Inverter protection circuit, motor drive circuit, and motor control device

Abstract

It detects the occurrence of a ground fault and suppresses the spread of damage caused by the ground fault. [Solution] The motor drive circuit 2 includes an inverter circuit 4 equipped with a switching element that generates a drive voltage to be applied to the motor M, and an inverter protection circuit 1. The inverter protection circuit 1 includes a first resistor R1 connected between the inverter circuit 4 and a positive power supply line 7 that supplies a constant voltage to the inverter circuit 4, a first detection circuit 11 that outputs a first detection signal E1 indicating that a ground fault or inter-phase short circuit has been detected based on the current flowing through the first resistor R1, and a first protection circuit 12 that cuts off the supply of a signal for driving the switching element based on the first detection signal E1.

Description

Technical Field

[0006] , ,

[0005] , , , ,

[0001] The present invention relates to an inverter protection circuit, a motor drive circuit, and a motor control device.

Background Art

[0002] Some drive circuits that supply drive current to an electrical device include an inverter circuit that generates drive current using a switching element. Patent Document 1 describes a drive circuit of this type in which a resistor is arranged at a location where a ground fault current flows to detect the ground fault. Conventionally, some motor drive circuits incorporate a resistor for detecting a short circuit between phases.

[0003] In the drive circuit of Patent Document 1, the motor itself that supplies the drive current is not grounded, and the motor is grounded via the ground wire of the drive circuit. The resistor for detecting the ground fault current is connected to the ground wire that grounds the shield wire of the three-phase shield cable, which is the power cable for supplying the drive current. Thereby, when a ground fault occurs, the ground fault current returning to the three-phase shield cable via the ground wire is detected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When an electrical device such as a motor connected to the drive circuit is directly grounded via the frame of the electrical device itself, the ground fault current may not flow via the ground wire. Therefore, even if a resistor is arranged in the ground wire, the ground fault current may not be detected.​​​As mentioned above, some drive circuits incorporate resistors to detect inter-phase short circuits. While ground fault current can flow through the resistors that detect inter-phase short circuits, depending on the location of the ground fault, the resistors designed to detect inter-phase short circuits may not be able to detect the ground fault.

[0007] Figure 9 is a block diagram showing the arrangement of resistors for conventional phase-to-phase short-circuit detection. As shown in Figure 9, the resistor 101 for phase-to-phase short-circuit detection is located on the ground side of the inverter circuit 100. When a phase-to-phase short-circuit occurs, as shown in the upper part of Figure 9, a short-circuit current Is flows through the resistor 101 via the low-side switching element in the inverter circuit 100.

[0008] However, the resistor 101 shown in Figure 9 may not be usable for detecting ground faults. For example, if a ground fault occurs in the W-phase power cable, as shown in the lower part of Figure 9, a ground fault current Ig flows through the high-side switching element in the inverter circuit 100 to the power line that supplies a constant voltage to the inverter circuit 100, but no current flows on the ground wire side. Therefore, the ground fault cannot be detected.

[0009] When a ground fault or phase-to-phase short circuit occurs, elements in the area where a large current flows due to the short circuit are destroyed. If the inverter circuit continues to switch in this state, current will be supplied to the damaged elements, potentially causing the damage to spread further through explosions or other means.

[0010] In view of the above problems, the object of the present invention is to detect the occurrence of a ground fault and suppress the spread of damage caused by the ground fault. [Means for solving the problem]

[0011] To solve the above problems, one embodiment of the inverter protection circuit according to the present invention is characterized by comprising: a first resistor connected between an inverter circuit equipped with a switching element that generates a drive voltage to be applied to an electrical device and a positive power supply line that supplies a constant voltage to the inverter circuit; a first detection circuit that outputs a first detection signal based on the current flowing through the first resistor; and a first protection circuit that cuts off the supply of a signal for driving the switching element based on the first detection signal.

[0012] Next, the motor drive circuit according to the present invention is characterized by having the above-described inverter protection circuit.

