JP2014072919A - Current detecting device and power supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detecting device which can resume detection of a current value within a prescribed time even in the case of failing in detection of the current value of a current which is intermittently supplied to a load.SOLUTION: The current detecting device which repeatedly detects the current value of a current intermittently supplied to a load has: a determination section which determines whether or not the detected current value is less than a predetermined value; and a change section which changes a detection timing of the current value when the determination section has determined that the detected current value is less than a predetermined value.

Description

  The present invention relates to a current detection device capable of controlling the detection timing of a current value intermittently supplied to a load, and a power supply control device including the current detection device.

  A load such as a motor and a lighting fixture is mounted on the vehicle, and the load is connected to a power source via an electric wire. Power supply to the load is controlled by PWM (pulse width modulation), and the number of rotations, brightness, and the like of the motor are controlled. There is a possibility that the inner core wire contacts the surrounding conductor structure and short-circuits due to aging deterioration such as wear. Generally, in order to prevent damage to an electric wire or a load due to a short circuit, a thermal fuse is interposed at an appropriate portion of the electric wire.

  However, in order to use a thermal fuse, it is necessary to secure an installation space, and there is a problem that the number of parts increases. In addition, when energizing a load with a large inrush current is repeated, the fusing time tends to be shortened due to deterioration of the thermal fuse, so it is necessary to use a thermal fuse with a certain amount of current capacity. There was a problem that it was necessary to use an electric wire that could withstand. Further, when the thermal fuse is blown, it is necessary to replace it with a new thermal fuse, and there is a problem that labor is required for maintenance work.

  As a method for solving such a problem, a thermal fuse interposed in the electric wire is virtually assumed, the temperature of the thermal fuse is estimated based on the current value, and the temperature of the thermal fuse reaches the allowable limit temperature. In such a case, a protection device that cuts off the power supply from the power source to the load using a cutoff switch such as a relay is disclosed (for example, Patent Document 1). Specifically, the microcomputer provided in the protection device detects the electric current value of the electric wire at every predetermined time according to the PWM control ON time, and the relational expression of the detected electric current value, heat generation and heat dissipation of the thermal fuse is obtained. And calculating a temperature rise value of the thermal fuse in the predetermined time. Then, the temperature of the thermal fuse is calculated by adding the integration result of the temperature rise values calculated every predetermined time to the ambient temperature at the start of energization.

JP 2010-177181 A

  However, in the conventional protection device, the current value may be detected because the detection timing of the current value corresponds to the OFF time of the PWM control. Since the current value detection cycle is synchronized with the PWM control cycle, once the current value detection timing reaches the PWM control ON time, the current value is not detected and accurate current value information is obtained. There was a problem that it was impossible. If the state where the current value is not detected continues, the temperature of the thermal fuse cannot be accurately estimated.

  The present invention has been made in view of such circumstances, and its purpose is to resume detection of a current value within a predetermined time even when detection of a current value intermittently supplied to a load fails. An object of the present invention is to provide a current detection device capable of performing the above and a power supply control device including the current detection device.

  The current detection device according to the present invention is a current detection device that repeatedly detects a current value intermittently supplied to a load, and a determination unit that determines whether or not the detected current value is less than a predetermined value. And a change unit that changes the detection timing of the current value when the current value is determined to be less than the predetermined value.

  In the present invention, when the current value is detected at a timing when power is not supplied to the load, the current value becomes less than a predetermined value. When the detected current value is less than the predetermined value, the current value detection timing is changed. By changing the detection timing of the current value, the current value can be detected at the timing when power is supplied to the load.

  In the current detection device according to the present invention, the power supply to the load is PWM-controlled, and the current value is detected at a cycle that is an integral multiple of the PWM control cycle. A first timing changing unit that moves back and forth by the control on-time and a second timing changing unit that drives the current value detection timing back and forth by the off-time of the PWM control are provided.

  In the present invention, the power supply to the load is PWM controlled, and the current detection device detects the current value at a cycle that is an integral multiple of the PWM control cycle. The changing unit moves the current value detection timing around the PWM control on-time, or moves the current value detection timing around the PWM control off-time to detect the current value during the PWM control on-time. Can be in a state.

  A current detection device according to the present invention includes a storage unit that stores a duty ratio of PWM control, and when the duty ratio of PWM control is smaller than a predetermined duty ratio range, the first timing change unit changes a detection timing of a current value. When the duty ratio of PWM control is larger than the predetermined duty ratio range, the second timing changing unit changes the detection timing of the current value.

In the present invention, when the duty ratio is smaller than the predetermined duty ratio range, the current value can be detected by changing the detection timing at most twice by changing the detection timing of the current value by about the ON time of the PWM control. It is possible to make it happen. The predetermined duty ratio range is not necessarily a wide range of several percent, and may be, for example, 50% and a tolerance range thereof.
When the duty ratio is larger than the predetermined duty ratio range, the current value can be detected by changing the detection timing once by changing the detection timing of the current value by the PWM control OFF time. It is.

  The current detection device according to the present invention is characterized in that when the duty ratio of the PWM control is within the predetermined duty ratio range, the second timing changing unit changes the detection timing of the current value.

