Device for adjusting stray capacitance of voltage-dividing circuit

Abstract

To provide a device for adjusting the stray capacitance of a voltage-dividing circuit with which it is possible to accurately divide a high-voltage pulse.SOLUTION: The stray capacitance adjustment device comprises a voltage-dividing circuit 30, a cover 42, a first conductor 38, and a second conductor 40. The voltage-dividing circuit 30 is connected between a ground potential line fixed to ground potential and a high-voltage line. The voltage-dividing circuit 30 includes a voltage-dividing resistor 33 and a first voltage-dividing capacitor 34. The cover 42 has conductive properties and covers the voltage-dividing circuit 30. The first conductor 38 is located between a section of the cover 42 and the first voltage-dividing capacitor 34. The first conductor 38 covers the first voltage-dividing capacitor 34 and is fixed to ground potential. The second conductor 40 is electrically connected to the high-voltage line. The second conductor 40 is located closer to the first voltage-dividing capacitor 34 than the first conductor 38. The angle of the second conductor 40 as seen from the first voltage-dividing capacitor 34 is variable.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a floating capacitance adjustment device for a voltage dividing circuit.

Background Art

[0002] Patent Document 1 describes a variable capacitance substrate and a substrate parasitic capacitance adjustment method. The variable capacitance substrate includes a dielectric layer formed between a wiring conductor and a ground layer. By generating a depletion layer in the dielectric layer, the dielectric constant changes, and the parasitic capacitance parasitic on the wiring conductor is adjusted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a voltage dividing circuit that divides a high voltage pulse, in order to make the voltage dividing waveform a similar waveform without distortion, it is necessary to provide a voltage dividing capacitor in parallel with the voltage dividing resistor and adjust the voltage ratio of the voltage dividing capacitor to be equal to the voltage dividing ratio of the resistor. The voltage dividing capacitor is affected by the surrounding stray capacitance. In many cases, such adjustment is performed with the conductive cover covering the voltage dividing circuit removed, with access to the voltage dividing circuit and in a state where the stray capacitance is small. Then, after the adjustment, the cover covering the voltage dividing circuit is attached, so that the voltage dividing circuit is completely housed. In this state, however, the stray capacitance increases, and the adjusted capacitance may be disrupted. Since the capacitance of the voltage dividing capacitor changes after adjustment, it becomes difficult to divide the high voltage pulse waveform with little distortion.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a floating capacitance adjustment device for a voltage dividing circuit capable of accurately dividing a high voltage pulse.

Means for Solving the Problem

[0006] [1] To solve the above-described problems, a floating capacitance adjustment device for a voltage dividing circuit according to the present invention includes a voltage dividing circuit, a cover, a first conductor, and a second conductor. The voltage dividing circuit is connected between a ground potential line defined at a ground potential and a high voltage line. The voltage dividing circuit has a voltage dividing resistor and a voltage dividing capacitor. The cover has conductivity and covers the voltage dividing circuit. The first conductor is disposed between a part of the cover and the voltage dividing capacitor. The first conductor covers the voltage dividing capacitor and is defined at the ground potential. The second conductor is electrically connected to the high voltage line. The second conductor is disposed closer to the voltage dividing capacitor than the first conductor. The angle of the second conductor as viewed from the voltage dividing capacitor is variable.

[0007] In the above floating capacitance adjustment device, the first conductor is defined at the ground potential and covers the voltage dividing capacitor. Thereby, an air capacitor is formed between the first conductor and the voltage dividing capacitor, and a floating capacitance is generated. Further, since the first conductor is located between a part of the cover and the voltage dividing capacitor, it prevents an air capacitor from being formed between a part of the cover and the voltage dividing capacitor. Therefore, the change in the characteristics of the voltage dividing capacitor before and after the cover is attached is reduced. That is, according to the above floating capacitance adjustment device, the capacitance value of the voltage dividing capacitor is adjusted in a state where the cover is removed, and even when the cover is attached thereafter, the change in the capacitance value of the voltage dividing capacitor is reduced, and a high voltage pulse can be accurately divided.

