JP7466502B2 - measuring device - Google Patents

Description

This disclosure relates to a measuring device.

A capacitance measuring device is known that has a low-voltage side circuit, a high-voltage side circuit, and a coaxial cable for connecting them. In such a device, the low-voltage side circuit and the high-voltage side circuit are connected via a block capacitor to prevent high voltage from being applied to the low-voltage side circuit.

For example, in Patent Document 1 (JP 2017-90266 A), the impedance analyzer and the test fixture are connected via a capacitor and a coil.

JP 2017-90266 A

A coaxial cable is composed of a core wire from the center of the axis, an insulator covering the core wire, a conductive shield wire covering the insulator, and a coating made of an insulator covering the shield wire. The shield wire is connected to GND. When a high voltage is applied to a coaxial cable, insulation breakdown occurs between the core wire and the shield wire. As a result, a short-circuit current flows into GND, destroying the measuring device.

A block capacitor is connected between the shield wire and GND to prevent insulation breakdown between the core wire and the shield wire.

If it becomes necessary to change the type of block capacitor depending on the measurement conditions or measurement environment, the installed block capacitor must be replaced with a different one.

Therefore, the object of the present disclosure is to provide a measuring device that can facilitate the task of replacing block capacitors.

The measuring device of the present disclosure includes a low-voltage side circuit, a high-voltage side circuit, a first coaxial cable connected to the low-voltage side circuit, a second coaxial cable connected to the high-voltage side circuit, a first block capacitor, a second block capacitor, and a housing for accommodating the first block capacitor. Each of the first coaxial cable and the second coaxial cable has a core wire and a shield wire. The core wire of the first coaxial cable and the core wire of the second coaxial cable are connected via the first block capacitor. The shield wire of the first coaxial cable and the shield wire of the second coaxial cable are connected via the second block capacitor.

The measuring device disclosed herein makes it easy to replace block capacitors.

FIG. 2 is a diagram showing an equivalent circuit of the measurement device according to the first embodiment. 2 is a cross-sectional view of a first coaxial cable 21. FIG. 2 is a cross-sectional view of a second coaxial cable 22. FIG. 2 is an external view of a connection portion between a low-voltage side circuit 100 and a high-voltage side circuit 200 in the first embodiment. FIG. 2 is a diagram showing wiring at a connection portion between a low-voltage side circuit 100 and a high-voltage side circuit 200 in the first embodiment. FIG. FIG. 13 is a diagram showing an equivalent circuit of a measuring device according to a second embodiment. FIG. 11 is an external view of a connection portion between a low-voltage side circuit 100 and a high-voltage side circuit 200 in a second embodiment. 11 is a diagram showing wiring at a connection portion between a low-voltage side circuit 100 and a high-voltage side circuit 200 in the second embodiment. FIG. FIG. 11 is an external view of a connection portion between a low-voltage side circuit 100 and a high-voltage side circuit 200 in the third embodiment.

Embodiment 1.
FIG. 1 is a diagram showing an equivalent circuit of the measurement device according to the first embodiment.

The measuring device includes a low-voltage side circuit 100, a high-voltage side circuit 200, first coaxial cables 21a, 21b, 21c, and 21d connected to the low-voltage side circuit 100, second coaxial cables 22a and 22b connected to the high-voltage side circuit 200, first block capacitors 31a, 31b, 31c, and 31d, and second block capacitors 32a, 32b, 32c, and 32d.

The low-voltage side circuit 100 includes, for example, an LCR meter 10.

The LCR meter 10 has a high-side current application terminal (HC) 11, a high-side voltage application terminal (HP) 12, a low-side voltage application terminal (LP) 13, and a low-side voltage application terminal (LC) 14.

The high side current application terminal (HC) 11 is connected to the first coaxial cable 21a. The high side voltage application terminal (HP) 12 is connected to the first coaxial cable 21b. The low side voltage application terminal (LP) 13 is connected to the first coaxial cable 21c. The low side voltage application terminal (LC) 14 is connected to the first coaxial cable 21d.

The high-voltage side circuit 200 has, for example, a test fixture 52 that measures the capacitance of a semiconductor device 51.

