Driving circuit

Abstract

To provide a driving circuit of which determination accuracy of a gate leak current is improved.SOLUTION: A driving circuit 1 drives a switching element 110. The driving circuit 1 comprises: an upper arm switch 20 and a gate resistance 30 as an on-switch circuit; and a lower arm switch 40 and a gate resistance 50 as an off-switch circuit. In addition, the driving circuit 1 comprises a leakage current determination circuit 70a that is connected to a gate terminal 110g of the switching element and determines if leak current is generated in the switching element. The leakage current determination circuit contains a current source 71 that is connected in parallel to the on-switch circuit, and generates a monitor voltage for determining a leak current, and determines the occurrence of the leak current in the case where the monitor voltage is a threshold value or larger.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a drive circuit. [Background technology]

[0002] One example of a driving circuit is a semiconductor device disclosed in Patent Document 1. The semiconductor device includes a gate leakage detection circuit that detects gate leakage of a semiconductor element. The gate leakage detection circuit detects gate leakage based on a potential difference generated across a gate resistor connected to the gate of the semiconductor element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-71174 A Summary of the Invention [Problem to be solved by the invention]

[0004] The semiconductor device judges the gate leakage based on the potential difference generated at both ends of the gate resistor. Therefore, it is considered that the semiconductor device lowers the resistance value of the gate resistor in order to reduce the loss of the semiconductor element. However, there is a risk that the semiconductor device will lower the accuracy of the gate leakage judgment by lowering the resistance value of the gate resistor.

[0005] One disclosed object is to provide a drive circuit with improved accuracy in determining a gate leakage current. [Means for solving the problem]

[0006] The drive circuit disclosed herein comprises: A drive circuit for driving a switching element (110), an on-switch circuit (20, 30) connected to a gate terminal of the switching element for turning on the switching element; an off switch circuit (40, 50) connected to the gate terminal and driving the switching element to an off state; a determination circuit (70a to 70g) connected to the gate terminal and determining whether or not a gate leakage current is occurring in the switching element; The judgment circuit includes a generation circuit connected in parallel to the on switch circuit or the off switch circuit and generating a judgment voltage for judging the gate leakage current, and is characterized in that it judges that a gate leakage current is occurring when the judgment voltage is equal to or greater than a threshold value.

[0007] In this manner, in the drive circuit, the generation circuit for generating a determination voltage for determining the gate leakage current of the gate terminal is connected in parallel with the on switch circuit or the off switch circuit, so that the drive circuit can determine the occurrence of the gate leakage current without affecting the switching speed of the on switch circuit or the off switch circuit.

[0008] The aspects disclosed in this specification adopt different technical means to achieve their respective objectives. The claims and the parenthetical symbols described in this section are illustrative of the corresponding relationship with the embodiments described below, and are not intended to limit the technical scope. The objectives, features, and effects disclosed in this specification will become clearer by referring to the following detailed description and the attached drawings. [Brief description of the drawings]

[0009] [Figure 1] 2 is a diagram showing a schematic configuration of a drive circuit in the first embodiment. [Diagram 2] 5 is a flowchart showing the operation of the drive circuit in the first embodiment. [Diagram 3] 4 is a time chart showing the operation of the drive circuit in the first embodiment. [Figure 4] 13 is a diagram showing a schematic configuration of a drive circuit according to a second embodiment. [Diagram 5]10 is a time chart showing the operation of the drive circuit in the second embodiment. [Figure 6] 13 is a diagram showing a schematic configuration of a drive circuit according to a third embodiment. [Figure 7] 13 is a time chart showing the operation of the drive circuit in the third embodiment. [Figure 8] 13 is a diagram showing a schematic configuration of a drive circuit according to a fourth embodiment. [Figure 9] 13 is a time chart showing the operation of a drive circuit in the fourth embodiment. [Figure 10] 13 is a diagram showing a schematic configuration of a drive circuit according to a fifth embodiment. [Figure 11] 13 is a diagram showing a schematic configuration of a drive circuit in a sixth embodiment. [Figure 12] 13 is a diagram showing a schematic configuration of a drive circuit according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, several embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, the same reference numerals may be used to designate parts corresponding to matters described in the preceding embodiment, and duplicated descriptions may be omitted. In each embodiment, when only a part of the configuration is described, the other parts of the configuration may be applied by referring to the other embodiment described previously.

