Current detection device and power supply control device

Abstract

A current detection device detects a current flowing through a power supply path of a power supply control device, wherein the power supply path includes a first conductor and a second conductor, and further includes: a first shunt resistor and a second shunt resistor connected in parallel between the first conductor and the second conductor; a current detection circuit that detects a current flowing through the first shunt resistor; a current that flows from the first conductor to the second conductor via both the first shunt resistor and the second shunt resistor; and an operation circuit. The operation circuit calculates the current flowing through the power supply path based on a correlation between a current flowing from the first conductor to the second conductor via both the first shunt resistor and the second shunt resistor and a current flowing through the first shunt resistor and a current detected by the current detection circuit.

Description

Technical Field

[0001] The present disclosure relates to a current detection device and a power supply control device.

[0002] This application claims the benefit of priority based on Japanese Application No. 2019-085995, filed on April 26, 2019, and all the contents described in the above Japanese Application are incorporated herein by reference. Background Art

[0003] The vehicle is equipped with a power supply control device that controls the power supply from the battery to the load. The power supply control device has semiconductor switching elements such as power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) connected to the power supply path, and performs power supply control through PWM (Pulse Width Modulation) control of the semiconductor switching element. In addition, the power supply control device has a current detection device that detects the current of the power supply path. The current detection circuit has a shunt resistor connected in series with the semiconductor switching element, and can detect the current of the power supply path from the voltage across the shunt resistor.

[0004] The power supply control device disconnects the semiconductor switch element to protect the device from overcurrent when the voltage drop generated by the shunt resistor reaches a predetermined threshold or more. In addition, the power supply control device estimates the wire temperature based on the current value detected by the current detection circuit and the power-on time, and disconnects the semiconductor switch element to protect the wire when the estimated wire temperature reaches a predetermined threshold or more.

[0005] Prior art literature

[0006] Patent Document 1: Japanese Patent Application No. 2017-122781 Summary of the invention

[0007] The present method relates to a current detection device, which detects the current flowing through a power supply path of a power supply control device, wherein the power supply path includes a first conductor and a second conductor, and the current detection device further includes: a first shunt resistor and a second shunt resistor, which are connected in parallel between the first conductor and the second conductor; a current detection circuit, which detects the current flowing through the first shunt resistor; and an operation circuit, which calculates the current flowing through the power supply path based on the correlation between the current flowing from the first conductor to the second conductor via the first shunt resistor and the second shunt resistor and the current flowing through the first shunt resistor, and the current detected by the current detection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a circuit block diagram showing a configuration example of the power supply control device according to the first embodiment.

[0009] Figure 2 It is a schematic diagram showing a configuration example of a current detection device according to the first embodiment.

[0010] Figure 3 This is a circuit block diagram showing a configuration example of a current detection device according to the first embodiment.

[0011] Figure 4 It is a schematic diagram showing a configuration example of a current detection device according to the second embodiment.

[0012] Figure 5A This is a circuit diagram showing a part of a current detection device according to a modification example.

[0013] Figure 5B This is a circuit diagram showing a part of a current detection device according to a modification. DETAILED DESCRIPTION

[0014] [Problems to be Solved by the Present Disclosure]

[0015] When a vehicle is equipped with a large number of loads or the power consumed by the loads increases, there is a technical problem that the current flowing through the power supply path increases and the heat generated by the shunt resistor also increases. It is also conceivable to use multiple shunt resistors in parallel so that the temperature of the shunt resistor does not exceed the heat-resistant temperature, but it is necessary to set a current detection circuit for each shunt resistor, resulting in an increase in the number of components, an increase in the circuit mounting area on the substrate, and an increase in calculation processing.

[0016] An object of the present disclosure is to provide a current detection device and a power supply control device that can detect a larger current that cannot be detected by a single shunt resistor by providing only one current detection circuit for a plurality of shunt resistors connected in parallel.

[0017] [Effects of the present disclosure]

[0018] According to the present disclosure, it is possible to provide a current detection device and a power supply control device that can detect a large current that cannot be detected by a single shunt resistor by providing only one current detection circuit for a plurality of shunt resistors connected in parallel.

[0019] [Description of Embodiments of the Invention]

[0020] First, the embodiments of the present disclosure will be described by way of examples. In addition, at least a part of the embodiments described below may be arbitrarily combined.

