JP3021122B2 - DC high voltage generator and X-ray apparatus using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC high voltage generator suitable for supplying a high voltage to an X-ray tube, and an X-ray apparatus provided with the DC high voltage generator.

2. Description of the Related Art In recent years, power supplies for X-rays using high-frequency inverters of several kHz to several tens of kHz have been put into practical use due to the advantages of high-speed response and low ripple. As described above, the miniaturization of the inverter portion of the X-ray power supply is steadily proceeding, but the oil tank including the high-voltage transformer and the high-voltage rectifier circuit, that is, the DC high-voltage generator is relatively small. Is late. The reason for this is that the high voltage rectification method of the conventional DC high voltage generator is a neutral-point grounded bridge rectification circuit shown in FIG. In FIG.
Is a high-voltage transformer having two secondary windings 52 and 53 having a neutral point grounded, and 54, 55, 56 and 57 are bridge-connected high-voltage diodes. In this method, since both poles of all the high-voltage diodes 54 to 57 are at a high potential, a high insulating material is required for wiring and mounting of the high-voltage diodes, and the high-voltage transformer 51 has two high-voltage diodes. Since the windings 52 and 53 are required and electrical insulation between the windings is required, it is difficult to reduce the size of the DC high-voltage generator by increasing the size of the high-voltage transformer. In addition, the high-voltage part and the low-voltage part have a complicated structure, so the distance between the high-voltage part and the low-voltage part must be increased to ensure electrical insulation between them. This, too, was one of the reasons why the DC high-voltage generator could not be reduced in size and weight.

SUMMARY OF THE INVENTION An object of the present invention is to realize a compact and lightweight X-ray apparatus by reducing the size and weight of a DC high voltage generator for X-rays.

