JP7016658B2 - Switch failure detector - Google Patents

Description

The present invention relates to a switch failure detection device.

As the above-mentioned switch failure detection device, for example, the one described in Patent Document 1 is known. In the power supply device of Patent Document 1 described above, by comparing the source voltage when the FET (switch) is turned off with the threshold value, a short-circuit failure of the FET (that is, the FET is stuck on and cannot be turned off). Failure) is detected. However, the power supply device of Patent Document 1 described above detects a sticking failure only when the FET is off, that is, when both ends of the FET are cut off. Therefore, when the FET is on, that is, when both ends of the FET are conducting, the sticking failure cannot be detected, and the sticking failure that occurred while the FET is on cannot be detected.

Therefore, as a device for detecting a failure without shutting off both ends of the switch, the switch failure detection device of Patent Document 2 has been proposed. The switch failure detection device of Patent Document 2 connects two series circuits in which a resistor and a switch element are connected in series in parallel. The control circuit turns on the two switch elements and turns off only one of the switch elements in turn when detecting a failure. The comparison circuit detects a switch sticking failure based on the voltage across the series circuit at this time.

In the switch failure detection device of Patent Document 2 described above, the sticking failure of the switch is detected based on the difference in the combined resistance of the series circuit at the time of normal operation and the time of failure. Since the difference in combined resistance between normal and faulty is not large, there is a problem that sticking fault cannot be detected accurately.

Japanese Unexamined Patent Publication No. 2016-163051 Japanese Unexamined Patent Publication No. 2007-285769

The present invention has been made in view of the above background, and an object of the present invention is to provide a switch failure detection device capable of detecting a sticking failure while both ends of the switch are conducting while improving accuracy.

The switch failure detection device according to the embodiment of the present invention includes a plurality of switches provided on a plurality of branch paths that branch the current path into a plurality of branches, and a plurality of currents that detect currents flowing in the plurality of branch paths. The detection unit, the switch control unit that controls the switches off in order for each branch path after the plurality of switches are turned on, and the switch control unit that controls the switches off for a certain period of time, and the plurality of switches during the control of the switches by the switch control unit. It is characterized by including a first failure detecting unit for detecting a failure of the switch based on the current flowing through the plurality of branch paths detected by the current detecting unit of the above.

Further, a board on which the plurality of switches are mounted and a wiring pattern or bus bar provided on the board for connecting the plurality of switches to a power source or a load are provided, and the current detection unit is provided. The wiring pattern or the resistance value of the bus bar may be used as the shunt resistance to detect the current flowing in the branch path.

Further, a second failure detection unit that detects a failure of the current detection unit by comparing the currents detected by the plurality of current detection units when the plurality of switches are on may be provided.

As described above, according to the embodiment, a sticking failure can be detected by providing a plurality of branch paths and turning off the switch sequentially for each branch path for a certain period of time. Therefore, a sticking failure sometimes occurs during switch on control. Can be detected. Further, the accuracy can be improved by detecting the failure based on the current.

It is a circuit diagram which shows one Embodiment of the power supply device for a vehicle which incorporates the failure detection device of the switch of this invention. It is explanatory drawing for demonstrating the current which flows when the switch Q3 and Q4 are turned off in a normal state. It is a time chart of on / off of switches Q1 to Q4 and currents I0 to I2 in a normal state. It is explanatory drawing for demonstrating the current which flows when the switch Q3 and Q4 are turned off at the time of abnormality. It is a time chart of on / off of switches Q1 to Q4 and currents I0 to I2 at the time of abnormality. It is a flowchart which shows the processing procedure of μCOM shown in FIG. It is a schematic diagram which shows the failure detection apparatus of a switch in another embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram showing an embodiment of a vehicle power supply device incorporating the switch failure detection device of the present invention. The vehicle power supply device 1 shown in FIG. 1 includes a main battery 11 mounted on the vehicle and a sub-battery 12.

The main battery 11 is composed of an inexpensive battery such as a lead battery, and is connected to a starter ST, an alternator ALT, and a load Lo1. The sub-battery 12 is composed of a high-performance battery such as a lithium ion battery or a nickel hydrogen battery, and is connected to the load Lo2.

