Diagnosis device

Abstract

To provide a diagnosis device capable of appropriately detecting ON fixation of an ideal diode.SOLUTION: In a diagnosis device for detecting an abnormality of an ideal diode in an electric circuit including a DC-DC converter, a battery, and an ideal diode in which an output of the DC-DC converter is connected to an anode side and the battery is connected to a cathode side, the diagnosis device comprises: an acquisition unit that acquires an output voltage of the DC-DC converter in a state where an operation is stopped with respect to the ideal diode using the output of the DC-DC converter as a power source; and a determination unit that determines that the ideal diode is abnormal when the output voltage is equal to or higher than a predetermined threshold.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a diagnostic device for diagnosing the control of an ideal diode.

Background Art

[0002] Patent Document 1 discloses an in-vehicle electric circuit using an ideal diode that realizes ideal diode characteristics in which the forward voltage is zero and current flows only in one direction.

[0003] This ideal diode is realized, for example, by a circuit including at least a metal oxide semiconductor field effect transistor (hereinafter referred to as "MOSFET") that operates in synchronous rectification and a gate control function for switching the conduction state (ON operation) / cut-off state (OFF operation) of this MOSFET. Generally, as an ideal diode, a configuration in which a discrete MOSFET is controlled using an ideal diode IC in which a MOSFET and a gate control function are integrated into a circuit, or an ideal diode controller IC in which only the gate control function is integrated into a circuit, is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In an ideal diode, if an abnormality occurs in the gate control function and the MOSFET remains conducting, that is, a so-called ON-fixation symptom occurs, an unintended reverse current will occur. Since this reverse current significantly affects the circuit using the ideal diode, it is necessary to appropriately detect the ON-fixation symptom of the ideal diode.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a diagnostic device that can appropriately detect an ideal diode being stuck in the ON state. [Means for solving the problem]

[0007] In order to solve the above problem, one aspect of the disclosed technology is a diagnostic device that detects an abnormality in an ideal diode in an electric circuit that includes a DCDC converter, a battery, and an ideal diode that has the output of the DCDC converter connected to its anode side and the battery connected to its cathode side. The diagnostic device includes an acquisition unit that acquires the output voltage of the DCDC converter when the ideal diode, which is powered by the output of the DCDC converter, is in a stopped state, and a determination unit that determines that the ideal diode is abnormal if the output voltage is equal to or greater than a predetermined threshold. [Effects of the Invention]

[0008] According to the diagnostic device of the present disclosure, when the power supply for the ideal diode is taken from the output of the DC-DC converter, if the ideal diode is stuck on, the battery voltage will appear on the output side even if the operation of the DC-DC converter stops. Therefore, the symptom of the ideal diode being stuck on can be properly detected based on the output voltage of the DC-DC converter. [Brief explanation of the drawings]

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

[0010] The diagnostic device according to the present disclosure utilizes the fact that if the ideal diode is stuck ON, the anode side and the cathode side are electrically conductive, and detects the occurrence of the ideal diode being stuck ON based on whether or not the battery voltage appears at the output terminal of the DCDC converter via the ideal diode when the operation of the DCDC converter is stopped. Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0011] <Embodiment> [composition] Fig. 1 is a block diagram showing a schematic configuration of an electric circuit including a diagnostic device 40 and an ideal diode 30 according to an embodiment of the present disclosure. The block diagram shown in Fig. 1 includes a DC-DC converter 10, a battery 20, an ideal diode 30, and a diagnostic device 40. The DC-DC converter 10, the battery 20, the ideal diode 30, and the diagnostic device 40 can be mounted on a vehicle or the like.

[0012] The DC-DC converter 10 is a power converter that can convert power of a first voltage input from a power source (not shown), such as a generator or a battery, into power of a predetermined second voltage and output it. The DC-DC converter 10 includes components such as a step-up / step-down circuit made up of switching elements and coils, and a driver circuit made up of a microcomputer and the like that controls the step-up / step-down operation.

[0013] The battery 20 is a secondary battery configured to be chargeable and dischargeable, such as a lithium ion battery. The battery 20 is connected to the DC-DC converter 10 via an ideal diode 30 so that it can be charged by the power output by the DC-DC converter 10. The battery 20 can also supply the stored power to a predetermined device (not shown).

