JP2007033303A - Electric current detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric current detector capable of detecting correctly the self-phase current or an electric current to be measured by removing the influence of magnetic flux from other-phase currents. <P>SOLUTION: The electric current detector enclosing a conductor 3, through which electric current flows, is equipped with two magnetic substance cores 10 and 11 prepared to form void parts 12 and 13 at each opposite position in a magnetic path formed from electric current, magnetic flux detecting elements 14 and 15 arranged at each void part, respectively, and a detector circuit section 60 computing the value of electric current by adding or subtracting the output signals from each magnetic flux detecting element 14 and 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a current detection device including a Hall element that measures a magnetic field generated by a current.

  A conventional current detection device has a magnetic core that generates a magnetic field according to a current to be measured, and the magnetic core has at least one air gap, and a hole for detecting a magnetic field in order to obtain a wide dynamic range. Two elements are provided in the gap (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-350470 (page 8, FIG. 1)

  In the conventional current detection device, when the current detection device is configured on the substrate, the current detection device is influenced by the other-phase current when detecting the self-phase current. That is, there is a problem that the Hall element for detecting the self-phase current erroneously detects the magnetic field generated by the other-phase current other than the self-phase current that is the current to be measured.

  The present invention has been made to solve the above-described problems, and obtains a current detection device that eliminates the influence of a magnetic field from other-phase current and accurately detects a self-phase current that is a current to be measured. It is.

  The current detection device according to the present invention includes two magnetic cores arranged so as to surround each conductor through which a current flows and to have respective air gap portions at opposite positions in a magnetic path formed by the current, and to each air gap Each of the magnetic flux detection elements disposed in the unit, and a detection circuit unit that calculates a current value by adding or subtracting the output signals of the magnetic flux detection elements.

  The current detection device according to the present invention includes two magnetic cores arranged so as to surround each conductor through which a current flows and to have respective air gap portions at opposite positions in a magnetic path formed by the current, and to each air gap Each of the magnetic flux detection elements arranged in the unit and a detection circuit unit that calculates the current value by adding or subtracting the output signal of each magnetic flux detection element. It is possible to obtain a current detection device that eliminates and accurately detects the self-phase current that is the current to be measured.

Embodiment 1 FIG.
FIG. 1 shows a configuration diagram of a magnetic flux detection unit of a current detection device according to Embodiment 1 for carrying out the present invention. 1A is a perspective view, and FIG. 1B is a cross-sectional view. In FIG. 1, the magnetic flux detection unit includes an upper magnetic core 10 and a lower magnetic core 11 that are two magnetic cores forming an annular magnetic core, and a Hall element 14 that is a magnetic flux detection element. 15. The upper magnetic core 10 and the lower magnetic core 11 surround the first bus bar 3 which is a conductor through which a current flows, and are respectively at opposite positions in a magnetic path formed by the current flowing through the first bus bar 3. Are arranged so as to form the gap portions 12 and 13. The positions of the air gaps 12 and 13 are determined so that the direction of the magnetic flux in the air gap 12 and the direction of the magnetic flux in the air gap 13 are reversed. A hall element 14 is disposed in the gap portion 12, and a hall element 15 is disposed in the gap portion 13.

  A first bus bar 3 through which a self-phase current Ib1 that is a detected current flows and a second bus bar 4 through which another phase current Ib2 other than the self-phase current flows are arranged on the circuit board 2, and the first bus bar 3 The upper magnetic body core 10 and the lower magnetic body core 11 are arranged so as to surround the circuit board 2. The upper magnetic core 10 and the lower magnetic core 11 are U-shaped each having a certain thickness. The upper magnetic core 10 and the lower magnetic core 11 are arranged such that the two protrusions face each other and the end surfaces of the two protrusions almost overlap each other when viewed from the vertical direction of the circuit board 2. . The upper magnetic core 10 and the lower magnetic core 11 are arranged symmetrically with respect to the center line of the current inflow / outflow cross section of the first bus bar 3. The Hall elements 14 and 15 are disposed so as to be substantially at the center of the two protrusions of the upper magnetic core 10 and are mounted on the circuit board 2.

