Power control device and semiconductor fault detection method

Abstract

A power control device detects faults in semiconductor switching elements in a switching circuit having semiconductor series circuits, each semiconductor series circuit having semiconductor switching elements connected in series with opposite polarities. The power control device includes: a reference resistance value storage unit that stores information about the combined resistance value between the input and output of the switching circuit; a current detection unit configured to detect the current flowing through the switching circuit; a potential difference detection unit configured to detect the input-output potential difference between the input and output of the switching circuit; a voltage drop calculation unit configured to calculate an assumed voltage drop; a voltage comparison unit configured to compare the input-output potential difference with the assumed voltage drop; and a fault identification unit configured to identify faults in the semiconductor switching elements.

Description

Technical Field

[0001] This disclosure relates to power control devices and semiconductor fault detection methods. Background Technology

[0002] For example, when supplying power from a power source to a load such as a motor, the operation of turning the load on and off is typically performed, or a semiconductor switching element capable of performing on / off control is connected between the power source and the load to adjust the load's operating parameters. In many cases, power MOSFETs are used as semiconductor switching elements.

[0003] In various devices employing semiconductor switching elements, there is a possibility of operational failure due to the malfunction of the semiconductor switching elements. Therefore, a technique for detecting malfunctions in semiconductor switching elements is needed.

[0004] Furthermore, patent document JP-A-2011-71174 discloses a technique for detecting characteristic degradation that leads to semiconductor device failure. In JP-A-2011-71174, the semiconductor device (IPD) 1 includes: a setting value storage unit 3 that stores setting values ​​based on initial characteristic values ​​of the IPD 1; and a detection circuit 4 that detects characteristic degradation of the IPD 1 based on the characteristic value of the IPD 1 at a predetermined time and the setting values ​​stored in the setting value storage unit 3. In the characteristic degradation detection method of JP-A-2011-71174, setting values ​​determined based on initial characteristic values ​​are stored, and characteristic degradation of the IPD 1 is detected based on the characteristic value of the IPD 1 at a predetermined time and the stored setting values.

[0005] In addition, patent document JP-A-2019-135819 discloses a power semiconductor module that can reduce the number of semiconductor components while improving the power redundancy of the system, and a vehicle power system including the power semiconductor module.

[0006] However, the technology disclosed in patent document JP-A-2011-71174 is intended to detect faults occurring within a semiconductor included in the internal circuitry of a single semiconductor device (IPD: intelligent power device), and cannot be used to detect faults in circuits that combine multiple semiconductor switching elements.

[0007] For example, when electronic devices are installed in a vehicle, there is a possibility that the wiring or the vehicle battery may be connected incorrectly with the polarity of the power supplied from the vehicle side reversed. Additionally, for example, there is a possibility that a power supply with a high voltage of 24V may be incorrectly connected to an electronic device that is to be supplied with a power supply voltage of 12V.

[0008] To prevent malfunctions caused by incorrect connections as described above, electronic devices installed in vehicles are typically equipped with protective circuits. As a specific example, a diode is connected in series with a semiconductor switching element to prevent abnormal current flow due to the application of voltages with opposite polarities. However, such diodes have relatively high power losses and require a considerable amount of space. Therefore, instead of a diode, another semiconductor element equivalent to the semiconductor switching element can be connected in series with opposite polarities.

[0009] In addition, in circuits that require switching very large currents, there is a possibility that sufficient current switching capability or sufficient reliability cannot be ensured by using only a single semiconductor switching element.

[0010] Therefore, for example, as in patent document JP-A-2019-135819 Figure 1 In the system shown in the middle, there are multiple semiconductor switching elements connected in series with opposite polarities and multiple semiconductor switching elements further connected in parallel.

[0011] However, when multiple semiconductor switching elements are connected in series with opposite polarities and in parallel as described above, it is difficult to detect a fault when a fault occurs in any one of the semiconductor switching elements.

[0012] For example, when power is supplied to the load side via multiple semiconductor switching elements connected in parallel, even if any one of the semiconductor switching elements fails and is fixed in a non-conducting (off) state, current still flows to the load side through the remaining semiconductor switching elements. Therefore, the failure of the semiconductor switching elements cannot be identified by simply detecting the presence or absence of current flowing to the load and the high / low of the output voltage.

