WO2018101012A1 - Power supply control device, power supply control method, and computer program - Google Patents

Abstract

A power supply control device (12) controls the supply of power, which is supplied via an electric wire (W1). A control unit of a microcomputer (23) periodically fetches an electric wire current value flowing in the electric wire (W1), and calculates the square value of the fetched electric wire current value. The control unit of the microcomputer (23) calculates the electric wire temperature of the electric wire (W1) each time n (n: integer of 2 or greater) periods relating to fetching of the electric wire current elapse. The control unit of the microcomputer (23) determines whether or not the integrated value of the square value of k items, calculated at the kth (k: natural number of n or less) period from the first period of the n periods, is an integrated threshold value or greater. The control unit of the microcomputer (23) changes the integrated threshold value to be a smaller value the higher that the calculated electric wire temperature is.

Description

Power supply control device, power supply control method, and computer program

The present invention relates to a power supply control device, a power supply control method, and a computer program.
This application claims priority based on Japanese Patent Application No. 2016-235118 filed on December 2, 2016, and incorporates all the description content described in the above Japanese application.

Patent Document 1 discloses a power supply control device that controls power supply via an electric wire by switching a switch provided in the middle of the electric wire to ON or OFF. In this power supply control device, the electric wire temperature is calculated based on the electric wire current value flowing through the electric wire. When the calculated wire temperature is equal to or higher than the temperature threshold, the switch is turned off to lower the wire temperature.

Patent Document 2 discloses a power supply control device that has a low processing amount for calculating the wire temperature performed by a microcomputer (hereinafter referred to as a microcomputer). In this power supply control device, the microcomputer periodically acquires the electric wire current value. Each time an n (n: integer greater than or equal to 2) period related to the acquisition of the wire current value elapses, the microcomputer uses the n wire current values acquired from the first cycle of the n cycle to the n cycle. The temperature is calculated, and it is determined whether or not the calculated wire temperature is equal to or higher than the temperature threshold. When the microcomputer determines that the wire temperature is equal to or higher than the temperature threshold, the microcomputer outputs a control signal instructing switching to OFF to the switch.

The microcomputer determines whether or not the wire current value is equal to or greater than a predetermined value from the first cycle of the n cycle related to the acquisition of the wire current value to the (n−1) cycle. When the electric wire current value is equal to or greater than a predetermined value, the microcomputer outputs a control signal instructing switching to OFF to the switch.

JP 2010-283777 A JP2015-105924A

A power supply control device according to an aspect of the present invention is a power supply control device that controls power supply via an electric wire, and an acquisition unit that periodically acquires an electric wire current value flowing through the electric wire, and the acquisition unit acquires A square value calculation unit for calculating the square value of the electric wire current value, and a temperature calculation for calculating the electric wire temperature of the electric wire every time n (n: an integer of 2 or more) related to the acquisition of the electric wire current value elapses. And the integrated value of the k square values calculated by the square value calculation unit in the k period (k: a natural number less than or equal to n) from the first cycle of the n cycle is greater than or equal to an integration threshold. And a change unit that changes the integration threshold to a smaller value as the electric wire temperature calculated by the temperature calculation unit is higher.

A power feeding control method according to an aspect of the present invention is a power feeding control method for controlling power feeding through an electric wire, the step of periodically obtaining a current value of the electric wire flowing through the electric wire, and 2 of the obtained electric wire current value. From the step of calculating the multiplier value, the step of calculating the wire temperature of the wire, and the first cycle of the n cycle each time n (n: an integer of 2 or more) related to the acquisition of the wire current value elapses. a step of determining whether or not an integrated value of the k square values calculated in the k (k: natural number equal to or less than n) period is equal to or greater than an integration threshold; Changing to a smaller value.

The computer program which concerns on 1 aspect of this invention WHEREIN: The step which acquires the electric wire electric current value which flows through an electric wire periodically, the step which calculates the square value of the acquired electric wire electric current value, and acquisition of the said electric wire electric current value Each time an n (n: integer greater than or equal to 2) period has elapsed, a step of calculating the wire temperature of the electric wire and a k (k: natural number less than n) period from the first period of the n period were calculated. A step of determining whether or not an integrated value of the k square values is equal to or greater than an integrated threshold value and a step of changing the integrated threshold value to a smaller value as the calculated electric wire temperature is higher are executed.

In addition, the present invention can be realized not only as a power supply control device including such a characteristic processing unit, but also as a power supply control method using such characteristic processing as a step, It can be realized as a computer program for execution. Further, the present invention can be realized as a semiconductor integrated circuit that realizes part or all of the power supply control device, or can be realized as a power supply control system including the power supply control device.

1 is a block diagram illustrating a main configuration of a power supply system 1 according to a first embodiment. It is a block diagram which shows the principal part structure of a microcomputer. It is a flowchart which shows the procedure of the electric wire protection process of an electric wire. It is a graph which shows transition of a counter value. 10 is a chart showing storage contents of a storage unit in Embodiment 2. It is a flowchart which shows the procedure of the electric wire protection process of an electric wire. It is a flowchart which shows the procedure of the electric wire protection process of an electric wire.

[Problems to be solved by the present disclosure]
In the power supply control device described in Patent Literature 2, instead of determining whether the electric wire temperature is equal to or higher than the temperature threshold value, it is determined whether the electric wire current value is equal to or higher than a predetermined value. However, the difference between the wire temperature and the temperature threshold is large when the wire current value is greater than or equal to a predetermined value. In other words, even if the electric wire current value is less than a predetermined value, the electric wire temperature may be equal to or higher than the temperature threshold value.

As long as the heat generation amount of the wire per unit time exceeds the heat dissipation amount of the wire per unit time, the wire temperature rises. If the wire current value continues to be slightly smaller than the predetermined value, the wire temperature may greatly exceed the temperature threshold during the (n-1) th cycle of the n cycle for acquiring the wire current value There is.

Therefore, an object of the present invention is to provide a power supply control device, a power supply control method, and a computer program capable of performing a determination that is substantially equivalent to the determination related to the wire temperature using the wire current value.

[Effects of the present disclosure]
According to the present disclosure, it is possible to perform a determination that is substantially equivalent to the determination related to the wire temperature using the wire current value.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described. You may combine arbitrarily at least one part of embodiment described below.