[0008] In addition, in the above-described floating capacitance adjustment device, a second conductor electrically connected to the high-voltage line is disposed closer to the voltage-dividing capacitor than the first conductor. As a result, the floating capacitance in the voltage-dividing capacitor is affected by the second conductor. And since the angle of the second conductor as viewed from the voltage-dividing capacitor is variable, the magnitude of the floating capacitance generated between the voltage-dividing capacitor and the second conductor can be made variable. Therefore, by using the angle of the second conductor, the capacitance value of the voltage-dividing capacitor can be adjusted more accurately, and the high-voltage pulse can be divided more accurately.

[0009] [2] In the floating capacitance adjustment device of [1] above, the second conductor may include a non-conductive plate material. By attaching a conductor such as a copper plate to the non-conductive plate material, it becomes possible to increase the capacitance change.

[0010] [3] The floating capacitance adjustment device of [1] or [2] above may further include a shaft that supports the second conductor, and the second conductor may be rotatable about the shaft. In this case, a configuration for making the angle of the second conductor variable can be easily realized.

[0011] [4] In the floating capacitance adjustment device of [3] above, the shaft may have conductivity, and the second conductor may be electrically connected to the high-voltage line via the shaft. In this case, since there is no need to prepare another component for electrically connecting the second conductor and the high-voltage line, the number of components can be reduced and the configuration can be simplified.

[0012] [5] In the floating capacitance adjustment device of [4] above, the voltage-dividing capacitor includes a plurality of capacitors connected in series with each other, and the distance between the capacitor closest to the high-voltage line side among the plurality of capacitors and the shaft may be shorter than the distance between the shaft and the other capacitors among the plurality of capacitors. In this case, the high-voltage line disposed between the shaft and the voltage-dividing capacitor can be shortened, and the safety of the device can be improved.

[0013] [6] Any of the floating capacitance adjustment devices of [1] to [5] above further includes an insulating member that covers the voltage-dividing capacitor as viewed from the one part, and the first conductor may include a conductor disposed on the surface of the member. In this case, an insulating member can be interposed between the operator who adjusts the capacitance value of the voltage-dividing capacitor and the voltage-dividing capacitor including the high-voltage wiring. Therefore, the safety of the operation can be improved. And by disposing a conductor as the first conductor on the surface of such a member, the first conductor can be easily disposed.

[0014] [7] In the floating capacitance adjustment device of [6] above, the member may be transparent at the wavelength of visible light. In this case, since the second conductor can be visually recognized through the member, the workability when changing the angle of the second conductor can be improved.

Advantages of the Invention

[0015] According to the floating capacitance adjustment device of the present invention, it is possible to accurately divide the high-voltage pulse.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the floating capacitance adjustment device according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are given to the same elements, and duplicate descriptions are omitted. In the following description, "connected" means electrically connected unless otherwise specified. Electrical connections include connections through conductors having a substantially zero resistance value, as well as connections through static electronic components such as resistors and capacitors. Further, the "high voltage pulse" includes not only positive voltage pulses but also negative voltage pulses.

[0018] FIG. 1 is a circuit diagram showing the configuration of a high voltage pulse generator 10 including a floating capacitance adjustment device according to an embodiment of the present invention. The high voltage pulse generator 10 includes a high voltage pulse generation unit 20, a voltage dividing circuit 30, a first conductor 38, and a second conductor 40. The high voltage pulse generator 10 is used, for example, to obtain the resistance value when a high voltage is applied to a resistor to be measured. Since excessive heat generation occurs when a high voltage is applied to the resistor, it is necessary to measure in a short time, and for this purpose, the high voltage pulses generated in the high voltage pulse generator 10 are preferably used.

[0019] The high voltage pulse generation unit 20 is a circuit portion that generates a high voltage pulse MS. The high voltage pulse generation unit 20 of the present embodiment has a connection point 21 and a connection point 22. The connection point 21 is a terminal on the high potential side (or low potential side) with respect to the ground potential, and is a terminal that outputs the high voltage pulse MS. The connection point 22 is a terminal defined as the ground potential (0V).