[0011] (First embodiment) 1 to 3, a drive circuit 1 of the first embodiment will be described. The drive circuit 1 is a circuit that drives a switching element 110. The drive circuit 1 applies a gate voltage Vcc to a gate terminal 110g of the switching element 110 to drive the switching element 110.

[0012] In this embodiment, a switching element 110 provided in an inverter circuit 100 is used as an example of a driven object. The inverter circuit 100 is mounted on a vehicle or the like. The inverter circuit 100 operates to supply power to a load device such as a rotating electric machine mounted on the vehicle. Thus, the drive circuit 1 is configured so as to be mountable on the vehicle together with the inverter circuit 100. The inverter circuit 100 corresponds to a power conversion device. The rotating electric machine is used as a drive source for the vehicle or the like.

[0013] The inverter circuit 100 includes a plurality of switching elements 110. However, in the drawings, one switching element 110 is illustrated. In this embodiment, an N-channel MOSFET is used as an example of the switching element 110. However, the present disclosure is not limited to this, and an IGBT can also be used as the switching element 110. In other words, any switching element having a gate terminal can be used as the driving target. The driving circuit 1 is provided corresponding to one switching element 110.

[0014] However, the switching element 110 may be provided outside the power conversion device. The power conversion device may include the drive circuit 1 and the inverter circuit 100.

[0015] <Drive circuit configuration> As shown in FIG. 1, the drive circuit 1 includes a control IC 10, an upper arm switch 20, a gate resistor 30, a lower arm switch 40, a gate resistor 50, a voltage source 61, a leakage current determination circuit 70a, and the like.

[0016] The control IC 10 is connected to the gate terminal 20g of the upper arm switch 20 and the gate terminal 50g of the lower arm switch 40. The control IC 10 is also connected to the gate terminal 72g of the change-over switch 72 and the output terminal of the comparator 73. The control IC 10 controls the on / off of the upper arm switch 20, the lower arm switch 40 and the change-over switch 72. The control IC 10 switches between enabling and disabling the leakage current determination circuit 70a, for example, by controlling the change-over switch 72. The control IC 10 also receives an output signal from the comparator 70. The control IC 10 corresponds to a control unit.

[0017] The upper arm switch 20 has a source terminal connected to a voltage source 61, a drain terminal connected to a gate resistor 30, and a gate terminal 20g connected to a control IC 10. Here, a P-channel MOSFET is used as an example of the upper arm switch 20. One terminal of the gate resistor 30 is connected to the drain terminal of the upper arm switch 20. The other terminal of the gate resistor 30 is connected to a gate terminal 110g. The upper arm switch 20 and the gate resistor 30 are a circuit for turning on the switching element 110. The upper arm switch 20 and the gate resistor 30 correspond to an on switch circuit. The voltage source 61 can also be said to be a gate voltage source that supplies a gate voltage Vcc to the gate terminal 110g.

[0018] The lower arm switch 40 has a source terminal connected to ground, a drain terminal connected to the gate resistor 50, and a gate terminal 40g connected to the control IC 10. Here, an N-channel MOSFET is used as an example of the lower arm switch 40. One terminal of the gate resistor 50 is connected to the drain terminal of the lower arm switch 40. The other terminal of the gate resistor 50 is connected to the gate terminal 110g. The lower arm switch 40 and the gate resistor 50 form a circuit for driving the switching element 110 to the off state. The lower arm switch 40 and the gate resistor 50 correspond to an off switch circuit.

[0019] The leakage current determination circuit 70a is connected to the gate terminal 110g and determines whether or not a gate leakage current occurs at the gate terminal 110g of the switching element 110. The leakage current determination circuit 70a corresponds to a determination circuit. Hereinafter, the gate leakage current is also simply referred to as a leakage current. The leakage current is a current that flows from the gate terminal 110g to the source terminal as shown by the dashed dotted line in FIG. 1. Note that whether or not a leakage current occurs can be rephrased as whether or not there is a leakage current, whether or not a leakage current flows, etc.