  In the present invention, when the duty ratio of the PWM control is within the predetermined duty ratio range, the current value is detected by changing the detection timing once by changing the detection timing of the current value by the PWM control off time. It is possible to make a state in which detection is performed.

  In the current detection device according to the present invention, when the duty ratio of the PWM control is within the predetermined duty ratio range, the changing unit moves the detection timing of the current value around half the PWM control on-time, or A third timing changing unit is provided that moves back and forth by half the PWM control OFF time.

  In the present invention, when the duty ratio of the PWM control is within the predetermined duty ratio range, the detection timing of the current value is changed by about half of the on time of the PWM control, or half of the off time of the PWM control. By changing the detection timing back and forth by this time, the current value can be detected by changing the detection timing a maximum of two times.

  In the current detection device according to the present invention, the first timing changing unit determines that the current value detected after the current value detection timing is advanced (or delayed) by the on-time of the PWM control is less than a predetermined value. In this case, the current value detection timing is delayed (or advanced) by a time twice as long as the PWM control ON time.

In the present invention, when it is determined that the current value detected after the current value detection timing is advanced by the PWM control ON time is less than the predetermined value, the current value detection timing is set to the PWM control ON time. By delaying the time twice as long as this, the detection of the current value can be performed by changing the detection timing twice at the maximum.
Similarly, when it is determined that the current value detected after delaying the current value detection timing after the PWM control on-time is less than the predetermined value, the current value detection timing is twice the PWM control on-time. By advancing the time, the current value can be detected by changing the detection timing at most twice.

  A power supply control device according to the present invention includes any one of the above-described current detection devices and a PWM control unit that performs PWM control of power supply to the load.

  In the present invention, power supply control to the load is performed by PWM control.

  The power supply control device according to the present invention includes a timing instruction unit that instructs the PWM control unit to start the start time of the PWM control so that the current detection timing becomes the ON time of the PWM control.

  In the present invention, the timing instruction unit instructs the PWM control unit to start timing of the on-time of the PWM control. By instructing the start timing to the PWM control unit, it becomes possible to start the detection of the current value from the ON time at the start of the PWM control.

  The power supply control device according to the present invention includes a calculation unit that calculates a temperature of the load or an electric wire connected to the load based on the detected current value, and the temperature calculated by the calculation unit is equal to or higher than a predetermined temperature. A temperature determining unit that determines whether or not there is a shut-off switch that shuts off power supply to the load when the temperature determining unit determines that the temperature is equal to or higher than a predetermined temperature;

  In the present invention, the temperature of the load or the electric wire is calculated based on the detected current value. When the calculated temperature is equal to or higher than the predetermined temperature, power supply to the load is interrupted.

  According to the present invention, even when detection of a current value intermittently supplied to a load fails, detection of a current value can be resumed within a certain time.

It is the block diagram which showed the example of 1 structure of the electric power feeding system which concerns on this Embodiment. It is the block diagram which showed the example of 1 structure of electric power feeding control apparatus and body ECU. It is the flowchart which showed the process sequence of the control part which concerns on electric power feeding. 5 is a timing chart showing PWM control start timing. It is the flowchart which showed the process sequence of the control part which concerns on electric current detection. It is the table which showed the change method of electric current detection timing. It is a timing chart which showed the change method of the electric current detection timing in case a duty ratio exceeds 50%. It is a timing chart which showed the change method of the electric current detection timing in case a duty ratio is 50% or less. It is a timing chart which showed the change method of the electric current detection timing in case a duty ratio is 50% or less. It is the flowchart which showed the process sequence of the control part which concerns on the electric current detection of a modification. It is the flowchart which showed the process sequence of the control part which concerns on the electric current detection of a modification. It is the table which showed the change method of the electric current detection timing which concerns on a modification. 6 is a timing chart showing a method for changing the current detection timing when the duty ratio is more than 40% and 50% or less. 6 is a timing chart showing a method for changing the current detection timing when the duty ratio is more than 40% and 50% or less.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a block diagram illustrating a configuration example of a power feeding system according to the present embodiment. The protection system according to the present embodiment includes a power supply control device 1, a body ECU 2, a power source 3, and a load 51 that are mounted on a vehicle 5. The load 51 is, for example, a headlight, a room light, a wiper, or the like. The positive terminal of the load 51 is connected to the positive terminal of the power source 3 via the electric wire 6, and the negative terminal of the load 51 is grounded. A power supply switch 7 is provided at an appropriate position of the electric wire 6, and the opening and closing of the power supply switch 7 is controlled by the body ECU 2, and power supply to the load 51 is controlled. In addition, a power supply control device 1 having a function of protecting the electric wire 6 and the load 51 from heat generation due to an overcurrent or the like is provided at an appropriate position of the electric wire 6 while performing PWM control of electric power supply to the load 51. The power supply control device 1 and the body ECU 2 are connected by a communication line 4 such as an in-vehicle LAN.

  FIG. 2 is a block diagram illustrating a configuration example of the power supply control device 1 and the body ECU 2. The power supply control device 1 includes a microcomputer 11. The microcomputer 11 includes a control unit 11a that controls the operation of each component of the microcomputer 11, for example, one or a plurality of CPUs (Central Processing Units), a multi-core CPU, and the like. A ROM 11b, a first storage unit 11c, a timer 11d, a CAN (Controller Area Network) communication I / F 11e, and an I / F unit 11f are connected to the control unit 11a via a bus.

