JPH11204290A - Inverter type x-ray high-voltage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter type X-ray high-voltage device capable of obtaining a nearly ideal tube voltage wave-form required for a medical X-ray device without giving a trouble of electromagnetic noise to peripheral apparatuses, requiring a small installation area, and made small-sized and lightweight at a low cost. SOLUTION: This device is provided with a converter circuit 1 rectifying the commercial power to obtain a DC voltage, an inverter circuit 2 receiving the DC voltage from this power supply and converting it into a high-frequency AC voltage and controlling the output voltage (tube voltage), a high-voltage transformer 3 boosting the AC voltage from the inverter circuit 2, a high-voltage rectifying circuit 4 converting the output voltage of the high-voltage transformer 3 into a DC high voltage, and an X-ray tube 6 applied with the DC high voltage from the high-voltage rectifying circuit 4 to emit X-rays. A sheet-like conductor is electrically connected to at least one of two output terminals of the inverter circuit Z, and the extended sheet-like conductor plate is wound on a high-voltage transformer core as the primary winding of the high-voltage transformer 3. The switching element of the inverter circuit 2 is fitted to the outer wall face of a container storing the high-voltage transformer 3 directly or indirectly via a fixed plate having high heat conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter type X-ray high voltage apparatus, and more particularly to an inverter type high voltage transformer and an inductance between a high voltage transformer and a primary winding of the high voltage transformer. The present invention relates to an inverter-type X-ray high-voltage device suitable for downsizing by reduction and higher frequency.

[0002]

2. Description of the Related Art A conventional inverter type X-ray high voltage apparatus will be described with reference to FIG. Inverter circuit 2
Is to apply a high DC voltage (hereinafter referred to as a tube voltage) to the X-ray tube 6 as a load by controlling the phase difference, frequency, pulse width and the like of the inverter circuit 2. That is, an AC voltage from a commercial power supply is converted into a DC voltage by the converter circuit 1 and smoothed by the smoothing capacitor 11 to obtain a DC power supply voltage of the inverter circuit 2. This DC power supply voltage is used as a DC power supply for the inverter circuit 2, and the high-frequency AC voltage output from the inverter circuit 2 is boosted by the high-voltage transformer 3, which is converted to a high-voltage DC by the high-voltage rectifier circuit 4. , To the X-ray tube 6 via the high voltage cable 5. In a device requiring a large output, the inverter circuit 2
In some cases, a capacitor 10 is inserted between the output of the high voltage transformer 3 and the high voltage transformer 3, and a resonance phenomenon between the capacitor 10 and the leakage inductance of the high voltage transformer 3 is used. The high-voltage transformer 3 is usually installed in a high-voltage transformer tank filled with insulating oil together with the high-voltage rectifier circuit 4 for the purpose of securing insulation voltage and cooling. Further, the high-voltage cable 5 has a capacitance, which brings about a tube voltage smoothing action. The tube voltage feedback control circuit 9 detects the actual tube voltage Vx by the tube voltage detector 8 and inputs the tube voltage Vx and the target tube voltage Vr to obtain the phase difference, frequency or pulse width of the inverter circuit 2, and detects the detected tube voltage. Control is performed so that the voltage Vx matches the target tube voltage Vr. The tube current is controlled by adjusting the temperature of the filament of the X-ray tube 6 by a filament heating circuit (not shown).

In the X-ray high-voltage device having the above configuration, the switching element of the inverter circuit 2 includes, for example, an insulated gate bipolar transistor (hereinafter abbreviated as IGBT).
These IGBTs generate heat due to switching loss and conduction loss during X-ray irradiation.However, these IGBTs are usually fixed to a metal having a large heat capacity called a heat sink with radiation fins, and at the same time, a cooling fan, etc. A method of forcibly cooling the heat sink by using the heat sink is used.

