Gate drive device and electronic control device

Abstract

The present invention comprises: constant current drive circuits (301, 401) for controlling, on the basis of a prescribed reference voltage, a drive current applied to a gate terminal of a gate drive power semiconductor element (200); and diagnosis circuits (302, 402) for diagnosing the presence or absence of an abnormality in the constant current drive circuits (301, 401), wherein the constant current drive circuits (301, 401) generate the constant drive current by applying, to reference resistors (33, 43), negative feedback voltages (36, 46) that are constant voltages controlled by negative feedback, and the diagnosis circuits (302, 402) compare the negative feedback voltages (36, 46) with diagnostic voltages (VdiagON, VdiagOFF) corresponding to the reference voltage, and diagnose, on the basis of a result of the comparison, the presence or absence of an abnormality in the constant current drive circuits (301, 401).

Description

Gate drive and electronic control device

[0001] The present invention relates to a gate driver for driving a power semiconductor element and an electronic control device using the same.

[0002] Conventionally, a switching power supply circuit that is simply configured to drive a power semiconductor element (hereinafter also referred to as a "power device") having a switching function and that can easily switch the threshold voltage for overcurrent protection operation while monitoring the output voltage is disclosed in Patent Document 1. Patent Document 1 describes that the switching power supply circuit is configured as follows: "A second current detection resistor is provided between the input stage of the overcurrent detection circuit and the first current detection resistor, and an output detection circuit that detects a drop in output voltage and a current source that supplies a bias current to the second current detection resistor depending on the detection result of the output detection circuit are provided, and when a drop in output voltage due to the output current limiting operation of the overcurrent detection circuit is detected by the output detection circuit, the current source is caused to supply a bias current to the second current detection resistor, and the output current limiting state by the overcurrent detection circuit is changed."

[0003] Incidentally, electrical losses occur when power semiconductor elements with switching functions are driven. These losses are divided into switching losses and surge losses. When focusing on surge losses, control differs between the start of a voltage transition and near the end of the voltage transition. To minimize losses when driving power semiconductor elements, it is effective to control the power semiconductor elements with a high slew rate at the start of a voltage transition that does not contribute to the surge, and to switch to a low slew rate near the end of a voltage transition that does contribute to the surge. The high or low slew rate means changing the amount of change in the output voltage of the operational amplifier in the drive circuit of the power semiconductor element, i.e., the rate of change in the input voltage. This method of driving power devices by varying the slew rate is known as active gate control.

[0004] If a drive capacity different from the expected is set for a power device, it may increase losses and cause deterioration of the power device's characteristics or failure. A drive capacity different from the expected state occurs when the gate voltage of the power device is outside the set range. The rate of change of the input voltage, the timing of the input, and other factors can also result in a drive capacity different from the expected state. Therefore, active gate control requires highly precise control of the drive capacity supplied to the power device.

[0005] One method of implementing active gate control is the constant current drive method. The constant current drive method is said to enable more precise control than the constant voltage drive method. The constant voltage drive method is less precise because it is significantly affected by variations in switching elements. However, the constant current drive method generally requires more complex control than the constant voltage drive method. For this reason, with the constant current drive method, it is necessary to check whether the drive capacity is controlled as expected.

[0006] JP 2015-216763 A

[0007] The technology described in Patent Document 1 addresses the drop in output voltage by controlling the output current limit state to change when the output voltage drops due to the output current limit operation of the power semiconductor element. However, it is not possible to confirm whether the drive capacity of the power semiconductor element has been controlled as expected.

[0008] The present invention has been made in view of the above situation, and aims to make it possible to reliably confirm whether the driving capacity of a power semiconductor element has been controlled as expected.

[0009] To solve the above problems, one aspect of the present invention provides a gate drive device that includes a constant current drive circuit for controlling a drive current applied to a gate terminal of a gate-drive-type power semiconductor element based on a predetermined reference voltage, and a diagnostic circuit for diagnosing whether or not the constant current drive circuit is malfunctioning. The constant current drive circuit generates a constant drive current by applying a negative feedback voltage, which is a constant voltage controlled by negative feedback, to a reference resistor. The diagnostic circuit compares a diagnostic voltage corresponding to the reference voltage with the negative feedback voltage, and diagnoses whether or not the constant current drive circuit is malfunctioning based on the comparison result.

[0010] According to at least one aspect of the present invention, by diagnosing the presence or absence of an abnormality in the constant current drive circuit based on the result of comparing the diagnostic voltage corresponding to the reference voltage with the negative feedback voltage, it is possible to reliably confirm whether the drive capacity for the power semiconductor element is controlled as expected. Other problems, configurations, and effects will become clear from the following description of the embodiment of the present invention.

[0011] FIG. 1 is a circuit diagram showing an example of the configuration of a gate drive device according to a first embodiment of the present invention. FIG. 2 is a circuit diagram showing an example of the configuration of a gate drive device according to a second embodiment of the present invention. FIG. 3 is a circuit diagram showing an example of the configuration of a gate drive device according to a third embodiment of the present invention. FIG. 4 is a circuit diagram showing an example of the configuration of a gate drive device according to a fourth embodiment of the present invention. FIG. 5 is a diagram showing an example of switching of diagnostic voltages and expected values ​​of comparison results in a fifth embodiment of the present invention. FIG. 6 is a circuit diagram showing an example of the configuration of a gate drive device according to a sixth embodiment of the present invention. FIG. 7 is a diagram showing a first example of diagnosis by the gate drive device according to the sixth embodiment of the present invention. FIG. 8 is a diagram showing a second example of diagnosis by the gate drive device according to the sixth embodiment of the present invention.

