JPH08184626A - Disconnection detector for earth wire and electric/ electronic apparatus employing it - Google Patents

Abstract

PURPOSE: To detect disconnection of an earth wire including disconnection of earth wire within an electric/electronic apparatus and removal of the earth electrode from the earth. CONSTITUTION: An electric/electronic apparatus 1 is provided with two independent earth terminals 11, 12 and two independent earth electrodes 21, 22 are provided on the earth 2 side thus forming a closed loop CL including the two earth terminals 11, 12 and the two earth electrodes 21, 22. A decision is made that the earth wire is normal when the loop CL is closed otherwise a decision is made that the earth wire is abnormal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground wire disconnection detecting device for detecting disconnection of a ground wire between an electric / electronic device and a ground and an electric / electronic device having a ground wire disconnection detecting device.

[0002]

2. Description of the Related Art Electric and electronic equipment is grounded for circuit operation and it is not necessary to ground it for circuit operation, but it is grounded to prevent electric shock due to electric leakage. May be obligatory. In this type of electric / electronic equipment, if the ground wire is disconnected, the intended circuit operation may not be obtained, or electric shock due to electric leakage may occur.

However, to the present inventor's knowledge, no prior art sufficient to detect the disconnection of the ground wire has been known so far. For this reason, even though normal circuit operation is impaired due to the ground wire disconnection, without knowing it,
Continued use of electrical and electronic equipment sometimes resulted in unexpected results.

For example, taking a well-known line filter as an example, a capacitor for absorbing normal mode noise is connected between two lines, a common mode choke coil is inserted and connected to a line at the subsequent stage, and a line at the subsequent stage is connected. Two capacitors for absorbing common mode noise are connected between the ground terminal and the ground terminal. The common mode noise absorbing capacitor is a two-terminal capacitor, and the series connection point (middle point) is connected to the ground.

In the above power supply line filter, when the ground line for grounding the middle point of the capacitor for absorbing common mode noise is broken, the normal noise filtering function is impaired. However, since it is not possible to detect the disconnection of the ground line that grounds the midpoint of the capacitor for common mode noise absorption, it is assumed that the normal filtering function is obtained despite the disconnection of the ground line. It will be handled, and noise will propagate to the load connected to the line filter or the power supply or signal supply side.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a ground that can be grounded, including the ground wiring inside an electric / electronic device, when the ground wire between the electric / electronic device and the ground is normal. An object of the present invention is to provide a wire breakage detection device and an electric / electronic device including the ground wire breakage detection device.

Another object of the present invention is to provide a ground wire disconnection detecting device capable of detecting disconnection of a ground wire between an electric / electronic device and a ground, and an electric / electrical wire having this ground wire disconnection detecting device.
An electronic device is provided.

Still another object of the present invention is to provide a ground wire disconnection detecting device capable of detecting disconnection of ground wiring inside an electric / electronic device and an electric / electronic device having this ground wire disconnection detecting device. is there.

Still another object of the present invention is to provide a ground wire disconnection detecting device which can detect that the ground electrode on the ground side is disconnected from the ground, and an electric / electronic device having the ground wire disconnection detecting device. Is.

[0010]

In order to solve the above-mentioned problems, the ground wire disconnection detecting device according to the present invention is provided with two electric circuits.
It includes an electronic device side ground terminal, two ground side ground electrodes, and a detection circuit. The electric / electronic device side ground terminals are provided independently of each other and are connected to each other inside the electric / electronic device. The two ground-side ground electrodes are grounded independently of each other. The ground terminal and the ground electrode are connected so as to form one closed loop. The detection circuit is connected to the closed loop and determines normal when the closed loop is closed and abnormal when the closed loop is not closed.

The detection circuit of the ground wire disconnection detection device according to the present invention preferably includes at least one transformer, the secondary winding of the transformer being connected in series to the closed loop, and the primary winding of the transformer being preferably connected. A ground wire disconnection detection signal is supplied to the wire, and the ground wire disconnection detection signal is extracted as a change in the inductance of the transformer.

In another preferred example, the transformer is 2
And each primary winding is connected in series.
A secondary winding of one of the two transformers is connected in series to the closed loop. The other of the two transformers produces a signal in the secondary winding as to whether the ground condition is normal.

