Semiconductor element drive circuit

Abstract

To provide a driving circuit for a semiconductor element capable detection without having a transistor included in a path for detecting leak current.SOLUTION: In a driving circuit 7, serial circuits of high-side switches M1 to M3 and charging gate resistors R1 to R3 are connected between a driving power source and a gate of a FET 1. A leak current detection unit 2 detects the voltage generated in a conduction path including the charging gate resistor R3 when the high-side switch M3 is turned on. A control unit 5 controls the on / off of the high-side switches M1 to M3 and a low-side switch M4 and determines whether there is a leak current flowing a source of the FET 1 from the gate on the basis of the voltage detected by the leak current detection unit 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a circuit for driving a voltage-driven semiconductor element.

Background Art

[0002] For a voltage-driven semiconductor element such as an N-channel MOSFET, various circuits for detecting a current leaking from the gate to the source or from the drain to the gate have been proposed. For example, in Patent Document 1, by switching the driving ability in a circuit for driving a semiconductor element, a leakage current is detected using a gate resistor having a high resistance value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration of Patent Document 1, since there is a MOSFET connected in series to the gate resistor in the path for detecting the leakage current, detection is performed including the on-resistance of the MOSFET. Therefore, there is a problem that the detection accuracy of the leakage current is reduced accordingly.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a driving circuit for a semiconductor element that can detect a leakage current without including a transistor in the detection path.

Means for Solving the Problems

[0006] According to the semiconductor element drive circuit described in claim 1, multiple series circuits of high-side switches (M1, M2, M3) and charging gate resistors (R1, R2, R3) are connected between the drive power supply and the gate of the voltage-driven semiconductor element (1). Among the multiple charging gate resistors, the series circuit including the one with the highest resistance value is designated as the detection switch (M3) and the detection gate resistor (R3), respectively. The voltage detection unit (2) detects the voltage generated in the current path including the detection gate resistor when the detection switch is turned on. The control unit (5) controls the on / off state of the multiple high-side switches and, based on the voltage detected by the voltage detection unit, determines whether or not there is a leakage current flowing from the gate to the low-potential conducting terminal of the semiconductor element.

[0007] With this configuration, the voltage detection unit does not include switches such as MOSFETs in the current path used to detect voltage. Furthermore, since the gate resistor with the highest resistance value among the charging gate resistors is used as the detection gate resistor, leakage current can be detected at a higher voltage. Overall, leakage current can be detected with higher accuracy.

[0008] According to the semiconductor device drive circuit described in claim 3, a series circuit of a reverse current prevention element (M8), a first high-side switch (M1), and a first charging gate resistor (R1) is connected between a first drive power supply (V1) and the gate of a voltage-driven semiconductor device (1). In addition, a series circuit of a second high-side switch (M7) and a second charging gate resistor (M7) with a higher resistance value is connected between a second drive power supply (V2) with a higher voltage and the common connection point of the first high-side switch and the first charging gate resistor. The voltage detection unit (2) detects the voltage generated in the current path including the first and second gate resistors when the second high-side switch is turned on. The control unit (16) controls the on / off state of the first and second high-side switches and determines whether or not there is a leakage current flowing from the gate to the low-potential conducting terminal of the semiconductor device based on the voltage detected by the voltage detection unit.

[0009] With this configuration, when driving semiconductor elements that require a high voltage to turn on, the system can be driven in two stages: first, it can be turned on quickly using only the first charging gate resistor, and then it can be turned on slowly using the first and second charging gate resistors. Furthermore, since the voltage detection unit does not include a switch and detects the voltage generated in the current path including the first and second gate resistors, it can detect the occurrence of leakage current with higher voltage and higher accuracy.

