JP2004354106A - Current detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable and accurate current detector only requiring a minimum space with minimized component costs and assembly man-hours. <P>SOLUTION: In this current detector, an electric circuit and an electric current path 14 connected to the electric circuit are formed on a substrate 12 while the detector is adapted to detect a current flowing through the current path 14. The current path 14 is disposed in such a shape as to surround a prescribed position 16 on the substrate 12 and provided with a magnetism detection element 17 in the prescribed position 16 or in the vicinity thereof for converting magnetic flux generated correspondent to the size of current into a voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a current detecting device for detecting a motor current or the like, and more particularly to a non-contact current detecting device for a vehicle-mounted electric component such as an electric power steering device.
[0002]
[Prior art]
This type of conventional current detection device has a configuration in which a bus bar serving as a path of a detected current penetrates a C-shaped magnetic core, and a magnetic field generated by the detected current flowing through the bus bar is detected by the C-shaped magnetic core. At the same time as the magnetic flux is collected, the voltage is converted into a voltage by a Hall element installed in a gap portion of the magnetic core, and a predetermined amplification is performed by an amplifier circuit to obtain a current detection output (a voltage value proportional to the current to be detected). .
In addition, as a method that does not use a magnetic core, a conductive metal plate serving as a current path to be detected is curved in a U-shape or a U-shape, and a Hall element is arranged at the center thereof to obtain a voltage value proportional to the current to be detected. There are also devices that do so. (See, for example, Patent Documents 1 and 2).
[0003]
[Patent Document 1]
JP 2001-174486 A (paragraph 0016, FIGS. 1 and 5)
[Patent Document 2]
JP-A-2003-4771 (paragraph 0011, FIG. 7)
[0004]
[Problems to be solved by the invention]
Since the conventional non-contact type current detecting device is configured as described above, there are the following problems. That is, in the case of using a C-shaped magnetic core, the shape of the magnetic core becomes large, which may cause a problem in the mountability of a small-sized control device, particularly a vehicle-mounted control device. Also, the number of parts and the number of assembling steps are large, which is disadvantageous in terms of cost. Furthermore, the influence of the hysteresis characteristic of the magnetic core may adversely affect current detection accuracy and detection stability.
Furthermore, in the method without using a magnetic core, in order to obtain a practical detection sensitivity, it is necessary to increase the detected current density in the vicinity of the magnetic detecting element. The width had to be reduced to some extent. However, for this reason, when it is necessary to detect a current of several tens of amperes or more, such as a motor current, there is a concern that heat is concentrated near the magnetic detection element of the current path conductor to be detected. Since it is necessary to fix and package the conductor and the magnetic detection element with a resin mold or the like, there is a problem of heat radiation, an increase in volume, or an increase in cost. Further, since the current detection unit is configured separately from the control circuit board that requires current detection, there is a problem that the current detection unit needs to be attached and connection wiring to the control circuit board is required.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a stable and high-accuracy current detection device that minimizes the cost of parts and the number of assembling steps and minimizes space. With the goal.
[0006]
[Means for Solving the Problems]
The current detection device according to the present invention is a current detection device, wherein an electric circuit and a current path connected to the electric circuit are formed on a substrate, and the current detection device detects a current flowing through the current path. The current path is provided in a shape surrounding a predetermined location on the substrate, and a magnetic detection element that converts a magnetic flux generated according to the magnitude of current into a voltage at or near the predetermined location is provided. is there.
In a power or power control circuit such as a motor drive circuit or a power supply circuit that requires current detection, a heat radiating means (heat sink) for efficiently radiating heat generated from a power control semiconductor element constituting the power or power control circuit in many cases. Originally.
The present invention effectively dissipates heat generated when a detected current such as a motor current flows through a current path pattern by sharing the heat radiating means, and enables stable current detection in a small space. . In particular, this is an effective means when the power control semiconductor element is arranged on a metal substrate (aluminum substrate) or a ceramic substrate.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1A and 1B are schematic diagrams showing a configuration of the first embodiment, in which FIG. 1A is a plan view and FIG. 1B is a side view.
