JPS62165899A - Inverter type x-ray generator - Google Patents

Abstract

PURPOSE:To enable any distorsion in a tube voltage waveform caused by voltage drop of a filter capacitor to be eliminated without increasing the capacitance of the filter capacitor, by setting the output voltage of a chopper during operation of a DC voltage source and the chopper higher than the output voltage of the chopper during the operation of the DC voltage source, the chopper and an inverter. CONSTITUTION:X ray is generated by operating only a DC voltage source first, then the DC voltage source and a shopper, and lastly the DC voltage source, the chopper and an inverter, while setting the chopper output voltage during the operation of the DC voltage source and the chopper higher than the chopper output voltage during the operation of the DC voltage source, the chopper and the inverter. Namely, the chopper 2 is of so-called boosting type. When a switching element 15 is in conductive state, a reactor 16 stores current energy presented by voltage V1 which is released through a diode 17 to charge a smoothing filter capacitor 9 when the switching element 15 is not in conductive state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an improvement in an inverter type X-ray apparatus.

[Background of the invention]

Currently, mwa-style X-ray equipment and Sanwa-style X-ray equipment are often used as medical X-ray equipment. Single-phase X-ray devices have problems in that the tube voltage waveform applied to the X-ray tube is sinusoidal, so there are many ripples, and the tube voltage region above a certain level that contributes to medical diagnosis is narrow. On the other hand, the Sanwa-type X-ray device has relatively little ripple and can obtain high-output X-rays, but
The problem is that the device is structurally large and occupies a high floor space in the hospital.

Therefore, in recent years, commercial AC power is first converted to DC power, and then reconverted to AC voltage with a higher frequency at the subsequent stage.
A so-called inverter type X-ray apparatus has been proposed (see Japanese Patent Application Laid-open No. 78499/1983).

In this type of device, the voltage can be adjusted using the DC voltage converter or chopper, so there is no need for the conventional auto-transformer for voltage adjustment, and the frequency of the voltage applied to the high-voltage transformer for step-up is eliminated. Since this can be made arbitrarily high, the high voltage transformer itself can be made smaller, and the entire device can be made smaller. In addition, since it is converted to direct current once, the tube voltage waveform can be made into a rectangular waveform, making it ideal for medical diagnosis.
It has the advantage of widening the E pressure area.

Incidentally, an inverter type X-ray apparatus requires a smoothing filter capacitor due to its circuit configuration.

This filter capacitor is a large component, so
It is set only to the minimum capacitance necessary for voltage smoothing during radiation exposure. Therefore, at the start of X-ray exposure, a large current flows due to sudden changes in load or charging of the capacitance of the high-voltage cable, causing a temporary drop in the voltage of the filter capacitor and distorting the tube voltage waveform. There was a problem.

[Purpose of the invention]

The present invention was made in order to solve the two problems described above, and it is possible to eliminate the distortion of the tube voltage waveform caused by the voltage drop of the filter capacitor without increasing the capacitance of the filter capacitor. The purpose is to provide an inverter-type X-ray device that can

[Summary of the invention]

The device of the present invention is an inverter-type X-ray device that operates in the order of the DC voltage source, then the DC voltage source and the chopper, and finally the DC voltage source, chopper, and inverter during X-ray exposure. and the chopper output voltage when operating the chopper.

The above object is achieved by setting the chopper output voltage higher than the chopper output voltage when operating the DC voltage source, chopper, and inverter.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of an inverter type X-ray apparatus according to the present invention, and in the figure, 1 indicates a DC voltage source. The output DC voltage (1) of this DC voltage rAl is converted into a DC-DC voltage by the chopper 2, and becomes a DC voltage v2. This voltage v2 is DC-AC converted by the inverter 3 and then input to the high voltage transformer 4, where it is boosted. The output AC voltage of the high voltage transformer 4 is rectified by a high voltage rectifier 5 and then applied to the X-ray tube 6 as a tube voltage 8.

