JP2003232814A - Current detection device and current detection device for inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve detection accuracy of a current detection device wherein a motor loaded on an automobile or the like is used for an inverter device driven by using a low-voltage battery as a power source. <P>SOLUTION: A potential difference taking-out wiring pattern for taking out a potential difference between both ends of a shunt resistance mounted or provided on a printed circuit board is drawn out from a spot where a current to be detected hardly flows on a shunt resistance mounting land. Otherwise, the wiring pattern for taking out the potential difference between both ends of the shunt resistance is drawn out from a land fringe part positioned on the prolonged line of a wiring pattern for the current to be detected connected to the shunt resistance mounting land. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detecting device, and more particularly to a current detecting device suitable for an inverter device for driving a motor mounted on an automobile or the like using a low voltage battery as a power source.

[0002]

2. Description of the Related Art In recent years, in order to control a motor mounted on an automobile or the like, it is necessary to use a permanent magnet motor with a rotor position sensor because of requirements such as variable speed, environmental resistance, and ease of maintenance. Instead, an increasing number of examples are adopting a position sensorless vector control method in which vector control is performed by a voltage type PWM inverter circuit. Although various methods have been proposed for this position sensorless vector control method, most of them model the motor in a stator coordinate system or a rotor coordinate system, and estimate the rotor position using voltage and current estimation errors. It is a thing. The current and voltage of the motor are required for the estimation calculation of the rotor position, and the measured value is often used as the motor current, and the measured value or the command voltage to the voltage source inverter is often used as the motor voltage. The detection accuracy of the motor current has a great influence on the controllability of the motor, and when the accuracy is low, it causes vibration and noise in the motor, and therefore it is desired to detect with high accuracy.

FIG. 5 shows an example of the main circuit configuration of a voltage type inverter. The inverter circuit 100 in the figure is a circuit that supplies a three-phase alternating current to the permanent magnet motor 116, and the main circuit is configured by the switching elements 101 to 106 and the freewheel diodes 107 to 112. In the present circuit, the current flowing in each phase of the motor 116 is not detected by providing a hall element or a current transformer in the middle of wiring from the inverter 100 to each coil, but is detected by the lower arm switching elements 104 to 106 and the battery power source. The shunt resistors 113 to 115 are connected between the negative side DC bus 118 of 117 and the potential difference across the shunt resistors is detected to calculate the phase current of each motor. This calculation method is described in, for example, Japanese Patent Laid-Open No. 61-26.
2084.

[0004]

The current detecting device using such a shunt resistor has an advantage that the detector is smaller and less expensive than the device using the conventional Hall current detector or current transformer. On the other hand, when a shunt resistor is mounted on the printed circuit board to reduce the size of the device, the large motor current flowing through the shunt resistor causes the resistance value to change due to the heat generated by the shunt resistor, and the wiring pattern part where the detected current flows Problems such as an increase in voltage drop occur, making it difficult to accurately detect the current value. In particular, in the case of an inverter device mounted on an automobile or the like and driving a motor with a low-voltage battery as a power source, a low-voltage, large-current output is produced, which makes further difficulty in accurate current detection. The present invention has been devised in order to reduce the problem in such a case, and an object thereof is to provide a device capable of accurately detecting a current even when a large current flows through a shunt resistor.

[0005]

According to a first aspect of the present invention, there is provided a current detecting device, wherein a shunt resistor is attached in the middle of a current path to be detected formed by a wiring pattern on a printed circuit board, and a potential difference across the shunt resistor is detected. In the current detecting device for detecting the magnitude of the current flowing through the current passage, the wiring pattern for extracting the potential difference between the both ends of the shunt resistor is provided at the outer edge portion in the land for mounting the shunt resistor where almost no detected current flows. It was designed to be pulled out from. By pulling out like this, the resistance of the wiring pattern connected to the shunt resistor,
The influence of the potential difference generated due to the resistance of the land portion can be minimized, and the potential difference across the shunt resistor can be accurately detected, and the detection accuracy of the detected current can be improved.

According to a second aspect of the present invention, in the outer edge of the land, the wiring pattern for extracting the potential difference between both ends of the shunt resistor is located on the extension line of the wiring pattern for the detected current connected to the land for mounting the shunt resistor. It is designed to be pulled out from the department. Such an outer edge portion of the land is a portion where the current to be detected flowing out from the land is not easily affected by the potential difference generated due to the resistance of the land and the wiring pattern, and thus is hardly affected by the potential difference, and the both ends of the shunt resistor are not affected. The potential difference can be detected, and the detection accuracy of the detected current can be improved.

