JP2005156445A - Circuit board and current detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board capable of detecting an accurate current value independently of a surrounding environment or dispersion at the manufacturing time. <P>SOLUTION: A current detection wire 3 connected to a power load or the like is formed on a substrate body 2. In addition, a correction wire 11 for correcting a detected value of voltage drop in a prescribed distance of the current detection wire 3 is provided on the substrate body 2 close to the current detection wire 3, and necessary correction is performed to the voltage drop of the current detection wire 3 by using the voltage drop in the prescribed distance when a constant current I2 is made to flow in the correction wire 11, to thereby determine the current I1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a circuit board configured to detect a current flowing in a main circuit based on a voltage drop.

A circuit board manufactured for controlling a power load such as a motor has a configuration in which copper wiring is formed on a board body and predetermined circuit elements are mounted. In such a circuit board, the current supplied to the power load is monitored based on the voltage drop of the copper wiring having a predetermined resistance value (see, for example, Patent Document 1). Specifically, the current is calculated from the resistance value at the time of designing the copper wiring and the actually measured value of the voltage drop.
JP 2002-5968 A

However, although the design value is used as the resistance value of the copper wiring when obtaining the current value, the resistance value of copper has a large temperature coefficient, and the resistance value changes when the substrate temperature changes, so that a detection error occurs. It was easy. Also, in the case of printed wiring, the copper wiring thickness may vary from lot to lot, so the actual resistance value of the copper wiring may differ from the design value, causing an error in the current value. It was.
The present invention has been made in view of such a problem, and an object of the present invention is to provide a circuit board capable of detecting a correct current value without depending on the surrounding environment and variations during manufacture. . It is another object of the present invention to accurately detect a current flowing through a main circuit using such a circuit board.

In the invention according to claim 1 of the present invention for solving the above-mentioned problem, a current detection wiring for detecting a current flowing in a main circuit is formed on a substrate body, and a voltage drop in the current detection wiring is detected. A voltage detection circuit is connected to the current detection wiring, and a correction circuit for correcting a detected value of the voltage drop of the current detection wiring detected by the voltage detection circuit is provided at a position close to the current detection wiring. The circuit board is characterized by this.
According to this circuit board, since the correction circuit is provided in the vicinity of the current detection wiring, in detecting the current flowing through the main circuit from the voltage drop in the current detection wiring, an error caused by the temperature of the current detection wiring is eliminated. Correction can be made with information obtained from the correction circuit.

According to a second aspect of the present invention, in the circuit board according to the first aspect, the correction circuit forms the correction wiring connected to a constant current source in the vicinity of the current detection wiring and the correction circuit. A correction voltage detection circuit for detecting a voltage drop in the wiring is provided.
In this circuit board, the correction circuit is configured as a circuit for detecting a voltage drop when a constant current is passed through the correction wiring. Therefore, when a voltage drop is detected when a constant current is passed through the correction wiring, the resistance value at that temperature can be accurately measured. Here, since the correction wiring and the current detection wiring are arranged close to each other, the temperatures thereof can be regarded as the same. Therefore, when the resistance value of the current detection wiring is corrected with the resistance value of the correction wiring detected in this way, the current flowing through the main circuit has a predetermined voltage drop ratio between the current detection wiring and the correction wiring. Since it is obtained as a value multiplied by a constant, the current flowing through the main circuit can be accurately obtained without depending on the temperature.

The invention according to claim 3 is the circuit board according to claim 2, wherein the current detection wiring and the correction wiring are printed wirings and have substantially the same thickness.
According to this circuit board, the current detection wiring and the correction wiring can be easily formed by the printed wiring. Furthermore, since the current detection wiring and the correction wiring are made of the same material and have the same thickness, the resistance value of the current detection wiring can be easily corrected using the resistance value of the correction wiring.

According to a fourth aspect of the present invention, in the circuit board according to the third aspect, the line width of the correction wiring is narrower than the line width of the voltage detection wiring.
According to this circuit board, since the resistance of the correction wiring is increased, the current flowing through the correction wiring is decreased. Therefore, current control of the constant current source of the correction circuit is facilitated.