  The sizes of the gaps of the gap portions 12 and 13 are the same. That is, the lengths of the gaps of the gaps 12 and 13 are the same. The reason why the lengths of the gaps are made equal is as follows. When the lengths of the air gaps are different, the output sensitivity of the Hall elements 14 and 15 arranged in the short air gap is increased with respect to the leakage of magnetic flux from the upper magnetic body core 10 and the lower magnetic body core 11, This is because the output voltage balance of the Hall elements 14 and 15 is deteriorated. In the ideal case where there is no leakage of magnetic flux, the gap length variation does not seem to be a problem. However, in reality, the length of the air gap and the amount of leakage of the magnetic flux are correlated, and the magnetic flux density in the Hall elements 14 and 15 also changes depending on the length of the air gap. When the balance of the output voltages of the Hall elements 14 and 15 is deteriorated, there is a problem that the influence of the magnetic field from the other-phase current Ib2 cannot be completely eliminated. For this reason, the balance of the output voltages of the Hall elements 14 and 15 can be adjusted by making the lengths of the gaps 12 and 13 equal.

  FIG. 2 shows a circuit diagram of the current detection device according to the first embodiment. The current detection device includes a magnetic flux detection unit 50 and a detection circuit unit 60 that calculates a current value by adding or subtracting the output signals of the Hall elements 14 and 15 as the magnetic flux detection elements. The detection circuit unit 60 is mounted on the circuit board 2 in the same manner as the Hall elements 14 and 15. On the circuit board 2, a circuit element for realizing a function different from the current detection function, a power source for driving the circuit element, and the like are also mounted. Thus, by mounting circuit elements having functions other than current detection on the same substrate, the entire system can be reduced in size and cost.

  The detection circuit unit 60 includes a current supply unit 30 including two current supply sources 21 and 22 that drive the Hall elements 14 and 15 that are the magnetic flux detection elements, and the Hall elements 14 and 15 that are the magnetic flux detection elements. Two differential amplifiers 70 and 71 that differentially amplify the output voltage, and a differential amplifier 72 that is an arithmetic unit that adds or subtracts each output voltage differentially amplified by the two differential amplifiers 70 and 71. It is configured.

  The Hall element 14 is driven by the Hall element drive current Ih01 supplied from the current supply source 21, and outputs a voltage proportional to the magnetic flux density generated by the current flowing through the first bus bar 3. The hall element 15 is driven by the hall element drive current Ih02 supplied from the current supply source 22, and outputs a voltage proportional to the magnetic flux density generated by the current flowing through the first bus bar 3. Ih01 and Ih02 are equivalent current values. The magnitude of the current flowing through the first bus bar 3 is proportional to the magnetic flux density detected by the Hall elements 14 and 15. The output voltage of the Hall element 14 is amplified by the differential amplifier 70, and the output voltage of the Hall element 15 is amplified by the differential amplifier 71. The differential amplifier 70 includes an operational amplifier AP70 and resistors R701, R702, R703, and R704, and the differential amplifier 71 includes an operational amplifier AP71 and resistors R711, R712, R713, and R714.

  The two output voltages amplified by the differential amplifiers 70 and 71 are subtracted by the differential amplifier 72 and output from the differential amplifier 72 as a detection voltage signal proportional to the magnitude of the current flowing through the first bus bar 3. . The differential amplifier 72 includes an operational amplifier AP72 and resistors R721, R722, R723, and R724. The detection voltage signal is processed by a control circuit unit configured by a microcomputer or the like (not shown).

  Here, the reason why the influence of the magnetic field from the other-phase current that is the current flowing through the bus bar other than the first bus bar 3 to be measured can be eliminated will be described. As shown in FIG. 1B, the self-phase current Ib1 that is a current flowing through the first bus bar 3 is from the upper surface to the lower surface, and the other-phase current Ib2 that is a current flowing through the second bus bar 4 is from the upper surface to the lower surface. Is flowing. Due to the self-phase current Ib1, a loop-shaped magnetic field is generated around the first bus bar 3 in the clockwise direction. The magnetic flux density from the self-phase current Ib1 in the gap portion 12 is B11, and the magnetic flux density from the self-phase current Ib1 in the gap portion 13 is B12. The magnetic flux density B11 and the magnetic flux density B12 have the same size and the opposite directions.