  The ROM 11b is a nonvolatile memory such as an EEPROM (Electrically Erasable Programmable ROM), and stores a computer program for performing current detection, temperature calculation processing, and power supply interruption processing according to the present embodiment.

  The first storage unit 11c is a memory such as a DRAM (Dynamic RAM), an SRAM (Static RAM), and the like. The computer program read from the ROM 11b when executing the calculation process of the control unit 11a, or the calculation of the control unit 11a Various data generated by the processing are temporarily stored. For example, the first storage unit 11c stores a duty ratio necessary for power supply PWM control.

  The timer 11d generates a clock for measuring the current detection timing, and the first control unit 11a controls the detection timing of the current value with reference to the clock of the timer 11d. In addition, the timer 11d measures the current time, for example, the time, and gives a timing result to the control unit 11a in accordance with a request from the control unit 11a.

  The CAN communication I / F 11e is connected to the body ECU 2 mounted on the vehicle 5 via the communication line 4, and transmits / receives data to / from the body ECU 2 according to the CAN protocol. The CAN communication I / F 11e transmits the data given from the control unit 11a, and gives the data received from the body ECU 2 to the control unit 11a. Thus, the power supply control device 1 can send a control command or the like to the body ECU 2 to request a predetermined operation from the body ECU 2, and can detect information from the body ECU 2 by the CAN communication I / F 11e.

  A temperature detector 12 and an IPD (Intelligent Power Device) 13 are connected to the I / F unit 11f. The temperature detection unit 12 includes, for example, a thermistor, and detects the ambient temperature of the power supply control device 1 by detecting the electrical resistance of the thermistor that varies depending on the temperature.

  The IPD 13 includes a relay (cutoff switch) 13b and a PWM control unit 13d that are interposed in series between the power source 3 and the load 51. The relay 13b is, for example, a semiconductor relay or a mechanical relay composed of an IGBT, a power MOSFET, and the like. One end of the relay 13b is connected to the positive electrode of the power supply 3 via the power supply switch 7, and the other end of the PWM control unit 13d. Connected to the input terminal. The relay 13b opens and closes according to a control signal given from the control unit 11a via the I / F unit 11f.

The PWM control unit 13d operates in accordance with a control signal supplied from the control unit 11a via the I / F unit 11f. For example, the control unit 11a operates the PWM control unit 13d so that power is supplied to the load 51 at the duty ratio by giving the PWM control unit 13d a start command signal instructing the start of PWM control and the duty ratio. Let The PWM controller 13d intermittently supplies power to the load 51 by periodically turning on and off the switch using the clock of the timer 13c. The PWM control unit 13d controls the ratio between the on time and the off time in accordance with the duty ratio given from the control unit 11a. Further, the control unit 11a can adjust the start time of the on-time when starting the PWM control by giving the PWM control unit 13d a start timing instruction signal that instructs the start timing of the on-time of the PWM control. . Further, the control unit 11a can stop the operation of the PWM control unit 13d by giving the PWM control unit 13d an end command signal for instructing the end of the PWM control.
2 shows a configuration in which a clock necessary for PWM control is input from the external timer 13c to the PWM control unit 13d. However, the configuration is such that PWM control is performed using the internal clock of the PWM control unit 13d. You may do it. In the above example, the configuration in which the microcomputer 11 gives the duty ratio to the IPD 13 has been described. However, the PWM control signal of the rectangular pulse signal is given to the IPD 13, and the PWM control switch provided in the IPD 13 is controlled by the PWM control signal. You may comprise so that it may be turned on and off.

  The IPD 13 includes a current detection unit 13 a that detects a current value flowing through the electric wire 6. The current detection unit 13a is, for example, a hall element sensor. The Hall element sensor detects a magnetic field generated by the current flowing through the electric wire 6 by the Hall element, amplifies the Hall voltage generated in the Hall element by the magnetic field, and outputs the amplified current as a current value. A series resistance type sensor may also be used. The series resistance type current detection unit 13 a detects a current value from a voltage drop in a resistor connected in series to the electric wire 6. Thus, the current value output from the current detection unit 13a is represented by the magnitude of the voltage.

  The body ECU 2 is a control device that controls body-based in-vehicle devices, and controls in-vehicle devices such as headlights, turn hazards, wipers, and door lock mechanisms mounted on the vehicle 5. That is, the body ECU 2 receives user operations, controls turning on and off of headlights and turn hazards, on / off or intermittent operation of wipers, and controls locking / unlocking of the door lock mechanism. Specifically, the body ECU 2 includes a control unit 21 that controls the operation of each component of the body ECU 2. The control unit 21 is, for example, one or a plurality of CPUs, a multi-core CPU, and the like. The control unit 21 is connected to the ROM 22, the second storage unit 23, the CAN communication I / F 24, the clock unit 25, and the I / F via a bus. The unit 26 is connected.

  The ROM 22 is a nonvolatile memory such as an EEPROM, and stores a computer program for holding and providing information necessary for the temperature calculation process according to the present embodiment.