[0020] The voltage dividing circuit 30, the first conductor 38, and the second conductor 40 constitute a floating capacitance adjustment device. The voltage dividing circuit 30 divides the high voltage pulse MS and outputs a voltage signal VD indicating the voltage waveform of the high voltage pulse MS. The voltage dividing circuit 30 includes a high voltage line 311, a ground potential line 312, an output terminal group 32, a voltage dividing resistor 33, a first voltage dividing capacitor 34, and a second voltage dividing capacitor 35.

[0021] The high-voltage line 311 and the ground potential line 312 are pattern wirings provided on the printed wiring board. One end of the high-voltage line 311 is connected to the connection point 21 of the high-voltage pulse generation unit 20. Therefore, the high-voltage line 311 inputs the high-voltage pulse MS from the high-voltage pulse generation unit 20. One end of the ground potential line 312 is connected to the connection point 22 of the high-voltage pulse generation unit 20. Therefore, the ground potential line 312 has the ground potential of the high-voltage pulse MS.

[0022] The voltage-dividing resistor 33 is connected between the high-voltage line 311 and the ground potential line 312. The voltage-dividing resistor 33 has a plurality (two in the illustrated example) of resistors 331 and 332 connected in series with each other. One end and the other end of the series circuit composed of the resistors 331 and 332 are connected to the high-voltage line 311 and the ground potential line 312, respectively. The high-voltage pulse MS is voltage-divided according to the resistance ratio between the resistor 331 and the resistor 332, and the voltage across both ends of the resistor 332 on the ground potential line 312 side becomes the voltage signal VD that is the output of the voltage-dividing circuit 30.

[0023] The first voltage-dividing capacitor 34 is connected in parallel with the resistor 331 on the high-voltage line 311 side among the resistors 331 and 332 for the purpose of improving the capacitive balance. The second voltage-dividing capacitor 35 is connected in parallel with the resistor 332 on the ground potential line 312 side among the resistors 331 and 332 for the purpose of improving the capacitive balance. The first voltage-dividing capacitor 34 has a plurality of capacitors 341 connected in series with each other. However, the first voltage-dividing capacitor 34 may be composed of a single capacitor. The second voltage-dividing capacitor 35 has a plurality of capacitors 351 connected in parallel with each other. However, the second voltage-dividing capacitor 35 may be composed of a single capacitor. The first voltage-dividing capacitor 34 and the second voltage-dividing capacitor 35 are connected in series with each other between the high-voltage line 311 and the ground potential line 312. The node (branch point) 303 between the first voltage-dividing capacitor 34 and the second voltage-dividing capacitor 35 is connected to the node 333 between the resistor 331 and the resistor 332 of the voltage-dividing resistor 33.

[0024] The output terminal group 32 has terminals 321, 322, and 323. Terminal 321 is connected to the other end of the high-voltage line 311. Terminal 322 is connected to node 333 and node 303. Terminal 323 is connected to the other end of the ground potential line 312. A high-voltage pulse MS for applying to the resistor to be measured is output from terminals 321 and 323. A voltage signal VD for measuring the magnitude of the high-voltage pulse MS is output from terminals 322 and 323.

[0025] The first conductor 38 is connected to the ground potential line 312 via the wiring 43. Thereby, the first conductor 38 is defined at the ground potential. The second conductor 40 is electrically connected to the high-voltage line 311 via the conductive shaft 41. Thereby, the second conductor 40 is defined at the same potential as the high-voltage line 311. FIG. 2 is a perspective view showing the structure of the first voltage-dividing capacitor 34 and its vicinity. FIG. 3 is a plan view showing the structure of the first voltage-dividing capacitor 34 and its vicinity. FIG. 4 is a side cross-sectional view showing the structure of the first voltage-dividing capacitor 34 and its vicinity. As shown in FIGS. 2 to 4, the stray capacitance adjusting device further includes a wiring board 37, a member 39, and a cover 42 (shown only in FIG. 4) in addition to the first conductor 38, the second conductor 40, and the shaft 41.

