JPH0227800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to tube voltage control for an inverter type X-ray apparatus.

There are several types of inverter-type X-ray equipment, but considering the performance of current semiconductor devices, the first one is
Inverter type X consisting of the circuit shown in the figure
Suitable for diagnostic X-ray equipment that requires high output.

In this inverter type X-ray apparatus, as shown in FIG. 1, alternating current is supplied from a commercial power source 1 to a first rectifier circuit 2. The first rectifier circuit 2 is a rectifier diode 3
and thyristor 4, and an opening/closing part (not shown)
In order to prevent overcurrent when the capacitor is closed, the phase of the thyristor 4 is controlled and the smoothing capacitor 5 is gradually charged. The current charged and smoothed by the smoothing capacitor 5 is interrupted by the chopper 6 and supplied to the filter 7 during X-ray irradiation. The chopper 6 is composed of a switching transistor 28, and the duty ratio during intermittent operation is set by the pulse width modulation circuit 26 according to the tube voltage preset by the tube voltage setting section 27, and the chopper 6 is driven by the chopper drive circuit 25. . For example, as shown in the figure, the filter 7 includes diodes 8 and 9 and chiyoke transformers 10 and 1.
1, resistors 12 and 13, and a capacitor 14, it smoothes continuous rectangular wave pulses interrupted by a chopper 6, and supplies the smoothed pulses to an inverter 15.
The inverter 15 is, for example, a GTO as shown in the figure.
16, 17, a resistor 18 and a capacitor 19 connected in series, and an inverter transformer 20,
By alternately switching the GTOs 16 and 17, the smoothed current is converted into positive and negative pulse waveforms, and the inverter transformer 20
transforms to high voltage. Here, the resistor 18 connected in series
The capacitor 19 is an absorption circuit for absorbing electromagnetic energy mainly stored in the leakage inductance of the inverter transformer 20 during switching operations of the GTOs 16 and 17, and preventing overvoltage from being applied to the GTOs 16 and 17. The pulse transformed into a high voltage by the inverter 15 is rectified by a rectifier circuit 22 composed of a high voltage rectifier diode 22.
It is supplied to the X-ray tube 23.

The tube voltage of the X-ray tube of this type of X-ray apparatus is controlled by the duty ratio of the chopper 6. In other words, the tube voltage is proportional to the duty ratio of the chopper 6, so
When increasing the tube voltage, increase the duty ratio, and when decreasing the tube voltage, decrease it. Further, the exposure time is mainly determined by the drive time of the chopper 6.

This inverter type X-ray device is equipped with a filter 7 at the next stage of the chopper 6, so the switching elements such as the switching transistor 28 are 10K.
Even at a switching speed of about Hz, the filter 7 smoothes the tube voltage waveform of the X-ray tube 23, which has the advantage that it is less affected by the intermittent waveform caused by the switching operation of the chopper 6.

However, with this inverter-type X-ray device, fluctuations in the power supply voltage and circuits that rectify alternating current as shown in Figure 1, in particular, output ripples directly as tube voltage, resulting in stable Obtaining tube voltage is difficult. The tube voltage of the X-ray tube affects the photographic effect of the X-ray film, and in particular greatly affects the contrast of the X-ray film, which is important for clinical judgment. It is required to suppress the error within the error range. Therefore, it is necessary to take measures to keep the tube voltage stable.

The present invention has been made to address the above points, and by controlling the duty ratio of the chopper according to voltage fluctuations in the power supply section, voltage fluctuations in the power supply section are canceled out and the tube voltage of the X-ray tube is stabilized. The purpose is to provide an X-ray device that maintains

The configuration of the X-ray apparatus of the present invention consists of a power supply section whose purpose is to supply direct current, a chopper that intermittents the current output from the power supply section, and a voltage supplied by the power supply section that adjusts the duty ratio of the chopper. a filter means for smoothing the current intermittent by the chopper; an inverter for transforming the current smoothed by the filter means into a high voltage; It is composed of a rectifying means for rectifying current, and an X-ray tube to which a voltage rectified by the high-voltage rectifying means is applied and irradiating X-rays.

Further, a feedback diode is provided between the filter means and the power supply section.

The feedforward control means included in the X-ray apparatus of the present invention includes a detection means for detecting the voltage supplied from the power supply section, a tube voltage setting section for setting the tube voltage, and a tube voltage setting section for setting the tube voltage. a calculation means for calculating the supplied detection signal and setting signal; a duty ratio setting section for setting the duty ratio of the chopper based on the calculation signal supplied from the calculation means; and a duty ratio setting section supplied from the duty ratio setting section. The present invention is characterized by comprising a chopper drive section that drives the chopper in response to a signal.

