JPH11242063A - Apparatus and method for injection of noise - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise injection apparatus or the like which is small and lightweight, and by which a noise can be injected safely into a power-supply line while a high voltage is not generated by itself. SOLUTION: A noise generation source NS generates a noise. The noise is supplied, via a switch SW1, a variable resistor VR1, and capacitors C1, C2, to a pair of power-supply ends provided at an apparatus to be tested as an object for a noise test. The noise is cut off substantially by respective poles of a single-phase AC commercial power supply and by choke coils L1, L2 which are connected across the power-supply ends at the apparatus to be tested, and it is not supplied to the side of the commercial power supply. On the other hand, a voltage which is supplied by the commercial power supply is supplied, via the choke coils L1, L2, to the power-supply ends at the apparatus to be tested. As a result, according to the principle of superposition, the sum of a voltage of the noise supplied by the noise generation source NS and the voltage supplied by the commercial power supply is applied to the power-supply ends at the apparatus to be tested.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a noise injector and a noise injection method.

[0002]

2. Description of the Related Art Hitherto, noise (noise), particularly common mode noise (ie, noise applied to both a pair of lines so that electric variables such as current and voltage are substantially in phase) is known. When examining the effects on electrical equipment,
2. Description of the Related Art A technique has been adopted in which noise is injected into an electrical device (device under test) to be tested to check the operation of the device under test.

In the case of injecting noise into a power supply line of a device under test, conventionally, a noise injector that generates and supplies a voltage equivalent to a voltage obtained by superimposing noise on a power supply voltage to be supplied to the device under test has Power is being supplied to the test equipment.

When such a noise injector injects common mode noise, the noise injector and the device under test have a common ground potential. And the noise injector is
The method of generating two AC voltages and supplying the same to the device under test by generating two AC voltages whose phases are different from each other by approximately 180 degrees and whose average potential with respect to the ground potential is equal to the instantaneous value of the common mode noise. Injecting noise.

[0005]

However, according to this method, when the noise injector supplies a voltage corresponding to a commercial power supply, an AC voltage having an effective value of about 100 volts is generated. In this case, since such a noise injector generates a high voltage by itself, there is a great risk of causing a disaster due to electric shock or spark during operation.

[0006] Such a noise injector is 100
In order to generate an AC voltage having an effective value of about volt, it is necessary to provide components such as large capacitors having a withstand voltage of about several hundred volts. This makes the noise injector large and heavy, making it difficult to handle.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and provides a small and lightweight noise injector and safely injects noise into a power supply line without generating a high voltage by itself. And a noise injection method.

[0008]

In order to achieve the above object, a noise injector according to a first aspect of the present invention comprises:
Noise generating means for generating a pair of noises having substantially the same phase in a noise injector for supplying noise to a device under test having a pair of power supply terminals through each of the power supply terminals;
Power superimposing means for superimposing the pair of noises generated by the noise generating means on electric power supplied from an external power supply and supplying the electric power to the pair of power supply terminals. A noise backflow preventing means for substantially preventing the backflow of noise toward the external power supply is provided.

Such a noise injector superimposes each of the noises on the electric power supplied from an external power supply.
It safely injects common mode noise into power supply lines without generating power supply voltage by itself. Further, since such a noise injector does not generate a power supply voltage by itself, even if the power supply voltage is high, there is no need to provide large and heavy components such as a high withstand voltage capacitor. For this reason, such a noise injector becomes small and lightweight.

If the noise backflow prevention means includes means for substantially preventing a pair of currents having substantially the same phase from passing to the external power supply, common mode noise is prevented from flowing to the external power supply. Outflow to the power supply. This makes the injection of common mode noise more efficient,
Further, it is possible to prevent the common mode noise from flowing out to another electric device commonly connected to the external power supply via the external power supply.

The external power supply is, for example, a single-phase AC power supply. In this case, the noise backflow preventing means has, for example, one end connected to each power supply end and the other end connected to the single-phase power supply end. It may be provided with a pair of inductors connected to each pole of the AC power supply, passing the electric signal of the frequency of the single-phase AC power supply, and substantially blocking the electric signal of each of the noise frequencies.

Each of the pair of inductors generates an electromotive force in a direction to cancel an electromotive force induced by the inductor forming a pair with the inductor by a single-phase AC current supplied from the single-phase AC power source. If the inductive coupling means for inducing mutual induction with the inductor is provided, common mode noise supplied from the single-phase AC power supply is prevented from being supplied to the electric device. Further, the situation in which the voltage supplied by the single-phase AC power supply is offset by the electromotive force induced by the pair of inductors by the single-phase AC current supplied from the single-phase AC power supply is also prevented. Be more efficient.

[0013] The power superimposing means may include a mutual inducing means for inducing a voltage of each of the noises in the pair of inductors. Thus, the pair of inductors themselves generate noise, so that the configuration of the noise injector is simplified, and the noise injector is configured to be small and light. Further, since the impedance of the line connecting the external power supply and the device under test is kept low, the power supply is performed efficiently.

[0014] The mutual inducing means includes, for example, means for commonly linking the magnetic flux that induces the voltage of the noise with the pair of inductors to the pair of inductors. Generates noise in the inductor itself.

The power superimposing means includes, for example, means for applying the voltage of each of the noises to a line connecting the pair of inductors and the pair of power supply terminals, thereby reducing the noises to the electric equipment. To the power superimposing means, for example,
The noise may be injected into the electrical device by providing a means for inducing a current of each of the noises in a line connecting the pair of inductors and the pair of power supply terminals.

If the noise generating means includes means for generating a pair of noises having substantially the same phase driven by the external power supply, the noise injector may provide the power supply means with itself. Since the noise is supplied to the electric device without providing the noise injector, the noise injector becomes small and lightweight.