[0010] According to the semiconductor element drive circuit described in claim 5, multiple series circuits of discharge gate resistors (R4, R5, R6) and low-side switches (M4, M5, M6) are connected between the gate of the voltage-driven semiconductor element (1) and a low-potential reference point. Among the multiple discharge gate resistors, the series circuit including the one with the highest resistance value is designated as the detection switch (M6) and detection gate resistor (R6), respectively, and the voltage detection unit (2) detects the voltage generated in the current path including the detection gate resistor when the detection switch is turned on. The control unit (13) controls the on / off state of the multiple low-side switches and determines whether or not there is a leakage current flowing from the high-potential side conducting terminal of the semiconductor element to the gate based on the voltage detected by the voltage detection unit. Therefore, the leakage current flowing from the high-potential side conducting terminal of the semiconductor element to the gate can be detected with high accuracy, similar to claim 1. [Brief explanation of the drawing]

[0011] [Figure 1] This is a first embodiment, and the diagram shows the configuration of the semiconductor element drive circuit. [Figure 2] This diagram shows the change in gate voltage when the high-side switch M1 is turned on. [Figure 3] This diagram shows the change in gate voltage when the high-side switch M3 is turned on. [Figure 4] This is a second embodiment, and the diagram shows the configuration of the semiconductor element drive circuit. [Figure 5] This is a third embodiment, and the diagram shows the configuration of the semiconductor element drive circuit. [Figure 6]This diagram shows the change in gate voltage when high-side switches M1 and M7 are turned on sequentially (assuming no leakage current is generated). [Figure 7] This diagram shows the change in gate voltage when high-side switches M1 and M7 are sequentially turned on (with leakage current present). [Figure 8] This is a fourth embodiment, and the diagram shows the configuration of the semiconductor element drive circuit. [Modes for carrying out the invention]

[0012] (First Embodiment) As shown in Figure 1, the drive circuit of this embodiment drives an N-channel MOSFET 1, which is a voltage-driven semiconductor element. FET 1 constitutes, for example, the lower arm side of a bridge circuit. Its source is connected to ground, which is a low-potential reference point, and its drain is connected to an upper-arm FET (not shown). The drain of FET 1 is a high-potential conductive terminal, and its source is a low-potential conductive terminal.

[0013] High-side switches M1-M3 and charging gate resistors R1-R3 are connected in series between the drive power supply and the gate of FET1. High-side switches M1-M3 are, for example, P-channel MOSFETs. In addition, a series circuit of a discharge gate resistor R4 and a low-side switch M4 is connected between the gate of FET1 and ground. Low-side switch M4 is, for example, an N-channel MOSFET.

[0014] Furthermore, the relative values ​​of the charging gate resistors R1 to R3 are set to (R3 > R2 > R1), and the relative values ​​of the on-resistances of the high-side switches M1 to M3 are set to (M3 > M2 > M1). High-side switch M3 corresponds to a detection switch, and charging gate resistor R3 corresponds to a detection resistor.

[0015] The source of the high-side switch M3 and the drain of the low-side switch M4 are respectively connected to the input terminals of a differential amplifier circuit 3 that constitutes a leakage current detection unit 2. The leakage current detection unit 2 corresponds to a voltage detection unit. The output terminal of the differential amplifier circuit 3 is connected to the input terminal of a control unit 5 via an A / D converter 4. The control unit 5 is composed of, for example, a microcomputer and controls the on / off of each switch M1 to M4. In the above, excluding the FET1 and the gate resistors R1 to R4 constitutes a drive IC6. The drive IC6 and the gate resistors R1 to R4 constitute a drive circuit 7.

[0016] Next, the operation of this embodiment will be described. When turning on the high-side switches M1 to M3, the high-side switches M1 to M3 can be selectively used for the purpose of changing the speed of the on-operation according to the magnitude relationship of the resistance values set in the charging gate resistors R1 to R3 when turning on the FET1. When turning off the low-side switch M4 and turning on the FET1 with the high-side switch M1 having the minimum resistance value and the charging gate resistor R1, the speed of the on-operation becomes high, and when turning on with the high-side switch M3 having the maximum resistance value and the charging gate resistor R3, the speed of the on-operation becomes low.

