Fault detection device

Abstract

A fault detection apparatus includes first, second, and third switching units, and a fault detection unit that detects an on-fault of the first and second switching units. The failure detection unit includes: a voltage application unit that applies a specified voltage to the connection point in a superimposed manner when the first, second, and third switching units are all controlled to be turned off; a voltage detection unit that detects a voltage of the connection point in an application state of the voltage application unit; and an on-failure determination unit that determines that at least one of the first and second switching units has an on-failure when the voltage detected by the voltage detection unit is not greater than or equal to a threshold value.

Description

Technical Field

[0001] The present invention relates to a fault detection device. Background Art

[0002] In the related art, there has been proposed a fault detection device that detects abnormalities such as an on fault and an off fault in a switching unit such as a field effect transistor (FET) (see Patent Document 1).

[0003] Reference List

[0004] Patent Literature

[0005] Patent Document 1: JP2021-85733A Summary of the invention

[0006] In the fault detection device described in Patent Document 1, back-to-back metal oxide semiconductor field effect transistors (MOSFETs) are targets for fault detection. Here, in a configuration using a diode or drain-connected MOSFET, even when the MOSFET is turned off, a bypass path exists due to a parasitic diode, and the MOSFET cannot be completely turned off, so a conduction fault cannot be detected.

[0007] As a countermeasure, when a DC / DC converter is provided as a power supply in each diode or configuration, a potential difference can be provided between MOSFETs by increasing or decreasing the output voltage, and a conduction fault can be detected. However, in practice, the output voltage is determined by the equipment (such as vehicle equipment, etc.) to which the voltage is supplied, and since these equipments basically operate at the same voltage, it is impossible to freely increase or decrease the voltage, and therefore it is impossible to detect a conduction fault.

[0008] Therefore, two combined diodes or configurations in a pair of back-to-back switching cells are required, and at least four switching cells are required, which increases the number of switching cells.

[0009] Therefore, the present invention provides a fault detection device capable of detecting a conduction fault while suppressing the number of switching units.

[0010] A fault detection device according to the present disclosure includes: a first switch unit, wherein the first terminal is connected to a first battery that outputs a predetermined voltage, the second terminal is connected to a connection point, and the first switch unit includes a parasitic diode that prevents current from flowing from the second terminal to the first terminal; a second switch unit, wherein the first terminal is connected to a second battery that outputs a predetermined voltage, the second terminal is connected to a connection point, and the second switch unit includes a parasitic diode that prevents current from flowing from the second terminal to the first terminal; a third switch unit, wherein the first terminal is connected to a load, the second terminal is connected to the connection point, and the third switch unit includes a parasitic diode that prevents current from flowing from the second terminal to the first terminal; and a fault detection unit that detects a conduction fault of the first switch unit and the second switch unit. The fault detection unit includes: a voltage applying unit, which applies a specified voltage to a connection point in a superimposed manner when the first switch unit, the second switch unit, and the third switch unit are all controlled to be disconnected; a voltage detection unit, which detects the voltage of the connection point under the application state of the voltage applying unit; and a conduction fault determination unit, which determines that at least one of the first switch unit and the second switch unit has a conduction fault when the voltage detected by the voltage detection unit exceeds a predetermined voltage and is not greater than or equal to a threshold value, and the threshold value is set to be less than a value obtained by subtracting a voltage drop caused by a parasitic diode of the first switch unit and a parasitic diode of the second switch unit after adding the specified voltage to the predetermined voltage.

[0011] According to the present invention, it is possible to provide a fault detection device capable of detecting a conduction fault while suppressing the number of switching units. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a block diagram of a power supply system including a fault detection device according to an embodiment.

[0013] Figure 2 It is shown Figure 1 Block diagram showing details of the transfer switch.

[0014] Figure 3 It is shown Figure 2 A circuit diagram of a detailed example of a single pulse boost circuit is shown.

[0015] Figure 4 is a timing chart showing a voltage state when a conduction failure does not occur.

[0016] Figure 5 is a timing chart showing a voltage state when a conduction failure occurs.