If the noise generating means includes means for generating a pair of noises having phases substantially opposite to each other, it is necessary that the noise injector has a common ground with the electric equipment. Instead, normal mode noise is injected into the electrical equipment.

In this case, if the external power supply is, for example, a single-phase AC power supply, for example, the noise backflow prevention means has one end connected to each power supply end and the other end connected to the power supply end. A noise generating means, comprising a pair of inductors connected to each pole of the single-phase AC power supply, passing an electric signal at the frequency of the single-phase AC power supply, and substantially blocking the electric signal at each of the noise frequencies; Comprises means for inducing a pair of voltages of the noise having substantially opposite phases to each other at both ends of a noise generating inductor, wherein the power superimposing means comprises the pair of inductors and the pair of power supplies. Means for applying a voltage of the noise induced at each end of the noise generating inductor to a line connecting the noise generating inductor to the noise generating inductor. The injected into the electrical device.

If the noise generating means includes means for adjusting the amount of each of the noises supplied to the pair of power supply terminals in accordance with an operation from the outside, the amount of the noise corresponding to the operation of the operator is reduced. The noise is injected into the electrical device.

A noise injector according to a second aspect of the present invention is connected between a noise generating means for generating noise, a power supply terminal of an electric device, and a pole of an external power supply. The power supplied from an external power supply is supplied to each of the power supply terminals, the noise is superimposed on the power and supplied to each of the power supply terminals, and the noise is substantially supplied to the external power supply. And a noise backflow prevention means for preventing noise.

Since such a noise injector superimposes the noise on the power supplied from an external power supply, the noise injector safely injects the noise into the power supply line without generating a power supply voltage by itself. Also, such a noise injector,
Since the power supply voltage is not generated by itself, even if the power supply voltage is high, there is no need to provide a large and heavy component such as a high withstand voltage capacitor. For this reason, such a noise injector becomes small and lightweight.

A noise injection method according to a third aspect of the present invention is a noise injection method for supplying noise to a device under test having a pair of power supply terminals via each of the power supply terminals. A noise generating step for generating a pair of noises having the same phase, and the pair of noises generated by the noise generating step are superimposed on electric power supplied from an external power supply and supplied to the pair of power supply terminals. Power superimposing step, wherein the power superimposing step includes a noise backflow prevention step of substantially preventing each of the noises from flowing back toward the external power supply.

According to such a noise injection method, since each of the noises is superimposed on the power supplied from an external power supply, the step of generating the power supply voltage by itself is not required, and the power supply line can be safely connected to the power supply line. Is injected.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a noise injector and a noise injection method according to embodiments of the present invention will be described by taking a noise injector for injecting noise into a device under test using a single-phase AC commercial power supply as an example. explain.

(First Embodiment) FIG. 1 shows the configuration of a noise injector according to a first embodiment of the present invention.
As shown, the noise injector includes choke coils L1 and L2, capacitors C1 to C4, a noise source NS, a variable resistor VR1, and a switch SW1.

The choke coils L1 and L2 remove harmonic components contained in the commercial power supply, and generate noise generated by the noise source NS at points A1-B1 shown in FIG.
This is to prevent the vehicle from passing through the line between the points A2 and B2.

One end of each of the choke coils L1 and L2 is connected to a pair of poles of a commercial power supply, and the other end of each of the choke coils L1 and L2 is connected to a test object to be tested for noise. It is connected one-to-one to the power input end of the device.

The inductance values of the choke coils L1 and L2 are large enough to prevent the choke coils L1 and L2 from passing an electric signal belonging to the frequency band of noise generated by the noise source NS. However, the inductance values of the choke coils L1 and L2 are small enough to allow the choke coils L1 and L2 to pass an electric signal belonging to the frequency band of the commercial power supply without substantially causing loss.

Each of the choke coils L1 and L2 is, for example, a coil wound on a bifilar coil on the same core. One end of each of the choke coils L1 and L2 connected to each pole of the commercial power supply is Is also the end of the coil on the winding start side, or both are the end of the coil on the winding end side.

When currents of substantially opposite phases (ie, normal mode currents) are supplied from both poles of the commercial power supply, the choke coils L1 and L2 cause the back electromotive force, which is self-induced by the current flowing through each of them. Are induced by mutual induction.

For example, when a current flowing from the end connected to the device under test to the end connected to the commercial power supply flows through the choke coil L1, the choke coil L1 is connected to the commercial power supply by self-induction. Back electromotive force is generated in a direction in which current flows from the connected end to the device connected to the device under test. On the other hand, while the current flowing from the end connected to the device under test to the end connected to the commercial power supply flows through the choke coil L1, the choke coil L2 is connected from the end connected to the commercial power supply to the choke coil L2. A current flows through the end connected to the device under test. Then, this current causes the choke coil L1 to generate an electromotive force that causes a current to flow from the end connected to the device under test to the end connected to the commercial power supply.
Induced by mutual induction.

As a result, the back electromotive force generated by the choke coil L1 due to self-induction and the electromotive force induced in the choke coil L1 by the mutual current induced by the current flowing through the choke coil L2 cancel each other. Similarly, the counter electromotive force generated by the choke coil L2 by self-induction and the electromotive force induced by the current flowing through the choke coil L1 in the choke coil L2 by mutual induction cancel each other out.

For this reason, the normal mode voltage applied to supply the normal mode current from both poles of the commercial power supply does not substantially cause a voltage drop.
Supplied to the equipment under test. And the choke coil L1
L2 and L2 may have a reactance large enough to cause a substantial voltage drop at both ends when signals belonging to the band of the commercial power supply are individually passed.

On the other hand, when currents of substantially the same phase (ie, common mode currents) are supplied to the ends of the choke coils L1 and L2 on the side connected to the device under test, the choke coils L1 and L2 The back electromotive force, which is self-induced by the common mode current flowing through the antenna, is not canceled by the electromotive force generated by the mutual induction.