According to another aspect of the present invention, there is provided a shunt resistor mounting land and a detected current wiring pattern.
It is provided on a metal-based printed board or a ceramics-based board having good thermal conductivity. Improved heat dissipation reduces the temperature rise of the shunt resistance,
The change in resistance value with temperature rise is reduced, and the current detection accuracy is improved.

According to another aspect of the current detecting device of the present invention, the shunt resistor is formed by a meandering wiring pattern provided on the printed circuit board. In this way, no special component is needed for the shunt resistor, and the labor for mounting the component can be saved.

According to a fifth aspect of the current detecting device of the present invention, the shunt resistor is formed in a flat chip shape. By doing so, the mounting density is increased and the height of the printed circuit board is lowered, so that the device can be downsized.

According to the sixth aspect of the present invention, a temperature detecting element is attached near the shunt resistor to detect the temperature, and the resistance value of the shunt resistor is temperature-corrected. A large current flows through the shunt resistor, so even if the resistance value is lowered, it will generate considerable heat and the temperature will rise, but the current value can be calculated by correcting the resistance value and using the corrected resistance value to calculate the current. It is possible to improve the detection accuracy of.

According to a seventh aspect of the present invention, a current detecting device is provided near the shunt resistor formed by the zigzag wiring pattern to attach a temperature detecting element to detect the temperature and correct the resistance value of the shunt resistor. It is the one. Also in this case, the current detection accuracy can be improved by using the resistance value after temperature correction.

An electric current detection device according to claim 8 is the electric current detection device according to claim 1.
In an inverter device using the current detection device according to any one of 1 to 7, it is possible to improve load current control accuracy by improving current detection accuracy.

According to a ninth aspect of the present invention, there is provided a current detecting device which is an inverter device for vector control of a motor, which uses the current detecting device according to any one of the first to seventh aspects. It is possible to improve the accuracy of motor speed control and torque control.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of a wiring pattern on a printed circuit board of a current detection device of the present invention in which a shunt resistor is attached in the middle of a current path to be detected formed on the printed circuit board and a potential difference across the shunt resistor is taken out. It is shown. In the figure, 1 is a shunt resistor for converting the current to be detected into a voltage. If the current to be detected is a current flowing through a motor powered by a low voltage battery,
Since the current value is large and the amount of heat generated is large, for example, a shunt resistor made of Al and having a low resistance value of tens of mΩ or less and having a flat chip shape is used. The shunt resistor 1 is fixed by soldering a terminal portion to two lands (terminal regions) 2a and 2b provided on the printed board. In the figure, shaded portions 3a and 3b at both ends of the shunt resistor 1 represent contact portions between the terminal portion of the shunt resistor 1 and the lands 2a and 2b which are to be soldered.

On the lands 2a and 2b, a wiring pattern 4 as a current path for guiding the detected current to the shunt resistor 1 is formed.
a and 4b are connected. The arrows marked in the wiring patterns 4a and 4b and in the shunt resistor 1 indicate the direction of current flow for convenience of description later. In this figure, the wiring patterns 4a and 4b are arranged such that the land 2 extends in the extension direction of the flow direction of the current flowing through the shunt resistor 1.
This is the case of the layout drawn from a and 2b. The broken lines marked on the boundaries between the lands 2a and 2b and the wiring patterns 4a and 4b are temporarily drawn in order to clarify the boundaries between the portions called lands and the portions called wiring patterns. There is no structure.

A current to be detected by a motor or the like flows into an input / output land (not shown) on a printed circuit board by a wiring cable, and then is guided to lands 2a and 2b to which the shunt resistor 1 is connected through wiring patterns 4a and 4b. . Then, by flowing through the shunt resistor 1, a potential difference proportional to the magnitude of the current is generated across the shunt resistor 1.

The generated potential difference is the wiring pattern 5a, 5 for extracting the potential difference extracted from the lands 2a, 2b.
It appears on the potential difference output lands 6a and 6b via b.
The potential difference appearing on the potential difference output lands 6a and 6b is guided to a differential amplifier by a wiring cable, amplified, and then AD-converted into a digital amount, which is divided by the resistance value of the shunt resistor 1 to obtain the target value. The detected current value is obtained. When the differential amplifier is mounted on the printed circuit board to which the shunt resistor 1 is mounted, the potential difference extracting wiring patterns 5a and 5b are directly connected to the input terminals of the differential amplifier.

Now, considering the current paths of the detected currents flowing on the wiring patterns 4a and 4b and the lands 2a and 2b, as shown in FIG.
When b extends from the lands 2a and 2b in the extension direction of the current flow direction on the shunt resistor 1, approximately 2
The shunt resistor terminals flow into the soldering surfaces 3a and 3b of the printed circuit board through the current flow paths as indicated by the arrowed lines 7a to 7e with thin lines. In this case, since the conductors forming the wiring patterns 4a and 4b and the lands 2a and 2b have resistance, when a large current such as a motor current flows, an electric field, that is, a potential, is generated along the current flow path. A gradient is created.