[0014] The ideal diode 30 is a diode that realizes ideal diode characteristics with a forward voltage of zero and allows current to flow in only one direction. This ideal diode 30 can greatly reduce power loss compared to discrete rectifier diodes. The ideal diode 30 illustrated in FIG. 1 includes a discrete MOSFET 31 and an ideal diode controller IC 32.

[0015] This ideal diode 30 is inserted between the DC-DC converter 10 and the battery 20 with the output of the DC-DC converter 10 connected to the anode side and the battery 20 connected to the cathode side. More specifically, the source of the MOSFET 31 (the anode side of the body diode) is connected to the output of the DC-DC converter 10, and the drain of the MOSFET 31 (the cathode side of the body diode) is connected to the battery 20.

[0016] The ideal diode controller IC 32 is a drive circuit that controls the gate voltage (GATE) of the MOSFET 31 to control the electrical conduction / blocking between the source and drain of the MOSFET 31. This ideal diode controller IC 32 is equipped with a reverse current prevention function that controls the MOSFET 31 to the off state when a current flowing backward from the battery 20 (OUT) side to the DC-DC converter 10 (IN) side is detected. The power supply (Vcc) of the ideal diode controller IC 32 is connected to the output side of the DC-DC converter 10, and the ideal diode controller IC 32 can operate if there is a voltage output (power supply) from the DC-DC converter 10. When the ideal diode controller IC 32 stops (shuts down) without power supply, the MOSFET 31 is controlled to be in the off state (normally off).

[0017] Note that for the ideal diode 30, the configuration using the discrete MOSFET 31 and the ideal diode controller IC 32 shown in FIG. 1 may be used, or an ideal diode IC 33 in which a MOSFET and a controller are integrated on one chip as shown in FIG. 4 may be used.

[0018] The diagnostic device 40 is configured to diagnose the control of the ideal diode 30. This diagnostic device 40 acquires (inputs) at least information about the operating state (operating, stopped) of the DC-DC converter 10 and information about the voltage (hereinafter referred to as "output voltage") that appears on the output side of the DC-DC converter 10. When the DC-DC converter 10, the battery 20, the ideal diode 30, and the diagnostic device 40 are mounted on a vehicle, the diagnostic device 40 further acquires (inputs) an IG signal that is information indicating the ignition state (IG-ON, IG-OFF) of the vehicle. Then, based on the acquired pieces of information, the diagnostic device 40 performs a diagnosis to determine whether or not there is an abnormality in the control of the ideal diode 30. The diagnostic control performed by the diagnostic device 40 will be described in detail below.

[0019] [control] Next, with further reference to FIGS. 2 and 3, the control performed by the diagnostic device 40 according to an embodiment of the present disclosure will be described.

[0020] 2 is a flowchart illustrating the procedure for diagnostic control of the ideal diode 30 executed by the diagnostic device 40 when the IG-OFF state is reached. The diagnostic control of the ideal diode 30 illustrated in FIG. 2 is initiated when the ignition of the vehicle is turned off (IG-OFF). The ignition state of the vehicle can be determined by the IG signal.

[0021] (Step S201) The diagnostic device 40 determines whether the DC-DC converter 10 (DDC) is in a stopped state. This determination can be made based on information about the operating state of the DC-DC converter 10 or an IG signal indicating the ignition state of the vehicle. If the diagnostic device 40 determines that the DC-DC converter 10 is in a stopped state (Yes in step S201), the process proceeds to step S202.

[0022] (Step S202) The diagnostic device 40 acquires the output voltage of the DC-DC converter 10 (DDC). This output voltage can be acquired by, for example, using a voltage sensor to monitor the output terminal of the DC-DC converter 10. Once the output voltage of the DC-DC converter 10 (DDC) is acquired by the diagnostic device 40, the process proceeds to step S203.

[0023] (Step S203) The diagnostic device 40 determines whether the output voltage of the DC-DC converter 10 is equal to or greater than a predetermined threshold. This determination is made to confirm that the anode and cathode of the ideal diode 30 are electrically connected and that the power supply voltage required for operation is being supplied to the ideal diode 30. Therefore, this threshold is set to a predetermined value (but smaller than the voltage of the battery 20) that is greater than the voltage that would appear as the voltage on the output side of the DC-DC converter 10 if the ideal diode 30 were in a cutoff state.