For example, the back electromotive force generated by the choke coil L1 by self-induction and the electromotive force induced by the current flowing through the choke coil L2 in the choke coil L1 by the mutual induction have the same direction. Similarly, the back electromotive force generated by the choke coil L2 by self-induction and the electromotive force induced by the current flowing through the choke coil L1 in the choke coil L2 by the mutual induction have the same direction.

For this reason, the choke coils L1 and L2
When common mode noise is supplied to the end connected to the device under test, the common mode noise is generated by the back electromotive force which is self-induced by the current flowing through the choke coils L1 and L2, and by mutual induction. The generated electromotive force prevents the commercial power supply from flowing into each pole.

The capacitors C1 and C2 are for generating a ground potential based on the potential of both poles of the commercial power supply. The capacitors C1 and C2 are connected in a cascade, and the connection point of both is grounded. Capacitor C1
Is connected to the connection point between the commercial power supply and the choke coil L1, and the other end of the capacitor C2 that is not connected to the capacitor C1. Is connected to a connection point between the commercial power supply and the choke coil L2. Capacitors C1 and C2
Are substantially equal to each other, so that the potential value at the connection point of the capacitors C1 and C2 is substantially equal to the arithmetic average of the potential values of both poles of the commercial power supply.

The capacitors C3 and C4 are for injecting the noise generated by the noise source NS into the device under test. The capacitors C3 and C4 are connected in a cascade, and a connection point between the two is connected to one end of the variable resistor VR1. Of each end of the capacitor C3, the capacitor C4
Is connected to the connection point between the device under test and the choke coil L1, and of the respective ends of the capacitor C4, the end not connected to the capacitor C3 is
It is connected to the connection point between the device under test and the choke coil L2.

The noise source NS includes an oscillator composed of a blocking oscillation circuit or the like, and generates noise to be injected into a device under test. The noise source NS includes a pair of power input terminals for obtaining a power source for driving an oscillator included in the noise source NS, an output terminal for outputting an AC voltage serving as noise, and a ground terminal (not shown). Each power input terminal is connected one-to-one to each pole of the commercial power supply, the output terminal is connected to one end of the switch SW1, and the ground terminal is grounded.

When commercial power is supplied to each power input terminal of the noise source NS, the commercial power is transformed by a transformer PT and then bridge-connected diodes D1 to D4 as shown in FIG. 2, for example. It rectifies and generates a DC voltage for driving the oscillator. The oscillator driven by this DC voltage contains a frequency component higher than the frequency of the commercial power supply, and generates a signal in which the value of the potential of the DC component is substantially equal to the value of the arithmetic average of the potentials of both poles of the commercial power supply as noise. Then, the noise is applied to one end of the switch SW1.

The ground potential of the device under test is
For example, the ground end of the device under test is connected to the noise source N
By connecting to the ground terminal of S, the potential of the noise source NS (that is, the potential of the connection point between the capacitors C1 and C2) is kept substantially the same. As a result, it is possible to prevent the DC component of the potential of each pole of the commercial power supply from being applied to the device under test as common mode noise.

The variable resistor VR1 is for adjusting the amount of noise injected into the device under test. One end of the variable resistor VR1 is connected to the capacitors C3 and C4 as described above, and the other end is connected to one end of the switch SW1 which is not connected to the noise source NS.

The noise is output from the output terminal of the noise source NS, and includes a variable resistor VR1, capacitors C3 and C3.
4 to the device under test.

The choke coil L1 in the noise band
And L2 have sufficiently large reactance to substantially block signals belonging to the noise band. Further, the back electromotive force induced by the choke coils L1 and L2 supplied with the noise and the choke coils L1 and L2 supplied with the noise.
The electromotive forces induced by each other by mutual induction prevent noise from passing through the choke coils L1 and L2.
Therefore, the noise generated by the noise source NS is supplied to the device under test via the variable resistor VR1 and the capacitors C3 and C4 without being substantially diverted to each pole of the commercial power supply.

On the other hand, when a normal mode current supplied from a commercial power supply flows through the choke coils L1 and L2, self-induced back electromotive force is generated in the choke coils L1 and L2. But these back EMFs are
The choke coils L1 and L2 are attenuated by electromotive forces induced by each other by mutual induction. Therefore, the voltage supplied from the commercial power supply is supplied to the power supply input terminal of the device under test without substantially causing a voltage drop in the choke coils L1 and L2.

Therefore, each power input terminal of the device under test has
According to the principle of superposition, a voltage having a value substantially equal to the sum of the voltage supplied from the noise source NS via the variable resistor VR1 and the capacitors C3 and C4 and the voltage of the commercial power supply is applied. The noise components of the voltage applied to each power input terminal of the device under test have substantially the same phase. In other words, at the power input end of the UUT,
Common mode noise is applied.

The device under test obtains power including noise supplied from the noise injector as a power source and drives it. Then, various kinds of noise tests are executed by testing the operation state due to the noise supplied from the noise injector.

More specifically, for example, the operation of the device under test when a noise injector is used as a power source is compared with the operation of the device under test when a power source containing no noise is used. In the case of a device under test that outputs an electric signal when driven, for example, the common mode voltage rejection ratio of the output electric signal (ie, the ratio of the amplitude of the injected noise to the amplitude of the noise component included in the electric signal) ) Is measured.

The configuration of the noise injector is not limited to the above. For example, the amount of injected noise does not need to be adjusted by the variable resistor VR1, and the amount of injected noise may be fixed.

The oscillator of the noise source NS does not need to be driven by a voltage obtained by transforming and rectifying a commercial power supply, and may be driven by an external power supply such as a battery. In this case, the noise source NS does not need to be connected to both poles of the commercial power supply, and the transformer PT and the diodes D1 to D4 are unnecessary.