  Due to the other-phase current Ib2, a loop-shaped magnetic field is also generated around the second bus bar 4 in the clockwise direction. The magnetic flux density from the other phase current Ib2 in the gap portion 12 is B13, and the magnetic flux density from the other phase current Ib2 in the gap portion 13 is B14. The distance to the second bus bar 4 is shorter in the gap 13 than in the gap 12, so that the magnetic flux density B14 is larger than the magnetic flux density B13. However, since the distance between the second bus bar 4 and the gaps 12 and 13 is large, the distance from the second bus bar 4 to the gap 12 is equal to the distance from the second bus bar 4 to the gap 13. Thus, the magnetic flux density B13 and the magnetic flux density B14 are substantially equal. The direction of the magnetic flux density B13 and the direction of the magnetic flux density B14 are the same direction.

From this, the magnetic flux density B1 in the gap portion 12 and the magnetic flux density B2 in the gap portion 13 generated by the self-phase current Ib1 and the other-phase current Ib2 are expressed as in the equations (1) and (2). be able to.
B1 = B11 + B13 (1)
B2 = −B12 + B14 (2)

By subtracting the detection voltage proportional to the magnetic flux density B1 and the detection voltage proportional to the magnetic flux density B2 by the detection circuit unit 60, the magnetic flux density B13 and the magnetic flux density B14 having the same magnitude can be removed. it can. That is, when B13 = B14 and subtracting equation (2) from equation (1), equation (3) is obtained.
B1-B2 = (B11 + B13)-(-B12 + B14) = B11 + B12 (3)
As a result, the influence of the magnetic flux density B13 and the magnetic flux density B14 caused by the other-phase current Ib2 is eliminated, and an output voltage proportional to the sum of the magnetic flux density B11 and the magnetic flux density B12 is detected. Also, the output voltage detection sensitivity is doubled.

  Note that either one of the Hall elements 14 and 15 has a magnetic flux detection surface in the opposite direction, the output voltage of one Hall element is reversed in the positive and negative directions, and two outputs amplified by the differential amplifiers 70 and 71 in the differential amplifier 72. The same effect can be obtained by adding the voltages.

  As described above, the two magnetic cores are disposed so as to surround the conductor through which the current flows and to have the respective air gap portions at opposite positions in the magnetic path formed by the electric current, and to be arranged in each air gap portion. In addition, each magnetic flux detection element and a detection circuit unit that calculates the value of the current by adding or subtracting the output signal of each magnetic flux detection element, the influence of the magnetic field from the other-phase current Ib2 is eliminated, The self-phase current Ib1 that is the current to be measured can be accurately detected.

Embodiment 2. FIG.
FIG. 3 is a circuit diagram of a current detection device showing Embodiment 2 of the present invention. In FIG. 3, the configuration of the detection circuit unit 61 is different from that of the first embodiment. In FIG. 3, the same reference numerals as those in FIGS. 1 and 2 are the same or equivalent, and this is common throughout the entire specification. Further, the description of the constituent elements appearing in the whole specification is merely an example, and is not limited to these descriptions. In the second embodiment, the effect of the magnetic field from the other-phase current Ib2 can be almost eliminated by adjusting the gain of the differential amplifier 73 or the differential amplifier 74 of the detection circuit unit 61.

The detection circuit unit 61 includes a current supply unit 30 including two current supply sources 21 and 22 that are driven by the Hall elements 14 and 15 that are the magnetic flux detection elements, and the Hall elements 14 and 15 that are the magnetic flux detection elements. Two differential amplifiers 73 and 74 that differentially amplify the output voltage, and a differential amplifier 75 that is an arithmetic unit that adds or subtracts each output voltage differentially amplified by the two differential amplifiers 73 and 74. It is configured.

  The Hall element 14 is driven by the Hall element drive current Ih01 supplied from the current supply source 21, and outputs a voltage proportional to the magnetic flux density generated by the current flowing through the first bus bar 3. The hall element 15 is driven by the hall element drive current Ih02 supplied from the current supply source 22, and outputs a voltage proportional to the magnetic flux density generated by the current flowing through the first bus bar 3. Ih01 and Ih02 are equivalent current values. The magnitude of the current flowing through the first bus bar 3 is proportional to the magnetic flux density detected by the Hall elements 14 and 15. The output voltage of the Hall element 14 is amplified by the differential amplifier 73, and the output voltage of the Hall element 15 is amplified by the differential amplifier 74. The differential amplifier 73 is composed of operational amplifiers AP701 and AP702 and resistors R731, R732, and R733, and the differential amplifier 74 is composed of operational amplifiers AP711, AP712, and resistors R741, R742, and R743.

