal VF' is V
When it becomes less than h, the phase control angle signal V& becomes 180", no on-gate signal is generated, and the thyristor becomes non-conductive. Also, the output of the operational amplifier OP4 becomes +VCC level, and as mentioned above, the transistor Trs is turned on. resistance 6
3 and the transistor 2 form a short circuit, and the capacitor 28 is rapidly discharged and the voltage drops. Voltage VC
1, the transistor (Trll) 62 is turned off, and an on-gate signal is generated in the thyristor again. In this embodiment, as in the first embodiment, halation occurs. Even if this occurs, the tube voltage quickly shifts to an appropriate value, making it possible to obtain an image that is easy to view. In addition, although the present invention has been described for tube voltage control during fluoroscopy using automatic brightness adjustment, the circuit of the present invention can also be partially modified in the case of manual setting of normal fluoroscopy tube voltage without using an automatic brightness adjustment mechanism. Then, for example, in FIG. 1, the tube voltage adjustment in the case of manual setting, which is effective for speeding up the tube voltage adjustment, is set by the KV reference signal generator 47, and the error signal Vo from the brightness detection system is set. It is turned off by a switch. Therefore, when the set tube voltage value is changed from a high state to a low state by the KV reference signal generator 47, the charge charged in the capacitor 33 cannot rapidly change to the charging voltage corresponding to the low set tube voltage, so Poor responsiveness.

By adding the voltage adjusting means of the present invention, it becomes possible to adjust the capacitor voltage at high speed as described above. In the case of the other embodiment shown in FIG. 7 as well, the tube voltage adjustment by manual setting is set by the Va reference signal generator 54, and the error signal Vo is turned off by a switch in the same manner as described above. Therefore, as explained in the case of FIG. 1, the voltage can be adjusted at high speed.

〔Effect of the invention〕

According to the present invention, by adding a discharge circuit to the inverter input voltage when lowering the fluoroscopic tube voltage, the time constant for lowering can be made small, and the tube voltage can be rapidly brought to an appropriate value. Therefore, the halation state of the monitor image of the television camera device can be shortened, and an easy-to-see image can be obtained.

In order to reduce the discharge time constant of the capacitor on the input side of the inverter, for example, if only a resistor is used instead of the voltage control means as in this embodiment, the same effect as in this embodiment can be obtained when the fluoroscopic tube voltage decreases.

However, in this case, a small resistance is always inserted in parallel with the load, so a loss occurs in the constant resistance. As explained in the embodiment, this resistance needs to be much smaller than the equivalent resistance R' of the X-ray tube.
The current flowing through the resistor is large and the loss is large. In the method according to the present invention, the resistor is inserted only for a short time when the tube voltage is to be lowered, so the loss can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram for explaining the present invention in detail, and FIG.
The figure is for explaining the problems of the conventional method. Fig. 3 is a circuit diagram for explaining the problems of other conventional methods, Figs. 4 and 5 are equivalent circuit diagrams for explaining the problems of the conventional method, and Fig. 6 is a circuit diagram for explaining the problems of other conventional methods. An operation waveform diagram for explaining the operation of the conventional method, FIG. 7 is a detailed circuit diagram for explaining one embodiment of the present invention, and FIG. 8 is an operation waveform diagram for explaining one embodiment of the present invention. 9 is a circuit diagram for explaining another embodiment of the present invention, FIG. 10 is a detailed circuit diagram for explaining another embodiment of the present invention, and FIG. 11 is a detailed circuit diagram for explaining another embodiment of the present invention. 10 is an operation waveform diagram of FIG. 10. FIG. DESCRIPTION OF SYMBOLS 1... AC power supply, 9... Image intensifier (1,1,), 10... Optical system, 11... Television camera, 12... Monitor, 13... Photomultiplier tube ,
14... Amplifier, 15... Reference signal generator, 16.
... Comparator, 25 a, 25 b, 25 c
, 25 d - semiconductor control element (thyristor), 26
a, 26b...driver, 27...reactor, 2
8... Capacitor, 29... Transistor, 30...
...Driver, 31...Reactor. 32... Diode, 33... Capacitor, 36a
. 36b, 36c, 36d - transistor, 38a. 38 b, 38 c, 38 d-driver, 3
9-...High voltage transformer, 40a, 40b, 4
0 c, 40 d - diode, 41... X-ray tube, 43... comparator, 44... oscillation circuit (0, S,
C), 45... Pulse width modulation circuit (P, W, M), 4
6-...adder, 47-KV reference signal generator, 54...
・v1 base reference amount generator, 55... Adder, 56...
Comparator, 57... Phase control angle adjustment circuit, 60... Control circuit, 61... Driver, 62... Transistor, 63... Resistor, 64... Diode. No. 40 #5 Figure 3 to EiJ Atsushi! 1 figure

Claims (1)

[Claims] 1. Voltage adjustment including a smoothing capacitor consisting of an AC-DC converter that converts AC input to DC and can adjust the output voltage, or an AC-DC converter and a DC-DC converter that adjusts its output voltage. a circuit, a DC-AC converter that converts this direct current to alternating current, a high-voltage transformer that boosts its output, a rectifier that converts the output to high-voltage direct current voltage, and an X-ray tube that applies high-voltage direct current voltage; A converter that converts X-ray information transmitted through the object into a visible image, a comparator that compares the detection signal of the means for converting the output luminance of the converter into an electrical signal and a preset reference value, and the In an X-ray apparatus with an automatic brightness adjustment mechanism configured with a circuit that outputs the output of a comparator to the voltage adjustment circuit as a voltage adjustment control signal, the charge in the capacitor of the voltage adjustment circuit is discharged during high-voltage DC voltage step-down control. 1. An X-ray apparatus with an automatic brightness adjustment mechanism, characterized in that a voltage control means consisting of a resistor and a switch is connected in series to the capacitor.