The cooling of the inverter circuit of such an inverter type X-ray high voltage apparatus by a heat sink and a cooling fan and the insulation and cooling of the high voltage transformer are performed as follows. That is, the X-ray high-voltage device has a shooting mode in which a large output is exposed for a short time and a fluoroscopy mode in which a small output is exposed for a long time. Although the temperature rises sharply, the temperature of the container that houses the high-voltage transformer (high-voltage transformer tank) almost never rises due to its relatively large volume (large heat capacity) and oil-cooled type. Absent. On the other hand, in the fluoroscopy mode, since the power loss is small, the temperature of the inverter circuit 2 hardly rises, and the temperature of the high-voltage transformer tank also slightly rises compared to the time of photographing.
The rise is very slight. Therefore, the heat sink and the cooling fan are necessary mainly for suppressing the temperature rise of the inverter circuit 2 at the time of photographing, but the insulating oil injected into the high-voltage transformer tank ensures the withstand voltage as described above. At the same time, it has the dual purpose of cooling the high-voltage transformer 3, and the amount of insulating oil injected has been conventionally determined only from the viewpoint of securing the withstand voltage. For example, in order to ensure the withstand voltage between the secondary winding of the high-voltage transformer 3 reaching a maximum of 150 kV and the high-voltage transformer tank which is normally set to the ground potential, a correspondingly large insulation distance must be provided. The space was filled with insulating oil. However, as described above, since the temperature rise of the insulating oil and the high-voltage transformer tank was conventionally very small, the insulating oil to be injected was unnecessarily large from the standpoint of cooling only, and in that sense, it was excessive. It was spec. As described above, since the heat sink and the cooling fan of the inverter circuit 2 require a relatively large volume and weight, and the high-voltage transformer is also large, these are housed in separate housings and arranged separately. Was.

[0005]

As described above, the conventional apparatus has the following problems and points to be improved. (1) The inductance of the wiring between the inverter circuit 2 and the high-voltage transformer 3 and the inductance component of the primary winding of the high-voltage transformer are large, thereby generating electromagnetic noise. Was spent.

Conventionally, in the X-ray high-voltage device having the above-mentioned structure, a copper wire is usually used for an electrical connection from the output of the inverter circuit 2 to the high-voltage transformer 3, which has many inductance components. include. Since a normal copper wire is also used for the primary winding of the high-voltage transformer, the presence of the parasitic inductance component of the circuit including the inductance component due to this winding causes a large high-frequency current by the switching element to be switched every time. L by the above-mentioned inductance (the magnitude of this inductance is L)
Electromagnetic noise is generated by the voltage of × (di / dt),
This adversely affects the control circuit and peripheral devices, and sometimes causes a malfunction. In addition, when an X-ray fluoroscopic image is obtained in combination with an X-ray television apparatus, a drastic improvement has been desired such that much cost and labor must be spent as a measure against the noise. The inductance component causing such a problem is that the inverter circuit 2 and the high-voltage transformer 3 are housed in separate housings, so that the wiring between them is long, and their electrical connection (including the high-voltage transformer) For example, the use of a normal copper wire has a limit in reducing inductance.

(2) Since the operating frequency of the inverter circuit 2 cannot be increased due to the influence of the inductance component, there is a limit in downsizing the high-voltage transformer and improving the tube voltage waveform.

[0008] In recent medical X-ray apparatuses, high-precision, high-reproducibility, large-current, short-time control is required for high-resolution X-ray apparatuses in order to take sharp X-ray pictures with high diagnostic performance. Thus, a tube voltage waveform with a fast rise and no pulsation is required (FIG. 5 shows a comparison between an ideal tube voltage waveform and an actual tube voltage waveform). Also, the rise of the tube voltage,
Higher falling speed is strongly demanded in terms of improving the photographic effect and reducing exposure to soft X-rays, and as means for realizing them, increasing the operating frequency of the inverter is progressing. However, one of the factors that hinder the increase in the operating frequency of the inverter is that the inverter circuit 2
And the inductance of the primary winding of the high voltage transformer from the output of the high voltage transformer 3 to the high voltage transformer 3. If the inverter operating frequency is increased while these inductances are still large, the impedance of the inductance is proportional to the square of the operating frequency.
Current does not sufficiently flow through the load, and a predetermined X-ray output cannot be obtained. Therefore, in order to increase the frequency, it is necessary to reduce these inductance components.