[0021] (1) The present method relates to a current detection device for detecting a current flowing through a power supply path of a power supply control device, the power supply path comprising a first conductor and a second conductor, the current detection device further comprising: a first shunt resistor and a second shunt resistor connected in parallel between the first conductor and the second conductor; a current detection circuit for detecting a current flowing through the first shunt resistor; and an operation circuit for calculating a current flowing through the power supply path based on a correlation between a current flowing from the first conductor to the second conductor via the first shunt resistor and the second shunt resistor and a current flowing through the first shunt resistor and a current detected by the current detection circuit.

[0022] According to this embodiment, the current flowing through the first conductor and the second conductor constituting the power supply path is divided and flows to the first shunt resistor and the second shunt resistor. The current detection circuit is provided in the first shunt resistor to detect the current flowing in the first shunt resistor. The current detection circuit is not provided in the second shunt resistor.

[0023] The current flowing through the first shunt resistor and the current flowing through the second shunt resistor are biased when there is a difference in the resistance value of their respective current paths. The calculation circuit calculates the current flowing through the power supply path based on the correlation between the current flowing through the power supply path and the current flowing through the first shunt resistor and the current of the first shunt resistor.

[0024] In addition, the number of shunt resistors in this embodiment is not limited to two.

[0025] (2) It is preferable that a shunt ratio of current flowing through a first path of the power supply path via the first shunt resistor is smaller than a shunt ratio of current flowing through a second path of the power supply path via the second shunt resistor.

[0026] (3) It is preferable that a path resistance of a first path through which current flows through the power supply path via the first shunt resistor is larger than a path resistance of a second path through which current flows through the power supply path via the second shunt resistor.

[0027] (4) It is preferable that a first path through which current flows through the power supply path via the first shunt resistor is longer than a second path through which current flows through the power supply path via the second shunt resistor.

[0028] According to this aspect, the current flowing through the power supply path of the power supply control device is divided into the two paths, and the current flowing through the first path is smaller than the current flowing through the second path.

[0029] When the calculation circuit calculates the current flowing through the power supply path by setting the ratio of the currents flowing through the two paths to 50:50, the current flowing through the power supply path is calculated as a relatively small value.

[0030] When the arithmetic circuit controls the semiconductor switch element that cuts off the power supply path to turn off when determining that the current flowing through the power supply path is equal to or greater than a predetermined threshold, the above aspect can prevent the power supply path from being erroneously cut off.

[0031] (5) It is preferable that the distance between the first shunt resistor and the second shunt resistor be 5 mm or less.

[0032] According to this embodiment, since the distance between the first shunt resistor and the second shunt resistor is less than 5 mm, the current flowing through the first shunt resistor and the current flowing through the second shunt resistor can be suppressed, and the calculation circuit can calculate the current flowing through the power supply path with higher accuracy.

[0033] The resistance values ​​of the first shunt resistor and the second shunt resistor are, for example, not less than 0.5 mΩ and not more than 10 mΩ, and the resistance values ​​of the first conductor and the second conductor are smaller than the resistance values ​​of the first shunt resistor and the second shunt resistor.

[0034] (6) This aspect relates to a power supply control device including a current detection device according to any one of aspects (1) to (5).

[0035] According to this aspect, it is possible to perform power supply control of a large current flowing through the power supply path via the first and second shunt resistors connected in parallel.

[0036] [Description of Embodiments of the Present Disclosure]

[0037] Specific examples of the current detection device and the power supply control device according to the embodiments of the present disclosure are described below with reference to the drawings. The present invention is not limited to these examples but is indicated by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0038] Hereinafter, the present disclosure will be described in detail based on the drawings showing embodiments thereof.

[0039] (Implementation Method 1)

[0040] Figure 11 is a circuit block diagram showing a configuration example of a power supply control device according to Embodiment 1. The power supply control device according to Embodiment 1 is a device that controls the power supply from a vehicle-mounted storage battery (not shown) to a load A. The power supply control device includes: a microcomputer (calculation circuit) 1, a drive circuit 2, a semiconductor switch element 3, a shunt resistor 4, a current detection circuit 5, and a power supply path 6. The microcomputer 1, the shunt resistor 4, and the current detection circuit 5 constitute a current detection device 101 according to Embodiment 1.

[0041] The power supply path 6 is a conductor that supplies power from the vehicle-mounted battery to the load A, and includes a first conductor 61, a second conductor 62, and a third conductor 63 connected in series. The first conductor 61, the second conductor 62, and the third conductor 63 are, for example, flat-plate-shaped conductors. The first conductor 61 is connected to the second conductor 62 via the shunt resistor 4. In addition, the first conductor 61 is connected to the third conductor 63 via the semiconductor switch element 3. The third conductor 63 is connected to the positive terminal of the vehicle-mounted battery, and the second conductor 62 is connected to the positive terminal of the load A.