As shown in this figure, the current detection device 1 of the first embodiment forms a control circuit such as a motor drive circuit that requires current detection and is disposed on an aluminum substrate 12 having a heat sink 11 for heat radiation. Then, the current of the motor drive circuit and the like formed through an insulating layer 13 such as an epoxy film containing a filler of about 70 μm is detected. A detected current path pattern 14 is formed on the aluminum substrate 12 as a current detection path of the electric circuit. The detected current path pattern 14 is formed of, for example, a copper foil having a thickness of about 80 μm, and a notch (slit) 15 having a width of about 0.2 mm is provided in the copper foil in a shape as illustrated. That is, the slit 15 is formed such that the current path is formed in an arc shape centered on the predetermined location 16 as shown by an arrow in FIG.
[0008]
As a result, a magnetic flux of a number proportional to the magnitude of the current to be detected is generated at the predetermined location 16, so that a magnetic detection element for converting the magnetic flux density into a voltage, for example, a Hall element 17, is provided at or near the predetermined location 16. As a result, a voltage output proportional to the current to be detected can be obtained. Reference numeral 18 denotes a voltage source for applying an operating voltage to the Hall element 17, and 19 denotes a lead wire for extracting a voltage output of the Hall element 17, and is connected to a pad 20 for connecting to the aluminum substrate 12. The voltage output of the Hall element 17 is amplified to a necessary degree by the amplifier circuit 21 and is taken out as a current detection output 22 corresponding to the current to be detected.
[0009]
Note that the magnetic flux density generated at the predetermined location 16 by the current flowing around the predetermined location 16 of the detected current path pattern 14 increases as the radius of the arc-shaped line decreases, assuming that the current has the same magnitude. Therefore, the detection sensitivity can be increased by reducing the circumference of the detected current path pattern 14 and reducing the width of the detected current path pattern 14. However, when the circumference of the current path is reduced and the path width is reduced, when a large current flows through the current path, heat generation at that portion becomes excessive. Therefore, by inserting the slit 15 in the detected current path pattern 14 at an appropriate position, the path through which the current actually flows is concentrated on the inner peripheral side of the arc, and the connection with the thermally conductive outer side conductor pattern is sufficiently provided. To ensure heat dissipation. As a result, the detection density can be sufficiently increased by increasing the current density of the detected current in the vicinity of the detection point of the Hall element 17.
[0010]
Embodiment 2 FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a side view showing the configuration of the second embodiment. The plan view is the same as FIG.
In FIG. 2, the same or corresponding parts as those in FIG. The difference from FIG. 1 is that a multilayer ceramic substrate 30 (FIG. 2 exemplifies a case of four layers) is used instead of the aluminum substrate 12, and a first ceramic substrate 30 shown in FIG. Are formed, the detected current path pattern 14 having the same shape is formed in each of the second layer 30b to the fourth layer 30d, and as many vias (interlayer connection conductors) 31 as possible are provided. Thus, the detected current path patterns 14 formed in each layer are electrically and thermally coupled to each other to reduce the electric resistance and the thermal resistance of the detected current path patterns 14. Reference numeral 32 denotes a high thermal conductive insulating adhesive layer that couples the multilayer ceramic substrate 30 and the heat sink 11.
With such a configuration, an allowable measured current value can be increased.
[0011]
Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a schematic diagram showing the configuration of the third embodiment, in which a multilayer ceramic substrate 30 is used as in the second embodiment (FIG. 3 illustrates the case of five layers). In FIG. 3, the same or corresponding parts as those in FIGS. 2 is different from FIG. 2 in that a relatively small current (up to about 10 amperes) can be accurately detected at low cost. Each of the layers 30a to 30e of the multilayer ceramic substrate 30 has a different structure. Of the arc-shaped current paths 14a to 14e surrounding the predetermined portion 16 of the detected current path pattern to be formed, the end part ae of the first layer arc-shaped current path 14a and the start end part of the second layer arc-shaped current path 14b bs is connected by a via (interlayer connection conductor) 31, and the end be of the arc current path 14 b of the second layer and the start end cs of the arc current path 14 c of the third layer are connected by a via (interlayer connection conductor). Then, the current path of each layer is connected in series by connecting the end of the arc-shaped current path in the upper layer and the start end of the arc-shaped current path in the lower layer in the same manner as described above. Is a point to be formed.