  The second storage unit 23 is a memory such as a DRAM or an SRAM, and temporarily stores a computer program read from the ROM 22 when the calculation process of the control unit 21 is executed, and various data generated by the calculation process of the control unit 21. To do.

  The CAN communication I / F 24 is connected to the power supply control device 1 mounted on the vehicle 5 and other various ECUs (not shown) via the communication line 4, and transmits and receives data according to the CAN protocol. The CAN communication I / F 24 transmits data given from the control unit 21 and gives data received from other ECUs to the control unit 21. As a result, the body ECU 2 can detect information obtained from the in-vehicle devices connected to the various ECUs by the CAN communication I / F 24 and transmit an operation command to the in-vehicle devices connected to the other ECUs. The operation of the in-vehicle device can be controlled.

  The power supply switch 7 is connected to the I / F unit 26, and the control unit 21 controls power supply to the load 51 by giving an open / close signal to the power supply switch 7 via the I / F unit 26. For example, when the headlight is turned on by the user, the control unit 21 supplies a close signal to the power supply switch 7 via the I / F unit 26 to supply power to the load 51 that is a headlight. When the user turns off the headlight, the control unit 21 provides an open signal to the power supply switch 7 through the I / F unit 26 to cut off the power supply to the load 51 that is the headlight.

  FIG. 3 is a flowchart illustrating a processing procedure of the control unit 11a related to power feeding. The control unit 11a performs drive control on the PWM control unit 13d (step S11). Specifically, the control unit 11a receives a start command signal and a duty ratio for instructing start of PWM control via the I / F unit 11f, and a start timing instruction signal for instructing start timing of the on-time of PWM control. This is given to the PWM controller 13d. The duty ratio is a value determined by the control unit 11a according to the operation content of the user, and is stored in the first storage unit 11c. The user's operation content is input to the CAN communication I / F 11e via the communication line 4, for example.

  FIG. 4 is a timing chart showing the PWM control start timing. In FIG. 4, the block drawn on the upper part shows the periodic structure of the control performed by the control unit 11a. The control unit 11a executes control processing with 10 ms as one cycle. In each cycle, the control unit 11a sequentially executes an external information input process, an external device control process, and an external information output process. In the figure, a block described as “input” indicates a period during which the input process is executed, a block described as “control” indicates a period during which the control process is executed, and a block described as “output” indicates an output. The period during which the process is executed is shown. Then, when the input process, the control process, and the output process are finished within the range of 10 ms, the control unit 11a waits until the next cycle is started. A block described as “IDLE” indicates a period in which the control unit 11a is waiting until the start of the next cycle.

In the period corresponding to the block described as “output”, the control unit 11a executes the process of step S11 for supplying the start command signal, the duty ratio, and the start timing instruction signal to the PWM control unit 13d. Then, as described later, after the PWM control of power feeding is started, the current value input process is executed in a period corresponding to the block described as “input”, that is, at the timing when the control cycle starts. . The current value input process is a process in which the control unit 11a acquires the detection value output from the current detection unit 13a via the I / F unit 11f.
By the way, as shown in the upper timing chart of FIG. 4, when the PWM control on-time starts at the timing when the start command signal is given to the PWM control unit 13d, the timing for acquiring the current value is the PWM control off-time. May hit. That is, the timing for acquiring the current value may correspond to a period during which no current flows through the electric wire 6, and the detection of the current value will fail from the beginning.

  Therefore, the control unit 11a gives a timing instruction signal to the PWM control unit 13d so that the on-time of the PWM control is started in accordance with the timing of executing the current value input process. For example, the control unit 11a refers to the time measurement result of the timer 11d and calculates the time from the current time to the time when the current value input process is executed. Also, a predetermined time, for example, 1 to 2 ms, is subtracted from the calculated time in order to provide a certain margin between the timing at which the PWM control on-time is started and the timing at which the current value input processing is started. To do. Then, the control unit 11a gives a start timing instruction signal to the PWM control unit 13d so that the PWM control is started with a delay by the calculated time. In this way, by controlling the start timing of PWM control, the detection timing of the current value and the on-time of PWM control can be matched at the start time of PWM control. The lower timing chart of FIG. 4 shows a state where the detection timing of the current value matches the on-time of the PWM control.

  Next, the control unit 11a determines whether or not it is a current detection timing (step S12). The controller 11a is basically configured to detect a current value at a period that is an integral multiple of the PWM control period, and should calculate the temperature of the electric wire 6 every time a time that is an integral multiple of the PWM control period elapses. It is determined that it is a predetermined detection timing. However, the predetermined detection timing is appropriately changed when the detection of the current value fails. Here, an example will be described in which a current value is detected every 10 ms, which is a PWM control cycle.

  When it is determined that it is not the detection timing at which the temperature of the electric wire 6 is to be calculated (step S12: NO), the control unit 11a performs the process of step S12 again and waits until the predetermined detection timing is reached. Actually, control of an external device, output processing of information to the outside, and the like are executed, but details are omitted. When it determines with it being the predetermined detection timing which should calculate the temperature of the electric wire 6 (step S12: YES), the control part 11a calls the subroutine which concerns on the electric current detection part 13a, and detects an electric current value (step S13). Details of the current value detection method will be described later.