[0013] Next, the motor control device according to the present invention is characterized by having the above-described motor drive circuit. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a block diagram showing a motor drive circuit equipped with an inverter protection circuit according to Embodiment 1, when connected to a motor. [Figure 2] Figure 2 is a block diagram showing the inverter protection circuit of Embodiment 1 when it is incorporated into a power module. [Figure 3] Figure 3 is a block diagram showing the motor drive circuit equipped with the inverter protection circuit of Embodiment 2 connected to a motor. [Figure 4] Figure 4 is a block diagram showing the inverter protection circuit of Embodiment 2 when it is incorporated into a power module. [Figure 5] Figure 5 is a block diagram showing the motor drive circuit equipped with the inverter protection circuit of Embodiment 3 connected to a motor. [Figure 6] Figure 6 is a block diagram showing the inverter protection circuit of Embodiment 3 when it is incorporated into a power module. [Figure 7] Figure 7 is a block diagram showing the motor drive circuit equipped with the inverter protection circuit of Embodiment 4 connected to a motor. [Figure 8]FIG. 8 is a block diagram showing a modified example of an element for cutting off power by an inverter protection circuit. [Figure 9] FIG. 9 is a block diagram showing the arrangement of conventional resistors for detecting phase - to - phase short - circuits.

Embodiments for Carrying out the Invention

[0015] Hereinafter, embodiments of an inverter protection circuit, a motor drive circuit including the inverter protection circuit, and a motor control device will be described with reference to the drawings.

[0016] (Embodiment 1) FIG. 1 is a block diagram showing the case where a motor drive circuit 2 including an inverter protection circuit 1 of Embodiment 1 is connected to a motor M. FIG. 1 shows the main part of the motor drive circuit 2. The motor M is a servo motor. The motor drive circuit 2 is incorporated in a motor control device 3 such as a servo amplifier, for example.

[0017] (Motor Drive Circuit) As shown in FIG. 1, the motor drive circuit 2 includes an inverter circuit 4 that generates a drive voltage for supplying to the coil of the motor M, a control element 5 that supplies a PWM signal for causing the inverter circuit 4 to perform a switching operation, and an isolator element 6 interposed between the control element 5 and the inverter circuit 4. The control element 5 is an IC chip such as a microcontroller, for example. The control element 5 outputs a PWM signal based on a control signal input from a higher - level device.

[0018] The inverter circuit 4 includes switching elements such as MOS type FETs (metal - oxide - semiconductor field - effect transistors), IGBTs (Insulated Gate Bipolar Transistors), for example. The isolator element 6 is an insulated gate driver, for example. The isolator element 6 includes an insulated signal transmission circuit and supplies a signal for turning on and off the gate of the switching element to the inverter circuit 4 based on the logic - level PWM signal supplied from the control element 5.

[0019] Here, in FIG. 1, the inverter circuit 4 is shown as one block. However, the inverter circuit 4 may be in any form, such as a form in which switching elements such as MOS-type FETs and IGBTs are mounted on a circuit board as discrete elements, or a form of a power module in which the switching elements are packaged into one unit. Note that, as will be described later, it is also possible to take a form in which an insulation gate driver and various protection circuits are included and packaged as an IPM (Intelligent Power Module).

[0020] The motor M is a three-phase motor. The motor drive circuit 2 outputs drive voltages of the U-phase, V-phase, and W-phase for applying to the U-phase coil, V-phase coil, and W-phase coil of the motor M from the inverter circuit ④. The inverter circuit 4 and the motor M are connected by a power cable. A part of the motor case, for example, a flange of the motor M is connected to the frame ground of the device frame that supports the motor M and is grounded. "GND" shown in the drawings of this specification means grounding.

[0021] A positive power supply line 7 for supplying a constant voltage to the switching element and a ground-side power supply line 8 are connected to the inverter circuit 4. The inverter circuit 4 converts the constant-voltage drive voltage supplied from the positive power supply line 7 into a three-phase AC drive voltage by switching of the switching element. The motor drive circuit 2 includes a smoothing capacitor 9 connected between the positive power supply line 7 and the ground-side power supply line 8 on the power supply side with respect to the inverter circuit 4. A smoothed DC voltage is supplied to the positive power supply line 7 by the smoothing capacitor 9.

[0022] (Inverter Protection Circuit) As shown in Figure 1, the motor drive circuit 2 includes an inverter protection circuit 1. The inverter protection circuit 1 includes a first resistor R1, a first detection circuit 11, and a first protection circuit 12. The first resistor R1 is connected between the positive power supply line 7 and the inverter circuit 4. The first resistor R1 is on the power supply side of the inverter circuit 4 and is positioned directly before the inverter circuit 4, and is connected in series with the inverter circuit 4 to the positive power supply line 7.