(1) A power supply control device according to an aspect of the present invention is a power supply control device that controls power supply via an electric wire, and periodically acquires an electric wire current value flowing through the electric wire, and the acquisition unit. Calculates the square value of the electric wire current value acquired by the calculation unit, and calculates the electric wire temperature of the electric wire every time an n (n: integer greater than or equal to 2) period related to the acquisition of the electric wire current value elapses. The integrated value of the k square values calculated by the square value calculation unit in the k (k: natural number less than or equal to n) period from the first cycle of the n cycle is greater than or equal to the integration threshold value. An integrated value determination unit that determines whether or not there is a change unit, and a change unit that changes the integration threshold value to a smaller value as the electric wire temperature calculated by the temperature calculation unit is higher.

(2) The power supply control device according to an aspect of the present invention provides the n squares calculated by the square value calculation unit from the first cycle to the n cycle of the n cycle each time the n cycle elapses. A temperature difference calculation unit that calculates a temperature difference between the electric wire temperature and a predetermined temperature based on the value; and the temperature calculation unit adds the temperature difference calculated by the temperature difference calculation unit to the predetermined temperature. To calculate the wire temperature.

(3) In the power supply control device according to an aspect of the present invention, the temperature difference calculation unit includes an integrated value of the n square values, a preceding temperature difference between the wire temperature and a predetermined temperature calculated in advance. Based on the above, the temperature difference between the wire temperature and the predetermined temperature is calculated.

(4) In the power supply control device according to one aspect of the present invention, a storage unit storing n weighting factors corresponding to each of the n square values, and each of the n square values, A multiplication unit that multiplies the corresponding weighting factors in the n weighting factors, and the temperature difference calculation unit includes an integrated value of n multiplication values multiplied by the multiplication unit and the previously calculated value. The temperature difference between the wire temperature and the predetermined temperature is calculated based on the wire temperature and the preceding temperature difference between the predetermined temperature.

(5) The power feeding control method according to one aspect of the present invention is a power feeding control method for controlling power feeding through an electric wire, the step of periodically obtaining the value of the electric wire current flowing through the electric wire, and the obtained electric wire current. A step of calculating a square value of the value, a step of calculating a wire temperature of the wire every time an n (n: integer greater than or equal to 2) period related to acquisition of the wire current value elapses, and 1 of the n cycle The step of determining whether or not the integrated value of the k square values calculated in the k period (k: natural number less than or equal to n) from the period is greater than or equal to the integration threshold, and the higher the calculated wire temperature, Changing the integration threshold value to a small value.

(6) The computer program which concerns on 1 aspect of this invention WHEREIN: The step which acquires the electric wire electric current value which flows through an electric wire to a computer periodically, the step which calculates the square value of the acquired electric wire electric current value, and the said electric wire electric current Every time an n (n: integer greater than or equal to 2) period for obtaining a value elapses, a step of calculating the wire temperature of the wire, and a k (k: natural number less than n) period from the first period of the n period The step of determining whether or not the integrated value of the k square values calculated in step S is equal to or greater than the integrated threshold value and the step of changing the integrated threshold value to a smaller value as the calculated wire temperature is higher are executed. .

In the power supply control device, the power supply control method, and the computer program according to the above aspect, the electric wire current value is periodically acquired, and the square value of the acquired electric wire current value is calculated. It is determined whether or not the integrated value of k square values calculated from the first cycle to the k cycle of the n cycle related to the acquisition of the electric wire current value is equal to or greater than the integration threshold.

The increase in the wire temperature increases as the power consumption consumed by the wire, that is, the integrated value of the square value of the wire current value increases. Therefore, the integrated value of the k square values indicates the increase range of the wire temperature during the k period.

Every time the n period elapses, the integrated threshold value is changed to a smaller value as the calculated wire temperature is higher, that is, as the wire temperature is closer to the temperature threshold at which energization through the wire is to be cut off. The integrated threshold indicates an allowable increase in the wire temperature.

Determining whether or not the integrated value of k square values is equal to or greater than the integral threshold is whether or not the increase in wire temperature during the k period is equal to or greater than the allowable increase in wire temperature. This corresponds to determining, that is, determining whether the wire temperature is equal to or higher than the temperature threshold. As a result, a determination that is substantially equivalent to the determination related to the wire temperature is performed using the wire current value.

In the power supply control device according to the above aspect, the wire temperature and the predetermined temperature are calculated based on n square values calculated from the first cycle of the n cycle to the n cycle every time the n cycle elapses. The wire temperature is calculated by adding a predetermined temperature to the calculated temperature difference. Therefore, the square value is used not only for determination of the integrated value but also for calculation of the wire temperature.

In the power supply control device according to the above aspect, the temperature difference between the electric wire temperature and the predetermined temperature is calculated based on an integrated value of n square values, so that the temperature difference is easily calculated. .

In the power supply control device according to the above aspect, each of the n square values is multiplied by a corresponding weighting factor, and an accurate temperature difference is calculated based on an integrated value of the n multiplied values. .

[Details of the embodiment of the present invention]
A specific example of a power supply control device according to an embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and it is intended that all the changes within the meaning and range equivalent to a claim are included.

(Embodiment 1)
FIG. 1 is a block diagram illustrating a main configuration of a power supply system 1 according to the first embodiment. The power supply system 1 is suitably mounted on a vehicle, and includes a battery 10, n (n: integer of 2 or more) loads 11a, 11b,..., A power supply control device 12, and n electric wires W1, W2, and so on. It is equipped with ... One end of each of the electric wires W1, W2,... Is connected to the positive electrode of the battery 10. The other ends of the electric wires W1, W2,... Are connected to one ends of loads 11a, 11b,. The negative electrode of the battery 10 and the other ends of the loads 11a, 11b, ... are grounded. The power feeding control device 12 is connected in the middle of the electric wires W1, W2,.

The battery 10 supplies power to the loads 11a, 11b,... Via the electric wires W1, W2,. Each of the loads 11a, 11b,... Is an electric device mounted on the vehicle. Each of the loads 11a, 11b,... Operates when power is supplied, and stops operating when power supply is stopped.

The power feeding control device 12 controls power feeding via the electric wires W1, W2,. The power supply control device 12 performs the interruption of energization and the release of the interruption for each of the electric wires W1, W2,. When energization through one of the n wires W1, W2,... is interrupted, power supply from the battery 10 to the load connected to this wire is stopped, and this load operates Stop. When the interruption of energization through one of the n wires W1, W2,... is released, power supply from the battery 10 to the load connected to the wire is resumed. Operate. As a specific example, when energization through the electric wire W1 is interrupted, power supply from the battery 10 to the load 11a is stopped, and the load 11a stops operating. Further, when the energization via the electric wire W1 is released, the power supply from the battery 10 to the load 11a is resumed, and the load 11a operates.