[0013] Furthermore, in circuits where multiple semiconductor switching elements are connected in parallel, if any one of the semiconductor switching elements fails in the off state, an abnormally large current will surge violently through the remaining normal semiconductor switching elements due to the influence of the failed element. There is also a high probability that the normal switching elements will also fail due to excessive stress caused by the current and heat. Therefore, if the device remains unchanged while one semiconductor switching element in a circuit with multiple connected semiconductor switching elements fails, there is a high probability that the entire device will cease functioning.

[0014] For example, when electronic devices are installed in cars equipped with autonomous driving functions, they must be configured to ensure that no one of their functions completely stops due to the need for extremely high reliability. Summary of the Invention

[0015] In view of the above, this disclosure has been made, and the purpose of this disclosure is to provide a power control device and a semiconductor fault detection method that can correctly identify the presence or absence of a fault even when only a portion of the semiconductor switching elements in a circuit with multiple semiconductor switching elements connected in series and parallel fail.

[0016] To achieve the above objectives, the power control device according to this disclosure is characterized as follows. One aspect of a non-limiting embodiment of this disclosure relates to a power control device for detecting faults in semiconductor switching elements in a switching circuit, the switching circuit comprising a plurality of semiconductor series circuits connected in parallel with each other, and each of the semiconductor series circuits having a plurality of semiconductor switching elements connected in series with opposite polarities, the power control device comprising: a reference resistance value storage unit that pre-stores information of the combined resistance value between the input and output of the switching circuit in a reference state as a reference resistance value; and a current-current detection unit that detects the magnitude of the current flowing through the entire switching circuit as the current-current. The system includes: a potential difference detection unit that detects the potential difference between the input and output of the switching circuit as an input-output potential difference; a voltage drop calculation unit that calculates an assumed voltage drop based on the reference resistance value and the current detected by the current-carrying detection unit; a voltage comparison unit that compares the input-output potential difference detected by the potential difference detection unit with the assumed voltage drop calculated by the voltage drop calculation unit; and a fault identification unit that identifies the presence or absence of a fault in the semiconductor switching element based on the comparison result of the voltage comparison unit.

[0017] To achieve the above objectives, the semiconductor fault detection method according to this disclosure is characterized as follows. One aspect of a non-limiting embodiment of this disclosure relates to a semiconductor fault detection method for detecting faults in semiconductor switching elements in a switching circuit, the switching circuit comprising a plurality of semiconductor series circuits connected in parallel with each other, and each of the semiconductor series circuits having a plurality of semiconductor switching elements connected in series with opposite polarities. The semiconductor fault detection method includes: obtaining in advance a combined resistance value between the input and output of the switching circuit in a reference state as a reference resistance value; detecting the magnitude of the current flowing through the entire switching circuit as a current-carrying current; detecting the potential difference between the input and output of the switching circuit as an input-output potential difference; calculating an assumed voltage drop based on the reference resistance value and the detected current-carrying current; and identifying the presence or absence of a fault in the semiconductor switching element based on a comparison between the detected input-output potential difference and the assumed voltage drop.

[0018] According to the power control device and semiconductor fault detection method disclosed herein, in a circuit in which multiple semiconductor switching elements are connected in series and parallel, the presence or absence of a fault can be accurately identified even when only a portion of the semiconductor switching elements are faulty.

[0019] The present disclosure has been briefly described above. The details of the disclosure will be further elucidated by reading the aspects for implementing the disclosure described below with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a circuit diagram illustrating an example configuration of a semiconductor fault detection apparatus according to an embodiment of the present disclosure.

[0021] Figure 2 This is a flowchart illustrating an example of a fault determination process according to an embodiment of the present disclosure.

[0022] Figure 3 This is a circuit diagram illustrating an example of a switching circuit when a conduction fault occurs. Detailed Implementation

[0023] Specific embodiments according to this disclosure will be described with reference to the accompanying drawings. In the following description, an example of the power control device according to this disclosure being applied to a semiconductor fault detection device installed in a vehicle will be described; however, this disclosure is not limited to this example and can be applied to various power control devices, such as DC / DC converters, each having a switching function.

[0024] <Configuration of Semiconductor Fault Detection Device>

[0025] Figure 1 An example configuration of a semiconductor fault detection device 100 (power control device) according to an embodiment of the present disclosure is shown.

[0026] Figure 1 The semiconductor fault detection device 100 shown has the function of detecting faults in the semiconductor switching element contained in the switching circuit 10. The switching circuit 10 is installed in the vehicle and is used to supply power from the vehicle power supply to the vehicle-mounted devices (various electrical components) that are loads.