The resistance of the conductor forming the wiring patterns 4a and 4b is, for example, about 0.5 mΩ for a width of 1 mm and a length of 1 mm in the case of a copper foil having a thickness of 35 μm.
When the resistance value of is a low value of several tens of mΩ or less, the value cannot be ignored. Therefore, when a large current to be detected is passed through a shunt resistor having a low resistance value to detect the potential difference across the shunt resistor, the potential difference extracting wiring patterns 5a and 5b for detecting the potential difference are wiring patterns through which the current to be detected flows. The shunt resistor 1 is not affected by the potential difference generated along the current flow paths in the lands 4a and 4b and the lands 2a and 2b.
It is important to pull out from the position where only the potential difference between the two ends can be accurately taken out.

FIG. 2 shows a typical current flow path in the vicinity of the terminals of the shunt resistor 1 when the shunt resistor 1 and the detected current wiring patterns 4a and 4b have a layout relationship as shown in FIG. It is a thing. As for the vicinity of the upper terminal portion 3a where the detected current flows into the shunt resistor 1, the flow path 7a and the terminal portion 3a that flow straight from the wiring pattern 4a to the terminal portion 3a of the shunt resistor 1 bypass the terminal portion 3a, and the direction is about 90. The flow paths 7b and 7c which are changed to flow laterally into the terminal portion 3a, and the flow paths 7d and 7e which largely bypass and flow from the back surface portion to the terminal portion 3a in the substantially opposite direction are representative. Since there is a potential difference along these flow paths as described above, it is not preferable to draw out the potential difference extracting wiring patterns 5a and 5b from the middle of these flow paths.

On the other hand, in FIG. 2, the outer edge portion of the land 2a to which the potential difference extracting wiring pattern 5a is connected, that is, the land outer edge portion 8a located on the extension line of the wiring pattern 4a through which the detected current flows is Due to the symmetry of the layout, the current component in the direction orthogonal to the flow direction of the current to be detected indicated by the thick arrow in the wiring pattern 4a is zero. In addition, the terminal portion 3 of the shunt resistor 1 is connected to the outer edge 8a
The current component flowing toward a is not zero,
Its current density is much lower than the current passing through the other channels.
That is, the vicinity of the land outer edge portion 8a is a portion where the potential difference which is generated by the current flowing through the land 2a and acts as an error voltage with respect to the potential difference across the shunt resistor 1 is detected.

Similarly, regarding the vicinity of the lower terminal portion 3b in FIG. 2 where the current flows out from the shunt resistor 1, also in this case, the vicinity of the land outer edge portion 8b located on the extension line of the wiring pattern 4b through which the detected current flows is This is the part that is most unlikely to be affected by the error voltage. Thus, in this embodiment,
Since the wiring patterns 5a and 5b for extracting the potential difference for detecting the potential difference between both ends of the shunt resistor 1 are drawn from the location of the land 2a and 2b to which the shunt resistor 1 is attached, where the detected current hardly flows. It is possible to accurately detect the potential difference across the shunt resistor 1. Therefore, there is an effect that the accuracy of the value of the detected current calculated from that value is also improved.

Next, a second embodiment will be described with reference to FIG. This figure shows wiring patterns 4a and 4b through which detected current flows.
Is at a right angle to the flow path of the current flowing in the shunt resistor 1,
Further, this is the case of the layout in which the lands 2a and 2b are drawn out in the same direction. In this case, the lands 2a, 2b
The above-mentioned portion where the detected current hardly flows is near the land outer edge portions 9a and 9b located on the extension lines of the wiring patterns 4a and 4b through which the detected current flows, and therefore, the potential difference extraction for detecting the potential difference from this portion is performed. Wiring pattern 5a,
5b is pulled out. By pulling out from such a place, as in the case of the first embodiment, the lands 2a,
The influence of the error voltage due to the current flowing in 2b can be minimized, and the value of the detected current can be detected with high accuracy.

FIG. 4 shows a third embodiment. In this embodiment, as a shunt resistor, a shunt resistor having a chip shape or the like is not soldered to a printed circuit board, but a zigzag folded wiring pattern 10 as shown in the figure is formed by a laminated conductor such as a copper foil of the printed circuit board. The resistance of this wiring pattern is used as a shunt resistance. Although the resistance value of the conductor forming the wiring pattern is not high, by forming the length of the zigzag wiring pattern 10 to some extent, a sufficient potential difference can be obtained at both ends thereof when the detected current is large. in this way,
If the shunt resistor is formed by the wiring pattern, parts such as a chip-shaped shunt resistor are not needed, and the labor for attaching them to the printed circuit board can be omitted.

