WO2024195419A1

WO2024195419A1 - Drive circuit for semiconductor element

Info

Publication number: WO2024195419A1
Application number: PCT/JP2024/006290
Authority: WO
Inventors: 雅広戸森; 一輝山内
Original assignee: 株式会社デンソー
Priority date: 2023-03-17
Filing date: 2024-02-21
Publication date: 2024-09-26
Also published as: JP2024132314A

Abstract

In a drive circuit 7 according to one embodiment of the present disclosure, a series circuit of high-side switches M1 to M3 and charging gate resistors R1 to R3 is connected between a drive power supply and a gate of a FET 1. A leakage current detection unit 2 detects a voltage generated in an energization path including the charging gate resistor R3 when the high-side switch M3 is turned on. A control unit 5 controls whether the high-side switches M1 to M3 and a low-side switch M4 are on or off and assesses whether a leakage current flowing from the gate to the source of the FET 1 is present on the basis of the voltage detected by the leakage current detection unit 2.

Description

Semiconductor device driver circuit

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Application No. 2023-43057, filed on March 17, 2023, the contents of which are incorporated herein by reference.

This disclosure relates to a circuit that drives a voltage-driven semiconductor element.

For example, various circuits have been proposed for detecting current leaking from the gate to the source or from the drain to the gate of a voltage-driven semiconductor element such as an N-channel MOSFET. For example, in Patent Document 1, the driving capability is switched within the circuit that drives the semiconductor element, and leakage current is detected using a gate resistor with a high resistance value.

Patent No. 6949280

However, in the configuration of Patent Document 1, the path for detecting the leakage current includes a MOSFET connected in series with the gate resistor, and the on-resistance of the MOSFET is also detected. This causes a problem in that the accuracy of detecting the leakage current decreases accordingly.

This disclosure has been made in consideration of the above circumstances, and its purpose is to provide a drive circuit for a semiconductor element that can detect leakage current without including a transistor in the path for detecting leakage current.

According to the semiconductor element drive circuit disclosed herein, multiple series circuits of high-side switches and charging gate resistors are connected between the drive power supply and the gate of a voltage-driven semiconductor element. Among the multiple charging gate resistors, those constituting the series circuit including the one with the highest resistance value are designated as the detection switch and detection gate resistor, respectively. When the detection switch is turned on, the voltage detection unit detects the voltage generated in the current path including the detection gate resistor. The control unit controls the on/off of the multiple high-side switches, and determines the presence or absence of 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.

In this configuration, the current path through which the voltage detection unit detects the voltage does not include a switch such as a MOSFET. Furthermore, the gate resistor for detection has the highest resistance among the gate resistors for charging, so that the occurrence of leakage current can be detected at a higher voltage. Overall, leakage current can be detected with higher accuracy.

Furthermore, according to the semiconductor element drive circuit of the present disclosure, a series circuit of a reverse current prevention element, a first high-side switch, and a first charging gate resistor is connected between a first drive power supply and the gate of a voltage-driven semiconductor element. Furthermore, a series circuit of a second high-side switch and a second charging gate resistor having a higher resistance value is connected between a second drive power supply having a higher voltage and a common connection point of the first high-side switch and the first charging gate resistor. When the second high-side switch is turned on, the voltage detection unit detects the voltage generated in the current path including the first and second gate resistors. The control unit controls the on/off of the first and second high-side switches, and determines the presence or absence of 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.

With this configuration, when driving a semiconductor element that requires a high voltage to turn on, it can be driven in two stages, first by turning it on at high speed using only the first charging gate resistor, and then by turning it on at a slower speed 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 that includes the first and second gate resistors, it is possible to detect the occurrence of leakage current at a higher voltage with high accuracy.

Furthermore, according to the semiconductor element drive circuit of the present disclosure, multiple series circuits of discharge gate resistors and low-side switches are connected between the gate of a voltage-driven semiconductor element and a low potential reference point. Among the multiple discharge gate resistors, those constituting the series circuit including the one with the highest resistance value are respectively designated as a detection switch and a detection gate resistor, and a voltage detection unit detects a voltage generated in a current path including the detection gate resistor when the detection switch is turned on. A control unit controls the on/off of the multiple low-side switches, and determines the presence or absence of 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. Therefore, in a manner similar to the above disclosure, it is possible to detect with high accuracy the leakage current flowing from the high potential side conductive terminal of the semiconductor element to the gate.

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a diagram showing a configuration of a drive circuit for a semiconductor element in a first embodiment; FIG. 2 is a diagram showing a change in the gate voltage when the high-side switch M1 is turned on. FIG. 3 is a diagram showing a change in the gate voltage when the high-side switch M3 is turned on. FIG. 4 is a diagram showing a configuration of a drive circuit for a semiconductor element in a second embodiment; FIG. 5 is a diagram showing a configuration of a drive circuit for a semiconductor element in a third embodiment; FIG. 6 is a diagram showing a change in gate voltage when the high-side switches M1 and M7 are sequentially turned on (when no leakage current occurs). FIG. 7 is a diagram showing a change in gate voltage when the high-side switches M1 and M7 are sequentially turned on (when a leakage current is generated). FIG. 8 is a diagram showing the configuration of a drive circuit for a semiconductor element in the fourth embodiment.