[0027] The input terminal 21 of the semiconductor fault detection device 100 is connected to the output of the vehicle power supply. The output terminal 22 is connected to the power input terminal of the vehicle device (not shown). Since the switching circuit 10 is used in a vehicle, there is a possibility that the input power may have the opposite polarity due to an incorrect power connection or that an excessively high power supply voltage may be input. The switching circuit 10 is designed so that it will not fail even under such incorrect connection conditions. In addition, redundancy is included in the switching circuit 10 to improve reliability.

[0028] Specifically, the switching circuit 10 includes six semiconductor switching elements FET1 to FET6. Each of the semiconductor switching elements FET1 to FET6 is a MOS field-effect transistor (FET) device. Note that... Figure 1 The “FET1-ON” to “FET6-ON” shown means that each of the semiconductor switching elements FET1 to FET6 is in the on (conductive) state.

[0029] exist Figure 1 In the switching circuit 10 shown, semiconductor switching elements FET1 and FET4 are connected in series with opposite polarities. That is, the drain terminal (D) of semiconductor switching element FET1 is connected to the input terminal 21, the source terminal (S) of semiconductor switching element FET1 and the source terminal of semiconductor switching element FET4 are connected to each other via conductive path 12, and the drain terminal of semiconductor switching element FET4 is connected to the output terminal 22. In other words, the two semiconductor switching elements FET1 and FET4 form a series circuit.

[0030] In the same manner as described above, two semiconductor switching elements FET2 and FET5 form a series circuit. Furthermore, two semiconductor switching elements FET3 and FET6 form a series circuit.

[0031] The series circuits of semiconductor switching elements FET1 and FET4, the series circuits of semiconductor switching elements FET2 and FET5, and the series circuits of semiconductor switching elements FET3 and FET6 are connected in parallel.

[0032] The gate terminals (G) of semiconductor switching elements FET1 and FET4 are connected to the common control line 11 via resistor 15, the gate terminals of semiconductor switching elements FET2 and FET5 are connected to the common control line 11 via resistor 16, and the gate terminals of semiconductor switching elements FET3 and FET6 are connected to the common control line 11 via resistor 17.

[0033] Therefore, by controlling the control signal SG1 applied to the common control line 11, semiconductor switching elements FET1 to FET6 can be simultaneously turned on and off. When the series circuit of semiconductor switching elements FET1 and FET4 is turned on, a conductive path is formed, allowing current to flow from the input terminal 21 through semiconductor switching element FET1, conductive path 12, and semiconductor switching element FET4 to the output terminal 22. When the series circuit is turned off, no current flows through the aforementioned conductive path.

[0034] In the same manner as described above, when the series circuit of semiconductor switching elements FET2 and FET5 is turned on, a conductive path is formed, so that current flows from the input terminal 21 through semiconductor switching element FET2, conductive path 13 and semiconductor switching element FET5 to the output terminal 22.

[0035] When the series circuit is broken, no current flows through the above conductive path.

[0036] In the same manner as described above, when the series circuit of semiconductor switching elements FET3 and FET6 is turned on, a conductive path is formed, so that current flows from the input terminal 21 through semiconductor switching element FET3, conductive path 14 and semiconductor switching element FET6 to the output terminal 22.

[0037] When the series circuit is broken, no current flows through the above conductive path.

[0038] Since the control inputs of the three series circuits are all connected to the common control line 11, the three series circuits usually switch to the same ON / OFF state simultaneously according to the control signal SG1.

[0039] Therefore, the current I flowing from the input terminal 21 to the output terminal 22 through the switching circuit 10 is divided inside the switching circuit 10. The divided currents flow through three series circuits respectively, merge on the downstream side, and the merged current flows through the path to the output terminal 22.

[0040] Incidentally, there is a possibility that any of the semiconductor switching elements FET1 to FET6 in the switching circuit 10 may fail. Figure 1 The “turn-off fault” of the semiconductor switching element FET2 shown refers to the following state: the semiconductor switching element FET2 is fixed to the turn-off state due to a fault and a fault occurs in which the semiconductor switching element FET2 is not switched to the turn-on state.

[0041] like Figure 1 As shown, when the semiconductor switching element FET2 is in a "turn-off fault" state, a fault condition occurs when the control signal SG1 switches to the on state. In this state, current flows through conductive paths 12 and 14, but current does not flow through conductive path 13. However, even in this fault state, the load connected to the output terminal 22 can still function normally because the current I flows through conductive paths 12 and 14.