This noise injector is provided with a variable resistor V
For example, an attenuator as shown in FIG. 3 may be provided instead of R1. As shown, the attenuator comprises a plurality of stages of three resistors, each connected in a "T" shape. Among the resistors forming each stage, the resistors except one whose one end is connected to the ground terminal are cascaded with each other. One end of the series circuit formed by the cascade-connected resistors is connected to the output end of the noise source NS via the switch SW1, and the other end is connected to the connection point of the capacitors C3 and C4. The ground terminal is connected to the ground terminal of the noise source NS.

The attenuator also includes a plurality of double-pole double-throw switches for electrically disconnecting each stage from the attenuator in accordance with the operation of the operator and electrically bypassing the disconnected stages. The resistance of each resistor forming the attenuator is determined by the value of the capacitor C3 regardless of whether the resistor in each stage is electrically disconnected from the attenuator.
And the impedance of the attenuator from the point of connection of C4 and C4 is selected to be a substantially constant value.

In the noise injector having such an attenuator, the output impedance of the noise is substantially constant irrespective of the amount of injected noise when viewed from the power supply end of the device under test. Therefore, the amount of noise injected into the device under test can be accurately controlled.

The noise injector supplies normal mode noise (that is, noise applied to one of the pair of lines). For example, as shown in FIG.
, The capacitors C1 to C4, the noise source NS, the variable resistor VR1,
A switch SW2 and choke coils L3 and L4 may be provided in addition to the switch SW1.

The switch SW2 is composed of a double-pole single-throw switch, and can switch the other end of the capacitor C3 that is not connected to the device under test to be connected to one of the variable resistor VR1 and the ground. It is.
The choke coil L3 is connected to the device under test and the capacitor C3.
And a connection point between the commercial power supply and the capacitor C1. The choke coil L4 is connected between a connection point between the device under test and the capacitor C4 and a connection point between the commercial power supply and the capacitor C2.

The reactance of the choke coils L3 and L4 in the noise band is sufficiently large to substantially block signals belonging to the noise band. On the other hand, the reactances of the choke coils L3 and L4 in the band of the commercial power supply are sufficiently small, and pass signals belonging to the band of the commercial power supply substantially without any loss.

If the noise source NS generates noise while the switch SW2 is switched so that the other end of the capacitor C3 not connected to the device under test is grounded, the noise is generated by the noise source NS. And is supplied to one power input terminal of the device under test via the variable resistor VR1 and the capacitor C4. The choke coil L4 prevents the noise supplied via the capacitor C4 from shunting to one pole of the commercial power supply,
The choke coil L3 prevents noise supplied from one power supply input terminal of the device under test from flowing into the other pole of the commercial power supply via the other power supply input terminal of the device under test.

Therefore, the variable resistor VR1 and the capacitor C4 from the noise source NS are connected to the power input terminal connected to the capacitor C4 among the power input terminals of the device under test in accordance with the principle of superposition. A voltage having a value substantially equal to the sum of the voltage supplied via the power supply and the voltage of the commercial power supply is applied. That is, normal mode noise is injected into the device under test.

The normal mode noise injected into the device under test flows to the ground via the terminal connected to the capacitor C3 of the power input terminals of the device under test and the capacitor C3. Therefore, even when the reactance of the choke coil L3 in the noise band is sufficiently large, normal mode noise is efficiently injected into the device under test.

Further, the noise injector may be configured to inject noises having different polarities into each power input terminal of the device under test, thereby flowing into one power input terminal of the device under test. An amount of noise substantially equal to the amount of noise flows out of the other power input of the UUT.
Therefore, it is possible to prevent noise from flowing out to the ground common to the noise injector and the device under test. Therefore, even if this noise injector does not have a common ground with the UUT, it can inject normal mode noise into the UUT, and even if it has a common ground, Instability of the ground potential due to a voltage drop generated by the current flowing to the ground can be avoided.

A noise injector according to a modification in which noises having different polarities are injected into each power input terminal of the device under test has, for example, a configuration shown in FIG. As shown
This noise injector includes a transformer T and a capacitor C in addition to choke coils L3 and L4, capacitors C1 and C2, a noise source NS, a variable resistor VR1, and a switch SW1.

The choke coils L3 and L4 are substantially the same as those in the noise injector shown in FIG.
1, and the choke coil L4 is connected between the connection point of the commercial power supply and the capacitor C2 and the device under test.

The hot end of the primary winding of the transformer T is connected to the end of the variable resistor VR1 that is not connected to the switch SW1, and the cold end is grounded. The hot end of the secondary winding of the transformer T is connected to one end of the capacitor C, and the cold end is connected to a connection point between the choke coil L4 and the device under test.
Of the two ends of the capacitor C, the other end that is not connected to the transformer T is connected to a connection point between the choke coil L3 and the device under test.

When the noise source NS generates a current, the current is output from the output terminal of the noise source NS and supplied to the primary winding of the transformer T via the variable resistor VR1. As a result, a voltage proportional to the AC amplitude of the current supplied to the primary winding of the transformer T is generated between both ends of the secondary winding of the transformer T. The voltage at one end of the secondary winding of the transformer T is supplied as noise to one power supply input terminal of the device under test via the capacitor C, and the voltage at the other end is supplied to the other power supply input terminal of the device under test. Provided as noise.

The choke coil L3 prevents noise supplied from the secondary winding of the transformer T via the capacitor C from shunting to one pole of the commercial power supply.
4 prevents noise supplied from the secondary winding of the transformer T from flowing into the other pole of the commercial power supply.

Therefore, the sum of the voltage supplied from one end of the secondary winding of the transformer T via the capacitor C and the voltage of the commercial power supply is applied to one power input terminal of the equipment under test in accordance with the principle of superposition. A voltage having a value substantially equal to is applied. In addition, a value substantially equal to the sum of the voltage supplied from the other end of the secondary winding of the transformer T and the voltage of the commercial power supply is applied to the other power input terminal of the UUT according to the principle of superposition. Is applied.

