JP3202058B2 - Inverter type X-ray high voltage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter type X-ray high-voltage device used in a circulatory organ diagnostic X-ray imaging apparatus, and more particularly to discharge control of the voltage of a resonance capacitor at the end of X-ray irradiation.

[0002]

2. Description of the Related Art Continuous radiography and cine radiography are performed by a circulatory organ diagnostic X-ray radiography apparatus.
Since line pulses are continuously output and dynamics are photographed, reproducibility is required for each pulse. If there is a variation in each pulse, the film density will fluctuate, and in the worst case, it may hinder diagnosis. Therefore, the output voltage on the high voltage side is detected by the inverter type X-ray high voltage device,
The reproducibility is improved by performing feedback control so that the detected value matches the set value. However, even in this inverter type X-ray high voltage device, since reproducibility of short X-ray pulses of several ms is severe, an inverter type X-ray high voltage device using a resonance capacitor is used.

A conventional apparatus is disclosed in Japanese Patent Laid-Open Publication No.
As described in No. 9696, a DC power supply voltage is converted into a high-frequency AC by an inverter circuit 102, this AC is boosted by a high-voltage transformer 112 having a primary winding provided with a resonance capacitor 111, and rectified by a rectifier circuit 113. The voltage is applied to the X-ray tube device 115. The reproducibility of the X-ray pulse depends on the voltage remaining in the resonance capacitor 111. That is, FIG.
As shown in (a), if the inverter circuit is cut off after X-ray irradiation and a voltage is stored in the resonance capacitor, the next X
In line irradiation, the inverter circuit operates while holding the voltage,
As shown in FIG. 10B, the voltage becomes unstable at the time of rising.
Therefore, since the residual voltage of the resonance capacitor 111 must be discharged, in the conventional device, the transistors 104, 104
Only one switch 106 is opened and closed depending on the polarity of the residual voltage of the resonance capacitor 111 to discharge.

[0004]

In the inverter type high-voltage device provided with the above-mentioned resonance capacitor, a circuit for discriminating the polarity and a circuit for storing the judgment result are controlled in order to discharge the voltage of the resonance capacitor. , The circuit configuration was complicated. Also, in short-time shooting such as cine shooting, even a slight shift in time has a large effect on the image, so if the circuit configuration becomes complicated, the timing of one circuit will be delayed, and it will be completely discharged by the next shooting. In some cases, it is not possible to obtain a good image.

It is an object of the present invention to improve the reproducibility of an X-ray pulse by discharging the voltage of a resonance capacitor at the end of X-ray irradiation and to simplify a circuit for discharging.

[0006]

The object of the present invention is to provide a DC power supply, an inverter circuit for converting the DC power supply voltage to a high-frequency AC, an inverter drive circuit for operating respective switching elements constituting the inverter circuit, and A high-voltage transformer for boosting the output voltage of the inverter circuit, a resonance capacitor connected in series to the primary winding of the high-voltage transformer, an X-ray tube device for rectifying the output voltage of the high-voltage transformer and applying this voltage; And a feedback circuit for dividing a voltage applied to the X-ray tube device by a voltage divider and feeding back to the inverter circuit. In the inverter type X-ray high voltage device, a certain phase difference is provided to each switching element of the inverter circuit. The inverter drive circuit so that the inverter circuit operates with the phase difference for a predetermined time. This is achieved by providing a control circuit for controlling and operating the inverter circuit by the control circuit after X-ray irradiation to discharge the voltage stored in the resonance capacitor. The control circuit includes a phase control circuit that determines a phase difference between the switching elements of the inverter circuit after the end of the X-ray irradiation, a phase difference signal for obtaining a target value from the feedback circuit, and a signal from the phase control circuit. A switching circuit for switching a phase difference signal and an inverter drive control circuit for operating the inverter drive circuit for a predetermined time after X-ray irradiation is completed.