Therefore, according to the present invention, a high-voltage transformer having one secondary winding and an AC high voltage from the secondary winding are provided in an oil tank comprising a case body and an upper lid. Two high voltage sockets, a positive electrode and a negative electrode, are juxtaposed on the upper lid in a DC high voltage generator that encloses a DC high voltage generating circuit for boosting and rectifying, a transformer for filament, and a divider for high voltage detection with insulating oil. Along with these high voltage sockets,
The high-voltage transformer is mounted with its secondary winding downward, and a circuit board on which two sets of positive and negative voltage doubler rectifier circuits forming a DC high-voltage generating circuit are mounted is mounted on the high-voltage transformer. Below the socket, the positive and negative poles of the high-voltage socket and the positive and negative poles of the above two sets of voltage doubler rectifiers are arranged so as to correspond to each other and fixed substantially parallel to the upper lid.
Also, the positive and negative high voltage outputs of the two sets of positive and negative voltage doubler rectifier circuits are connected to the positive and negative high voltage sockets, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention mainly resides in the arrangement and configuration of members constituting a DC high voltage generator. In order to facilitate understanding of the present invention, the circuit configuration of the embodiment of the present invention shown in FIG. First, an example will be described. In the figure, reference numeral 1 denotes a grounded metal oil tank, in which a high-voltage transformer 2, a positive voltage doubler rectifying circuit 3, and a negative voltage doubler rectifying circuit 4 are provided. , A filament transformer 5, a high-voltage detection divider 26, and the like are sealed with insulating oil. 6 and 7 are high-frequency input terminals connected to the output of the high-voltage high-frequency inverter 8;
Reference numerals 9 and 10 denote a filament inverter input terminal connected to the output of the filament inverter 11; 12 denotes a positive electrode high voltage socket for inserting and connecting a high voltage cable 14 connected to the anode A of the X-ray tube 13; A negative high voltage socket is connected to the cathode K of the X-ray tube 13 and inserts and connects the high voltage cable 16. The positive voltage doubler rectifier circuit 3 includes a single voltage doubler capacitor 17, two sets of high voltage diode blocks 18 and 19 in which a plurality of diodes are connected in series to increase the withstand voltage, and a plurality of capacitors for increasing the withstand voltage. Are connected in series. Similarly, the negative voltage doubler rectifier circuit 4 includes one capacitor for voltage doubler 21, two diode blocks for high voltage 22 and 23, and a capacitor block for filter 24. In this embodiment, an X-ray tube having a single filament is used. However, in order to be applicable to an X-ray tube having two filaments, a large focus filament and a small focus filament, the negative electrode high voltage socket 1 is used.
Reference numeral 5 denotes a triode having a common terminal C, a large focal filament terminal L, and a small focal filament terminal S. Common terminal C
The negative output of the negative voltage doubler rectifier circuit 4 is connected to one end of the secondary winding 25 of the filament transformer 5, and the terminals S and L are connected to the other end of the secondary winding 25. The positive electrode high voltage socket 12 also has three poles, and all terminals are short-circuited and connected to the positive output of the positive electrode voltage doubler rectifier circuit 3.
Reference numeral 26 denotes a high-voltage detection divider in which a plurality of resistors are connected in series to increase the withstand voltage. The divider 26 is connected between the positive output of the positive electrode voltage doubler rectifier circuit 3 and the tube voltage detection terminal 27, and the tube voltage detection signal is high voltage. Control pressure circuit 28 for stabilizing output
Connected to. 29 is a terminal for detecting a high voltage output current,
That is, it is a tube current detection terminal, detects the cathode current of the high voltage diode block 22, and supplies the tube current detection signal to the tube current measurement circuit 30. This cathode current is pulse-shaped, but is equal to the tube current when averaged. The tube current may be detected by detecting the anode current of the diode block 19 for high voltage. Reference numeral 31 denotes a signal return terminal for the tube voltage detection signal and the tube current detection signal, which is connected to the inner wall of the oil tank, and in some cases, the outer wall of the tank, and is grounded. 33 is a terminal of the DC high voltage generating circuit 32 corresponding to the signal return terminal 31, 34 is a tube current detection line,
35 is a tube current detection terminal 29 by a tube current detection line 34
Shows the terminals of the DC high-voltage generating circuit 32 connected to. FIG. 2 shows an example of the structure of the high-voltage transformer 2. A primary winding N1 is wound on one leg of a mouth-shaped iron core 40 in which a UU-type or UI-type iron core is combined, and one secondary winding N is further wound thereon.
Two are wound. f is a ground start terminal of the secondary winding N2, and g is a high voltage side terminal thereof. As described above, since the winding start terminal f of the secondary winding N2 is at the ground potential, the winding N
It does not require much withstand voltage between 1 and N2.
000 V is sufficient, and it is easy to manufacture a high-voltage transformer.
In the present invention, the secondary winding voltage E of the high-voltage transformer 2 is rectified to + 2E and -2E by the two voltage doubler rectifier circuits 3 and 4, and a voltage of 4E can be applied to the X-ray tube 13. The ripples of the tube voltage applied to the anode A and the cathode K of the X-ray tube 13 are the same as the operating frequency of the high-frequency inverter 8 as shown in FIG. 3, but cancel each other because they have opposite phases. As a result, the anode of the X-ray tube,
The ripple applied to the cathode is twice the operating frequency,
In addition, there is an advantage that the size is reduced. As described above, in the present invention, only one secondary winding of the high-voltage transformer 2 is required, and the voltage doubler rectifier circuits 3 and 4 require one of the X-ray tube voltages required for the secondary winding voltage of the high-voltage transformer. / 4, so it is sufficient to be ２ of the conventional secondary winding voltage. Instead, the winding current capacity is 2