The semiconductor device 51 to be measured is an IGBT (Insulated Gate Bipolar Transistor). The semiconductor device 51 has a collector terminal C, an emitter terminal E, and a gate terminal G.

The test fixture 52 is provided to measure the capacitances of the gate-collector parasitic capacitance C _GC , the gate-emitter parasitic capacitance C _GE , and the collector-emitter parasitic capacitance C _CE of the semiconductor device 51 .

The test fixture 52 includes a power supply Vcc, inductances 41 and 42, and a bypass capacitor C _BP . The power supply Vcc is connected to a first end of the inductance 41. The second end of the inductance 41 is connected to a collector terminal C of the semiconductor device 51. The first end of the inductance 42 is connected to a gate terminal G of the semiconductor device 51. The second end of the inductance 42 is connected to an emitter terminal E of the semiconductor device 51. The first end of the bypass capacitor C _BP is connected to the collector terminal C of the semiconductor device 51. The second end of the bypass capacitor C _BP is connected to the emitter terminal E of the semiconductor device 51. The emitter terminal E of the semiconductor device 51 is connected to ground GND. The gate terminal G of the semiconductor device 51 is connected to the second coaxial cable 22a. The emitter terminal E of the semiconductor device 51 is connected to the second coaxial cable 22b.

The first coaxial cable 21a is connected to the second coaxial cable 22a via the first block capacitor 31a. The first coaxial cable 21b is connected to the second coaxial cable 22a via the first block capacitor 31b. The first coaxial cable 21c is connected to the second coaxial cable 22b via the first block capacitor 31c. The first coaxial cable 21d is connected to the second coaxial cable 22b via the first block capacitor 31d.

The first coaxial cable 21a is connected to the second coaxial cable 22a via the second block capacitor 32a. The first coaxial cable 21b is connected to the second coaxial cable 22a via the second block capacitor 32b. The first coaxial cable 21c is connected to the second coaxial cable 22b via the second block capacitor 32c. The first coaxial cable 21d is connected to the second coaxial cable 22b via the second block capacitor 32d.

In the following, the first coaxial cables 21a, 21b, 21c, and 21d are collectively referred to as the first coaxial cable 21. The second coaxial cables 22a and 22b are collectively referred to as the second coaxial cable 22. The first block capacitors 31a, 31b, 31c, and 31d are collectively referred to as the first block capacitor 31. The second block capacitors 32a, 32b, 32c, and 32d are collectively referred to as the second block capacitor 32.

Figure 2 is a cross-sectional view of the first coaxial cable 21.

The first coaxial cable 21 is composed of a core wire 1, an insulator 2 covering the core wire 1, a shield wire 3 covering the insulator 2, and a coating 4 covering the shield wire 3. The shield wire 3 is connected to ground GND to prevent the coating 4 from becoming charged and generating stray capacitance with the outside.

Figure 3 is a cross-sectional view of the second coaxial cable 22.

The second coaxial cable 22 is composed of a core wire 101, an insulator 102 covering the core wire 101, a shield wire 103 covering the insulator 102, and a coating 104 covering the shield wire 103. The shield wire 103 is connected to ground GND via a second block capacitor 32 to prevent the coating 104 from becoming charged and generating stray capacitance with the outside.

The core wire 1 of the first coaxial cable 21 and the core wire 101 of the second coaxial cable 22 are connected via a first block capacitor 31. The shield wire 3 of the first coaxial cable 21 and the shield wire 103 of the second coaxial cable 22 are connected via a second block capacitor 32.

Figure 4 is an external view of the connection between the low-voltage side circuit 100 and the high-voltage side circuit 200 in the first embodiment. Figure 5 is a diagram showing the wiring of the connection between the low-voltage side circuit 100 and the high-voltage side circuit 200 in the first embodiment.

The measuring device has a housing 50 for housing the first block capacitor 31.

The second block capacitor 32 is positioned outside the housing 50.

Holes 70 and 71 are formed on the top surface of the housing 50.

A first BNC (Bayonet Neill Concelman) connector 60 and a second BNC connector 62 are inserted into the housing 50.