An electric / electronic device according to the present invention includes the ground wire disconnection detecting device according to the present invention described above.

Electricity with ground wire disconnection detection device according to the present invention
The electronic device, in one embodiment, includes a line filter circuit. The line filter circuit includes at least two capacitors. Each of the two capacitors is a four-terminal capacitor. 4 above
Each of the terminal capacitors has two terminals with each of the capacitor electrodes being independent of each other. The two terminals connected to one of the capacitor electrodes are connected in series to the line so that a circuit including one of the terminals, the capacitor electrode and the other of the terminals in series is formed. One of the two terminals connected to the other of the capacitor electrodes is connected to each other, and the other is individually connected to each of the two ground terminals.

More specifically, the line filter circuit includes a choke coil and another capacitor different from the above two capacitors. The choke coil is inserted in series with the line before the two capacitors. The other capacitor is
A four-terminal capacitor, and in a stage preceding the choke coil, two terminals connected to one of the capacitor electrodes form a circuit including one of the terminals, the capacitor electrode, and the other of the terminals in series, Connected between lines.

Electricity with ground wire disconnection detection device according to the present invention
The electronic device may have a transmission transformer at a front stage or a rear stage of the line filter circuit, and the transformer may have an inter-winding electrostatic shield body. In this case, preferably, the electrostatic shield body has two electrodes independent of each other, and the ground wire disconnection detection device includes the two electrodes provided in the electrostatic shield body in series in the closed loop. Make up the circuit.

Further, in another preferred example, the electric / electronic device with a ground wire disconnection detection device uses a voltage generated in the choke coil or the transmission transformer as the ground wire disconnection detection signal.

[0018]

In the ground wire disconnection detecting device according to the present invention, the electric / electronic equipment side ground terminals are provided independently of each other,
They are connected to each other inside the electric / electronic device, and the two ground side ground electrodes are grounded independently of each other.
Since the ground terminal and the ground electrode are connected so as to form one closed loop, when the ground wire between the electric / electronic device and the ground is normal, the electric / electronic device passes through the closed loop to Including the ground wiring inside,
Grounded.

When an abnormality such as a disconnection occurs in the ground wire between the electric / electronic equipment and the ground, the closed loop does not close.
Therefore, the detection circuit determines normal when the closed loop is closed and abnormal when the closed loop is not closed. As a result, it is possible to detect that the ground wire is normal and that the ground wire is broken, and it is possible to prevent an abnormality in circuit operation and an electric shock due to electric leakage.

Moreover, since the two ground terminals on the electric / electronic device side are provided independently of each other and are connected to each other inside the electric / electronic device, a disconnection occurs in the ground wiring inside the electric / electronic device. Closed loop does not close. Therefore, it is possible to detect the disconnection of the ground wiring inside the electric / electronic device.

Further, since the ground side is provided with the two ground electrodes which are grounded independently of each other, the closed loop does not close even when the ground electrode on the ground side is disconnected from the ground. Therefore, it is possible to detect that the ground electrode on the ground side is disconnected from the ground. If a similar closed loop is configured with only one ground terminal that should be provided on the ground side,
It cannot detect that the ground electrode on the ground side is disconnected from the ground.

Next, since the electric / electronic equipment according to the present invention has the above-mentioned ground wire disconnection detecting device, when the ground wire between the electric / electronic equipment and the ground is normal, the electric / electronic equipment is connected through the closed loop. -It is possible to reliably ground the electronic device, detect that the ground is normal and that the ground wire is broken, and prevent the abnormal operation of the circuit and the electric shock due to electric leakage.

Further specific features and advantages of the present invention include:
A more detailed description will be given with reference to the accompanying drawings.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a ground wire disconnection detecting device according to the present invention. The ground wire disconnection detection device according to the present invention detects a ground wire disconnection between the electric / electronic device 1 and the ground 2, and includes two ground terminals 11 provided on the electric / electronic device 1 side. , 12, two ground electrodes 21 and 22 provided on the ground 2 side, and the detection circuit 3. Electricity·
The electronic device side ground terminals 11 and 12 are provided independently of each other and are connected to each other inside the electric / electronic device 1. The wiring 111 indicated by a dotted line is the electric / electronic device 1
Is a ground wiring for connecting the ground terminals 11 and 12 to each other. The two ground electrodes 21 and 22 are grounded independently of each other. Ground terminal 11 and ground terminal 12
It is essential that the ground electrode 21 and the ground electrode 22 are independent of each other, but the interval may be a minute value, for example, in mm. These ground terminals 11, 12
The ground electrodes 21 and 22 are connected to form one closed loop CL.