[0012] Hereinafter, examples of modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described with reference to the accompanying drawings. In this specification and the accompanying drawings, identical or similar components are given the same reference numerals, and redundant explanations may be omitted or only explanations focusing on the differences may be given. Furthermore, when there are multiple identical or similar components, they may be described using the same reference numerals with different subscripts. Note that when it is not necessary to distinguish between these multiple components, the subscripts may be omitted in the description. The number of each component may be singular or plural unless otherwise specified.

[0013] First Embodiment First, a gate driving device according to a first embodiment of the present invention and an electronic control device using the same will be described with reference to FIG.

[0014] FIG. 1 is a circuit diagram showing an example of the configuration of a gate driver according to a first embodiment of the present invention. In FIG. 1, an electronic control device 100 includes a semiconductor integrated circuit 300 and a semiconductor integrated circuit 400 for driving a semiconductor element 200. The load is an EV (Electric Vehicle) motor or the like. The electronic control device 100 is an electronic control unit (ECU) having an MCU 500. The MCU 500 controls the semiconductor integrated circuit 300 and the semiconductor integrated circuit 400 via low-voltage and high-voltage isolations 601 to 604.

[0015] The MCU 500 and the semiconductor integrated circuits 300, 400 are electrically isolated by isolations 601 to 604. The isolations 601 to 604 have their input and output sides magnetically coupled, and transmit signals while maintaining electrical isolation between the input and output sides. Signals are exchanged between the MCU 500 and the semiconductor integrated circuits 300, 400 via the isolations 601 to 604. Examples of the isolations 601 to 604 include a signal transmission section using magnetic coupling with a transformer and an optical signal transmission section using a photocoupler.

[0016] The semiconductor element 200 is an example of a gate-driven power device that supplies power to a load. As an example, an n-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) power semiconductor element is used for the semiconductor element 200. Instead of the n-channel MOSFET, a p-channel MOSFET may also be used.

[0017] The semiconductor integrated circuit 300 and the semiconductor integrated circuit 400 are each an example of a gate driver that supplies a control signal (drive current) to the gate terminal of the semiconductor element 200 to control the drive of the semiconductor element 200. The semiconductor integrated circuit 300 and the semiconductor integrated circuit 400 alternately switch on and off. The semiconductor integrated circuit 300 is an example of a circuit that has a constant current circuit 301 and a diagnostic circuit 302 for turning on the semiconductor element 200 with a constant current drive and detecting an abnormality in the semiconductor integrated circuit 300 itself during the turn-on operation. The semiconductor integrated circuit 400 is an example of a circuit that has a constant current circuit 401 and a diagnostic circuit 402 for turning off the semiconductor element 200 with a constant current drive and detecting an abnormality in the semiconductor integrated circuit 400 itself during the turn-off operation.

[0018] [Semiconductor Integrated Circuit (Upper Arm Side)] The semiconductor integrated circuit 300 has an operational amplifier 31, a transistor 32, a resistor 33, a DC voltage source 34, and a comparator 35. The operational amplifier 31, the transistor 32, the resistor 33, and the DC voltage source 34 configure a constant current circuit 301 that drives the gate of the semiconductor element 200 with a constant current through negative feedback operation.

[0019] The constant current circuit 301 (an example of a constant current drive circuit) is a circuit for driving the gate terminal of the semiconductor element 200 on or off based on a predetermined reference voltage. The constant current circuit 301 generates a constant current by applying a negative feedback voltage, which is a constant voltage controlled by negative feedback, to a resistor 33, which is a reference resistor.

[0020] The transistor 32 is a switching element made of a semiconductor element, such as an n-channel MOSFET. The source terminal of the transistor 32 is connected to a power supply that supplies the power supply voltage VCC via a resistor 33. The drain terminal is connected to the gate terminal of the semiconductor element 200 and the drain terminal of the transistor 42 of the semiconductor integrated circuit 400. The gate terminal of the transistor 32 is connected to the output terminal of the operational amplifier 31.

[0021] The positive terminal (non-inverting input terminal) of the operational amplifier 31 is connected to the negative electrode of the DC voltage source 34 , and the negative terminal (inverting input terminal) is connected to the source terminal of the transistor 32 and the positive terminal of the comparator 35 .

[0022] The positive terminal of DC voltage source 34 is connected to a power source that supplies power supply voltage VCC. DC voltage source 34 generates reference voltage Vref from power supply voltage VCC. The voltage value of reference voltage Vref generated by DC voltage source 34 is set by MCU 500. DC voltage source 34 changes reference voltage Vref based on the setting by MCU 500.

[0023] The comparator 35 constitutes a diagnostic circuit 302 for diagnosing the negative feedback operation of the constant current circuit 301. The comparator 35 has a positive terminal (non-inverting input terminal) connected to the negative feedback voltage 36 and a negative terminal (inverting input terminal) connected to the diagnostic voltage V ｄｉａｇＯＮ are input respectively. Diagnostic voltage V ｄｉａｇＯＮ is the upper limit (upper limit threshold voltage) that can be tolerated for the negative feedback voltage 36 with respect to the reference voltage Vref of the DC voltage source 34 when the semiconductor device 200 is turned on. ｄｉａｇＯＮ is preferably generated from a voltage source independent of the reference voltage Vref, but is not limited to this configuration.