It is preferable to use a metal-based printed board or a ceramic base board having good thermal conductivity as the printed board on which the shunt resistor mounting land and the wiring pattern described above are formed. Since such a substrate has a good heat dissipation property, the temperature rise of the shunt resistor is small, the resistance value change of the shunt resistor due to the temperature rise is small, and the current detection accuracy can be improved.

Further, it is preferable that a resistance temperature detector or other temperature detecting element is attached near the shunt resistor on the printed circuit board to detect the temperature and the temperature of the resistance value of the shunt resistor is corrected based on the detected temperature. . With this configuration, the detection accuracy of the detected current can be further improved.

Further, the current detecting devices shown in the first to third embodiments can be adopted in the current detecting shunt resistors 113 to 115 of the inverter circuit as shown in FIG. Then, if the motor is vector-controlled using an inverter device that adopts such a current detection device,
By improving the current detection accuracy, it is possible to improve the accuracy of motor speed control and torque control.

[0028]

As described above, according to the current detecting device of the present invention, the wiring pattern for taking out the potential difference between both ends of the shunt resistor, which is attached or provided on the printed circuit board, is provided in the land portion for attaching the shunt resistor. Since the current to be detected is drawn from the point where it hardly flows, the potential difference across the shunt resistor can be accurately detected by avoiding the influence of the potential difference caused by the resistance of the wiring pattern wired to the shunt resistor and the resistance of the land part. The detection accuracy of the current to be detected can be improved.

If such a current detection device is adopted in the vector control inverter device of the motor, the current detection accuracy is improved, so that the speed control and torque control accuracy of the motor can be improved.

[Brief description of drawings]

FIG. 1 is a wiring pattern diagram on a printed circuit board showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a current flow path according to the first embodiment of the present invention.

FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 4 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 5 is a configuration example of a main circuit of an inverter device.

[Explanation of symbols]

In the figure, 1 is a shunt resistor, 2a and 2b are lands, 3a,
3b is a contact portion between the shunt resistor terminal portion and the printed circuit board,
4a and 4b are wiring patterns 5a and 5 through which a detected current flows.
b is a wiring pattern for extracting a potential difference, 6a and 6b are lands for outputting a potential difference, 7a to 7e are representative current flow paths, 8
a and 8b are the outer edge of the land, which is less affected by the current to be detected, 9
a and 9b are the outer edge of the land, which is less affected by the detected current, 1
0 is a zigzag wiring pattern, 100 is an inverter circuit, 101 to 106 are switching elements, and 107 to 11
2 is a freewheel diode, 113-115 are shunt resistors, 116 is a permanent magnet motor, 117 is a battery, and 118 is a negative side DC bus.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Haruhiko Ishihara             33, Isogo, Isogo-ku, Yokohama-shi, Kanagawa             Company Toshiba Production Technology Center F-term (reference) 2G025 AA07 AA09 AB05 AC04                 2G035 AA03 AA08 AC02 AD10 AD54

Claims (9)

[Claims] 1. A shunt resistor is attached in the middle of a detected current path formed by a wiring pattern on a printed circuit board.
In the current detecting device for detecting the magnitude of the current flowing through the current path by detecting the potential difference across the shunt resistor, a wiring pattern for extracting the potential difference across the shunt resistor is provided on the shunt resistor mounting land portion. A current detection device characterized in that the current to be detected is drawn from an outer edge portion where almost no current flows. 2. A wiring pattern for extracting a potential difference between both ends of the shunt resistor is drawn from an outer edge portion of a land located on an extension line of the wiring pattern for the detected current connected to the land for mounting the shunt resistor. The current detection device according to claim 1. 3. The land for mounting the shunt resistor and the wiring pattern for the detected current are provided on a metal base printed board or a ceramic base board having good thermal conductivity. Current detection device. 4. The current detecting device according to claim 1, wherein the shunt resistor is formed by a meandering wiring pattern provided on a printed circuit board. 5. The current detecting device according to claim 1, wherein the shunt resistor has a flat chip shape. 6. The current according to claim 1, wherein a temperature detecting element is attached near the shunt resistor to detect the temperature, and the temperature of the resistance value of the shunt resistor is corrected. Detection device. 7. A temperature detecting element is mounted near the shunt resistor formed by the zigzag wiring pattern to detect the temperature, and the temperature of the resistance value of the shunt resistor is corrected. Current detection device. 8. An inverter device using the current detection device according to claim 1. 9. An inverter device for vector control of a motor, which uses the current detection device according to any one of claims 1 to 7.