Current detector

Abstract

To provide a current detector that is versatile enough to accurately measure a current value of a measurement target object without being restricted by a measurement target object in which a measurement target current flows.SOLUTION: A current detector 1 includes: a main bus bar B for flowing a detection target current Bi; and a semiconductor chip 2 located away from a main bus bar B. The semiconductor chip 2 includes: a branch bus bar 3 connected to the main bus bar B in parallel; a detection unit 4 located next to the branch bus bar 3, the detection unit detecting a first magnetic field H1 generated on the basis of a branch current 3i flowing from the main bus bar B to the branch bus bar 3; and an output unit 5 for operating a current I on the basis of the first magnetic field H1 detected by the detection unit 4 and outputting the current I.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a current detection device.

Background Art

[0002] Current detection devices for detecting the current flowing through conductors such as busbars of circuits are known (see, for example, Patent Document 1 and Patent Document 2). The current detection device described in Patent Document 1 includes a main busbar through which a non-detected current flows, a branch busbar branched from the main busbar, and a current sensor provided on the branch busbar. The current detection device described in Patent Document 1 calculates the current value of the main busbar based on the current value flowing through the branch busbar. The current detection device described in Patent Document 2 includes a busbar having a curved portion and a magnetic sensor disposed inside the curved portion. The current detection device described in Patent Document 2 calculates the current value of the busbar based on the detection value of the magnetic sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conductors such as busbars through which the measured target current flows are formed in various shapes according to the uses and types of electrical equipment to be attached, and the ranges of the measured current values are also different. According to the current detection devices described in Patent Document 1 and Patent Document 2, it is necessary to set the shape and the range of the detected current according to the electrical equipment to be attached, and there is a risk that the design process and the manufacturing process will become complicated.

[0005] One aspect of the present invention has been made in view of these circumstances, and aims to provide a versatile current detection device that can measure the current value of an object with high accuracy, without being limited by the configuration of the object through which the current to be measured flows. [Means for solving the problem]

[0006] A current detection device according to one aspect of the present invention comprises a main busbar through which a current to be detected flows, and a semiconductor chip disposed at a distance from the main busbar, wherein the semiconductor chip includes a branch busbar connected in parallel with the main busbar, a detection unit disposed adjacent to the branch busbar for detecting a first magnetic field generated based on a branch current flowing from the main busbar to the branch busbar, and an output unit that calculates and outputs a current value based on the first magnetic field detected by the detection unit. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a versatile current detection device that can measure the current value of an object with high accuracy, without being limited by the configuration of the object through which the current to be measured flows. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view showing an example of a current detection device according to an embodiment. [Figure 2] This is a circuit diagram showing an example of a detection unit according to the embodiment. [Figure 3] This is a block diagram showing an example of the configuration of the output unit according to the embodiment. [Figure 4] This diagram shows the arrangement of the main busbar, branch busbar, and detection unit according to the embodiment. [Figure 5] This diagram shows the arrangement of the main busbar, branch busbar, and detection unit according to the embodiment. [Figure 6] This is a plan view showing a current detection device according to Modification Example 1. [Figure 7] This is a plan view showing a current detection device according to modified example 2. [Figure 8] This is a plan view showing the arrangement of the main busbar, branch busbar, and detection unit according to Modification 3. [Figure 9] This is a plan view showing the arrangement of the main busbar, branch busbar, and detection unit according to Modification 4. [Modes for carrying out the invention]

[0009] As shown in Figures 1 to 3, the current detection device 1 includes a main busbar B through which the current to be detected Bi flows, and a semiconductor chip positioned spaced apart from the main busbar B. The semiconductor chip 2 includes a branch busbar 3, a detection unit 4 adjacent to the branch busbar 3, and an output unit 5. This current detection device 1 measures the current to be detected Bi flowing through the main busbar B by branching a portion of the current to be detected Bi flowing through the main busbar B at the branch busbar 3 and monitoring the branched current. For convenience, the X, Y, and Z axes in the drawing are set to be mutually orthogonal.