[0024] If the diagnostic device 40 determines that the output voltage of the DC-DC converter 10 is equal to or greater than the threshold value (step S203, Yes), the process proceeds to step S204. On the other hand, if the diagnostic device 40 determines that the output voltage of the DC-DC converter 10 is less than the threshold value (step S203, No), the process proceeds to step S205.

[0025] (Step S204) The diagnostic device 40 determines that an abnormality has occurred in the control of the ideal diode 30. Specifically, the diagnostic device 40 determines that the ideal diode 30 has a symptom of being stuck ON (the ideal diode 30 is operating) because the output voltage of the DC-DC converter 10 indicates a voltage value (corresponding to the voltage value of the battery 20) equal to or higher than the threshold value even though the DC-DC converter 10 is stopped. When the diagnostic device 40 determines that an abnormality has occurred in the control of the ideal diode 30, the diagnostic control of the ideal diode 30 when IG-OFF is terminated.

[0026] (Step S205) The diagnostic device 40 determines that the control of the ideal diode 30 is normal. Specifically, the diagnostic device 40 determines that the ideal diode 30 does not have a stuck-on symptom (the ideal diode 30 is not operating) because the output voltage of the DC-DC converter 10 is less than the threshold value when the DC-DC converter 10 is stopped. When the diagnostic device 40 determines that the control of the ideal diode 30 is normal, the diagnostic control of the ideal diode 30 when IG-OFF is ended.

[0027] 3 is a flowchart illustrating the procedure for diagnostic control of the ideal diode 30 executed by the diagnostic device 40 when the ignition is turned on. The diagnostic control of the ideal diode 30 illustrated in FIG. 3 is started when the ignition of the vehicle is turned on (IG-ON). The ignition state of the vehicle can be determined by the IG signal.

[0028] (Step S301) The diagnostic device 40 judges whether the result of the diagnostic control (FIG. 2) of the ideal diode 30 executed when the IG-OFF is "normal" or not. This judgment is made to prevent the occurrence of an erroneous diagnosis when the IG-ON is turned on immediately after the IG-OFF. One cause of an erroneous diagnosis is that the output voltage of the DC-DC converter 10, which has stopped operating, has not dropped sufficiently at the time of diagnosis.

[0029] If the diagnostic device 40 determines that the diagnostic result of the ideal diode 30 when IG-OFF is normal (YES in step S301), the process proceeds to step S302. On the other hand, if the diagnostic device 40 determines that the diagnostic result of the ideal diode 30 when IG-OFF is abnormal (NO in step S301), the process proceeds to step S303.

[0030] (Step S302) The diagnostic device 40 determines whether or not a predetermined time has elapsed since the vehicle ignition was turned off (IG-OFF). This determination is made to wait until the output voltage that appeared on the output side of the DCDC converter 10 during operation has sufficiently decreased until diagnosis can be performed after stopping. Therefore, this predetermined time is appropriately set based on, for example, the time required to discharge the charge of the capacitor connected to the output side of the DCDC converter 10. That is, until the predetermined time has elapsed, no new determination is made, and the diagnosis result of the most recent normal state is retained. When the predetermined time has elapsed since the vehicle ignition was turned off (IG-OFF), the process proceeds to step S303.

[0031] (Step S303) The diagnostic device 40 determines whether or not the DCDC converter 10 (DDC) is in a stopped state. This determination is made based on information regarding the operating state of the DCDC converter 10 because correct diagnosis cannot be performed if the DCDC converter 10 starts operating due to IG-ON.

[0032] When the diagnostic device 40 determines that the DCDC converter 10 is in a stopped state (step S303, yes), the process proceeds to step S304. On the other hand, when the diagnostic device 40 determines that the DCDC converter 10 is already in an operating state (step S303, no), the diagnostic control of the ideal diode 30 ends without performing the diagnosis at this timing.

[0033] (Step S304) The diagnostic device 40 acquires the output voltage of the DCDC converter 10 (DDC). This output voltage can be acquired, for example, by monitoring the output terminal of the DCDC converter 10 using a voltage sensor or the like. When the diagnostic device 40 acquires the output voltage of the DCDC converter 10 (DDC), the process proceeds to step S305.

[0034] (Step S305) The diagnostic device 40 determines whether the output voltage of the DCDC converter 10 is equal to or higher than a predetermined threshold value. This determination is made to confirm that the anode side and the cathode side of the ideal diode 30 are conducting and that the power supply voltage necessary for the operation of the ideal diode 30 is being supplied. The threshold value is as described above.

