JP2012016094A - Feeding controller and feeding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feeding controller and a feeding control method for appropriately interrupting feeding from a DC power supply to a load based on a plurality of determinations on a switch in order to prevent linked malfunctions, firing or the like of the switch.SOLUTION: A control portion 10 measures voltages of load-side terminals of FET 11 and 12 in a period when only the FET 11 between the FET (switch) 11 and 12 is turned off, a period when only the FET 12 is turned off, and in a period when the FET 11 and 12 are simultaneously turned off. The control portion then determines whether any of the FET 11 and 12 has a malfunction based on the measured voltages. The control portion 10 also determines whether a temperature around the FET 11 and 12 exceeds a prescribed temperature or not. The control portion 10 interrupts feeding to a load group 4 when any of the FETs is determined to have a malfunction based on the measured voltages and the temperature around the FET 11 and 12 is determined to exceed the prescribed temperature.

Description

  The present invention relates to a power supply control device and a power supply control method that are preferably used in a vehicle and control power supply to a load by turning on / off a switch connected between a DC power supply and the load.

  The vehicle is equipped with a plurality of loads such as a car navigation device, an audio device, an air conditioner, a door lock, a power window, and various control devices.

  The plurality of loads are connected to a DC power source through a common switch, and power supply from the DC power source to the plurality of loads is controlled by turning on / off the switch.

  In recent years, the number of loads mounted on vehicles has increased, and along with this, the amount of current that switches on / off has increased, making it difficult to turn on / off current with a single switch, A plurality of switches tend to be provided in parallel. As a result, the amount of current flowing through one switch is distributed.

  However, in a power supply control device in which a plurality of switches are provided in parallel and controls power supply to a plurality of loads, if one switch fails and other switches operate normally, power supply to the load is stopped. Therefore, a failure cannot be determined by monitoring the output from the load.

  If you continue to use the power supply control device while one of the switches is broken, a larger current flows through the other switches than usual, and the amount of heat generated by the other switches increases, possibly resulting in failure or fire. Occurs. Therefore, when a switch fails, it is necessary to detect the failed switch and cut off the power supply to the load according to the detection result.

  Patent Document 1 discloses an apparatus that detects a faulty element from a plurality of elements connected in parallel between a power source and a device to which the power source supplies power, and controls power feeding according to the detection result. Has been. In the apparatus described in Patent Document 1, an element failure is determined by measuring the temperature of an element and detecting a temperature rise of another element caused by the failure of one element.

JP 2009-189161 A

  However, as in the device disclosed in Patent Document 1, in the power supply control device that determines the failure of the switch based on the temperature of the switch, if the switch temporarily becomes hot due to the environmental temperature, The problem of misjudging that it is doing. When power supply from the DC power supply to the load is cut off based on an incorrect determination, there is a risk of forcing the driver or passenger of the vehicle to perform unnecessary work such as repair or replacement of the power supply control device, and warned of failure In such a case, there is a risk of anxiety to the driver or passenger of the vehicle.

  The present invention has been made in view of such circumstances, and an object of the present invention is to appropriately cut off power supply from a DC power source to a load based on a plurality of determinations related to the switch. An object of the present invention is to provide a power supply control device and a power supply control method capable of preventing a serious failure or ignition.

  The power supply control device according to the present invention is a power supply control device that is interposed between a DC power supply and a load and controls power supply to the load, and a plurality of switches connected in parallel between the DC power supply and the load, Control means for controlling on / off of a plurality of switches, measuring means for measuring voltages at the load-side terminals of the plurality of switches, and turning on only one switch among the plurality of switches by the control means. And when the plurality of switches are simultaneously turned off, the voltage is measured by the measuring unit, and based on the measured voltage, whether or not there is a faulty switch in the plurality of switches. Voltage determination means for determining whether the temperature is around the plurality of switches, and whether the temperature detected by the temperature detection means exceeds a predetermined temperature. And when the voltage determining means determines that there is a malfunctioning switch and the temperature determining means determines that the temperature exceeds the predetermined temperature, the control means The power supply to the load is configured to be cut off.

  In the power supply control device according to the present invention, when the control means determines that the temperature determination means exceeds the predetermined temperature, the voltage determination means turns on / off the plurality of switches in order to make a determination. It is comprised so that it may do.

  The power supply control device according to the present invention is configured such that, when the temperature detection unit determines that there is a switch in which the voltage determination unit is out of order, the temperature determination unit detects the temperature in order to make a determination. It is characterized by being.