Since both ends of the secondary winding of the transformer T generate voltages having different polarities, noises having different polarities are injected into each power supply input terminal of the device under test. As a result, normal mode noise is injected into the device under test without passing through the ground loop.

The noise injector according to the modified example in which noises having different polarities are injected into each power supply input terminal of the device under test is not limited to the above-described one, but may have a configuration shown in FIG. 6, for example. As shown, this noise injector is
In addition to choke coils L3 and L4 substantially the same as those shown in FIG. 4, capacitors C1 to C4, a noise source NS and a switch SW1 substantially the same as those shown in FIG. VR2, buffer BUF,
It comprises an inverting amplifier INV. However, the end of the capacitor C3 that is not connected to the device under test is connected to the output terminal of the buffer BUF, and the other end of the capacitor C4 that is not connected to the device under test is inverted. It is connected to the output terminal of the amplifier INV described later.

The variable resistor VR2 outputs a voltage obtained by dividing the voltage applied between the first and second terminals at a ratio according to the operation of the operator from the third terminal. A first terminal of the variable resistor VR2 is connected to the output terminal of the noise source NS via a switch SW1, a second terminal is grounded, and a third terminal is a buffer BUF and an inverting amplifier IN.
Connected to V input.

The buffer BUF has an input terminal and an output terminal, and outputs from the output terminal a voltage substantially equal to the voltage applied to the input terminal. The inverting amplifier INV also has an input terminal and an output terminal, and supplies from the output terminal a voltage substantially equal to the inverted version of the voltage applied to the input terminal. The output end of the buffer BUF is connected to the end of the capacitor C3 that is not connected to the power input end of the device under test, and the output end of the inverting amplifier INV is connected to the end of the capacitor C4. Connected to the end of the UUT that is not connected to the power input end.

In this noise injector, the noise voltage output from the output terminal of the noise source NS is divided by the variable resistor VR2 and then applied to the input terminals of the buffer BUF and the inverting amplifier INV. The buffer BUF is
Since the inverting amplifier INV outputs a voltage substantially equal to the polarity of the voltage applied to the input terminal, while outputting a voltage substantially equal to the voltage applied to the input terminal, the device under test Each of the power input terminals has a capacitor C
3, noises having different polarities are injected through C4. As a result, normal mode noise is injected into the device under test without passing through the ground loop.

(Second Embodiment) In the first embodiment, the noise is injected into the device under test via the capacitor, but the method of injecting the noise into the device under test is as follows.
It is not limited to the technique of injecting via a capacitor. Hereinafter, a noise injector according to a second embodiment of the present invention, in which noise is injected using a transformer, will be described.

FIG. 7 shows the configuration of this noise injector.
As shown, the noise injector includes transformers T1 and T2, a noise source NS, a variable resistor VR1, and a switch SW1. A noise source NS;
The variable resistor VR1 and the switch SW1 are substantially the same as those in the first embodiment.

Each pole of the commercial power supply is connected one-to-one to the cold end of the secondary winding of transformer T1 and to the cold end of the secondary winding of transformer T2.

Each power supply input terminal of the noise source NS is connected to each pole of the commercial power supply on a one-to-one basis, and the output terminal is connected to a switch S.
W1 is connected to one end of the transformer T1 and T2
Are connected to the connection points between the cold ends of the primary windings.

One end of the variable resistor VR1 is connected to a connection point between the other ends of the primary windings of the transformers T1 and T2, and the other end of the variable resistor VR1 is connected to one of the ends of the switch SW1.
It is connected to the end that is not connected to the noise source NS.

The transformers T1 and T2 are connected to a noise source NS.
This is for injecting the generated noise into the device under test. The hot end of the primary winding of the transformer T1 is connected to the power input end of the device under test, and the cold end is connected to one pole of the commercial power as described above. Transformer T2
The hot end of the primary winding is connected to the power input end of the equipment under test, and the cold end is connected to the other pole of the commercial power supply as described above. The hot ends of the secondary windings of the transformers T1 and T2 are connected to each other, and the cold ends are also connected to each other.

The ratio of the number of turns of the primary winding of the transformer T1 to the number of turns of the secondary winding is substantially the same as the ratio of the number of turns of the primary winding of the transformer T2 to the number of turns of the secondary winding. Has substantially the same inductance as the primary winding of the transformer T2. Therefore, the current supplied from the noise source NS via the variable resistor VR1 is almost equally divided into the primary windings of the transformers T1 and T2, and as a result, the secondary windings of the transformers T1 and T2 are changed. Electromotive forces are induced in the lines with approximately equal amplitudes. The polarity of the electromotive force is the same between the hot ends (and between the cold ends) of the transformers T1 and T2.

When the transformers T1 and T2 are supplied with normal mode currents from both poles of the commercial power supply to the respective secondary windings, the respective secondary windings are self-induced by the self-induction. A back electromotive force is generated to cancel the current in the mode. On the other hand, the normal mode current supplied to the secondary windings of the transformers T1 and T2 induces an electromotive force in each of the primary windings due to mutual induction, and the induced electromotive force is applied to each of the primary windings. As a result, an electromotive force is induced in each other's secondary winding by mutual induction. The electromotive force induced in each secondary winding by mutual induction is in a direction to cancel the above-mentioned counter electromotive force generated in each secondary winding by self-induction.

For this reason, the normal mode voltage applied to supply the normal mode current from both poles of the commercial power supply does not substantially cause a voltage drop in the transformers T1 and T2, and the device under test Supplied to
The secondary windings of transformers T1 and T2 have reactances large enough to cause a substantial voltage drop across both ends when signals belonging to the band of the commercial power supply are individually passed. You may.

The alternating current generated by the noise source NS is
From the output terminal of the oscillator of the noise source NS, the switch SW
1. The current flows from the hot end of the primary winding of the transformers T1 and T2 through the cold end to the ground terminal of the oscillator via the variable resistor VR1.