The first coaxial cable 21 is coupled to the first BNC connector 60. The first BNC connector 60 includes, from the center, a core wire 201, an insulator 202 covering the core wire 201, and a shield wire 203 covering the insulator 202. The core wire 201 is coupled to the core wire 1 of the first coaxial cable 21. The insulator 202 is coupled to the insulator 2 of the first coaxial cable 21. The shield wire 203 is coupled to the shield wire 3 of the coaxial cable 21.

The second coaxial cable 22 is coupled to the second BNC connector 62. The second BNC connector 62 includes, from the center, a core wire 301, an insulator 302 covering the core wire 301, and a shield wire 303 covering the insulator 302. The core wire 301 is coupled to the core wire 101 of the second coaxial cable 22. The insulator 302 is coupled to the insulator 102 of the second coaxial cable 22. The shield wire 303 is coupled to the shield wire 103 of the second coaxial cable 22.

The measuring device includes a printed circuit board 80. The printed circuit board 80 is provided inside the housing 50.

The printed circuit board 80 has a first connection terminal 90 and a second connection terminal 91. The first end of the second block capacitor 32 is connected to the first connection terminal 90. The second end of the second block capacitor 32 is connected to the second connection terminal 91. The wiring connecting the first end of the second block capacitor 32 to the first connection terminal 90 passes through the hole 70. The wiring connecting the second end of the second block capacitor 32 to the second connection terminal 91 passes through the hole 71. The shielded wire 203 of the first BNC connector 60 is connected to the first connection terminal 90. The shielded wire 303 of the second BNC connector 62 is connected to the second connection terminal 91. Therefore, the shielded wire 203 of the first BNC connector 60 and the shielded wire 303 of the second BNC connector 62 are connected via the second block capacitor 32. The shield wire 203 of the first BNC connector 60 is connected to ground GND.

The core wire 201 of the first BNC connector 60 and the core wire 301 of the second BNC connector 62 are connected via the first block capacitor 31.

In this embodiment, even if insulation breakdown occurs between the core wire 101 and the shield wire 103 of the second coaxial cable 22 on the high voltage side, the shield wire 303 of the second BNC connector 62 is connected to ground GND via the block capacitor 32, so that it is possible to prevent a short circuit current from flowing into the LCR meter 10.

In addition, since the second block capacitor 32 is placed outside the housing 50, the second block capacitor 32 can be easily replaced, making it easy to change the type of second block capacitor 32 depending on the measurement conditions or measurement environment.

The number of holes formed in the housing 50 does not need to be limited to two, and it is also possible to form one large hole in the housing 50 that can connect the second block capacitor 32 to the connection terminals 90 and 91.

The printed circuit board 80 may be disposed on the surface of the housing 50 rather than inside the housing 50.

The connections between the printed circuit board 80 and the first connection terminal 90 and the second connection terminal 91, the first connection terminal 90 and the shielded wire 203, and the second connection terminal 91 and the shielded wire 303 may be made by soldering or press-fitting, etc.

Embodiment 2.
FIG. 6 is a diagram showing an equivalent circuit of the measurement device according to the second embodiment.

The measurement device of the second embodiment differs from the measurement device of the first embodiment in that the measurement device of the second embodiment includes coils 43a to 43d.

The first coaxial cable 21a is connected to the second coaxial cable 22a via the second block capacitor 32a and coil 43a connected in series. The first coaxial cable 21b is connected to the second coaxial cable 22a via the second block capacitor 32b and coil 43b connected in series. The first coaxial cable 21c is connected to the second coaxial cable 22b via the second block capacitor 32c and coil 43c connected in series. The first coaxial cable 21d is connected to the second coaxial cable 22b via the second block capacitor 32d and coil 43d connected in series.

In the following, coils 43a, 43b, 43c, and 43d will be collectively referred to as coil 43.

Figure 7 is an external view of the connection between the low-voltage side circuit 100 and the high-voltage side circuit 200 in embodiment 2. Figure 8 is a diagram showing the wiring of the connection between the low-voltage side circuit 100 and the high-voltage side circuit 200 in embodiment 2.