[0024] The comparator 35 detects that the negative feedback voltage 36 is a diagnostic voltage V ｄｉａｇＯＮ If the diagnostic voltage V is greater than 0.001V, an error signal (high level) is transmitted to the MCU 500 via the isolation 601. ｄｉａｇＯＮis set to a voltage value that differs from the reference voltage Vref by a predetermined value (for example, about 5%). The comparator 35 outputs an error signal indicating an abnormality in the constant current circuit 301 when the negative feedback voltage 36 differs from the reference voltage Vref by more than a predetermined value.

[0025] [Semiconductor Integrated Circuit (Lower Arm Side)] The semiconductor integrated circuit 400 has an operational amplifier 41, a transistor 42, a resistor 43, a DC voltage source 44, and a comparator 45. The operational amplifier 41, the transistor 42, the resistor 43, and the DC voltage source 44 configure a constant current circuit 401 that drives the gate of the semiconductor element 200 with a constant current through negative feedback operation.

[0026] The constant current circuit 401 (an example of a constant current drive circuit) is a circuit for driving the gate terminal of the semiconductor element 200 on or off based on a predetermined reference voltage. The constant current circuit 401 generates a constant current by applying a negative feedback voltage, which is a constant voltage controlled by negative feedback, to a resistor 43, which is a reference resistor.

[0027] The transistor 42 is a switching element made of a semiconductor element, such as a p-channel MOSFET. The source terminal of the transistor 42 is connected to a power supply that supplies the power supply voltage VEE via a resistor 43. The drain terminal is connected to the gate terminal of the semiconductor element 200 and the drain terminal of the transistor 32 of the semiconductor integrated circuit 300. The gate terminal of the transistor 42 is connected to the output terminal of the operational amplifier 41.

[0028] The positive terminal (non-inverting input terminal) of the operational amplifier 41 is connected to the positive electrode of the DC voltage source 44 , and the negative terminal (inverting input terminal) is connected to the source terminal of the transistor 42 and the positive terminal of the comparator 45 .

[0029] The negative terminal of DC voltage source 44 is connected to a power source that supplies power supply voltage VEE. DC voltage source 44 generates reference voltage Vref from power supply voltage VEE. The voltage value of reference voltage Vref generated by DC voltage source 44 is set by MCU 500. DC voltage source 44 changes reference voltage Vref based on the setting by MCU 500. The reference voltage Vref generated by DC voltage source 44 and the reference voltage Vref generated by DC voltage source 34 have the same or similar voltage values, but reference voltage Vref is set according to the state of each semiconductor integrated circuit.

[0030] The comparator 45 constitutes a diagnostic circuit 402 for diagnosing the negative feedback operation of the constant current circuit 401. The comparator 45 has a positive terminal (non-inverting input terminal) connected to a negative feedback voltage 46 and a negative terminal (inverting input terminal) connected to a diagnostic voltage V ｄｉａｇＯＦＦ are input respectively. Diagnostic voltage V ｄｉａｇＯＦＦ is the upper limit (upper limit threshold voltage) that can be tolerated for the negative feedback voltage 46 with respect to the reference voltage Vref of the DC voltage source 44 when the semiconductor device 200 is turned off. ｄｉａｇＯＦＦ is preferably generated from a voltage source independent of the reference voltage Vref, but is not limited to this configuration.

[0031] The comparator 45 detects whether the negative feedback voltage 46 is a diagnostic voltage V ｄｉａｇＯＦＦ If the diagnostic voltage V is greater than 0.001V, an error signal (High level) is transmitted to the MCU 500 via the isolation 604. ｄｉａｇＯＦＦ is set to a voltage value that is different from the reference voltage Vref by a predetermined value (for example, about 5%). When the negative feedback voltage 46 is different from the reference voltage Vref by a predetermined value or more, the comparator 45 outputs an error signal indicating an abnormality in the constant current circuit 401. In this specification, the diagnostic voltage V ｄｉａｇＯＮ and diagnostic voltage V ｄｉａｇＯＦＦ When no distinction is made between the diagnostic voltage V ｄｉａｇ "

[0032] The MCU 500 sets the reference voltage Vref for the negative feedback operation generated by the DC voltage source 34 of the semiconductor integrated circuit 300 and the DC voltage source 44 of the semiconductor integrated circuit 400 in order to turn on or off the semiconductor element 200 .

[0033] Furthermore, upon receiving an error signal from the comparators 35, 45 of the diagnostic circuits 302, 402, the MCU 500 determines that the constant current circuits 301, 401 are abnormal. In response to the error signal from the semiconductor integrated circuits 300, 400, the MCU 500 controls the semiconductor element 200 by limiting or stopping its operation, or by transitioning it to a different drive mode, in order to prevent the semiconductor element 200 from failing or increasing its loss due to driving at an incorrect drive capacity. For example, the MCU 500 may limit the output of the EV motor by limiting the operation of the semiconductor element 200, or transition it to a safety mode. In parallel with these controls, the MCU 500 may also output a warning or other message to a display device or the like within the vehicle in which the electronic control unit 100 is installed.

[0034] The MCU 500 (an example of a control unit) is a microcontroller that performs arithmetic processing and is an example of a control computer. In the MCU 500, a processing unit (e.g., a CPU), a storage unit (RAM and ROM), an input / output circuit (I / O), a timer circuit, and the like are implemented in a single integrated circuit.

[0035] In the semiconductor integrated circuits 300 and 400, the transistors 32 and 42 are not limited to an n-channel MOS-p-channel MOS configuration, but may also be an n-channel MOS-n-channel MOS configuration or a p-channel MOS-p-channel MOS configuration.

