JPH0719667B2 - X-ray equipment - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an X-ray apparatus for generating a high voltage used for X-ray generation, and more particularly to an apparatus for reducing ripple components contained in the high voltage. .

[Technical background of the invention and its problems]

An X-ray device usually has a voltage adjusting unit, such as a chopper unit, for adjusting the voltage of a DC voltage by switching, and an inverter unit for converting the output (DC voltage) of the chopper unit into an AC voltage. The high voltage (tube voltage) is obtained by boosting the voltage and converting it to a DC voltage.

The chopper section and the inverter section are driven separately, but by setting the drive frequency of the inverter section to several kHz to several tens of kHz (high frequency), downsizing of the step-up transformer and reduction of the ripple component contained in the tube voltage can be achieved. Has been planned.

However, even if the drive frequency of the inverter section is increased, the ripple component contained in the tube voltage does not decrease so much due to the relationship with the drive frequency of the chopper section. This is because the drive frequency of the inverter unit has come very close to the drive frequency of the chopper unit as the frequency of the inverter unit has become higher, and the mutual influence between the two cannot be ignored.

If the drive frequency of the chopper section is made much higher than that of the inverter section, the above problem will be solved, but if the capacity becomes large (for example, 100 kVA) like an X-ray device, the drive frequency of the chopper section will be changed to that of the inverter section. It is technically extremely difficult to make it much higher than.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to convert the drive frequency of a voltage adjusting unit that adjusts the voltage of a DC voltage by switching and the output of the voltage adjusting unit into an AC voltage. It is an object of the present invention to provide an X-ray device in which the ripple component contained in the tube voltage is extremely small even though the difference with the drive frequency of the inverter unit is small.

[Outline of Invention]

The present invention has a voltage adjustment unit that adjusts the voltage of a DC voltage by switching, and an inverter unit that converts the output of this voltage adjustment unit into an AC voltage. Based on the output of the inverter unit, it is used for X-ray generation. In the X-ray device that generates a high voltage, the drive control of the voltage adjusting unit and the inverter unit is performed, and the ripple component generated in the tube voltage due to the voltage adjusting unit and the tube voltage due to the inverter unit are generated. It is characterized by comprising a control unit for driving and controlling the voltage adjusting unit and the inverter unit so that the frequencies of both ripple components are matched and a predetermined phase difference is given between them.

Example of Invention

First, the principle of the present invention will be described with reference to FIGS.

FIG. 5 shows a temporal change in the tube voltage when the driving frequency of the chopper, which is the voltage adjusting unit, is higher than the driving frequency of the inverter. The change in tube voltage when the ripple component caused by the inverter is assumed to be zero is shown in FIG.
And ΔV ₁ becomes a ripple component caused by the chopper section. On the contrary, when the ripple component generated in the chopper portion is assumed to be zero, the tube voltage change is as shown in FIG. 2, and ΔV ₂ is the ripple component generated in the inverter portion. Thus, since the ripple components ΔV ₁ and ΔV ₂ are generated due to both the chopper portion and the inverter portion, the actual tube voltage change is as shown in FIG. 3, and the combined ripple of ΔV ₁ + ΔV _{2 is} obtained. Appears.

FIG. 6 shows a temporal change in the tube voltage when the drive frequency of the chopper part and the drive frequency of the inverter part are equal and the phases between the two are the same. Ripple components ΔV ₁ and ΔV ₂ are generated due to the chopper portion and the inverter portion, respectively, so that a combined ripple of ΔV ₁ + ΔV ₂ actually occurs in the tube voltage.

However, by matching the frequencies of both the ripple component caused by the chopper portion and the ripple component caused by the inverter portion and by providing a phase difference of 180 ° between them, the change in the tube voltage is shown in FIG. As shown in Fig. 5, due to the chopper and inverter, ΔV ₁ and ΔV ₂ respectively.
However, since there is a phase difference of 180 ° between them, the ripple component contained in the actual tube voltage is canceled and reduced.

Next, an embodiment of the present invention based on the above principle will be described.

FIG. 1 is a block diagram of an X-ray apparatus which is an embodiment of the present invention. Reference numeral 10 is a rectifying / smoothing unit that rectifies and smoothes the three-phase AC voltage that is taken in, and 11 is a voltage adjusting unit that adjusts the voltage of the DC voltage. A chopper section 12 is applied to this voltage adjusting section 11. Reference numeral 13 is an inverter unit that converts the output of the chopper unit 12 into AC voltage, and 14 is a step-up transformer that steps up the output of the inverter unit 13. Reference numeral 15 is a rectifying / smoothing unit that rectifies and smoothes the AC voltage boosted by the boosting transformer 14, and 16 is an X-ray tube. The output of the rectifying / smoothing unit 15 is applied between the anode and cathode of the X-ray tube 16.

Further, 18 controls the drive of the chopper section 12 and the inverter section 13, and matches the frequencies of both the ripple component caused by the chopper section 12 and the ripple component caused by the inverter section 13. And
It is a control unit that gives a predetermined phase difference between the two. The control unit 18 controls the pulse signal (frequency
₀₎ generates a drive pulse frequency _0/2 on the basis of the inverter control circuit 18 for outputting it to the inverter section 13
a, a phase shift circuit 18b that shifts the phase of the pulse signal from the oscillator 19, and a chopper control that generates a drive pulse of frequency ₀ based on the output of the phase shift circuit 18b and outputs this to the chopper unit 12. And a circuit 18c.