The detection circuit 3 is connected to the closed loop CL,
It is determined that the ground wire is normal when the closed loop CL is closed, and that the ground wire is abnormal when the closed loop CL is not closed. In FIG. 1, the detection circuit 3 includes a signal supply source 31 for flowing a detection current Is and a current detection resistor 32, and determines whether or not a current flows in the closed loop CL based on the terminal voltage Es of the current detection resistor 32. , Normal or abnormal. Although not shown, a current probe that electromagnetically couples with the detection current Is may be used instead of the current detection resistor 32.

As described above, when detecting the disconnection of the ground wire between the electric / electronic device 1 and the earth 2,
Two ground terminals 11 and 12 that are independent of each other in the electronic device 1
And two ground electrodes 21 and 22 that are independently grounded on the ground side
Since one closed loop CL including 1 and 12 and two ground electrodes 21 and 22 is configured, when the ground wire between the electric / electronic device 1 and the ground 2 is normal, the closed loop CL is used. The electric / electronic device is grounded through the.

When an abnormality such as a break occurs in the ground wire between the electric / electronic device 1 and the ground 2, the closed loop CL is not closed (opened). Therefore, when the closed loop is closed, it is determined to be normal, and when the closed loop is not closed, it is determined to be abnormal, thereby confirming that the grounding is normal and that one or both of the ground wires is disconnected. It becomes possible to detect, and it becomes possible to prevent the abnormality of the circuit operation of the electric / electronic device 1 and the electric shock due to electric leakage.

Moreover, the electric / electronic device 1 is provided with two ground terminals 11 and 12 which are independent of each other to form a dual system for grounding, and the ground terminals 11 and 12 are grounded inside the electric / electronic device 1. Since they are connected to each other by 111, when the ground wiring 111 inside the electric / electronic device 1 is disconnected, the closed loop CL does not close. Therefore, the disconnection of the ground wiring 111 inside the electric / electronic device 1 can be detected.

Further, since the two ground electrodes 21 and 22 which are grounded independently of each other are provided on the ground 2 side, the ground 2
Even if either of the ground electrodes 21 or 22 on the side is disconnected from the ground 2, the closed loop CL does not close. For this reason,
When at least one of the ground electrodes 21 or 22 on the ground 2 side is disconnected from the ground 2, this can already be detected. If only one ground terminal should be provided on the ground 2 side as a common terminal and a similar closed loop CL is configured, it is detected that the ground electrode (common terminal) on the ground 2 side is disconnected from the ground. Can not do it.

The detection circuit 3 shown in the figure has a closed loop CL.
Since it is determined to be normal or abnormal depending on the presence or absence of the detection current Is flowing in the
By providing a signal supply source 31 for supplying s and a current probe (not shown) that is electromagnetically coupled to the current detection resistor 32 or the detection current Is, it can be easily determined that the closed loop CL is closed or not closed.

FIG. 2 is a view for explaining another example of the ground wire disconnection detecting device according to the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components.

The detection circuit 3 includes a transformer 33. The secondary winding 332 of the transformer 33 is inserted and connected to the closed loop CL. Then, the ground wire disconnection detection signal is supplied to the primary winding 31 of the transformer 33, and the ground wire disconnection detection signal is extracted as a change in the inductance of the transformer. The ground wire disconnection detection signal is supplied from the signal supply source 31 to the primary winding 331 of the transformer 33. Primary winding 33 of transformer 33
A current reduction resistor 34 is connected to 1. Primary winding 33
The self-inductance L1 of 1 is set so that the impedance is larger than the resistance value of the current reducing resistor 34.