[0010] The main busbar B is, for example, a conductor formed in the shape of a rectangular plate. The main busbar B is made of a metal material such as copper, brass, or aluminum. The main busbar B is a terminal member through which a large current to be detected Bi flows, for example in a vehicle. Depending on the application, the current to be detected Bi can range from ±tens of amperes to ±1,000 amperes. The main busbar B has a predetermined electrical resistance value (first resistance value). The main busbar B is provided with, for example, an input terminal B1 into which current is input and an output terminal B2 to which current is output. In the current detection device 1, the branch busbar 3, detection unit 4 and output unit 5, as well as a portion of the main busbar B, are sealed with resin on the semiconductor chip 2.

[0011] The semiconductor chip 2 is electrically connected in parallel to, for example, the main busbar B via electrical wiring W. A branch busbar 3 is arranged on the semiconductor chip 2, separate from the main busbar B. The branch busbar 3 is formed, for example, as a rectangular plate-like body.

[0012] The branch busbar 3 has a predetermined electrical resistance value (second resistance value). The second resistance value is higher than the first resistance value. The second resistance value is set so as not to overheat in order to ensure the detection performance of the detection unit 4. The second resistance value is adjusted so that, for example, the temperature propagated to the detection unit 4 based on the amount of heat generated based on the branch current 3i flowing through the branch busbar 3 is lower than the temperature threshold that ensures the detection performance of the detection unit 4. By changing parameters such as the thickness, length, and width of the branch busbar 3 and the main busbar B in terms of shape, the ratio between the first resistance value and the second resistance value can be adjusted, and the magnitude of the branch current 3i flowing through the branch busbar 3 can be arbitrarily adjusted.

[0013] The branch busbar 3 is electrically connected in parallel with the main busbar B via electrical wiring W, which is formed of metal wire, for example. The electrical wiring W is a bonding wire formed of one of the following metal materials: gold, copper, silver, solder, or a combination of these. One end of the branch busbar 3 is connected to one end of the main busbar B on the input terminal B1 side via electrical wiring W. The other end of the branch busbar 3 is connected to the other end of the main busbar B on the output terminal B2 side via electrical wiring W. The branch busbar 3 is electrically connected in parallel with the main busbar B and is formed so that a branch current 3i proportional to the detected current Bi flows through it. The detection unit 4 is located adjacent to the branch busbar 3. By forming both the branch busbar 3 and the detection unit 4 on the surface of the semiconductor chip 2 using a semiconductor process, positional variations between the branch busbar 3 and the detection unit 4 can be suppressed, allowing for high-precision current detection.

[0014] The detection unit 4 is arranged at a predetermined distance r from the branch bus bar 3. The detection unit 4 is, for example, a magnetic sensor that detects a first magnetic field H1 generated based on a branch current 3i flowing through the branch bus bar 3. For the detection unit 4, for example, the detection direction D of the magnetic field is the normal direction (Z-axis direction) of the semiconductor chip 2 (surface). The detection unit 4 is arranged adjacent to the branch bus bar 3 and detects the first magnetic field H1 generated by the branch current 3i. Since the branch bus bar 3 and the detection unit 4 are formed on the surface (the same plane) of the semiconductor chip 2, the first magnetic field H1 can be detected at the most sensitive position, so that the current can be detected with high accuracy. The detection unit 4 is formed by, for example, a Hall element. The detection unit 4 may be a magnetic sensor such as a TMR (Tunnel Magneto Resistance) element other than the Hall element.

[0015] The detection unit 4 detects, for example, a magnetic field in a direction along a predetermined direction (the Z-axis direction in the figure). The detection unit 4 is adjusted in posture and position so as to detect, for example, a concentric first magnetic field H1 generated centering on the branch bus bar 3 through which the branch current 3i flows (see FIG. 2). Further, the main bus bar B generates a second magnetic field based on the detected current Bi. The detection unit 4 is arranged in a posture or position where it is difficult to detect the component of the second magnetic field in the detection direction of the first magnetic field H1.