[0020] The leakage current determination circuit 70a includes a current source 71, a changeover switch 72, and a comparator 73. The current source 71 is connected to the voltage source 61 and the source terminal of the changeover switch 72. It can be said that the current source 71 is connected to the gate terminal 110g via the changeover switch 72. The current source 71 is also connected in parallel to the on-switch circuit.

[0021] The current source 71 is for generating a monitor voltage for determining a gate leakage current of the gate terminal 110g. The current source 71 passes a current through the gate terminal 110g when the changeover switch 72 is in an enabled state. The current source 71 corresponds to a generating circuit. The monitor voltage corresponds to a determination voltage.

[0022] The current source 71 can be considered as a circuit that creates a potential difference (monitor voltage) to improve the detection accuracy of the leakage current. The current source 71 can also be considered as a circuit that generates a monitor voltage that changes when a leakage current occurs. The monitor voltage can also be considered as a voltage that correlates with the gate terminal voltage of the gate terminal 110g.

[0023] The changeover switch 72 has a source terminal connected to the current source 71, a drain terminal connected to the gate terminal 110g, and a gate terminal 72g connected to the control IC 10. Here, a P-channel MOSFET is used as an example of the changeover switch 72. The changeover switch 72 is connected in parallel with the on switch circuit. The changeover switch 72 is a switch that switches between enabling and disabling the leakage current determination circuit 70a. The changeover switch 72 can also be considered as part of the generation circuit.

[0024] In this embodiment, as an example, the current source 71 and the changeover switch 72 connected in parallel to the on switch circuit are used. However, the present disclosure is not limited to this, and the current source 71 and the changeover switch 72 connected in parallel to the off switch circuit may also be used.

[0025] The comparator 73 compares the monitor voltage with a threshold value and outputs the comparison result. An output terminal of the comparator 73 is connected to the control IC 10. One input terminal of the comparator 73 is connected to the gate terminal 110g and the drain terminal of the change-over switch 72. The monitor voltage is input to one input terminal of the comparator 73. The threshold value is a voltage threshold value for determining whether or not a leak current flows through the gate terminal 110g.

[0026] When the monitor voltage is equal to or greater than the threshold, the comparator 73 outputs a leak signal to the control IC 10 indicating that it has been determined that a leak current is occurring. That is, the comparator 73 outputs the leak signal as an output signal. The leak signal can also be considered a leak current flag. The leak signal can also be considered a signal indicating that a leak current is occurring. When the monitor voltage is equal to or greater than the threshold, the comparator 73 outputs Hi (1) as the leak signal. On the other hand, when the monitor voltage is smaller than the threshold, the comparator 73 outputs Lo (0) as a normal signal indicating that no leak current is occurring.

[0027] The leakage current determination circuit 70a can be said to include a generation circuit that generates a monitor voltage and is provided separately from the on switch circuit and the off switch circuit. The leakage current determination circuit 70a can also be said to be a circuit that determines the leakage current without using the gate resistors 30 and 50.

[0028] The comparator 73 may be included in the control IC 10. In this case, the control IC 10 judges whether or not a leak current is occurring. That is, a monitor voltage is input to the control IC 10. Then, the control IC 10 compares the monitor voltage with a threshold value, and judges that a leak current is occurring if the monitor voltage is equal to or greater than the threshold value. Therefore, it can be said that the control IC 10 includes a part of a judgment circuit.

[0029] <Drive circuit operation> The operation of the drive circuit 1 will be described with reference to Figures 2 and 3. The solid line in Figure 3 shows the monitor voltage when no leakage current occurs, while the dashed and dotted line shows the monitor voltage when leakage current occurs.

[0030] The control IC 10 starts operating when the vehicle ignition switch (IG) is turned on. Once the control IC 10 starts operating, it continues operating until the inverter is stopped. In other words, the control IC 10 starts the flowchart shown in FIG. 2 when the IG is turned on.

[0031] The control IC 10 executes step S10 with the IG on. In step S10, it is determined whether or not there is a leak current. Step S10 is an initial process that is performed before the operation of the inverter circuit 100 starts (S11). Therefore, the control IC 10 determines whether or not there is a leak current as the initial process.