[0017] Also, as shown in FIG. 1, when turning on the high-side switch M3 and turning off the low-side switch M4, the gate of the FET1 is charged by the drive power supply through the high-side switch M3 and the charging gate resistor R3. At this time, if no leakage current flows from the gate of the FET1 to the source side, as shown in FIG. 3, no current flows through the charging gate resistor R3 after the gate of the FET1 is charged. On the other hand, if a leakage current flows from the gate to the source side, current also flows through the charging gate resistor R3 even after the gate is charged. The control unit 5 determines whether a leakage current is flowing or not based on the magnitude of the voltage detected by the leakage current detection unit 2 during the period after the gate of the FET1 is charged and the gate voltage is stabilized.

[0018] When the high-side switch M3 shown in FIG. 3 is turned on, the resistance value of the charging path is higher than when the high-side switch M1 shown in FIG. 2 is turned on. Therefore, when there is a leakage current flowing, the voltage becomes higher. Thus, the leakage current can be detected with higher precision.

[0019] As described above, according to the present embodiment, in the drive circuit 7, a series circuit of high-side switches M1 to M3 and charging gate resistors R1 to R3 is connected between the drive power supply and the gate of the FET1. The leakage current detection unit 2 detects the voltage generated in the energization path including the charging gate resistor R3 when the high-side switch M3 is turned on. The control unit 5 controls the on / off of the high-side switches M1 to M3 and the low-side switch M4, and determines the presence or absence of the leakage current flowing from the gate to the source of the FET1 based on the voltage detected by the leakage current detection unit 2.

[0020] With such a configuration, the energization path for the leakage current detection unit 2 to detect the voltage does not include a switch such as a MOSFET. And since the resistor having the highest resistance value among the charging gate resistors R1 to R3 is used as the detection gate resistor, the generation of the leakage current can be detected at a higher voltage. Overall, the leakage current can be detected with higher accuracy. Also, by setting the magnitude relationship of the on-resistances of the high-side switches M1 to M3 as (M3 > M2 > M1), the driving capabilities between these switches can be changed.

[0021] (Second Embodiment) Hereinafter, the same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted, and the different parts will be described. The drive circuit 11 of the second embodiment shown in FIG. 4 includes a drive IC 12 that replaces the drive IC 6. The drive IC 12 also includes three switches M4 to M6 for the low-side switch, and the drains of these switches M4 to M6 are each connected to the gate of the FET1 via discharge gate resistors R4 to R6.

[0022] The on-resistance relationship of the low-side switches M4 to M6 is set to (M6 > M5 > M4). The discharge gate resistors R4 to R6 are set to (R6 > R5 > R4). The control unit 13 controls the on / off state of the low-side switches M4 to M6 in addition to the high-side switches M1 to M3. One of the input terminals of the leakage current detection unit 2 is connected to the drain of the low-side switch M6 instead of the low-side switch M4.

[0023] Next, the operation of the second embodiment will be described. The control unit 13 can change the operating speed when turning off the FET1 by selectively turning on the low-side switches M4 to M6. In addition, by turning on any one of the high-side switches M1 to M3 to charge the gate of the FET1, the control unit 13 can determine whether or not there is a leakage current flowing from the drain to the gate of the FET1 by turning on the low-side switch M6.

[0024] If no leakage current flows from the drain to the gate of FET1, no current will flow through the discharge gate resistor R6 after the gate of FET1 has been discharged. On the other hand, if leakage current flows from the drain to the gate, current will continue to flow through the discharge gate resistor R6 even after the gate has been discharged. The control unit 13 determines whether or not leakage current is flowing based on the magnitude of the voltage detected by the leakage current detection unit 2 after the gate of FET1 has been discharged.

[0025] As described above, according to the second embodiment, the leakage current flowing from the drain to the gate side of FET1 can also be detected with high accuracy.