[0026] The wiring board 37 is a printed wiring board and has a high-voltage line 311 and a ground potential line 312 on its surface. A plurality of capacitors 341 included in the first voltage-dividing capacitor 34 and a plurality of capacitors 351 included in the second voltage-dividing capacitor 35 are mounted on the wiring board 37 (only a plurality of capacitors 341 are shown in FIGS. 2 to 4). The capacitors 341 and 351 are, for example, lead-wire type ceramic capacitors. The plurality of capacitors 341 are arranged in a row along a certain direction.

[0027] The cover 42 is a part of a conductive housing having an internal space for accommodating the wiring board 37, the voltage dividing resistor 33, the first voltage dividing capacitor 34, and the second voltage dividing capacitor 35, and covers the wiring board 37, the voltage dividing resistor 33, the first voltage dividing capacitor 34, and the second voltage dividing capacitor 35. The cover 42 may further cover the high voltage pulse generating unit 20. The cover 42 is removed when adjusting the capacitance values of the first voltage dividing capacitor 34 and the second voltage dividing capacitor 35. The cover 42 is made of a conductive material (for example, metal) and is defined at the ground potential. In one example, the cover 42 is connected to the ground potential line 312. Only a part 421 of the cover 42 is shown in FIG. 4. The part 421 is the part of the cover 42 that is closest to the first voltage dividing capacitor 34.

[0028] The first conductor 38 is a conductor disposed between a part 421 of the cover 42 and the first voltage dividing capacitor 34. The first conductor 38 is made of a metal such as copper (Cu), for example. The first conductor 38 covers the first voltage dividing capacitor 34.

[0029] The member 39 is an insulating plate-like member supported on the wiring board 37 so as to face the surface of the wiring board 37. The member 39 is a resin plate such as an acrylic plate, for example. The member 39 may be transparent at the wavelength of visible light. Note that being transparent means that the light transmittance is 90% or more. The member 39 is disposed between a part 421 of the cover 42 and the first voltage dividing capacitor 34 and covers the first voltage dividing capacitor 34. In the illustrated example, the member 39 covers the entire first voltage dividing capacitor 34.

[0030] In one example, the first conductor 38 includes a thin film-like conductor disposed on the surface of the member 39. The thin film-like conductor may be a metal foil such as copper foil, for example. Alternatively, the first conductor 38 may be a metal plate such as a copper plate, for example. In that case, the first conductor 38 may be supported by the member 39 or may be supported on the wiring board 37 independently of the member 39.

[0031] The second conductor 40 is arranged closer to the first conductor 38 than the first conductor 38 with respect to at least one or two or more capacitors 341 on the high-voltage line 311 side among the plurality of capacitors 341 of the first voltage-dividing capacitor 34. In the illustrated example, the second conductor 40 is arranged between the first conductor 38 and the three capacitors 341 on the high-voltage line 311 side. The second conductor 40 includes, for example, a plate material extending along the wiring board 37, and in one embodiment, it consists only of the plate material. The plate material is, for example, a metal plate. The metal plate may have a plating film on its surface for corrosion prevention. Or, the second conductor 40 may include a non-conductive plate material.

[0032] The second conductor 40 is configured such that the angle of the second conductor 40 as viewed from the first voltage-dividing capacitor 34 is variable. For example, the second conductor 40 shown in FIGS. 2 to 4 is supported by a shaft 41 standing on the surface of the wiring board 37. And the second conductor 40 is rotatable about the shaft 41. The shaft 41 has conductivity, and the second conductor 40 is electrically connected to the high-voltage line 311 via the shaft 41. In one example, the shaft 41 is a metal spacer. A screw hole is formed in the end face of the shaft 41, and a screw 45 is inserted into the hole formed in the second conductor 40 and the screw 45 is screwed into the screw hole of the shaft 41, whereby the second conductor 40 is rotatably supported by the shaft 41. On the wiring board 37, the shaft 41 is attached at a position closer to the capacitor 341 closest to the high-voltage line 311. In other words, the distance between the capacitor 341 on the highest voltage line 311 side among the plurality of capacitors 341 and the shaft 41 is shorter than the distance between the shaft 41 and the other capacitors 341 among the plurality of capacitors 341.