[0032] The control IC 10 controls the change-over switch 72 to determine the presence or absence of leakage current. That is, the control IC 10 switches the leakage current determination circuit 70a from disabled to enabled by the change-over switch 72. It is preferable that the control IC 10 controls the change-over switch 72 to enable the leakage current determination circuit 70a in a stopped state where the gate terminal 110g is equal to or lower than the on-threshold value. The control IC 10 switches the leakage current determination circuit 70a to enabled, for example, at timing t1 in FIG. 3.

[0033] As a result, the current source 71 passes a current through the gate terminal 110g. The monitor voltage is input to the input terminal of the comparator 73. The comparator 73 outputs a leak signal when the monitor voltage is equal to or higher than the threshold. As shown in FIG. 3, the comparator 73 outputs the leak signal at timing t2. The comparator 73 also outputs a normal signal when the monitor voltage is lower than the threshold.

[0034] The control IC 10 receives the output signal of the comparator 73. If the control IC 10 receives a leak signal as the output signal, it determines that there is a leak current and proceeds to step S13. If the control IC 10 receives a normal signal as the output signal, it determines that there is no leak current and proceeds to step S11.

[0035] The flow of leakage current may be a sign of a failure in the switching element 110. In other words, it may be considered that there is a possibility that the gate terminal 110g of the switching element 110 may fail. Therefore, when the control IC 10 determines that there is a leakage current, it may determine that this is a sign of a failure in the switching element 110.

[0036] In step S11, the control IC 10 starts the operation of the inverter circuit 100 and operates the inverter circuit 100 to supply power to the load device. At this time, the control IC 10 operates the inverter circuit 100 by controlling the on switch circuit and the off switch circuit.

[0037] In step S12, it is determined whether the inverter is stopped. The control IC 10 determines whether the inverter is stopped based on a signal from, for example, a higher-level ECU. If the control IC 10 does not determine that the inverter is stopped, it repeats step S12. If the control IC 10 determines that the inverter is stopped, it ends the flowchart of FIG. 2.

[0038] In step S13, an abnormality notification is performed. The control IC 10 performs the abnormality notification when it determines that the abnormality is a sign of a failure in the switching element 110. The control IC 10 performs the abnormality notification to the user. In this case, the control IC 10 may perform the abnormality notification via a higher-level ECU or the like.

[0039] Furthermore, the control IC 10 may notify the abnormality so that it can be detected by inspection at a dealer, a factory, etc. In this case, the control IC 10 stores a signal indicating that there is a sign of a failure in the switching element 110 in a non-volatile memory in the control IC 10 or in a host ECU. The abnormality notification corresponds to a failure sign notification.

[0040] The period during which the inverter circuit 100 is operating can also be expressed as the inverter circuit 100 is driving, the vehicle is operating, the vehicle is driving, etc. On the other hand, the period before the inverter circuit 100 starts to operate can also be expressed as the inverter circuit 100 is stopped, the vehicle is stopped, the vehicle is not driving, etc.

[0041] <Effects> In this manner, in the drive circuit 1, the current source 71 that generates the monitor voltage for determining the leakage current of the gate terminal 110g is connected in parallel with the on switch circuit. Therefore, the drive circuit 1 can determine the occurrence of leakage current without affecting the switching speed of the on switch circuit.

[0042] In a configuration in which leakage current is determined based on the voltage across the gate resistor 30, it is possible to reduce the resistance value of the gate resistor 30 in order to reduce the loss of the switching element 110. In this case, the accuracy of determining the leakage current may decrease. Furthermore, it is also possible to increase the detection threshold value so as not to erroneously determine that a leakage current is occurring. However, in this case, there is a problem that the determination of the leakage current is delayed.

[0043] In contrast, the drive circuit 1 can prevent a decrease in the accuracy of leak current determination because it does not depend on the resistance value of the gate resistor 30. Furthermore, the drive circuit 1 can prevent a delay in determining the leak current.

[0044] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present disclosure.

[0045] Hereinafter, the second to seventh embodiments will be described as other aspects of the present disclosure. The above-mentioned embodiment and the second to seventh embodiments can be implemented individually, but can also be implemented in appropriate combination. The present disclosure is not limited to the combinations shown in the embodiments, and can be implemented in various combinations.