According to this configuration, in the state where the closed loop CL is closed, the secondary winding 332 is short-circuited and the primary winding 3
The terminal voltage E1 of the signal 31 is significantly lowered to a low level, and most of the output voltage E of the signal supply source 31 is reduced by the current reducing resistor 34.
And the terminal voltage Es of the current reducing resistor 34 becomes high level. In the state where the ground wire is disconnected and the closed loop CL is not closed, the secondary winding 332 is opened and the terminal voltage E1 of the primary winding 331 rises according to the self-inductance L1. The terminal voltage Es of is drastically reduced to a low level. Therefore, by determining the terminal voltage Es with a constant threshold value, it is possible to easily determine whether the closed loop CL is closed or not closed.

Although not shown, the ground line 111,
Ground terminals 11, 12, ground line 211, ground line 221
The reliability can be further improved by providing a plurality of combinations of the ground electrodes 21 and 22 and further adding a closed loop.

Next, with reference to FIGS. 3 to 6, electronic / electrical equipment equipped with the ground wire disconnection detection device according to the present invention will be described. In these figures, the same reference numerals as those in FIGS. 1 and 2 denote the same components.

First, in the embodiment of FIG. 3, reference numeral 1
Reference numerals 3 and 14 are input terminals, and 15 and 16 are output terminals. The electric / electronic device 1 includes a line filter circuit 17 that absorbs noise in the power supply line. A commercial power source or a signal source is connected to the input terminals 13 and 14, and a load is connected to the output terminals 15 and 16.

The line filter circuit 17 has at least two lines.
It includes two capacitors 173 and 174. Each of the capacitors 173 and 174 is composed of a 4-terminal capacitor. The four-terminal capacitor 173 has two terminals (a1, a
2) and (b1, b2). The four-terminal capacitor 174 also has two terminals (a3, a4) and (b3, b4) whose capacitor electrodes are independent of each other.

Terminals a1 and a2 of the four-terminal capacitor 173
Are connected in series to the line 171 so that a circuit including the terminal a1, the capacitor electrode and the terminal a2 in series is formed. Terminals a3 and a4 of the four-terminal capacitor 174
Are connected in series to the line 172 so that a circuit including the terminal a3, the capacitor electrode and the terminal a4 in series is formed. Terminals b2 and 4 of the 4-terminal capacitor 173
The terminals b3 of the terminal capacitors 174 are connected to each other. The terminal b1 of the 4-terminal capacitor 173 is the ground terminal 11
The terminal b4 of the 4-terminal capacitor 174 is connected to the ground terminal 12. The lines 171 and 172 are used as power or signal transmission lines.

According to this structure, the four-terminal capacitor 17
If any of the terminals b1 and b2 of 3 or the terminals b3 and b4 of the 4-terminal capacitor 174 is disconnected, the closed loop CL
Cannot be configured. Therefore, the capacitors 173, 17
The disconnection of the terminals b1 to b4 of No. 4 can be detected, and it can be detected early that the normal noise filter operation of the line filter circuit 17 is impaired.

The line filter circuit 17 shown in FIG. 3 further includes another capacitor 175 and two choke coils 1.
76 and 177 are included. Another capacitor 175 is a four-terminal capacitor, and two terminals a5 and a6 provided on one side of the capacitor electrodes are inserted and connected to the line 171, and two terminals b provided on the other side of the capacitor electrodes.
5, b6 are inserted and connected to the line 172. Another capacitor 175 is provided in front of the choke coils 176 and 177 and has a function of absorbing normal mode noise.

As mentioned above, another capacitor 175 is
Since it is composed of a four-terminal capacitor, terminals a5, a
When a wire break occurs in any one of 6, b5, and b6, power transmission or signal transmission cannot be performed. Therefore, it is possible to avoid the problem that power transmission or signal transmission is performed even though the noise filtering operation by the other capacitor 175 included in the line filter circuit 17 is not obtained.

The choke coils 176 and 177 are called common mode choke coils, and are wound around, for example, one toroidal core, and the other capacitor 1 is used.
Line 17 between 75 and capacitors 173, 174
1, 172 are inserted and connected.

