Current control device

Abstract

To provide a current control device, capable of protecting wires from sudden changes in current with a simple configuration including relatively few components and with a relatively small mounting area.SOLUTION: There is provided a current control device that controls supply current supplied to a load from a power source via a wire. The current control device includes: a switch part which flows the supply current in an on-state and interrupts the supply current in an off-state; a temperature characteristics simulation part into which first current according to the supply current is input and which simulates temperature characteristics of the wire such that, according to the first current, a first voltage signal according to a temperature difference between a wire temperature of the wire and an environmental temperature of the wire is output; a current generation part into which second current according to the supply current and which generates third current according to the second current, by a magnetic field generated by the second current; and a drive part which controls the switch part to an off-state when the voltage of the first voltage signal is equal to or more than a first voltage threshold or when the third current is equal to or more than a first current threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current control device. [Background Art]

[0002] There is known a technology that calculates the wire temperature of an electric wire based on the wire current flowing through the electric wire, and cuts off the energization of current through the electric wire when the calculated wire temperature reaches or exceeds a predetermined temperature. According to this technology, the wire temperature can be prevented from rising to an abnormal temperature, so the electric wire can be protected. Further, a power supply control device that can prevent the wire temperature from rising to an abnormal temperature without calculating the wire temperature is disclosed (Patent Document 1). According to this power supply control device, by using a temperature difference circuit that outputs a higher voltage as the temperature difference between the wire temperature of the electric wire and the environmental temperature around the electric wire increases, it is possible to prevent the wire temperature from rising to an abnormal temperature without calculating the wire temperature using an expensive microcontroller with high processing capacity. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2022-80105 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] However, the temperature difference circuit as disclosed in Patent Document 1 cannot follow a steep current change such as when a large current suddenly flows through the electric wire due to a short circuit or the like. Therefore, the power supply control device disclosed in Patent Document 1 is provided with a circuit (second current output circuit) for cutting off the current at a predetermined current threshold, for example, to protect a switch or the like used for cutting off the current.

[0005] However, the second current circuit described above has a relatively complex configuration, which presents challenges such as a large number of components and a large area required for implementation.

[0006] The present invention has been made in view of the above, and aims to provide a current control device that can protect electric wires from sudden current changes with a relatively simple configuration with a relatively small number of components and a relatively small mounting area. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, one aspect of the present invention is a current control device for controlling a supply current supplied from a power source to a load via an electric wire, comprising: a switch unit that allows the supply current to flow when it is ON and cuts off the supply current when it is OFF; a temperature characteristic simulation unit that receives a first current corresponding to the supply current and simulates the temperature characteristics of the electric wire by outputting a first voltage signal corresponding to the temperature difference between the electric wire temperature and the ambient temperature of the electric wire according to the first current; a current generation unit that receives a second current corresponding to the supply current and generates a third current corresponding to the second current using a magnetic field generated by the second current; and a drive unit that controls the switch unit to an OFF state when the voltage of the first voltage signal is equal to or greater than a first voltage threshold or when the third current is equal to or greater than a first current threshold.

[0008] The second current may be at least a portion of the supply current or at least a portion of the first current.

[0009] The current generating unit may include a common mode choke coil.

[0010] The current generating unit may include a first conductor into which the second current is input, and a second conductor provided adjacent to the first conductor through which the third current flows.

[0011] The current generating unit may include a substrate on which the first conductor and the second conductor are formed as a conductor pattern. [Effects of the Invention]

[0012] According to the present invention, a current control device that protects wires from sudden current changes can be realized with a relatively small number of components, a simple configuration, and a relatively small mounting area. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a block diagram showing the configuration of an electrical device equipped with a current control device according to Embodiment 1. [Figure 2] Figure 2 is a time chart showing an example of the operating characteristics of the current control device shown in Figure 1. [Figure 3] Figure 3 is a graph showing the supply current interruption characteristics of the current control device shown in Figure 1. [Figure 4] Figure 4 is a block diagram showing the configuration of an electrical device equipped with a current control device according to Embodiment 2. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below. Furthermore, in the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and redundant explanations are omitted as appropriate.

[0015] (Embodiment 1) Figure 1 is a block diagram showing the configuration of an electrical device equipped with a current control device according to Embodiment 1. The electrical device 1000 comprises a current control device 100 according to Embodiment 1, a power supply 200, an electric wire 300, and a load 400.