  A power supply control device according to the present invention includes a fuse connected between a positive terminal (or negative terminal) of the DC power supply and the plurality of switches, a plurality of switch-side terminals of the fuse, and a negative electrode of the DC power supply. And a control switch connected directly or indirectly between terminals (or positive terminals) and controlled to be turned on / off by the control means.

  The power supply control device according to the present invention is characterized in that a period during which the control unit turns off the switch is shorter than an allowable instantaneous interruption time of the load in order for the voltage determination unit to make a determination.

  The power supply control device according to the present invention is characterized in that the switch is an FET.

  The power supply control method according to the present invention is a power supply control method for controlling on / off of a plurality of switches connected in parallel between a DC power source and a load, wherein only one of the plurality of switches is turned on. A first voltage measurement step for measuring voltages at the load-side terminals of the plurality of switches during a period in which only the switches are on, and a period during which the plurality of switches are simultaneously turned off and are simultaneously off. Based on the voltage measured in the second voltage measuring step for measuring the voltage at the load-side terminal of the plurality of switches, and the first and second voltage measuring steps, a switch in which the plurality of switches have failed A voltage determination step for determining whether there is a temperature, a temperature detection step for detecting temperatures around the plurality of switches, and a temperature detected in the temperature detection step. When it is determined that there is a malfunctioning switch in the temperature determination step that determines whether or not the temperature exceeds a predetermined temperature and the voltage determination step, and the temperature determination step determines that the temperature exceeds the predetermined temperature And an interruption step of interrupting power supply to the load.

In the power supply control device and the power supply control method according to the present invention, voltage determination and temperature determination are performed. In the voltage determination, first, one switch is turned on, and the voltages at the terminals on the load side of the plurality of switches are measured during the period when the other switches are turned off. Hereinafter, a case will be described in which a plurality of switches are connected to the positive terminal of the DC power source, and the negative terminal of the DC power source and one terminal of the load are grounded. When the measured voltage is the voltage of the positive terminal in the DC power supply, it is determined that one switch is operating normally. When the measured voltage is the potential of the body ground, it is determined that one of the switches is off and has failed.
The plurality of switches described above are repeatedly turned on / off in place of the switch to be turned on, and it is sequentially determined whether each of the plurality of switches is operating normally or has a failure while being turned off.

  In addition, the plurality of switches are simultaneously turned off, and the voltage at the above-described location is measured during the period when the switches are turned off. If the measured voltage is the voltage of the positive terminal of the DC power supply, it is determined that one of the multiple switches is on and failed, and if the measured voltage is the body ground potential, the multiple switches are normal. Is determined to be operating.

  In the temperature determination, it is determined whether the temperature around the plurality of switches exceeds a predetermined temperature. When it is determined that there is a malfunctioning switch in the voltage determination and it is determined in the temperature determination that the predetermined temperature is exceeded, the power supply to the load is cut off.

  When it is determined that there is a malfunctioning switch in the voltage determination, and the temperature determination determines that the temperature exceeds the predetermined temperature, the power supply to the load is cut off. Chain failures or fires are prevented. For example, even when the temperature around the plurality of switches temporarily increased due to the environmental temperature exceeds a predetermined temperature, it is determined by the voltage determination that there is no malfunctioning switch, and power supply is not cut off.

  In the power supply control device according to the present invention, when the temperature determination unit determines that a temperature exceeding a predetermined temperature is detected around the plurality of switches, the control unit turns on / off the plurality of switches, and the voltage determination unit judge. The on / off of the switch by the control means changes the voltage or current applied to the load and makes the power supply to the load unstable. On the other hand, the temperature detection by the temperature detection means is irrelevant to the power supply to the load. For this reason, the temperature detection means can detect temperature more frequently than on / off of the switch by the control means.

  Accordingly, the temperature determination unit repeats the determination at short intervals, and when it is determined that the temperature around the plurality of switches has exceeded the predetermined temperature, the voltage determination unit determines whether there is a malfunctioning switch. Compared with a case where determination is made only by the determination means, a state in which there is a possibility of chain failure or ignition of the switch can be quickly found without destabilizing the power supply to the load.

  Further, only when the temperature determination means determines that the temperature around the plurality of switches exceeds a predetermined temperature, the control means turns on / off the switch for the voltage determination means to determine, so only the voltage determination means Compared with the case of determining, the number of times the switch is switched on / off is reduced.