The current path between the main battery 11 and the sub-battery 12 is branched into two, and two branch paths L1 and L2 are provided. The vehicle power supply device 1 includes a plurality of switches Q1 to Q4 provided on the two branch paths L1 and L2, a current detection unit 13 for detecting a current flowing through the plurality of branch paths L1 and L2, respectively. It includes a switch control unit, a first failure detection unit, and a microcomputer (hereinafter, μCOM) 14 that functions as a second failure detection unit.

Each of the switches Q1 to Q4 is composed of a field effect transistor. The switches Q1 and Q2 are provided on the branch path L1, the drains and the sources are connected to each other, and the switches Q1 and Q2 are connected to each other in parallel. The switches Q3 and Q4 are provided on the branch path L2, and the drains and sources are connected to each other and are connected in parallel to each other.

Each of the plurality of current detection units 13 includes a shunt resistor 13A and a differential amplifier 13B that amplifies the voltage across the shunt resistor 13A. The shunt resistor 13A is provided on each of the branch paths L1 and L2, respectively. The shunt resistor 13A provided on the branch path L1 is connected in series with the switches Q1 and Q2. The shunt resistor 13A provided on the branch path L2 is connected in series with the switches Q3 and Q4. In the differential amplifier 13B, both ends of the shunt resistor 13A are input, and the voltage across the shunt resistor 13A is amplified and supplied to μCOM 14 as a current value flowing on the branch paths L1 and L2.

The μCOM 14 is a well-known microcomputer that controls the entire vehicle power supply device 1 and is composed of a CPU, a ROM, a RAM, and the like. The μCOM 14 is connected to the gate of the switches Q1 to Q4 and supplies a gate signal to control the on / off of the switches Q1 to Q4.

The μCOM 14 controls the switches Q1 to Q4 on when it is necessary to connect the main battery 11 and the sub-battery 12, for example, when the sub-battery 12 is to be regeneratively charged. The μCOM 14 detects a failure of the switches Q1 to Q4 when the switches Q1 to Q4 are turned on. First, consider the state in which all of the switches Q1 to Q4 are turned on. It is assumed that the shunt resistors 13A of the current detection units 13 provided in the branch paths L1 and L2 have the same resistance value. If all of the switches Q1 to Q4 are on, the currents I1 and I2 flowing in the branch paths L1 and L2 detected by the current detection units 13 are equal. The currents I1 and I2 are 1/2 times the total current I0.

Next, only the switches Q3 and Q4 are turned off for a certain period of time (for example, 2 ms to 10 ms). At this time, if the switches Q1 to Q4 are normal, the current I2 flowing in the branch path L2 becomes 0A as shown in FIGS. 2 and 3. Then, since the current flowing in the branch path L2 flows through the branch path L1, the current I1 flowing in the branch path L1 increases (doubles) and becomes equal to the total current I0. Similarly, when the switches Q1 and Q2 are turned off for a certain period of time, if the switches Q1 and Q2 are turned off normally, the currents I1 and I2 fluctuate as shown in FIG. Since the switches Q1 and Q2 are on while the switches Q3 and Q4 are off, the continuity between the batteries 11 and 12 is maintained. Similarly, while the switches Q1 and Q2 are off, the switches Q3 and Q4 are on, so that the continuity between the batteries 11 and 12 is maintained.

On the other hand, when only the switches Q3 and Q4 are turned off for a certain period of time, for example, if a sticking failure occurs in the switch Q3, a current continues to flow in the branch path L1 through the switch Q3. Therefore, as shown in FIG. 5, the currents I1 and I2 do not change even when the switches Q3 and Q4 are turned off. If the currents I1 and I2 do not fluctuate when the branch paths L1 and L2 are sequentially cut off, the μCOM 14 of the present embodiment detects a failure of the switches Q1 to Q4 provided on the branch paths L1 and L2. As described above, the failure of the switches Q1 to Q4 can be detected while the continuity between the batteries 11 and 12 is maintained.