[0007]

After the X-ray irradiation, the phase difference between the two switching elements of the inverter circuit used when flowing in the primary winding of the high voltage transformer in the forward direction during the X-ray irradiation and the inverter used when flowing in the reverse direction. By inverting and operating the phase difference between the two switching elements of the circuit, the voltage of the resonance capacitor can be discharged. Therefore, the circuit configuration can be simplified and the reproducibility of the X-ray pulse can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 is a block diagram showing the present invention, FIG. 2 is a block diagram showing a specific configuration of a control circuit, FIG. 3 is a time chart of the inverter circuit at the time of X-ray irradiation, and FIG. 5 is a time chart of the control circuit, FIG. 6 is a block diagram showing another embodiment, FIG. 7 is a flowchart showing the operation of the CPU of FIG. 6, and FIG. 8 is a voltage and tube of the resonance capacitor according to the present invention. It is a voltage waveform. 1 is a DC power supply, 2 is an inverter circuit for converting a voltage output from the DC power supply 1 to AC, and switching elements 6 to 6 in which transistors and diodes are connected in anti-parallel.
9 combinations.

Reference numeral 3 denotes a high-voltage transformer for boosting and rectifying the AC output from the inverter circuit 2, and reference numeral 4 denotes an inverter circuit 2.
A resonance capacitor connected in series between the high-voltage transformer 3 and the X-ray tube device 5 for applying a voltage rectified by the high-voltage transformer 3, a switching element 6 of the inverter circuit 2
An inverter drive circuit for operating the inverter drive circuit 10 to operate the inverter circuit 2 and discharge the resonance capacitor 4;
Reference numeral 12 denotes a timer circuit for controlling the X-ray irradiation time.
1 is output.

Reference numeral 13 denotes a feedback circuit for the X-ray tube device 5.
Is fed back and output to the control circuit 11 and the timer circuit 12. Reference numeral 14 denotes a high-voltage divider that divides a high voltage applied to the X-ray tube device 5 and inputs the divided voltage to the feedback circuit 13.

Next, the operation of the present invention will be described. When irradiating X-rays, the inverter circuit 2 is operated by the inverter drive circuit 10 to output an alternating current to the high-voltage transformer 3 and apply it to the X-ray tube device 5. At this time, the high voltage divider 1
The high voltage to the X-ray tube device 5 is divided by 4 and input to the feedback circuit 13. Then, the inverter drive circuit 10 passes through the control circuit 11 and the timer circuit 12 in order to obtain the high voltage set by the feedback circuit 13.
To work. The adjustment of the high voltage is performed by the switching elements 6 and 9 of the inverter circuit 2 used when the DC power supply voltage is applied to the primary winding of the high-voltage transformer 3 in the positive or negative direction.
Alternatively, the adjustment is performed by changing the phase difference between the switching elements 7 and 8. At this time, each of the switching elements 6 to
The time chart of No. 9 is shown in FIG. 3, and is usually used with a certain phase difference during X-ray irradiation.

When the irradiation of X-rays is stopped, the switching elements 6 and 9 and the switching elements 7 and 8 are controlled by an inverter drive circuit 10 as shown in FIG.
Is inverted or made close to it. As a result, no voltage is applied to the X-ray tube device 5 because a closed circuit is formed by the switching elements 6 and 8 on the + side of the DC power supply 1. At the end of the X-ray irradiation, the residual voltage of the resonance capacitor 4 is discharged, so that the phase difference between the switching elements 6 and 9 and the phase difference between 7 and 8 are inverted, that is, the switching elements 6, 8 and 7, 9 Are operated alternately for a predetermined time (for example, several hundred μm).
s) is activated.

At the end of X-ray irradiation, switching elements 7 and 9
Is operating, the high-voltage transformer 3 of the resonance capacitor 4
If the positive side is a positive charge, the residual voltage is the resonance capacitor 4 →
High voltage transformer 3 → Transistor of switching element 9 →
Discharge occurs through the path from the diode of the switching element 7 to the resonance capacitor 4. If the high-voltage transformer 3 has a negative charge, the discharge is performed through the path of the resonance capacitor 4 → the transistor of the switching element 7 → the diode of the switching element 9 → the high voltage transformer 3 → the resonance capacitor 4.