  In the power supply control device according to the present invention, when the voltage determination unit determines that there is a malfunctioning switch, the temperature detection unit detects temperatures around the plurality of switches, and the temperature determination unit determines. Even if one switch fails, for example, when it is off, if the number of driving loads is small and the current that turns the switch on or off is small, the temperature exceeding the predetermined temperature is not detected around multiple switches. . When the temperature exceeding the predetermined temperature is not detected, there is no possibility of failure or ignition of other switches, so that power supply to the load through the other switches can be continued.

  Therefore, even if there is a switch that has failed in the voltage determination after the voltage determination means determines, even if there is a switch that fails in the voltage determination, the power supply to the load is not cut off if the temperature around the plurality of switches is low. The power is supplied to the load for a long time.

  In the power supply control device according to the present invention, the fuse connected between the positive terminal (or the negative terminal) of the DC power source and the plurality of switches, the terminals on the plurality of switch sides of the fuse, and the negative terminal (or the DC power source) (or And a control switch connected directly or indirectly between the positive terminal). When the voltage determining means determines that there is a malfunctioning switch and the temperature determining means determines that the temperature exceeds the predetermined temperature, the control means turns on the control switch and supplies a current equal to or higher than the rated current to the fuse. To blow the fuse. For this reason, the power supply from the DC power supply to the load is surely cut off.

  In the power supply control device according to the present invention, since the period during which the control unit turns off the switch when the voltage determination unit determines is shorter than the allowable instantaneous interruption time of the load, the switch can be performed without hindering the operation of the load. Is determined to be faulty.

  In the power supply control device according to the present invention, an FET is used for the switch.

  According to the present invention, it is possible to appropriately cut off the power supply from the DC power supply to the load by combining the determination of the voltage at the load-side terminal of the plurality of switches and the determination of the temperature detected around the plurality of switches. It is possible to prevent a cascade failure or ignition of the switch.

It is a block diagram which shows the structure of embodiment of the electric power feeding control apparatus and electric power feeding control method which concern on this invention. It is a timing chart of the gate voltage controlled by a switch control circuit based on control from a control part. It is explanatory drawing which shows the example of the content of the reference | standard of the failure determination by a control part. It is another timing chart of the gate voltage controlled by a switch control circuit based on control from a control part. It is a flowchart which shows the operation | movement in embodiment of the electric power feeding control apparatus which concerns on this invention. It is a flowchart which shows the operation | movement in embodiment of the electric power feeding control apparatus which concerns on this invention.

(Embodiment 1)
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a block diagram showing a configuration of a power supply control device and a power supply control method according to Embodiment 1 of the present invention. The power supply control device 1 is mounted on a vehicle, and one terminal of the power supply control device 1 is connected between the other terminal of the fuse 3 connected to the positive terminal of the battery 2 and the load group 4 subject to power supply control. The negative terminal of the battery 2 is body grounded. In the claims, the battery 2 corresponds to a DC power source, and the load group 4 corresponds to a load.
The load group 4 is one or a plurality of ECUs (Electronic Controller Units) fed by the battery 2. One terminal of each ECU is connected to the power line in a bus shape, and the other terminal is body-grounded. Power supply is controlled by the power supply control device 1 as a whole.

  The power supply control device 1 includes a control unit 10 having a CPU (Central Processing Unit), an FET 11, an FET 12 connected in parallel to the FET 11, a switch control circuit 13, and a voltage measurement circuit 14. In the claims, the control unit 10 corresponds to a control unit, a voltage determination unit, and a temperature determination unit, the FETs 11 and 12 each correspond to a switch, and the voltage measurement circuit 14 corresponds to a measurement unit.

  The sources of the FETs 11 and 12 are connected to the battery 2 through the fuse 3, and the drains are connected to the load group 4. The switch control circuit 13 controls the gate voltage of each of the FET 11 and the FET 12. The voltage measurement circuit 14 measures the output voltage of the FET 11 and / or the FET 12.

  The power supply control device 1 further includes a thermistor 15 arranged around the FETs 11 and 12, a temperature detection circuit 16 connected to both ends of the thermistor 15, and one terminal connected to the battery 2 through the fuse 3. A relay contact 17 whose other terminal is grounded and a relay control circuit 18 are provided. In the claims, the temperature detection circuit 16 corresponds to a temperature detection means, and the relay contact 17 corresponds to a control switch.

  The temperature detection circuit 16 detects the temperature from the electrical resistance of the thermistor 15. The relay control circuit 18 controls on / off of the relay contact 17. When the relay contact 17 is turned on, the terminals of the fuses 3 on the FETs 11 and 12 side and the body ground are short-circuited, a current exceeding the rated current flows from the battery 2 to the fuse 3, and the fuse 3 is blown.