[0042] The semiconductor switch element 3 is, for example, an N-channel power MOSFET. The drain of the semiconductor switch element 3 is connected to the third conductor 63, and the source is connected to the first conductor 61. That is, the drain of the semiconductor switch element 3 is connected to the positive terminal side of the vehicle battery via the third conductor 63, and the source is connected to the positive terminal of the load A via the first conductor 61. The negative terminal of the vehicle battery and the negative terminal of the load A are grounded.

[0043] The drive circuit 2 is connected to the gate of the semiconductor switch element 3. The drive circuit 2 turns the semiconductor switch element 3 on or off based on a PWM signal supplied from the microcomputer 1.

[0044] The shunt resistor 4 includes a first shunt resistor 41 and a second shunt resistor 42 connected in parallel between a first conductor 61 and a second conductor 62. Specifically, one end of the first shunt resistor 41 is connected to the first conductor 61, and the other end of the first shunt resistor 41 is connected to the second conductor 62. Similarly, one end of the second shunt resistor 42 is connected to the first conductor 61, and the other end of the second shunt resistor 42 is connected to the second conductor 62. The first shunt resistor 41 and the second shunt resistor 42 are, for example, not less than 0.5 mΩ and not more than 10 mΩ.

[0045] The current detection circuit 5 is a circuit that detects the current flowing through the first shunt resistor 41 by detecting the voltage across both ends of the first shunt resistor 41, and outputs a voltage corresponding to the current to the microcomputer 1. The power supply control device involved in this embodiment 1 has a single current detection circuit 5, and the single current detection circuit 5 is provided on the first shunt resistor 41 side.

[0046] An example of the current detection circuit 5 is described. The current detection circuit 5 includes a differential amplifier 51, which constitutes an inverting amplifier circuit. The non-inverting input terminal of the differential amplifier 51 is connected to the negative end of the first shunt resistor 41. The inverting input terminal of the differential amplifier 51 is connected to the positive end of the first shunt resistor 41 via a resistor 52. The output terminal of the differential amplifier 51 is grounded and connected to the inverting input terminal via a resistor 53, and negative feedback is performed. The voltage output from the output terminal of the differential amplifier 51 is equivalent to the value of the current flowing in the power supply path 6, and is input to the microcomputer 1.

[0047] Figure 2 is a schematic diagram showing a configuration example of a current detection device 101 according to Embodiment 1. Figure 3 1 is a circuit block diagram showing a configuration example of the current detection device 101 involved in Embodiment 1. The first path R1 in which the current flows through the above-mentioned power supply path 6 via the first shunt resistor 41 is a circuit structure that is longer than the second path R2 in which the current flows through the power supply path 6 via the second shunt resistor 42. In other words, the first path R1 is a path with a smaller current diversion ratio than the second path R2, and the current Is1 and the current Is2 flow in a biased manner. In addition, the path resistance of the first path R1 can also be said to be greater than the path resistance of the second path R2.

[0048] The first path R1 is generally a path connecting the inflow point 61a where the current flows into the first conductor 61, the first shunt resistor 41, and the outflow point 62a where the current flows out from the second conductor 62. Figure 3 As shown, the path is represented by the resistor 61 b ​​of the first conductor 61 , the first shunt resistor 41 , and the resistor 62 b of the second conductor 62 .

[0049] The second path R2 is generally a path connecting the inflow point 61a, the second shunt resistor 42 and the outflow point 62a. Figure 3 As shown, the path is represented by the resistor 61 c of the first conductor 61 , the second shunt resistor 42 , and the resistor 62 c of the second conductor 62 .

[0050] The current Is flowing into the inflow point 61a is divided into the current Is1 flowing through the first path R1 and the current Is2 flowing through the second path R2. The resistor 61b is larger than the resistor 61c, and the resistor 62b is larger than the resistor 62c. Therefore, the current Is1 flowing through the first path R1 is smaller than the current Is2 flowing through the second path R2. In other words, the current Is1 and the current Is2 are biased.

[0051] When the bias current is too large, the heat generation on the side where the current flows more increases, and the current that can be supplied decreases. Therefore, in order to reduce the bias current as much as possible, the following configuration is preferably used.