Next, in the embodiment shown in FIG.
The electronic device 1 further includes a transmission transformer 18. The transformer 18 is connected to the front stage or the rear stage of the line filter circuit 17, and has an electrostatic shield body 183 between the primary winding 181 and the secondary winding 182. In the embodiment, the transformer 18 is connected to the subsequent stage of the line filter circuit 17. The electrostatic shield 183 is generally composed of a strip-shaped thin plate, and has two electrodes c1 and c2 which are independent from each other on both end sides in the length direction. Ground wire disconnection detector 3
Are electrodes c1 and c2 provided on the electrostatic shield 183.
In series in the closed loop CL.

According to this structure, the electrostatic shield 183
Is grounded, and its disconnection can also be detected.

In the embodiment shown in FIG. 5, the line filter circuit 1
7 or the input signal or output signal of the transformer 18 is used as a ground wire disconnection detection signal. According to this configuration, it is not necessary to separately provide the signal supply source 31, and the cost is reduced.

Further, in the embodiment of FIG. 6, the detection circuit 3
Includes two transformers 33 and 35. Transformer 3
The respective primary windings 331 and 351 of 3 and 35 are connected in series. The secondary winding 332 of the transformer 33 is connected in series to the closed loop CL, and the secondary winding 3 of the transformer 35 is connected.
A signal E35 indicating whether the ground state is normal is generated at 52.

More specifically, a constant voltage diode 354, a current reducing resistor 355, and a light emitting element 356 are connected in series to the secondary winding 352. A reverse voltage protection diode 357 is connected to the light emitting element 356.
The tertiary winding 333 of the transformer 33 generates a detection signal E33 indicating that the ground state is abnormal. The tertiary winding 333 includes a constant voltage diode 334 and a current reducing resistor 33.
5 and the light emitting element 336 are connected in series. A reverse voltage protection diode 337 is connected to the light emitting element 336. The constant voltage diodes 334 and 354 give threshold values for the light emitting elements 336 and 356 to emit light.

With the closed loop CL configured,
The voltage level of the primary winding 331 of the transformer 33 becomes a low level, and almost the entire voltage of the output signal E17 output from the line filter circuit 17 becomes the primary winding 351 of the transformer 35.
Is applied to Therefore, the secondary winding 35 of the transformer 35
The high-level detection signal E35 can be obtained from 2, and the light-emitting element 356 can be turned on by this detection signal E35 to display the normal state.

When the closed loop CL is not formed, the voltage of the output signal E17 of the line filter circuit 17 is divided by the transformer 33 and another transformer 35.
Self-inductance L of the primary winding 331 of the transformer 33
33 is set to be larger than the self-inductance L35 of the primary winding 351 of the transformer 35. Therefore, the detection signal E33 of the tertiary winding 333 of the transformer 33 rises,
The detection signal E35 of the secondary winding 352 of the transformer 35 decreases. Therefore, it is possible to display the abnormal state by turning on the light emitting element 336 by the detection signal E33 and turning off the light emitting element 356 by the detection signal E35. When the self-inductance L33 of the primary winding 331 of the transformer 33 is set larger than the self-inductance L35 of the primary winding 351 of the transformer 35, the transformer 3 is opened by opening the closed loop CL.
Since the voltage between the transformer 3 and the transformer 35 rises and falls remarkably, the disconnection detection becomes easy.

The same disconnection detection can be performed by the voltage generated in the tertiary winding 353 of the transformer 35 due to the normality and abnormality of the closed loop CL. In this case, the voltage generated in the tertiary winding 353 can be transmitted to a receiving device installed at a distant position, and the disconnection detection described above can be performed by this receiving device.

[0051]

As described above, according to the present invention, the following effects can be obtained. (A) If the ground wire between the electric / electronic equipment and the ground is normal, including the ground wiring inside the electric / electronic equipment,
A ground wire disconnection detection device and electric / electronic equipment capable of grounding can be provided. (B) It is possible to provide a ground wire disconnection detection device and an electric / electronic equipment capable of detecting disconnection of a ground wire between an electric / electronic device and a ground. (C) It is possible to provide a ground wire disconnection detection device and an electric / electronic apparatus capable of detecting disconnection of the ground wiring inside the electric / electronic equipment. (D) It is possible to provide a ground wire disconnection detecting device and an electric / electronic device capable of detecting that the ground electrode on the ground side is disconnected from the ground.