[0017] Figure 6 is a flowchart showing a conduction failure determination method in the MCU of the transfer switch according to the present embodiment. DETAILED DESCRIPTION

[0018] The present invention will be described below with reference to preferred embodiments. The present invention is not limited to the embodiments described below, and the embodiments may be appropriately modified without departing from the scope of the present invention. In the embodiments to be described below, there may be portions in which a portion of the illustration and description of a configuration is omitted, and needless to say, within the scope of not contradicting the contents to be described below, known or well-known techniques are appropriately applied to the details of the omitted techniques.

[0019] Figure 1 is a block diagram of a power supply system including the fault detection device according to the present embodiment. Figure 1 The illustrated power supply system 1 supplies power to a load L and includes a high-voltage and low-voltage DC power supply 10 , a main battery (first battery) MB, a battery fuse terminal (hereinafter referred to as BFT) 20 , a sub-battery (second battery) SB, a BFT 30 , an electronic control unit (ECU) 40 , and a transfer switch (fault detection device) 50 .

[0020] The high and low voltage DC power source 10 is implemented by a DC / DC converter that reduces the voltage of the high voltage power source. The high and low voltage DC power source 10 reduces the voltage from the high voltage power source to a predetermined voltage (e.g., 12V) of the load L, which is an operating voltage. After the voltage is reduced, the high and low voltage DC power source 10 supplies power to the conversion switch 50 via the first fuse F1 in the BFT 20.

[0021] The main battery MB can supply a predetermined voltage (eg, 12V) as an operating voltage to the load L, and is implemented by, for example, a lead storage battery. The main battery MB supplies power to the transfer switch 50 through the second fuse F2 in the BFT 20 .

[0022] The sub-battery SB can supply a predetermined voltage (e.g., 12V) as an operating voltage to the load L and is implemented by, for example, a lead storage battery or a lithium ion battery. The sub-battery SB can supply the same voltage as the main battery MB and supplies power to the transfer switch 50 via the third fuse F3 in the BFT 30.

[0023] The ECU 40 corresponds to a high-level device that controls the conversion switch 50. The conversion switch 50 switches the power supply path to the load L. In the present embodiment, it is assumed that the load L is an important load required for the vehicle to travel, for example. The power supply system 1 includes the conversion switch 50 in order to avoid a situation where power cannot be supplied to the load L. For example, when power cannot be supplied from the main battery MB side (including the high-voltage and low-voltage DC power supply 10), the power supply system 1 controls the conversion switch 50 to supply power to the load L from the sub-battery SB.

[0024] The conversion switch 50 includes first to third switch units SW1 to SW3, a memory control unit (MCU) 51, and a single pulse boost circuit (boost unit) 52. The MCU 51 and the single pulse boost circuit 52 constitute a fault detection portion (fault detection unit) 50a, which detects whether at least one of the first switch unit SW1 and the second switch unit SW2 has a conduction fault.

[0025] The first switch unit SW1 is implemented by a MOSFET, and a source terminal (first terminal) S is connected to the BFT 20 side, that is, the main battery MB, and a drain terminal (second terminal) D is connected to the connection point P. The gate terminal G is configured to receive a gate signal from the ECU 40 or the MCU 51, and the MCU 51 receives a command from the ECU 40. The first switch unit SW1 includes a parasitic diode BD1, which allows current to flow from the source terminal S to the drain terminal D, and blocks current from the drain terminal D to the source terminal S.

[0026] The second switch unit SW2 is implemented by a MOSFET, and a source terminal (first terminal) S is connected to the BFT 30 side, that is, the sub-battery SB, and a drain terminal (second terminal) D is connected to the connection point P. Similar to the first switch unit SW1, the gate terminal G receives a gate signal from the ECU 40 or the MCU 51. The second switch unit SW2 includes a parasitic diode BD2 that allows current to flow from the source terminal S to the drain terminal D and blocks current from the drain terminal D to the source terminal S. The first switch unit SW1 and the second switch unit SW2 constitute a diode or a circuit.

[0027] The third switch unit SW3 is also implemented by a MOSFET, and a source terminal (first terminal) S is connected to the load L, and a drain terminal (second terminal) D is connected to the connection point P. Similar to the first switch unit SW1, a gate terminal G receives a gate signal from the ECU 40 or the MCU 51. The third switch unit SW3 includes a parasitic diode BD3 that allows current to flow from the drain terminal D to the source terminal S, and blocks current from flowing from the drain terminal D to the source terminal S.

