JPH0427680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an X-ray high voltage device, and more particularly to a high voltage generator using an inverter.

[Prior art]

FIG. 1 shows the configuration of a high voltage generator using an inverter. 1 is an AC/DC converter with a function to adjust the magnitude of DC voltage, 2 is an inverter that operates at a constant duty rate and converts the output of 1 to AC with a constant frequency of several kHz, and 3 is 2 4 is a rectifier that converts the AC voltage boosted by 3 into a DC voltage; 5 is a smoothing capacitor;
6 is an X-ray tube, and 7 is a filament heating circuit for controlling the tube current. In the conventional system, the inverter 2 always operates at a constant frequency and constant energization rate, and the tube voltage is controlled by changing the DC voltage that is the output of the AC/DC converter 1. For this reason,
Output voltage waveform a of inverter 2 during normal shooting
And the output voltage waveform b of the inverter 2 during fluoroscopy is,
As shown in Figure 2, they are almost equal. These frequencies are all several kHz, and the sound generated by this vibration is unpleasant to humans. During imaging, the exposure time is short, so there is no problem, but during fluoroscopy, the exposure continues for several minutes, which may cause damage to the patient or X-ray.
There is a risk of causing pain to line technicians.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray high voltage apparatus that suppresses the generation of unpleasant sounds by changing the operating frequency of an inverter during fluoroscopy to that during imaging.

[Summary of the invention]

In the present invention, in order to suppress the sound generated during fluoroscopy, the operating frequency of the inverter during fluoroscopy is set to approximately 1/10 that of imaging, which is several hundred Hz. but,
When the output voltage waveform of the inverter 2 becomes as shown in Fig. 3b, the voltage-time product (hereinafter referred to as Vt
product) becomes large, and the high-voltage transformer becomes saturated. Therefore, in order to make the Vt product equal to a during imaging, as shown in FIG. 3c, even if the frequency is lowered during fluoroscopy, the energization time of the inverter is made equal to a during imaging. At this time, the output power of the inverter is
Approximately 1/10 of what it was when the photo was taken. However, since the tube current during fluoroscopy is normally several mA, there is no shortage of power supply.

[Embodiments of the invention]

FIG. 4 shows an embodiment of the present invention. 8 is an inverter controller that controls the operating frequency of the inverter 2. FIG. 5 shows an embodiment of the inverter 2 and the inverter controller 8. In FIG. 21 and 24 and 22 and 23 are thyristors that repeat opening and closing almost simultaneously; 25 to 28 are diodes that bypass the respective commutation energy after the thyristors 21 to 24 are extinguished; and 29 to 32 are thyristors 21 to 24.
commutation thyristor for extinguishing the arc, respectively, 33
represents thyristors 21 and 22, and 34 represents thyristor 2.
3 and 24 are commutating capacitors that store energy for extinguishing arcs, 35 and 36 are commutating reactors, 3
7 starts oscillation in response to the ON signal, and outputs two types of pulses with 180° phase difference, several kHz when the fluoroscopy selection signal is not input, and several hundred Hz when the fluoroscopy selection signal is input. Pulse generator, 3
8 and 39 are monostable multivibrators that generate constant pulses according to the output signal of the pulse generator 37, and 40 and 41 generate pulses by detecting the falling edge of the monostable multivibrators 38 and 39. It is a differentiator.

Next, the operation will be explained.

During imaging, when the ON signal is input to the pulse generator 37 in the inverter controller 8, the pulse generator 37 starts oscillating at a frequency (several kHz), and the sixth
The signals a and d in the figure are output. The signal a becomes the gate signal for the thyristors 21 and 24 and fires the thyristors 21 and 24. The signal a is also input to the monostable multivibrator 38, and as shown in FIG. Output _po pulse. In the differentiator 40,
As shown in Figure 6c, monostable multivibrator 3
Detecting the falling edge of the output pulse No. 8, the pulse is output, and the commutating thyristors 29 and 31 are fired. The thyristors 21 and 24 are extinguished by the energy previously stored in the commutating capacitors 33 and 34.
Similarly, the signal d causes the thyristors 22 and 23 to
is fired, and commutated thyristor 30 is activated by the signal of
and 31 are fired to extinguish thyristors 22 and 23. In this way, the thyristors 21 and 24 and 22 and 23 repeat opening and closing alternately. When the ON signal disappears, the pulse generator 37 stops oscillating, and the inverter stops operating.

Next, in the case of fluoroscopy, a fluoroscopy selection signal is input, and the oscillation frequency of the pulse generator 37 becomes approximately 1/10'. Therefore, the thyristors 21 to 24 are
It is fired at frequency ′. Moreover, thyristor 21
The gate signals of the commutating thyristors 29 to 32 that extinguish the arcs of thyristors 24 to 24 are t _po
thyristor 21 as shown in Figure 7.
The firing time of ~24 is always constant regardless of photography or fluoroscopy.
t _po , and the Vt product of the high voltage transformer does not change depending on the operating frequency of the inverter. Therefore, saturation of the iron core of the high voltage transformer can be prevented.

Another embodiment uses transistors as the switching elements of the inverter, but in this case an inverter controller similar to that shown in FIG.
If the transistor is driven with 9 output pulses, a result equivalent to that described above can be obtained.

〔Effect of the invention〕

According to the present invention, when X-ray exposure is continuous for several minutes during fluoroscopy, the operating frequency of the inverter is lower than several kHz, which is uncomfortable for humans, and becomes several hundred Hz.
Does not cause discomfort to patients or X-ray technicians. Furthermore, since the Vt product of the high-voltage transformer is approximately the same during imaging and during fluoroscopy, magnetic saturation of the iron core of the high-voltage transformer can be suppressed.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a high voltage generator using an inverter, Fig. 2 is an inverter output voltage waveform diagram during imaging and fluoroscopy in the configuration of Fig. 1, and Fig. 3 is a diagram of the inverter output voltage waveform during imaging and fluoroscopy according to the present invention. 4 is a configuration diagram of an embodiment of the high voltage generator according to the present invention, FIG. 5 is a circuit diagram of an embodiment of the inverter and inverter control, and FIG. 6 is a photographic diagram according to the present invention. Time chart showing the movement of time, No. 7
The figure is a time chart showing the operation during fluoroscopy according to the present invention. 1... AC/DC converter, 2... Inverter, 3
...High voltage transformer, 4... Rectifier, 6... X-ray tube,
7...Filament heating circuit.

Claims (1)

[Claims] 1. An inverter that receives DC voltage and converts it into AC voltage, a high voltage transformer that steps up the output voltage of this inverter, and a rectifier that converts the output voltage of this high voltage transformer into DC voltage. 1. An X-ray high voltage apparatus comprising an inverter controller that controls the operating frequency of the inverter to be a lower frequency during fluoroscopy than during imaging. 2. The X-ray high-voltage apparatus according to claim 1, characterized in that it is an inverter controller that controls the operating frequency to be about 1/10 of that during radiography during fluoroscopy. 3 In claim 1 or 2,
The X-ray high voltage is characterized by comprising an inverter controller that controls the on-time of the switching element to be substantially constant even when the operating frequency changes, or the voltage-time product of the high-voltage transformer to be substantially constant. Device.