[0042] However, since current does not flow through conductive path 13, a larger current flows more strongly through the semiconductor switching elements FET1, FET3, FET4, and FET6 in paths 12 and 14, which are not connected to conductive path 13. As a result, stress due to excessive current and heat is applied to the semiconductor switching elements FET1, FET3, FET4, and FET6, making them more prone to failure than under normal conditions.

[0043] Therefore, a fault must be detected inside the switching circuit 10 before the semiconductor switching elements FET1, FET3, FET4, and FET6, which have not yet failed, fail and the function of the switching circuit 10 completely stops.

[0044] However, in Figure 1 In the switch circuit 10 shown, a pair of semiconductor switching elements are connected in series with opposite polarities, and three series circuits are connected in parallel. Therefore, a fault cannot be detected by conventional methods. For example, with only one series circuit, it is easy to identify whether the switch circuit is working properly by simply comparing the high / low voltage of the conductive path 13 with the high / low voltage of the control signal SG1. However, since the three series circuits are connected in parallel, the voltage of the conductive path 13 is not significantly different from the voltage when no fault has occurred, and a fault cannot be detected.

[0045] Therefore, in Figure 1 In the semiconductor fault detection device 100 shown, the microcomputer 40 detects "turn-off faults" of semiconductor switching elements such as FET2 by performing special processing described later.

[0046] like Figure 1 As shown, a resistor Ri for current sensing is connected between the output and output terminal 22 of the switching circuit 10. Resistor Ri has a very small resistance value, such that it has almost no effect on the current I. Furthermore, the voltage drop, represented by the product of the resistance value and the current I, occurs between the two ends of resistor Ri.

[0047] Meanwhile, the two inputs of the current detection circuit 31 are respectively connected to the two ends of the resistor Ri. Therefore, the current detection circuit 31 can output the voltage obtained by amplifying the potential difference between the two ends of the resistor Ri as a current signal SGi. That is, the information represented by the voltage of the current signal SGi corresponds to the current I.

[0048] The two inputs of the potential difference detection circuit 32 are connected to the input side and the output side of the switching circuit 10, respectively. Therefore, the potential difference detection circuit 32 can amplify the signal representing the potential difference between the input and output of the switching circuit 10, and output the amplified signal as a voltage signal SGv.

[0049] Meanwhile, the temperature detection circuit 33 includes a temperature sensor that detects the temperature near the switching circuit 10. For example, the temperature near the switching circuit 10 can be detected by mounting the temperature sensor of the temperature detection circuit 33 on a heat sink or the like that promotes heat dissipation of the semiconductor switching elements FET1 to FET6. For example, a thermistor can be used as the temperature sensor. The temperature detection circuit 33 outputs a temperature signal SGt indicating the temperature near the switching circuit 10.

[0050] The microcomputer 40 includes analog input ports P1, P2, and P3, an output port P4, and a communication port P5. Analog input port P1 of the microcomputer 40 is connected to the output of the temperature detection circuit 33. Analog input port P2 of the microcomputer 40 is connected to the output of the current detection circuit 31, and analog input port P3 is connected to the output of the potential difference detection circuit 32. The output port P4 of the microcomputer 40 is connected to the input of the gate driver 24. The communication port P5 is connected to an external device 50 via a communication line.

[0051] The microcomputer 40 pre-stores the control program necessary to implement the functions of the semiconductor fault detection device 100. A non-volatile memory 41 is incorporated into the microcomputer 40. The non-volatile memory 41 pre-stores constant data required for fault detection.

[0052] The microcomputer 40 can sequentially sample the analog levels (voltages) of the signals input to the analog input ports P1 to P3, and convert the analog levels into digital signals. Therefore, the microcomputer 40 can acquire temperature information corresponding to the analog level of the temperature signal SGt, information about the current I corresponding to the analog level of the current signal SGi, and information about the potential difference corresponding to the analog level of the voltage signal SGv.

[0053] The microcomputer 40 can output a control signal SG1 as a binary signal from the output port P4. The control signal SG1 is provided to the control input terminal 23 of the switching circuit 10 via the gate driver 24. Therefore, the microcomputer 40 can switch the switching circuit 10 on / off by turning the control signal SG1 on / off.

[0054] The microcomputer 40 can communicate with the external device 50 via the communication port P5 to input and output various information. For example, when a device malfunction occurs inside the switching circuit 10, it can notify the external device 50 of information indicating the malfunction.