  The control unit 10 controls on / off of the FETs 11 and 12 and the relay contact 17 by reading and executing a control program stored in the built-in ROM using a CPU. The control unit 10 is not limited to a configuration using a CPU alone, and may be a microcomputer.

  An ACC signal and an IG ON / IG OFF signal from an accessory switch and an ignition switch (not shown) are input to the control unit 10. Further, a signal from a battery sensor that measures the remaining amount of the battery 2 is input to the control unit 10. The control unit 10 executes a switch control process based on signals from these switches and sensors, and outputs a control signal for controlling on / off of the FETs 11 and 12 to the switch control circuit 13.

Basically, the control unit 10 turns on both the FETs 11 and 12 when power supply to the load group 4 is started, and turns off both the FETs 11 and 12 when power supply to the load group 4 is stopped.
Further, the control unit 10 receives a signal from the voltage measurement circuit 14 and executes a failure determination process described later based on the voltage measurement result indicated by the signal. The control unit 10 receives a signal from the temperature detection circuit 16, and determines whether or not the temperature exceeds a predetermined temperature based on the temperature detection result indicated by the signal.

Further, the control unit 10 controls on / off of the relay contact 17 through the relay control circuit 18 based on the result of the failure determination process and the temperature detection result.
The control unit 10 is further connected to the communication line 5, and is connected to the CAN (Control Area Network) or LIN (Local Interconnect Network) through the communication line 5. The control unit 10 outputs a warning signal related to the failure information of the FETs 11 and 12 to a display or the like provided in the vehicle through CAN or LIN.

The switch control circuit 13 controls the gate voltages of the FETs 11 and 12 based on a control signal from the control unit 10.
The voltage measurement circuit 14 measures the drain voltages of the FETs 11 and 12 and notifies the control unit 10 of them.
The temperature detection circuit 16 detects the temperature around the FETs 11 and 12 by the thermistor 15 and notifies the control unit 10 of the temperature.
The relay control circuit 18 controls on / off of the relay contact 17 based on a control signal from the control unit 10.

Details of the failure determination process using the switch control circuit 13 and the voltage measurement circuit 14 executed by the control unit 10 will be described below.
FIG. 2 is a timing chart of the gate voltage controlled by the switch control circuit 13 based on the control from the control unit 10. 2 shows the time axis on the horizontal axis and the H (High) / L (Low) gate voltage on the vertical axis, and FIGS. 2A and 2B show timing charts of the gate voltages of the FETs 11 and 12, respectively. .
When the gate voltage of the FET 11 (or FET 12) is H or L, the FET 11 (or FET 12) is turned on or off.

When the control unit 10 determines whether or not there is a faulty FET in the FETs 11 and 12, the gate voltage of the FETs 11 and 12 is lowered to L for a very short time, and the FETs 11 and 12 are turned off and off respectively. Whether the voltage measured by the voltage measurement circuit 14 is H or L is determined.
Here, the measured voltage being H indicates that the measured voltage is the voltage of the positive terminal of the battery 2, and the measured voltage being L indicates that the measured voltage is body ground. It shows that the potential is.

  As illustrated in FIG. 2, the control unit 10 repeats the switch control circuit 13 to set the gate voltages of the FETs 11 and 12 to L only during the period ta twice. At this time, the control unit 10 performs control so that the second period ta in which the gate voltage of the FET 11 is L is equal to the first period ta in which the gate voltage of the FET 12 is L. Thus, a period is provided in which only one of the FETs 11 and 12 is on (or off) and both are off.

  Note that the period in which the gate voltage of the FET 11 is L and the period in which the gate voltage of the FET 12 is L are not necessarily the same period ta. However, the period ta in which the gate voltage of the FET 11 or FET 12 is L is shorter than the allowable instantaneous interruption time of the load group 4. In the first embodiment, the period ta is within 2 milliseconds. The load group 4 must be configured to allow momentary interruption using a reverse connection diode or the like.

  The control unit 10 sets the time point t1 during the period ta when only the gate voltage of the FET 11 is L, the time point t2 during the period ta when the gate voltages of both the FETs 11 and 12 are L, and only the gate voltage of the FET 12 is L. The voltage is measured by the voltage measuring circuit 14 at time t3 in the period ta. The correspondence between the result obtained by the measurement and the determination result of the control unit 10 is as follows.

