JPH06310295A - Inverter type x-ray high voltage apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain an inverter type X-ray high voltage device that does not generate noise at low load. [Constitution] When the load is low, the inverter 4 is switched by the fixed frequency generation circuit 10 at a frequency exceeding the audible frequency.
At that time, the charging voltage of the input side capacitor 11 of the inverter 4 is adjusted by the phase control of the thyristors 12 and 12 'to control the tube voltage.

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, and more particularly to an X-ray high voltage device using a current resonance type inverter.

[0002]

2. Description of the Related Art An inverter type X-ray high-voltage device using a current resonance type inverter rectifies and smoothes an AC power source, then switches at high speed with the inverter and resonates with a resonance inductance and a resonance capacitor to generate a high frequency AC. This alternating current is boosted by a transformer, rectified and smoothed again to obtain high-voltage direct current, which is supplied to the X-ray tube as a tube voltage.

That is, a conventional inverter type high voltage device is constructed as shown in FIG. In FIG. 2, the AC output from the commercial AC power supply 1 is rectified by the rectifier 2, accumulated in the smoothing capacitor 3, smoothed, and converted into a DC output. This DC output is switched by the inverter 4 and converted into an AC output, which is sent to the high voltage generator 7 via the resonance capacitor 5 and the resonance inductance 6. The high voltage generator is provided with a high voltage transformer and a high voltage rectifier, which is converted into high voltage DC and applied to the X-ray tube 8. Here, the resonance inductance 6 includes the leakage inductance of the high voltage transformer that constitutes the high voltage generator 7.

In such a resonant inverter X-ray high voltage apparatus, the resonant frequency is determined by the resonant capacitor 5 added to the circuit and the inductance 6 such as the leakage inductance of the high voltage transformer. The output is the tube voltage, that is, the switching (driving) of the inverter 4 according to the load.
It is controlled by controlling the frequency.

Therefore, the control of the high voltage of the direct current applied to the X-ray tube 8, that is, the control of the tube voltage is performed by dividing the tube voltage by the voltage dividing resistor provided in the high voltage generator 7, and measuring it. Is fed back to the frequency control circuit 9, and this circuit 9 changes the switching frequency of the inverter 4 so that the actually measured tube voltage becomes the set tube voltage.

Generally, the resonance frequency is designed to be higher than the audible frequency, and the switching frequency of the inverter 4 is changed according to the set tube voltage in a frequency range lower than the resonance frequency. That is, the switching frequency of the inverter 4 becomes higher as the load during X-ray film photographing becomes larger, and becomes lower as the load becomes smaller during X-ray fluoroscopy.

[0007]

However, in the conventional resonance type inverter type X-ray high voltage apparatus, the switching frequency of the inverter 4 is higher than the audible frequency when the load is large such as when photographing an X-ray film. However, there is a problem in that the switching frequency of the inverter 4 becomes a low frequency in the audible frequency range when the load is small, such as during fluoroscopy, and it becomes a very noisy device that is audible to the human ear. In particular, when the device is placed near the operator and the subject (patient) such as a surgical X-ray device and used, it cannot be ignored in terms of mental health. Further, since the fluoroscopy is continuously performed for a long time, the noise generated by the device becomes more problematic.

In view of the above, the present invention provides an inverter type X-ray high-voltage device in which the switching frequency of the inverter does not fall into the audible frequency range even when the load is low during fluoroscopy and noise is not generated. To aim.

[0009]

In order to achieve the above-mentioned object, the present invention is an inverter type X-ray high voltage device in which the switching frequency of the inverter is changed according to the load, and the inverter is higher than the audible frequency. A means for switching at a constant frequency and a means for changing the direct current input to the inverter when switching the inverter at a constant frequency were provided.

[0010]

The means for switching at a constant frequency switches the inverter at a high frequency exceeding the audible frequency when the load is small such as during X-ray fluoroscopy. As a result, the device does not generate noise.

The means for changing the DC input changes the input of the inverter during switching at a constant frequency of the inverter according to the load.

Therefore, the tube voltage can be controlled by changing the input of the inverter.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 10 is a fixed frequency generating circuit for switching the inverter 4 at a certain frequency exceeding the audible frequency, and 11 is a smoothing capacitor which serves as a DC power source of the inverter 4 when the load is small such as when seeing through. It is connected to the AC power supply 1 via the thyristors 12 and 12 '.

Reference numeral 13 denotes a phase control circuit, which is a high voltage generator 7
The tube voltage feedback signal and the set tube voltage signal detected and measured inside are supplied, and the phase control of the thyristors 12 and 12 'is performed based on the comparison result of both, and the measured tube voltage becomes equal to the set tube voltage. Control the charging voltage of the smoothing capacitor 11. Reference numeral 14 is a changeover switch for switching between photographing and fluoroscopy, which is switched to the R value during photographing and to the F side during fluoroscopy.