[0016] The electrical device 1000 is mounted in, for example, a vehicle. The power source 200 is, for example, a battery mounted in a vehicle. A current output from the power source 200 is supplied to the load 400 via the current control device 100 and further via the electric wire 300. The electric wire 300 is a power feeding electric wire included in, for example, a wire harness mounted in a vehicle. The load 400 is, for example, an electrical device mounted in a vehicle, and operates by a supply current supplied from the power source 200.

[0017] The current control device 100 controls a supply current supplied to the load 400. As shown in FIG. 1, the current control device 100 includes a main line 1, a switch unit 2, a drive unit 3, a control unit 4, a switch temperature detection unit 5, a current output unit 6, a diode 7, a current generation unit 8, a resistance unit 9, a temperature characteristic simulation unit 10, a comparison unit 11, and a reference voltage generation unit 12.

[0018] The main line 1 electrically connects the power source 200 and the electric wire 300, and is formed of, for example, an electric wire containing a conductor. A supply current Is supplied to the load 400 flows through the main line 1.

[0019] The switch unit 2 is provided midway along the main line 1. The switch unit 2 allows the supply current Is to flow when in an on state, and interrupts the supply current Is when in an off state. The switch unit 2 includes, for example, a semiconductor switching element. The semiconductor switching element is, for example, an FET (Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor).

[0020] The drive unit 3 switches the operating state of the switch unit 2 between an on state and an off state. The drive unit 3 is configured of, for example, an analog circuit, and outputs a drive signal to the switch unit 2 to set the operating state of the switch unit 2 to an on state or an off state based on a control signal input from the control unit 4. The drive signal is, for example, a voltage signal applied to a gate terminal of the switch unit 2.

[0021] Further, as will be described later, the drive unit 3 outputs, to the switch unit 2, a drive signal for turning the operating state of the switch unit 2 to an on state or an off state based on voltage signals input from the switch temperature detection unit 5, the resistor unit 9, and the comparison unit 11.

[0022] The control unit 4 includes, for example, a microcontroller. When the supply current Is is caused to flow through the load 400 to operate the load 400, the control unit 4 outputs, to the drive unit 3, a control signal for turning the switch unit 2 to an on state. Further, when the supply current Is to the load 400 is cut off to stop the operation of the load 400, the control unit 4 outputs, to the drive unit 3, a control signal for turning the switch unit 2 to an off state.

[0023] The switch temperature detection unit 5 is provided in the vicinity of the switch unit 2. The switch temperature detection unit 5 outputs, to the drive unit 3, a voltage signal corresponding to the temperature of the switch unit 2. For example, the voltage value of the voltage signal output by the switch temperature detection unit 5 increases as the temperature of the switch unit 2 increases. The switch temperature detection unit 5 is constituted by an analog circuit including, for example, a thermistor.

[0024] The current output unit 6 is connected to the main line 1. The current output unit 6 outputs, to the diode 7, a current corresponding to the supply current Is flowing through the main line 1. For example, the current output by the current output unit 6 increases as the supply current Is increases. The current output unit 6 is constituted by, for example, an analog circuit, and may be configured like the first current circuit described in Patent Document 1.

[0025] The diode 7 causes current to flow from the current output unit 6 to the temperature characteristic simulation unit 10 via the current generation unit 8, and prevents current from flowing backward from the temperature characteristic simulation unit 10 side to the current output unit 6.

[0026] The current generation unit 8 comprises a primary coil 8a and a secondary coil 8b. One end of the primary coil 8a is connected to the diode 7, and the other end of the primary coil 8a is connected to the temperature characteristic simulation unit 10. One end of the secondary coil 8b is connected to the resistor 9, and the other end of the secondary coil 8b is connected to ground. In this embodiment, the current generation unit 8 includes a common mode choke coil.

[0027] When the current input from diode 7 flows through the primary coil 8a, a mutually induced electromotive force is generated by the magnetic field created by this current. This mutually induced electromotive force generates a current in the secondary coil 8b, which then flows through the secondary coil 8b. In other words, the current generation unit 8 is an example of a current generation unit that receives a second current corresponding to the supply current Is, and generates a third current corresponding to the second current due to the magnetic field generated by the second current. The current input from diode 7 is an example of the second current, and the current generated in the secondary coil 8b is an example of the third current. For example, the second current is larger as the supply current Is increases, and the third current is larger as the temporal change of the second current increases.

[0028] One end of the resistor 9 is connected to one end of the secondary coil 8b, and the other end of the resistor 9 is connected to ground. The connection point between the resistor 9 and the secondary coil 8b is connected to the drive unit 3. When the current generated in the secondary coil 8b flows through the resistor 9, the drive unit 3 receives a voltage signal corresponding to that current and the resistance value of the resistor 9.