FIG. 3 is an explanatory diagram illustrating an example of the content of a criterion for failure determination by the control unit 10.
As shown in FIG. 3, when the voltage measured by the voltage measuring circuit 14 is H at the time t1 during the period when only the gate voltage of the FET 11 is L, the FET 12 is operating normally. Determined. This is because the FET 11 is in the off state at the time t1, but the output voltage is maintained at H if the FET 12 is operating normally because the FET 12 is in the on state. On the other hand, when the voltage measured by the voltage measurement circuit 14 is L at the time t1, it is determined that the FET 12 is in a failure state while being in the off state.

  When the voltage measured by the voltage measurement circuit 14 is H at the time t2 during the period when the gate voltages of both the FETs 11 and 12 are L, either of the FETs 11 and 12 fails while being turned on. It is determined that This is because both the FETs 11 and 12 should be in the OFF state at the time t2, and therefore the output voltage becomes L if the FETs 11 and 12 are operating normally. On the other hand, when the voltage measured by the voltage measurement circuit 14 is L at time t2, it is determined that the FETs 11 and 12 are operating normally.

  If the voltage measured by the voltage measurement circuit 14 is H at time t3 during the period when only the gate voltage of the FET 12 is L, it is determined that the FET 11 is operating normally. This is because the FET 12 is off at the time t3, but the FET 11 is on, so that the output voltage is maintained at H if the FET 11 is operating normally. On the other hand, when the voltage measured by the voltage measurement circuit 14 is L at the time point t3, it is determined that the FET 11 is in a failure state while being turned off.

  As described above, the failure of each of the FETs 11 and 12 can be determined by configuring the power supply control device 1. In addition, since the FETs 11 and 12 are connected in parallel and the off-period of the FETs 11 and 12 is shorter than the allowable instantaneous interruption time of the load group 4, the load group even during power supply from the power supply control device 1 to the load group 4 The failure can be determined without hindering the operation of No. 4.

  Note that the timing chart of the gate voltage controlled by the switch control circuit 13 is not limited to the timing chart shown in FIG. FIG. 4 is another timing chart of the gate voltage controlled by the switch control circuit 13 based on the control from the control unit 10. 4 shows the time axis on the horizontal axis and H (High) / L (Low) of the gate voltage on the vertical axis, as in FIG. 2, and FIGS. 4A and 4B show the gate voltages of the FETs 11 and 12, respectively. A timing chart is shown.

  The controller 10 causes the switch control circuit 13 to set the gate voltage of the FET 11 to L for the period tb, and similarly to setting the gate voltage of the FET 12 to L for the period tb so as to overlap during the period tb. The timing chart of the gate voltage controlled by the switch control circuit 13 may be the timing chart shown in FIG.

  Here, the period for turning off the gate voltages of the FET 11 and the FET 12 may not be the same. The period tb during which the gate voltages of the FETs 11 and 12 are turned off is shorter than the allowable instantaneous interruption time of the load group 4.

  Further, t1 is a time point during a period in which only the gate voltage of the FET 11 is set to L, t2 is a time point during an overlapping period of the period tb in which the gate voltages of both the FETs 11 and 12 are set to L, and t3 is a time point of the FET 12. This is a point in time during which only the gate voltage is L.

  Furthermore, the switch provided between the battery 2 and the load group 4 is not limited to the FET. The switch may be a relay contact, for example. Further, the number of switches provided between the battery 2 and the load group 4 is not limited to two. Three or more switches may be provided.

  A feature of the present invention is a control method of the control unit 10 based on the result of the above-described failure determination processing (hereinafter simply referred to as failure determination processing) and the temperature detection result around the FETs 11 and 12 detected by the temperature detection unit 16. It is in. Details of this control method will be described below.

FIG. 5 is a flowchart showing the operation of the power supply control device 1 according to the first embodiment of the present invention.
First, the control unit 10 receives a signal from the temperature detection circuit 16 every predetermined period, for example, every 100 milliseconds, and determines whether or not the temperature detection circuit 16 has detected a temperature exceeding the predetermined temperature T1 (S1).
When it is determined that the temperature detection circuit 16 has not detected a temperature exceeding the predetermined temperature T1 (S1: NO), the control unit 10 returns to step S1.

When it is determined that the temperature detection circuit 16 has detected a temperature exceeding the predetermined temperature T1 (S1: YES), the control unit 10 determines that any of the FETs 11 and 12 may be defective and determines the failure. Processing is executed (S2).
When one of the FETs 11 and 12 fails, the current flowing through the FET 11 (or FET 12) increases, and the amount of heat generated by the FET 11 (or FET 12) increases. The controller 10 can quickly find a failure by monitoring the temperature around the FETs 11 and 12 every predetermined period. The predetermined temperature T1 is set higher than the temperature when both the FETs 11 and 12 are operating normally, and lower than the temperature detected when one of the FETs 11 and 12 fails.