Next, the detailed operation of the vehicle power supply device 1 described in the above outline will be described with reference to the flowchart of FIG. The μCOM 14 needs to connect the main battery 11 and the sub battery 12, and when the switches Q1 to Q4 are turned on, the failure of the switches Q1 to Q4 is detected every predetermined diagnostic cycle (for example, 1s to 10s). Start the self-diagnosis process. In the self-diagnosis process, the μCOM 14 executes not only the above-mentioned sticking failure but also a failure diagnosis of the overcurrent and current detection unit 13.

First, in order to detect the overcurrent, the μCOM 14 takes in the detection value of the current detection unit 13 and measures the currents I1 and I2 flowing in the branch paths L1 and L2 (step S1). Next, μCOM 14 adds the currents I1 and I2 to calculate the total current I0 (step S2). Then, if the total current I0 is out of the predetermined range (N in step S3), the μCOM 14 diagnoses the overcurrent (step S4) and proceeds to step S5. If the total current I0 is within the predetermined range (Y in step S3), the μCOM 14 determines that it is normal and immediately proceeds to step S5.

In step S5, μCOM 14 detects a failure of the current detection unit 13 based on the comparison of the currents I1 and I2. If the shunt resistors 13A of the plurality of current detection units 13 have the same resistance value, the currents I1 and I2 have the same value. Therefore, as a result of comparing the currents I1 and I2, the μCOM 14 determines that the failure is a failure if the difference is equal to or higher than a predetermined value (Y in step S6), diagnoses the failure of the current detection unit 13 (step S7), and then steps S8. Proceed to. On the other hand, μCOM14 determines that the currents I1 and I2 are normal if there is no difference as a result of comparing the currents I1 and I2 (N in step S6), and immediately proceeds to step S8.

Next, the μCOM 14 detects a sticking failure of the switches Q1 to Q4. In step S8, μCOM 14 first turns off the switches Q1 and Q2, and then turns them back on after a certain period of time (step S8). At this time, the switches Q3 and Q4 remain on. The μCOM 14 measures the currents I1 and I2 when only the switches Q1 and Q2 are off, and compares the currents I1 and I2 measured in step S1 before turning off. As a result of comparison, if the currents I1 and I2 do not fluctuate (N in step S9), μCOM 14 proceeds to the next step S11 after diagnosing a sticking failure of the switches Q1 and Q2 (step S10). On the other hand, as a result of comparison, if there is a fluctuation in the currents I1 and I2 (Y in step S9), μCOM 14 determines that it is normal and immediately proceeds to step S11.

In step S11, the μCOM 14 first turns off the switches Q3 and Q4, and then turns them back on after a certain period of time. At this time, the switches Q1 and Q2 remain on. The μCOM 14 measures the currents I1 and I2 when only the switches Q3 and Q4 are off, and compares the currents I1 and I2 measured in step S1 before turning off. As a result of comparison, if the currents I1 and I2 do not fluctuate (N in step S12), the μCOM 14 ends the process after diagnosing a sticking failure of the switches Q3 and Q4 (step S13). On the other hand, as a result of comparison, if there is a fluctuation in the currents I1 and I2 (Y in step S12), μCOM14 is diagnosed as normal (step S14), and the process is terminated.

When the μCOM 14 performs a failure diagnosis as a result of executing the above-mentioned self-diagnosis process, it notifies the driver to that effect or switches from automatic operation to manual operation.

According to the above-described embodiment, after the μCOM 14 turns on and controls a plurality of switches Q1 to Q4, the switches Q1 to Q4 are sequentially controlled off for each branch path L1 and L2 for a certain period of time, and at this time, a plurality of switches Q1 to Q4 are turned on. Failure is detected based on the currents I1 and I2 detected by the current detection unit 13. As a result, the current continues to flow through the branch paths L1 and L2 that are not off-controlled, so that a sticking failure can be detected while the switches Q1 to Q4 are on while both ends are conducting.

Further, as described above, when one of the branch paths L1 and L2 is cut off in the normal state, the currents I1 and I2 are the total current I0 × 1/2 to 0A or the total current I0 × 1/2 to twice the total current I0. It fluctuates greatly. On the other hand, at the time of failure, the currents I1 and I2 do not fluctuate. Therefore, the current detection unit 13 may have an accuracy of detecting three stages of 0A, I0 × 1/2, and I0, and the shunt resistor 13A does not need to be temperature-corrected. Therefore, the failure of the switches Q1 to Q4 can be detected with high accuracy by using the inexpensive current detection unit 13.