According to a fifth aspect of the present invention, in the circuit board according to any one of the first to fourth aspects, the substrate body is a metal substrate using a metal material.
According to this circuit board, the heat conduction of the board body is improved, and variations in the board temperature are reduced.

According to a sixth aspect of the present invention, a current flowing through the main circuit is caused to flow through the current detection wiring, a voltage drop in the current detection wiring is detected, and a correction wiring provided close to the current detection wiring is provided. A constant current is supplied, a voltage drop in the correction wiring is detected, and a current value that does not depend on a temperature change is obtained as a current value flowing in the main circuit from each voltage drop in the current detection wiring and the correction wiring. It was set as the electric current detection method characterized by obtaining.
According to this current detection method, the resistance value of the correction wiring at that temperature can be obtained by detecting the voltage drop when a constant current is passed through the correction wiring. The resistance value of the wiring can be corrected. Thus, the current flowing through the main circuit can be detected from the resistance value of the current detection wiring whose temperature has been corrected and the actually measured voltage drop. When the current is detected in this manner, the temperature of the substrate body and the wiring is not affected.

According to the first aspect of the present invention, the correction circuit is provided in the vicinity of the current detection wiring, and the electric characteristics on the current detection wiring side are corrected based on the information of the correction circuit. The flowing current can be accurately detected without depending on the temperature.
According to the invention described in claim 2, since the correction circuit includes the correction wiring connected to the constant current source, the temperature characteristic of the current detection wiring can be corrected by the resistance value of the correction wiring. it can. Therefore, the current flowing through the main circuit can be accurately detected without depending on the temperature.
According to the invention described in claim 3, since the current detection wiring and the correction wiring are printed wirings, the thicknesses of both can be made substantially the same. In different cases, the current flowing through the main circuit can be detected with high accuracy.
According to the fourth aspect of the invention, since the line width of the correction wiring is narrowed, a constant current can be stably passed through the correction wiring. Therefore, since the resistance value of the correction wiring can be measured with high accuracy, the current of the main circuit corrected based on this can be detected with high accuracy.
According to the fifth aspect of the present invention, since the substrate body is made of metal, variations in the substrate temperature are reduced, and the current can be detected with high accuracy.
According to the invention described in claim 6, a constant current is supplied to the correction wiring provided close to the current detection wiring, a voltage drop in the correction wiring is detected, and the resistance value of the current detection wiring is corrected. As a result, the current flowing through the main circuit can be accurately detected without being affected by the temperature of the substrate body and wiring.

The best mode for carrying out the invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the circuit board 1 has a configuration in which a predetermined circuit is formed on a board body 2. The circuit board 1 is provided to detect a current supplied to a power load (main circuit) such as a motor, for example.
The substrate body 2 is made of ceramics such as glass, a material made of glass and synthetic resin, or a metal material such as aluminum. Here, from the viewpoint of keeping the variation in the substrate temperature to a minimum, it is desirable to use a metal material having good thermal conductivity.

  On the substrate body 2, a current detection wiring 3 having a line width W1 and a substantially U-shape is formed. The current detection wiring 3 is a copper printed wiring having a predetermined resistance value. A lead wire 4 and a lead wire 5 are attached to one end and the other end using solder or the like, respectively. The lead wire 5 is connected to the main circuit. The lead wire 4 is connected to a circuit that supplies current to the main circuit. When the substrate body 2 is made of a metal material, the current detection wiring 3 is formed after an insulating layer is formed on the substrate surface.

  The current detection wiring 3 is connected with two wirings 6 and 7 at an interval L1 in an intermediate straight line portion 3a from one end to the other end. The wirings 6 and 7 have a sufficiently narrow line width than the current detection wiring 3, and each is connected to a main voltage detection circuit 8 that detects the voltage (voltage drop) of the current detection wiring 3. Yes. That is, the main voltage detection circuit 8 is connected to the current detection wiring 3 so as to detect a voltage between the lengths L1 of the current detection wiring 3.