In the operation of the switching elements 6 and 8 at the next timing, if the high-voltage transformer 3 has a positive charge, the residual voltage of the resonance capacitor 4 is changed to the resonance capacitor 4 →
Discharge occurs in the path of the high voltage transformer 3 → the diode of the switching element 8 → the transistor of the switching element 6 → the resonance capacitor 4. If the high-voltage transformer 3 has a negative charge, it is discharged through the path of the resonance capacitor 4 → the diode of the switching element 6 → the transistor of the switching element 8 → the high voltage transformer 3 → the resonance capacitor 4.

Next, a specific circuit operation of the control circuit 11 will be described. Feedback circuit 13 during X-ray irradiation
The control circuit 11 controls the inverter circuit 2 by operating the inverter drive circuit 10 through the switching circuit in the control circuit 11 to determine the phase difference to be the target value of the high voltage to be applied. When the timer circuit 12 is turned off and the X-ray irradiation is completed, the phase difference between the switching elements 6 to 9 of the inverter circuit 2 is changed by the phase control circuit so that the resonance capacitor 4 discharges using the inverter circuit 2. The drive circuit 10 is operated. At this time, since the inverter circuit 2 must be operated in order to discharge the residual voltage of the resonance capacitor 4 after the X-ray irradiation, the inverter drive control circuit operates the inverter circuit 2 for a certain time after the X-ray irradiation.

This operation will be described with reference to FIG. A timer signal for X-ray irradiation from the timer circuit 12 is input to the switching circuit 11b and the inverter drive control circuit 11a. The switching circuit 11b switches to the phase difference signal of the feedback circuit 13 while the timer signal is on, and switches to the phase difference control circuit 11c while the timer signal is off and inputs the signal to the inverter drive circuit 10. Then, the inverter drive control circuit 11a operates even after the timer circuit 12 is turned off for a time necessary for operating the inverter several times in order to discharge the residual voltage of the resonance capacitor 4. That is, when the timer signal is on, control is performed by the phase difference signal from the feedback circuit 13 so as to reach the target value, and when the timer signal is off, the inverter drive control circuit 11a
Accordingly, the inverter circuit 2 is operated with a phase difference at which the voltage of the resonance capacitor 4 can be discharged for a certain time after the timer signal is turned off.

Another embodiment using a CPU is shown in FIG.
Shown in In this case, the switching circuit 11b, the phase difference control circuit 11c, and the feedback circuit 13 of the control circuit 11 are connected to a CPU.
And the inverter drive control circuit 11a as an inverter operation control unit 16. Inverter phase control unit 15 is connected to CPU 15a and RO
M15b, RAM 15c, input port 15d, and output port 15e. ROM 15b stores a program required for control. The phase difference signal is output to the output port 15e.

The inverter operation control section 16 includes a delay circuit 1
6a and a gate circuit 16b. A timer signal and a signal obtained by delaying the timer signal by a delay circuit 16a are combined by a gate circuit 16b. The delay circuit 16a generates a signal for operating the inverter circuit 2 only for a time necessary for operating the inverter circuit 2 several times because the resonance capacitor 4 is discharged. Then, the combined signal and the inverter drive signal are combined and output by the gate circuit 10b.

That is, at the time of X-ray irradiation, a phase difference signal corresponding to the target value is input from the inverter phase control unit 15 to the inverter drive circuit 10 and fed back to the inverter circuit 2, and after the X-ray irradiation, the output voltage of the inverter circuit 2 is output. Is input to the inverter drive circuit 10 for a predetermined time after X-ray irradiation.
To work.

Next, FIG. 7 shows a control program for the X-ray irradiation processing of the inverter phase control unit 15. When this program starts, first, a phase difference signal for causing a discharging operation is output to the output port 15e (step A), and the process waits until the timer signal is turned on (step B). When the timer signal is turned on, the measured X-ray tube voltage for calculating the control phase difference of the target value is input from the input port 15d (step C). Then, the operation of the timer signal is determined again (step D). If the timer signal is on, the control phase difference is calculated (step E) and output to the output port 15e (step F). The signal is output to the output port 15e (Step G). At this time, the inverter drive control signal is determined (step H). If it is on, the operation is repeated from step C. If it is off, the X-ray irradiation process is determined (step I). When continuing in this step I, the process restarts from step A, and when ending, X
Terminate the line irradiation.