[0055] <Fault Diagnosis and Handling>

[0056] Figure 2An example of fault determination processing according to embodiments of the present disclosure is shown. That is, when in Figure 1 The microcomputer 40 shown executes... Figure 2 When the fault determination and processing procedure shown is executed, it is able to detect a "turn-off fault" in each of the semiconductor switching elements FET1 to FET6 of the switching circuit 10. Figure 2 The process shown is executed repeatedly periodically. The following will describe... Figure 2 Fault diagnosis and handling in the process.

[0057] The microcomputer 40 samples the current signal SGi to obtain information about the latest energized current I (S11).

[0058] The microcomputer 40 samples the temperature signal SGt to obtain the latest temperature T1 information (S12).

[0059] The microcomputer 40 samples the voltage signal SGv to obtain information about the latest potential difference ΔV (S13). The potential difference ΔV is the difference between the voltage Vin[V] on the input side and the voltage Vout[V] on the output side of the switching circuit 10.

[0060] Meanwhile, the non-volatile memory 41 in the microcomputer 40 includes Figure 2 The table TB1 shows the combined resistance values. Each data point stored in the table TB1 represents a reference value (reference resistance value Rref) for the combined resistance of the entire circuit between the input side (input terminal 21) and the output side of the switching circuit 10 when all semiconductor switching elements FET1 to FET6 are in the on-state. These data points correspond to values ​​obtained through actual measurement, for example, under standard operating conditions of all semiconductor switching elements FET1 to FET6, or equivalent values. The combined resistance values ​​corresponding to each of the various variations of temperature T1 in the switching circuit 10 and the combined resistance values ​​corresponding to each of the various variations of potential difference ΔV are predetermined and recorded in the table TB1.

[0061] The microcomputer 40 substitutes the temperature T1 obtained in S12 and the potential difference ΔV obtained in S13 into the synthesized resistance value table TB1, and obtains the appropriate reference resistance value Rref associated with T1 and ΔV (S14).

[0062] The microcomputer 40 calculates the assumed potential difference between the input and output terminals of the switching circuit 10 as the assumed voltage drop Vdrop (S15) when the semiconductor switching elements FET1 to FET6 in the switching circuit 10 are working normally (all are in the on state). The assumed voltage drop Vdrop is calculated by the following equation.

[0063] Vdrop=Rref×I·····(1)

[0064] The microcomputer 40 calculates the voltage error Ve using the following equation (S16) and compares the voltage error Ve with the voltage threshold Vth (S17). For the voltage threshold Vth, a predetermined constant is recorded in the non-volatile memory 41 and used.

[0065] Ve=ΔV-Vdrop·····(2)

[0066] Microcomputer 40 progresses from S17 to S18 when “Ve≤Vth”, and from S17 to S19 when “Ve>Vth”.

[0067] In other words, when the actual potential difference ΔV detected in S13 is equal to the assumed voltage drop Vdrop (Ve≤Vth) calculated based on the reference resistance value Rref, the combined resistance value between the input and output of the switching circuit 10 is equal to the combined resistance value under standard conditions. Therefore, in this case, the microcomputer 40 identifies that all semiconductor switching elements FET1 to FET6 are normal (S18).

[0068] When the actual potential difference ΔV detected in S13 is too large compared to the assumed voltage drop Vdrop (Ve>Vth), the microcomputer 40 identifies a "turn-off fault" in any of the semiconductor switching elements FET1 to FET6 (S19). In this case, the microcomputer 40 also performs predetermined fault control to facilitate fault handling (S20).

[0069] As a specific fault control measure, the microcomputer 40 controls the control signal SG1 to cut off... Figure 1 The switching circuit 10 shown is turned on, or switched from on / off control to pulse width modulation (PWM) control, thereby suppressing the current I flowing through the switching circuit 10. Furthermore, the microcomputer 40 notifies the external device 50 of a malfunction in the switching circuit 10 via communication signal SG2.

[0070] Even when a fault exists within the switching circuit 10, the switching circuit 10 itself still functions normally due to its redundancy. However, for example, when semiconductor switching element FET2 remains in a "shutdown fault" state, additional stress is applied to the remaining normal semiconductor switching elements FET1, FET3, FET4, and FET6. In either case, the possibility of the switching circuit 10 completely ceasing to function is high.

[0071] Therefore, the switching circuit 10 is switched off by fault control, or the current I is suppressed by PWM control or the like. This control reduces the stress on the remaining normal semiconductor switching elements and extends the time before the switching circuit 10 stops functioning. Furthermore, by notifying external devices such as the 50 of the fault occurrence through fault control, vehicle users can be prompted to repair the fault in the switching circuit 10 as soon as possible to ensure safety.