  Next, the control unit 11a calculates the temperature increase value of the electric wire 6 based on the current value detected in step S13 and the temperature increase value calculated at the previous detection timing, and adds the calculated temperature increase value to the ambient temperature. Thus, the temperature of the electric wire 6 is calculated (step S14). For example, the temperature rise value of the electric wire 6 is calculated using the following formulas (1) to (4).

ΔTw (n) = Qw (n) / Cwth (1)
Q (w) = Qw (n−1) + (Pwin−Pwout) × Δt (2)
Pwin = rw × I (n) ² (3)
Pwout = Qw (n−1) / (Cwth × Rwth) (4)
However,
ΔTw: Temperature rise value Qw (n): Heat amount of the wire 6 at the n-th detection (the heat amount of the wire 6 at the ambient temperature is set to 0)
Δt: detection time interval Cwth: heat capacity of the electric wire 6 [J / ° C.]
rw: electric resistance of the electric wire I: current flowing through the electric wire 6 Rwth: thermal resistance of the electric wire 6 [° C./W]

The amount of heat Qw (n−1) at the previous detection timing is expressed by the following equation (5) using the temperature increase value ΔTw (n−1) at the detection timing.
Qw (n−1) = ΔTw (n−1) × Cwth (5)

  Further, at the first detection timing, the heat quantity Qw (0) at the previous detection timing is zero.

The temperature of the electric wire 6 is calculated using, for example, the following formula (6). The ambient temperature is a temperature detected by the temperature detector 12.
T = Ta + ΔTw (6)
However,
Ta: Ambient temperature

  Next, the control unit 11a determines whether or not the relay 13b is in a disconnected state (step S15). Since the control unit 11a controls the opening and closing of the relay 13b, the state of the relay 13b is grasped by the control unit 11a. When it determines with not being in the interruption | blocking state (step S15: NO), the control part 11a determines whether the calculated temperature of the electric wire 6 is more than predetermined temperature (step S16). When it determines with the temperature of the electric wire 6 being more than predetermined temperature (step S16: YES), the control part 11a cuts off the electric power feeding to the load 51 through the electric wire 6 by opening the relay 13b (step S17). ), The process returns to step S12. When it determines with the temperature of the electric wire 6 being less than predetermined temperature (step S16: NO), the control part 11a returns a process to step S12.

  When it determines with it being in the interruption | blocking state by step S15 (step S15: YES), the control part 11a determines whether it can reset (step S18). For example, the control unit 11a determines whether or not recovery is possible by determining whether or not a certain period of time has elapsed since the relay 13b is in a disconnected state. Further, it is determined whether or not the electric wire 6 can be restored by determining whether or not the temperature of the electric wire 6 has become lower than a second predetermined temperature that is lower than the predetermined temperature. When it determines with resetting being possible (step S18: YES), the control part 11a connects the relay 13b to a closed state, and restarts the electric power feeding to the load 51 through the electric wire 6 (step S19), and performs a process step Return to S12. If it is determined that the return is impossible (step S18: NO), the controller 11a returns the process to step S12 while keeping the relay 13b open.

  FIG. 5 is a flowchart showing a processing procedure of the control unit 11a related to current detection. The control unit 11a that has called a subroutine relating to current detection detects a current value in the current detection unit 13a (step S31). Specifically, the control unit 11a acquires the current value output from the current detection unit 13a via the I / F unit 11f. And the control part 11a determines whether the detected electric current value is less than predetermined value (step S32). Step S32 is a process of confirming whether or not the detection of the current value has failed. The predetermined value is set as a threshold value for determining the current value to be 0 in consideration of the noise level characteristic of the AD conversion unit included in the I / F unit 11f of the microcomputer 11. For example, when the input voltage of the I / F unit 11f is 5V, 1V that is 20% may be set as the predetermined value.

  When it determines with the detected electric current value being more than predetermined value (step S32: NO), the control part 11a complete | finishes a process. When it determines with the detected electric current value being less than predetermined value (step S32: YES), the control part 11a complements the electric current value replaced with the electric current value which failed in detection in step S31 (step S33). Specifically, the control unit 11a discards the current value acquired in step S31, and stores the current value detected at the previous detection timing as the current value detected at the current detection timing.

  Control part 11a which finished processing of Step S33 judges whether a duty ratio is over 50% (Step S34). The 50% is an example of a predetermined duty ratio range. When it is determined that the duty ratio is greater than 50% (step S34: YES), the control unit 11a adds the OFF time of the PWM control to the reference timing, and the time obtained by the addition is the time of the next detection timing. (Step S35), and the process related to current detection is completed. The reference timing is, for example, 10 ms, which is the same as the PWM control cycle, and indicates the time from the current time to the next current value detection in a normal state where the current value is being detected smoothly. . The detection timing indicates the timing at which the current value is actually detected with reference to the current time in consideration of the success or failure of the current value detection. When step S35 is executed, the next current value detection is performed at a timing delayed by the OFF time of the PWM control from the normal detection timing (see FIG. 7).