The economical effect is large, but only one secondary winding with a small number of turns is required. Further, the number of high voltage diode blocks also increases to four, but the withstand voltage may be １ ／ of the conventional one.
Although the current capacity is doubled, it is technically more difficult to increase the breakdown voltage of the high-voltage diode than to increase the current capacity, and a low breakdown voltage type is sufficient, so that the economic effect is large. In particular, in the case of X-ray equipment, the operation time is often as short as several seconds, and at the same time, the downtime is considerably longer than the operation time. It is also possible to apply. In contrast to these advantages, the present invention increases the number of the doubler capacitors 17 and 21 by two. However, as the operating frequency of the high-frequency inverter 8 increases, a capacitor having a smaller capacity can be used, and the withstand voltage becomes 1 / the tube voltage. There is no major drawback because only 4 is needed. In addition, by measuring the current flowing through the high-voltage diode block 22 on the ground side as an embodiment of the present invention, a current due to the distributed capacitance of the high-voltage transformer 2 does not flow, so that accurate current detection is possible. In the embodiment of the present invention, if the demand for the ripple voltage of the X-ray tube voltage is not severe, the capacitors 20 and 24 for the filter may be removed and only the capacitance of the high voltage cables 14 and 16 may be used. In the experiment, to output a tube voltage of 100 kV and a tube current of 100 mA, a high-frequency inverter of 20 kHz, a high-voltage transformer for generating a secondary winding voltage of about 25 kV, a capacitor for double voltage of 1000 pF and 30 kV, and a withstand voltage of 60 kV were used. With four high-voltage diode blocks and 2 m high-voltage cables each, sufficiently practical output characteristics could be obtained. The current can be detected by the anode current of the high-voltage diode block 19. 4 (A) and 4 (B) are a top view and a cross-sectional perspective view of an embodiment of the present invention in which an oil tank upper lid is removed. In the figure, the same reference numerals as in FIG. 1 correspond to the description. The tank case body 41 and the upper lid 42 filled with insulating oil are provided with a rubber packing 4 for preventing oil leakage.
3 are connected by bolts or the like (not shown). High voltage sockets 12 and 15 for positive and negative electrodes having a structure determined by JIS or the like are penetrated and welded to the upper lid 42. These high-voltage sockets 12 and 15 receive the high-voltage cables 14 and 16 from outside the oil tank, and are connected to the inside and outside of the oil tank by high-voltage fittings (not shown) near the bottom thereof. The high-voltage transformer 2 is attached to the upper lid 42 by a mounting bracket (not shown) with the secondary winding N2 facing downward at substantially the same position as the high-voltage sockets 12 and 15 along the same. Also, four rectangular insulating posts 44, 45, 46, 47 extend downward from the upper lid 42, and a circuit board 48 for high voltage, for example, a printed board is suspended substantially horizontally at the lower ends of these posts. The circuit board 48 has a first
In the figure, a high voltage rectifier circuit surrounded by a dashed line has a negative voltage doubler rectifier circuit 4 on the right side and a positive voltage doubler rectifier circuit 3 on the left side in a substantially symmetrical manner. Circuit board 48
In the above, reference numerals 17 and 21 denote capacitors for voltage doubling, reference numerals 20 and 24 denote capacitor blocks for filters, and also show the arrangement of the high voltage diode blocks 18, 19, 22, 23. As can be seen from this arrangement, the circuit board 48
Has a high potential in the left-right direction, and has a ground potential on a line located substantially in the middle between the positive voltage doubler rectifier circuit 3 and the negative voltage doubler rectifier circuit 4. Next, 49 is the ground point 33 on the circuit board 48.
The tube current detection line 34 rises from the circuit board 48 along the metal conductor 49. This metal conductor 49
Is located almost in the middle between the high voltage sockets 12 and 15 of the positive and negative electrodes, and serves as a middle point of the potential distribution between the electrodes of the socket. It has helped prevent it. Further, the metal conductor 49 can also serve as a support for the tube current detection line 34. In FIG. 4A, the high-voltage transformers 2, the positive and negative high-voltage sockets 12 and 15 are indicated by alternate long and short dash lines. In addition, 6
Reference numeral 1 denotes a printed circuit board to which a plurality of serially connected divider resistors 26A constituting the high voltage detection divider 26 are attached as shown in FIG. 5, and is attached along the longitudinal direction of the rectangular insulating columns 44 and 47. . As shown in FIG. 6, an insulating substrate 62 on which a transformer 5 for filament is mounted is mounted on the rectangular insulating posts 45 and 46 on the opposite sides.
5 and 46 are mounted along the longitudinal direction. The filament transformer 5 has a normal filament voltage of 3
Since the voltage is 10 to 10 V, a primary winding (not shown) is wound around the ring core 63 for several tens of turns, and a high-voltage insulated wire 64 is wound several turns thereon to form a secondary winding. The secondary winding is 1
For the next winding, 1/2 of the tube voltage, for example, 62.5 kV
Since the above withstand voltage is required, the wire itself has a withstand voltage. These are all arranged so that the high voltage side is located below, and the electrical insulation between the oil tank wall and the oil tank is sufficiently ensured. In FIG. 4 (A), since the drawing becomes complicated, the filament transformer 5 and the high voltage detecting divider 26 are omitted, and the terminals 6, 7, 9, 10 provided on the oil tank wall are omitted. , 27,29,31
Has a normal structure, and a description thereof will be omitted. next,
According to the present invention, the rated output is 10 kW and the rated voltage is 125 kV.
In the embodiment in which the high voltage generator for X-rays of
It was possible to put together a tank having external dimensions of (width) 250 mm, D (depth) 190 mm, and H (height) 204 mm. The dimensions of the main parts are as follows. Positive and negative sockets for high voltage (according to JIS Z4731)... Approximately 50 mm in diameter and approximately 150 mm in length. High voltage transformer (2)... W × H × D = 1
00 × 120 × 100 Filament transformer (5) ……………………………
Outer diameter 60 x thickness 30 High voltage circuit board (48) ... W x H x D =
200 × 140 × 20 (excluding height of capacitor for double voltage)