Further, according to the above-described embodiment, the μCOM 14 detects a failure of the current detection unit 13 by comparing the currents detected by the plurality of current detection units 13 when the plurality of switches Q1 to Q4 are on. is doing. As a result, the failure of the current detection unit 13 can be easily detected.

As the shunt resistance 13A described above, a resistance element may be used, or as shown in FIG. 7, the resistance component of the existing bus bar 15 may be used as the shunt resistance 13A. As shown in the figure, the switches Q1 to Q4 and the differential amplifier 13B of the current detection unit 13 are mounted on the substrate 17. A bus bar 16 for connecting the switches Q1 to Q4 to the main battery 11 and a bus bar 15 for connecting the switches Q1 to the sub battery 12 are mounted on the board 17.

In the example shown in FIG. 7, a bus bar 15 for connecting to the sub-battery 12 is used as the shunt resistor 13A. That is, one of the two inputs of the differential amplifier 13B is connected at a position on the switch Q1 to Q4 side of the bus bar 15, and the other is connected at a position away from the connection position with one of the bus bars 15. As a result, a resistance element is not required for the shunt resistance 13A, so that cost reduction can be achieved.

Further, in the example shown in FIG. 7, the resistance component of the bass bar 15 is used as the shunt resistance 13A, but the resistance component is not limited to this. When the switches Q1 to Q4 are connected to the main battery 11 and the sub battery 12 with the wiring pattern printed on the board 17 instead of the bus bar 15, the resistance element of the wiring pattern is used as the shunt resistance 13A. May be good.

Further, according to the above-described embodiment, the switches Q1 and Q2 are connected in parallel in order to withstand a large current and for redundancy, and the two switches Q1 are connected to one branch path L1. Q2 was provided. Further, the switches Q3 and Q4 are connected in parallel, and two switches Q3 and Q4 are provided for one branch path L2. However, the present invention is not limited to this, and it is sufficient that at least one switch is provided in one branch path L1 and L2.

Further, according to the above-described embodiment, the current path is branched into two branch paths L1 and L2, but the current path is not limited to this. The branch paths L1 and L2 may be branched into a plurality of branches, and may be branched into three or more.

Further, according to the above-described embodiment, the failure detection device detects the failure of the switches Q1 to Q4 provided between the batteries 11 and 12, but is not limited to this. It may be used for failure detection of a switch provided between the batteries 11 and 12 and the loads Lo1 and Lo2.

The present invention is not limited to the above embodiment. That is, it can be variously modified and carried out within a range that does not deviate from the gist of the present invention.

1 Vehicle power supply device (switch failure detection device)
11 Main battery (power supply)
12 Sub-battery (power supply)
13 Current detection unit 13A Shunt resistance 14 μCOM (Switch control unit, 1st failure detection unit, 2nd failure detection unit)
15 Bus bar 17 Board L1 Branch route L2 Branch route Lo1 Load Lo2 Load Q1 to Q4 switches

Claims (3)

Multiple switches provided on each of the multiple branch paths that branch the current path in parallel, and
A plurality of current detectors for detecting the current flowing in each of the plurality of branch paths, and
After the plurality of switches are turned on, the switch control unit that controls the switches off in order for each branch path for a certain period of time,
A first failure detection unit that detects a failure of the switch based on the currents flowing in the plurality of branch paths detected by the plurality of current detection units while the switch control unit controls the switch.
A switch failure detection device , wherein the plurality of switches are connected in parallel with each other . A board on which the plurality of switches are mounted and
A wiring pattern or bus bar provided on the board for connecting the plurality of switches to a power source or load is provided.
The switch failure detection device according to claim 1, wherein the current detection unit detects a current flowing in the branch path by using the wiring pattern or the resistance value of the bus bar as a shunt resistance. A claim comprising a second failure detection unit that detects a failure of the current detection unit by comparing the currents detected by the plurality of current detection units when the plurality of switches are on. Item 2. The switch failure detection device according to Item 1.

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