After executing the failure determination process (after step S2), the control unit 10 determines whether there is a failed FET in the FETs 11 and 12 (S3).
The controller 10 turns the FETs 11 and 12 on / off only when the temperature detection circuit 16 detects a temperature exceeding a predetermined temperature around the FETs 11 and 12. Therefore, the number of on / off switching of the FETs 11 and 12 can be reduced as compared with the case where it is determined whether or not there is a defective FET only by the failure determination processing. For this reason, regarding the voltage applied to the load group 4, the number of changes due to on / off switching of the FETs 11 and 12 is suppressed, and power can be stably supplied to the load group 4.

  When it is determined that there is a failed FET in the FETs 11 and 12 (S3: YES), the control unit 10 outputs a control signal to the relay control circuit 18 and turns on the relay contact 17 (S4).

  As a result, the fuse 3 and the body ground are short-circuited, a current exceeding the rated current is passed through the fuse 3, and the fuse 3 is blown. As a result, power supply from the battery 2 to the load group 4 is cut off. For this reason, it is possible to reliably prevent a chain failure or ignition of the FET 11 (or FET 12) caused by an increase in the amount of heat generated with an increase in the current flowing through the FET 11 (or FET 12).

  Note that the method of cutting off the power supply from the battery 2 to the load group 4 is not limited to the method of fusing the fuse 3 with the current supplied by the battery 2. For example, the power supply to the load group 4 may be interrupted by setting the gate voltage applied to the FETs 11 and 12 by the control unit 10 to L.

After turning on the relay contact 17 (after step S4), the control unit 10 outputs a warning signal related to the failure information to the display provided in the vehicle through the communication line 5 connected to CAN or LIN. Fault information is output to (S5).
Note that the method for outputting the failure information is not limited to the method for outputting to the display. For example, the failure information may be notified to the driver of the vehicle or the occupant by voice or buzzer.
After outputting the failure information (after step S5), the control unit 10 ends the control.

  When the control unit 10 determines that there is no failed FET in the FETs 11 and 12 (S3: NO), whether or not the period during which the temperature detection circuit 16 detects the temperature exceeding the predetermined temperature T1 exceeds the predetermined period ts. Is determined (S6). The detection period is measured by a timer or the like built in the control unit 10.

  When the control unit 10 determines that the period during which the temperature detection circuit 16 detects the temperature exceeding the predetermined temperature T1 does not exceed the predetermined period ts (S6: NO), the temperature exceeding the predetermined temperature T1 is detected in step S1. It is assumed that the cause is an external factor such as the environmental temperature, not the failure of the FETs 11 and 12, and the process returns to step S1.

  Accordingly, when a temperature exceeding the predetermined temperature T1 is detected around the FETs 11 and 12, and there is a failed FET by the failure determination process, the power supply is cut off, and due to a temporary temperature increase due to an external factor such as an environmental temperature. Since power feeding is not interrupted, power feeding to the load group 4 can be appropriately interrupted.

  When it is determined that the period during which the temperature detection circuit 16 detects the temperature exceeding the predetermined temperature T1 exceeds the predetermined period ts (S6: YES), the control unit 10 sets the gate voltages of the FETs 11 and 12 to L, 12 is turned off (S7). This is because there is a possibility that a failure that could not be determined by the failure determination process has occurred in either of the FETs 11 and 12.

After turning off both FETs 11 and 12 (after step S7), the controller 10 outputs failure information in the same manner as in step S5 (S8).
After outputting the failure information (after step S8), the control unit 10 again determines whether or not the period during which the temperature detection circuit 16 detects the temperature exceeding the predetermined temperature T1 exceeds the predetermined period ts (S9). ). As described above, the detection period is measured by a timer or the like built in the control unit 10.

  When it is determined that the period during which the temperature detection circuit 16 detects the temperature exceeding the predetermined temperature T1 does not exceed the predetermined period ts (S9: NO), the control unit 10 determines that the FET 11, The control is terminated because there is no longer a risk of twelve failures or firing.

When it is determined that the period during which the temperature detection circuit 16 detects the temperature exceeding the predetermined temperature T1 exceeds the predetermined period ts (S9: YES), the control unit 10 executes Step S4. The controller 10 turns on the relay contact 17 and blows the fuse 3, thereby reliably cutting off the power supply from the battery 2 to the load group 4. As a result, the possibility of failure or ignition of the FETs 11 and 12 due to excessive supply of current to the FETs 11 and 12 can be reliably eliminated.
After executing step S4, the control unit 10 outputs failure information in step S5 and ends the control.