[0046] Second embodiment The drive circuit 2 of the second embodiment will be described with reference to Figs. 4 and 5. The drive circuit 2 has many points in common with the drive circuit 1. Here, differences from the drive circuit 1 will be mainly described. The drive circuit 2 differs from the drive circuit 1 in the configuration of the leakage current determination circuit 70b. Fig. 4 is a drawing corresponding to Fig. 1. Fig. 5 is a drawing corresponding to Fig. 3.

[0047] 4, the drive circuit 2 includes a leakage current determination circuit 70b. The leakage current determination circuit 70b has a configuration in which a current source 71 is connected in parallel to an off switch circuit. The leakage current determination circuit 70b employs an N-channel MOSFET as a change-over switch 74. The change-over switch 74 has a source terminal connected to the current source 71, a drain terminal connected to the gate terminal 110g, and a gate terminal 74g connected to the control IC 10. The current source 71 is connected to a negative power supply 62.

[0048] The control IC 10 performs the same process as in the first embodiment. Therefore, the drive circuit 2 operates in the same manner as the drive circuit 1. The leakage current determination circuit 70b is switched to active at timing t1 in FIG. 5. This causes the current source 71 to pass a current through the gate terminal 110g. As shown in FIG. 5, the comparator 73 outputs a leakage signal at timing t2. The drive circuit 2 can achieve the same effects as the drive circuit 1.

[0049] Third embodiment The drive circuit 3 of the third embodiment will be described with reference to Figs. 6 and 7. The drive circuit 3 has many points in common with the drive circuit 1. Here, differences from the drive circuit 1 will be mainly described. The drive circuit 3 differs from the drive circuit 1 in the configuration of the leakage current determination circuit 70c. Fig. 6 is a drawing corresponding to Fig. 1. Fig. 7 is a drawing corresponding to Fig. 3.

[0050] As shown in Fig. 6, the drive circuit 3 includes a leakage current determination circuit 70c. The leakage current determination circuit 70c includes a determination voltage source 75 that applies a voltage to a current source 71. That is, a voltage is supplied (applied) to the current source 71 from the determination voltage source 75 that is different from the voltage source 61. The determination voltage source 75 supplies a different voltage V2 that is higher than the gate voltage Vcc to the current source 71. Therefore, as shown in Fig. 7, it is possible to increase the difference between the monitor voltage when a leakage current is occurring and the monitor voltage when no leakage current is occurring. The determination voltage source 75 corresponds to a voltage source for current.

[0051] The control IC 10 performs the same process as in the first embodiment. Therefore, the drive circuit 3 operates in the same manner as the drive circuit 1. Therefore, as shown in Fig. 7, the comparator 73 outputs a leak signal at timing t2.

[0052] The drive circuit 3 can achieve the same effects as the drive circuit 1. Furthermore, the drive circuit 3 can increase or decrease the monitor voltage depending on the presence or absence of a leak current. Therefore, the drive circuit 3 can determine the presence or absence of a leak current with high accuracy. In other words, the drive circuit 3 can determine the presence or absence of a leak current even when noise is superimposed on the monitor voltage or when the current value of the current source 71 is reduced.

[0053] (Fourth embodiment) The drive circuit 4 of the fourth embodiment will be described with reference to Figs. 8 and 9. The drive circuit 4 has many points in common with the drive circuit 1. Here, differences from the drive circuit 1 will be mainly described. The drive circuit 4 differs from the drive circuit 1 in the configuration of a leakage current determination circuit 70d. Fig. 8 is a drawing corresponding to Fig. 1. Fig. 9 is a drawing corresponding to Fig. 3.

[0054] 8, the drive circuit 4 includes a leakage current determination circuit 70d. The leakage current determination circuit 70d includes a determination voltage source 76 instead of the current source 71. The leakage current determination circuit 70d also includes a shunt resistor 77 and an operational amplifier 78.

[0055] The changeover switch 72 has a source terminal connected to a judgment voltage source 76, a drain terminal connected to a shunt resistor 77, and a gate terminal 72g connected to the control IC 10. The shunt resistor 77 has one terminal connected to the judgment voltage source 76 via the changeover switch 72, and the other terminal connected to the gate terminal 110g. A judgment voltage Vreak is applied to the shunt resistor 77. The shunt resistor 77 corresponds to a judgment resistor.