As a result, an electromotive force having a magnitude proportional to the amplitude of the noise generated by the noise source NS is generated in the secondary windings of the transformers T1 and T2. This electromotive force supplies noise to the device under test. On the other hand, transformers T1 and T
The second secondary winding allows the current supplied from the commercial power supply to pass through without causing substantial loss, so that the current supplied from the commercial power supply flows directly to the power input terminal of the device under test.

Therefore, each power input terminal of the device under test has
A voltage having a value substantially equal to the sum of the voltage generated on the secondary windings of the transformers T1 and T2 and the voltage of the commercial power supply is applied. Then, among the currents flowing through the power input terminals of the device under test, noise components are substantially in phase with each other. That is, common mode noise is applied to the power input terminal of the device under test.

The configuration of the noise injector is not limited to the above. For example, this noise injector is shown in FIG.
, A switch SW2 that can be switched to connect the hot end of the primary winding of the transformer T1 to one of the hot end of the primary winding of the transformer T2 and the ground may be provided. When noise is generated with the switch SW2 switched so that the hot end of the primary winding of the transformer T1 is grounded, normal mode noise is injected into the device under test.

In the noise injector shown in FIG. 8 as well, transformers T1 and T2 are connected to respective secondary windings when normal mode current is supplied from both poles of the commercial power supply. A back electromotive force is generated in the line by the self-induction so as to cancel the current in the normal mode. on the other hand,
The normal mode current supplied to the secondary windings of the transformers T1 and T2 induces a mutual induction electromotive force in each of the primary windings, and this induced electromotive force is applied to each other's primary winding. As a result, an electromotive force is induced in each other's secondary winding by mutual induction.

However, when noise is injected in a state where the switch SW2 is switched so that the hot end of the primary winding of the transformer T1 is grounded, the counter electromotive force generated in the secondary winding of the transformer T1 is injected. The power is not canceled by the electromotive force induced by the mutual induction in the primary winding of the transformer T1. However, in this case, both ends of the primary winding of the transformer T1 are short-circuited, so that the reactance of the transformer T1 viewed from both ends of the secondary winding of the transformer T1 causes noise generation even in the band of the commercial power supply. Even in the noise band generated by the source NS, the noise is reduced to such an extent that substantially no voltage drop occurs across the transformer T1.

Further, this noise injector injects normal mode noise into the UUT without passing through a ground loop by injecting noises having different polarities into each power supply input terminal of the UUT. It may be.

Specifically, as shown in FIG. 9, for example, the hot end of the primary winding of the transformer T1 is connected to the variable resistor VR1.
And the cold end of the transformer T1 is connected to the variable resistor VR1 and the hot end is grounded by the noise mode switch. I just need.

By operating the noise mode changeover switch, the hot end of the primary winding of the transformer T1 is changed to the variable resistor VR1.
And when the cold end is grounded, the noise injector operates as described above.
On the other hand, when the cold end of the primary winding of the transformer T1 is connected to the variable resistor VR1 and the hot end is grounded, the secondary winding of the transformer T1 is connected to the secondary winding of the transformer T2. And an electromotive force having a polarity opposite to that of the electromotive force induced by the electromotive force is generated. That is, for example, when the electromotive force is generated in such a direction that the hot end of the secondary winding of the transformer T2 has a positive polarity, the size of the transformer T1
The electromotive force is generated substantially the same as the electromotive force induced in No. 2 and in a direction such that the hot end has a negative polarity.

As a result, noises having different polarities are injected into each power supply input terminal of the device under test, so that normal mode noise is injected into the device under test without passing through the ground loop.

In the noise injector shown in FIG. 9, when the transformers T1 and T2 are supplied with normal mode current from both poles of the commercial power supply to the respective secondary windings, the respective transformers T1 and T2 operate as follows. A back electromotive force is generated in the line by the self-induction so as to cancel the current in the normal mode. on the other hand,
The normal mode current supplied to the secondary windings of the transformers T1 and T2 induces a mutual induction electromotive force in each of the primary windings, and the induced electromotive force is applied to each other's primary windings. As a result, an electromotive force is induced in each other's secondary winding by mutual induction. When the noise mode changeover switch is set so that noises having different polarities are injected into each power supply input terminal of the device under test, the back electromotive force generated in each secondary winding of the transformers T1 and T2. Is the same as the direction of the electromotive force induced by mutual induction in these secondary windings.

In this case, in order for the voltage of the commercial power supply to be supplied to the equipment under test without substantially causing a voltage drop, these secondary windings transmit signals belonging to the band of the commercial power supply. It is set so as to have a small reactance such that a voltage drop does not substantially occur at both ends when each is passed alone.

(Third Embodiment) In the second embodiment, the noise is injected into the device under test via the transformer, but in the second embodiment, the choke coil L
The transformer may perform the functions performed by 1 and L2. As a result, the circuit configuration is simplified, the impedance of the line connecting each pole of the commercial power supply and the device under test is suppressed lower than in the second embodiment, and the power supply is efficiently performed. Done. In the following, a third embodiment of the present invention will be described in which a transformer for injecting noise performs the function of a choke coil.
The noise injector according to the embodiment will be described.

FIG. 10 shows the configuration of this noise injector. As shown, the noise injector includes a transformer T3
, A noise source NS, a variable resistor VR1, and a switch SW1. The noise source NS, the variable resistor VR1, and the switch SW1 are substantially the same as those in the first and second embodiments.

The transformer T3 consists of three coils wound around a trifiler on the same core, one of the three coils forming a primary winding and the other two coils being separate coils from each other. Make the next winding. The number of turns of the two secondary windings of the transformer T3 is substantially equal.