[0016] Also, the predetermined distance r between the detection unit 4 and the branch bus bar 3 is set so that the amount of heat generated based on the branch current 3i does not affect the performance of the detection unit 4. The predetermined distance r is set to a value that is separated by a predetermined distance r or more such that the temperature propagated to the detection unit 4 based on the amount of heat generated based on the branch current 3i is lower than the temperature threshold value that ensures the detection performance of the detection unit 4. The arrangement of the detection unit 4 will be described later. The detection unit 4 transmits an electrical signal obtained by converting the magnetic field strength into a voltage value to the output unit 5.

[0017] The output unit 5 is arranged adjacent to the detection unit 4. The output unit 5 is electrically connected to the detection unit 4 and receives an electrical signal corresponding to the detection value of the detection unit 4. The semiconductor chip 2 is provided with a plurality of electrode terminals 6. Electrical signals and signal power supplied to the detection unit 4 and the output unit 5 are input and output to the electrode terminals 6. The plurality of electrode terminals 6 are electrically connected to the electrode portion E via, for example, bonding wires W1. The electrode portion E includes, for example, a pair of signal electrodes E1 for inputting and outputting electrical signals and a pair of power supply electrodes E2 for inputting and outputting power supply power.

[0018] The output unit 5 includes an arithmetic unit 5A having an arithmetic function and a storage unit 5B having a memory function (see FIG. 3). The arithmetic unit 5A calculates, for example, the branch current 3i flowing through the branch bus bar 3 based on the detection value of the first magnetic field generated from the branch bus bar 3 and an arithmetic expression for calculating the current. The arithmetic expression is stored in the storage unit 5B in advance. The arithmetic expression includes a magnetic field strength arithmetic expression for converting the electrical signal of the detection value into a magnetic field strength, a branch current arithmetic expression for calculating the first current value of the branch current flowing through the branch bus bar 3 based on the magnetic field strength and a predetermined distance r, and a detected current arithmetic expression for calculating the second current value of the detected current flowing through the main bus bar B. The storage unit 5B stores in advance data such as the first resistance value of the main bus bar B, the second resistance value of the branch bus bar 3, the predetermined distance r, etc. used in the arithmetic expression.

[0019] The arithmetic unit 5A calculates, for example, the magnetic field strength of the first magnetic field H1 based on the detection value and the magnetic field strength arithmetic expression. There is a relationship of H = I / 2r between the magnetic field strength H, the current value I, and the predetermined distance r, and the branch current arithmetic expression is represented by I = 2rH. The arithmetic unit 5A calculates the first current value of the branch current based on the calculation result of the magnetic field strength of the first magnetic field H1, the data of the predetermined distance r, and the branch current arithmetic expression. The arithmetic unit 5A calculates the detected current flowing through the main bus bar B based on the calculated first current value, the second resistance value of the branch bus bar 3, the first resistance value of the main bus bar B, and the detected current arithmetic expression.

[0020] The memory unit 5B is a memory having a predetermined memory capacity capable of holding data. The memory unit 5B pre-stores magnetic field strength calculation formulas, branch current calculation formulas, and detected current calculation formulas. In addition, the memory unit 5B stores, for example, the first resistance value of the main busbar B and the second resistance value of the branch busbar 3. The first and second resistance values ​​are measured, for example, by passing a predetermined test current through the main busbar B and branch busbar 3 in advance. During product characteristic testing, the branch busbar 3 is electrically connected to the main busbar B, and then the test current is passed through it. Based on the first and second resistance values, correction coefficients and correction formulas are set for the magnetic field strength calculation formulas, branch current calculation formulas, and detected current calculation formulas, and the error between the theoretical value and the measured value is corrected. Subsequently, the correction coefficients and correction formulas are stored in the memory unit 5B. The test current is measured using one or more values.

[0021] After the branch busbar 3 is electrically connected to the main busbar B, it is initialized based on a test current, and the first resistance value, second resistance value, correction coefficient, and correction formula are stored in the memory unit 5B, allowing the detected current to be accurately calculated based on the detected value of the detection unit 4. After initialization, the calculation unit 5A can calculate the current value of the detected current Bi based on the detected value of the first magnetic field, the first resistance value, the second resistance value stored in the memory unit 5B, and the corrected calculation formulas. With the above configuration, individual differences in the ratio of resistance values ​​that occur due to dimensional variations in the main busbar B and branch busbar 3, which are metal components, can be corrected by the calculations of the calculation unit 5A.