[0029] The temperature characteristic simulation unit 10 is connected to the current generation unit 8. Based on the current input through the diode 7 and the current generation unit 8, the temperature characteristic simulation unit 10 simulates the temperature characteristics when a supply current Is flows through the wire 300, and outputs a voltage signal to the comparison unit 11 corresponding to the temperature difference between the wire temperature of the wire 300 and the ambient temperature of the wire 300. The temperature characteristic simulation unit 10 is an example of a temperature characteristic simulation unit that simulates the temperature characteristics of the wire 300 by receiving a first current corresponding to the supply current Is and outputting a first voltage signal corresponding to the temperature difference between the wire temperature of the wire 300 and the ambient temperature of the wire 300 in accordance with the first current.

[0030] The temperature characteristic simulation unit 10 can be constructed using an analog circuit employing a thermal model. Such a circuit is also called a thermal equivalent circuit. In a thermal equivalent circuit, the thermal resistance of the wire 300 is represented by electrical resistance, and the thermal capacitance is represented by a capacitor. For example, a Cauer type or a Foster type can be used as the thermal equivalent circuit.

[0031] The comparison unit 11 outputs a high-level voltage signal to the drive unit 3 when the voltage signal input from the temperature characteristic simulation unit 10 is equal to or greater than the reference voltage value input from the reference voltage generation unit 12, and outputs a low-level voltage signal to the drive unit 3 when the voltage signal input from the temperature characteristic simulation unit 10 is less than the reference voltage value.

[0032] The reference voltage value is set, for example, to a voltage value corresponding to the threshold temperature difference between the wire temperature of the wire 300 and the ambient temperature of the wire 300, as indicated by the voltage signal output by the temperature characteristic simulation unit 10. The threshold temperature difference between the wire temperature of the wire 300 and the ambient temperature of the wire 300 is, for example, a value above which malfunctions such as smoke or fire will occur in the wire 300. The reference voltage value is an example of a first voltage threshold.

[0033] An example of the operation of the current control device 100 configured as described above will now be explained. When the control unit 4 receives a command signal from a higher-level device to operate the load 400, it outputs a control signal to the drive unit 3 to turn on the switch unit 2. When the drive unit 3 receives the control signal to turn on the switch unit 2, it outputs a drive signal to the switch unit 2 to turn on the switch unit 2. As a result, the switch unit 2 is turned on, and the supply current Is is supplied from the power supply 200 to the load 400 via the current control device 100 and the wire 300, causing the load 400 to operate.

[0034] Furthermore, when the control unit 4 receives a command signal from a higher-level device to stop the operation of the load 400, it outputs a control signal to the drive unit 3 to turn off the switch unit 2. When the drive unit 3 receives a control signal to turn off the switch unit 2, it outputs a drive signal to the switch unit 2 to turn off the switch unit 2. As a result, the switch unit 2 is turned off, the supply current Is is cut off, and the load 400 stops operating.

[0035] Furthermore, when the switch unit 2 is turned ON by a command signal from the control unit 4, the current control device 100 operates, for example, as follows.

[0036] The drive unit 3 outputs a drive signal to the switch unit 2 to turn off its operating state if the voltage value of the voltage signal input from the switch temperature detection unit 5 is equal to or greater than a predetermined voltage threshold. Here, the predetermined voltage threshold is set so that the voltage value of the voltage signal output by the switch temperature detection unit 5 corresponds to the temperature threshold of the switch unit 2. The temperature threshold of the switch unit 2 is, for example, the temperature above which malfunctions such as failures will occur in the switch unit 2. In this way, the current control device 100 prevents the temperature of the switch unit 2 from becoming excessive due to the flow of the supplied current Is to the switch unit 2.

[0037] Furthermore, if the voltage signal input from the comparison unit 11 is a high-level voltage signal, the drive unit 3 outputs a drive signal to the switch unit 2 that turns off the operating state of the switch unit 2. When the voltage signal input from the comparison unit 11 is a high-level voltage signal, it corresponds to the case where the voltage value of the voltage signal output by the temperature characteristic simulation unit 10 is above the threshold temperature difference between the wire temperature of the wire 300 and the ambient temperature of the wire 300. As a result, the current control device 100 prevents the temperature difference between the wire temperature of the wire 300 and the ambient temperature of the wire 300 from becoming excessive due to the flow of the supply current Is through the wire 300. When the voltage signal input from the comparison unit 11 is a high-level voltage signal, it is an example of the case where the voltage of the first voltage signal output by the temperature characteristic simulation unit 10 is above the first voltage threshold.