[Brief description of drawings]

FIG. 1 is a diagram showing a ground wire disconnection detection device according to the present invention.

FIG. 2 is a diagram showing another example of the ground wire disconnection detection device according to the present invention.

FIG. 3 is a circuit diagram showing an embodiment of a ground wire disconnection detection device according to the present invention and an electronic / electrical device including the same.

FIG. 4 is a circuit diagram showing another embodiment of the ground wire disconnection detection device according to the present invention and an electronic / electrical device including the same.

FIG. 5 is a circuit diagram showing still another embodiment of the ground wire disconnection detection device according to the present invention and an electronic / electrical device including the same.

FIG. 6 is a circuit diagram showing still another embodiment of the ground wire disconnection detection device according to the present invention and an electronic / electrical device including the same.

[Explanation of symbols]

 1 Electric / Electronic Equipment 11, 12 Ground Terminal 17 Line Filter Circuit 171, 172 Line 173, 174 Capacitor 175 Another Capacitor 176, 177 Choke Coil 18 Transformer 183 Electrostatic Shield 2 Ground 21, 22 Ground Electrode 3 Detection Circuit 31 Signal Supply source 32 Current detection circuit CL Closed loop

Claims (8)

[Claims] 1. A ground wire disconnection detection device for detecting disconnection of a ground wire between an electric / electronic device and a ground, comprising two electric / electronic device side ground terminals and two ground side ground electrodes. A detection circuit, the electric / electronic device-side ground terminals are provided independently of each other, and are connected to each other inside the electric / electronic device, the two ground-side ground electrodes are independent of each other. Grounded, the ground terminal and the ground electrode are connected to form one closed loop, the detection circuit is connected to the closed loop, the ground wire is normal when the closed loop is closed. And a ground wire disconnection detecting device that determines that the ground wire is abnormal when the closed loop is not closed. 2. The ground wire disconnection detection device according to claim 1, wherein the detection circuit includes at least one transformer, and a secondary winding of the transformer is connected in series to the closed loop. A ground wire disconnection detecting device that supplies a ground wire disconnection detection signal to a primary winding of a transformer and extracts the ground wire disconnection detection signal as a change in the inductance of the transformer. 3. The ground wire disconnection detection device according to claim 2, wherein the number of the transformers is two, each primary winding is connected in series, and the transformer is one of the two transformers. One of the two transformers has a secondary winding connected in series to the closed loop, and the other of the two transformers has a ground wire disconnection that generates a signal indicating whether or not the ground state is normal in the secondary winding. Detection device. 4. An electric / electronic device having a ground wire disconnection detecting device, wherein the ground wire disconnection detecting device is the one described in any one of claims 1 to 3. 5. The electric / electronic device according to claim 4, further comprising a line filter circuit, wherein the line filter circuit includes at least two capacitors, and each of the two capacitors. A four-terminal capacitor, each of the four-terminal capacitors has two terminals each having a capacitor electrode independent of each other, and the two terminals connected to one of the capacitor electrodes are:
One of the terminals, the capacitor electrode and the other of the terminals are connected in series so as to form a circuit including the other of the terminals in series, and one of the two terminals connected to the other of the capacitor electrodes is Electrical / electronic devices connected to each other and the other individually connected to each of the two ground terminals 6. The electric / electronic device according to claim 6, wherein the line filter circuit includes a choke coil and another capacitor, and the choke coil is more than the two capacitors. In the previous stage, the other capacitor is inserted in series with the line, the another capacitor is a four-terminal capacitor, and in the preceding stage of the choke coil, two terminals connected to one of the capacitor electrodes are one of the terminals, An electric / electronic device connected between lines so that a circuit including a capacitor electrode and the other of the terminals in series is formed. 7. The electric / electronic device according to claim 6, wherein a transmission transformer is provided in a front stage or a rear stage of the line filter circuit, and the transmission transformer has an inter-winding electrostatic shield body. The electrostatic shield body has two electrodes that are independent of each other, and the ground wire disconnection detection device serially connects the two electrodes provided on the electrostatic shield body in the closed loop. Electrical and electronic equipment including. 8. The electric / electronic device according to claim 7, wherein the voltage generated in the choke coil or the transmission transformer is used as the ground wire disconnection detection signal.