[0023] In the motor drive circuit 2, if a ground fault occurs, a ground fault current will always flow through the first resistor R1. The first detection circuit 11 can detect that a ground fault current has flowed through the first resistor R1 by detecting the voltage difference between the two points on either side of the first resistor R1. Specifically, it detects that a ground fault has occurred by detecting an increase in the voltage difference between the two points on either side of the first resistor R1. For example, in this embodiment, the first detection circuit 11 detects when the voltage difference between the two points on either side of the first resistor R1 exceeds a predetermined voltage difference.

[0024] In the motor drive circuit 2, even if a phase-to-phase short circuit occurs, a short-circuit current flows through the first resistor R1. Therefore, by detecting an increase in the voltage difference between the two points on either side of the first detection circuit 11, it is possible to detect that a phase-to-phase short circuit has occurred. The voltage difference when a phase-to-phase short circuit occurs is smaller than the voltage difference when a ground fault occurs. Therefore, as described above, it is not possible to distinguish between a phase-to-phase short circuit and a ground fault simply by determining the magnitude of the voltage difference. However, if the setting value for the voltage difference to be detected is set to a value that can detect both phase-to-phase short circuits and ground faults, it is possible to detect when either a phase-to-phase short circuit or a ground fault occurs. Even if a correlated short circuit or ground fault does not occur, setting the detection value to a low value intended for correlated short circuits will prevent detection failures.

[0025] The first detection circuit 11 outputs a first detection signal E1 based on the detected voltage difference when a ground fault or phase-to-phase short circuit occurs. The first detection circuit 11 includes a first photocoupler 13 equipped with a light-emitting element that emits light based on the current flowing through the first resistor R1, and a first latch circuit 14 that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the first photocoupler 13. The first latch circuit 14 outputs a first detection signal E1 of the required length by maintaining an ON state. In this embodiment, a first detection signal E1 with a length of 1 msec is output. The first detection signal E1 is input to the first protection circuit 12. The first detection signal E1 can be any length necessary to activate the circuit to which the first detection signal E is input. In this embodiment, the first protection circuit 12 requires a signal of at least 1 msec in length. Therefore, the first detection signal E1 only needs to be a signal of 1 msec or longer.

[0026] The first protection circuit 12 cuts off the supply of signals to drive the switching elements of the inverter circuit 4 based on the input of a first detection signal E1 from the first detection circuit 11 due to a ground fault or inter-phase short circuit. In this embodiment, the first protection circuit 12 immediately cuts off the power supply to the isolator element 6 based on the input of the first detection signal E1. For example, as shown in Figure 1, the power supply is cut off by directly inputting a signal F based on the first detection signal E1 to a switching element provided on the power line of the isolator element 6. As described above, since the isolator element 6 is an element to which a PWM signal is input from the control element 5, cutting off the power supply to the isolator element 6 cuts off the supply of gate drive signals to the inverter circuit 4.

[0027] In Figure 1, the power supply voltage for the isolator element 6 is set to 3.3V, but it is not limited to 3.3V. Furthermore, the switching element for interrupting the power supply to the isolator element 6 is not limited to a semiconductor switch as shown in Figure 1. For example, a mechanical relay can also be used. These points are also true for each embodiment described later in Embodiment 2 and subsequent embodiments.

[0028] Furthermore, the first protection circuit 12 stops the output of the PWM signal to the control element 5 based on the input of the first detection signal E1. For example, as shown in Figure 1, a signal F based on the first detection signal E1 is input to the control element 5. The control element 5 stops the output of the PWM signal based on the signal F. Furthermore, the control element 5 cuts off the power supply to the isolator element 6 based on the signal F and maintains that state. As a result, the motor drive circuit 2 maintains a state in which the switching operation of the inverter circuit 4 is stopped, and the supply of U-phase voltage, V-phase voltage, and W-phase voltage to the motor M is cut off.

[0029] Based on the signal F input from the first protection circuit 12, the control element 5 outputs an error signal to notify the outside of the occurrence of a ground fault or phase short circuit, in addition to stopping the output of the PWM signal and cutting off the power supply to the isolator element 6. This allows the display unit of the motor control device 3 to display information based on the error signal.

[0030] (Effects and Benefits) As described above, the inverter protection circuit 1 of Embodiment 1 includes a first resistor R1 connected between an inverter circuit 4 equipped with a switching element that generates a drive voltage applied to the motor M and a positive power supply line 7 that supplies a constant voltage to the inverter circuit 4, a first detection circuit 11 that outputs a first detection signal E1 based on the current flowing through the first resistor R1, and a first protection circuit 12 that cuts off the supply of a signal for driving the switching element based on the first detection signal E1.