The power supply control device 12 has an operation signal indicating one or a plurality of loads to be operated among the n loads 11a, 11b,..., And operates among the n loads 11a, 11b,. And a stop signal indicating one or a plurality of loads to be stopped. When the operation signal is input, the power supply control device 12 passes through one or more electric wires connected to one or more loads indicated by the input operation signal among the electric wires W1, W2,. Release the power interruption. As a result, one or more loads indicated by the activation signal are activated.
When the stop signal is input, the power supply control device 12 passes through one or more electric wires connected to one or more loads indicated by the input stop signal among the electric wires W1, W2,. Shut off the energized power. Thereby, the operation | movement of the 1 or several load which a stop signal shows stops.

The power supply control device 12 cuts off energization based on the current values of the wires flowing through the wires W1, W2,... And the temperatures of the wires W1, W2,. For example, the power supply control device 12 interrupts energization via the electric wire W1 based on the value of the electric wire current flowing through the electric wire W1 and the electric wire temperature of the electric wire W1.

The power supply control device 12 includes n switches 20a, 20b, ..., n current output circuits 21a, 21b, ..., n drive circuits 22a, 22b, ..., a microcomputer 23, and It has n resistors R1, R2,. Each of the n switches 20a, 20b,... is an N-channel FET (Field-Effect-Transistor). The switches 20a, 20b,... Are provided in the middle of the electric wires W1, W2,. Similarly, the current output circuits 21a, 21b,... Are connected in the middle of the electric wires W1, W2,.

The drain of the switch 20a is connected to the positive electrode of the battery 10 via the electric wire W1. The source of the switch 20a is connected to the current output circuit 21a via the electric wire W1. The current output circuit 21a is further connected to one end of the load 11a via the electric wire W1 and to one end of the resistor R1. The other end of the resistor R1 is grounded. One end of the resistor R1 is further connected to the drive circuit 22a and the microcomputer 23. The drive circuit 22a is further connected to the gate of the switch 20a and the microcomputer 23.

The switch 20b, the current output circuit 21b, the drive circuit 22b, and the resistor R2 are connected in the same manner as the switch 20a, the current output circuit 21a, the drive circuit 22a, and the resistor R1. Other switches, current output circuits, drive circuits, and resistors not shown are also connected in the same manner as the switches 20a, current output circuits 21a, drive circuits 22a, and resistors R1.

Hereinafter, operations of the switch 20a, the current output circuit 21a, the drive circuit 22a, and the resistor R1 will be described.
The operations of the switch 20b, current output circuit 21b, drive circuit 22b, and resistor R2 are the same as the operations of the switch 20a, current output circuit 21a, drive circuit 22a, and resistor R1. Furthermore, the operations of other switches, current output circuits, drive circuits, and resistors (not shown) are the same as the operations of the switch 20a, current output circuit 21a, drive circuit 22a, and resistor R1. Therefore, detailed description of these operations is omitted.

In the switch 20a, when the gate voltage value with respect to the source potential is equal to or higher than a certain voltage value, a current can flow through the drain and the source. At this time, the switch 20a is on. When the switch 20a is switched on, the interruption of energization via the electric wire W1 is released. Thereby, electric power is supplied from the battery 10 to the load 11a via the electric wire W1, and the load 11a operates.

In the switch 20a, when the gate voltage value with respect to the source potential is less than a certain voltage value, no current flows through the drain and the source. At this time, the switch 20a is off. When the switch 20a is switched off, the energization through the electric wire W1 is interrupted. Thereby, the power supply from the battery 10 to the load 11a is stopped, and the load 11a stops its operation.

The current output circuit 21a is constituted by, for example, a current mirror circuit, and outputs a current whose current value is a predetermined fraction of the electric wire current value flowing through the electric wire W1 to the resistor R1. The voltage value between both ends of the resistor R1 (hereinafter, referred to as both-end voltage value) is calculated by dividing the product of the wire current value of the wire W1 and the resistance value of the resistor R1 by the predetermined number described above. The resistance value of the resistor R1 is constant. For this reason, the voltage value across the resistor R1 is proportional to the wire current value of the wire W1. Therefore, the acquisition of the voltage value across the resistor R1 corresponds to the acquisition of the wire current value of the wire W1.

A voltage value across the resistor R1 is input to the drive circuit 22a, and a control signal including a high level voltage value and a low level voltage value is input from the microcomputer 23.
When the voltage value across the resistor R1 is less than the reference voltage value and the voltage value indicated by the control signal is switched from the low level voltage value to the high level voltage value, the drive circuit 22a is a switch based on the ground potential. The voltage value of the gate 20a is increased. As a result, in the switch 20a, the gate voltage value with reference to the source potential becomes a certain voltage value or more, and the switch 20a is switched from OFF to ON.

Further, when the voltage value across the resistor R1 is less than the reference voltage value, the drive circuit 22a uses the ground potential as a reference when the voltage value indicated by the control signal is switched from the high level voltage value to the low level voltage value. The voltage value of the gate of the switch 20a is lowered. Thereby, in the switch 20a, the gate voltage value with reference to the source potential becomes less than a certain voltage value, and the switch 20a is switched from on to off.

When the voltage value at both ends of the resistor R1 becomes equal to or higher than the reference voltage value, the drive circuit 22a reduces the voltage value of the gate of the switch 20a with respect to the ground potential regardless of the voltage value indicated by the control signal. Switch off. Thereafter, the drive circuit 22a keeps the switch 20a off until a predetermined condition is satisfied. The predetermined condition is, for example, that the voltage value indicated by the control signal is switched in the order of the low level voltage value and the high level voltage value.

An operation signal and a stop signal are input to the microcomputer 23. The microcomputer 23 switches the voltage value indicated by the control signal to the low level voltage value or the high level voltage value based on the contents indicated by the input operation signal or stop signal or the input voltage value across the resistor R1.
The microcomputer 23 also receives a voltage value across the resistor R2, and also receives a voltage value across other resistors (not shown). The microcomputer 23 outputs a control signal to the drive circuit 22b and also outputs a control signal to a drive circuit (not shown). The microcomputer 23 switches the voltage values indicated by the plurality of control signals.

FIG. 2 is a block diagram showing a main configuration of the microcomputer 23. The microcomputer 23 includes a control unit 30, a storage unit 31, an input unit 32, n input units 33a, 33b, ..., n output units 34a, 34b, ..., and n A (Analog) / D (Digital) converters 35a, 35b,... The control unit 30, the storage unit 31, and the input unit 32 are connected to the bus 36.