Hereinafter, the present invention will be explained with reference to one embodiment of the present invention. FIG. 2 is a circuit configuration diagram of an embodiment of the present invention,
FIG. 3 is an output waveform diagram of each part. As shown in the figure, a power supply section 31 whose purpose is to supply direct current is, for example, connected to an alternating current power supply 30 to rectify the alternating current and prevent overcurrent when a switch (not shown) is closed. A rectifying diode 32 and a thyristor 33 for the purpose of controlling the phase of the thyristor 33,
It is composed of a smooth conductor 58 that gradually charges. Here, the rectified and smoothed current (FIG. 3a) is supplied to the chopper section 34. The chiyotsupa part 34 is
For example, it is composed of a switching element 35 such as a switching transistor, and the output of the power supply section 31 is turned on and off in accordance with a drive pulse supplied from a feedforward control means 59. The feedforward control means 59 is provided between the power supply section 31 and the chopper section 34, and generates a drive pulse with a duty ratio inversely proportional to the output voltage of the power supply section 31. The continuous square wave pulses (FIG. 3b, f) generated by chopper section 34 are supplied to filter means 36.
The filter means 36 is, for example, as shown in the same figure.
Diodes 37, 38 and Chiyoke transformer 39,
40, resistors 41 and 42, and a capacitor 43, and supplies continuous rectangular wave pulses to an inverter section 44 after smoothing (FIG. 3c). The inverter section 44 is composed of a resistor 47 and a capacitor 48 connected in series with switching elements such as GTOs 45 and 46, and an inverter transformer 49.
By alternately switching the GTOs 45 and 46, positive and negative pulses (FIG. 3d) are applied to the inverter transformer 49 to transform it into a high voltage.
Here, a resistor 47 and a capacitor 48 are connected in series.
When switching between GTO45 and 46, the GTO
It functions to absorb electromagnetic energy accumulated in the inverter transformer 49 in order to prevent overvoltage from being applied to the inverter transformer 45 and 46. The positive and negative pulses transformed to high voltage by the inverter section 44 are rectified by a high voltage rectifier 50 comprising a high voltage diode 51 (FIG. 3e), and then applied to the X-ray tube 52.

Further, the feedback diode 60 is provided between the power supply section 31 and the filter 36, and returns the electromagnetic energy accumulated in the choke transformers 39 and 40 to the power supply section 31 when the GTOs 45 and 46 are switched.
This is provided to prevent overvoltage from being applied to the GTOs 45 and 46.

The feedforward control means for driving the chopper 34 detects the output voltage of the power supply section 31, and controls the tube voltage setting section 55 using a detection signal supplied from the isolation amplifier 54, which has excellent insulation from the next stage.
A divider 56 that divides the tube voltage setting signal supplied from the divider 56, a duty ratio setting circuit 57 that sets the duty ratio of the chopper section 34 in accordance with the division signal supplied from the divider 56, and this duty ratio setting circuit 57. and a chopper drive section 53 that drives the chopper 34 according to a duty ratio setting signal supplied from the chopper section 34. Even if the output voltage of the power supply section 31 is unstable due to ripples, the chopper section 3
The duty ratio of 4 is controlled in inverse proportion to the output voltage of the power supply section 31. In other words, when the output voltage of the power supply section 31 is an average value, the detection signal of the isolation amplifier is
If you adjust it so that it is 1 within 6, the power supply section 31
When the output voltage is higher (or lower) than the average value, the division signal supplied from the divider 56 will be smaller (or conversely larger) than the tube voltage setting signal supplied from the tube electric left setting section 55. The duty ratio of the chopper 34 is inversely proportional to the output voltage of the power supply section 31. Therefore, the tube voltage can reduce the influence of fluctuations in the output voltage of the power supply section 31, and is always maintained at the desired value set by the tube voltage setting section. Further, the feed control means having the above configuration can be easily implemented and operates with high precision.

As explained above, according to the present invention, even when the output voltage of the power supply section fluctuates due to ripples etc., it is possible to stably maintain the desired tube voltage. line equipment can be provided.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram of a general inverter type X-ray device, Fig. 2 is a circuit configuration diagram of an inverter type X-ray device which is an embodiment of the present invention, and Fig. 3 is an output waveform diagram of each part. . 30... AC power supply, 31... Power supply section, 32...
Rectifier diode, 33... Thyristor, 34...
Chopper section, 35... Switching transistor, 36... Filter means, 37, 38... Diode, 39, 40... Choker transformer, 4
1, 42...Resistor, 43...Capacitor, 44...
...Inverter section, 45, 46...GTO, 47...
... Resistor, 48 ... Capacitor, 49 ... Inverter transformer, 50 ... High voltage rectifier, 51 ... High voltage diode, 52 ... X-ray tube, 53 ... Chopper drive circuit, 54 ... Isolation amplifier, 55 ... Tube voltage setting section, 56... Divider, 57... Duty ratio setting circuit, 58... Smoothing capacitor, 59...
Feedback control means, 60... Feedback diode, a... Output waveform of 31, b... Output waveform of 34, c... Output waveform of 36, d... 45, 46
An enlarged view of the part indicated by A of the output waveform of e...50, f...a.

Claims (1)

[Scope of Claims] 1. A power supply section that supplies approximately direct current, a chopper that intermittents the direct current, and feed-forward control means that changes the duty ratio of the chopper in inverse proportion to the voltage supplied from the power supply section. A filter means for smoothing the current interrupted by the chopper, an inverter for transforming the current smoothed by the filter means into a high voltage, and a high voltage rectifier for rectifying the current transformed into a high voltage by the inverter. 1. An X-ray apparatus comprising: a means for rectifying high voltage; and an X-ray tube for applying the output of the high-voltage rectifying means. 2. The X-ray apparatus according to claim 1, characterized in that a feedback diode is provided between the power supply section and the filter means. 3. The feedforward control means includes a detection means for detecting the voltage of the power supply section, a tube voltage setting section for setting the tube voltage, a detection signal supplied from the detection means, and a tube voltage setting section supplied from the tube voltage setting section. a calculation means for calculating a voltage setting signal; a duty ratio setting section for setting a duty ratio of the chopper based on the calculation signal supplied from the calculation means;
2. The X-ray apparatus according to claim 1, further comprising a chopper drive section that drives a chopper using a duty ratio setting signal supplied from the duty ratio setting section.