[0056] An input terminal of the operational amplifier 78 is connected to both terminals of the shunt resistor 77. An output terminal of the operational amplifier 78 is connected to an input terminal of the comparator 73. The operational amplifier 78 outputs the voltage across the shunt resistor 77 as a monitor voltage. The operational amplifier 78 corresponds to an output circuit.

[0057] The determination voltage source 76, the shunt resistor 77, and the operational amplifier 78 correspond to a generating circuit. Therefore, the determination voltage source 76 can be said to be a part of a circuit that generates a potential difference (monitor voltage) for improving the detection accuracy of the leakage current.

[0058] The control IC 10 performs the same process as in the first embodiment. Therefore, the drive circuit 4 operates in the same manner as the drive circuit 1. Therefore, as shown in FIG. 9, the comparator 73 outputs a leak signal at timing t2. The drive circuit 4 can achieve the same effect as the drive circuit 1.

[0059] Fifth embodiment The drive circuit 5 of the fifth embodiment will be described with reference to FIG. 10. The drive circuit 5 has many points in common with the drive circuit 4. Here, differences from the drive circuit 4 will be mainly described. The drive circuit 5 differs from the drive circuit 4 in the configuration of a leakage current determination circuit 70e. FIG. 10 corresponds to FIG. 8.

[0060] 10, the drive circuit 5 includes a leakage current determination circuit 70e. The leakage current determination circuit 70e uses the voltage source 61 as a determination voltage source. Therefore, the source terminal of the changeover switch 72 is connected to the voltage source 61. In addition, a gate voltage Vcc is applied to the shunt resistor 77.

[0061] The control IC 10 performs the same process as in the fourth embodiment. Therefore, the drive circuit 5 operates in the same manner as the drive circuit 4. Therefore, the drive circuit 5 can achieve the same effects as the drive circuit 4. Furthermore, the drive circuit 5 does not require a determination voltage source 76 separate from the voltage source 61.

[0062] Moreover, the voltage source 61 may be a variable power source capable of changing a voltage value. The voltage value of the voltage source 61 is changed by the control IC 10. When judging a leakage current, the control IC 10 changes the voltage value to a higher value than when the leakage current is not judged. For example, the control IC 10 changes the voltage value of the voltage source 61 when the change-over switch 72 switches the leakage current judgment circuit 70e to an active state. This enables the drive circuit 5 to increase the difference between the monitor voltage when a leakage current is occurring and the monitor voltage when no leakage current is occurring. Therefore, the drive circuit 5 can judge the presence or absence of a leakage current with high accuracy.

[0063] Sixth embodiment A drive circuit 6 of the sixth embodiment will be described with reference to FIG. 11. The drive circuit 6 has many points in common with the drive circuit 4. Here, differences from the drive circuit 4 will be mainly described. The drive circuit 6 differs from the drive circuit 4 mainly in the configuration of a leakage current determination circuit 70f. FIG. 11 is a drawing corresponding to FIG. 8.

[0064] As shown in Fig. 11, the drive circuit 6 includes a leakage current determination circuit 70f. The drive circuit 6 includes a gate resistor 35 that is common to the on switch circuit and the off switch circuit. The input terminals of an operational amplifier 78 are connected to both terminals of the gate resistor 35. The operational amplifier 78 outputs the voltage across the gate resistor 35 as a monitor voltage. In this way, the leakage current determination circuit 70e uses the gate resistor 35 instead of a shunt resistor.

[0065] The control IC 10 performs the same process as in the fourth embodiment. Therefore, the drive circuit 6 operates in the same manner as the drive circuit 4. Therefore, the drive circuit 6 can achieve the same effects as the drive circuit 4.

[0066] Seventh embodiment The drive circuit 7 of the seventh embodiment will be described with reference to FIG. 12. The drive circuit 7 has many commonalities with the drive circuits 2 and 4. Here, differences from the drive circuits 2 and 4 will be mainly described. The drive circuit 7 differs from the drive circuits 2 and 4 in the configuration of a leakage current determination circuit 70g. FIG. 12 corresponds to FIG. 8.

[0067] 12, the drive circuit 7 includes a leakage current determination circuit 70g. The leakage current determination circuit 70g uses the negative power supply 62 as a determination voltage source. The leakage current determination circuit 70g has a configuration in which a shunt resistor 77 and an operational amplifier 78 are connected in parallel to an off switch circuit. The shunt resistor 77 and the operational amplifier 78 correspond to a generation circuit.