  The two output voltages amplified by the differential amplifiers 73 and 74 are subtracted by the differential amplifier 75 and output as detection voltage signals proportional to the magnitude of the current flowing through the first bus bar 3. The differential amplifier 75 includes an operational amplifier AP721 and resistors R751, R752, R753, R754, R755, and R756. The operational amplifier AP721 may be the same as the operational amplifier AP72. The detection voltage signal is processed by a control circuit unit configured by a microcomputer or the like (not shown).

  In the differential amplifiers 73 and 74 of the detection circuit unit 61 configured in this way, the values of resistors other than the resistors R732 and R742 can be made the same. Further, the gain of the differential amplifier 73 that amplifies the output voltage of the Hall element 14 can be changed by changing only the resistor R732. That is, the differential amplifier has a gain adjustment function. When the differential amplifiers 70 and 71 in the first embodiment are used, it is necessary to adjust at least two resistors such as the resistor R703 and the resistor R704 when adjusting the gain of the differential amplifier 70. On the other hand, in the present embodiment, only one resistor R732 needs to be adjusted. Similarly, the gain of the differential amplifier that amplifies the output voltage of the Hall element 15 can be changed by changing only the resistor R742. To change the resistance, the resistance value may be changed by a variable resistor, or the resistance value may be changed by changing a fixed resistance.

The reason why the gains of the differential amplifiers 73 and 74 need to be adjusted will be described. In the first embodiment, in order to remove the influence of the magnetic field from the other-phase current Ib2, it is necessary that the characteristics of the Hall elements 14 and 15 are equal. However, there are variations in characteristics of the Hall elements, and variations occur in the product sensitivity of the Hall elements 14 and 15. The output voltages of the respective Hall elements 14 and 15 can be expressed as Expressions (4) and (5) using the Hall element product sensitivity and the Hall element drive current.
Vh1 = Kh1 × Ih01 × B1 (4)
Vh2 = Kh2 × Ih02 × B2 (5)
Here, Kh1 is the product sensitivity of the Hall element 14, Kh2 is the product sensitivity of the Hall element 15, Ih01 is the drive current of the Hall element 14, Ih02 is the drive current of the Hall element 15, Vh1 is the output voltage of the Hall element 14, and Vh2 is This is the output voltage of the Hall element 15.

  Even if the drive currents Ih01 and Ih02 of the hall elements 14 and 15 have the same value, if there is a variation in the product sensitivities Kh1 and Kh2 of the hall elements 14 and 15, Variations occur in the output voltages Vh1 and Vh2. For this reason, the product sensitivity of the Hall element 14 and the product sensitivity of the Hall element 15 can be apparently made equal by adjusting the gain of the differential amplifier 73 by adjusting the resistor R732 at the time of shipment. As a result, since the magnetic flux density B13 and the magnetic flux density B14 generated by the other phase current Ib2 can be detected as the same value, the differential amplifier 75 subtracts the magnetic flux density B13 and the magnetic flux density B14 from the other phase current Ib2. The influence of the magnetic field can be removed. Further, the same effect can be obtained by adjusting the gain of the differential amplifier 74 by adjusting the resistor R742.

  As described above, since the differential amplifier has a gain adjustment function, variations in output voltage due to variations in sensitivity of the Hall elements can be suppressed.

Embodiment 3 FIG.
FIG. 4 is a configuration diagram of a current supply source of the Hall element according to the third embodiment of the present invention. In FIG. 4, the configuration of the current supply source 23 is different from that of the first embodiment. Further, in the present embodiment, the gain adjustment method when there is variation in the product sensitivity of the Hall elements is different from that of the second embodiment. In the third embodiment, the influence of the magnetic field from the other-phase current can be almost eliminated by adjusting the current value supplied to the Hall element.

In FIG. 4, the current supply source 23 is included in a current supply unit (not shown), and includes a microcomputer 80, an operational amplifier AP801, a transistor Tr801, and a resistor R801. The analog output terminal of the microcomputer 80 is connected to the non-inverting input terminal of the operational amplifier AP801. Here, the current supply source 23 supplies a current to the Hall element 14. The drive current Ih01 of the Hall element 14 obtained from the current supply source 23 by the analog output voltage of the microcomputer 80 is as shown in Expression (6).
Ih01 = Vh01 / R801 (6)
Here, Vh01 is an analog output voltage of the microcomputer 80. That is, the Hall element drive current Ih01 can be adjusted by adjusting the analog output voltage Vh01 of the microcomputer 80. That is, the current supply source 23 has a function of adjusting a current value supplied to the Hall element 14 that is a magnetic flux detection element. A current supply source 23 is provided in at least one of the two current supply sources of the detection circuit unit. That is, the current supply source 23 may be used to supply current to the Hall element 14, the current supply source 23 may be used to supply current to the Hall element 15, and the Hall element 14 and Hall element The current supply source 23 may be used individually to supply the current to 15.

The necessity of adjusting the drive current of the Hall element 14 or the Hall element 15 is as follows. Even if the drive currents Ih01 and Ih02 of the hall elements 14 and 15 have the same value, if there is variation in the product sensitivities Kh1 and Kh2 of the hall elements 14 and 15, the hall elements 14 and 15 have different values. , 15 also have variations in the output voltages Vh1, Vh2. The relationship between the output voltages Vh1 and Vh2 of the respective Hall elements 14 and 15 and the product sensitivities Kh1 and Kh2 is equivalent to the expressions (4) and (5). For this reason, as shown in equation (7),
Kh1 × Ih01 = Kh2 × Ih02 (7)
By adjusting the Hall element drive current Ih01 so as to satisfy the relationship, the characteristics of the output voltages Vh1 and Vh2 of the Hall elements with respect to the magnetic flux density can be made the same. As a result, since the magnetic flux density B13 and the magnetic flux density B14 generated by the other phase current Ib2 can be detected as the same value, the differential amplifier 72 subtracts the magnetic flux density B13 and the magnetic flux density B14 from the other phase current Ib2. The influence of the magnetic field can be removed.

  Next, a method for adjusting Ih01 when the current supply source 23 is used will be described. The analog of the microcomputer 80 is set such that the other-phase current Ib2 is zero, the current is supplied only to the self-phase current Ib1, and the drive currents Ih01 in which the magnitudes of the output voltages of the Hall elements 14 and 15 are equal are opposite to each other. The output voltage Vh01 is adjusted. The same applies to the adjustment of the drive current Ih02. In the present embodiment, it is not necessary to change the resistance value as in the second embodiment.

  As described above, since at least one of the two current supply sources has a function of adjusting the current value supplied to the magnetic flux detection element, variation in output voltage due to variation in sensitivity of the Hall element can be suppressed. .

Embodiment 4 FIG.
FIG. 5 is a circuit diagram of a current detection device showing Embodiment 4 of the present invention. In FIG. 5, the configuration of the current supply unit 31 is different from that of the first embodiment. In the fourth embodiment, a constant current source is used to drive the Hall element, and the influence of the magnetic field from the other phase current can be eliminated without performing gain adjustment or current value adjustment.

  The detection circuit unit 62 includes a current supply unit 31 including one current supply source 24 that drives the Hall elements 14 and 15 that are magnetic flux detection elements connected in parallel, and the Hall element 14 that is a magnetic flux detection element. Differential amplifiers 70 and 71 for differentially amplifying the output voltages of 15 and 15, and a differential amplifier which is an arithmetic unit for adding or subtracting the respective output voltages differentially amplified by the two differential amplifiers 70 and 71 72. In the current drive configuration of the Hall element in the fourth embodiment, the Hall elements 14 and 15 connected in parallel are driven by the current supply source 24 which is a single current source. As a result, it is possible to suppress variations in the output voltages of the Hall elements 14 and 15 due to variations in product sensitivity of the Hall elements 14 and 15.

The product sensitivity of the Hall element is related to the input resistance of the Hall element. When the input resistance of the Hall element is large, the product sensitivity of the Hall element increases. The input resistance of the Hall element is a resistance between an input and an output of a current that drives the Hall element. The relationship between the product sensitivity of the Hall element and the input resistance of the Hall element can be expressed as Equation (8) when the specific sensitivity of the Hall element is used.
K * = Vh / (Rin × Ih × B) (8)
Here, K * is the Hall element specific sensitivity, Rin is the Hall element input resistance, Ih is the Hall element drive current, B is the Hall element magnetic flux density, and Vh is the Hall element output voltage. The output voltage Vh of the Hall element can be expressed as in Expression (8) to Expression (9).
Vh = K * × Rin × Ih × B (9)
The relationship between the output voltage Vh of the Hall element and the product sensitivity Kh of the Hall element can be expressed as Expression (10).
Vh = Kh × Ih × B (10)
From Equations (9) and (10), a relationship such as Equation (11) is obtained, and it can be seen that the product sensitivity of the Hall element is proportional to the input resistance of the Hall element.
Kh = K * × Rin (11)

Using the Hall element specific sensitivity K *, the output voltages Vh1 and Vh2 of the Hall elements 14 and 15 can be expressed by Expression (12) and Expression (13) from Expression (9), respectively.
Vh1 = K * × Rin1 × Ih01 × B1 (12)
Vh2 = K * × Rin2 × Ih02 × B2 (13)
Here, Rin1 is the input resistance of the Hall element 14, and Rin2 is the input resistance of the Hall element 15.

The reason why variations in the output voltages Vh1 and Vh2 of the Hall elements 14 and 15 can be suppressed is as follows. The currents flowing through the respective Hall elements 14 and 15 are determined by the input resistances Rin1 and Rin2 of the respective Hall elements 14 and 15, and have a relationship as shown in Expression (14) and Expression (15).
Ih01 × Rin1 = Ih02 × Rin2 (14)
Ih01 + Ih02 = Ih0 (15)
In addition, the drive currents Ih01 and Ih02 to the respective Hall elements 14 and 15 can be expressed as in Expression (16) and Expression (17).
Ih01 = (Rin2 / (Rin1 + Rin2)) × Ih0 (16)
Ih02 = (Rin1 / (Rin1 + Rin2)) × Ih0 (17)
By substituting the relationship of the equations (16) and (17) into the terms of the drive currents Ih01 and Ih02 of the equations (12) and (13), The output voltages Vh1 and Vh2 of the Hall elements 14 and 15 can be expressed as Expressions (18) and (19).
Vh1 = K * × Ih0 × (Rin1 × Rin2 / (Rin1 + Rin2)) × B1 (18)
Vh2 = K * × Ih0 × (Rin1 × Rin2 / (Rin1 + Rin2)) × B2 (19)

  Comparing equation (18) and equation (19), the output voltage of the hall element changes depending on the magnetic flux density, so the characteristics of the output voltage of the hall element with respect to the magnetic flux density in each of the hall elements 14 and 15 are the same. Can be. As a result, since the magnetic flux density B13 and the magnetic flux density B14 generated by the other phase current Ib2 can be detected as the same value, the differential amplifier 72 subtracts the magnetic flux density B13 and the magnetic flux density B14 from the other phase current Ib2. The influence of the magnetic field can be removed.

As described above, one current supply source that drives each magnetic flux detection element connected in parallel;
Two differential amplifiers that differentially amplify the output voltage of each magnetic flux detection element, and a differential amplifier that is an arithmetic unit that adds or subtracts each output voltage differentially amplified by the two differential amplifiers. Therefore, variation in output voltage due to variation in sensitivity of the Hall element can be suppressed.

Embodiment 5. FIG.
FIG. 6 is a configuration diagram of a current supply source of the Hall element according to the fifth embodiment of the present invention. In FIG. 6, the configuration of the current supply unit 32 is different from that of the first embodiment. In FIG. 6, the current supply unit 32 includes a constant voltage source 25 having a function equivalent to that of the constant current source. The constant voltage source 25 is one current supply source that drives the Hall elements 14 and 15 that are magnetic flux detection elements connected in parallel.