  In addition, the control part 10 can determine a failure similarly by performing the failure determination process of step S2 for every predetermined period, without determining the temperature in step S1. However, it is not desirable to execute the failure determination process every short predetermined time such as 100 milliseconds.

One reason is that when the failure determination process is executed every short time such as 100 milliseconds, the voltage or current applied to the load group 4 frequently changes, and thus the power supply to the load group 4 is not stable.
On the other hand, the temperature detection around the FETs 11 and 12 by the temperature detection circuit 16 is irrelevant to the power supply to the load group 4.

  Further, when executing the failure determination process, the control unit 10 turns off the FET 11 or (and) the FET 12 for a predetermined period, and the load group 4 uses the electric power stored in the instantaneous interruption capacitor in the off period. Must be used. Another reason is that if the failure determination process is executed every short time such as 100 milliseconds, it cannot be stored in the capacitor for instantaneous interruption, and the load group 4 turns off the FET 11 or (and) the FET 12. There is a risk of stopping while you are.

  Therefore, the control unit 10 detects the temperature every short time such as 100 milliseconds, and executes a failure determination process when a temperature exceeding the predetermined temperature T1 is detected. As a result, in a state where the power supply to the load group 4 is stabilized, the FETs 11 and 12 can be chained or ignited without worrying about the stop of the load group 4 while the FET 11 or (and) the FET 12 is turned off. It is possible to quickly find a state that there is a risk of such.

(Embodiment 2)
FIG. 6 is a flowchart showing the operation of the power supply control device 1 according to the second embodiment of the present invention. The configuration of the power supply control device and the power supply control method according to the second embodiment of the present invention is the same as the configuration of the above-described first embodiment (FIGS. 1 to 4), and thus description thereof is omitted.
First, the control part 10 performs a failure determination process every predetermined period, for example, every 5 minutes (S11). Thereafter, the control unit 10 determines whether or not there is a failed FET in the FETs 11 and 12 (S12).

When it is determined that there is no failed FET in the FETs 11 and 12 (S12: NO), the control unit 10 returns to step S11.
When it is determined that there is a failed FET in the FETs 11 and 12 (S12: YES), the control unit 10 determines whether or not the temperature detection circuit 16 has detected a temperature exceeding the predetermined temperature T2 (S13). .

  The predetermined temperature T2 is set higher than the temperature when both the FETs 11 and 12 are operating normally, and lower than the temperature detected when either of the FETs 11 and 12 fails.

  When it is determined that the temperature detection circuit 16 has not detected a temperature exceeding the predetermined temperature T2 (S13: NO), the control unit 10 performs the failure determination process in the same manner as in steps S5 and S9 in the first embodiment. Failure information indicating that a failure has been determined is output (S14).

  Thereafter, since the temperature detected by the temperature detection circuit 16 does not exceed the predetermined temperature T2, the control unit 10 has no fear of failure or ignition in other FETs except the FET determined to be failed by the failure determination. It is determined that the power supply to the load group 4 can be controlled by turning on / off other FETs. And the control part 10 continues the electric power feeding from the battery 2 to the load group 4, and returns to step S11. Thereby, it is possible to supply power to the load group 4 from the battery 2 for a long time.

  For example, even when the FET 11 (or FET 12) is off and fails, the current that turns on or off the FETs 11 and 12 is small due to the small number of loads driving in the load group 4. In this case, there is no fear of failure or ignition of the FET 12 (or the FET 11). Therefore, when the temperature exceeding the predetermined temperature T2 is not detected around the FETs 11 and 12, the power supply to the load group 4 is controlled by turning on / off the FET 12 (or the FET 11), and the power supply from the battery 2 to the load group 4 is controlled. Can continue.

  When it is determined that the temperature detection circuit 16 has detected a temperature exceeding the predetermined temperature T2 (S13: YES), the control unit 10 outputs a control signal to the relay control circuit 18 and turns on the relay contact 17 (S15). As a result, the fuse 3 is short-circuited, and a current exceeding the rated current is passed through the fuse 3 to blow the fuse 3. As a result, power supply from the battery 2 to the load group 4 is cut off. For this reason, it is possible to reliably prevent failure or ignition of the FET 11 (or FET 12) caused by an increase in the amount of heat generated with an increase in the current flowing through the FET 11 (or FET 12).