[0038] Furthermore, if the voltage value of the voltage signal input from the resistor 9 is greater than or equal to another predetermined voltage threshold, the drive unit 3 outputs a drive signal to the switch unit 2 to turn it off. Here, the other predetermined voltage threshold is set so that the voltage value of the voltage signal output by the resistor 9 corresponds to the current threshold of the supply current Is. The current threshold of the supply current Is is the current at which, for example, if more current flows through the switch unit 2 or the wire 300, malfunctions such as failures will occur in the switch unit 2 or the wire 300. As described above, the second current is a value corresponding to the supply current Is, and the third current is a value corresponding to the second current, so the third current is also a value corresponding to the supply current Is. If the voltage value of the voltage signal input from the resistor 9 is greater than or equal to another predetermined voltage threshold, it corresponds to the case where the third current is greater than or equal to the first current threshold. As a result, the current control device 100 prevents the supply current Is flowing through the switch unit 2 or the wire 300 from becoming an excessive value.

[0039] With the current control device 100 configured as described above, it is prevented that the switch unit 2 and the wire 300 will become excessively hot. Furthermore, the current control device 100 prevents the supply current Is flowing through the switch unit 2 and the wire 300 from becoming excessively high. In addition, the current generation unit 8 generates a third current based on the magnetic field generated by the input second current, and the drive unit 3 turns off the switch unit 2 based on the third current. Therefore, even if the supply current Is changes abruptly and becomes excessively high, the switch unit 2 can be turned off with a faster response than the temperature characteristic simulation unit 10. Moreover, the current generation unit 8 can be realized with a relatively simple configuration with a relatively small number of components, such as a common mode choke coil, and in a relatively small mounting area.

[0040] Figure 2 is a time chart showing an example of the operating characteristics of the current control device shown in Figure 1. Figure 2(a) shows the supply current Is, Figure 2(b) shows the voltage signal output from the resistor 9 to the drive unit 3 by the current generation unit 8, and Figure 2(c) shows the voltage signal output from the temperature characteristic simulation unit 10 to the comparison unit 11.

[0041] As shown in Figure 2(a), the supply current Is is initially 0A as indicated by line L11, and normally rises as indicated by line L12 in response to the control signal from the control unit 4, and then becomes a constant value as indicated by line L13. However, if a short circuit occurs, the supply current Is changes to rise sharply as indicated by line L14. In this case, the temperature characteristic simulation unit 10 responds relatively slowly as indicated by line L3 in Figure 2(c), and therefore cannot cope with a sharp change as indicated by line L14. However, the voltage signal output from the resistor unit 9 to the drive unit 3 by the current generation unit 8 responds quickly as indicated by line L2 in Figure 2(b). Therefore, by setting a voltage threshold in the drive unit 3, for example as indicated by line L4 in Figure 2(b), it is possible to interrupt the large current that rises sharply as indicated by line L14.

[0042] Figure 3 is a graph showing an example of the supply current interruption characteristics of the current control device 100. In Figure 3, the horizontal axis represents the energizing time of the supply current Is, and the vertical axis represents the supply current Is. Lines L5, L6, L7, and L8 represent the smoke emission characteristics of the electric wire 300, the interruption characteristics of the switch unit 2, the interruption characteristics of the temperature characteristic simulation unit 10, and the interruption characteristics of the current generation unit 8, respectively.

[0043] For example, if the supply current Is is I1, the supply current Is is cut off by the temperature characteristic simulation unit 10 at time t1, preventing smoke from being emitted from the wire 300. Also, if the supply current Is is relatively large I2, the supply current Is is quickly cut off by the current generation unit 8 at a shorter time t2, preventing smoke from being emitted from the wire 300 and protecting the switch unit 2.

[0044] (Embodiment 2) Figure 4 is a block diagram showing the configuration of an electrical device equipped with a current control device according to Embodiment 4. Electrical device 1000A has a configuration in which the current control device 100 according to Embodiment 1 is replaced with the current control device 100A according to Embodiment 2, in the configuration of electrical device 1000 shown in Figure 1.

[0045] The current control device 100A has a configuration in which the current generating unit 8 is replaced with a current generating unit 8A in the configuration of the current control device 100.

[0046] The current generating unit 8A comprises a first conductor 8Aa, a second conductor 8Ab provided adjacent to the first conductor 8Aa, and a substrate 8Ac.