Furthermore, in recent medical X-ray apparatuses, demands for not only the above-mentioned performance but also a reduction in installation area, a reduction in size and weight, and a reduction in price have been increasing. Occupies a high proportion in the volume of the device, and a higher frequency is also required to reduce the size of the high-voltage transformer 3. An object of the present invention is to reduce the inductance component of the wiring between the inverter circuit and the high-voltage transformer and the inductance component of the primary winding of the high-voltage transformer to reduce electromagnetic noise and increase the frequency, and to provide peripheral devices. It is an object of the present invention to provide an inverter-type X-ray high-voltage device that can obtain a tube voltage waveform close to an ideal required for a medical X-ray device without causing any obstacle, and has a small installation area, and is small, light, and inexpensive. is there.

[0010]

SUMMARY OF THE INVENTION The present invention provides a DC power supply,
An inverter circuit for converting the DC power supply voltage into a high-frequency AC voltage, a high-voltage transformer for boosting an output voltage of the inverter circuit, and a high-voltage rectifier circuit for rectifying the output of the high-voltage transformer. Inverter type X for applying a DC high voltage, which is the output voltage of a high voltage rectifier circuit, to an X-ray tube
In the line high-voltage device, a sheet-like conductor is electrically connected to at least one of the two terminals of the output of the inverter circuit, and the sheet-like conductor extended therefrom is connected to the high-voltage transformer. This is achieved by having a primary winding. As described above, by using a sheet-shaped conductor for the wiring between the inverter circuit and the high-voltage transformer and for the primary winding of the high-voltage transformer, the output current of the inverter circuit flows intensively in a specific path (direction). Since there is no wiring, the inductance components of the wiring between the inverter circuit and the high-voltage transformer and the primary winding of the high-voltage transformer can be reduced. Therefore, the switching element of the inverter circuit generates a large high-frequency current by L (di / d) by the inductance (L is the inductance) at each switching.
Electromagnetic noise generated by the voltage of t) can be suppressed, which can prevent a control circuit and peripheral devices from being adversely affected and causing a malfunction. In particular, when an X-ray fluoroscopic image is obtained in combination with an X-ray television apparatus, the cost and labor of the noise countermeasures can be reduced, so that the effect is large.

Further, the switching element of the inverter circuit is mounted directly or indirectly via a fixing plate having a high thermal conductivity on the outer wall surface of the container housing the high-voltage transformer, whereby the inverter circuit is mounted. Wiring distance between the power supply and the high-voltage transformer. As a result, the inductance component of the wiring between the inverter circuit and the high-voltage transformer is further reduced, so that the above-mentioned measures against electromagnetic noise are further reduced.

Further, by reducing the inductance components of the wiring between the inverter circuit and the high-voltage transformer and the primary winding of the high-voltage transformer by the above method, the operating frequency of the inverter circuit can be further increased. Further, the size of the high-voltage transformer can be further reduced.

By using the above solution, it is possible to obtain a tube voltage waveform close to an ideal required for a medical X-ray apparatus without causing electromagnetic noise to interfere with peripheral devices, and to further reduce the installation area. It is possible to obtain a small, compact, lightweight and inexpensive inverter type X-ray high voltage device.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a mounting diagram of an inverter type X-ray high voltage device according to the present invention. This X-ray high-voltage device converts a DC voltage from a converter circuit into a high-frequency AC voltage using an inverter circuit, boosts the output voltage, rectifies the voltage, supplies the DC voltage to an X-ray tube, And a converter circuit 1, an inverter circuit 2, a high-voltage transformer 3, a high-voltage rectifier circuit 4, a high-voltage cable 5, an X-ray tube 6, and the like shown in the circuit diagram of FIG. ,
It comprises a tube voltage detector 8, a tube voltage feedback control device 9 by a digital control method, and the like.

FIG. 1 does not show the X-ray tube 6, the tube voltage detector 8, and the tube voltage feedback control device 9 based on the digital control method.