[0036] As described above, the gate drive device (semiconductor integrated circuit 300, 400) according to this embodiment includes a constant current drive circuit (constant current circuit 301, 401) for controlling the drive current flowing through the gate terminal of the gate-drive type power semiconductor element (semiconductor element 200) based on a predetermined reference voltage (Vref), and a diagnostic circuit (diagnostic circuit 302, 402) for diagnosing the presence or absence of an abnormality in the constant current drive circuit. The constant current drive circuit is a circuit that generates a constant drive current by applying a negative feedback voltage (36, 46), which is a constant voltage controlled by negative feedback, to a reference resistor (resistor 33, 43). The diagnostic circuit generates a diagnostic voltage (V ｄｉａｇＯＮ , V ｄｉａｇＯＦＦ) and the negative feedback voltage (36, 46), and based on the comparison result, the presence or absence of an abnormality in the constant current drive circuit is diagnosed.

[0037] This constant current drive circuit has a gate control element (transistor 32, 42) connected to the gate terminal of the power semiconductor element, a reference resistor (resistor 33, 43) connected between the gate control element and a power supply that supplies a power supply voltage (power supply voltage VCC, VEE) to the gate control element, and a differential amplifier (operational amplifier 31, 41) that drives the gate control element based on the result of comparing a negative feedback voltage corresponding to the drive current with a reference voltage.

[0038] (Effects) Conventional constant current drive systems lack a drive capacity diagnostic function, making it impossible to determine whether a power device is being controlled with the expected drive capacity. In contrast, the gate drive device of this embodiment compares a diagnostic voltage Vdiag, equivalent to a reference voltage Vref, with the negative feedback voltage of the constant current drive circuit to diagnose whether or not there is an abnormality in the constant current drive circuit, thereby resolving the conventional problems. In other words, this embodiment can reliably confirm whether the drive capacity for the power semiconductor element is being controlled as expected. In particular, when the upper limit of the negative feedback voltage is defined by the diagnostic voltage, it is possible to check for excessive drive by the constant current drive circuit.

[0039] Therefore, when an abnormality is detected, the gate drive device according to this embodiment can prevent breakdowns or increased losses in the power device due to driving at an incorrect driving capacity by limiting, stopping, or switching to a different driving mode of the power device, or by issuing a warning, etc. (From the inverter's perspective) In particular, when the upper limit of the negative feedback voltage is defined by the diagnostic voltage, excessive driving by the constant current drive circuit can be checked.

[0040] Second Embodiment As a second embodiment of the present invention, an example in which a DC voltage source for generating a diagnostic voltage is provided in the gate drive device according to the first embodiment will be described with reference to FIG.

[0041] 2 is a circuit diagram showing an example of the configuration of a gate driver according to the second embodiment. In the gate driver (semiconductor integrated circuit 400A) shown in FIG. 2, components with the same reference numerals as those in the semiconductor integrated circuit 400 (FIG. 1) of the first embodiment have the same functions, and therefore descriptions thereof will be omitted. Here, only the semiconductor integrated circuit 400A on the turn-off side is shown, and the description of the turn-on side is omitted. This embodiment is similarly applicable to the semiconductor integrated circuit 300 on the turn-on side, and therefore should not be interpreted as being limited to the semiconductor integrated circuit 400A.

[0042] The semiconductor integrated circuit 400A differs from the semiconductor integrated circuit 400 shown in FIG. 1 in that it generates a diagnostic voltage V ｄｉａｇＯＦＦ The comparator 45 and the DC voltage source 47 constitute a diagnostic circuit 402A for diagnosing the negative feedback operation of the constant current circuit 401.

[0043] A negative feedback voltage 46 is input to the positive terminal of the comparator 45. A diagnostic voltage V generated by a DC voltage source 47 independent of the reference voltage Vref is input to the negative terminal of the comparator 45. ｄｉａｇＯＦＦ is input. Diagnostic voltage V ｄｉａｇＯＦＦ is the upper limit threshold voltage for diagnosing the negative feedback voltage 46 at the time of turn-off. ｄｉａｇＯＦＦ The upper limit threshold voltage is generated from a DC voltage source 47 that is independent of the reference voltage Vref of the negative feedback operation by the DC voltage source 44.

[0044] The diagnostic voltage V generated by the DC voltage source 47 ｄｉａｇＯＦＦ may be configured to be used not only for the turn-off side semiconductor integrated circuit 400A but also for the turn-on side semiconductor integrated circuit 300. In this way, the DC voltage source 47 can be shared by the turn-on side and turn-off side semiconductor integrated circuits, thereby suppressing an increase in the circuit scale of the electronic control device.

[0045] (Effects) In conventional configurations, the diagnostic voltage is generated by, for example, dividing the reference voltage for current drive. Therefore, if the reference voltage is abnormal, the diagnostic voltage also fluctuates, raising concerns about erroneous diagnosis. In contrast, in the gate driver (e.g., semiconductor integrated circuit 400A) according to this embodiment, the diagnostic voltage Vdiag used in the diagnostic circuit (diagnostic circuit 402A) is generated from a voltage source (DC voltage source 47) independent of the reference voltage Vref, making it possible to diagnose abnormalities in the reference voltage Vref. In this way, the gate driver according to this embodiment can also diagnose faults within the semiconductor integrated circuit, such as diagnosing the reference voltage Vref and the presence or absence of an abnormality in the constant current drive circuit. Therefore, this embodiment can increase diagnostic coverage from the perspective of functional safety, i.e., broaden the diagnostic range (from the perspective of the IC).

