JP2674451B2 - X-ray high voltage equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an 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 X-ray high voltage apparatus 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 an AC current. The alternating current is boosted by a transformer, rectified and smoothed again to obtain high voltage direct current,
This is supplied to the X-ray tube.

That is, an X-ray high voltage device using a conventional current resonance type inverter is constructed as shown in FIG.
In FIG. 3, the AC output from the AC power supply 1 is rectified by the rectifier 2, accumulated in the smoothing capacitor 3, smoothed, and converted into a DC output. Then, this DC output is switched by the inverter 4 and converted into an AC output, and is sent to the primary side of the high voltage transformer 8 via the resonance capacitor 6 and the resonance inductance 9. A high-voltage AC output appears on the secondary side of the high-voltage transformer 8, which is rectified by the high-voltage rectifier 10 and converted into high-voltage DC, and X
It is applied to the wire tube 11. Here, the resonance inductance 9 includes the leakage inductance of the high voltage transformer 8.

In such a resonance type inverter X-ray high voltage apparatus, the resonance frequency is determined by the resonance capacitor 6 added to the circuit and the inductance 9 such as the leakage inductance of the high voltage transformer. The output is controlled by controlling the switching frequency of the inverter 4 according to the load. Generally, the resonance frequency is designed to exceed the audible frequency, and the switching frequency of the inverter 4 can be changed in a frequency range lower than this resonance frequency. That is, the switching frequency of the inverter 4 is increased as the load during X-ray film photography is increased, and is decreased as the load during X-ray fluoroscopy is reduced, and the relationship between the switching frequency and the load is as shown in FIG. Become involved.

[0005]

However, in the conventional resonance type inverter type X-ray high voltage apparatus as described above, the switching frequency of the inverter 4 exceeds the audible frequency when the load is large such as when photographing an X-ray film. Although the device is quiet to the ears, there is a problem in that the switching frequency of the inverter 4 is in the audible frequency range when the load is low, such as during fluoroscopy, and the device is very noisy to the human ear.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an X-ray high voltage apparatus which has been improved so as to have a low noise both during photographing and during fluoroscopy.

[0007]

In order to achieve the above object, according to the X-ray high voltage apparatus of the present invention, the switching frequency of the switching means for switching the DC output becomes a frequency exceeding the audible frequency range at the time of photographing, and is transparent. It sometimes changes to the audible frequency range depending on the load, and by switching the capacitor or the inductance that determines the resonance frequency, the resonance frequency can be switched so that the resonance frequency becomes high during fluoroscopy. It is characterized by switching in a frequency range higher than the frequency.

[0008]

The resonance frequency can be switched by switching the capacitor or the inductance, but can be switched in a frequency range higher than the switching frequency of the switching means for switching the DC output. On the other hand, the switching frequency of the switching means for switching the DC output is changed according to the magnitude of the load, and the frequency exceeds the audible frequency range during photographing, and drops to the audible frequency range during fluoroscopy. Then, during fluoroscopy (where the switching frequency has dropped to the audible frequency range), the resonance frequency is increased by switching the capacitor or the inductance. Therefore, at the time of shooting, the switching frequency exceeds the audible frequency range.
Since the resonance frequency is higher than the switching frequency, the resonance frequency at this time is also higher than the audible frequency range), and does not cause noise to the human ear. On the other hand, when seen through, the switching frequency becomes low and enters the audible frequency range. At this time, the resonance frequency is increased by switching the capacitor or the inductance. When the resonance frequency becomes higher, the magnetic flux density of the iron core of the high voltage transformer is inversely proportional to the frequency,
The magnetic flux density of the iron core is reduced and the iron loss is reduced. Since this iron loss causes noise, this reduces noise when the load is small and the switching frequency of the inverter is in the audible frequency range. as a result,
Noise can be reduced during both photographing and see-through.

[0009]

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, the AC output from the AC power supply 1 is rectified by the rectifier 2,
It is smoothed by being accumulated in the smoothing capacitor 3 and converted into a DC output. Then, this DC output is switched by the inverter 4 and converted into an AC output.
This AC output is sent to the primary side of the high voltage transformer 8 via the resonance capacitor 6 or 7 selected by the changeover switch 5 and the resonance inductance 9. A high-voltage AC output appears on the secondary side of the high-voltage transformer 8, which is rectified by the high-voltage rectifier 10 and converted into high-voltage DC, and the X-ray tube 1
1 is applied.