[0022] As shown in Figure 4, the detection unit 4 detects not only the first magnetic field H1 generated by the branch busbar 3, but also the component of the second magnetic field H2 generated by the main busbar B. When the direction of flow of the current Bi to be detected flowing through the main busbar B and the branch current 3i flowing through the branch busbar 3 are the same, the component of the second magnetic field H2 is given by, for example, the following equation H = I / 2R × cosθ, where R is the distance between the main busbar B and the detection unit 4, and θ is the direction angle between the height position of the main busbar B and the height position of the detection unit 4. Therefore, the closer θ is to 90°, the less the detection unit 4 is affected by the second magnetic field H2 and the more accurately it can measure the first magnetic field H1. The detection unit 4 may be positioned, for example, at a position where θ = 90°.

[0023] The detection unit 4 may be positioned in a manner that does not detect the component of the second magnetic field in the detection direction D of the first magnetic field H1. Specifically, as shown in Figure 5, the detection unit 4 may be formed such that the detection direction D is in the direction normal to the surface of the semiconductor chip 2. The detection unit 4 may be positioned in a manner and location perpendicular to the direction of the second magnetic field H2 generated by the detected current Bi in the detection direction D, and also positioned in a manner and location for detecting the first magnetic field H1 generated by the branch current 3i. Even when the detection direction D of the detection unit 4 is parallel to the surface of the semiconductor chip 2, it may still be positioned in a manner and location perpendicular to the direction of the second magnetic field H2 generated by the detected current Bi in the detection direction D, and also positioned in a manner and location for detecting the first magnetic field H1 generated by the branch current 3i. In this embodiment, the detection unit 4 is formed so that the detection direction D is in the direction normal to the surface of the semiconductor chip 2. However, it is not limited to this, and the detection direction D may be in the in-plane direction of the surface of the semiconductor chip 2. In this case, a branch busbar 3 may be formed on the surface of the semiconductor chip 2, and a vertical Hall element or the like with the detection direction D being in the in-plane direction may be formed inside the semiconductor chip 2 directly below the branch busbar 3, and the main busbar may be arranged adjacent to the semiconductor chip 2.

[0024] As described above, the current detection device 1 is electrically connected to the main busbar B via electrical wiring W, thus offering versatility regardless of the shape or mounting position of the main busbar B. The current detection device 1 can easily accommodate various types of main busbar B, reducing development and production management man-hours, and thus lowering costs. According to the current detection device 1, even if there are variations in the main busbar B or the product itself, during product characteristic inspection, the test current is measured to determine a correction coefficient or correction formula for each individual unit, and stored in the memory unit 5B, thereby accurately calculating the current to be detected. This eliminates variations due to individual differences and improves accuracy.

[0025] The current detection device 1 can reduce design man-hours and design time, as well as design costs, in designs handling small quantities of diverse products. The current detection device 1 can significantly reduce development man-hours and production management man-hours by adjusting processes such as setup time and parts management during the production stage using the design of the electrical wiring W and data stored in the memory unit 5B. The current detection device 1 can be applied to applications where a wide operating temperature range is required and relatively large currents (tens of amperes to hundreds of amperes) need to be detected non-contact, such as motor control for hybrid cars and electric vehicles, idle control for battery monitoring, and motor control for electric power steering.

[0026] [Example 1] The following describes a modified version of the current detection device. In the following description, the same names and reference numerals will be used for identical components, and redundant explanations will be omitted as appropriate.

[0027] As shown in Figure 6, the modified current detection device 1A improves the detection sensitivity of the detection unit 4. The branch busbar 3A is formed in an arch shape, for example, so as to extend around the detection unit 4. The branch current 3i flows in an arch shape along the branch busbar 3A. With the current detection device 1A, the strength of the first magnetic field H1 input to the detection unit 4 on the inner circumference side of the branch busbar 3A is improved compared to when using the branch busbar 3.