[0068] The change-over switch 74 has a source terminal connected to the negative power supply 62, a drain terminal connected to the shunt resistor 77, and a gate terminal 74g connected to the control IC 10. The shunt resistor 77 has one terminal connected to the drain terminal and the other terminal connected to the gate terminal 110g.

[0069] The control IC 10 performs the same process as in the fourth embodiment. Therefore, the drive circuit 7 operates in the same manner as the drive circuit 4. Therefore, the drive circuit 7 can achieve the same effects as the drive circuit 4.

[0070] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also encompasses various modifications and modifications within the equivalent range. In addition, although various combinations and forms are shown in the present disclosure, other combinations and forms including only one element, more than one element, or less than one element are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0071] 1 to 7: Drive circuit, 10: Control IC, 20: Upper arm switch, 20g: Gate terminal, 30: Gate resistor, 40: Lower arm switch, 40g: Gate terminal, 50: Gate resistor, 61: Voltage source, 70 to 70g: Leakage current determination circuit, 71: Current source, 72: Change-over switch, 72g: Gate terminal, 73: Comparator, 100: Inverter circuit, 110: Switching element, 110g: Gate terminal

Claims

1. A drive circuit for driving a switching element (110), an on-switch circuit (20, 30) connected to a gate terminal of the switching element for turning on the switching element; an off switch circuit (40, 50) connected to the gate terminal and driving the switching element to an off state; a determination circuit (70a to 70g) connected to the gate terminal and determining whether or not a gate leakage current is occurring in the switching element; The judgment circuit includes a generation circuit connected in parallel to the on switch circuit or the off switch circuit, which generates a judgment voltage for judging the gate leakage current, and a drive circuit that judges that the gate leakage current is occurring when the judgment voltage is equal to or greater than a threshold value.

2. A control unit (10) for controlling the on switch circuit and the off switch circuit, 2 . The drive circuit according to claim 1 , wherein the determination circuit outputs a leak signal indicating that the gate leakage current is occurring to the control unit when the determination voltage is equal to or greater than the threshold value.

3. the determination circuit includes a change-over switch (72, 74) connected in parallel with the on switch circuit or the off switch circuit for switching between enabled and disabled states of the determination circuit, The drive circuit according to claim 2 , wherein the control unit controls the change-over switch to switch between enabling and disabling the determination circuit.

4. The drive circuit according to claim 3, wherein the control unit controls the change-over switch to enable the determination circuit when the gate terminal is in a stopped state below an on-threshold value, and determines that the gate leakage current is occurring when the leakage signal is input.

5. The generating circuit includes a current source (71) that supplies a current to the gate terminal, 5. The drive circuit according to claim 2, wherein the determination circuit determines that the gate leakage current is occurring when the determination voltage, which correlates with the gate terminal voltage at the gate terminal, is equal to or greater than the threshold value.

6. A gate voltage source (61) that applies a gate voltage to the gate terminal; 6. The drive circuit of claim 5, further comprising: a current voltage source (75) for applying a different voltage to the current source that is greater than the gate voltage.

7. The drive circuit according to any one of claims 2 to 4, wherein the generation circuit comprises a judgment resistor (77) connected between a judgment voltage source (76) and the gate terminal, and an output circuit (78) that outputs a voltage across the judgment resistor as the judgment voltage.

8. A gate voltage source (61) for applying a gate voltage to the gate terminal, The drive circuit according to any one of claims 2 to 4, wherein the generating circuit comprises a judgment resistor (77) connected between the gate voltage source and the gate terminal, and an output circuit (78) that outputs a voltage across the judgment resistor as the judgment voltage.

9. 9. The drive circuit according to claim 8, wherein the gate voltage source is a variable power source capable of changing a voltage value, and when the gate leakage current is determined, the gate voltage source sets a voltage value higher than that when the gate leakage current is not determined.

10. A gate resistor (35) connected to the gate terminal; 5. The drive circuit according to claim 2, wherein the generating circuit includes an output circuit (78) that outputs a voltage across the gate resistor as the determination voltage.

Images