The capacitances of the resonance capacitors 6 and 7 are CR and Cf, respectively, and CR> Cf. Since the resonance capacitors 6 and 7 are switched by the changeover switch 5, the resonance frequency becomes low when the resonance capacitor 6 is switched, and the resonance current waveform becomes as shown by the solid line in FIG. When it is turned on, the resonance frequency becomes high, and the resonance current waveform becomes as shown by the dotted line in FIG.

The switching frequency of the inverter 4 is controlled in accordance with the high voltage applied to the X-ray tube 11 within a range lower than the resonance frequency (the control system is not shown).
That is, since the load becomes large when photographing on an X-ray film, the switching frequency of the inverter 4 is increased, and conversely, when the image is seen through, the load is small so that the switching frequency of the inverter 4 is lowered.

Generally, in the case of a current resonance type inverter, under a condition of a constant input voltage, the output increases as the switching frequency of the inverter 4 approaches the resonance frequency fo (see FIG. 4), and the electrostatic capacitance of the resonance capacitor increases. The larger the capacity, the larger the output. Therefore, when an output of several tens of kW is required, such as when photographing on an X-ray film, it is necessary to use a resonance capacitor having a relatively large electrostatic capacity and to increase the switching frequency of the inverter 4 to near the resonance frequency. There is.

Therefore, when there is a large load such as when photographing an X-ray film, the changeover switch 5 is switched to select the resonance capacitor 6 having a large electrostatic capacitance. The value CR of the inductance 9 and the resonance capacitor 6 is determined so that the resonance frequency at this time has a value exceeding the audible frequency. At this time, the inverter 4
The switching frequency of is raised to near its resonant frequency and exceeds the audible frequency, resulting in a quieter human ear.

On the other hand, when the load is light, such as when seeing through, the changeover switch 5 is changed over to the resonance capacitor 7 having a small electrostatic capacitance. At this time, the switching frequency of the inverter 4 is low and in the audible frequency range, but the resonance frequency is higher than when the resonance capacitor 6 is selected because the capacitance of the resonance capacitor 7 is small. . Therefore, the waveform of the current flowing through the high voltage transformer 8 is shown in FIG.
As indicated by the dotted line, the frequency becomes higher, and the magnetic flux density of the high-voltage transformer 8 is inversely proportional to the frequency. Therefore, the magnetic flux density of the iron core decreases, and the iron loss that causes noise also decreases. As a result, it is possible to reduce the noise even when the switching frequency of the inverter 4 is in the audible frequency range when the load is light such as when seeing through.

In the above embodiment, the changeover switch 5
Therefore, one of the two resonance capacitors 6 and 7 having large and small electrostatic capacitances is selected. However, it suffices if the resonance frequency can be changed. It is also possible to adopt a configuration in which whether or not (the combined electrostatic capacity becomes small when inserted in series) is switched by a switch, or a configuration in which the inductance is switched instead of the configuration in which the capacitor is switched.

[0016]

As described above, according to the resonance type inverter type X-ray high voltage apparatus of the present invention, the switching frequency is made higher than the audible frequency range when the film is heavily loaded, and the human ear hears it. It reduces the noise to be felt and switches the resonance frequency to a higher value when the load is low, such as during fluoroscopy, where the switching frequency drops to the audible frequency range, so the iron loss of the transformer, which is the main cause of noise, is reduced. It is possible to reduce the noise and reduce the noise. Therefore, it is possible to reduce the noise during photographing and during fluoroscopy.

[Brief description of the drawings]

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

FIG. 2 is a graph showing a resonance current waveform in the example.

FIG. 3 is a block diagram of a conventional example.

FIG. 4 is a graph showing the relationship between the switching frequency of the inverter and the load.

[Explanation of symbols]

 1 AC power supply 2 Rectifier 3 Smoothing capacitor 4 Inverter 5 Changeover switch 6, 7 Resonance capacitor 8 High voltage transformer 9 Resonance inductance 10 High voltage rectifier 11 X-ray tube

Claims (1)

(57) [Claims] 1. A first rectifying means for converting an AC output from an AC power supply into a DC output, a storage means for accumulating and smoothing the rectified output, a frequency exceeding an audible frequency range during photographing, and an audible frequency during fluoroscopy. A switching means for switching the direct current output obtained from the storage means at a frequency that changes according to the load such that it falls to the range, and a resonance means including a resonance inductance and a resonance capacitor to which the switching output is input; , Means for switching the resonance frequency in a frequency range higher than the above-mentioned switching frequency so that the resonance frequency becomes high when seen through by switching the resonance inductance or the resonance capacitor, and the voltage of the AC output outputted from the resonance means is boosted. Means to convert the boosted AC output to DC output and An X-ray high voltage device, comprising: