JP2015121423A - Current detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of accuracy in detecting a level of current flowing through each conductor.SOLUTION: A current detection device 20 includes; Hall elements 21, 22 which generate analog signals V_a, V_b corresponding to magnetic fluxes generated by currents flowing through two conductors 13, 14, respectively; and amplifier circuits 23-26 which output analog signals V_aK1, V_aK2, V_bK3, V_bK4, respectively, obtained by amplifying either of the analog signals V_a, V_b with respective gains K1-K2. The current detection device 20 also includes analog arithmetic circuits 27, 28 which output analog signals Out_a, Out_b, respectively, obtained by adding respective analog signals V_aK1, V_aK2, V_bK3, V_bK4 generated by the amplifier circuits 23-26.

Description

  The present invention relates to a current detection device.

  Conventionally, as a current detection device that detects values of currents flowing through a plurality of conductors (bus bars) by using a Hall element that outputs a voltage corresponding to a magnetic flux density, for example, there is a current detection device described in Patent Document 1. . In the current detection device of Patent Document 1, a technique that does not require a magnetic core is employed. Specifically, a coefficient indicating the relationship between the current flowing through each conductor and the voltage output by the Hall element as a magnetic sensor is acquired in advance, and the value of each current flowing through each conductor based on the coefficient is obtained from a microcomputer or the like. Calculated by the signal processing circuit.

JP 2008-58035 A

  However, in the current detection device of Patent Document 1, since the value of the current flowing through each conductor is calculated by the signal processing circuit based on the voltage output from the Hall element and the coefficient acquired in advance, calculation processing time is required. become. Then, if such a calculation processing time is not sufficient, when a fast response speed is required for detection of the value of the current flowing through each conductor, the detection accuracy of such a current value is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a current detection device capable of suppressing a decrease in detection accuracy of a value of a current flowing through each conductor.

  A current detection device that solves the above problem is a current detection device that can detect the values of currents flowing through a plurality of conductors, respectively, and a voltage value corresponding to a magnetic flux generated by a current flowing through each conductor. A magnetic sensor that outputs an analog signal, an amplifier circuit that outputs a second analog signal obtained by amplifying the first analog signal output from the magnetic sensor at a predetermined amplification factor, and a second analog signal output from the amplifier circuit are calculated. And an analog arithmetic circuit that outputs the third analog signal that can calculate the current flowing through the corresponding conductor in association with each conductor.

  According to this configuration, the analog signal is used as it is, and a series of processes such as amplification of the first analog signal output from the magnetic sensor and output of the third analog signal are performed as a result of the subsequent calculation of the second analog signal. Thus, calculation by a signal processing circuit such as a microcomputer is not necessary. This eliminates the need for calculation processing time by the signal processing circuit. Therefore, it is possible to cope with a fast response speed in detecting the value of the current flowing through each conductor without considering the calculation processing time, and it is possible to suppress a decrease in detection accuracy of the value of the current flowing through each conductor. .

  In such a current detection device, as a method for detecting the value of the current flowing through each conductor, the magnetic sensor has a method including a plurality of detection elements provided with a part or all of the plurality of conductors as detection targets. is there. Further, as such a technique, the amplifier circuit outputs the second analog signal amplified by the amplification factor determined so that the first analog signal output from each detection element becomes a component corresponding to the conductor to be detected. There is a method of making each output possible. Further, as such a technique, there is a technique in which the analog arithmetic circuit is configured to be able to output the third analog signal calculated for each component corresponding to the conductor whose detection target is the second analog signal output from the amplifier circuit. is there. According to these, since the value of the current flowing through each conductor can be detected without using the signal processing circuit, the configuration of the current detection device is simplified and the cost is reduced.

  Further, in such a current detection device, as a method for determining the amplification factor, the amplification factor is determined by using the relationship between the first analog signal output from each detection element and the magnetic flux density based on the conductor to be detected. There is a method of setting each proportional constant when the current of each conductor detected by the detection element is the sum proportional to the first analog signal output by each detection element. According to this, since the output equivalent to the value of the current flowing through each conductor such as the third analog signal can be obtained without using the signal processing circuit, the configuration of the current detection device is simplified and the cost is reduced. Contributes to reduction.

  In such a current detection device, the amplification factor is obtained from the theoretical value obtained as the respective proportionality constant in the sum proportional to the first analog signal output from each detection element and the second analog signal at the theoretical value. It is preferable to adjust the value obtained from the actual measurement value using the relationship with the actual measurement value.

  Each proportionality constant in the sum proportional to the first analog signal output by each detection element is positioned as a theoretical value for calculation. On the other hand, each detection element actually used in the current detection device generally has individual differences in the relationship between the magnetic flux to be detected and the output voltage. Therefore, the theoretical value is adjusted using the relationship with the actual measurement value actually obtained from the second analog signal. As a result, individual differences in the relationship between the magnetic flux detected by each detection element and the output voltage can be absorbed, and the value of the current flowing through each conductor such as the third analog signal can be obtained without using the signal processing circuit. Equivalent output can be obtained with high accuracy.

  Further, in such a current detection device, each detection element is two provided with detection of two specific conductors among the three conductors corresponding to each phase of the three-phase alternating current, and the amplification circuit Are each provided to amplify the first analog signals output from the two detection elements at a predetermined amplification factor so as to be components corresponding to two specific conductors to be detected. The analog arithmetic circuit is composed of two pieces that are provided so as to add the second analog signal output by the two amplification circuits for each component corresponding to the conductor to be detected. It is preferable to further include a shielding shield that covers the detection element together with two specific conductors and shields the influence of an external magnetic flux.

  According to this configuration, it is possible to first detect the value of the current flowing through two specific conductors. As for the value of the current flowing in the remaining one conductor, two specific currents are utilized by utilizing the fact that the sum of the current flowing in each conductor is “0 (zero)”, which is a characteristic of the three-phase alternating current. It is obtained from the detection result of the value of the current flowing through the conductor. In particular, for the two detection elements, the influence of the magnetic flux generated by the current flowing through the remaining one conductor can be ignored by covering the two detection elements together with the specific two conductors with a shielding shield. As a result, the magnetic flux generated by the current flowing in the specific two conductors can be detected more greatly, and the detection accuracy of the value of the current flowing in each conductor can be improved.

  According to the present invention, it is possible to suppress a decrease in detection accuracy of the value of the current flowing through each conductor.

The figure which shows schematic structure of a motor drive device. The figure which shows schematic structure of an electric current detection apparatus.

Hereinafter, an embodiment of the current detection device will be described.
A motor drive device 10 shown in FIG. 1 is mounted on a vehicle or the like, and converts DC power supplied from a battery 11 into three-phase (U-phase, V-phase, W-phase) AC power used for driving the motor. An inverter 12 is provided. The inverter 12 is connected to the motor 16 via rod-shaped first to third conductors 13 to 15 made of a conductive material such as copper. The first to third conductors 13 to 15 supply the AC power of each phase converted by the inverter 12 to the motor 16. The first conductor 13 supplies AC power for the U phase, the second conductor 14 for V phase, and the third conductor 15 for W phase.

  In addition, the motor driving device 10 includes a control device 17 that outputs a command signal for controlling the power supply of the inverter 12. The command signal output from the control device 17 commands the on / off state of each switching element constituting the inverter 12. And the control apparatus 17 controls the drive of the motor 16 by outputting a command signal.

  In addition, the motor drive device 10 includes a current detection device 20 that outputs an analog signal (voltage signal) corresponding to the value (current value) of the current flowing through the first conductor 13 and the second conductor 14. The control device 17 receives analog signals Out_a and Out_b as third analog signals output from the current detection device 20, and controls driving of the motor 16 based on the analog signals Out_a and Out_b.

Next, the configuration of the current detection device 20 will be described.
As shown in FIG. 2, the current detection device 20 includes a Hall element (two) that outputs an analog signal (voltage signal) corresponding to a magnetic flux density (magnetic flux), and an amplifier circuit (four) that inputs and outputs the analog signal. And an analog arithmetic circuit (two) for inputting / outputting analog signals is a Hall IC provided as one package.

  Specifically, the current detection device 20 includes a plurality of (two in this embodiment) first Hall elements 21 and second Hall elements 22 as magnetic sensors (detection elements). The first hall element 21 receives an analog signal V_a as a first analog signal output from the hall element 21 and amplifies the analog signal V_a with a predetermined amplification factor (two in this embodiment). The first amplifier circuit 23 and the second amplifier circuit 24 are connected.

  Each amplifier circuit 23, 24 amplifies the analog signal V_a with amplification factors K1, K2 respectively determined. The first amplifier circuit 23 outputs (generates) the analog signal V_aK1 as the second analog signal. The second amplifier circuit 24 outputs (generates) an analog signal V_aK2 as the second analog signal.

  The second hall element 22 receives an analog signal V_b as the first analog signal output from the hall element 22 and amplifies the analog signal V_b at a predetermined amplification factor (in this embodiment, 2). ) Third amplifier circuit 25 and fourth amplifier circuit 26 are connected.

  Each amplifier circuit 25, 26 amplifies the analog signal V_b with amplification factors K3, K4 respectively determined. Then, the third amplifier circuit 25 outputs (generates) an analog signal V_bK3 as the second analog signal. The fourth amplifier circuit 26 outputs (generates) an analog signal V_bK4 as the second analog signal.

In the present embodiment, two amplifying circuits are connected to each Hall element 21, 22. In addition, each of the amplifier circuits 23 to 26 is configured to be able to vary the amplification factor by varying the input resistance.
The first amplifier circuit 23 and the third amplifier circuit 25 receive the analog signal V_aK1 output from the first amplifier circuit 23 and the analog signal V_bK3 output from the third amplifier circuit 25, and add them in an analog manner. The first analog arithmetic circuit 27 is connected. Note that the analog addition is realized by, for example, a configuration in which each analog signal (voltage signal) is input via a resistor.

  The first analog arithmetic circuit 27 adds the analog signal V_aK1 proportional to the analog signal V_a output from the first Hall element 21 and the analog signal V_bK3 proportional to the analog signal V_b output from the second Hall element 22. Then, the first analog arithmetic circuit 27 outputs (generates) an analog signal Out_a as a third analog signal.

  In addition, the analog signal V_aK2 output from the second amplifier circuit 24 and the analog signal V_bK4 output from the fourth amplifier circuit 26 are input to the second amplifier circuit 24 and the fourth amplifier circuit 26, and these are added in an analog manner. The second analog arithmetic circuit 28 is connected.

  The second analog arithmetic circuit 28 adds the analog signal V_aK2 proportional to the analog signal V_a output from the first Hall element 21 and the analog signal V_bK4 proportional to the analog signal V_b output from the second Hall element 22. Then, the second analog arithmetic circuit 28 outputs (generates) an analog signal Out_b as a third analog signal.

  Further, as shown in FIG. 2, the current detection device 20 faces the adjacent first conductor 13 and second conductor 14 among the three conductors 13 to 15 arranged in parallel in the longitudinal direction. Is mounted on the motor driving device 10. Further, when the current detection device 20 is mounted on the motor drive device 10, the first Hall element 21 faces the first conductor 13, while the second Hall element 22 faces the second conductor 14. The hall elements 21 and 22 are spaced apart.

  Further, the motor drive device 10 includes a shielding shield made of a ferromagnetic material such as iron or ferrite that shields the influence of magnetic flux from outside inside. The shielding shield 30 covers the current detection device 20 together with the first conductor 13 and the second conductor 14. For this reason, each Hall element 21, 22 of the current detection device 20 is affected by the magnetic flux generated by the current flowing in the first conductor 13 and the second conductor 14 that are both covered by the shield shield 30 in the motor driving device 10. On the other hand, each Hall element 21, 22 is not affected by the magnetic flux generated by the current flowing through the third conductor 15 (shown by a broken line in FIG. 2) outside the shield shield 30 in the motor drive device 10, but was temporarily affected. However, it is negligible for detection of the current value.

  As described above, the current detection device 20 outputs information indicating a current value by detecting two specific conductors such as the first conductor 13 and the second conductor 14 among the three conductors 13 to 15. . The current detection device 20 outputs an analog signal Out_a as information indicating a current value flowing through the first conductor 13 and outputs an analog signal Out_b as information indicating a current value flowing through the second conductor 14.

  The analog signals Out_a and Out_b output in this way are voltage signals corresponding to the conductors to be detected. For this reason, these analog signals Out_a and Out_b are converted into current values based on the rated current values and the rated voltage values of the motor drive device 10, thereby indicating the current values flowing through the conductors to be detected. Then, the control device 17 receives the analog signal Out_a, converts it into a current value, and acquires information indicating the current value flowing through the first conductor 13 to be detected. Further, the control device 17 receives the analog signal Out_b, converts it into a current value, and acquires information indicating the current value flowing through the second conductor 14 to be detected.

  Further, when the current value flowing through the first conductor 13 is “Ia”, the current value flowing through the second conductor 14 is “Ib”, and the current value flowing through the third conductor 15 is “Ic”, the current is supplied by the motor driving device 10. In the three-phase AC power that is generated, the relationship of Expression (1) in which the sum of the currents flowing through the conductors is “0 (zero)” between the current values is shown.

Ia + Ib + Ic = 0 (1)
That is, the control device 17 converts the information indicating the current value flowing through the remaining third conductor 15 that is not detected by the current detection device 20 from the information indicating the current value acquired by the analog signals Out_a and Out_b into a three-phase alternating current. It acquires using the relationship of Formula (1) in electric power.

Next, the amplification factors K1 to K4 in the amplifier circuits 23 to 26 will be described.
In general, the magnetic flux density B of the magnetic flux generated by the current having the current value I flowing through the rod-shaped conductor has the relationship of the formula (2) with the distance r from the center of each conductor.

B = μ0 / (2π) × I / r (2)
In Expression (2), “μ0” is magnetic permeability.
As shown in FIG. 2, the first Hall element 21 is arranged at a distance r1 from the first conductor 13 (center) and a distance r2 from the second conductor 14 (center). The second Hall element 22 is arranged at a distance r3 from the first conductor 13 (center) and a distance r4 from the second conductor 14 (center).

  The analog signals V_a and V_b output from the hall elements 21 and 22 are proportional to the magnetic flux density B generated by the current flowing through the conductors 13 and 14. Further, the magnetic flux density B is proportional to the current value I generating the magnetic flux density B from the relationship of the formula (2).

Therefore, the analog signals V_a and V_b output from the hall elements 21 and 22 show the relations of the expressions (3) and (4) with the current values Ia and Ib flowing through the conductors 13 and 14, respectively.
V_a = R1 × Ia + R2 × Ib (3)
V_b = R3 × Ia + R4 × Ib (4)
In the equations (3) and (4), “R1” is a constant proportional to “1 / r1”, “R2” is a constant proportional to “1 / r2”, and “R3” is proportional to “1 / r3”. “R4” is a constant proportional to “1 / r4”.

  Then, when “Ib” is deleted from the equations (3) and (4) and rearranged, the relationship of the equation (5) is shown between the current value Ia and the analog signals V_a and V_b.

Further, when “Ia” is deleted from the equations (3) and (4) and rearranged, the relationship of the equation (6) is shown between the current value Ib and the analog signals V_a and V_b.

In other words, the equations (5) and (6) are obtained from the analog signals V_a, which are output from the hall elements 21 and 22, respectively, as the current values Ia and Ib flowing through the conductors 13 and 14 to be detected by the hall elements 21 and 22. The relationship as a sum proportional to V_b is shown.

  As shown in FIG. 2, the analog signals Out_a and Out_b output from the current detection device 20 are expressed between the analog signals V_a and V_b using the amplification factors K1 to K4 of the amplification circuits 23 to 26, respectively. The relationship of (7) and Formula (8) is shown.

Out_a = K1 × V_a + K3 × V_b (7)
Out_b = K2 × V_a + K4 × V_b (8)
That is, as shown in the equations (7) and (8), the respective amplification circuits 23 to 26 output the respective hall elements 21 and 22 so as to become components corresponding to the detected conductors 13 and 14. That is, the analog signals V_a and V_b are amplified at the amplification factors determined for each. Further, as shown in Expression (7) and Expression (8), the analog arithmetic circuits 27 and 28 detect the analog signals V_aK1, V_aK2, V_bK3, and V_bK4 output from the amplifier circuits 23 to 26, respectively. The addition is performed for each component corresponding to the conductors 13 and 14.

  Then, when the formula (5) is compared with the formula (7), the amplification factors K1 and K3 show the relationship of the formula (9) between the constants R1 to R4.

Further, when Expression (6) is compared with Expression (8), the amplification factors K2 and K4 show the relationship of Expression (10) between the constants R1 to R4.

That is, the amplification factors K1 to K4 of the amplification circuits 23 to 26 are proportional constants in the equations (5) and (6). As described above, since the analog signals Out_a and Out_b are voltage signals corresponding to the conductors to be detected, the amplification factors K1 to K4 are related to the constants R1 to R4 (equations (9) and (9)). The right side of (10) is multiplied by a constant based on each rated value of the motor drive device 10.

  Then, in the equations (9) and (10), each of the amplifications to be determined is substituted by substituting constants R1 to R4 based on the distances r1 to r4 between the conductors 13 and 14 and the hall elements 21 and 22, respectively. The rates K1 to K4 are obtained. The amplification factors K1 to K4 determined in this way are positioned as theoretical values in calculation.

  Therefore, the theoretical values calculated for the amplification factors K1 to K4 obtained so far are set in the amplification circuits 23 to 26, and the current signals are detected by actually detecting the analog signals V_aK1, V_aK2, V_bK3, and V_bK4. Errors such as detection errors of the Hall elements 21 and 22 and setting errors of the distances r1 to r4 in the apparatus 20 can be adjusted.

Hereinafter, adjustment of the errors of the amplification factors K1 to K4 in each of the amplifier circuits 23 to 26 will be described.
As shown in FIG. 2, the actual measurement value S <b> 1 for the analog signal V_aK <b> 1 is detected by connecting the terminal P <b> 1 between the connections of the first amplifier circuit 23 and the first analog arithmetic circuit 27. In addition, the actual measurement value S2 for the analog signal V_aK2 is detected by connecting the terminal P2 between the connections of the second amplifier circuit 24 and the second analog arithmetic circuit 28. The actual measurement value S3 for the analog signal V_bK3 is detected by connecting the terminal P3 between the connections of the third amplifier circuit 25 and the first analog arithmetic circuit 27. Further, the actual measurement value S4 for the analog signal V_bK4 is detected by connecting the terminal P4 between the connections of the fourth amplifier circuit 26 and the second analog arithmetic circuit 28.

  The actually measured values S1 to S4 detected are equivalent to the values obtained by amplifying the analog signals V_a and V_b with the corresponding amplification factors K1 to K4, and by using the equations (3) and (4). The current values Ia and Ib can be replaced.

In other words, the actual measurement value S1 and the actual measurement value S3 related to the analog signal Out_a show the relationship of the equations (11) and (12).
S1 = K1 × V_a = K1 × (R1 × Ia + R2 × Ib) (11)
S3 = K3 × V_b = K3 × (R3 × Ia + R4 × Ib) (12)
Further, regarding the actual measurement value S2 and the actual measurement value S4 related to the analog signal Out_b, the relationship of Expression (13) and Expression (14) is shown.

S2 = K2 * V_a = K2 * (R1 * Ia + R2 * Ib) (13)
S4 = K4 × V_b = K4 × (R3 × Ia + R4 × Ib) (14)
And while substituting the theoretical value in calculation of each amplification factor K1-K4 of each of Formula (11)-(14), and substituting an appropriate numerical value for each current value Ia, Ib, each constant R1-R4. Can be represented by measured values S1 to S4. Then, each amplification factor K1-K4 based on each actual measurement value S1-S4 can be calculated | required, By setting each amplification factor of each amplification circuit 23-26 to each amplification factor K1-K4 calculated | required here, The error adjustment can be completed.

Here, a case where “1” is obtained as a theoretical value for calculation of each of the amplification factors K1 to K4 will be described.
Then, for example, “100 A” is passed through the current value Ia and “0 A” is passed through the current value Ib, and the measured values S1 to S4 are detected. That is, by substituting “100 A” for the current value Ia and “0 A” for the current value Ib in the equations (11) and (12), respectively, the actual measurement value S1 and the actual measurement value S3 related to the analog signal Out_a 15) is shown.

S1 = 100 × R1, S3 = 100 × R3 (15)
Next, for example, “0A” is passed as the current value Ia and “100A” is passed as the current value Ib, and the actual measurement values S1 to S4 are detected. That is, by substituting “0A” for the current value Ia and “100A” for the current value Ib into the equations (13) and (14), respectively, the actual measurement value S2 and the actual measurement value S4 related to the analog signal Out_b The relationship of 16) is shown.

S2 = 100 × R2, S4 = 100 × R4 (16)
Then, by replacing the constants R1 to R4 in the equations (9) and (10) with the actual measurement values S1 to S4, the amplification factors K1 to K4 are expressed by the equation (17) between the actual measurement values S1 to S4 in this example. ) To (20) are shown.

Then, by setting the amplification factors K1 to K4 obtained by substituting the actually measured values S1 to S4 in this example into the equations (17) to (20), the amplification factors 23 to 26 are set as the adjusted amplification factors. , The adjustment of the error can be completed.

Next, the operation of the current detection device 20 will be described.
Using the analog signal as it is, a series of amplification of the analog signals V_a and V_b output from the Hall elements 21 and 22 and further calculation of the analog signals V_aK1, V_aK2, V_bK3, and V_bK4 as a result of the output of the analog signals Out_a and Out_b. Therefore, calculation by a signal processing circuit such as a microcomputer is not necessary. This eliminates the need for calculation processing time by the signal processing circuit.

  In order to realize this, each of the Hall elements 21 and 22 is arranged so that specific two conductors among the three conductors are targeted for detection. In addition, each of the amplifier circuits 23 to 26 amplifies the analog signals V_a and V_b output from the hall elements 21 and 22 with amplification factors K1 to K4 determined so as to be components corresponding to the conductors to be detected. The analog signals V_aK1, V_aK2, V_bK3, and V_bK4 are output. Also, each of the analog arithmetic circuits 27 and 28 outputs analog signals Out_a and Out_b calculated for each component corresponding to the conductor for which the analog signals V_aK1, V_aK2, V_bK3, and V_bK4 output from the amplifier circuits 23 to 26 are detected, respectively. Output. With this configuration, it is possible to detect the value of the current flowing through each of the conductors 13 to 15 without using the signal processing circuit.

  In order to realize this, the amplification factors K1 to K4 are related to the relationship between the analog signals V_a and V_b output from the Hall elements 21 and 22 and the magnetic flux density based on the conductor to be detected, that is, the expressions (2) to (2) to Calculate using (4). That is, the amplification factors K1 to K4 are the sums proportional to the analog signals V_a and V_b output by the Hall elements 21 and 22, respectively, that is, the current values of the conductors that are detected by the Hall elements 21 and 22; ) And the proportionality constant in equation (6). Thereby, an output equivalent to the current value flowing through each conductor such as the analog signals Out_a and Out_b can be obtained without using the signal processing circuit.

  Further, the sum proportional to the analog signals V_a and V_b output from the Hall elements 21 and 22, that is, the proportional constants in the equations (5) and (6), is merely a theoretical value for calculation. On the other hand, the Hall elements 21 and 22 actually used in the current detection device 20 generally have individual differences in the relationship between the magnetic flux to be detected and the output voltage. Therefore, the theoretical value is actually adjusted using the relationship with the actual measurement values S1 to S4 obtained from the analog signals V_aK1, V_aK2, V_bK3, and V_bK4, that is, the equations (11) to (14). Thereby, the individual difference of the relationship between the magnetic flux detected in each Hall element 21 and 22 and the output voltage can be absorbed.

  In this embodiment, it is possible to first detect the current value flowing through the two conductors 13 and 14 to be detected. And about the electric current value of the remaining one 3rd conductor 15, the electric current value which flows into each of the two conductors 13 and 14 made into the detection object using Formula (1) which is the characteristic of a three-phase alternating current is shown. Obtained from the detection result. In particular, the Hall elements 21 and 22 are covered with the shield shield 30 together with the conductors 13 and 14 to be detected by the current detection device 20, thereby affecting the influence of the magnetic flux generated by the current flowing through the remaining third conductor 15. Can be ignored. Thereby, the magnetic flux which the electric current which flows into each conductor 13 and 14 made into the detection object by the electric current detection apparatus 20 generate | occur | produces can be detected more largely.

As described above, according to the present embodiment, the following effects can be achieved.
(1) Since calculation processing time by a signal processing circuit such as a microcomputer is not required, it is possible to respond to a fast response speed for detecting the current value flowing through each conductor without considering such calculation processing time. A decrease in detection accuracy of the current value flowing through each conductor can be suppressed.

  (2) Since the detection of the current value flowing through each of the conductors 13 to 15 can be realized without using the signal processing circuit, the configuration of the current detection device 20 is simplified and the cost is reduced.

  (3) Since the output equivalent to the value of the current flowing through each of the conductors 13 and 14 to be detected, such as the analog signals Out_a and Out_b, can be obtained without using the signal processing circuit, the configuration of the current detection device 20 And contribute to cost reduction.

  (4) Since individual differences in the relationship between the detected magnetic flux and the output voltage in each Hall element 21 and 22 can be absorbed, the detection target such as the analog signals Out_a and Out_b can be obtained without using the signal processing circuit. An output equivalent to the value of the current flowing through each of the conductors 13 and 14 can be obtained with high accuracy.

  (5) Since the magnetic flux generated by the currents flowing through the conductors 13 and 14 to be detected can be detected more greatly, the detection accuracy of the current values flowing through the conductors 13 and 14 can be improved.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
When the influence of the magnetic flux generated by the current flowing through the third conductor 15 may be ignored, the shielding shield 30 may not be provided. As a case where it can be ignored in this way, for example, it is conceivable that the third conductor 15 is disposed sufficiently away from the Hall elements 21 and 22.

  The current detection device 20 may output the detection result (third analog signal) based on the magnetic flux received from each of the three conductors 13 to 15 by the Hall elements 21 and 22 without providing the shielding shield 30. . In this case, an amplifier circuit that amplifies the voltage corresponding to the magnetic flux generated by the current flowing through the third conductor 15 is added, and an analog arithmetic circuit that adds components affected by the third conductor 15 is added. do it. Further, in this case, the component of the current value Ic is added in the expressions (3) and (4), and the relationship of the current value Ic is added to the expressions (5) and (6), so that each amplification factor is You just have to decide.

  The current detection device 20 can also detect the value of the current flowing through each of the conductors 13 to 15 with the three hall elements without providing the shielding shield 30. In this case, an amplifier circuit for amplifying the voltage output from the added Hall element may be added, and the analog signals amplified by the amplifier circuit may be added by the analog arithmetic circuits 27 and 28. In this case, the voltage output from the Hall element added in Equation (3) and Equation (4) is added, and the voltage output from the Hall element added in Equation (5) and Equation (6) is added. Each amplification factor may be determined in consideration of the components.

  The number of amplifier circuits can be reduced depending on the relationship between the amplification factors K1 to K4 based on the constants R1 to R4 (distances r1 to r4). In this way, when the number of amplifier circuits is reduced, the analog arithmetic circuits 27 and 28 are mainly configured for addition, but subtraction can be mainly configured, or only one of them can be configured by subtraction.

If the gains K1 to K4 do not need to be adjusted for accuracy, the gains may not be adjusted.
Each amplification factor K1 to K4 can be determined through a method in which appropriate values are first set and adjusted while viewing actual measurement values.

The amplification factors K1 to K4 may be set to values including elements of the rated values so that the analog signals Out_a and Out_b become information indicating current values without conversion.
The current detection device 20 flows through a four-phase conductor when there are two motor drive devices that supply three-phase AC power, for example, three-phase AC power, in a plurality of motor drive devices that supply three-phase AC power. It can also be applied to current detection. In this case, according to the present embodiment, a structure may be constructed in which a current value is detected by adding a number of Hall elements equal to the number of conductors to be detected and an accompanying amplification circuit.

-Although rod shape was illustrated as a conductor, plate shape may be sufficient.
The arrangement of the Hall elements 21 and 22 may be different as long as the current of each conductor as a detection target can be detected by the current detection device 20.

The current detection device 20 is not limited to a motor drive device, and can be applied to, for example, detection of a current value required for driving an electrical load such as a generator.
In the current detection device 20, an analog arithmetic circuit is added or a connection is devised so that an analog signal is output as information indicating a current value flowing through the third conductor 15 not to be detected using the analog signals Out_a and Out_b. You may do it.

  The current detection device 20 may be configured by a Hall IC having a Hall element and an amplifier circuit as one package, and an analog arithmetic circuit. In addition, the current detection device 20 may be a Hall IC in which one Hall element and two amplifier circuits are combined into one package, or one Hall element and one amplifier circuit are combined. One packaged Hall IC can also be used.

  K1 to K4 ... amplification factor, 13 to 15 ... conductor, 20 ... current detection device, 21 and 22 ... Hall element (magnetic sensor, detection element), 23 to 26 ... amplification circuit, 27 and 28 ... analog operation circuit, 30 ... Shield shield.

Claims (5)

In the current detection device that can detect the value of the current flowing through the plurality of conductors,
A magnetic sensor that outputs a first analog signal indicating a voltage value corresponding to a magnetic flux generated by a current flowing through each conductor;
An amplifier circuit for outputting a second analog signal obtained by amplifying the first analog signal output by the magnetic sensor at a predetermined gain;
A current detection apparatus comprising: an analog arithmetic circuit that outputs a third analog signal that can calculate a current flowing in a corresponding conductor by calculating the second analog signal output from the amplifier circuit in association with each conductor. The magnetic sensor has a plurality of detection elements provided for detection of some or all of the plurality of conductors,
The amplifying circuit can output the second analog signal amplified by the amplification factor determined so that the first analog signal output from each detection element is a component corresponding to the conductor targeted for detection. Composed of
The said analog arithmetic circuit is comprised so that the said 3rd analog signal calculated for every component corresponding to the said conductor which made the detection object the said 2nd analog signal which the said amplifier circuit outputs can each be output. Current detection device.   The amplification factor is obtained by detecting the current of each conductor detected by each detection element using the relationship between the first analog signal output by each detection element and the magnetic flux density based on the conductor detected. 3. The current detection device according to claim 1, wherein each of the constants is proportional to a sum proportional to the first analog signal output from the element.   The amplification factor is a relationship between a theoretical value obtained as a proportional constant in a sum proportional to the first analog signal output by each detection element and an actual measurement value obtained from the second analog signal at the theoretical value. The current detection device according to claim 3, wherein the current detection device is adjusted to a value obtained from the actual measurement value. Each of the detection elements is two of the three conductors corresponding to each phase of the three-phase alternating current provided for detection of two specific conductors,
The amplifying circuit amplifies the first analog signals output from the two detection elements at the amplification factors determined to be components corresponding to the two specific conductors to be detected. It is composed of two each provided in
The analog arithmetic circuit is composed of two pieces provided so as to add the second analog signal output from the two amplification circuits for each component corresponding to the conductor as a detection target,
The current detection device according to claim 4, further comprising a shielding shield that covers the two detection elements together with the specific two conductors and shields the influence of an external magnetic flux.