  When it is determined that the duty ratio is 50% or less (step S34: NO), the control unit 11a determines whether or not the next current value detection is the first re-detection performed after the current value detection failure. Determination is made (step S36). Note that the number of times of re-detection may be stored in the first storage unit 11c as the number of times that the current value detection has subsequently failed. If the number of failures is 1, the next current value detection is the first redetection, and if the number of failures is 2, the next current value detection is the second redetection.

  When it is determined that the next current value detection is the first re-detection (step S36: YES), the control unit 11a adds the ON time of the PWM control to the reference timing, and the time obtained by the addition is calculated the next time. The detection timing time is set (step S37), and the process ends. When step S37 is executed, the next current value detection is performed at a timing delayed by the on-time of the PWM control from the normal detection timing (see FIG. 8).

  When it is determined that the next current value detection is the second re-detection (step S36: NO), the control unit 11a subtracts and subtracts the time twice as long as the PWM control on-time from the reference timing. The time is set as the time of the next detection timing (step S38), and the process ends. When step S38 is executed, the next current value detection is performed at a timing earlier than the normal detection timing by the on-time of the PWM control (see FIG. 9). Since the current value is detected at the detection timing delayed by the PWM control on-time in the first re-detection, the detection timing is advanced only twice the next time of the PWM control on-time by the second re-detection. As a result, in the second redetection, the current value is detected at a detection timing that is earlier by the PWM control on-time than the normal detection timing at which the current value is normally detected.

  As described above, when the detected current value is less than the predetermined value, that is, when the detection of the current value fails, the control unit 11a changes the detection timing of the next current value according to the magnitude of the duty ratio. Thus, an attempt is made to match the detection timing of the current value with the on-time of the PWM control. According to the above-described processing, the current value can be successfully detected by matching the detection timing of the current value to the on-time of the PWM control by performing re-detection twice. Hereinafter, a method for redetecting the current value will be described.

  FIG. 6 is a table showing a method for changing the current detection timing. When the detection of the current value fails, the control unit 11a changes the detection timing of the current value as shown in the table of FIG. From the left column to the right column of the table, the PWM control cycle, duty ratio, PWM control on-time, off time, reference timing, redetection first detection timing changing method, and first redetection detection timing The method of changing the detection timing for the second detection is shown, and the detection timing for the second detection is shown. Here, a specific detection timing changing method is shown when the PWM control cycle is 10 ms, the reference timing is 10 ms, and the duty ratio is 10%, 20%... 80%, 90%.

FIG. 7 is a timing chart showing a method for changing the current detection timing when the duty ratio exceeds 50%. The rectangular pulse shown in FIG. 7 indicates the on / off state of PWM control, and the circle indicates the timing at which the current value is detected. A white circle indicates that the current value has been successfully detected, and a black circle (hatched circle) indicates that the current value has failed to be detected. As is clear from FIG. 7, when the current value fails to be detected when the duty ratio exceeds 50%, the current value detection timing is advanced by advancing the next detection timing of the current value by the PWM control off-time. Can be adjusted to the on-time of PWM control. The current value can be detected only by trying one redetection.
Note that the next detection timing may be delayed by the PWM control off time. Also in this case, the detection timing of the current value can be matched with the on-time of the PWM control only by trying one re-detection.

  8 and 9 are timing charts showing a method of changing the current detection timing when the duty ratio is 50% or less. As shown in FIG. 8, when the duty ratio is 50% or less and the current value detection timing precedes the PWM control ON time and fails to detect the current value, the next detection timing of the current value. The current value detection timing can be matched with the PWM control on-time by advancing the signal by the PWM control on-time. In this case, the current value can be detected only by trying one redetection.

  However, as shown in FIG. 9, when the duty ratio is 50% or less, when the current value detection timing is delayed with respect to the PWM control ON time and the current value detection fails, the next time the current value is detected. Even if the detection timing is advanced by the PWM control ON time, the current value detection timing cannot be matched with the PWM control ON time. In this case, the detection timing of the current value can be matched with the ON time of the PWM control by delaying the subsequent current detection timing by a time twice as long as the ON time of the PWM control. In this case, the current value can be detected only by trying the re-detection twice.

The next detection timing may be delayed by the PWM control on-time, and the next detection timing may be advanced by twice the PWM control on-time. In this case as well, the detection timing of the current value can be matched with the on-time of the PWM control only by trying the re-detection twice at the maximum.
When the duty ratio is 50%, the method shown in FIG. 7, that is, the next detection timing may be delayed by the OFF time of PWM control. In this case, the detection timing of the current value can be adjusted to the on-time of the PWM control only by trying one re-detection, and the detection timing of the current value can be adjusted to the on-time of the PWM control earlier.

  In the present invention, even when the detection of the current value intermittently supplied to the load 51 fails, the detection of the current value can be restarted by the maximum of two re-detections.

  Moreover, based on the detected current value, the temperature of the load 51 or the electric wire 6 is calculated, and the electric power supply to the load is cut off according to the calculated temperature, thereby protecting the electric wire 6 and the load 51. be able to.