  Further, in addition to the current detection wiring 3, a correction circuit 9 for correcting the voltage between the lengths L <b> 1 detected by the main voltage detection circuit 8 is formed on the substrate body 2. The correction circuit 9 has a configuration in which a correction wiring 11 is connected to a constant current source 10. The constant current source 10 is a power supply circuit that includes a transistor or the like and can stably supply a current smaller than that of the current detection wiring 3. The correction wiring 11 has a line width W2 that is sufficiently narrower than the line width W1 of the current detection wiring 3. The correction wiring 11 is a printed wiring formed at the same time as the current detection wiring 3, and the thickness of the correction wiring 11 and the current detection wiring 3 is substantially the same. For this reason, the resistance per unit length of the correction wiring 11 is larger than the resistance per unit length of the current detection wiring 3.

Further, the straight line portion 11a which is a part of the correction wiring 11 is disposed in the vicinity of the straight line portion 3a to which the main voltage detection circuit 8 is connected in the current detection wiring 3. The two wirings 12 and 13 are connected to the straight line portion 11a with an interval of a length L2. The wirings 12 and 13 are connected to a correction voltage detection circuit 14 that detects a voltage drop between the length L2 of the correction wiring 9.
The length L2 is longer than the length L1 for detecting the voltage drop of the current detection wiring 3. Further, in the correction wiring 11, the location where the wirings 12 and 13 are connected is closer to the lead wire 4 than the connection location of the wiring 6 when viewed from the current detection wiring 3 arranged oppositely. Similarly, the location where the wiring 14 is connected is closer to the lead wire 5 than the location where the wiring 7 is connected, as viewed from the current detection wiring 3 arranged oppositely. That is, the wirings 6 and 7 are installed in a range sandwiched between positions adjacent to the wirings 12 and 13 on the correction wiring 11 side.

The detection value of the voltage drop of the length L1 of the current detection wiring 3 and the detection value of the voltage drop of the length L2 of the correction wiring 11 are output to a control device including a microcomputer (not shown). This control device is mounted on, for example, a circuit that supplies current to the main circuit. At least the main voltage detection circuit 8, the correction voltage detection circuit 14, and the constant current source 10 are connected to the control device, and a circuit (not shown) for controlling the current flowing through the other main circuits is also connected.
Here, the control device is programmed to calculate the current flowing through the current detection wiring 3 by multiplying the ratio of the voltage V2 of the main voltage detection circuit 8 to the voltage V1 of the correction voltage circuit 14 by a predetermined constant C1. ing. That is, the calculation formula of the current I1 is as shown in the following formula 1.

  The constant C1 includes the length L1 and the wiring width W1 for detecting the voltage drop in the current detection wiring 3, the length L2 and the distribution width W2 for detecting the voltage drop in the correction wiring 11, and the current of the constant current source 10. It is represented by the value I2. This is obtained by multiplying a value obtained by dividing the resistance of the current detection wiring 3 by the resistance of the correction wiring 11 having the same thickness with the same conductive material by the constant current source I2. That is, the value obtained by dividing the constant C1 by the voltage V2 in Equation 1 corresponds to the resistance value of the current detection wiring 3 corrected by the correction circuit 9. Note that the value of the constant C may be stored in a memory connected to the control device. Further, the lengths L1 and L2, the line widths W1 and W2, and the current I2 may be stored in the memory instead of the constant C1.

Next, the operation of this embodiment will be described. The circuit board here is described as a circuit board that is inserted between a motor and a driver circuit that supplies the motor, and is used to feed back the current flowing through the motor to the driver circuit.
When rotating the motor, the driver supplies a current to the motor based on an externally input signal. The current supplied to the motor flows from the lead wire 4 of FIG. 1 through the current detection wiring 3 to the lead wire 5 and is supplied to the motor.

When a current flows through the current detection wiring 3, a voltage drop during the length L 1, that is, the voltage V 2 is detected by the main voltage detection circuit 8.
At the same time, the constant current source 10 of the correction circuit 9 causes the current I2 to flow through the correction wiring 11 in accordance with a command from the control device. Thereby, the correction voltage detection circuit 14 detects the voltage drop during the length L1, that is, the voltage V1.
The control device calculates the current I1 flowing through the current detection wiring 3 by multiplying the ratio of the voltage V1 and the voltage V2 by a constant C1 according to the above-described equation 1. Based on the current I1 thus detected, the current supplied to the motor is controlled by the driver circuit.