The output unit 34a is connected to the drive circuit 22a and the bus 36 separately. The A / D converter 35a is connected to the input unit 33a and the bus 36 separately. The input unit 33a is further connected to one end of the resistor R1.
Similarly, the output unit 34b is connected to the drive circuit 22b and the bus 36 separately. The A / D converter 35b is connected to the input unit 33b and the bus 36 separately. The input unit 33b is further connected to one end of the resistor R2. An input unit, an output unit, and an A / D conversion unit (not shown) are connected in the same manner as the input unit 33a, the output unit 34a, and the A / D conversion unit 35a.

The input unit 32 receives an operation signal and a stop signal. When the operation signal or the stop signal is input, the input unit 32 notifies the control unit 30 of the input signal and the load indicated by the signal.

Hereinafter, operations of the input unit 33a, the output unit 34a, and the A / D conversion unit 35a will be described.
The operations of the input unit 33b, the output unit 34b, and the A / D conversion unit 35b are the same as the operations of the input unit 33a, the output unit 34a, and the A / D conversion unit 35a. Furthermore, operations of an input unit, an output unit, and an A / D conversion unit (not shown) are the same as the operations of the input unit 33a, the output unit 34a, and the A / D conversion unit 35a. Therefore, detailed description of these operations is omitted.

The voltage value at both ends of the analog resistor R1 is input to the input unit 33a. The input unit 33a outputs the input analog both-end voltage value to the A / D conversion unit 35a. The A / D converter 35a converts the analog both-end voltage value input from the input unit 33a into a digital both-end voltage value. The control unit 30 acquires the digital both-end voltage value from the A / D conversion unit 35a. The both-end voltage value acquired by the control unit 30 substantially matches the both-end voltage value of the resistor R1 at the time of acquisition.

The output unit 34a outputs a control signal to the drive circuit 22a. The output unit 34a switches the voltage value indicated by the control signal output to the drive circuit 22a to a low level voltage value or a high level voltage value in accordance with an instruction from the control unit 30.

The storage unit 31 is a nonvolatile memory. The storage unit 31 stores a computer program P1.
The control unit 30 has a CPU (Central Processing Unit) (not shown). The CPU of the control unit 30 executes the computer program P1 stored in the storage unit 31 to execute the operation process, the stop process, and the electric wire protection processes of the electric wires W1, W2,.

The operation process is a process for operating one or a plurality of loads among the n loads 11a, 11b,. The stop process is a process for stopping the operation of one or a plurality of loads in the n loads 11a, 11b,. Each of the electric wire protection processes of the electric wires W1, W2,... Is a process of protecting the corresponding electric wires from overheating. As a specific example, the electric wire protection process for the electric wire W1 is a process for protecting the electric wire W1 from overheating.
The computer program P1 is a computer program for causing the CPU of the control unit 30 to execute the operation process, the stop process, and the electric wire protection processes of the electric wires W1, W2,.

Note that the computer program P1 may be stored in the storage medium E1 so that the computer can read it. In this case, the computer program P1 read from the storage medium E1 by a reading device (not shown) is stored in the storage unit 31. The storage medium E1 is an optical disk, a flexible disk, a magnetic disk, a magnetic optical disk, a semiconductor memory, or the like. The optical disc is a CD (Compact Disc) -ROM (Read Only Memory), a DVD (Digital Versatile Disc) -ROM, or a BD (Blu-ray (registered trademark) Disc). The magnetic disk is, for example, a hard disk. Alternatively, the computer program P1 may be downloaded from an external device (not shown) connected to a communication network (not shown), and the downloaded computer program P1 may be stored in the storage unit 31.

The output units 34a, 34b,... Correspond to the loads 11a, 11b,. Therefore, each operation | movement of load 11a, 11b, ... is controlled according to the voltage value which the control signal which output part 34a, 34b, ... outputs has shown. As described above, when the voltage value indicated by the control signal output from the output unit 34a is switched from the low level voltage value to the high level voltage value, the drive circuit 22a switches the switch 20a from OFF to ON, and the load 11a. Operates. When the voltage value indicated by the control signal output from the output unit 34a is switched from the high level voltage value to the low level voltage value, the drive circuit 22a switches the switch 20a from on to off, and the operation of the load 11a stops. .

The control unit 30 performs an operation process when an operation signal is input to the input unit 32. In the operation process, the control unit 30 instructs the output unit corresponding to each of the one or a plurality of loads indicated by the operation signal to switch the voltage value indicated by the control signal from the low level voltage value to the high level voltage value. Accordingly, one or a plurality of loads indicated by the operation signal input to the input unit 32 are operated. Thereafter, the control unit 30 ends the operation process.

When the stop signal is input to the input unit 32, the control unit 30 executes a stop process. In the stop process, the control unit 30 instructs the output unit corresponding to each of the one or a plurality of loads indicated by the stop signal to switch the voltage value indicated by the control signal from the high level voltage value to the low level voltage value. Thereby, the operation | movement of the 1 or several load which the stop signal input into the input part 32 shows stops operation | movement. Thereafter, the control unit 30 ends the stop process.

The control unit 30 executes the electric wire protection processes of the electric wires W1, W2,. The control unit 30 periodically executes these n wire protection processes. The start points of the n wire protection processes are substantially the same.
Below, the electric wire protection process of the electric wire W1 is demonstrated. The wire protection process for the wire W2 and the wire protection process for other wires not shown are performed in the same manner as the wire protection process for the wire W1. For this reason, detailed description of these electric wire protection processes is abbreviate | omitted.

A cycle in which the wire protection process of the wire W1 is executed is described as Δt (unit: s). In the following, “·” represents a product.
In the wire protection process of the wire W1, the control unit 30 always acquires the wire current value of the wire W1 from the A / D conversion unit 35a. Therefore, the period Δt related to the execution of the electric wire protection process is also a period related to the acquisition of the electric wire current value.

The wire protection process of the wire W1 that is repeatedly executed includes a wire protection process that calculates the temperature difference between the wire temperature of the wire W1 and the ambient temperature of the wire W1, and a wire protection process that does not calculate the temperature difference. Yes. In the wire protection process of the nth cycle after the wire protection process for calculating the temperature difference is executed, the temperature difference is calculated again. Therefore, the control unit 30 repeatedly calculates the temperature difference between the wire temperature and the ambient temperature every time the n period related to the execution of the wire protection process elapses. In the calculation of the temperature difference, the control unit 30 determines the electric wire based on the previously calculated temperature difference and the integrated value of the electric wire current value calculated from the first cycle of the n cycle to the n cycle related to the execution of the wire protection process. Calculate the temperature difference between temperature and ambient temperature.