[0031] Thus, in this embodiment, the first resistor R1 is placed in the motor drive circuit 2 at a location where a large current is reliably expected to flow when a ground fault or inter-phase short circuit occurs. This ensures reliable detection of ground faults and allows detection of both ground faults and inter-phase short circuits using a single resistor. Furthermore, the first protection circuit 12 cuts off the supply of signals for driving the switching elements based on the first detection signal E1, stopping the switching operation of the inverter circuit 4 and cutting off the supply of U-phase voltage, V-phase voltage, and W-phase voltage to the motor M. This prevents further switching operation from occurring while the element is damaged by a large current due to a ground fault or inter-phase short circuit, thus avoiding the damage being exacerbated by the explosion of the damaged element.

[0032] In this embodiment, the first protection circuit 12 cuts off the power supply to the isolator element 6 based on the first detection signal E1, and also stops the output of the PWM signal from the control element 5 based on the first detection signal E1. In this way, by the first protection circuit 12 directly cutting off the power supply to the isolator element 6, it is possible to avoid the escalation of damage caused by switching operation occurring between the time the control element 5 stops the PWM signal and the power supply to the isolator element 6 is cut off.

[0033] In this embodiment, the first detection circuit 11 includes a first photocoupler 13 equipped with a light-emitting element that emits light based on the current flowing through the first resistor R1, and a first latch circuit 14 that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the first photocoupler 13. Because the ON time of the photocoupler is short, it is not possible to output a signal of the required length, but by combining it with the latch circuit, it is possible to output a signal of the length required for the operation of the first protection circuit 12, for example, a signal of 1 msec in length.

[0034] (Integration of the inverter protection circuit of Embodiment 1 into the IPM) Figure 2 is a block diagram showing the inverter protection circuit 1A of Embodiment 1 incorporated into the IPM30. The IPM30 is a module that integrates switching elements such as MOS-type FETs and IGBTs that constitute the inverter circuit 4, and a gate drive circuit that drives and controls the switching elements, into a single package. As shown in Figure 2, each part that constitutes the inverter protection circuit 1A, and the isolator element 6 that provides the function of a gate drive circuit, can all be incorporated into the IPM30. In addition to protection circuits against ground faults and inter-phase short circuits, the IPM30 can also incorporate other protection circuits such as overheat protection.

[0035] As shown in Figure 2, the motor control device 3A includes a motor drive circuit 2A. The motor drive circuit 2A includes an inverter protection circuit 1A incorporated into the IPM 30. The inverter protection circuit 1A includes a first resistor R1, a first detection circuit 11, and a first protection circuit 12, similar to the inverter protection circuit 1 in Figure 1. The configurations of the first resistor R1, the first detection circuit 11, and the first protection circuit 12 have already been described.

[0036] Here, the inverter protection circuit 1 and the isolator element 6 can be fully incorporated into the IPM 30, or only some of the functions of the inverter protection circuit 1 and the isolator element 6 can be incorporated into the IPM 30. The parts to be incorporated can be selected as appropriate. For example, of the functions of the first protection circuit 12, only the function of directly shutting off the power supply to the isolator element 6 without going through the control element 5 can be incorporated into the IPM 30.

[0037] (Embodiment 2) Figure 3 is a block diagram showing the motor drive circuit 2B equipped with the inverter protection circuit 1B of Embodiment 2 connected to the motor M. The motor drive circuit 2B is incorporated into the motor control device 3B, similar to the above embodiment. As shown in Figure 3, the motor drive circuit 2B comprises an inverter circuit 4, a control element 5, an isolator element 6, and an inverter protection circuit 1B.

[0038] (Inverter protection circuit) The inverter protection circuit 1B includes a first resistor R1 and a first detection circuit 11, similar to the configuration described above. Furthermore, the inverter protection circuit 1B includes a second resistor R2 and a second detection circuit 21. The second resistor R2 is located between the inverter circuit 4 and the ground-side power supply line 8. The second resistor R2 is connected in series with the inverter circuit 4 to the ground-side power supply line 8.