[0035] When the diagnostic device 40 determines that the output voltage of the DCDC converter 10 is equal to or higher than the threshold value (step S305, yes), the process proceeds to step S306. On the other hand, when the diagnostic device 40 determines that the output voltage of the DCDC converter 10 is lower than the threshold value (step S305, no), the process proceeds to step S307.

[0036] (Step S306) The diagnostic device 40 determines that there is an abnormality in the control of the ideal diode 30. Specifically, since the output voltage of the DCDC converter 10 indicates a voltage value equal to or higher than the threshold value (corresponding to the voltage value of the battery 20) even though the DCDC converter 10 has stopped, the diagnostic device 40 determines that the ideal diode 30 has a symptom of being stuck ON (the ideal diode 30 is operating). When the diagnostic device 40 determines that there is an abnormality in the control of the ideal diode 30, the diagnostic control of the ideal diode 30 at the time of IG-ON ends.

[0037] (Step S307) The diagnostic device 40 determines that the control of the ideal diode 30 is normal. Specifically, since the output voltage of the DCDC converter 10 indicates less than the threshold value in a state where the DCDC converter 10 has stopped, the diagnostic device 40 determines that the ideal diode 30 does not have a symptom of being stuck ON (the ideal diode 30 is not operating). When the diagnostic device 40 determines that the control of the ideal diode 30 is normal, the diagnostic control of the ideal diode 30 at the time of IG-ON ends.

[0038] <Effect> According to one embodiment of the present disclosure described above, the power supply of the ideal diode 30 inserted between the DCDC converter 10 and the battery 20 is supplied from the output side of the DCDC converter 10. With this configuration, the diagnostic device 40 monitors the output voltage of the DCDC converter 10 when it stops, thereby detecting symptoms of ON sticking (such as a failure of the ideal diode controller IC32, a failure of the ideal diode IC33, and a loss of the reverse current prevention function) in which the ideal diode 30 continues to conduct between the anode side and the cathode side.

[0039] Further, in the diagnostic device 40 according to the present embodiment, when detecting symptoms of ON sticking of the ideal diode 30, by issuing a notification via a display device, an audio device (not shown), etc., indicating that an abnormality has occurred, it is possible to alert the user of the vehicle, etc.

[0040] In the above embodiment, although the configuration in which the power supplies (Vcc) of the ideal diode controller IC32 and the ideal diode IC33 are connected to the output side of the DCDC converter 10 has been described, they may be connected to the battery 20. Even when the ideal diode 30 is always operated with the power of the battery 20, it is possible to perform the above-described diagnostic control of the ideal diode 30 to determine an ON sticking abnormality.

[0041] As described above, one embodiment of the present disclosure technology has been described. However, the present disclosure can be regarded as not only a diagnostic device, but also a method executed by the diagnostic device, a program for the method, a computer-readable non-transitory storage medium storing the program, a vehicle equipped with the diagnostic device, etc.

Industrial Applicability

[0042] The diagnostic device of the present disclosure can be used when diagnosing the control of an ideal diode, etc.

Explanation of Signs

[0043] 10 DCDC converter (DDC) 20 Battery 30 Ideal Diode 31 MOSFET 32 Ideal Diode Controller IC 33 Ideal diode IC 40 Diagnostic Equipment

Claims

1. A diagnostic device for detecting an abnormality of an ideal diode in an electric circuit including a DC-DC converter, a battery, and an ideal diode having an output of the DC-DC converter connected to an anode side and the battery connected to a cathode side, comprising: for the ideal diode powered by the output of the DC-DC converter, an acquisition unit that acquires the output voltage of the DC-DC converter in a state where the operation has stopped; a determination unit that determines that the ideal diode is abnormal when the output voltage is equal to or higher than a predetermined threshold value.

2. The electric circuit is mounted on a vehicle, The acquisition unit acquires the output voltage after the ignition of the vehicle is turned off and the operation of the DC-DC converter has stopped. The diagnostic device according to claim 1.

3. The electric circuit is mounted on a vehicle, The acquisition unit acquires the output voltage after the ignition of the vehicle is turned on and before the DC-DC converter operates. The diagnostic device according to claim 1 or 2.

4. When the determination unit determines that the ideal diode is normal when the ignition of the vehicle is turned off, the determination unit does not make a new determination for a predetermined time after the normal determination. The diagnostic device according to claim 2 or 3.

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