[0072] <Fault Detection>

[0073] Figure 3 An example of the switching circuit 10 in the event of a conduction failure is shown. Figure 3 In the example shown, it is assumed that the "conduction failure" occurs in semiconductor switching element FET2, and that semiconductor switching elements FET1, FET3, FET4, FET5, and FET6, other than semiconductor switching element FET2, are in a normal state. A "conduction failure" refers to the inability to switch to a shutdown state when the semiconductor switching element FET2 is in a normal conduction state.

[0074] When the control signal SG1 applied to the common control input terminal 23 becomes off, initially, all semiconductor switching elements FET1 to FET6 are turned off, and therefore the entire circuit should be disconnected and the current I should be 0. However, in Figure 3 In the example, since the "conduction failure" occurs in the semiconductor switching element FET2, the current I flows even when the control signal SG1 is off due to the current flowing through the conductive path 13.

[0075] Therefore, it is easy to detect, such as Figure 3 The example shown illustrates a "conduction failure." For instance, microcomputer 40 monitors the voltage of each conductive path 12 to 14 and identifies whether the switching circuit is functioning correctly simply by comparing the high / low voltage with the on / off state of control signal SG1. That is, in Figure 3 In the example, when the control signal SG1 is off, the voltages of conductive paths 12, 13, and 14 become "low", "high", and "low" respectively, thus indicating that a "conduction fault" has occurred in the semiconductor switching element FET2.

[0076] <Modular Examples of Semiconductor Fault Detection Devices>

[0077] exist Figure 2In the fault determination process shown, it is assumed that the effects of the actual temperature T1 and the potential difference ΔV are taken into account. The synthesized resistance value table TB1 stores a large number of corrected reference resistance values ​​Rref in advance, and can be corrected by calculation. For example, a reference resistance value Rref can be appropriately corrected according to the characteristics of the synthesized resistance value in the actual switching circuit 10 by using a temperature correction value obtained by using a predetermined function with temperature T1 as a variable and a potential difference correction value obtained by using the potential difference ΔV as another function as a variable.

[0078] <Advantages and Effects of Semiconductor Fault Detection Devices>

[0079] exist Figure 1 The semiconductor fault detection device 100 shown can easily identify the presence or absence of a semiconductor switching element that has experienced a "turn-off fault" in the switching circuit 10. In the switching circuit 10, multiple series circuits are connected in parallel, and each series circuit has multiple semiconductor switching elements connected with opposite polarities. Figure 1 In the example, a "shutdown fault" was identified in FET2.

[0080] Additionally, when executing Figure 2 The fault determination shown uses a reference resistance value Rref, corrected based on the actual temperature T1 and potential difference ΔV, to calculate the assumed voltage drop Vdrop, thus easily improving the accuracy of fault determination.

[0081] Furthermore, when a "turn-off fault" is detected in the semiconductor switching element, fault control is performed in S20, which reduces excessive pressure applied to the normal semiconductor switching element and prevents the further development of the fault in the switching circuit 10. In addition, it prompts the user to repair the fault early and ensures safety.

[0082] <Supplementary Notes>

[0083] Hereinafter, the features of the embodiments of the power control device and semiconductor fault detection method according to the present disclosure are briefly summarized in [1] to [5].

[0084] [1] A power control device (semiconductor fault detection device 100) for detecting faults in semiconductor switching elements in a switching circuit (10), the switching circuit (10) comprising a plurality of semiconductor series circuits connected in parallel with each other, and each of the semiconductor series circuits having a plurality of semiconductor switching elements (FET1 to FET6) connected in series with opposite polarities, the power control device (semiconductor fault detection device 100) comprising:

[0085] A reference resistance value storage unit, which pre-stores information (synthetic resistance value table TB1) of the combined resistance value between the input and output of the switching circuit in a reference state as a reference resistance value (Rref);

[0086] A current detection unit (microcomputer 40, S11) is configured to detect the magnitude of the current flowing through the entire switching circuit as the current (I).

[0087] A potential difference detection unit (microcomputer 40, S13) is configured to detect the potential difference between the input and the output of the switching circuit as an input-output potential difference;

[0088] A voltage drop calculation unit (microcomputer 40, S15) is configured to calculate an assumed voltage drop (Vdrop) based on the reference resistance value and the current detected by the current detection unit.