The switching elements 6 to 6 of the inverter circuit 2
X-ray irradiation can be controlled by the change in the phase difference of No. 9. Also, X
In order to discharge the voltage remaining in the resonance capacitor 4 after the end of the X-ray irradiation, a discharge can be performed by providing a phase difference between the switching elements 6 to 9 and operating the inverter for a certain time after the end of the X-ray irradiation. The circuit configuration can be simplified, and the reproducibility of X-ray pulses can be improved.

[0022]

According to the present invention, a control circuit for controlling the inverter drive circuit is provided, and the control circuit changes the phase difference between the switching elements of the inverter circuit and operates the inverter circuit for a fixed time after the end of X-ray irradiation. The voltage of the resonance capacitor can be discharged through the inverter circuit. That is, it is possible to discharge only by the phase difference and the operation time of the inverter circuit. Thus, the circuit configuration can be simplified, and the reproducibility of the X-ray pulse can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the present invention.

FIG. 2 is a block diagram showing a specific configuration of a control circuit.

FIG. 3 is a time chart of an inverter circuit at the time of X-ray irradiation.

FIG. 4 is a time chart of the inverter circuit after the end of X-ray irradiation.

FIG. 5 is a time chart in a control circuit.

FIG. 6 is a block diagram showing another embodiment.

FIG. 7 is a flowchart showing the operation of the CPU in FIG. 6;

FIG. 8 shows waveforms of a voltage of a resonance capacitor and a tube voltage according to the present invention.

FIG. 9 shows waveforms of a conventional resonance capacitor voltage and a tube voltage.

FIG. 10 shows waveforms of a conventional resonance capacitor voltage and a tube voltage.

FIG. 11 is a configuration diagram of a conventional inverter type X-ray high voltage device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter circuit 3 High voltage transformer 4 Resonant capacitor 5 X-ray tube device 6 Switching element 7 Switching element 8 Switching element 9 Switching element 10 Inverter drive circuit 11 Control circuit 12 Timer circuit 13 Feedback circuit 14 High voltage divider 15 Inverter phase control Unit 16 Inverter operation control unit 117 Current polarity discrimination circuit 119 Operator 120B Drive circuit 121 Base drive circuit 129 Voltage detector 130 Voltage polarity discrimination circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05G 1/32 H05G 1/20

Claims (2)

(57) [Claims] 1. A DC power supply, an inverter circuit for converting the DC power supply voltage into a high-frequency AC, and the inverter circuit.
Operating each switching element that constitutes
An inverter drive circuit and an output power of the inverter circuit.
A high-voltage transformer for boosting the pressure, the resonance capacitor which is series connected to the primary winding of the high-voltage transformer, rectifies the output voltage of the high voltage transformer and an X-ray tube device for applying the voltage, the X-ray tube A feedback circuit for dividing a voltage applied to the device by a voltage divider and feeding back the voltage to the inverter circuit ;
In the inverter type X-ray high voltage device having the above i
Providing a certain phase difference to each switching element of the inverter circuit
The inverter circuit operates at the phase difference for a predetermined time.
Control the inverter drive circuit to operate
A control circuit is provided.
Activate the inverter circuit to connect to the resonance capacitor.
An inverter type X-ray high voltage device characterized by discharging a stored voltage. 2. The control circuit according to claim 1, further comprising:
Position that determines the phase difference between the switching elements of the inverter circuit
Set the target value from the phase control circuit and the feedback circuit.
And a phase difference signal from the phase control circuit.
Switching circuit for switching the signal, and a predetermined time after the end of X-ray irradiation
Inverter for operating the inverter drive circuit
Claims characterized by comprising a live control circuit
Item 2. An inverter type X-ray high voltage device according to item 1.