[0033] The effects obtained by the floating capacitance adjustment device of the present embodiment having the above configuration will be described together with the problems of the conventional device. Generally, in order to accurately divide a high-voltage pulse, a voltage-dividing capacitor is provided in parallel with a voltage-dividing resistor. When providing a voltage-dividing capacitor, it is necessary to accurately adjust the capacitance value of the voltage-dividing capacitor.

[0034] FIG. 5 is a diagram for explaining problems of a conventional device. As shown in FIG. 5, the conventional device does not include the first conductor 38 and the second conductor 40 of the present embodiment. When manufacturing such a device, as shown in FIG. 5(a), with the cover 42 removed, the capacitance value of the first voltage-dividing capacitor 34 is adjusted. Then, after the adjustment is completed, as shown in FIG. 5(b), the cover 42 is attached, and the wiring board 37 and the first voltage-dividing capacitor 34 are housed in the housing.

[0035] However, when the cover 42 is added to the configuration, a stray capacitance AC1 is newly formed between a part 421 of the cover 42 and the first voltage-dividing capacitor 34. This stray capacitance AC1 did not exist when the capacitance value of the first voltage-dividing capacitor 34 was adjusted because the cover 42 was not present. Therefore, the capacitance value of the first voltage-dividing capacitor 34 will change after the adjustment. FIG. 6 is a diagram conceptually showing the change in the voltage signal VD that occurs when the cover 42 is attached. With respect to the voltage waveform (A in the figure) of the voltage signal VD adjusted with the cover 42 removed, when the cover 42 is added to the configuration, due to the influence of the stray capacitance AC1, the voltage waveform of the voltage signal VD changes as shown by B in the figure. Thus, it becomes difficult to accurately adjust the capacitance value of the first voltage-dividing capacitor 34.

[0036] In response to the above problems, in the floating capacitance adjustment device of the present embodiment, the first conductor 38 is defined at the ground potential and covers the first voltage dividing capacitor 34. As a result, an air capacitor AC2 (see FIG. 4) is formed between the first conductor 38 and the first voltage dividing capacitor 34, and a floating capacitance is generated. Further, since the first conductor 38 is located between a part 421 of the cover 42 and the first voltage dividing capacitor 34, it prevents a floating capacitance AC1 (see FIG. 5(b)) from being formed between the part 421 of the cover 42 and the first voltage dividing capacitor 34. Therefore, the change in the characteristics of the first voltage dividing capacitor 34 before and after the part 421 of the cover 42 is attached becomes small. That is, according to the floating capacitance adjustment device of the present embodiment, even when the cover 42 is removed and the capacitance value of the first voltage dividing capacitor 34 is adjusted, and then the cover 42 is attached, the capacitance value of the first voltage dividing capacitor 34 can be accurately adjusted, and the high voltage pulse can be accurately divided.

[0037] In addition, in the floating capacitance adjustment device of the present embodiment, a second conductor 40 electrically connected to the high voltage line 311 is arranged closer to the first voltage dividing capacitor 34 than the first conductor 38. As a result, the floating capacitance in the first voltage dividing capacitor 34 is affected by the second conductor 40. That is, the air capacitor AC2 between the first voltage dividing capacitor 34 and the first conductor 38 is divided into an air capacitor AC21 between the first voltage dividing capacitor 34 and the second conductor 40 and an air capacitor AC22 between the second conductor 40 and the first conductor 38. And since the angle of the second conductor 40 as seen from the first voltage dividing capacitor 34 is variable, the size of the air capacitor AC22 (floating capacitance) formed between the first voltage dividing capacitor 34 and the second conductor 40 can be made variable. Therefore, by using the angle of the second conductor 40, the capacitance value of the first voltage dividing capacitor 34 can be adjusted more accurately, and the high voltage pulse can be divided more accurately.

[0038] As in the present embodiment, the second conductor 40 may include a non-conductive plate material. By attaching a conductor such as a copper plate to the non-conductive plate material, it becomes possible to increase the capacitance change.

[0039] As in this embodiment, the floating capacitance adjustment device may include a shaft 41 that supports the second conductor 40. Then, the second conductor 40 may be rotatable about the shaft 41. In this case, a configuration in which the angle of the second conductor 40 is variable can be easily realized.