According to this embodiment, since the substrate body 2 is made of a material having high thermal conductivity, temperature unevenness hardly occurs. Furthermore, since the current detection wiring 3 and the correction wiring 11 are arranged close to each other, the temperatures of the two wirings 3 and 11 can be regarded as the same. Therefore, if the resistance value of the current detection wiring 3 is corrected using the information of the correction wiring 11, a correct current value can be obtained even if the temperature changes.
Since the wirings 3 and 11 are printed wirings of the same conductive material, the thicknesses thereof are substantially the same. Therefore, the variation in the current value I1 generated for each circuit board 1 due to the variation in the thickness of the current detection wiring 3 can also be prevented. Since the material and thickness are the same, the current value I1 can be easily obtained simply by multiplying the voltage ratio by a constant with the voltages V1 and V2 as variables as shown in Equation 1. Here, since the correction wiring 11 is a wiring having a large resistance value, the energization of the constant current I2 can be stabilized, and the detection accuracy of the current value I1 is high.
In addition, by detecting the current value I1 with high accuracy in this way, current control of the main circuit such as a motor can be performed with high accuracy.

The present invention is not limited to the above-described embodiment, and can be widely applied.
For example, a temperature sensor may be arranged as a correction circuit in the vicinity of the current detection wiring 3 on the substrate body 2. In this case, before the circuit board 1 is shipped, a constant current is passed through the current detection wiring 3 in an environment controlled at a predetermined temperature to calibrate the variation in the thickness of the copper wiring. Further, the calibration value is stored in a non-volatile memory connected to the control device. Also, resistance correction values that differ for each temperature are stored in the memory. When the current actually flowing through the circuit board 1 is detected, the voltage drop of the current detection wiring 3 is detected, the temperature of the board body 2 is detected by the temperature sensor, and the correction stored in the memory is detected. The current value I1 is calculated using the value. According to this circuit board 1, even when the temperature changes, it is possible to detect the current value with high accuracy with a simple configuration.

  Further, the current detection wiring 3 is not limited to a linear shape and can be formed in an arbitrary shape. Further, the correction wiring 11 may be formed on a cover fixed to the substrate body 2 so as to cover the current detection wiring 3. If the cover is made of a material having a high heat transfer coefficient, the temperature of the substrate main body 2 and the temperature of the cover become substantially the same, and the same effect as in the above embodiment can be obtained.

It is a figure which shows the circuit board in embodiment of this invention.

Explanation of symbols

2 Substrate body 3 Current detection wiring 8 Main voltage detection circuit (voltage detection circuit)
9 Correction Circuit 10 Constant Current Source 11 Correction Wiring 14 Correction Voltage Detection Circuit W1 Line Width W2 Line Width

Claims (6)

  A current detection wiring for detecting a current flowing in the main circuit is formed on the substrate body, a voltage detection circuit for detecting a voltage drop in the current detection wiring is connected to the current detection wiring, and the current detection wiring A circuit board comprising a correction circuit for correcting a detected value of a voltage drop of the current detection wiring detected by the voltage detection circuit at a position close to the wiring.   The correction circuit includes a correction voltage detection circuit that forms the correction wiring connected to a constant current source in the vicinity of the current detection wiring and detects a voltage drop in the correction wiring. The circuit board according to claim 1.   The circuit board according to claim 2, wherein the current detection wiring and the correction wiring are printed wirings and have substantially the same thickness.   The circuit board according to claim 3, wherein a line width of the correction wiring is narrower than a line width of the voltage detection wiring.   The circuit board according to any one of claims 1 to 4, wherein the substrate body is a metal substrate using a metal material. The current flowing through the main circuit is supplied to the current detection wiring, a voltage drop in the current detection wiring is detected, and a constant current is supplied to the correction wiring provided close to the current detection wiring. A current detection that detects a voltage drop in the wiring and obtains a current value that does not depend on a temperature change as a current value that flows in the main circuit from each voltage drop in the current detection wiring and the correction wiring. Method.

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