A condition setting unit 17 sets various conditions such as tube voltage, tube current, and tube voltage application time. The chopper control circuit 18c controls the pulse width, the number of pulses, etc. of the drive pulse in accordance with the set conditions.

Next, the details of the rectifying / smoothing unit 10, the chopper unit 12, the inverter unit 13, and the rectifying / smoothing unit 15 will be described with reference to FIG.

The rectifying / smoothing unit 10 is a bridge rectifier that rectifies a three-phase AC voltage.
It comprises D ₁ , a coil L ₁ for smoothing the rectified output, and a capacitor C ₁ .

The chopper unit 12 includes a transistor Q ₁ that opens and closes according to a drive pulse from the chopper control circuit 18c, a freewheeling diode D ₂ , a coil L ₂ and a capacitor C ₂
And.

Further, the inverter unit 13 includes a coil L ₃ and transistors Q ₂ and Q ₃ which alternately open and close according to a drive pulse from the inverter control circuit 18a.

The rectifying / smoothing unit 15 includes bridge rectifiers D ₃ and D ₄ connected in series with each other, and capacitors C ₃ and C ₄ connected in series with each other.

Next, the operation of the embodiment apparatus configured as described above will be described with reference to FIGS. 3 (a), (b) and FIG.

FIG. 3 (a) is a timing chart showing the relationship between the inverter operation mode, the inverter output and the tube voltage change, FIG. 3 (b) is a timing chart showing the relationship between the chopper operation mode and the tube voltage change, and FIG. It is a waveform diagram which shows an actual tube voltage change.

The three-phase AC voltage is converted into a DC voltage by the rectifying / smoothing unit 10, and the converted DC voltage is input to the chopper unit 12 and used for voltage adjustment. The output of the chopper section 12 is converted into an AC voltage by the inverter section 13, boosted by the step-up transformer 14, and then rectified and smoothed by the rectifying and smoothing section 15.
It is applied to the X-ray tube 16.

Here, the transistors Q ₁ , Q in the inverter unit 13
₂ is alternately opened and closed according to the drive pulse from the inverter control circuit 18a, so that the inverter output has an AC waveform as shown by 20 in FIG. 3 (a). The tube voltage change when the ripple component generated in the chopper unit 12 is assumed to be zero is shown in FIG. 21, which rises in the Ut cycle and falls in the Dt cycle.

On the other hand, the transistor Q ₁ in the chopper section 12 opens and closes in accordance with the drive pulse from the chopper control circuit 18c. Since the phase of this drive pulse lags the phase of the pulse signal from the oscillator 19 by 180 °, for example, the inverter Ripple component caused by section 13 and inverter section 13
The frequency of the ripple component included in the tube voltage is four times the inverter drive frequency by matching the frequencies of both the ripple components caused by the above and giving a predetermined phase difference (for example, 180 °) between them. Frequency (frequency twice the frequency of the ripple generated in the inverter unit 13),
The level can be lowered. Further, since the ripple component is reduced by such a method, it is possible to reduce the values of the coil, the capacitor and the like on the primary side of the step-up transformer 14, thereby reducing the size of the X-ray apparatus and further. Can greatly improve responsiveness.

Although one embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to the above embodiment and various modifications can be made. For example, in the above embodiment has been described an application of the chopper unit 12 as a voltage adjusting unit 11, a bridge rectifier D ₁ in the rectifying and smoothing portion 10 and a thyristor (SCR), a voltage regulator of the DC voltage by the phase control of the thyristor May be performed. In this case, the voltage adjusting unit is configured to include the rectifying / smoothing unit and the chopper unit.

〔The invention's effect〕

As described above in detail, according to the present invention, the difference between the drive frequency of the voltage adjustment unit that adjusts the voltage of the DC voltage by switching and the drive frequency of the inverter unit that converts the output of the voltage adjustment unit into the AC voltage is small. Nevertheless, it is possible to provide the X-ray device in which the ripple component contained in the tube voltage is extremely small.

[Brief description of drawings]

FIG. 1 is a block diagram of an X-ray apparatus which is an embodiment of the present invention,
FIG. 2 is a circuit diagram showing the configuration of the main part of FIG. 1, and FIG. 3 (a) is an inverter operation mode in the device of this embodiment.
FIG. 4B is a timing diagram showing the relationship between the inverter output and the tube voltage change. FIG. 3B is a timing diagram showing the relationship between the chopper operation mode and the tube voltage change in the apparatus of this embodiment.
FIG. 5 is a waveform diagram showing changes in the tube voltage actually applied to the X-ray tube in the apparatus of this embodiment, and FIGS. 5 to 7 are waveform diagrams for explaining the principle of the present invention. 11 …… Voltage adjustment unit, 13 …… Inverter unit, 18 …… Control unit.

Claims (1)

[Claims] 1. A voltage adjusting unit for adjusting the voltage of a DC voltage by switching, and an inverter unit for converting the output of the voltage adjusting unit into an AC voltage, wherein X-ray generation is performed based on the output of the inverter unit. In an X-ray device that generates a high voltage to be supplied, drive control of the voltage adjustment unit and the inverter unit is performed, and a ripple component generated in the tube voltage due to the voltage adjustment unit and the tube voltage due to the inverter unit An X-ray device comprising: a control unit that drives and controls the voltage adjustment unit and the inverter unit so that the frequencies of both the generated ripple components coincide with each other and that a predetermined phase difference is given between them.