As described above, the DC high voltage generator according to the present invention has a structure in which a high voltage generating circuit is sealed with insulating oil in an oil tank composed of a tank case body and an upper lid. Two high voltage sockets of the negative electrode are mounted side by side, and along these high voltage sockets, a high voltage transformer having one secondary winding is mounted with its secondary winding down. In addition, a circuit board on which two sets of positive and negative voltage doubler rectifier circuits are mounted almost symmetrically, below the high voltage socket, their positive and negative electrodes correspond to the positive and negative electrodes of the two sets of doubler voltage rectifier circuits. The input of the two sets of voltage doubler rectifier circuits is connected to the secondary winding of the high voltage transformer, and their positive and negative high voltage outputs are respectively connected to the positive and negative electrodes. Socket for each high voltage Is a circuit and structure connected. According to the present invention, such a circuit and structure allows the height of the tank to be equal to the length of the high voltage socket, the thickness of the circuit board on which the high voltage rectifier circuit is mounted, and the height sufficient to provide the necessary insulation distance. Since it can be manufactured in dimensions and the size of the DC high voltage generator can be reduced, the size of the X-ray apparatus itself can be reduced.
Further, since the amount of insulating oil in the oil tank is also reduced, the cost can be reduced and the weight can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing an example of the structure of a high-voltage transformer used in one embodiment of the present invention.