Next, the functions of the above components will be described with reference to FIGS.
Each will be described briefly with reference to FIG. The converter circuit 1 is a device for supplying a DC voltage.
The DC voltage is obtained by rectifying the voltage of the commercial power supply of Hz or 60 Hz and smoothing the rectified voltage by the smoothing capacitor 11. The inverter circuit 2 receives the DC voltage output from the converter circuit 1, converts the DC voltage into a high-frequency AC voltage, and controls the voltage (hereinafter, tube voltage) output to the X-ray tube. High voltage transformer 3
Is for boosting the AC voltage from the inverter circuit 2, and its primary winding is connected to the output side of the inverter circuit 2.

The X-ray tube 6 receives the output voltage from the high voltage rectifier circuit 4 through the high voltage cable 5 and emits X-rays, and is connected to the output side of the high voltage rectifier circuit 4. . The high-voltage cable 5 has a cable head 19 that matches the shape of the bushing 18, thereby connecting to the X-ray tube 6. The tube voltage detector 8 detects a tube voltage supplied to the X-ray tube 6 and sends out a tube voltage signal Vx to the inverter circuit 2.
Is connected to the input side of the X-ray tube 6. The feedback control device 9 receives the target tube voltage signal Vr and the tube voltage signal Vx detected by the tube voltage detector 8, compares the target tube voltage signal Vr with the tube voltage signal Vx, and calculates the X-ray. The control signal S is sent to the inverter circuit 2 so that the tube voltage signal Vx of the tube 6 becomes a predetermined voltage.

Here, first, the configuration and parts arrangement of the tank 12 of the inverter circuit 2 and the high-voltage transformer 3 will be described. In the main circuit according to the present embodiment, as shown in FIG. 3, the converter circuit 1 and the inverter circuit 2 both use four switching elements IGBT, and two IGBTs are built in one package as shown in FIG. Two IGBT modules 13 of the same type are used to form a full bridge. In the converter circuit 1 and the inverter circuit 2 according to the present invention, the IGBT module 13 as a switching element has a high-voltage transformer 3, a high-voltage rectifier 4, a bushing 18 and the like built in by volts, and a high voltage into which insulating oil 20 is injected. The transformer tank 12 is fixed and held in close contact with one outer wall surface.

Further, a large-capacity aluminum electrolytic capacitor is used as the smoothing capacitor 11 for smoothing the output voltage of the converter circuit 1, and two aluminum electrolytic capacitors are connected in series to increase the withstand voltage.

The smoothing capacitor 11, together with the converter circuit 1 and the inverter circuit 2, is fixed and held (not shown) by a support or the like (not shown) so that its axis is along the outer wall surface of the high-voltage transformer tank 12. Next, a method of electrically connecting the above-described main circuit components will be mainly described.

The capacitor 11 for smoothing the output voltage of the converter circuit 1 reduces the inductance component of the wiring to suppress the surge voltage at the time of switching of the IGBT, and at the same time, the components are arranged in a minimum space.
As close as possible to the GBT module 13.

As shown in FIG. 1, the capacitor 11 is a thin and wide copper plate 2 capable of securing necessary current capacity and withstand voltage.
1 (there may be a bent shape if necessary) using the IGB of the converter circuit 1 and the inverter circuit 2.
It is electrically connected to the T module 13 at the shortest distance to reduce the inductance component of the wiring between the smoothing capacitor 11 and the converter circuit 1.

FIG. 4 shows an equivalent circuit of the IGBT module 13 having three terminals.
One terminal corresponds to each of the terminals C1, C2E1, and E2 in FIG. On the upper surface of the IGBT module 13, a snubber circuit for suppressing a surge voltage at the time of switching is required, and wiring (not shown) for driving the IGBT is required. Therefore, if the space on the upper surface of the IGBT module 13 is too complicated, There is a need for a unique implementation.

For this reason, in the example of FIG.
The “E2” terminal of the IGBT module 13 for use is electrically connected to the minus terminal of the smoothing capacitor 11 (2) via a copper plate 21 provided along the side surface of the IGBT module 13 near the smoothing capacitor 11. ing.