[0028] Figure 2 It is shown Figure 1 A block diagram of the details of the transfer switch 50 is shown. Figure 2 As shown, the MCU 51 of the conversion switch 50 includes an output part (output unit) 51a, a voltage detection part (voltage detection unit) 51b and a conduction failure determination part (conduction failure determination unit) 51c so as to determine the conduction failure of the first switch unit SW1 and the second switch unit SW2.

[0029] The output portion 51a outputs a voltage, for example, a 5V voltage, for application to the connection point P in a superimposed manner. The output portion 51a outputs a single pulse voltage with the shortest conduction time. The single pulse boosting circuit 52 boosts the single pulse voltage from the output portion 51a, and applies the boosted single pulse voltage to the connection point P in a superimposed manner. The output portion 51a and the single pulse boosting circuit 52 constitute a voltage applying portion (voltage applying unit) 50V. When the ECU 40 (see Figure 1 ) or when the MCU 51 controls the first switch unit SW1, the second switch unit SW2 and the third switch unit SW3 to be all turned off, the voltage applying part 50V applies the boosted voltage based on the single pulse voltage as the specified voltage to the connection point P in a superimposed manner.

[0030] Figure 3 It is shown Figure 2 FIG. 5 is a circuit diagram of a detailed example of a single pulse boost circuit 52. Figure 3 As shown, for example, the single pulse boost circuit 52 includes an NPN transistor Q1 , resistors R1 , R2 , a capacitor C1 , and Schottky barrier diodes SD1 , SD2 .

[0031] From the output portion 51a (see Figure 2 ) is input to the base B of the NPN transistor Q1 through the resistor R1. The collector C of the NPN transistor Q1 is connected to the main battery MB through the resistor R2. The emitter E of the NPN transistor Q1 is grounded.

[0032] The connection point P1 between the main battery MB and the resistor R2 is connected to the anode of the Schottky barrier diode SD1. The cathode of the Schottky barrier diode SD1 is connected to the anode of another Schottky barrier diode SD2. The cathode of the Schottky barrier diode SD2 serves as a boost output section (output section of a specified voltage).

[0033] A connection point P2 between the two Schottky barrier diodes SD1 and SD2 is connected to a connection point P3 between the resistor R2 and the collector C of the NPN transistor Q1 through a capacitor C1.

[0034] Reference again Figure 2. The voltage detection part 51b detects the voltage applied to the connection point P. The conduction fault determination part 51c determines whether a conduction fault has occurred in the first switch unit SW1 or the second switch unit SW2 based on the voltage detected by the voltage detection part 51b. The conduction fault determination part 51c determines the conduction fault based on whether the voltage detected by the voltage detection part 51b is greater than or equal to a threshold value. The threshold value is set to a value exceeding a predetermined voltage, which is the output voltage of the battery MB, SB, and is less than a value obtained by subtracting a voltage drop due to parasitic diodes BD1, BD2 (described later) from a value obtained by adding a specified voltage to a predetermined voltage. When the detected voltage is greater than or equal to the threshold value, the conduction fault determination part 51c determines that a conduction fault has not occurred in the first switch unit SW1 or the second switch unit SW2. On the other hand, when the detected voltage is not greater than or equal to the threshold value, the conduction fault determination part 51c determines that a conduction fault has occurred in at least one of the first switch unit SW1 and the second switch unit SW2.

[0035] Next, we will refer to Figure 2 , 4 5 and 5 describe an overview of the conduction failure determination method of the conduction failure determination section 51c. Figure 4 is a timing diagram showing the voltage state when no conduction failure occurs, Figure 5 is a timing chart showing a voltage state when a conduction failure occurs.

[0036] First, the case where no conduction failure occurs will be described. Figure 2 As shown, the first switch unit SW1 and the second switch unit SW2 have parasitic diodes BD1 and BD2, respectively, and the parasitic diodes BD1 and BD2 are oriented to allow current to flow from the batteries MB and SB to the connection point P. Here, if the voltage (predetermined voltage) of the main battery MB and the sub-battery SB is 12V, a voltage obtained by subtracting the voltage drop of the parasitic diode BD1 from 12V is applied to the connection point P. For example, when the voltage drop of the parasitic diodes BD1 and BD2 is 0.6V, a voltage of 12V - 0.6V = 11.4V is applied to the connection point P.