[0040] As in this embodiment, the shaft 41 may have conductivity, and the second conductor 40 may be electrically connected to the high-voltage line 311 via the shaft 41. In this case, since there is no need to prepare another component for electrically connecting the second conductor 40 and the high-voltage line 311, the number of components can be reduced and the configuration can be simplified.

[0041] As in this embodiment, the distance between the capacitor 341 closest to the high-voltage line 311 among the plurality of capacitors 341 and the shaft 41 may be shorter than the distance between the shaft 41 and the other capacitors 341 among the plurality of capacitors 341. In this case, the high-voltage line 311 disposed between the shaft 41 and the capacitor 341 can be shortened, and the safety of the device can be enhanced.

[0042] As in this embodiment, the floating capacitance adjustment device may include an insulating member 39 that covers the first voltage-dividing capacitor 34. And the first conductor 38 may include a conductor disposed on the surface of the member 39. In this case, an insulating member 39 can be interposed between the operator who adjusts the capacitance value of the first voltage-dividing capacitor 34 and the first voltage-dividing capacitor 34 including high-voltage wiring. Therefore, the safety of the operation can be enhanced. And by disposing a conductor as the first conductor 38 on the surface of such a member 39, the first conductor 38 can be easily disposed.

[0043] As in this embodiment, the member 39 may be transparent at the wavelength of visible light. In this case, since the second conductor 40 can be visually recognized through the member 39, the workability when changing the angle of the second conductor 40 can be improved.

Description of Reference Numerals

[0044] 10…High-voltage pulse generator, 20…High-voltage pulse generation section, 21, 22…Connection points, 30…Voltage division circuit, 32…Output terminal group, 33…Voltage division resistor, 34…First voltage division capacitor, 35…Second voltage division capacitor, 37…Wiring board, 38…First conductor, 39…Member, 40…Second conductor, 41…Axis, 42…Cover, 43…Wiring, 45…Screw, 303, 333…Nodes, 311…High-voltage line, 312…Ground potential line, 321, 322, 323…Terminals, 331, 332…Resistors, 341, 351…Capacitors, 421…One part, AC1…Floating capacitance, AC2, AC21, AC22…Air capacitors, MS…High-voltage pulse, VD…Voltage signal.

Claims

1. A floating capacitance adjustment device comprising a voltage dividing circuit connected between a ground potential line defined at a ground potential and a high voltage line and having a voltage dividing resistor and a voltage dividing capacitor, and a conductive cover covering the voltage dividing circuit, disposed between a part of the cover and the voltage dividing capacitor, covering the voltage dividing capacitor, and a first conductor defined at the ground potential, a second conductor electrically connected to the high voltage line and disposed closer to the voltage dividing capacitor than the first conductor, further comprising, A floating capacitance adjustment device for a voltage dividing circuit, wherein an angle of the second conductor as viewed from the voltage dividing capacitor is variable.

2. The floating capacitance adjustment device for a voltage dividing circuit according to claim 1, wherein the second conductor includes a non-conductive plate material.

3. further comprising a shaft for supporting the second conductor, The floating capacitance adjustment device for a voltage dividing circuit according to claim 1, wherein the second conductor is rotatable about the shaft.

4. The shaft has conductivity, The floating capacitance adjustment device for a voltage dividing circuit according to claim 3, wherein the second conductor is electrically connected to the high voltage line via the shaft.

5. The voltage dividing capacitor includes a plurality of capacitors connected in series with each other, The floating capacitance adjustment device for a voltage dividing circuit according to claim 4, wherein a distance between the capacitor closest to the high voltage line side among the plurality of capacitors and the shaft is shorter than a distance between the shaft and other capacitors among the plurality of capacitors.

6. further comprising an insulating member covering the voltage dividing capacitor as viewed from the one part, The floating capacitance adjustment device for a voltage dividing circuit according to any one of claims 1 to 5, wherein the first conductor includes a conductor disposed on a surface of the member.

7. The floating capacitance adjustment device for a voltage division circuit according to claim 6, wherein the member is transparent at the wavelength of visible light.

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