[0046] In this embodiment, the diagnostic voltage Vdiag is generated from a voltage source independent of the reference voltage Vref, allowing for dynamic control of the diagnostic voltage Vdiag. This allows for diagnosis under multiple conditions using the diagnostic voltage Vdiag. This will be described in detail in the fifth embodiment below.

[0047] Third Embodiment As a third embodiment of the present invention, an example in which the lower limit value allowed for the negative feedback voltage in the gate drive device according to the first embodiment is defined by a diagnostic voltage will be described with reference to FIG.

[0048] FIG. 3 is a circuit diagram showing an example of the configuration of a gate driver according to a third embodiment. In the gate driver (semiconductor integrated circuit 400B) shown in FIG. 3, components with the same reference numerals as those in the semiconductor integrated circuit 400 (FIG. 1) of the first embodiment have the same functions, and therefore descriptions thereof will be omitted. Here, only the semiconductor integrated circuit 400B on the turn-off side is shown, and the description of the turn-on side is omitted. This embodiment is similarly applicable to the semiconductor integrated circuit 300 on the turn-on side, and therefore should not be interpreted as being limited to the semiconductor integrated circuit 400B.

[0049] The semiconductor integrated circuit 400B includes a comparator 48 instead of the comparator 45. The comparator 48 constitutes a diagnostic circuit 402B for diagnosing the negative feedback operation of the constant current circuit 401 that is configured with the operational amplifier 41, the transistor 42, the resistor 43, and the DC voltage source 44.

[0050] The negative feedback voltage 46 is input to the negative terminal of the comparator 48. The positive terminal of the comparator 48 receives the diagnostic voltage V ｄｉａｇＬ is input. Diagnostic voltage V ｄｉａｇＬ is the diagnostic voltage V ｄｉａｇ It is a type of diagnostic voltage V ｄｉａｇＬ is the lower limit (lower limit threshold voltage) that can be tolerated for the negative feedback voltage 46 with respect to the reference voltage Vref of the DC voltage source 44 when the semiconductor device 200 is turned off. ｄｉａｇＬ can be set to a value that is about 5% smaller than the reference voltage Vref (reference voltage Vref×0.95).

[0051] The comparator 48 detects whether the negative feedback voltage 46 is a diagnostic voltage V ｄｉａｇＬ If the diagnostic voltage V is smaller than the threshold voltage V, an error signal (High level) is transmitted to the MCU 500. ｄｉａｇＬ is preferably generated from a voltage source independent of the reference voltage Vref, but is not limited to this configuration.

[0052] As described above, in the gate driver (for example, the semiconductor integrated circuit 400B) according to this embodiment, the diagnostic circuit (diagnostic circuit 402B) detects the negative feedback voltage (46) as the lower limit threshold voltage (V ｄｉａｇＬ ) and, if the negative feedback voltage is smaller than the diagnostic voltage, outputs a signal indicating an abnormality in the constant current drive circuit.

[0053] (Effects) In the gate driving device according to this embodiment, a diagnostic voltage (V ｄｉａｇＬ) and a negative feedback voltage (46) is input to the negative terminal. This allows the lower limit of the negative feedback voltage to be determined by the diagnostic voltage, and if the negative feedback voltage falls below the lower limit, it can be determined that the constant current drive circuit is abnormal. Therefore, this embodiment can check for insufficient drive capacity of the constant current drive circuit.

[0054] Fourth Embodiment As a fourth embodiment of the present invention, an example in which a window comparator is used in the diagnostic circuit in the gate driver according to the first embodiment will be described with reference to FIG.

[0055] FIG. 4 is a circuit diagram showing an example of the configuration of a gate driver according to a fourth embodiment. In the gate driver (semiconductor integrated circuit 400C) shown in FIG. 4, components with the same reference numerals as those in the semiconductor integrated circuit 400 (FIG. 1) of the first embodiment have the same functions, and therefore descriptions thereof will be omitted. Here, only the semiconductor integrated circuit 400C on the turn-off side is shown, and the description of the turn-on side is omitted. This embodiment is similarly applicable to the semiconductor integrated circuit 300 on the turn-on side, and therefore should not be interpreted as being limited to the semiconductor integrated circuit 400C.

[0056] The semiconductor integrated circuit 400C includes a window comparator 49 instead of the comparator 45. The window comparator 49 constitutes a diagnostic circuit 402C for diagnosing the negative feedback operation of the constant current circuit 401 that is configured with the operational amplifier 41, the transistor 42, the resistor 43, and the DC voltage source 44. The window comparator 49 is configured with a comparator 491, a comparator 492, and an OR circuit 493 that calculates the logical OR of the outputs of the two comparators.

[0057] The positive terminal of the comparator 491 is connected to the negative feedback voltage 46, and the negative terminal is connected to the diagnostic voltage V ｄｉａｇＨ are input respectively. Diagnostic voltage V ｄｉａｇＨ is the upper limit (upper limit threshold voltage) that can be tolerated for the negative feedback voltage 46 with respect to the reference voltage Vref of the DC voltage source 44 when the semiconductor device 200 is turned off. On the other hand, the negative feedback voltage 46 is applied to the negative terminal of the comparator 492, and the diagnostic voltage V ｄｉａｇＬ are input respectively. Diagnostic voltage V ｄｉａｇＬis the lower limit (lower limit threshold voltage) that is allowable for the negative feedback voltage 46 with respect to the reference voltage Vref of the DC voltage source 44 when the semiconductor device 200 is turned off.