First Embodiment
As shown in Fig. 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, with its source connected to the ground, which is the low-potential side reference point, and its drain connected to, for example, an upper arm FET (not shown). The drain of FET 1 is a high-potential side conduction terminal, and the source is a low-potential side conduction terminal.

High-side switches M1 to M3 and charging gate resistors R1 to R3 are connected in series between the drive power supply and the gate of FET1. The high-side switches M1 to M3 are, for example, P-channel MOSFETs. A series circuit of a discharging gate resistor R4 and a low-side switch M4 is connected between the gate of FET1 and ground. The low-side switch M4 is, for example, an N-channel MOSFET.

The relationship between the resistance values of the charging gate resistors R1 to R3 is set to (R3>R2>R1), and the relationship between the on-resistance values of the high-side switches M1 to M3 is set to (M3>M2>M1). The high-side switch M3 corresponds to the detection switch, and the charging gate resistor R3 corresponds to the detection resistor.

The source of the high-side switch M3 and the drain of the low-side switch M4 are each connected to the input terminals of a differential amplifier circuit 3 that constitutes the 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 the 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 of the switches M1 to M4. The above, excluding FET1 and gate resistors R1 to R4, constitutes the drive IC 6. The drive IC 6 and gate resistors R1 to R4 constitute the drive circuit 7.

Next, the operation of this embodiment will be described. When FET1 is turned on, the high-side switches M1 to M3 can be used to change the speed of the on operation depending on the magnitude relationship of the resistance values set in the charging gate resistors R1 to R3. If the low-side switch M4 is turned off and FET1 is turned on by the high-side switch M1 and charging gate resistor R1, which have the smallest resistance value, the on operation speed will be high, and if it is turned on by the high-side switch M3 and charging gate resistor R3, which have the largest resistance value, the on operation speed will be low.

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

When the high-side switch M3 shown in FIG. 3 is turned on, the resistance of the charging path is higher than when the high-side switch M1 shown in FIG. 2 is turned on, so the voltage when leakage current flows is higher. Therefore, leakage current can be detected with higher accuracy.

As described above, according to this 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 FET1. When the high-side switch M3 is turned on, the leakage current detection unit 2 detects the voltage generated in the current path including the charging gate resistor R3. 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 leakage current flowing from the gate to the source of FET1 based on the voltage detected by the leakage current detection unit 2.

With this configuration, the current path used by the leakage current detection unit 2 to detect voltage does not include a switch such as a MOSFET. And, because the gate resistor with the highest resistance among the charging gate resistors R1 to R3 is used as the detection gate resistor, the occurrence of leakage current can be detected at a higher voltage. Overall, leakage current can be detected with higher accuracy. Also, by setting the magnitude relationship of the on-resistance of the high-side switches M1 to M3 to (M3>M2>M1), the drive capacity between these switches can be changed.

Second Embodiment
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals and their explanations are omitted, and only the different parts are explained. A drive circuit 11 of the second embodiment shown in Fig. 4 includes a drive IC 12 instead of the drive IC 6. The drive IC 12 also includes three switches M4 to M6 as low-side switches, and the drains of these switches M4 to M6 are connected to the gate of FET1 via discharge gate resistors R4 to R6, respectively.

The magnitude relationship of the on-resistance of the low-side switches M4 to M6 is set to (M6>M5>M4). The magnitude relationship of the discharge gate resistors R4 to R6 is set to (R6>R5>R4). The control unit 13 controls the on-off 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.

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

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 is 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 is discharged. After the gate of FET1 is 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.

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

Third Embodiment
The driving circuit 14 of the third embodiment shown in Fig. 5 includes a driving IC 15 that replaces the driving IC 6 of the first embodiment. The driving IC 15 is supplied with a first driving power source V1 and a second driving power source V2, and the magnitude relationship between the two voltages is set to (V2>V1). There are a first high-side switch M1 and a second high-side switch M7, and a series circuit of a backflow prevention switch M8, which is a P-channel MOSFET, the high-side switch M1, and a first charging gate resistor R1 is connected between the first driving power source V1 and the gate of FET1. The source of the backflow prevention switch M8 is connected to the source of the high-side switch M1, and the drain is connected to the first driving power source V1.

A series circuit of a high-side switch M7 and a second charging gate resistor R7 is connected between the second driving power source V2 and the drain of the high-side switch M1. The magnitude relationship between the resistance values of the gate resistors R1 and R7 is set to (R7>R1). The magnitude relationship between the on-resistances of the high-side switches M1 and M7 is 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 of each of the switches M1, M4, M7, and M8.

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

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

For example, if the voltage-driven semiconductor element instead of FET1 is an element such as SiC (silicon carbide) that requires a higher gate voltage to be fully on, in order to reduce the switching loss due to the SiC, the SiC is turned on at high speed by the low voltage first power supply voltage V1, and after the gate is sufficiently charged, it is turned on at a slower speed by the high voltage second power supply voltage V2.