One end of each of the two coils forming the secondary winding of the transformer T3 is connected one-to-one to each pole of the commercial power supply. The ends of these two secondary windings that are connected to the respective poles of the commercial power supply are either ends of the winding start side of these coils, or are both end ends of the windings of these coils. Is the end of

For this reason, when a normal mode current is supplied from both poles of the commercial power supply, each secondary winding of the transformer T3 is driven in such a manner as to cancel the back electromotive force which is self-induced by the current flowing therethrough. Power is induced in each other by mutual induction. As a result, the electromotive force induced by the current flowing through one secondary winding in the other secondary winding due to the mutual induction and the back electromotive force generated by the other secondary winding by the self-induction are mutually different. Cancel each other out.

[0098] Of the two ends of these two coils forming the secondary winding of the transformer T3, the end not connected to each pole of the commercial power supply is connected to a power input end of the equipment under test by a pair. 1
Connected to. Therefore, the normal mode voltage applied to supply the normal mode current from both poles of the commercial power supply does not substantially cause a voltage drop,
Supplied to the equipment under test. Each secondary winding of the transformer T3 has a reactance large enough to generate a voltage drop across both ends when signals belonging to the band of the commercial power supply are individually passed. Is also good.

Each power supply input terminal of the noise source NS is connected to each pole of the commercial power supply on a one-to-one basis, and the output terminal is connected to a switch S.
W1 is connected to one end, and the ground end is connected to one end of the primary winding of the transformer T3. One end of the variable resistor VR1 is connected to the other end of the primary winding of the transformer T3,
The other end of the switch 1 is connected to one end of the switch SW1 which is not connected to the noise source NS.

The AC current generated by the noise source NS is
From the output terminal of the oscillator of the noise source NS, the switch SW
1. The current flows through the primary winding of the transformer T3 to the ground terminal of the oscillator via the variable resistor VR1.

When current is supplied to the primary winding of the transformer T3, an electromotive force is induced in each secondary winding of the transformer T3 by a mutual induction action. The polarity of the electromotive force is the same at the winding start ends (and at the winding end sides) of the secondary windings of the transformer T3.

Since the number of turns of each secondary winding of transformer T3 is substantially equal to each other, the amplitudes of electromotive forces induced in each secondary winding are substantially equal to each other. Accordingly, in each secondary winding of the transformer T3, an electromotive force having a magnitude proportional to the amplitude of the noise generated by the noise source NS and having substantially the same amplitude is generated. These electromotive forces supply noise to the device under test without substantially flowing current to each pole of the commercial power supply.

On the other hand, since each secondary winding of the transformer T3 allows the current supplied from the commercial power supply to pass without causing substantial loss, the current supplied from the commercial power supply is It flows to the input end.

Therefore, each power input terminal of the device under test has
A voltage having a value substantially equal to the sum of the voltage generated at each secondary winding of the transformer T3 and the voltage of the commercial power supply is applied. Then, of the current flowing through each power input terminal of the UUT,
The components of the noise are substantially in phase with each other. That is,
Common mode noise is applied to the power input terminal of the device under test.

The configuration of the noise injector is not limited to the above. For example, the three windings of the transformer T3 do not necessarily have to be wound on a trifilar. In the transformer T3, the polarity of the electromotive force induced in each of the secondary windings by the current flowing through the primary winding of the transformer T3 is opposite to that of the other end connected to the commercial power supply (or connected to the equipment under test). It is only necessary that the terminal can be connected to the commercial power supply and the device under test so that the two terminals have the same polarity.

Further, the noise injector injects noises having different polarities into respective power supply input terminals of the device under test so that normal mode noise is injected into the device under test without passing through a ground loop. It may be. Therefore, this noise injector may have, for example, the configuration shown in FIG.

As shown, in the noise injector of FIG. 11, each secondary winding of the transformer T3 has (a) one of the secondary windings, the winding start side of the secondary winding. Is connected to one pole of the commercial power supply, the end on the winding end side is connected to one power input terminal of the UUT,
(B) With respect to the other secondary winding, the end on the winding end side of the secondary winding is connected to the other pole of the commercial power supply, and the end on the winding start side is the other power input of the UUT. It has substantially the same configuration as the noise injector of FIG. 10 except that it is connected to the end.

In the noise injector of FIG. 11, when an alternating current generated by the noise source NS flows through the primary winding of the transformer T3, a pair of inductions induced in each secondary winding of the transformer T3. The current flows in one direction from the commercial power supply toward the device under test, and the other flows in the direction from the device under test toward the commercial power supply.

More specifically, for example, when it is assumed that an electromotive force is generated in each secondary winding of the transformer T3 in such a direction that the end on the winding start side has a positive polarity, for example. FIG.
Performs the operations described below as (1) and (2).

(1) The secondary winding whose end on the winding start side is connected to the device under test has a current component constituting noise that is proportional to the electromotive force generated by itself. An induced current having a magnitude and flowing from the commercial power supply to the device under test is superimposed on the current flowing through the device under test. (2) On the other hand, the secondary winding whose one end on the winding start side is connected to the commercial power supply has the other secondary winding added by the operation of (1) as a current component constituting noise. An induced current having a magnitude substantially equal to the current component and flowing from the device under test to the commercial power supply is superimposed on the current flowing through itself.

As a result, the noise injector of FIG. 11 injects noise having different polarities into each power supply input terminal of the device under test. Therefore, normal mode noise is injected into the device under test without passing through the ground loop.

Further, the noise injector may inject one of a common mode noise and a normal mode noise into each power input terminal of the device under test in accordance with an operation of a user or the like. Specifically, for example, FIG.
As shown in FIG. 2, the two states indicated as (x) and (y) below may be switched by the noise mode switch for one predetermined secondary winding of the transformer T3.