[0058] The outputs of the comparators 491 and 492 are ORed by an OR circuit 493. As a result, the OR circuit 493 determines whether the negative feedback voltage 46 is equal to or lower than the upper limit diagnostic voltage V ｄｉａｇＨ or the lower limit of the diagnostic voltage V ｄｉａｇＬ If the diagnostic voltage V is smaller than the threshold voltage V, an error signal (high level) is transmitted to the MCU 500 via the isolation 604. ｄｉａｇＨ and diagnostic voltage V ｄｉａｇＬ When no distinction is made between the diagnostic voltage V ｄｉａｇ "

[0059] As described above, in the gate driver (for example, the semiconductor integrated circuit 400C) according to this embodiment, the diagnostic circuit (diagnostic circuit 402C) has a window comparator (window comparator 49). The diagnostic circuit uses the window comparator to detect the first diagnostic voltage (V ｄｉａｇＨ ) and a second diagnostic voltage (V ｄｉａｇＬ ) (for example, about the reference voltage Vref±5%), and if the negative feedback voltage is not within the range between the first diagnostic voltage and the second diagnostic voltage, a signal indicating an abnormality in the constant current drive circuit is output.

[0060] (Effects) In the gate driver according to this embodiment, two types of diagnostic voltages are provided, and two comparators (comparators 491, 492) are also provided for comparing the negative feedback voltage with the respective diagnostic voltages. The two types of diagnostic voltages are set as upper and lower threshold voltages, respectively, and the negative feedback voltage is compared with each of the upper and lower threshold voltages, thereby determining whether the negative feedback voltage is within the range (normal range) between the upper and lower threshold voltages. This enables the gate driver according to this embodiment to simultaneously diagnose both overdriving and insufficient drive capacity, improving diagnostic accuracy.

[0061] Fifth Embodiment As a fifth embodiment of the present invention, an example in which the diagnostic voltage is dynamically changed in the gate drive device according to the second embodiment will be described with reference to FIG.

[0062] 5 is a diagram showing an example of switching of the diagnostic voltage and expected values ​​of the comparison result in the fifth embodiment. In FIG. 5, the horizontal axis represents time, and the vertical axis represents the diagnostic voltage V ｄｉａｇＯＦＦ and negative feedback voltage. In this embodiment, components with the same reference numerals as those in the semiconductor integrated circuit 400A (FIG. 2) in the second embodiment have the same functions, and therefore descriptions thereof will be omitted. This embodiment can also be applied to a semiconductor integrated circuit on the turn-on side, and therefore should not be interpreted as being limited to the semiconductor integrated circuit 400A on the turn-off side.

[0063] In this embodiment, the diagnostic voltage V generated by the DC voltage source 47 of the semiconductor integrated circuit 400A is ｄｉａｇＯＦＦ For example, as shown in FIG. 5, the diagnostic voltage V ｄｉａｇＯＦＦ is the diagnostic voltage V, which is the upper threshold of the negative feedback voltage 46. ｄｉａｇＨ and the lower threshold diagnostic voltage V ｄｉａｇＬ It is changed to two values.

[0064] Then, the negative feedback voltage 46 becomes the upper threshold diagnostic voltage V ｄｉａｇＨ and the lower threshold diagnostic voltage V ｄｉａｇＬ If the voltage is within the range of V ｄｉａｇＯＦＦ is the diagnostic voltage V ｄｉａｇＨ , the output of the comparator 45 is at a low level. ｄｉａｇＯＦＦ is the lower threshold diagnostic voltage V ｄｉａｇＬ In this embodiment, when the diagnostic voltage V ｄｉａｇＨ and diagnostic voltage V ｄｉａｇＬ It is sufficient to obtain the output information of the comparator 45 for the above two points.

[0065] In this way, the diagnostic voltage V of the DC voltage source 47 ｄｉａｇＯＦＦand the output of the comparator 45, it is possible to diagnose whether the negative feedback voltage 46 is within the range of the set upper and lower thresholds using a single comparator 45. Furthermore, because the output of the comparator 45 changes between a high level and a low level, it is also possible to diagnose whether the comparator 45 itself is stuck at high or low. A stuck at high level is an event in which the output of the comparator 45 does not return to a low level regardless of the input, and a stuck at low is an event in which the output of the comparator 45 does not return to a high level.

[0066] As described above, in the gate driver according to this embodiment (for example, the semiconductor integrated circuit 400A), the diagnostic voltage (V ｄｉａｇＯＦＦ ) is generated from a voltage source (DC voltage source 47) independent of the reference voltage (Vref) of the constant current drive circuit (constant current circuit 401). The diagnostic circuit (diagnostic circuit 402A) generates a negative feedback voltage (46) and a diagnostic voltage (V ｄｉａｇＯＦＦ The diagnostic circuit has a comparator (comparator 45) to which the diagnostic voltage is input. The diagnostic circuit then calculates the diagnostic voltage over time to a first diagnostic voltage (V ｄｉａｇＨ ) and a second diagnostic voltage (V ｄｉａｇＬ ) and the presence or absence of an abnormality in the constant current drive circuit is diagnosed from the change in the comparator output when the voltage is switched between them.

[0067] (Effects) In the gate driver according to this embodiment, the diagnostic voltage is dynamically changed so as to straddle the expected value of the negative feedback voltage, like an upper threshold and a lower threshold, and the output of the diagnostic circuit comparator is determined to be changing as expected. This allows a single comparator to diagnose both the upper and lower limits of the negative feedback voltage.