[0026] (Third embodiment) The drive circuit 14 of the third embodiment shown in Figure 5 includes a drive IC 15 that replaces the drive IC 6 of the first embodiment. The drive IC 15 is supplied with a first drive power supply V1 and a second drive power supply V2, and the relative magnitudes of the two voltages are set to (V2 > V1). There is a first high-side switch M1 and a second high-side switch M7, and a series circuit of a reverse current prevention switch M8, a high-side switch M1, and a first charging gate resistor R1, which is a P-channel MOSFET, is connected between the first drive power supply V1 and the gate of the FET1. The source of the reverse current prevention switch M8 is connected to the source of the high-side switch M1, and its drain is connected to the first drive power supply V1.

[0027] A series circuit of the high-side switch M7 and the second charging gate resistor R7 is connected between the second drive power supply V2 and the drain of the high-side switch M1. The relative resistance values ​​of the gate resistors R1 and R7 are set to (R7 > R1). The relative on-resistances of the high-side switches M1 and M7 are set to (M7 > M1). One of the input terminals of the leakage current detection unit 2 is connected to the drain of the high-side switch M7 instead of the high-side switch M3. The control unit 16 controls the on / off state of each switch M1, M4, M7 and M8.

[0028] Next, the operation of the third embodiment will be described. As shown in Figures 6 and 7, when turning on FET1, the high-side switch M1 is first turned on to quickly raise the gate voltage of FET1 to V1. Subsequently, the high-side switch M7 is turned on to slowly raise the gate voltage to V2. At this time, in order to prevent reverse current from flowing back to the first drive power supply V1 via the body diode of the high-side switch M1, the reverse current prevention switch M8 is turned off.

[0029] As shown in Figure 7, the control unit 16 determines whether or not there is a leakage current flowing from the gate to the source during the period when the gate voltage of FET1 is stable at V2, in the same manner as in the first embodiment. Note that within the control unit 16, the high-side switch M1 may be driven by a switch, and the high-side switch M7 may be driven by a constant voltage.

[0030] For example, if the voltage-driven semiconductor element used instead of FET1 is a SiC (silicon carbide) element that requires a higher gate voltage to reach a fully-on state, then to reduce switching losses due to the SiC, the SiC is turned on quickly using a low first power supply voltage V1, and then turned on slowly using a higher second power supply voltage V2 after the gate has been sufficiently charged.

[0031] As described above, according to the third embodiment, a series circuit of a reverse current prevention switch M8, a first high-side switch M1, and a first charging gate resistor R1 is connected between the first drive power supply V1 and the gate of the FET1. In addition, a series circuit of a second high-side switch M7 and a second charging gate resistor R7 is connected between the second drive power supply V2, which has a higher voltage, and the drain of the first high-side switch M1. The leakage current detection unit 2 detects the voltage generated in the current path including the first and second gate resistors R7 and R1 when the second high-side switch M7 is turned on. The control unit 16 controls the on / off state of the first and second high-side switches M1 and M7, and determines whether or not there is a leakage current flowing from the gate to the source of the FET1 based on the voltage detected by the leakage current detection unit 2.

[0032] With this configuration, when driving semiconductor elements that require a high voltage to turn on, such as SiC, the element can be driven in two stages: first, it is turned on quickly using only the first charging gate resistor R1, and then it is turned on slowly using the first and second charging gate resistors R1 and R7. Furthermore, the leakage current detection unit 2 does not include a switch and detects the voltage generated in the current path including the first and second gate resistors R1 and R7, so it can detect the occurrence of leakage current with higher voltage and higher accuracy.

[0033] (Fourth Embodiment) The fourth embodiment shown in Figure 8 is modified in which the low-potential reference point of the drive IC 12 in the second embodiment is set to a negative potential instead of ground, which is 0V. The low-potential reference point of FET 1 is ground, as in the second embodiment. Thus, the low-potential reference point of FET 1 and the low-potential reference point of the drive IC 12 may be at different potentials. As mentioned above, if the semiconductor element is SiC instead of FET 1, the threshold voltage Vt of SiC is lower, so by setting the low-potential reference point of the drive IC 12 to a negative potential, the gate voltage at the off state can be made lower than the source voltage, ensuring that the device is reliably turned off.