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 driving power source V1 and the gate of 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 driving power source V2, which has a higher voltage, and the drain of the first high-side switch M1. When the second high-side switch M7 is turned on, the leak current detection unit 2 detects the voltage generated in the current path including the first and second gate resistors R7 and R1. The control unit 16 controls the on/off of the first and second high-side switches M1 and M7, and determines the presence or absence of a leak current flowing from the gate to the source of FET1 based on the voltage detected by the leak current detection unit 2.

With this configuration, when driving a semiconductor element such as SiC that requires a high voltage to be turned on, it can be driven in two stages, first by turning it on at high speed using only the first charging gate resistor R1, and then by turning it on at a slower speed using the first and second charging gate resistors R1 and R7. Furthermore, since 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, it can detect the occurrence of leakage current with high accuracy at a higher voltage.

Fourth Embodiment
In the fourth embodiment shown in Fig. 8, the low potential reference point of the driving IC 12 in the second embodiment is set to a negative potential instead of the ground, which is 0V. The low potential reference point of FET1 is the ground as in the second embodiment. In this way, the low potential reference point of FET1 and the low potential reference point of the driving IC 12 may be at different potentials. As described above, when the semiconductor element is SiC instead of FET1, the threshold voltage Vt of SiC is lower, so that the gate voltage in the off state can be made lower than the source voltage and the driving IC 12 can be reliably turned off.

Other Embodiments
The number of pairs of high-side switches and charging gate resistors, and the number of pairs of discharging gate resistors and low-side switches may be "2" or "4" or more.
It is not necessary to set a magnitude relationship between the on-resistance of the high-side switch and the on-resistance of the low-side switch, and the on-resistance may be the same.

The voltage detection section does not necessarily need to differentially detect the voltage occurring in the current path.
The reverse current prevention element may be a diode having a cathode connected to the source of the high-side switch M1.
The voltage-driven semiconductor element is not limited to an N-channel MOSFET, but may be a P-channel MOSFET, an IGBT, or the like.
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, various combinations and forms, and 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.

Claims

The semiconductor device (1) includes a plurality of series circuits each including a high-side switch (M1, M2, M3) and a gate resistor (R1, R2, R3) for charging, the series circuits being connected between a driving power supply and a gate of the voltage-driven semiconductor element (1);
The resistance values of the plurality of charging gate resistors are set to different values, and among them, those constituting a series circuit including the one with the highest resistance value are respectively designated as a detection switch (M3) and a detection gate resistor (R3),
a voltage detection unit (2) that detects a voltage generated in a current path including the detection gate resistor when the detection switch is turned on;
a control unit (5) that controls the on/off of the plurality of high-side switches and determines, based on the voltage detected by the voltage detection unit, whether or not there is a leakage current flowing from the gate to a low potential side conduction terminal of the semiconductor element.
the high-side switch is composed of a semiconductor element,
2. The semiconductor device 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.
A first driving power source (V1);
a second driving power source (V2) having a voltage higher than that of the first driving power source;
a series circuit including a reverse current prevention element (M8), a first high-side switch (M1), and a first charging gate resistor (R1) connected between the first driving power supply and a gate of a 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 set higher than that of the first charging gate resistor, the series circuit being connected between the second driving power supply and a common connection point of the first high-side switch and the first charging gate resistor;
a voltage detection unit (2) that detects a voltage generated in a current path including the first and second gate resistors when the second high-side switch is turned on;
a control unit (16) that controls on/off of the first and second high-side switches and determines, based on the voltage detected by the voltage detection unit, whether or not there is a leakage current flowing from the gate to a low potential side conduction terminal of the semiconductor element.
the first and second high-side switches are formed of semiconductor elements,
4. The semiconductor device drive circuit according to claim 3, wherein an on-resistance of the second high-side switch is set higher than an on-resistance of the first high-side switch.
A plurality of series circuits each including a discharge gate resistor (R4, R5, R6) and a low-side switch (M4, M5, M6) are connected between a gate of a voltage-driven semiconductor element (1) and a low potential reference point,
The resistance values of the plurality of discharge gate resistors are set to different values, and among them, those constituting a series circuit including the one with the highest resistance value are respectively designated as a detection switch (M6) and a detection gate resistor (R6),
a voltage detection unit (2) that detects a voltage generated in a current path including the detection gate resistor when the detection switch is turned on;
a control unit (13) that controls the on/off of the plurality of low-side switches and determines whether or not there is a leakage current flowing from the high potential side conduction terminal of the semiconductor element to the gate based on the voltage detected by the voltage detection unit.
the low-side switch is composed of a semiconductor element,
5. The semiconductor device drive circuit according to claim 4, wherein the on-resistance of the detection switch is set higher than the on-resistance of the other low-side switches.
The semiconductor element drive circuit according to any one of claims 1 to 6, wherein the voltage detection unit differentially detects the voltage generated in the current path.