[0037] The voltage applying section 50V applies a specified voltage to the connection point P, and the voltage is applied to the connection point P in a superimposed manner. Here, it is assumed that the output section 51a is Figure 4 At the time point t11 ​​shown, a 5V voltage is output. As time passes, the 5V voltage is boosted to 12V. Therefore, a voltage of 11.4V + 12V (= 23.4V) is finally applied to the connection point P. Here, the threshold is set to be less than 23.4V. Figure 4In the example shown, the voltage detected by the voltage detection portion 51b is greater than or equal to the threshold value at least at time point t12. The state in which the detected voltage is greater than or equal to the threshold value continues at least until time point t13 when the single pulse voltage is disconnected. Therefore, when the detected voltage is greater than or equal to the threshold value, the conduction failure determination portion 51c determines that a conduction failure does not occur in the first switch unit SW1 or the second switch unit SW2.

[0038] On the other hand, when a conduction failure occurs, the connection point P is in a conductive state with at least one of the main battery MB and the sub-battery SB. Therefore, the voltage of the connection point P is fixed to a predetermined voltage. Therefore, even if the output portion 51a is Figure 5 At the time point t21 shown, a 5 V voltage is output, and a 12 V voltage is also maintained until a time point t22 when the single pulse voltage is disconnected. Here, the threshold value is a value exceeding 12 V. Therefore, when the detected voltage is not greater than or equal to the threshold value, the conduction failure determination portion 51 c determines that a conduction failure has occurred in at least one of the first switch unit SW1 and the second switch unit SW2.

[0039] like Figure 4 As shown, when the single pulse voltage is disconnected, the detected voltage has a maximum value near the time point t13. Therefore, the voltage detection part 51b preferably detects the voltage of the connection point P near the time point t13 when the single pulse voltage is disconnected. Therefore, it is possible to prevent erroneous determination at the moment when the voltage is not sufficiently boosted before the time point t12. Here, as an example, near the time point t13 refers to a time period from the time point t13 - α to the time point t13 + α, where the time α is half of the time from the time point t12 when the detected voltage matches the threshold to the time point t13 when no conduction failure occurs.

[0040] Figure 6 4 is a flow chart showing a conduction fault determination method in the MCU 51 of the transfer switch 50 according to the present embodiment. Figure 6 As shown, first, the MCU 51 sets the number of retries N (S1). For example, in this embodiment, the number of retries N is assumed to be "3".

[0041] Next, the MCU 51 turns off all the switch units SW1 to SW3 (S2). Next, the output part 51a of the MCU 51 outputs the single pulse voltage (S3). The single pulse voltage is boosted by the single pulse boost circuit 52 and applied to the connection point P.

[0042] Thereafter, the voltage detection section 51b detects the voltage (drain voltage) of the connection point P through the A / D input (S4). Next, the conduction failure determination section 51c determines whether the voltage detected in step S4 is greater than or equal to a threshold value (S5).

[0043] When the voltage detected in step S4 is not greater than or equal to the threshold value (S5: No), the MCU 51 determines whether the retry number N is "0" (S6). When the retry number N is not "0" (S6: No), the MCU 51 decrements the retry number N (S7), and the process proceeds to step S3. When the retry number N is "0" (S6: Yes), the conduction failure determination part 51c determines that at least one of the first switch unit SW1 and the second switch unit SW2 has a conduction failure, and outputs the determination result to the ECU 40 (S8). Thereafter, Figure 6 The process shown ends.

[0044] On the other hand, when the voltage detected in step S4 is greater than or equal to the threshold value (S5: Yes), the conduction failure determination section 51c determines that a conduction failure has not occurred in either the first switch unit SW1 or the second switch unit SW2 (S9). Figure 6 The process shown ends.