(X) A state in which the end on the winding start side is connected to a predetermined pole of the commercial power supply, and the end on the winding end side is connected to a predetermined power supply input end of the device under test. (Y) a state in which the end on the winding start side is connected to the predetermined power input terminal of the UUT and the end on the winding end side is connected to the predetermined pole of the commercial power supply; What is necessary is just to make it switchable by a noise mode changeover switch.

When the user or the like operates the noise mode changeover switch to set this noise injector to the state (x),
The noise injector of FIG. 12 performs substantially the same operation as the operation of the noise injector of FIG. 10 described above. On the other hand, (y)
In the state described above, the noise injector of FIG. 12 performs substantially the same operation as the operation of the noise injector of FIG. That is, the noise injector of FIG. 12 injects one of a common mode noise and a normal mode noise into each power supply input terminal of the device under test according to an operation of a user or the like.

[0115]

As described above, according to the present invention, a small and lightweight noise injector can be realized, and noise can be safely injected into a power supply line without generating a high voltage by itself. A noise injector and a noise injection method are realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a noise injector according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a structure of a noise source.

FIG. 3 is a circuit diagram showing a modified example of the noise injector shown in FIG. 1;

FIG. 4 is a circuit diagram showing a modified example of the noise injector shown in FIG. 1;

FIG. 5 is a circuit diagram showing a modification of the noise injector shown in FIG. 1;

FIG. 6 is a circuit diagram showing a modified example of the noise injector shown in FIG. 1;

FIG. 7 is a circuit diagram showing a configuration of a noise injector according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram showing a modification of the noise injector shown in FIG. 7;

FIG. 9 is a circuit diagram showing a modified example of the noise injector shown in FIG. 7;

FIG. 10 is a circuit diagram showing a configuration of a noise injector according to a third embodiment of the present invention.

FIG. 11 is a circuit diagram showing a modification of the noise injector shown in FIG.

FIG. 12 is a circuit diagram showing a modified example of the noise injector shown in FIG.

[Explanation of symbols]

 BUF buffer C, C1 to C4 Capacitor D1 to D4 Diode INV Inverting amplifier L1 to L4 Choke coil NS Noise source PT, T, T1 to T3 Transformer SW1, SW2 Switch VR1, VR2 Variable resistor

Claims (14)

[Claims] 1. An apparatus under test having a pair of power supply terminals,
A noise injector that supplies a pair of noises having substantially the same phase; and a pair of noises generated by the noise generating unit. Power superimposing means for superimposing on the power supplied by the power supply and supplying the power to the pair of power supply terminals, wherein the power superimposing means substantially prevents each of the noises from flowing back toward the external power supply. A noise injector comprising: a noise backflow prevention means for blocking. 2. The noise backflow preventing means further comprises means for substantially preventing a pair of substantially in-phase currents from passing through to the external power supply. A noise injector according to claim 1. 3. The external power supply is a single-phase AC power supply, and the noise backflow prevention means has one end connected to each power supply end, and the other end connected to each of the single-phase AC power supplies. 3. A pair of inductors connected to the poles, passing an electric signal at the frequency of the single-phase AC power supply and substantially blocking the electric signal at each of the noise frequencies. 4. A noise injector according to claim 1. 4. Each of the pair of inductors generates an electromotive force in a direction to cancel an electromotive force self-induced by the inductor forming a pair with the inductor by a single-phase AC current supplied from the single-phase AC power supply. 4. The noise injector according to claim 3, further comprising: an inductive coupling unit that mutually induces with the inductor that forms a pair with the inductor. 4. 5. The noise injector according to claim 3, wherein the power superimposing means includes a mutual induction means for inducing a voltage of each of the noises in the pair of inductors. 6. The mutual induction means generates a magnetic flux such that the pair of inductors induces a voltage of each of the noises.
The noise injector according to claim 3, 4 or 5, further comprising means for linking the pair of inductors in common. 7. The power superimposing means includes means for applying a voltage of each of the noises to a line connecting the pair of inductors and the pair of power supply terminals. The noise injector according to 3 or 4. 8. The power superimposing means includes means for inducing a current of each of the noises in a line connecting the pair of inductors and the pair of power supply terminals. 6. The noise injector according to 4 or 5. 9. The noise injection device according to claim 1, wherein said noise generation means includes means for generating a pair of substantially in-phase noises driven by said external power supply. vessel. 10. The noise injector according to claim 1, wherein said noise generating means includes means for generating a pair of noises having phases substantially opposite to each other. 11. The external power supply is a single-phase AC power supply. The noise backflow prevention means has one end connected to each of the power supply ends, and the other end connected to each of the single-phase AC power supplies. A pair of inductors connected to the poles, passing the electric signal at the frequency of the single-phase AC power supply, and substantially blocking the electric signal at the frequency of each of the noises; Means for inducing a pair of noise voltages substantially in opposite phases to each other at both ends of the inductor, wherein the power superimposing means connects the pair of inductors and the pair of power supply terminals; 11. The noise injector according to claim 10, further comprising: a unit configured to apply a voltage of the noise induced to each end of the noise generating inductor. 12. 12. The apparatus according to claim 1, wherein said noise generating means includes means for adjusting the amount of each of said noises supplied to said pair of power supply terminals in accordance with an operation from outside. The described noise injector. 13. A power supply terminal connected between a power supply terminal provided in an electric device and a pole provided in an external power supply, and configured to supply power supplied from the external power supply to each of the power supply terminals. Noise superimposing means for superimposing the noise on the power and supplying the power to each of the power supply terminals, and substantially preventing the noise from being supplied to the external power supply. Characterized noise injector. 14. A noise injection method for supplying noise to a device under test having a pair of power supply terminals through each of said power supply terminals, wherein a noise generating step of generating a pair of substantially in-phase noises. And a power superimposing step of superimposing the pair of noises generated in the noise generating step on electric power supplied from an external power supply and supplying the superposed power to the pair of power supply terminals. A noise backflow preventing step of substantially preventing each of the noises from flowing back toward the external power supply.