[0089] A voltage comparison unit (microcomputer 40, S16, S17) is configured to compare the input-output potential difference detected by the potential difference detection unit with the assumed voltage drop calculated by the voltage drop calculation unit; and

[0090] A fault identification unit (microcomputer 40, S18, S19) is configured to identify the presence or absence of a fault in the semiconductor switching element based on the comparison result of the voltage comparison unit.

[0091] According to the power control device with the configuration described above [1], a reference resistance value can be obtained from the reference resistance value storage unit as known information. Therefore, the voltage drop calculation unit can calculate the assumed voltage drop expected to occur between the input and output of the switching circuit in the reference state (i.e., in the normal state) based on the reference resistance value and the detected current. In addition, when there is a large difference between the comparison result performed by the voltage comparison unit and the calculated assumed voltage drop, since the difference in the result is different from the difference in the reference state, it can be considered that an abnormality has occurred in one or more semiconductor switching elements. Therefore, the fault identification unit can identify the presence or absence of a fault in the semiconductor switching element based on the comparison result of the voltage comparison unit.

[0092] [2] The power control device according to [1] above further includes:

[0093] A temperature detection unit (temperature detection circuit 33) configured to detect the temperature (T1) near the switching circuit; and

[0094] A temperature correction unit (microcomputer 40, S14) is configured to correct the reference resistance value based on the temperature detected by the temperature detection unit.

[0095] According to the power control device with the configuration described above [2], fault detection can be performed with higher accuracy because the effects of temperature changes can be corrected before it can be performed. That is, because the resistance value between the input and output terminals of the semiconductor switching element changes due to the influence of ambient temperature, a difference corresponding to the temperature change occurs between the reference resistance value of the semiconductor switching element specified in the reference state and the actual resistance value. By correcting the effect of this difference, accurate fault detection can be performed.

[0096] [3] The power control device according to [1] or [2] further includes:

[0097] A voltage correction unit (microcomputer 40, S14) is configured to correct the reference resistance value based on the input-output potential difference (ΔV) detected by the potential difference detection unit.

[0098] According to the power control device with the configuration described above [3], fault detection can be performed with higher accuracy because the influence of the input-output potential difference change can be corrected before it can be performed. That is, since the resistance value between the input terminal and the output terminal of the semiconductor switching element changes according to the potential difference between the input terminal and the output terminal, a difference corresponding to the difference in potential difference occurs between the reference resistance value of the semiconductor switching element specified in the reference state and the actual resistance value. By correcting the influence of this difference, accurate fault detection can be performed.

[0099] [4] The power control device according to any one of [1] to [3],

[0100] When the fault identification unit detects a fault in the semiconductor switching element, the fault identification unit performs fault control (S20), which includes at least one of abnormal detection notification of a predetermined external device and operation suppression of the switching circuit.

[0101] According to the power control device with the above configuration [4], when a fault occurs in the semiconductor switching element, an abnormality detection notification is executed through fault control, thus attracting the user's attention to repair the fault before a more serious fault occurs. In addition, since the operation of the switching circuit is suppressed by fault control, the stress caused by excessive current and heat applied to the remaining semiconductor switching elements that have not yet failed can be reduced, and the time margin is increased before the entire device completely fails.

[0102] [5] A semiconductor fault detection method for detecting faults in semiconductor switching elements in a switching circuit (10), the switching circuit (10) comprising a plurality of semiconductor series circuits connected in parallel with each other, and each of the semiconductor series circuits having a plurality of semiconductor switching elements (FET1 to FET6) connected in series with opposite polarities, the semiconductor fault detection method comprising:

[0103] The combined resistance value between the input and output of the switching circuit in the reference state (combined resistance value table TB1) is obtained in advance as the reference resistance value (Rref);

[0104] The magnitude of the current flowing through the entire switching circuit is detected as the current-carrying current (I) (S11);

[0105] The potential difference between the input and the output of the switching circuit is detected as the input-output potential difference (ΔV) (S13);

[0106] The assumed voltage drop (Vdrop) is calculated based on the reference resistance value and the detected current (S15);

[0107] The presence or absence of a fault in the semiconductor switching element is identified based on the comparison between the detected input-output potential difference and the assumed voltage drop (S16 to S19).

[0108] [6] The semiconductor fault detection method according to [5] further includes:

[0109] Detecting the temperature near the switching circuit; and

[0110] The reference resistance value is corrected based on the detected temperature.

[0111] [7] The semiconductor fault detection method according to [5] or [6] further includes:

[0112] The reference resistance value is corrected based on the detected input-output potential difference (ΔV).