FIG. 3 is a diagram for explaining ripple of a high voltage output in one embodiment of the present invention.

FIG. 4A is a top view of the embodiment of the present invention with an oil tank upper lid removed, and FIG. 4B is a cross-sectional perspective view of the oil tank.

FIG. 5 is an explanatory diagram of a high voltage detection divider used in one embodiment of the present invention.

FIG. 6 is an explanatory diagram of a filament transformer used in one embodiment of the present invention.

FIG. 7 is a diagram showing an example of a conventional high voltage rectification method for X-rays.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC high voltage generator 2 ... High voltage transformer 3, 4 ... Double voltage rectification circuit 5 ... Filament transformer 8 ... High frequency inverter 12, 15 ... High voltage socket 13 ... X-ray tubes 14, 16 ... High voltage cable 17, 21 ... Double voltage capacitor 18, 23 ... High voltage diode block 19, 22 ... High voltage diode block 26 ..Divider for high-voltage detection 28... Control circuit 30... Tube current detection circuit 32... High-voltage generation circuit 41... Tank body 42... Top cover 44, 45, 46, 47. Square insulating support 48 48 High-voltage circuit board 49 Metal ground 61 61 Printed circuit board for high-voltage detection divider 26 62 Transformer for filament Insulating substrate for

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02M 3/28 H02J 1/00 308 H02M 7/10 H05G 1/06 H05G 1/12

Claims (4)

(57) [Claims] 1. A high-voltage transformer having one secondary winding in an oil tank comprising a case body and an upper lid, and a DC high-voltage generating circuit for boosting and rectifying an AC high voltage from the secondary winding. In a DC high-voltage generator in which is sealed with insulating oil, two high-voltage sockets, a positive electrode and a negative electrode, are mounted side by side on the upper lid, and the high-voltage transformer is mounted along these high-voltage sockets. The secondary winding is mounted downward, and the positive and negative electrodes that form the DC high voltage generation circuit
The circuit board on which the set of voltage doubler rectifier circuits is mounted is placed below the high voltage socket, and the positive electrode of the high voltage socket,
The negative electrode and the positive and negative electrodes of the two sets of voltage doubler rectifiers are arranged so as to correspond to each other and fixed substantially parallel to the upper cover. A DC high-voltage generator, wherein a high-voltage output is connected to each of the positive and negative high-voltage sockets. 2. A high voltage transformer having one secondary winding in an oil tank comprising a case body and an upper lid, and a DC high voltage generating circuit for boosting and rectifying an AC high voltage from the secondary winding. In a DC high-voltage generator in which is sealed with insulating oil, two high-voltage sockets, a positive electrode and a negative electrode, are mounted side by side on the upper lid, and the high-voltage transformer is mounted along these high-voltage sockets. The secondary winding is mounted on the upper lid with the lower side facing downward, and a circuit board on which two sets of positive and negative voltage doubler rectifier circuits forming a DC high voltage generating circuit are mounted is mounted below the high voltage socket. The positive and negative poles of the high-voltage socket and the positive and negative poles of the two sets of voltage doubler rectifiers are arranged so as to correspond to each other and fixed substantially in parallel with the upper lid. Almost in the middle of the circuit A grounding conductor for connecting them between the grounding point to be connected and the upper lid, and connecting the positive and negative high-voltage outputs of the voltage doubler rectifier circuit to the positive and negative high-voltage sockets, respectively. A DC high voltage generator. 3. A high voltage transformer having one secondary winding in an oil tank comprising a case body and an upper lid, and a DC high voltage generating circuit for boosting and rectifying an AC high voltage from the secondary winding. In a DC high-voltage generator in which the high-voltage socket is filled with insulating oil, two high-voltage sockets, a positive electrode and a negative electrode, are mounted side by side on the upper lid, and the high-voltage socket is placed at a position substantially equal to both high-voltage sockets. A voltage transformer is mounted on the upper lid with its secondary winding downward, and a circuit board on which two sets of positive and negative voltage doubler rectifier circuits forming a DC high voltage generating circuit are mounted almost symmetrically is provided.
Below the high voltage socket, the positive electrode and the negative electrode of the high voltage socket and the positive electrode and the negative electrode of the two sets of voltage doubler rectifiers are arranged so as to correspond to each other and fixed substantially parallel to the upper lid. A grounding conductor is provided between a grounding point located approximately at the center of the two sets of voltage doubler rectifier circuits of the negative electrode and the upper cover, and a grounding conductor is provided along the grounding conductor from the tube current detection line on the circuit board. The current detection line is extended and connected to the tube current detection circuit provided outside the oil tank through the upper lid, and the positive and negative high voltage outputs of the voltage doubler rectifier circuit are respectively connected to the positive and negative electrodes. A DC high voltage generator connected to each high voltage socket. 4. A high voltage cable connected to an X-ray tube located outside the oil tank is inserted and connected to each of the positive and negative high voltage sockets. The X-ray apparatus according to claim 3.