[0028] [Differentiation 2] As shown in Figure 7, in the modified example 2, the current detection device 1B differs from the current detection device 1A in that the number of wires in the electrical wiring W that electrically connects the main busbar and the branch busbar is different from that of the electrical wiring W in the above embodiment. Two or more wires of electrical wiring W may be provided at one end and the other end of the branch busbar 3A. In the current detection device 1A, the branch current 3i flowing through the branch busbar 3A may be adjusted based on the number of wires in the electrical wiring W. Alternatively, in the current detection device 1A, the branch current 3i flowing through the branch busbar 3A may be adjusted based on the diameter of the cross-section of the electrical wiring W. Changing the number of wires or the diameter of the electrical wiring W may also be applied to the current detection device 1.

[0029] [Difference 3] As shown in Figure 8, if the detection direction D of the magnetic field of the detection unit 4 is parallel to the surface of the semiconductor chip 2 (in the X-axis direction), the branch busbar 3 may be arranged superimposed on the detection unit 4. In this case, the main busbar B may be arranged adjacent to and parallel to the branch busbar 3.

[0030] [Differentiation Example 4] As shown in Figure 9, the current detection device 1 may have two or more branch busbars 3. The branch busbars 3 may include, for example, a first branch busbar 3-1 electrically connected in parallel to the main busbar B, and a second branch busbar 3-2 electrically connected in parallel to the first branch busbar 3-1. The detection unit 4 may be located adjacent to the second branch busbar 3-2. With the above configuration, the current detection device 1 has increased flexibility in the arrangement of the branch busbars 3 and the detection unit 4.

[0031] In addition to these variations, the semiconductor chip may have WLP (Wafer Level Package) wiring on its surface, with branch busbars formed in the WLP wiring.

[0032] Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be modified as appropriate without departing from the spirit of the invention. Furthermore, without departing from the spirit of the present invention, the components in the above-described embodiment can be replaced with well-known components, and the above-described modifications can be combined as appropriate. [Explanation of symbols]

[0033] 1, 1A, 1B Current detection device 3, 3A branch busbar 3-1 First branch busbar 3-2 Second Branch Busbar 3i Branch Current 4. Detection Unit 5 Output section 5A calculation section 5B Storage section B Main Bass Bar Bi detected current H1 First magnetic field H2 Second Magnetic Field I Current value r predetermined distance W Electrical wiring

Claims

1. a main bus bar through which a current to be detected flows; a semiconductor chip disposed at a distance from the main bus bar; and The semiconductor chip comprises: a branch bus bar connected in parallel to the main bus bar; a detection unit disposed adjacent to the branch busbar and configured to detect a first magnetic field generated based on a branch current flowing from the main busbar to the branch busbar; an output unit that calculates and outputs a current value based on the first magnetic field detected by the detection unit; A current detection device comprising:

2. the branch busbars are adjusted to have a second resistance value higher than a first resistance value of the main busbar; The current detection device according to claim 1 .

3. the second resistance value of the branch bus bar is adjusted so that a temperature propagating to the detection unit based on a heat quantity generated by the branch current is lower than a temperature threshold value that ensures detection performance of the detection unit; The current detection device according to claim 2 .

4. the branch busbar is disposed at a distance greater than a predetermined distance from the detection unit so that a temperature propagating to the detection unit based on the amount of heat generated by the branch current is lower than a temperature threshold value that ensures the detection performance of the detection unit; The current detection device according to claim 1 .

5. the main busbar generates a second magnetic field based on the detected current; the detection unit is disposed in an attitude or position that makes it difficult to detect a component of the second magnetic field in the detection direction of the first magnetic field. The current detection device according to claim 1 .

6. and electrical wiring formed of metal wires and electrically connecting the main bus bar and the branch bus bar. The current detection device according to claim 1 .

7. The electrical wiring adjusts the branch current based on the cross-sectional diameter or the number of wirings. The current detection device according to claim 6.

8. The branch bus bar includes a first branch bus bar electrically connected in parallel to the main bus bar; a second branch bus bar electrically connected in parallel to the first branch bus bar, the detection unit is disposed adjacent to the second branch bus bar, The current detection device according to claim 1 .

9. the semiconductor chip has a WLP wiring on its surface, The branch bus bar is formed on the WLP wiring. The current detection device according to claim 1 .

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