Next, a method of electrically connecting the inverter circuit 2 and the high-voltage transformer 3, which is a main part of the present invention, will be described in detail. The wiring 14 from the inverter circuit 2 to the high-voltage transformer 3 has two output terminals 31 and 32 of the inverter circuit 2 in order to reduce the inductance of the wiring therebetween.
Are electrically connected to each other, and extend in the direction of the high-voltage transformer 3. The extended sheet-shaped conductor has a cross-sectional area capable of securing a required current capacity, and is as thin and wide as possible. Only the primary side is provided with a high-voltage transformer that is discharged outside the high-voltage transformer tank 12. , And is used as it is as a primary winding of the high-voltage transformer 3.

Output terminal 3 of the two inverter circuits
The two sheet-like primary windings electrically connected to the first and second windings 32 are positioned outside the high-voltage transformer tank 12 while securing the withstand voltage with the insulating paper 16 interposed therebetween. Is wound around one leg of the transformer core 7
These two sheet-shaped windings are wound in opposite directions, and are connected to each other by a copper wire inside the sheet-shaped winding (on the side close to the iron core 7). The surface of the sheet-shaped conductor is covered with insulating paper 16 to enhance the withstand voltage and improve safety. The secondary winding 15 of the high-voltage transformer 3 has a voltage of 15
Since it reaches 0 kV, it is immersed in insulating oil, and its output reaches a high-voltage rectifier 4 provided below the high-voltage transformer 3 and passes through an X-ray tube 6 via a bushing 18 and a high-voltage cable 5. Leads to. The switching element I
The GBT module 13 is not directly fixed to the outer wall surface of the high-voltage transformer tank 12 as described above, but is temporarily mounted on a fixed plate made of a thin metal or the like having a high heat transfer coefficient and a mechanical strength. The fixing plate may be fixed together with the smoothing capacitor 11 and the fixing plate may be fixed and held on the outer wall surface of the high-voltage transformer tank 12.

On the other hand, although not shown, the X-ray control circuit 9 can be fixed to the front surface of the IGBT module 13 by providing a support on the outer wall surface to which the inverter circuit 2 is fixed.

The inverter circuit 2 and the high-voltage transformer 3 are electrically connected to each other by the sheet-shaped conductor as described above, and the inverter circuit 2 is directly fixed to the high-voltage transformer tank 12. 2 and the high-voltage transformer 3 become very short, and the output current of the inverter circuit does not concentrate on a specific path (direction), so that the equivalent inductance can be reduced. It is possible to suppress occurrence.

As described above, when the inverter circuit 2 is directly fixed to the high-voltage transformer tank 12, heat generation of the switching element of the inverter circuit 2 is suppressed as follows.

A part of the heat generated by the IGBT module 13 is directly transmitted to the surrounding air, electric wiring paths, and support members of each component in each of the processes described below, but most of the heat is generated by the IGBT module. 13 to the wall of the high-voltage transformer tank 12 from this case (after interposition of the fixing plate when a fixing plate is used).
The power is sequentially transmitted from the wall surface of the high-voltage transformer tank 12 to the insulating oil 20 inside the high-voltage transformer tank 12. I above
For example, silicon grease is applied between gaps between the GBT module 13 and the outer wall surface of the high-voltage transformer tank 12 to increase the degree of adhesion between them (by reducing the contact thermal resistance by increasing the contact area). , IGBT module 1
The heat generated in the IGBT module 13 is efficiently transmitted to the high-voltage transformer tank 12 having a large heat capacity to enhance the cooling effect of the IGBT module 13. As described above, conventionally, the insulating oil 20 in the high-voltage transformer tank 12 is unnecessarily large in view of the purpose of cooling only the high-voltage transformer 3 and has not been used effectively. With such a configuration, the insulating oil 20 can be used not only for the high voltage transformer 3 but also for the I
It can also be effectively used for cooling the GBT module 13, and provides a well-balanced thermal design for the inverter type X-ray high voltage device.

In FIG. 1, the inverter circuit 2
Both of the two output terminals 31 and 32 have extended conductor plates, which are used directly as primary windings of the high-voltage transformer 3.
2 (shown in FIG. 2), a capacitor may be connected between the output of the inverter circuit 2 and the high-voltage transformer 3 by using a copper wire on one of the output terminals of the inverter circuit 2. It is also possible to connect the inverter output terminal on one side to the resonance capacitor 10 and the resonance capacitor 10 to the high-voltage transformer 3 with a conductor plate.