The ambient temperature of the electric wire W1 depends on the place in the vehicle where the electric wire W1 is arranged, and hardly depends on the temperature outside the vehicle. In the vehicle, the position where the electric wire W1 is arranged is fixed. For this reason, it can be considered that the ambient temperature is a constant temperature. The ambient temperature is preset. The ambient temperature corresponds to a predetermined temperature.

The calculation of the wire temperature of the wire W1 will be described. The temperature difference and the electric wire current value in the s period of the n period related to the execution of the electric wire protection process are described as ΔT (s) (unit: ° C.) and I (s) (unit: A). s is an integer greater than or equal to zero and less than or equal to n. The temperature difference ΔT (n) is a temperature difference in the nth cycle, and the preceding temperature difference ΔT (0) is a previously calculated temperature difference. The temperature difference ΔT (n) is calculated by the following equations (1), (2), and (3).

Here, τ is a heat dissipation time constant (unit: s) of the electric wire W1. Rth is the wire thermal resistance (unit: ° C./W) of the wire W1. Rw is the wire resistance (unit: Ω) of the wire W1. The period Δt, the heat radiation time constant τ, the wire thermal resistance Rth, and the wire resistance Rw are constant. For this reason, Ca and Cb are constants.
The wire resistance Rw is, for example, the wire resistance of the wire W1 when the wire temperature of the wire W1 is a smoke generation temperature at which the wire W1 smokes. When the wire resistance Rw is set in this way, when the wire temperature of the wire W1 is low, the wire resistance Rw is larger than the actual wire resistance, and the temperature difference ΔT (n) is also larger than the actual temperature difference. In the same case, when the wire temperature of the wire W1 is high, the wire resistance Rw substantially matches the actual wire resistance, and the temperature difference ΔT (n) also substantially matches the actual temperature difference. Therefore, by setting the wire resistance Rw to the wire resistance when the wire temperature is the smoke generation temperature, when the wire temperature is high, that is, when an accurate calculation of the wire temperature is required, an accurate temperature difference is obtained. Calculated.

The temperature difference ΔT (n−1) is a temperature difference in the (n−1) period and is not calculated. For this reason, the temperature difference ΔT (n−1) is represented by the electric wire current value I (n−1) and the temperature difference ΔT (n−2), and when the equation (1) is developed, the temperature difference ΔT (n) It is represented by

By repeating the same development, the temperature difference ΔT (n) is obtained by changing the electric wire current values I (n), I (n−1),..., I (1) and the preceding temperature difference ΔT (0). And can be expressed as the following equation (4).

Here, the constant Ct is defined as 1-exp (−n · Δt / τ) using the integer n, the period Δt, and the wire heat dissipation time constant τ described above. When exp (−Δt / τ) is deleted using Ct = 1− {exp (−Δt / τ)} ⁿ and equation (2), equation (2) can be expanded as it can.
Ct = 1- (1-Ca) ⁿ
Therefore, (1-Ca) ⁿ can be expressed as (1-Ct). Then, when (1-Ca) ⁿ in the equation (4) is replaced with (1-Ct), the equation (4) is expanded as the following equation (5).

Since Δt / τ is a positive real number, exp (−Δt / τ) is less than 1. Further, since the heat radiation time constant τ is large and the period Δt is small, exp (−Δt / τ) is approximately equal to 1. Therefore, Ca represented by the equation (2) is sufficiently smaller than 1, and (1-Ca) can be approximated to 1. When approximation is performed in this way, ΔT (n) can be expressed by the following equation (6).

For the right side of equation (6), the first term represents heat generation and the second term represents heat dissipation. Since the constant Ct exceeds zero and is less than 1, (1-Ct) also exceeds zero and is less than 1. For example, if (1-Ct) is 0.8 and the wire current values I (n), I (n-1),..., I (1) are all zero, the temperature difference ΔT (n) is 0.8 · ΔT (0), which indicates that it is 80% of the previously calculated temperature difference. Therefore, when the state where the electric wire current value is zero continues, the temperature difference between the electric wire temperature and the ambient temperature becomes small, and the electric wire temperature approaches the ambient temperature.

In the wire protection process in the nth cycle, the control unit 30 calculates the preceding temperature difference ΔT (0) calculated last time and the wire current value I (1) calculated in the wire protection process in the (n−1) th cycle from the first cycle. ), I (2),..., I (n), and the integrated value of the square values of each, is substituted into the equation (6) to calculate the temperature difference ΔT (n). The control unit 30 calculates the wire temperature by adding a preset ambient temperature to the calculated temperature difference ΔT (n).

The control unit 30 determines whether or not the wire temperature is equal to or higher than the temperature threshold. When it is determined that the wire temperature is equal to or higher than the temperature threshold, the control unit 30 instructs the output unit 34a to change the voltage value indicated by the control signal output from the output unit 34a from the high level voltage value to the low level voltage value. Switch to. Thereby, the drive circuit 22a switches the switch 20a from on to off, and the energization through the electric wire W1 is interrupted.

In the wire protection process in the n period k (k: a natural number less than an integer n) in the execution of the wire protection process, the control unit 30 acquires the wire current value acquired in the wire protection process in the k period from the first period. Whether or not the wire temperature is equal to or higher than the temperature threshold by determining whether or not the integrated value of the square values of I (1), I (2),. Determine whether.

The temperature difference ΔT (k) at the kth cycle is expressed by the following equation (7). The expression (7) is an expression in which the integer n is replaced with a natural number k in the expression (4).

Here, as described above, when (1-Ca) is approximated to 1, equation (7) is expanded as the following equation (8).

Since the value on the right side of the equation (8) is equal to or greater than the temperature difference ΔT (0), the temperature difference ΔT (k) does not decrease from ΔT (0). Therefore, in the equation (8), it is considered that the heat radiation amount is zero.
When the ambient temperature is expressed as Ta (unit: ° C.), the difference between the wire temperature (Ta + ΔT (k)) at the kth cycle and the previously calculated wire temperature (Ta + ΔT (0)) is ΔT (k) −ΔT (0). For this reason, the first term on the right side of equation (8) indicates the temperature increase from the previously calculated wire temperature. When the electric wire temperature (Ta + ΔT (k)) is equal to or higher than the temperature threshold Tth, that is, when Ta + ΔT (k) ≧ Tth is satisfied, the switch 20a is switched from on to off. Ta + ΔT (k) ≧ Tth is developed as follows.

When the right side of the second expression in the above two expressions is defined as the integration threshold Fth, Ta + ΔT (k) ≧ Tth is expressed by the following expressions (9) and (10).