  Accordingly, when there is an FET that has failed due to the failure determination process and a temperature exceeding the predetermined temperature T2 is detected around the FETs 11 and 12, the power supply is cut off, and the power supply to the failure determination process load group 4 is appropriately cut off. be able to. In other words, even when there is a failed FET due to the failure determination process, the power supply is not interrupted when the temperature around the FETs 11 and 12 does not exceed the predetermined temperature T2.

  Note that the method of cutting off the power supply from the battery 2 to the load group 4 is not limited to the method of fusing the fuse 3 with the current supplied by the battery 2. For example, the power supply to the load group 4 may be interrupted by setting the gate voltage applied to the FETs 11 and 12 by the control unit 10 to L.

After turning on relay contact 17 (after step S15), control unit 10 outputs failure information in the same manner as in steps S5 and S9 in the first embodiment and step S14 in the second embodiment (S16). .
Thereafter, the control unit 10 ends the control.

  Further, the thermistor 15 provided for detecting the temperature around the FETs 11 and 12 is not limited to one. The temperature around the FETs 11 and 12 may be detected by a plurality of thermistors 15, 15,.

  In the first embodiment or the second embodiment, the number of FETs is not limited to two. The present invention can be applied even to a power supply control device having three or more FETs.

  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 description 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 control apparatus 10 Control part (control means, voltage determination means, temperature determination means)
11,12 FET (switch)
14 Voltage measurement circuit (measuring means)
16 Temperature detection circuit (temperature detection means)
17 Relay contact (control switch)
2 Battery (DC power supply)
3 Fuse 4 Load group (load)

Claims (7)

In a power supply control device that is interposed between a DC power supply and a load and controls power supply to the load,
A plurality of switches connected in parallel between the DC power source and the load;
Control means for controlling on / off of the plurality of switches, respectively;
Measuring means for measuring voltages at the load-side terminals of the plurality of switches;
When only one of the plurality of switches is turned on by the control means, and when the plurality of switches are simultaneously turned off, the voltage is measured by the measurement means, and the measured voltage is obtained. Based on voltage determination means for determining whether or not there is a malfunctioning switch among the plurality of switches;
Temperature detecting means for detecting temperatures around the plurality of switches;
Temperature determining means for determining whether or not the temperature detected by the temperature detecting means exceeds a predetermined temperature, and
When the voltage determination unit determines that there is a malfunctioning switch and the temperature determination unit determines that the predetermined temperature is exceeded, the control unit cuts off the power supply to the load. It is comprised in the electric power feeding control apparatus characterized by the above-mentioned. The control unit is configured to turn on / off the plurality of switches in order for the voltage determination unit to determine when the temperature determination unit determines that the predetermined temperature is exceeded. The power supply control device according to claim 1, wherein the power supply control device is a power supply control device. The temperature detection unit is configured to detect a temperature in order for the temperature determination unit to determine when the voltage determination unit determines that there is a malfunctioning switch. Item 2. The power supply control device according to Item 1. A fuse connected between a positive terminal (or a negative terminal) of the DC power source and the plurality of switches;
A control switch connected directly or indirectly between the plurality of switch-side terminals of the fuse and the negative terminal (or positive terminal) of the DC power source and controlled to be turned on / off by the control means. The power supply control device according to any one of claims 1 to 3, wherein The period during which the control unit turns off the switch for the voltage determination unit to make a determination is shorter than the allowable instantaneous interruption time of the load. The power supply control device according to one. The power supply control device according to any one of claims 1 to 5, wherein the switch is an FET. In a power supply control method for controlling on / off of a plurality of switches connected in parallel between a DC power source and a load,
A first voltage measuring step of turning on only one switch of the plurality of switches and measuring a voltage at the load side terminal of the plurality of switches during a period in which only one switch is on;
A second voltage measuring step of simultaneously turning off the plurality of switches and measuring voltages at the load-side terminals of the plurality of switches during a period in which the switches are simultaneously off;
A voltage determination step of determining whether or not there is a malfunctioning switch in the plurality of switches based on the voltages measured in the first and second voltage measurement steps;
A temperature detecting step for detecting temperatures around the plurality of switches;
A temperature determination step for determining whether or not the temperature detected in the temperature detection step exceeds a predetermined temperature;
A disconnecting step of interrupting power supply to the load when it is determined in the voltage determining step that there is a malfunctioning switch and the temperature determining step determines that the temperature exceeds the predetermined temperature. A power supply control method characterized by the above.

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