Holes 72, 73, 74, and 75 are formed on the top surface of the housing 50.

As in embodiment 1, the first BNC connector 60 and the second BNC connector 62 are inserted into the housing 50.

In this embodiment, the coupling between the first coaxial cable 21 and the first BNC connector 60, the connection between the first BNC connector 60 and the first block capacitor 31, the coupling between the second coaxial cable 22 and the second BNC connector 62, and the connection between the second BNC connector 62 and the second block capacitor 32 are the same as in the first embodiment. In this embodiment, as in the first embodiment, the shield wire 203 of the first BNC connector 60 is connected to ground GND.

In this embodiment, as in embodiment 1, a printed circuit board 80 is provided inside the housing 50.

The printed circuit board 80 has a first connection terminal 92, a second connection terminal 93, a third connection terminal 94, and a fourth connection terminal 95.

The first end of the second block capacitor 32 is connected to the first connection terminal 92. The second end of the second block capacitor 32 is connected to the second connection terminal 93. The wiring connecting the first end of the second block capacitor 32 to the first connection terminal 92 passes through the hole 72. The wiring connecting the second end of the second block capacitor 32 to the second connection terminal 93 passes through the hole 73.

The first end of the coil 43 is connected to the third connection terminal 94. The second end of the coil 43 is connected to the fourth connection terminal 95. The wiring connecting the first end of the coil 43 to the third connection terminal 94 passes through the hole 74. The wiring connecting the second end of the coil 43 to the fourth connection terminal 95 passes through the hole 75.

The shielded wire 203 of the first BNC connector 60 is connected to the first connection terminal 92. The shielded wire 303 of the second BNC connector 62 is connected to the fourth connection terminal 95. The second connection terminal 93 and the third connection terminal 94 are connected by wiring within the printed circuit board 80.

Therefore, the shielded wire 203 of the first BNC connector 60 and the shielded wire 303 of the second BNC connector 62 are connected via the second block capacitor 32 and coil 43 connected in series. The shielded wire 203 of the first BNC connector 60 is connected to ground GND.

In this embodiment, as in embodiment 1, even if insulation breakdown occurs between the core wire 101 and the shield wire 103 of the second coaxial cable 22 on the high voltage side, the shield wire 303 of the second BNC connector 62 is connected to ground GND via the block capacitor 32, so that it is possible to prevent a short circuit current from flowing into the LCR meter 10.

In this embodiment, the second block capacitor 32 and the coil 43 form a circuit that resonates at a specific frequency. Due to the resonance, the impedance between the shield wire 203 on the first BNC connector 60 side and the shield wire 303 on the second BNC connector 62 becomes 0Ω. By making the coil 43 larger, the voltage applied between the core wire 101 and the shield wire 103 of the second coaxial cable can be reduced to a voltage that does not cause insulation breakdown.

In addition, since the second block capacitor 32 and the coil 43 are placed outside the housing 50, the second block capacitor 32 and the coil 43 can be easily replaced depending on the measurement conditions or measurement environment.

The number of holes formed in the housing 50 does not need to be limited to four, and it is also possible to form one large hole in the housing 50 that can connect the second block capacitor 32 to the first connection terminal 92 and the second connection terminal 93, and connect the coil 43 to the third connection terminal 94 and the fourth connection terminal 95.

The printed circuit board 80 may be disposed on the surface of the housing 50 rather than inside the housing 50.

The connections between the printed circuit board 80 and the first connection terminal 92, the second connection terminal 93, the third connection terminal 94, and the fourth connection terminal 95, the connections between the first connection terminal 90 and the shielded wire 203, and the connections between the fourth connection terminal 95 and the shielded wire 303 may be made by soldering or press-fitting, etc.

Embodiment 3.
FIG. 9 is an external view of a connection portion between low-voltage side circuit 100 and high-voltage side circuit 200 in the third embodiment.

The housing 50 has an openable top cover 98 to cover the top surface 99 in which the holes 72 to 74 are formed.