[0052] The first shunt resistor 41 and the second shunt resistor 42 preferably have substantially the same resistance value. In addition, it is preferred that the distance between the first shunt resistor 41 and the second shunt resistor 42 is, for example, less than 5 mm. In addition, it is preferred that the first shunt resistor 41 and the second shunt resistor 42 are arranged in parallel. Specifically, the following configuration is preferred: the first shunt resistor 41 and the second shunt resistor 42 are configured in a flat, substantially rectangular shape, so that the long sides of the first shunt resistor 41 and the second shunt resistor 42 are substantially parallel, and the short sides of the first shunt resistor 41 and the second shunt resistor 42 are set to be flush with the plane.

[0053] In addition, if Figure 2 and Figure 3 As shown, it is preferable that the current detection circuit 5 is provided on the side of the first shunt resistor 41 having a longer path. Using the first shunt resistor 41 having a longer path for current flow can increase the current detection accuracy and prevent erroneous control of the microcomputer 1.

[0054] The microcomputer 1 includes a storage unit 11, which stores a correlation between a current Is=Is1+Is2 flowing from the first conductor 61 to the second conductor 62 via the first shunt resistor 41 and the second shunt resistor 42 and a current Is1 flowing through the first shunt resistor 41. The correlation is, for example, a ratio of the current Is to the current Is1 (=Is / Is1). The microcomputer 1 calculates the current Is flowing through the power supply path 6 based on the correlation stored in the storage unit 11 and the current Is1 detected by the current detection circuit 5.

[0055] When the microcomputer 1 determines that the current Is flowing in the power supply path 6 is greater than a predetermined threshold, the microcomputer 1 outputs a cutoff signal to the drive circuit 2 to turn off the semiconductor switch element 3. In addition, the microcomputer 1 estimates the temperature of the wire connecting the vehicle battery and the load A based on the current Is and the power-on time, and when the estimated wire temperature reaches a predetermined threshold or greater, the semiconductor switch element 3 is turned off to protect the wire.

[0056] Furthermore, the microcomputer 1 performs PWM control on the power supply to the load A by outputting a PWM signal to the drive circuit 2 to turn on or off the semiconductor switch element 3 .

[0057] The drive circuit 2 drives the semiconductor switch element 3 to turn on by increasing the voltage of the gate of the semiconductor switch element 3 with reference to the ground potential.

[0058] According to the current detection device 101 and the power supply control device according to the first embodiment configured in this way, only one current detection circuit 5 is provided for the first shunt resistor 41 and the second shunt resistor 42 connected in parallel, thereby being able to detect a large current that cannot be detected by a single shunt resistor.

[0059] In addition, a current detection circuit 5 is provided on the side of the first shunt resistor 41 where the path through which the first conductor 61 and the second conductor 62 flow is longer, and the microcomputer 1 calculates the current flowing through the power supply path 6 by setting the ratio of the current Is1 flowing through the first path R1 to the current Is2 flowing through the second path R2 to 50:50. In the case of such a configuration, since the current flowing through the power supply path 6 is calculated as a relatively small value, erroneous disconnection due to overcurrent can be prevented.

[0060] In the first embodiment, the current detection circuit 5 can also be provided for the second shunt resistor 42 .

[0061] In addition, by adopting a structure that suppresses bias current, such as making the distance between the first shunt resistor 41 and the second shunt resistor 42 less than 5 mm, the current can be detected with higher accuracy and power supply control can be performed. In addition, by suppressing bias current, the current can be shunted to the first shunt resistor 41 and the second shunt resistor 42 with good balance, and a larger current can be controlled.

[0062] (Implementation Method 2)

[0063] Figure 4 1 is a schematic diagram showing a configuration example of a current detection device 101 according to Embodiment 2. The current detection device 101 and the power supply device according to Embodiment 2 are different from Embodiment 1 in that they include a first semiconductor switch element 31 and a second semiconductor switch element 32 connected in parallel, so the following mainly describes the above difference. Since the other structures and effects are the same as those in Embodiment 1, the same figure marks are marked for the corresponding parts and detailed description is omitted.

[0064] Arranged on the substrate B are a first conductor 61 , a second conductor 62 , a third conductor 63 , a first semiconductor switch element 31 , a second semiconductor switch element 32 , a first shunt resistor 41 , a second shunt resistor 42 , a microcomputer 1 , and a current detection circuit 5 .