(Modification)
10 and 11 are flowcharts showing a processing procedure of the control unit 11a according to the current detection of the modification. Since the power supply control device 1 according to the modification differs in the detection timing changing method when PWM control is performed with a duty ratio of 40 to 60%, the following mainly describes the difference. The duty ratio of 40 to 60% is an example of a predetermined duty ratio range. The predetermined duty ratio range is an intermediate range of 0% to 100%, and a specific numerical range may be set as appropriate so that the current value detection success probability is high.
The PWM-controlled current value is not turned on and off in an ideal rectangular pulse shape. That is, in reality, the current application state does not discontinuously instantaneously switch from the on state to the off state, and the voltage gradually increases or decreases from the on state to the off state, although it is a very short time. . In other words, the voltage applied to the electric wire by PWM control rises diagonally from the off state and shifts to the on state, and falls diagonally from the on state and shifts to the off state.
For this reason, especially when the duty ratio is 50% and the detection timing at which the detection of the current value has failed is exactly the same as the ON / OFF switching timing of the PWM control, the detection timing is made to be before or after the ON time or OFF time. However, the current value may be detected again at the on / off switching timing of the PWM control, and the current value may fail to be detected or an incorrect current value may be detected. This is because the current value is in a state where the current value changes from the energized state to the energized stop state or from the energized stop state to the energized state at the timing when the power supply is turned on / off by PWM control, and the current value is not stable. The modification solves such a problem.

  The control unit 11a that has called a subroutine relating to current detection detects a current value in the current detection unit 13a (step S51), and determines whether or not the detected current value is less than a predetermined value (step S52). . When it determines with the detected electric current value being more than predetermined value (step S52: NO), the control part 11a complete | finishes a process. When it determines with the detected electric current value being less than predetermined value (step S52: YES), the control part 11a supplements the electric current value replaced with the electric current value which failed in detection in step S51 (step S53).

  Control part 11a which finished processing of Step S53 judges whether a duty ratio is over 60% (Step S54). When it is determined that the duty ratio exceeds 60% (step S54: YES), the control unit 11a adds the off time of the PWM control to the reference timing, and uses the time obtained by the addition as the time of the next detection timing. (Step S55), and the process related to current detection is completed.

  When it is determined that the duty ratio is 60% or less (step S54: NO), the control unit 11a determines whether or not the duty ratio is greater than 50% (step S56). When it is determined that the duty ratio exceeds 50% (step S56: YES), the control unit 11a determines whether or not the next current value detection is the first re-detection performed after the current value detection failure. Determination is made (step S57). When it is determined that the next current value detection is the first re-detection (step S57: YES), the control unit 11a adds half the PWM control OFF time to the reference timing, and the time obtained by the addition Is set as the time of the next detection timing (step S58), and the process related to current detection is finished. When it is determined that the next current value detection is the second re-detection (step S57: NO), the control unit 11a subtracts the off time from the PWM control to the reference timing, and the time obtained by the subtraction is calculated the next time. The detection timing time is set (step S59), and the process related to current detection is completed.

  When it determines with a duty ratio being 50% or less by step S56 (step S56: NO), the control part 11a determines whether a duty ratio is over 40% (step S60). When it is determined that the duty ratio exceeds 40% (step S60: YES), the control unit 11a determines whether or not the next current value detection is the first re-detection performed after the current value detection failure. Determination is made (step S61). When it is determined that the next current value detection is the first re-detection (step S61: YES), the control unit 11a adds half the PWM control on-time to the reference timing, and the time obtained by the addition Is set as the time of the next detection timing (step S62), and the process related to current detection is finished. When it is determined that the next current value detection is the second re-detection (step S61: NO), the control unit 11a subtracts the PWM control ON time from the reference timing, and calculates the time obtained by the subtraction the next time. The detection timing time is set (step S63), and the process related to current detection is completed.

  When it is determined that the duty ratio is 40% or less (step S60: NO), the control unit 11a determines whether or not the next current value detection is the first redetection performed after the current value detection failure. Determination is made (step S64). When it is determined that the next current value detection is the first re-detection (step S64: YES), the control unit 11a adds the on-time of the PWM control to the reference timing, and the time obtained by the addition is calculated the next time. The detection timing time is set (step S65), and the process ends.

  When it is determined that the next current value detection is the second re-detection (step S64: NO), the control unit 11a subtracts and subtracts a time twice as long as the PWM control on-time from the reference timing. The time is set as the time of the next detection timing (step S66), and the process ends.

Hereinafter, a method of re-detecting the current value when the duty ratio is 40 to 60% will be described.
FIG. 12 is a table showing a method of changing the current detection timing according to the modification, and FIGS. 13 and 14 are timing charts showing a method of changing the current detection timing when the duty ratio is more than 40% and 50% or less. is there.

  As shown in FIG. 13, in the case where the duty ratio is more than 40% and 50% or less, when the current value detection timing precedes the PWM control ON time and the current value detection fails, By advancing the next detection timing by half of the PWM control ON time, the current value detection timing can be matched with the PWM control ON time. In this case, the current value can be detected only by trying one redetection. In particular, in the modification, the current value detection timing can be adjusted to the center of the PWM control on-time instead of both ends by advancing by half the PWM control on-time.