Further, in FIG. 1, the output voltage of the high-voltage rectifier 4 is output to the high-voltage cable 5 through the side of the high-voltage transformer tank 12, but the space on the side of the high-voltage transformer tank 12 is made effective. For example, when it is desired to use the high-voltage transformer tank 12, the output may be made via the upper surface of the high-voltage transformer tank 12.

The primary side of the high-voltage transformer 3 is taken out of the upper surface of the high-voltage transformer tank 12 to the outside. You may make it go out further. Also,
In the above embodiment, the inverter circuit 2 has a circuit system of a full bridge configuration. However, the invention is not limited to this, and an inverter circuit system of a half bridge configuration may be used.

In this configuration, the number of switching elements is smaller than that of the full-bridge configuration, so that there is an effect that mounting is simplified. The converter circuit 1
Has I in all four switching elements of the full bridge.
Although a converter circuit using a GBT is applied, this is a converter circuit in which one of the two IGBT modules for the converter circuit 1 is a diode module although the power factor is slightly lower than that of the converter circuit in FIG. May be used.

Alternatively, without using any IGBT,
A rectification system in which a diode module or a thyristor module is arranged instead of the T module 13 may be used. However, in this case, since the diode or thyristor operates only at the commercial frequency, heat generation is not a serious problem.There is no need to increase the cooling effect by installing it on a fixed plate, and install it in consideration of other components. It should just be placed in a place that is easy to do.

Further, in the above embodiment, the IGBT
The electrical connection between the modules 13 and between the IGBT module 13 and the smoothing capacitor 11 uses the copper plate 21, but the electrical connection may use a copper plate or an electric wire.

[0037]

As described above, according to the present invention, the inductance of the wiring between the inverter circuit and the high-voltage transformer and the inductance of the primary winding of the high-voltage transformer can be reduced. Generation of noise can be suppressed. In particular, when obtaining an X-ray fluoroscopic image in combination with an X-ray television apparatus, it is not necessary to spend much cost and labor as a measure against noise.

Further, since the operating frequency of the inverter circuit can be further increased, it is possible to obtain the effects of further reducing the size of the high-voltage transformer and obtaining an ideal tube voltage waveform.

[Brief description of the drawings]

FIG. 1 is a mounting diagram of an inverter type X-ray high voltage device showing a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of an inverter type X-ray high voltage device.

FIG. 3 is a circuit diagram of a converter circuit and an inverter circuit according to the first embodiment of the present invention shown in FIG.

FIG. 4 is an equivalent circuit diagram of the IGBT module used in the embodiment shown in FIG.

FIG. 5 is an ideal waveform diagram and an actual waveform diagram of a tube voltage in the medical X-ray apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Converter circuit 2 Inverter circuit 3 High-voltage transformer 4 High-voltage rectifier 5 High-voltage cable 6 X-ray tube 7 High-voltage transformer core 10 Resonance capacitor 11 Smoothing capacitor 12 High-voltage transformer storage container 13 IGBT module 14 From inverter circuit Wiring to high-voltage transformer (including high-voltage transformer primary winding) 15 High-voltage transformer secondary winding 16 Insulating paper 17 Capacitor support 18 Bushing 19 Cable head 20 Insulating oil 21 Copper plate

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05G 1/20 H05G 1/20

Claims (2)

[Claims] 1. A DC power supply, an inverter circuit for converting the DC power supply voltage into a high-frequency AC voltage, a high-voltage transformer for boosting an output voltage of the inverter circuit, and rectifying an output of the high-voltage transformer. A high-voltage rectifier circuit, wherein the inverter-type X-ray high-voltage device for applying a DC high voltage, which is an output voltage of the high-voltage rectifier circuit, to an X-ray tube; An inverter-type X-ray high-voltage device, wherein a sheet-like conductor is electrically connected to one of them, and the sheet-like conductor extended therefrom is used as a primary winding of the high-voltage transformer. 2. The switching element of the inverter circuit is directly or indirectly mounted on an outer wall surface of a container housing the high-voltage transformer via a fixed plate having a high thermal conductivity. Item 2. An inverter type X-ray high voltage device according to item 1.