[0068] Furthermore, the output of the comparator of the diagnostic circuit (the result of comparing the negative feedback voltage with the diagnostic voltage) changes between high and low levels by dynamically changing the diagnostic voltage, which enables diagnosis of the diagnostic circuit itself, such as detecting whether the diagnostic circuit is stuck high or stuck low.

[0069] Sixth Embodiment As a sixth embodiment of the present invention, an example in which a negative feedback voltage is converted into digital data in the gate driver according to the first embodiment will be described with reference to FIG.

[0070] FIG. 6 is a circuit diagram showing an example of the configuration of a gate driver according to a sixth embodiment. In the gate driver (semiconductor integrated circuit 400D) shown in FIG. 6, components with the same reference numerals as those in the semiconductor integrated circuit 400 (FIG. 1) of the first embodiment have the same functions, and therefore descriptions thereof will be omitted. Here, only the semiconductor integrated circuit 400D on the turn-off side is shown, and the description of the turn-on side is omitted. This embodiment is similarly applicable to the semiconductor integrated circuit 300 on the turn-on side, and therefore should not be interpreted as being limited to the semiconductor integrated circuit 400D.

[0071] The semiconductor integrated circuit 400D includes an analog-to-digital converter (ADC) 61 instead of the comparator 45. The ADC 61 is a circuit for converting the input analog negative feedback voltage 46 into digital data. The ADC 61 receives a reference voltage V generated by a DC voltage source 62. ＡＤＣｒｅｆ The ADC 61 receives a reference voltage V ＡＤＣｒｅｆ As an example, the reference voltage V ＡＤＣｒｅｆ is DC 5 V. The DC voltage source 62 is a voltage source independent of the reference voltage Vref for negative feedback operation generated by the DC voltage source 44. The ADC 61 and the DC voltage source 62 constitute a diagnostic circuit 402D.

[0072] The digital data (digital value 63) of the negative feedback voltage 46 converted by the ADC 61 is transmitted to the MCU 500 via the isolation 604. Upon receiving the digital value 63, the MCU 500 executes arithmetic processing and diagnoses the negative feedback operation of the constant current circuit 401. The MCU 500 compares the digital value 63 of the negative feedback voltage 46 with upper and lower limit judgment thresholds (for example, within a few percent above and below the reference voltage Vref) stored in a storage device to make the diagnosis.

[0073] As described above, in the gate driver (for example, the semiconductor integrated circuit 400D) according to this embodiment, the diagnostic circuit (diagnostic circuit 402D) detects the voltage (V ref ) generated from the voltage source (DC voltage source 62) independent of the reference voltage (V ref ) of the constant current driver circuit (constant current circuit 401). ＡＤＣｒｅｆ The diagnostic circuit has an analog-to-digital converter (ADC 61) that uses the negative feedback voltage (46) as a reference. The diagnostic circuit converts the negative feedback voltage (46) into digital data (digital value 63) using the analog-to-digital converter and transmits the digital data of the negative feedback voltage to a control unit (MCU 500) that controls the operation of the gate drive device. The control unit then diagnoses whether or not there is an abnormality in the constant current drive circuit based on the digital data of the negative feedback voltage.

[0074] (Effects) In the gate drive device according to this embodiment, for example, data on the negative feedback voltage over time is stored, and if a variation from the initial value of a digital value exceeds an allowable range, it can be determined that this is a sign of a malfunction in the gate drive device. This improves the degree of freedom in diagnosis, and in addition to the same diagnoses as in the first to fifth embodiments, it also becomes possible to perform a malfunction sign diagnosis.

[0075] An example of diagnosis in the sixth embodiment will now be described with reference to Figures 6 and 7. However, the form of diagnosis in this embodiment is not limited to the example shown in Figures 6 and 7.

[0076] 7 is a diagram showing a first diagnostic example performed by the gate driver (semiconductor integrated circuit 400D) according to the sixth embodiment. In FIG. 7, the vertical axis represents the negative feedback voltage (digital value) at turn-off and the determination threshold value.

[0077] In the diagnosis example 71, an abnormality is determined by calculation using upper and lower limit thresholds set for the digital value 63 of the negative feedback voltage 46 converted into a digital value by the ADC 61 at the time of turn-off. The determination is based on calculation processing, and by using the upper limit threshold and / or the lower limit threshold stored in the storage device, it is possible to perform diagnoses equivalent to those in the first to fifth embodiments.

[0078] 8 is a diagram showing a second diagnostic example performed by the gate driver (semiconductor integrated circuit 400D) according to the sixth embodiment. In Fig. 8, the horizontal axis represents the elapsed time, and the vertical axis represents the negative feedback voltage (digital value) at turn-off and the allowable range of fluctuation.

[0079] In diagnostic example 72, time-series data of the digital value 63 of the negative feedback voltage 46 converted by the ADC 61 at turn-off is stored in a storage device or the like, and the amount of fluctuation in the digital value 63 from a certain point in the past (e.g., an initial value) is diagnosed. For example, the MCU 500 controls the ADC 61 to periodically acquire the digital value of the negative feedback voltage 46 using a timer function. If the amount of fluctuation exceeds a set allowable range, the MCU 500 determines that the constant current circuit 401 is abnormal or a sign of failure. Alternatively, if the rate of change of the time-series digital value 63 is greater than a preset value, it can be determined that the constant current circuit 401 is abnormal or a sign of failure.