  However, as shown in FIG. 14, when the duty ratio is more than 40% and 50% or less, the current value detection timing is delayed from the on-time of the PWM control and the current value detection fails. Even if the next detection timing of the value is advanced by half the PWM control ON time, the current value detection timing cannot be matched with the PWM control ON time. In this case, the current value detection timing can be matched with the PWM control on-time by delaying the subsequent current detection timing by the PWM control on-time. In this case, the current value can be detected only by trying the re-detection twice. Also in this case, the detection timing of the current value can be adjusted not at both ends of the on-time of the PWM control but at the center.

  The above-described procedure is an example, and the next detection timing is delayed by half of the PWM control on-time, and the subsequent detection timing is delayed by half of the PWM control off-time. Also good. In this case as well, the detection timing of the current value can be matched with the on-time of the PWM control only by trying the re-detection twice at the maximum.

  In addition, the example in which the process of moving back and forth by half the PWM control ON time is performed when the duty ratio is 40% to 60% has been described, but the range of the duty ratio is an example, and the duty ratio is 50%. Such processing may be executed in the range before and after.

  In the modified example, even when the detection of the current value fails when the duty ratio is around 50%, the detection timing of the current value can be adjusted to the on-time of the PWM control by re-detection twice at the maximum. .

  Note that although the in-vehicle power supply control device has been described, the present invention can be applied to other electric devices that require power supply. Moreover, although the example which calculates the temperature of a load and an electric wire and detects an electric current value in order to protect was demonstrated, the detection use of an electric current value is an example, and it is necessary to detect the electric current value supplied intermittently to a load The present invention may be used for other applications. For example, the present invention may be used to control the amount of power supply based on the current value supplied to the load.

  In the present embodiment, the temperature of the electric wire is calculated and the relay is opened / closed based on the temperature. However, as an open / close reference of the relay, other elements connected to the electric wire, for example, the load itself, the relay The temperature may be calculated and the relay may be opened and closed based on the temperature. The load and relay temperature calculation method is the same as that of the electric wire, and the load and relay temperature can be calculated by the above (1) to (4) by changing the resistance value, thermal resistance, and heat capacity. Further, as a relay opening / closing reference, a virtually assumed temperature of the thermal fuse may be calculated, and when the temperature reaches a temperature at which the virtual thermal fuse is blown, the relay may be opened.

  In addition, it should be considered that the embodiment disclosed this time is illustrative in all points and not 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.

1 Power supply control device 2 Body ECU
3 Power supply 4 Communication line 5 Vehicle 6 Electric wire 7 Feed switch 11 Microcomputer 11a Control unit (determination unit, change unit)
11b ROM
11c 1st memory | storage part 11d Timer 11e CAN communication I / F
11f I / F part 12 Temperature detection part 13 IPD
13a Current detector 13b Relay (cutoff switch)
13c timer 13d PWM control unit 21 control unit 22 ROM
23 Second storage unit 24 CAN communication I / F
25 Clock part 26 I / F part 51 Load

Claims (9)

In a current detection device that repeatedly detects a current value intermittently supplied to a load,
A determination unit that determines whether or not the detected current value is less than a predetermined value;
And a change unit that changes a detection timing of the current value when it is determined that the current value is less than a predetermined value. The power supply to the load is PWM controlled, and the current value is detected at a cycle that is an integral multiple of the PWM control cycle.
The changing unit is
A first timing changing section that changes the detection timing of the current value by an ON time of PWM control;
The current detection device according to claim 1, further comprising: a second timing changing unit that changes the detection timing of the current value around the OFF time of the PWM control. A storage unit for storing a duty ratio of PWM control;
When the duty ratio of PWM control is smaller than the predetermined duty ratio range, the first timing changing unit changes the detection timing of the current value, and when the duty ratio of PWM control is larger than the predetermined duty ratio range, the second timing change The current detection device according to claim 2, wherein the unit changes the detection timing of the current value. The current detection device according to claim 3, wherein when the duty ratio of PWM control is within the predetermined duty ratio range, the second timing changing unit changes the detection timing of the current value. The changing unit is
When the duty ratio of the PWM control is within the predetermined duty ratio range, the current value detection timing is moved back and forth by half the PWM control on-time, or by the time half of the PWM control off-time. The current detection device according to claim 3, further comprising a timing changing unit. The first timing changing unit includes:
When it is determined that the current value detected after the current value detection timing is advanced (or delayed) by the PWM control on-time is less than a predetermined value, the current value detection timing is set to 2 of the PWM control on-time. The current detection device according to any one of claims 2 to 5, wherein the current detection device is delayed (or advanced) by a double time. The current detection device according to any one of claims 1 to 6,
And a PWM control unit that performs PWM control of power supply to the load. The power supply control device according to claim 7, further comprising: a timing instruction unit that instructs the PWM control unit to start the PWM control on-time so that the current detection timing becomes the PWM control on-time. Based on the detected current value, a calculation unit that calculates the temperature of the load or the electric wire connected to the load;
A temperature determination unit that determines whether the temperature calculated by the calculation unit is equal to or higher than a predetermined temperature;
The power supply control device according to claim 7, further comprising: a cut-off switch configured to cut off power supply to the load when the temperature determination unit determines that the temperature is equal to or higher than a predetermined temperature.

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