[0012]
When a current flows through the detected current path configured as described above, the magnitude of the magnetic flux density at the center of the coil-shaped current path is proportional to the number of turns of the coil. That is, as shown in FIG. 3, by forming the detected current path patterns 14a to 14e having a multi-layer structure into a multi-turn coil shape, the current detection sensitivity can be increased at a low cost without using a magnetic core or the like. , It is possible to improve the detection accuracy.
The shapes of the detected current path pattern 14 and the slits 15 shown in FIGS. 1 to 3 are merely examples, and the properties of the current value to be handled, the thermal resistance of the substrate, the properties of the metal forming the detected current path pattern, and the like. It goes without saying that the optimum shape is determined by magnetic and thermal simulations based on the film thickness and the sensitivity of the Hall element.
[0013]
In the above description, the Hall element is exemplified as the magnetic detection element. However, the same effect can be expected by using another magnetic detection element. Further, the same configuration can be obtained by using a so-called Hall IC in which an amplifier circuit is built in the resin mold of the Hall element.
[0014]
【The invention's effect】
The current detection device according to the present invention is a current detection device in which an electric circuit and a current path connected to the electric circuit are formed on a substrate, and the current detection device detects a current flowing through the current path. The current path is provided in such a shape as to surround a predetermined location on the substrate, and a magnetic detection element for converting a magnetic flux generated according to the magnitude of the current into a voltage at or near the predetermined location is provided. Therefore, it is possible to obtain a stable and accurate non-contact type current detection device with a minimum space while reducing the cost of parts and the number of assembling steps as much as possible.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a first embodiment of the present invention, wherein (A) is a plan view and (B) is a side view.
FIG. 2 is a side view showing a configuration of a second embodiment of the present invention.
FIG. 3 is a schematic diagram showing a configuration of a third embodiment of the present invention.
[Explanation of symbols]
1 current detection device, 11 heat sink, 12 aluminum substrate,
13 insulating layer, 14 current path pattern to be detected,
15 slit, 16 predetermined place, 17 Hall element,
18 voltage sources, 19 leads, 20 pads,
21 amplifier circuit, 22 current detection output,
30 multilayer ceramic substrate, 31 via,
32 High thermal conductive insulating adhesive layer.

Claims (4)

An electric circuit and a current path connected to the electric circuit are formed on a substrate, and the current detecting device is configured to detect a current flowing through the current path. A current detection device, which is provided in a shape surrounding a location, and provided with a magnetic detection element for converting magnetic flux generated according to the magnitude of current into a voltage at or near the predetermined location. 2. The current detecting device according to claim 1, wherein the substrate has a multilayer structure, a current path is formed in each layer, and a plurality of interlayer connection conductors extending between the layers are provided to connect the current paths in each layer. . An electric circuit and a current path connected to the electric circuit are formed on a substrate having a multilayer structure, and the current detecting device is configured to detect a current flowing through the current path. A terminal provided on each layer so as to surround the corresponding place in the upper predetermined place or each layer, and connecting the terminal end of the current path surrounding the predetermined place or the corresponding place to the start end of the current path in the lower layer by an interlayer connection conductor. A current path of each layer is formed as a whole in the form of a coil, and a magnetic detection element for converting a magnetic flux generated in accordance with the magnitude of the current into a voltage at or near the predetermined location is provided. Detection device. The current detection device according to claim 1, wherein a slit is formed in the current path so that a current density near the predetermined location is increased.

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