Here, the DC'di pressure source 1 is configured, for example, to convert a commercial AC power source to M'dtδ using a thyristor (not shown), and its output DC voltage (1) is adjustable. Further, the voltage (1) is divided by a voltage dividing resistor 7, compared with a DC voltage source set voltage Vl)o in an error amplifier 8, and then fed back to the DC voltage source 1. That is, the voltage (1) can be stably adjusted to any voltage by setting the voltage VOO. Further, the DC voltage source 1 is started to be driven by the X-ray exposure preparation signal A.

The chopper 2 is a so-called step-up chopper, and while the switching element 15 is in the conductive state, the reactor 16 stores the voltage vi as current energy, and while the switching element 15 is in the non-conductive state, the current energy of the reactor 16 is stored in the diode. 17 to charge the filter capacitor 9 for filtering, and store it as upper pressure energy.

In this way, the capacitor 9 is connected in advance to the reactor 1
6 and the diode 17 to the same level as the voltage 1, and the output voltage 2 is the switching element 1.
According to the conduction time of 5, the voltage increases by the amount of 'l'LL flow energy.

This -fa pressure 2 is divided by a voltage dividing resistor 10,
In the error amplifier 11, the duty setting voltage generator 12
It is compared with the output voltage VD of . The output voltage of the error amplifier 11 is converted into a signal having an arbitrary frequency and duty by a voltage-to-duty converter 13 containing an oscillator (not shown). This duty signal is driver 1
4 becomes a drive signal for the switching element 15, forming a feedback loop for the chopper 2. Note that the chopper 2 starts its operation in response to the X-ray exposure signal B input to the driver 14.

FIG. 2 is a circuit diagram showing a specific example of the duty setting voltage generator 12. In this FIG. 2, analog switches 18, 1.9 and 20 are connected to the signal A.

When B and chopper no-load operation signal C become active, conduction occurs. When each of these analog switches 18.19°20 becomes conductive, the duty setting reference voltage Vo++
VD2+v,3 is input to the adder 21 and output as the duty setting voltage VD. In addition, 22 is a delay circuit, 23 is an inverter, and 24.25 is an AND circuit, and the output signal of the AND circuit 24 is used as the signal C. Further, the output signal of the AND circuit 25 is used as an inverter operation start signal, which will be described later.

That is, the duty setting voltage generator 12 not only generates the duty setting voltage but also generates an inverter operation start signal.

Next, the operation of the above-described apparatus of the present invention will be explained with reference to FIG. First, the exposure preparation signal A is x&! 0 at the start of exposure.
This signal A is generated approximately 1 to 1 second before the signal A, and normally the rotation of the anode of the X-ray tube 6 and the heating of the cathode heater are started. This signal A also starts the operation of the DC voltage source 1 and sets the voltages vl and v2 to the set voltage VDO. Signal A is simultaneously applied to the analog switch 18 in the duty setting voltage generator 12.
is made conductive, and the voltage vD1 is output as the duty setting voltage.

At this time, the duty setting voltage V
D, that is, voltage VDI, is set to the same voltage as the set voltage VDO. As a result, the disturbance element added to the feedback loop of the chopper 2 when only the DC voltage source 1 is operated is reduced, and the chopper 2 outputs a voltage v
2. It operates stably without causing any vibration. Also, the voltage Vo (=vD, ) is gradually raised. That is, by performing a soft start, inrush current that occurs when charging the filter capacitor 9 can be prevented.