When the constant voltage source 25 is used, the drive currents Ih01 and Ih02 to the Hall elements 14 and 15 are expressed by the equations (20) and (21) due to the input resistance of the Hall elements 14 and 15, respectively. Can be represented.
Ih01 = Vh0 / Rin1 (20)
Ih02 = Vh0 / Rin2 (21)
Here, Vh0 is a voltage supplied from the constant voltage source 25. By substituting the relations of the equations (20) and (21) into the terms of the drive currents Ih01 and Ih02 in the equations (12) and (13), the output voltages Vh1 and Vh2 of the respective Hall elements 14 and 15 are given by the equations (22) and can be expressed as in equation (23).
Vh1 = K * × Vh0 × B1 (22)
Vh2 = K * × Vh0 × B2 (23)

  Comparing equation (22) and equation (23), the output voltage of the hall element changes depending on the magnetic flux density, so the characteristics of the output voltage of the hall element with respect to the magnetic flux density in each of the hall elements 14 and 15 are the same. Can be. As a result, the magnetic flux density B13 and the magnetic flux density B14 generated by the other-phase current Ib2 can be detected as the same value. Therefore, by subtracting the magnetic flux density B13 and the magnetic flux density B14 in the differential amplifier 72, The influence of the magnetic field can be removed.

As described above, one current supply source that drives each magnetic flux detection element connected in parallel;
Two differential amplifiers that differentially amplify the output voltage of each magnetic flux detection element, and a differential amplifier that is an arithmetic unit that adds or subtracts each output voltage differentially amplified by the two differential amplifiers. Therefore, variation in output voltage due to variation in sensitivity of the Hall element can be suppressed.

  In all of the embodiments, each of the embodiments of the present invention can be applied to the case where the second bus bar has a current detection device and the other bus bars arranged in parallel have the current detection device. The current flowing through the bus bar can be accurately detected.

It is a block diagram of the magnetic flux detection part of the electric current detection apparatus which shows Embodiment 1 of this invention. 1 is a circuit diagram of a current detection device in Embodiment 1 of the present invention. It is a circuit diagram of the electric current detection apparatus which shows Embodiment 2 of this invention. It is a block diagram of the electric current supply source of the Hall element which shows Embodiment 3 of this invention. It is a circuit diagram of the electric current detection apparatus which shows Embodiment 4 of this invention. It is a block diagram of the electric current supply source of the Hall element which shows Embodiment 5 of this invention.

Explanation of symbols

  2 circuit board, 3 first bus bar, 4 second bus bar, 10 upper magnetic core, 11 lower magnetic core, 12, 13 gap, 14, 15 Hall element, 21-24 current supply source, 25 Constant voltage source, 30 to 32 current supply unit, 50 magnetic flux detection unit, 60 to 62 detection circuit unit, 70 to 75 differential amplifier, 80 microcomputer, AP70 to AP72, AP701, AP702, AP711, AP712, AP721, operational amplifier, R701 to R704, R711 to R714, R721 to R724, R731 to R733, R741 to R743, R751 to R756, R801 resistors, Tr801 transistors.

Claims (6)

Two magnetic cores that surround a conductor through which a current flows and are arranged to have respective air gaps at opposite positions in a magnetic path formed by the current;
Each magnetic flux detecting element disposed in each of the gaps;
A current detection apparatus comprising: a detection circuit unit that calculates the value of the current by adding or subtracting output signals of the respective magnetic flux detection elements. 2. The current detection device according to claim 1, wherein the size of each gap is made equal. The detection circuit unit includes two current supply sources that drive each magnetic flux detection element,
Two differential amplifiers for differentially amplifying the output voltage of each of the magnetic flux detection elements;
The current detection device according to claim 1, further comprising: an arithmetic unit that adds or subtracts each output voltage differentially amplified by the two differential amplifiers. 4. The current detection device according to claim 3, wherein the differential amplifier has a gain adjustment function. The current detection device according to claim 3, wherein at least one of the two current supply sources has a function of adjusting a current value supplied to the magnetic flux detection element. The detection circuit unit includes one current supply source that drives each magnetic flux detection element connected in parallel;
Two differential amplifiers for differentially amplifying the output voltage of each of the magnetic flux detection elements;
The current detection device according to claim 1, further comprising: an arithmetic unit that adds or subtracts each output voltage differentially amplified by the two differential amplifiers.

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