[0034] (Other embodiments) The number of high-side switches and charging gate resistors, and the number of discharge gate resistors and low-side switches may be "2" or "4" or more. It is not necessary to set a relative order for the on-resistance of the high-side switch and the low-side switch; the on-resistance can be the same.

[0035] The voltage detection unit does not necessarily need to detect the voltage generated in the current path by differential detection. The reverse current prevention element can also be a diode whose cathode is connected to the source of the high-side switch M1. Voltage-driven semiconductor devices are not limited to N-channel MOSFETs; P-channel MOSFETs, IGBTs, and other types can also be used. This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure. [Explanation of symbols]

[0036] In the diagram, 1 is an N-channel MOSFET, 2 is a leakage current detection unit, 3 is a differential amplifier, 5 is a control unit, 6 is a driver IC, 7 is a driver circuit, M1 to M3 are high-side switches, and R1 to R3 are charging gate resistors.

Claims

1. The device includes multiple series circuits of high-side switches (M1, M2, M3) and charging gate resistors (R1, R2, R3) connected between the drive power supply and the gate of the voltage-driven semiconductor element (1). The resistance values ​​of the aforementioned multiple charging gate resistors are set to different values ​​from each other, and the series circuit that includes the one with the highest resistance value is designated as the detection switch (M3) and the detection gate resistor (R3), respectively. A voltage detection unit (2) detects the voltage generated in the current path including the detection gate resistor when the detection switch is turned on, A semiconductor element drive circuit comprising: a control unit (5) that controls the on / off state of the plurality of high-side switches and determines whether or not there is a leakage current flowing from the gate to the low-potential side conductive terminal of the semiconductor element based on the voltage detected by the voltage detection unit.

2. The aforementioned high-side switch is composed of semiconductor elements, The semiconductor element drive circuit according to claim 1, wherein the on-resistance of the detection switch is set higher than the on-resistance of the other high-side switches.

3. First drive power supply (V1), A second drive power supply (V2) has a higher voltage than this first drive power supply, A series circuit comprising a reverse current prevention element (M8), a first high-side switch (M1), and a first charging gate resistor (R1) is connected between the first drive power supply and the gate of the voltage-driven semiconductor element. A series circuit of a second high-side switch (M7) and a second charging gate resistor (R7) having a resistance value higher than that of the first charging gate resistor is connected between the second drive power supply and the common connection point of the first high-side switch and the first charging gate resistor, A voltage detection unit (2) detects the voltage generated in the current path including the first and second gate resistors when the second high-side switch is turned on, A semiconductor element drive circuit comprising: a control unit (16) that controls the on / off state of the first and second high-side switches and determines whether or not there is a leakage current flowing from the gate to the low-potential side conductive terminal of the semiconductor element based on the voltage detected by the voltage detection unit.

4. The first and second high-side switches are composed of semiconductor elements. The semiconductor element drive circuit according to claim 3, wherein the on-resistance of the second high-side switch is set higher than the on-resistance of the first high-side switch.

5. The device comprises multiple series circuits of discharge gate resistors (R4, R5, R6) and low-side switches (M4, M5, M6) connected between the gate of a voltage-driven semiconductor element (1) and a low-potential reference point. The resistance values ​​of the aforementioned multiple discharge gate resistors are set to different values ​​from each other, and the series circuit that includes the one with the highest resistance value is designated as the detection switch (M6) and the detection gate resistor (R6), respectively. A voltage detection unit (2) detects the voltage generated in the current path including the detection gate resistor when the detection switch is turned on, A semiconductor element drive circuit comprising: a control unit (13) that controls the on / off state of the plurality of low-side switches and determines whether or not there is a leakage current flowing from the high-potential side conductive terminal of the semiconductor element to the gate based on the voltage detected by the voltage detection unit.

6. The aforementioned low-side switch is composed of semiconductor elements. The semiconductor element drive circuit according to claim 5, wherein the on-resistance of the detection switch is set higher than the on-resistance of the other low-side switches.

7. The voltage detection unit detects the voltage generated in the current path by differential means, according to any one of claims 1 to 6, in the semiconductor element drive circuit.

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