In the right side of equation (10), the only variable is the preceding temperature difference ΔT (0). Therefore, the integrated threshold value Fth is changed based on the preceding temperature difference ΔT (0), that is, the temperature difference calculated by the control unit 30. Further, since the previously calculated wire temperature Tw is represented by Ta + ΔT (0), the integrated threshold Fth is changed based on the wire temperature calculated by the control unit 30.

Therefore, the control unit 30 changes the integrated threshold value Fth every time the wire temperature Tw is calculated, that is, every time the n period related to the execution of the wire protection process elapses. In the wire protection process at the k-th cycle in the n cycle, the control unit 30 determines that the integrated value I (1) ² + I (2) ² +... + I (k) ^{2 of the} square value of the wire current value is the integrated threshold value. By determining whether or not it is equal to or higher than Fth, it is determined whether or not the wire temperature Tw is equal to or higher than the temperature threshold Tth.

When the control unit 30 determines that the integrated value I (1) ² + I (2) ² +... + I (k) ^{2 of the} square value of the electric wire current value is equal to or greater than the integrated threshold Fth, the control unit 30 The voltage value indicated by the control signal output from the output unit 34a is switched from the high level voltage value to the low level voltage value. Thereby, the drive circuit 22a switches the switch 20a from on to off, and the energization through the electric wire W1 is interrupted.

FIG. 3 is a flowchart showing the procedure of the wire protection process for the wire W1. The storage unit 31 stores a counter value for counting the number of cycles, an integrated value of the electric wire current value, and a preceding temperature difference. These are changed by the control unit 30. As described above, the preceding temperature difference is a temperature difference between the previously calculated wire temperature and the ambient temperature.

In the wire protection process, the control unit 30 first increments the counter value by 1 (step S1), and acquires the voltage value across the resistor R1 from the A / D conversion unit 35a (step S2). As described above, since the voltage value across the resistor R1 is proportional to the wire current value of the wire W1, obtaining the voltage value across the wire corresponds to obtaining the wire current value. The electric wire current value is calculated by dividing the product of the voltage value at both ends and the predetermined number described above by the resistance value of the resistor R1. Since the wire protection process is periodically executed, the control unit 30 periodically acquires the voltage value across the resistor R1. The control unit 30 functions as an acquisition unit.

Next, the control part 30 calculates the square value of the electric wire current value which the both-ends voltage value acquired by step S2 shows (step S3). The control unit 30 also functions as a square value calculation unit.
Next, the control unit 30 adds the square value calculated in step S3 to the integrated value stored in the storage unit 31 (step S4). The integrated value stored in the storage unit 31 is changed to the integrated value calculated in step S4.

In the electric wire protection process, when the counter value stored in the storage unit 31 becomes an integer n, the counter value and the integrated value stored in the storage unit 31 are changed to zero. Therefore, the wire protection process whose counter value at the time when Step S1 is executed is the natural number u is the wire protection process of the u-th cycle. In the wire protection process at the u-th cycle, the integrated value at the time when step S4 is executed is I (1) ² + I (2) ² +... + I (u) ² .

Next, the control unit 30 determines whether or not the counter value is an integer n (step S5). When it is determined that the counter value is not the integer n, that is, the counter value is less than the integer n (S5: NO), the control unit 30 determines whether or not the integrated value is greater than or equal to the integration threshold (step S6). ). The integrated value and the integrated threshold used in step S6 are the integrated value and the integrated threshold stored in the storage unit 31, respectively. The control unit 30 also functions as an integrated value determination unit.

When it is determined that the integrated value is less than the integrated threshold (S6: NO), the control unit 30 ends the wire protection process for the wire W1. In this case, after the period Δt has elapsed, the wire protection process for the wire W1 is executed again.

When determining that the integrated value is equal to or greater than the integrated threshold (S6: YES), the control unit 30 instructs the output unit 34a to set the voltage value indicated by the control signal output by the output unit 34a to the low level voltage value. (Step S7). As a result, the drive circuit 22a switches the switch 20a to OFF.

The control part 30 complete | finishes the electric wire protection process of the electric wire W1, after performing step S7. In this case, until the second predetermined condition is satisfied, the control unit 30 does not execute the wire protection process for the wire W1, and keeps the switch 20a off. The second predetermined condition is, for example, that a stop signal indicating the load 11a and an operation signal indicating the operation of the load 11a are sequentially input to the input unit 32.

When the control unit 30 determines that the counter value is an integer n, that is, when it is determined that the currently executed wire protection processing is the n-th cycle wire protection processing (S5: YES), the storage unit 31. Is changed to zero (step S8), and the preceding temperature difference is read from the storage unit 31 (step S9). Next, the control unit 30 calculates the integrated value I (1) ² + I (2) ² +... + I (n) ² calculated in step S4 and the preceding temperature difference ΔT (0) read in step S9. Substituting into the equation (6), the temperature difference ΔT (n) is calculated (step S10).

Therefore, every time the counter value becomes the integer n, that is, every time when the n period related to the execution of the wire protection process elapses, the control unit 30 calculates the n calculated in step S4 of the wire protection process from the 1st cycle to the nth cycle. The temperature difference between the electric wire temperature and the ambient temperature is calculated based on the integrated value of the square values and the preceding temperature difference. The control unit 30 also functions as a temperature difference calculation unit.
In step S10, since the temperature difference is calculated based on the integrated value of the square value of the electric wire current value, it is easy to calculate the temperature difference. In the electric wire protection process, the square value calculated in step S3 is used not only for determination related to the integrated value but also for calculating electric wire temperature.

Next, the control unit 30 calculates the wire temperature of the wire W1 by adding the temperature difference calculated in step S10 to the preset ambient temperature (step S11). Therefore, the control unit 30 executes step S11 every time the counter value reaches the integer n, that is, every time when the n period related to the execution of the wire protection process elapses, and calculates the wire temperature. The control unit 30 also functions as a temperature calculation unit.

After executing step S11, the control unit 30 changes the integrated value stored in the storage unit 31 to zero (step S12), and determines whether or not the wire temperature calculated in step S11 is equal to or higher than the temperature threshold. (Step S13). When it determines with the electric wire temperature being more than a temperature threshold value (S13: YES), the control part 30 performs step S7. As a result, the drive circuit 22a switches the switch 20a to off, and the switch 20a is kept off until the second predetermined condition is satisfied.