[0045] In this way, according to the conversion switch 50 of the present embodiment, when a conduction failure occurs from the direction of the parasitic diodes BD1, BD2 of the switch units SW1, SW2, a voltage based on the batteries MB, SB (a voltage slightly lower than a predetermined voltage) is applied to the connection point P. In addition, when determining the conduction failure, a specified voltage applied by the voltage applying part 50V is applied to the connection point P. Therefore, when the conduction failure does not occur, a voltage obtained by adding the specified voltage to a voltage slightly lower than the predetermined voltage should be detected. Therefore, by appropriately setting the threshold value, when the detection voltage at the connection point P is greater than or equal to the threshold value, the conduction failure determination part 51c can determine that a conduction failure does not occur in each of the switch units SW1, SW2.

[0046] On the other hand, during the conduction fault, the connection point P is short-circuited with the main battery MB or the sub-battery SB, and the connection point P is at a predetermined voltage. Therefore, when the voltage of the connection point P is not greater than or equal to the threshold value exceeding the predetermined voltage, the conduction fault determination portion 51c can determine that at least one of the first switch unit SW1 and the second switch unit SW2 has a conduction fault.

[0047] Furthermore, since at least three switch units SW1 to SW3 can be used to determine a conduction fault, the number of switch units can be reduced. Therefore, a fault detection device capable of detecting a conduction fault while suppressing the number of switch units SW1 to SW3 can be provided.

[0048] The voltage applying part 50V includes an output part 51a which outputs a voltage to be applied to the connection point P and a single pulse boosting circuit 52 which boosts the voltage output by the output part 51a. Therefore, a voltage such as a 5V voltage can be output from the MCU 51 to be applied to the connection point P, and the output voltage can be boosted so that a relatively high voltage can be applied. Therefore, the voltage difference at the connection point P increases between when the conduction fault occurs and when the conduction fault does not occur, and the conduction fault can be detected more appropriately.

[0049] Furthermore, since the output portion 51a outputs a single pulse voltage, unnecessary power consumption can be minimized.

[0050] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and may be modified without departing from the gist of the present invention, and known or well-known technologies may be combined.

[0051] For example, although the output portion 51a outputs a single pulse voltage in the above-described embodiment, the output portion 51a is not particularly limited to the single pulse voltage as long as the voltage can be applied to the connection point P in a superimposed manner. The conversion switch 50 includes a single pulse boost circuit 52 that boosts the voltage from the output portion 51a from 5V or the like to 12V or the like, and applies the boosted voltage to the connection point P. However, the present invention is not particularly limited thereto, and the voltage may be applied without boosting. It should be understood that the specified voltage applied in this case is greater than the voltage drop caused by the parasitic diodes BD1, BD2.

Claims

1. A fault detection device, comprising: a first switch unit, wherein a first terminal is connected to a first battery outputting a predetermined voltage, a second terminal is connected to a connection point, and the first switch unit includes a parasitic diode preventing a current from flowing from the second terminal of the first switch unit to the first terminal of the first switch unit; a second switch unit, wherein a first terminal is connected to a second battery outputting the predetermined voltage, a second terminal is connected to the connection point, and the second switch unit includes a parasitic diode preventing current from flowing from the second terminal of the second switch unit to the first terminal of the second switch unit; a third switch unit, wherein a first terminal is connected to a load, a second terminal is connected to the connection point, and the third switch unit includes a parasitic diode that prevents current from flowing from the second terminal of the third switch unit to the first terminal of the third switch unit; and a fault detection unit, which detects a conduction fault of the first switch unit and the second switch unit, wherein The fault detection unit comprises: a voltage applying unit, which applies a specified voltage to the connection point in a superimposed manner when the first switch unit, the second switch unit, and the third switch unit are all controlled to be disconnected, a voltage detection unit that detects a voltage at the connection point in an application state of the voltage applying unit, and A conduction fault determination unit that determines that at least one of the first switch unit and the second switch unit has a conduction fault when the voltage detected by the voltage detection unit exceeds the predetermined voltage and is not greater than or equal to a threshold value, wherein the threshold value is set to be smaller than a value obtained by subtracting a voltage drop caused by a parasitic diode of the first switch unit and a parasitic diode of the second switch unit after adding the specified voltage to the predetermined voltage.

2. The fault detection device according to claim 1, wherein The voltage applying unit includes an output unit that outputs a voltage to be applied to the connection point and a boosting unit that boosts the voltage output from the output unit.

3. The fault detection device according to claim 2, wherein The output unit outputs a single pulse voltage.

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