Next, the operation of the above apparatus will be described. First, at the time of a heavy load such as when photographing an X-ray film, the changeover switch 14 is changed over to the R side opposite to that shown in the drawing. This state is the same as that of FIG. 2, and the AC output from the AC power supply 1 is rectified and smoothed by the rectifier 2 and the smoothing capacitor 3 to be converted into the DC output, and this DC output is converted into the inverter 4
Is switched by and converted into an AC output. This AC output is sent to the high voltage generator 7 via the resonance capacitor 5 and the resonance inductance 6, converted into high voltage DC, and applied to the X-ray tube 8.

At this time, the frequency control circuit 9 compares the tube voltage feedback signal from the high voltage generator 7 with the set tube voltage signal, and controls the switching frequency of the inverter 4 so that the actually measured tube voltage becomes the set tube voltage. That is, the switching frequency is controlled according to the high voltage applied to the X-ray tube 11. The values CL of the resonance capacitor 5 and the resonance inductance 6 are set so that the resonance frequency at this time exceeds the audible frequency, and the frequency control circuit 9 controls the value CL according to the high voltage applied to the X-ray tube 11. The switching frequency of the inverter 4 is raised to near its resonance frequency and thus exceeds the audible frequency. As a result, it is quiet to the human ear.

On the other hand, when the load is light such as when seeing through, the changeover switch 14 is changed over to the F side shown in the figure. In this state, the AC output from the AC power supply 1 is the thyristor 12, 1
The inverter 4 is phase-controlled by 2'and converted into a DC output by the capacitor 11, and this DC output is switched at the switching frequency determined by the fixed frequency generation circuit 10.
Is converted to AC output.

This AC output is sent to the high voltage generator 7 through the resonance capacitor 5 and the resonance inductance 6,
The high-voltage DC is converted and applied to the X-ray tube 8. Since the fixed frequency generation circuit 10 switches the inverter 4 at a certain frequency exceeding the audible frequency, it becomes quiet to the human ear as when the changeover switch 14 is switched to the R side.

Further, the tube voltage feedback signal from the high voltage generator 7 and the set tube voltage signal are supplied to the phase control circuit 13, and the circuit 13 compares the two signals and measures the measured tube voltage. By controlling the phase of the thyristors 12 and 12 'so that the voltage becomes the set tube voltage, the capacitor 1
It controls the charging voltage of 1, that is, the input to the inverter 4.

As described above, when the changeover switch is switched to the R side and under a large load such as when photographing, the capacitor charging voltage is constant, that is, the input voltage of the inverter is constant and the tube voltage is controlled by changing the switching frequency of the inverter. When the load is switched to the F side such as X-ray fluoroscopy, the switching frequency of the inverter is constant and the tube charging voltage is controlled by changing the capacitor charging voltage. In either control, the switching frequency of the inverter is Beyond the audible frequency, it is quiet to the human ear and produces no noise.

In the above embodiment, the thyristor is used to control the charging voltage of the capacitor during light load such as X-ray fluoroscopy for switching the inverter at a fixed frequency, and the phase control thereof is also used. It is also possible to use an auto transformer. Further, in the embodiment, the frequency control circuit and the phase control circuit are provided with the automatic control function, the tube voltage feedback signal is supplied, and the tube voltage can be automatically set to the set tube voltage, but manual setting is also possible. Is.

[0022]

According to the present invention, the inverter can be switched at a switching frequency exceeding the audible frequency even under a small load such as fluoroscopy, so that an inverter type X-ray high-voltage device without noise can be obtained. .

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional example.

[Explanation of symbols]

1 ... AC power supply 2 ... Rectifier 3 ... Smoothing capacitor 4 ... Inverter 5 ... Resonance capacitor 6 ... Resonance inductance 7 ... High voltage generator 8 ... X-ray tube 9 ...
Frequency control circuit 10 ... Fixed frequency generation circuit 11 ... Capacitor 1
2, 12 '... Thyristor 13 ... Phase control circuit 14 ... Changeover switch

Claims (1)

[Claims] 1. An AC output from an AC power source is converted into a DC output, the converted DC output is switched by an inverter to be converted into a high frequency AC output, and the converted AC output is boosted to a DC output. In a high-voltage device for converting and applying to the X-ray tube as a tube voltage and changing the switching frequency of the inverter according to the tube voltage, means for switching the inverter at a constant frequency higher than an audible frequency, An inverter type X-ray high voltage apparatus, characterized in that it is provided with means for changing a DC output input thereto at a constant frequency of the inverter according to a tube voltage.