[0065] The semiconductor switch element 3 includes a first semiconductor switch element 31 and a second semiconductor switch element 32 connected in parallel between a first conductor 61 and a third conductor 63. The first conductor 61 has two separate conductor portions 611a and 611b. The source of the first semiconductor switch element 31 is connected to the first conductor portion 611a, and the source of the second semiconductor switch element 32 is connected to the second conductor portion 611b. The first shunt resistor 41 is connected to the first conductor portion 611a, and the second shunt resistor 42 is connected to the second conductor portion 611b.

[0066] According to the second embodiment, the arrangement freedom of the first semiconductor switch element 31 and the second semiconductor switch element 32 is high, bias current can be suppressed, and the current flowing through the power supply path 6 can be calculated with higher accuracy.

[0067] (Variation Example)

[0068] Figure 5A and Figure 5B 1 is a circuit diagram showing a part of a current detection device 101 according to a modification.

[0069] In the structure involved in the second embodiment, Figure 5A As shown, it is also possible to use a conductor to connect the source of the first semiconductor switch element 31 and the source of the second semiconductor switch element 32. In this case, it is possible to more effectively suppress the bias between the current flowing through the first shunt resistor 41 and the current flowing through the second shunt resistor 42. In addition, heat can be dissipated from the conductor, and a structure with excellent heat dissipation can be formed.

[0070] like Figure 5B As shown, the first shunt resistor 41 and the second shunt resistor 42 may be connected to the positive side, and the first semiconductor switch element 31 and the second semiconductor switch element 32 may be connected to the negative side. Specifically, the first conductor 61 is connected to the positive terminal of the vehicle battery, and the first conductor 61 and the second conductor 62 are connected via the first shunt resistor 41 and the second shunt resistor 42. The second conductor 62 and the third conductor 63 are connected via the first semiconductor switch element 31 and the second semiconductor switch element 32, and the third conductor 63 is connected to the positive terminal of the load A.

[0071] In the modification, the power supply control device and the current detection device 101 also have the same functions and effects as those of the first and second embodiments.

[0072] Description of Reference Numerals

[0073] 1 Microcomputer

[0074] 2. Driving Circuit

[0075] 3 Semiconductor switching elements

[0076] 5 Current Detection Circuit

[0077] 6 Power supply path

[0078] 11 Storage

[0079] 31 first semiconductor switching element

[0080] 32 second semiconductor switch element

[0081] 41 First shunt resistor

[0082] 42 Second shunt resistor

[0083] 51 Differential Amplifier

[0084] 61 First Conductor

[0085] 611a First conductor part

[0086] 611b Second conductor part

[0087] 62 Second conductor

[0088] 63 Third conductor

[0089] 101 Current detection device

[0090] A Load

[0091] B substrate

[0092] R1 First Path

[0093] R2 Second path.

Claims

1. A current detection device for detecting a current flowing through a power supply path of a power supply control device, The power supply path includes a third conductor, a first conductor, and a second conductor which are connected in sequence and are arranged in a flat plate shape on the substrate. The current detection device further comprises: A first semiconductor switch element and a second semiconductor switch element are connected in parallel between the first conductor and the third conductor disposed on the substrate; A first shunt resistor and a second shunt resistor are disposed on the substrate and connected in parallel between the first conductor and the second conductor; a current detection circuit, disposed on the substrate, for detecting the current flowing through the first shunt resistor; and an operation circuit, arranged on the substrate, The calculation circuit calculates the current flowing through the power supply path based on the correlation between the current flowing from the first conductor to the second conductor via both the first shunt resistor and the second shunt resistor and the current flowing through the first shunt resistor and the current detected by the current detection circuit. A first path through which current flows through the power supply path via the first shunt resistor is longer than a second path through which current flows through the power supply path via the second shunt resistor.

2. The current detection device according to claim 1, wherein: The shunt ratio of the current flowing through the first path of the power supply path via the first shunt resistor is smaller than the shunt ratio of the current flowing through the second path of the power supply path via the second shunt resistor.

3. The current detection device according to claim 1, wherein: A path resistance of a first path through which current flows through the power supply path via the first shunt resistor is greater than a path resistance of a second path through which current flows through the power supply path via the second shunt resistor.

4. The current detection device according to claim 2, wherein: A path resistance of a first path through which current flows through the power supply path via the first shunt resistor is greater than a path resistance of a second path through which current flows through the power supply path via the second shunt resistor.

5. The current detection device according to any one of claims 1 to 4, wherein: The distance between the first shunt resistor and the second shunt resistor is less than 5 mm. 6 . A power supply control device comprising the current detection device according to claim 1 .

Images