[0047] The first conductor 8Aa constitutes a part of the conductor included in the main wire 1. One end of the first conductor 8Aa is located on the switch section 2 side, and the other end of the first conductor 8Aa is located on the electric wire 300 side. A part of the second conductor 8Ab is arranged parallel to the part of the first conductor 8Aa. One end of the second conductor 8Ab is connected to the resistor section 9, and the other end of the second conductor 8Ab is connected to ground.

[0048] Furthermore, the first conductor 8Aa and the second conductor 8Ab are formed as a conductor pattern on a substrate 8Ac made of an insulator.

[0049] When the supply current Is flows from the switch unit 2 to the first conductor 8Aa, the magnetic field generated by this current causes a current to be generated in the second conductor 8Ab, which then flows through the second conductor 8Ab. In other words, the current generation unit 8A is an example of a current generation unit that receives a second current corresponding to the supply current Is, and generates a third current corresponding to the second current through the magnetic field generated by the second current. In this case, the second current is the supply current Is.

[0050] The current control device 100A configured as described above has the same effects as the current control device 100 according to Embodiment 1. In particular, in the current control device 100A, the current generation unit 8A is realized by a wiring pattern consisting of a first conductor 8Aa and a second conductor 8Ab, thus enabling a simpler configuration with even fewer components and an even smaller mounting area.

[0051] In the current control device 100A according to Embodiment 2 described above, a portion of the second conductor 8Ab is arranged parallel to a portion of the first conductor 8Aa. However, the arrangement of the second conductor 8Ab is not particularly limited, as long as the arrangement allows a current to be generated in the second conductor 8Ab by the magnetic field generated by the current flowing through the first conductor 8Aa.

[0052] Furthermore, in the current control device 100A according to the second embodiment described above, the current generating unit 8A is configured so that the supplied current Is is input to the first conductor 8Aa as the second current. However, as a variation of the current control device 100 and the current control device 100A, the current control device may be configured to include a current generating unit to which at least a portion of the supplied current Is or at least a portion of the first current input to the temperature characteristic simulation unit 10 is input as the second current. That is, for example, a portion of the supplied current Is or a portion of the first current may be branched and input to the current generating unit.

[0053] Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader embodiments of the present invention are not limited to the embodiments described above, and various modifications are possible. [Explanation of Symbols]

[0054] 1: Main line 2: Switch section 3: Drive unit 4: Control Unit 5: Switch temperature detection unit 6: Current output section 7: Diode 8, 8A: Current generation unit 8a: Primary coil 8b: Secondary coil 8Aa: First conductor 8Ab: Second conductor 8Ac: Circuit board 9:Resistance section 10:Temperature characteristics simulation part 11: Comparison Section 12: Reference voltage generation unit 100, 100A: Current control device 200: Power supply 300: Electric wire 400: Load 1000, 1000A: Electrical equipment

Claims

1. A current control device that controls the supply current supplied from a power source to a load via a power line, A switch unit that allows the supply current to flow when it is in the ON state and cuts off the supply current when it is in the OFF state, A temperature characteristic simulation unit receives a first current corresponding to the supply current and outputs a first voltage signal corresponding to the temperature difference between the wire temperature and the ambient temperature of the wire, thereby simulating the temperature characteristics of the wire. A current generation unit equipped with a common mode choke coil, into which a second current corresponding to the supply current is input, and which generates a third current corresponding to the second current by the magnetic field generated by the second current, A drive unit that controls the switch unit to an off state when the voltage of the first voltage signal is equal to or greater than a first voltage threshold or when the third current is equal to or greater than a first current threshold, Equipped with Current control device.

2. The second current is at least a portion of the supply current or at least a portion of the first current. The current control device according to claim 1.

3. A current control device for controlling the supply current supplied from a power source to a load via a wire, A switch unit that allows the supply current to flow when it is in the ON state and cuts off the supply current when it is in the OFF state, A temperature characteristic simulation unit receives a first current corresponding to the supply current and outputs a first voltage signal corresponding to the temperature difference between the wire temperature and the ambient temperature of the wire, thereby simulating the temperature characteristics of the wire. A current generating unit receives a second current corresponding to the supply current, and generates a third current corresponding to the second current using the magnetic field generated by the second current. A drive unit that controls the switch unit to an off state when the voltage of the first voltage signal is equal to or greater than a first voltage threshold or when the third current is equal to or greater than a first current threshold, Equipped with, The current generating unit comprises a first conductor into which the second current is input, a second conductor provided adjacent to the first conductor through which the third current flows, and a substrate on which the first conductor and the second conductor are formed as a conductor pattern. Current control device.

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