When it is determined that the wire temperature is lower than the temperature threshold (step S13: NO), the control unit 30 changes the preceding temperature difference stored in the storage unit 31 to the temperature difference calculated in step S10 (step S14). ). Next, the control unit 30 calculates the integrated threshold value Fth by substituting the preceding temperature difference ΔT (0) changed in step S14 into the equation (10) (step S15). In step S15, a smaller integrated value is calculated as the electric wire temperature calculated in step S11 is higher, that is, as the preceding temperature difference changed in step S14 is higher. Next, the control unit 30 changes the integration threshold value stored in the storage unit 31 to the integration threshold value calculated in Step S15 (Step S16). The control unit 30 also functions as a changing unit.

The control part 30 complete | finishes the electric wire protection process of the electric wire W1, after performing step S16. In this case, after the period Δt has elapsed, the wire protection process for the wire W1 is executed again.

In step S6 of the k-th cycle wire protection process, it is determined whether or not the formula (9) is satisfied. That is, it is determined whether or not the integrated value I (1) ² + I (2) ² +... + I (k) ² is equal to or greater than the integrated threshold Fth. As described in the description of the equation (8), the integrated value I (1) ² + I (2) ² +... + I (k) ² of k square values indicates the increase range of the wire temperature. That is, the increasing range of the wire temperature increases as the power consumption consumed by the wire W1, that is, the integrated value of the square value of the wire current value increases.

The controller 30 changes the integrated threshold value to a smaller value in step S16 as the electric wire temperature calculated in the n-th electric wire protection process is higher, that is, as the electric wire temperature is closer to the temperature threshold value. The integrated threshold indicates an allowable increase in the wire temperature.
Therefore, executing step S6 determines whether or not the increase in the wire temperature during the k period is equal to or greater than the allowable increase in the wire temperature, that is, the wire temperature is equal to or greater than the temperature threshold. This is equivalent to determining whether or not. As a result, in step S6, the control unit 30 performs a determination that is substantially equivalent to the determination related to the wire temperature, using the wire current value.

FIG. 4 is a chart showing the transition of the counter value. As described above, the wire protection process for the wire W2 and the wire protection process for other wires not shown are executed in the same manner as the wire protection process for the wire W1, and the wire protection process for the wires W1, W2,. It is executed almost simultaneously. FIG. 4 shows the transition of the counter value related to the wire protection processing of the wires W1, W2, W3, and W4 when the integer n is 4.

The counter values related to the first wire protection process for the wires W1, W2, W3, and W4 are 1, 2, 3, and 4, respectively. The counter values relating to the second wire protection process for the wires W1, W2, W3, and W4 are 2, 3, 4, and 1, respectively. The counter values related to the third wire protection process for the wires W1, W2, W3, and W4 are 3, 4, 1, and 2, respectively. The counter values related to the fourth wire protection process for the wires W1, W2, W3, and W4 are 4, 1, 2, and 3, respectively. This next wire protection process is the first wire protection process.

In the wire protection process in the nth cycle, that is, in the fourth cycle, the control unit 30 makes a determination related to the wire temperature. In the wire protection processing in the first cycle to the third cycle, the control unit 30 makes a determination related to the integrated value. Do. As shown in FIG. 4, the counter values related to the wire protection processing of the wires W1, W2, W3, and W4 are different from each other. For this reason, the determination related to the wire temperature is always performed in one wire protection process among the four wire protection processes whose start time points substantially coincide with each other, and the determination related to the integrated value is performed in the other three wire protection processes. Is done.

As a matter of course, the processing amount of the control unit 30 related to the calculation of the wire temperature is larger than the processing amount of the control unit 30 related to the calculation of the integrated value. As described above, the counter values related to the wire protection processing of the wires W1, W2, W3, and W4 are different from each other. For this reason, the maximum value of the processing amount of the control unit 30 performed per unit time is small. As the maximum value of the processing amount performed per unit time is larger, it is necessary to use an expensive CPU as the CPU of the control unit 30. In the power supply control device 12, since the maximum value of the processing amount performed per unit time is small, an inexpensive CPU can be used as the CPU of the control unit 30.

Even when the integer n is 2, 3 or 5 or more, the counter values related to the wire protection processing of the n wires W1, W2,... Are different from each other. The maximum processing amount is small.

(Embodiment 2)
In the wire protection process in the first embodiment, the approximation (6) is used for the calculation of the wire temperature. However, equation (5) may be used for calculating the wire temperature.
In the following, the second embodiment will be described while referring to differences from the first embodiment. Since the configuration other than the configuration described below is the same as that of the first embodiment, the same reference numerals as those of the first embodiment are given to the components common to the first embodiment, and the description thereof is omitted.

In the equation (5), the square value I (u) ² (u: natural number) of the electric wire current value is multiplied by a weight coefficient (1-Ca) ^nu . The square value I (u) ² is calculated by the wire protection process in the u period. The storage unit 31 stores a square value of the electric wire current value and a weighting factor in association with the counter value.

FIG. 5 is a chart showing the stored contents of the storage unit 31 in the second embodiment. In FIG. 5, Fu (u: natural number) indicates a square value I (u) ² , and αu indicates a weight coefficient (1-Ca) ^nu . The weight coefficient αn is 1. FIG. 5 shows an example in which the integer n is 4. As shown in FIG. 5, the storage unit 31 stores a square value of the electric wire current value and a weighting factor in association with the counter value. The square value of the electric wire current value is changed by the control unit 30 in the electric wire protection process. The weighting factor is a constant and is set in advance. A table similar to the table shown in FIG. 5 is stored in the storage unit 31 for each of the electric wires W1, W2,. Therefore, the storage unit 31 stores n weighting factors corresponding to the square value of n wire current values.

Hereinafter, the wire protection process for the wire W1 will be described. The wire protection process for the wire W2 and the wire protection process for other wires not shown are performed in the same manner as the wire protection process for the wire W1. For this reason, detailed description of these electric wire protection processes is abbreviate | omitted.

6 and 7 are flowcharts showing the procedure of the wire protection process for the wire W1. Steps S21 to S23, S25 to S29, S32, and S34 to S39 of the wire protection process for the wire W1 in the second embodiment are the same as steps S1 to S3, S4 to S8, S9, and S11 to S16. Therefore, detailed description of steps S21 to S23, S25 to S29, S32, and S34 to S39 is omitted.

After calculating the square value of the electric wire current value in step S23 of the electric wire protection process for the electric wire W1, the control unit 30 sets the square value of the electric wire current value stored in the storage unit 31 to the calculated square value. Change (step S24). In step S24, the square value of the electric wire current value corresponding to the counter value stored in the storage unit 31 is changed. For example, when the counter value is 1, the control unit 30 changes the square value F1 of the wire current value to the calculated square value. After executing step S24, the control unit 30 executes step S25.