In addition, the X-ray exposure signal B is delayed by a time T by a delay circuit 22, inverted by an inverter 23, and then input to an AND circuit 24 together with the original signal B to perform an AND operation. It is assumed to be signal C. While this signal C is active, the analog switch 20 is conductive, and at this time, the analog switch 19 is also conductive due to the signal B, so the voltage V becomes a voltage of (1) VDZ+VD3. Furthermore, since the chopper 2 starts operating at the same time as the signal B is input, the voltage v2 of the capacitor 9 is increased as shown in FIG. moreover,
The signal B is sent to the AND circuit 25 together with the output signal of the delay circuit 22.
It is also inputted and ANDed, which is used as the inverter operation start signal. When the inverter 3 starts operating due to this signal, the X-ray tube 6 is added as a load, and a large load current flows due to charging of the capacitance of the high voltage cable, and the voltage v2 of the capacitor 9 is as shown in FIG. As such, it decreases by ΔV. If the voltage VD3 is not applied, the voltage 2 will have a depressed waveform as shown by the dotted line in FIG. 3, and the tube voltage vx will also be distorted as shown by the dotted line. However, in order to obtain the desired tube voltage value, the duty setting voltage VD is set to Vold+vD2+■D3 from the time of the start of exposure, so the voltage v2 of the capacitor 9 does not drop significantly and is 1. The tube voltage v8 also has a waveform without distortion, as shown by the solid line in FIG.

Note that the degree of drop in voltage v2 at the start of operation of inverter 3 is determined by the load condition of X-ray tube 6 (tube voltage).

It varies depending on the tube current, etc.). Therefore, the above voltage
The voltage VD3 required to eliminate the drop of 2 varies depending on the above load conditions. For this reason, it is desirable that the voltage vo3 be changed in accordance with the set load conditions (changed greatly when the load is large, and changed small when the load is small).

〔Effect of the invention〕

As described above, according to the present invention, it is possible to remove the distortion of the tube voltage waveform caused by the voltage drop of the filter capacitor at the start of inverter operation, and to do so without increasing the capacitance of the filter capacitor. This can be achieved by simply setting the order in which the DC voltage source, chopper, and inverter are operated and the chopper output voltage, and has the advantage of reducing the size and cost of the configuration.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the device of the present invention, Fig. 2 is a circuit diagram showing a specific example of the duty setting voltage generator in Fig. 1, and Fig. 3 explains the operation of the device of the present invention. This is a timing chart for DESCRIPTION OF SYMBOLS 1... DC voltage source, 2... Chopper, 3... Inverter, 4... High voltage transformer, 5... High voltage rectifier, 6...
... X-ray tube, 8, 11 ... error amplifier, 9 ... filter capacitor, 12 ... duty setting voltage generator, 13 ... voltage-duty converter, 14 ... driver. Figure 2

Claims (3)

[Claims] (1) DC voltage source and the output voltage of this DC voltage source
- A chopper that converts DC, a filter capacitor that smoothes the output voltage of this chopper, an inverter that converts the output voltage of the chopper smoothed by this filter capacitor from DC to AC, and a high voltage transformer that boosts the output voltage of this inverter. In an inverter-type X-ray apparatus comprising a high-voltage rectifier that rectifies the output voltage of the high-voltage transformer, and an X-ray tube to which the output voltage of the high-voltage rectifier is applied, when irradiating X-rays, first the Only the DC voltage source is operated, then this DC voltage source and the chopper, and finally the DC voltage source, the chopper, and the inverter are operated in this order, and the chopper is operated when the DC voltage source and the chopper are operated. An inverter-type X-ray apparatus characterized in that the inverter-type X-ray apparatus is equipped with a control means for setting an output voltage higher than a chopper output voltage when operating the DC voltage source, the chopper, and the inverter. (2) The control means sets a duty setting voltage for setting the output voltage of the chopper when only the DC voltage source is operated, so that the output voltage of the chopper is equal to the output voltage of the DC voltage source. The inverter-type X-ray apparatus according to claim 1, wherein the inverter-type X-ray apparatus is controlled so that (3) The control means controls the extent to which the output voltage of the chopper when operating the DC voltage source and the chopper is higher than the chopper output voltage when operating the DC voltage source, the chopper, and the inverter. The inverter-type X-ray apparatus according to claim 1 or 2, wherein the inverter-type X-ray apparatus is changed according to load conditions of the X-ray tube.