[0113] [8] The semiconductor fault detection method according to any one of [5] to [7] further includes:

[0114] If a fault is detected in the semiconductor switching element, fault control (S20) is performed, which includes at least one of abnormal detection notification of a predetermined external device and operation suppression of the switching circuit.

[0115] According to the semiconductor fault detection method described above [5], since a reference resistance value is obtained in advance, the reference resistance value can be processed as known information. Therefore, it is possible to calculate the assumed voltage drop between the input and output of the switching circuit expected in the reference state (i.e., in the normal state) based on the reference resistance value and the detected current. In addition, when there is a large difference between the comparison result of the input-output potential difference detected by actual measurement and the assumed voltage drop obtained by calculation, since the difference in the result is different from the difference in the reference state, it can be considered that an anomaly has occurred in one or more semiconductor switching elements.

Claims

1. A power control device for detecting faults in semiconductor switching elements in a switching circuit, the switching circuit comprising a plurality of semiconductor series circuits connected in parallel with each other, and each of the semiconductor series circuits having a plurality of semiconductor switching elements connected in series with opposite polarities, the power control device comprising: A reference resistance value storage unit pre-stores information about the combined resistance value between the input and output of the switching circuit in a reference state as a reference resistance value for the combined resistance value of the entire circuit between the input and output sides of the switching circuit in an on state where all the semiconductor switching elements are turned on. A current-carrying detection unit is configured to detect the magnitude of the current flowing through the entire switching circuit as the current-carrying current. A potential difference detection unit is configured to detect the potential difference between the input and the output of the switching circuit as an input-output potential difference; A voltage drop calculation unit is configured to calculate an assumed voltage drop based on the reference resistance value and the current detected by the current detection unit. A voltage comparison unit is configured to compare the input-output potential difference detected by the potential difference detection unit with the assumed voltage drop calculated by the voltage drop calculation unit; as well as A fault identification unit is configured to identify the presence or absence of a fault in the semiconductor switching element based on the comparison result of the voltage comparison unit.

2. The power control device according to claim 1, further comprising: A temperature detection unit configured to detect the temperature near the switching circuit; as well as A temperature correction unit is configured to correct the reference resistance value based on the temperature detected by the temperature detection unit.

3. The power control device according to claim 1 or 2, further comprising: A voltage correction unit is configured to correct the reference resistance value based on the input-output potential difference detected by the potential difference detection unit.

4. The power control device according to claim 1 or 2, in, When the fault identification unit detects a fault in the semiconductor switching element, the fault identification unit performs fault control, which includes at least one of abnormal detection notification of a predetermined external device and operation suppression of the switching circuit.

5. The power control device according to claim 3, in, When the fault identification unit detects a fault in the semiconductor switching element, the fault identification unit performs fault control, which includes at least one of abnormal detection notification of a predetermined external device and operation suppression of the switching circuit.

6. A semiconductor fault detection method for detecting faults in semiconductor switching elements in a switching circuit, the switching circuit comprising a plurality of semiconductor series circuits connected in parallel with each other, and each of the semiconductor series circuits having a plurality of semiconductor switching elements connected in series with opposite polarities, the semiconductor fault detection method comprising: The combined resistance value between the input and output of the switching circuit in the reference state is obtained in advance as the reference resistance value of the combined resistance value of the entire circuit between the input side and the output side of the switching circuit in the conduction state where all the semiconductor switching elements are turned on. The magnitude of the current flowing through the entire switching circuit is used as the energizing current. The potential difference between the input and the output of the switching circuit is detected as the input-output potential difference; The assumed voltage drop is calculated based on the reference resistance value and the detected current. The presence or absence of a fault in the semiconductor switching element is identified based on the comparison between the detected input-output potential difference and the assumed voltage drop.

7. The semiconductor fault detection method according to claim 6 further includes: Detect the temperature near the switching circuit; as well as The reference resistance value is corrected based on the detected temperature.

8. The semiconductor fault detection method according to claim 6 or 7, further comprising: The reference resistance value is corrected based on the detected input-output potential difference.

9. The semiconductor fault detection method according to claim 6 or 7, further comprising: If a fault is detected in the semiconductor switching element, fault control is performed, which includes at least one of abnormal detection notification of a predetermined external device and operation suppression of the switching circuit.

10. The semiconductor fault detection method according to claim 8, further comprising: If a fault is detected in the semiconductor switching element, fault control is performed, which includes at least one of abnormal detection notification of a predetermined external device and operation suppression of the switching circuit.

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