After executing Step S29, the control unit 30 multiplies each of the n square values by the corresponding weight coefficient in the n weight coefficients (Step S30). When the integer n is 4, the control unit 30 calculates F1 · α1, F2 · α2, F3 · α3, and F4 · α4. The control unit 30 also functions as a multiplication unit.
Next, the control unit 30 calculates a second integrated value of the n multiplied values multiplied in step S30 (step S31). When the integer n is 4, the second integrated value is F1 · α1 + F2 · α2 + F3 · α3 + F4 · α4. The second integrated value is I (n) ² + (1−Ca) · I (n−1) ² +... + (1−Ca) ⁿ⁻¹ · I (1) ^{2 in} equation (5). It is.

The control unit 30 executes step S32 after executing step S31. After reading the preceding temperature difference in step S32, the control unit 30 reads the preceding temperature difference ΔT (0) and the second integrated value I (n) ² + (1−Ca) · I calculated in step S31. The temperature difference ΔT (n) is calculated by substituting (n−1) ² +... + (1−Ca) ⁿ⁻¹ · I (1) ² into the equation (5) (step S33). .
In step S33, since the equation (5) that is not approximated is used, an accurate temperature difference is calculated. The control unit 30 executes step S34 after executing step S33. In step S34, the wire temperature of the wire W1 is calculated by adding the temperature difference calculated in step S33 to the preset ambient temperature.

The power supply control device 12 according to the second embodiment has an effect obtained by performing a temperature difference calculation based on an integrated value of n square values among the effects exhibited by the power supply control device 12 according to the first embodiment. Except for the other effects.

In the electric wire protection process in the first and second embodiments, the control unit 30 performs the determination related to the integrated value when the counter value is less than the integer n. However, the control unit 30 may perform the determination related to the integrated value when the counter value is equal to or less than the integer n. For example, before determining whether or not the counter value is an integer n, the control unit 30 determines whether or not the integrated value of the square value of the electric wire current value is equal to or greater than an integration threshold value. Then, when it is determined that the integrated value is less than the integrated threshold, the control unit 30 determines whether or not the counter value is an integer n. When the control unit 30 determines that the integrated value is equal to or greater than the integration threshold value, the control unit 30 instructs one of the output units 34a, 34b,... To switch the voltage value indicated by the control signal to the low level voltage value. . When it is determined that the counter value is not the integer n, the control unit 30 ends the wire protection process.

In Embodiments 1 and 2, the temperature difference between the wire temperature and the ambient temperature may be calculated based on the wire current value, and the wire temperature may not be calculated by adding the ambient temperature to the calculated temperature difference. . The wire temperature may be calculated based on the wire current value.
Furthermore, in the first and second embodiments, the switches 20a, 20b,... Are not limited to N-channel FETs, but may be P-channel FETs, bipolar transistors, relay contacts, or the like.

The disclosed first and second embodiments are examples in all respects, and should not be considered as restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Power supply system 10 Battery 11a, 11b Load 12 Electric power feeding control apparatus 20a, 20b Switch 21a, 21b Current output circuit 22a, 22b Drive circuit 23 Microcomputer 30 Control part (acquisition part, square value calculation part, temperature calculation part, integrated value determination) Part, change part, temperature difference calculation part, multiplication part)
31 storage unit 32, 33a, 33b input unit 34a, 34b output unit 35a, 35b A / D conversion unit 36 bus E1 storage medium P1 computer program R1, R2 resistance W1, W2, W3, W4 electric wire

Claims (6)

1. A power supply control device for controlling power supply via an electric wire,
   An acquisition unit for periodically acquiring the value of the electric wire current flowing through the electric wire;
   A square value calculation unit for calculating a square value of the electric wire current value acquired by the acquisition unit;
   A temperature calculating unit that calculates the wire temperature of the wire each time an n period (n: an integer of 2 or more) related to the acquisition of the wire current value elapses;
   It is determined whether or not the integrated value of the k square values calculated by the square value calculation unit in the k period (k: a natural number equal to or less than n) from the first period of the n period is equal to or greater than an integration threshold. An integrated value determination unit to perform,
   A power supply control device comprising: a change unit that changes the integrated threshold value to a smaller value as the electric wire temperature calculated by the temperature calculation unit is higher.
2. Each time the n period elapses, a temperature difference between the wire temperature and a predetermined temperature based on the n square values calculated by the square value calculation unit from the first period to the n period of the n period. A temperature difference calculation unit for calculating
   The power supply control device according to claim 1, wherein the temperature calculation unit calculates the wire temperature by adding the temperature difference calculated by the temperature difference calculation unit to the predetermined temperature.
3. The temperature difference calculation unit calculates a temperature difference between the wire temperature and the predetermined temperature based on an integrated value of the n square values and a preceding temperature difference between the wire temperature and a predetermined temperature calculated in advance. The power supply control device according to claim 2.
4. A storage unit storing n weighting factors corresponding to the n square values;
   A multiplier that multiplies each of the n square values by a corresponding weighting factor in the n weighting factors,
   The temperature difference calculation unit is configured to calculate the wire temperature and the predetermined temperature based on an integrated value of the n multiplied values multiplied by the multiplication unit and a preceding temperature difference between the wire temperature and the predetermined temperature calculated in advance. The power supply control device according to claim 2, wherein a temperature difference is calculated.
5. A power supply control method for controlling power supply via an electric wire,
   Periodically obtaining a current value of a wire flowing through the wire;
   Calculating a square value of the acquired electric wire current value;
   Calculating the wire temperature of the wire each time n (n: an integer greater than or equal to 2) period for obtaining the wire current value elapses;
   Determining whether or not an integrated value of the k square values calculated from the first cycle of the n cycle to the k (k: natural number of n or less) cycle is equal to or greater than an integration threshold;
   And a step of changing the integrated threshold value to a smaller value as the calculated wire temperature is higher.
6. On the computer,
   Periodically obtaining the value of the electric wire current flowing through the electric wire;
   Calculating a square value of the acquired electric wire current value;
   Calculating the wire temperature of the wire each time n (n: an integer greater than or equal to 2) period for obtaining the wire current value elapses;
   Determining whether or not an integrated value of the k square values calculated from the first cycle of the n cycle to the k (k: natural number of n or less) cycle is equal to or greater than an integration threshold;
   A computer program for executing the step of changing the integrated threshold to a smaller value as the calculated electric wire temperature is higher.

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