When the top lid 98 is closed, the second block capacitor 32 and the coil 43 are positioned between the top lid 98 and the top surface 99 in which the holes 72 to 74 are formed.

The second block capacitor 32 and coil 43 can be easily replaced by opening the top cover 98.

When using the measuring device, the top cover 98 is closed. The block capacitor 32 and coil 43 are built into the housing 50, which improves the insulation performance between the terminals.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

1,101,201,301 Core wire, 2,102,202,302 Insulator, 3,103,203,303 Shield wire, 4,104 Coating, 10 LCR meter, 21a,21b,21c,21d First coaxial cable, 22a,22b Second coaxial cable, 31a,31b,31c,31d First block capacitor, 32a,32b,32c,32d Second block capacitor, 41,42 Inductance, 43a,43b,43c,43d Coil, 50 Housing, 51 Semiconductor device, 52 Test fixture, 60 First connector, 62 Second connector, 70,71,72,73,74,75 Hole, 80 Printed circuit board, 90,92 First connection terminal, 91,93 Second connection terminal, 94 third connection terminal, 95 fourth connection terminal, 98 upper cover, 99 upper surface, 100 low voltage side circuit, 200 high voltage side circuit, C _GC gate-collector parasitic capacitance, C _GE gate-emitter parasitic capacitance, C _CE collector-emitter parasitic capacitance, C _BP bypass capacitor.

Claims (6)

A low voltage side circuit;
A high voltage side circuit;
a first coaxial cable connected to the low-voltage side circuit;
a second coaxial cable connected to the high-voltage side circuit;
A first capacitor block;
a second capacitor block;
a housing for housing the first capacitor block;
each of the first coaxial cable and the second coaxial cable has a core wire and a shield wire;
a core wire of the first coaxial cable and a core wire of the second coaxial cable are connected via the first block capacitor,
A measurement device, wherein the shield wire of the first coaxial cable and the shield wire of the second coaxial cable are connected via the second block capacitor. a first BNC connector having a core wire and a shield wire;
a second BNC connector having a core wire and a shield wire;
a core wire of the first coaxial cable and a core wire of the first BNC connector are coupled together, and a shield wire of the first coaxial cable and a shield wire of the first BNC connector are coupled together,
each of the first BNC connector and the second BNC connector is plugged into the housing;
a core wire of the first BNC connector and a core wire of the second BNC connector are connected via the first block capacitor;
2. The measuring device according to claim 1, wherein the shielded wire of the first BNC connector and the shielded wire of the second BNC connector are connected via the second block capacitor. a printed circuit board having a first connection terminal and a second connection terminal;
At least one hole is formed in the surface of the housing,
the second capacitor block is disposed outside the housing;
the first connection terminal is connected to a shielded wire of the first BNC connector, and the second connection terminal is connected to a shielded wire of the second BNC connector;
The measuring device of claim 2 , wherein a wiring connecting a first end of the second block capacitor and the first connection terminal, and a wiring connecting a second end of the second block capacitor and the second connection terminal, pass through the at least one hole. The measurement device according to claim 2, wherein the shielded wire of the first BNC connector and the shielded wire of the second BNC connector are connected via the second block capacitor and a coil connected in series. a printed circuit board having a first connection terminal, a second connection terminal, a third connection terminal, and a fourth connection terminal;
At least one hole is formed in the surface of the housing,
the second block capacitor and the coil are disposed outside the housing;
the first connection terminal is connected to a shielded wire of the first BNC connector, the fourth connection terminal is connected to a shielded wire of the second BNC connector, and the second connection terminal and the third connection terminal are connected by wiring within the printed circuit board;
The measuring device of claim 4, wherein a wiring connecting a first end of the second block capacitor and the first connection terminal, a wiring connecting a second end of the second block capacitor and the second connection terminal, a wiring connecting a first end of the coil and the third connection terminal, and a wiring connecting a second end of the coil and the fourth connection terminal pass through the at least one hole. the housing has an openable and closable top cover for covering a surface on which the at least one hole is formed;
The measuring device according to claim 5 , wherein the second block capacitor and the coil are disposed between the top lid and the surface when the top lid is closed.

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