[0080] If the MCU 500 determines that an abnormality or a sign of failure has occurred, it controls the operation of the semiconductor element 200 by limiting or stopping it, switching it to another drive mode, issuing a warning, etc. This makes it possible to prevent the semiconductor element 200 from breaking down or increasing losses due to driving it with an incorrect drive capacity.

[0081] As described above, the present invention is not limited to the above-described embodiments, and various other modifications and applications are possible without departing from the spirit of the invention as defined in the claims. For example, the above-described embodiments have been described in detail and specifically to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the components described. Furthermore, it is possible to replace part of the configuration of one embodiment with a component of another embodiment. It is also possible to add a component of another embodiment to the configuration of one embodiment. It is also possible to add, replace, or delete other components from part of the configuration of each embodiment.

[0082] Furthermore, some or all of the above-described configurations, functions, processing units, etc. may be implemented in hardware, for example, by designing them as integrated circuits, etc. As the hardware, a broad processor device such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) may be used.

[0083] In the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are interconnected.

[0084] 31, 41... operational amplifier, 32, 42... transistor, 33, 43... resistor, 34, 44... DC voltage source, 35, 45... comparator, 36, 46... negative feedback voltage, 47... DC voltage source, 48... operational amplifier, 49... window comparator, 49-1, 49-2... comparator, 49-3... logical sum circuit, 61... ADC, 62... DC voltage source, 71... first diagnostic example, 72... second diagnostic example, 100... electronic control device, 200... semiconductor element (power device), 300, 400 to 400D... semiconductor integrated circuit, 401... constant current circuit, 402... diagnostic circuit, 500... MCU, V ｄｉａｇＯＮ ... diagnostic voltage at turn-on (upper threshold voltage), V ｄｉａｇＯＦＦ ... diagnostic voltage at turn-off (upper threshold voltage), V ｄｉａｇＨ ... diagnostic voltage (upper threshold voltage), V ｄｉａｇＬ ...Diagnostic voltage (lower threshold voltage)

Claims

1. A gate drive device comprising: a constant current drive circuit for controlling a drive current flowing through a gate terminal of a gate-driven power semiconductor element based on a predetermined reference voltage; and a diagnostic circuit for diagnosing the presence or absence of an abnormality in the constant current drive circuit, wherein the constant current drive circuit is a circuit that generates the drive current, which is a constant current, by applying a negative feedback voltage, which is a constant voltage controlled by negative feedback, to a reference resistor, and the diagnostic circuit compares a diagnostic voltage equivalent to the reference voltage with the negative feedback voltage, and diagnoses the presence or absence of an abnormality in the constant current drive circuit based on the comparison result.

2. The gate driver according to claim 1, wherein the diagnostic voltage is a voltage generated from a voltage source independent of the reference voltage of the constant current drive circuit.

3. The gate drive device according to claim 2, wherein the diagnostic circuit determines whether the negative feedback voltage is greater than the diagnostic voltage set as a lower threshold, and outputs a signal indicating an abnormality in the constant current drive circuit if the negative feedback voltage is smaller than the diagnostic voltage.

4. The gate drive device according to claim 2, wherein the diagnostic circuit has a window comparator, and the diagnostic circuit uses the window comparator to determine whether the negative feedback voltage is within a range between a first diagnostic voltage set as an upper threshold and a second diagnostic voltage set as a lower threshold, and outputs a signal indicating an abnormality in the constant current drive circuit if the negative feedback voltage is not within the range between the first diagnostic voltage and the second diagnostic voltage.

5. The gate drive device according to claim 1, wherein the diagnostic voltage is generated from a voltage source independent of the reference voltage of the constant current drive circuit, the diagnostic circuit has a comparator to which the negative feedback voltage and the diagnostic voltage are input, and the diagnostic circuit diagnoses whether or not there is an abnormality in the constant current drive circuit from a change in the output of the comparator when the diagnostic voltage is switched over time between a first diagnostic voltage set as an upper threshold and a second diagnostic voltage set as a lower threshold.

6. The gate drive device according to claim 2, wherein the diagnostic circuit has an analog-to-digital converter that uses a voltage generated from a voltage source independent of the reference voltage of the constant current drive circuit as a reference, the diagnostic circuit converts the negative feedback voltage into digital data using the analog-to-digital converter and transmits the digital data of the negative feedback voltage to a control unit that controls the operation of the gate drive device, and the control unit diagnoses whether or not there is an abnormality in the constant current drive circuit based on the digital data of the negative feedback voltage.

7. The gate drive device according to claim 1, wherein the constant current drive circuit comprises: a gate control element connected to the gate terminal of the power semiconductor element; the reference resistor connected between the gate control element and a power supply that supplies a power supply voltage to the gate control element; and a differential amplifier that drives the gate control element based on a result of comparing the negative feedback voltage corresponding to the drive current with the reference voltage.

8. An electronic control device comprising: a gate drive device that drives a power semiconductor element; and a control unit that controls the operation of the gate drive device, wherein the gate drive device comprises: a constant current drive circuit for controlling a drive current flowing to a gate terminal of a gate-driven power semiconductor element based on a predetermined reference voltage; and a diagnostic circuit that diagnoses the presence or absence of an abnormality in the constant current drive circuit, wherein the constant current drive circuit is a circuit that generates the drive current, which is a constant current, by applying a negative feedback voltage, which is a constant voltage controlled by negative feedback, to a reference resistor, and the diagnostic circuit compares a diagnostic voltage equivalent to the reference voltage with the negative feedback voltage, and diagnoses the presence or absence of an abnormality in the constant current drive circuit based on the comparison result.

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