[0039] In the motor drive circuit 2B, if a phase-to-phase short circuit occurs, a short-circuit current will always flow through the second resistor R2. The second detection circuit 21 detects that a short-circuit current has flowed through the second resistor R2 by detecting the voltage difference between the two points on either side of the second resistor R2. Specifically, it detects that a phase-to-phase short circuit has occurred by detecting an increase in the voltage difference between the two points on either side of the second resistor R2.

[0040] The second detection circuit 21 includes a second photocoupler 23 equipped with a light-emitting element that emits light based on the current flowing through the second resistor R2, and a second latch circuit 24 that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the second photocoupler 23. By maintaining the ON state, the second latch circuit 24 outputs a second detection signal E2 of the required length. In this embodiment, a second detection signal E2 with a length of 1 msec is output. By using the second latch circuit 24, a signal of the required length can be output.

[0041] The inverter protection circuit 1B includes a protection circuit 15 connected to the first detection circuit 11 and the second detection circuit 21. The protection circuit 15 cuts off the supply of signals for driving the switching elements of the inverter circuit 4 when at least one of the first detection signal E1 and the second detection signal E2 is input. Specifically, similar to the above configuration, the protection circuit 15 outputs a signal F to directly cut off the power supply to the isolator element 6. Furthermore, the signal F is input to the control element 5 to stop the output of the PWM signal and cut off the power supply to the isolator element 6, maintaining that state. As a result, the motor drive circuit 2B stops the switching operation of the inverter circuit 4 and cuts off the supply of U-phase voltage, V-phase voltage, and W-phase voltage to the motor M.

[0042] The protection circuit 15 includes an abnormality determination circuit that determines whether one or both of the first detection signal E1 and the second detection signal E2 are input. Based on the determination result of the abnormality determination circuit, it outputs signal F. If a ground fault occurs, the first detection signal E1 is input, and the second detection signal E2 is not input. On the other hand, if a phase-to-phase short circuit occurs, both the first detection signal E1 and the second detection signal E2 are input. Therefore, the protection circuit 15 outputs signal F when a ground fault or phase-to-phase short circuit occurs.

[0043] Based on the signal F input from the protection circuit 15, the control element 5 outputs an error signal to notify the outside of the occurrence of a ground fault or phase short circuit, in addition to the two processes described above. This allows the motor control device 3B's display unit to display information based on the error signal.

[0044] (Effects and Benefits) As described above, the inverter protection circuit 1B of Embodiment 2 includes a first resistor R1 connected between the inverter circuit 4 and the positive power supply line 7, a second resistor R2 connected between the inverter circuit 4 and the ground power supply line 8, a first detection circuit 11 that outputs a first detection signal E1 based on the current flowing through the first resistor R1, a second detection circuit 21 that outputs a second detection signal E2 based on the current flowing through the second resistor R2, and a protection circuit 15 connected to the first detection circuit 11 and the second detection circuit 21. The protection circuit 15 outputs a signal to drive the switching element when at least one of the first detection signal E1 and the second detection signal E2 is input. Cut off the supply.

[0045] In this configuration, ground faults can be detected by the first resistor R1, and phase-to-phase short circuits can be detected by the second resistor R2, making it easy to distinguish between ground faults and phase-to-phase short circuits. Furthermore, if either a ground fault or a phase-to-phase short circuit occurs, the supply of signals to drive the switching elements is interrupted, thereby stopping the switching operation of the inverter circuit 4 and interrupting the supply of U-phase voltage, V-phase voltage, and W-phase voltage to the motor M. Therefore, similar to the above configuration, it is possible to avoid further switching operation occurring in an element that has been damaged by a large current flowing through it due to a ground fault or phase-to-phase short circuit, which could result in current flowing through the damaged element and exacerbating the damage through explosion or other means.

[0046] Furthermore, similar to the above configuration, the protection circuit 15 directly cuts off the power supply to the isolator element 6, and in addition, it causes the control element 5 to stop outputting the PWM signal and cut off the power supply to the isolator element 6 from the control element 5. Therefore, it is possible to avoid the damage escalating due to switching operation occurring before the control element 5 stops the PWM signal and cuts off the power supply to the isolator element 6.

[0047] (Integration of the inverter protection circuit of Embodiment 2 into the IPM) Figure 4 is a block diagram showing the inverter protection circuit 1C of Embodiment 2 incorporated into the IPM 30C. As shown in Figure 4, the motor control device 3C includes a motor drive circuit 2C. The motor drive circuit 2C includes an inverter protection circuit 1C. All parts constituting the inverter protection circuit 1C, and the isolator element 6 that provides the function of a gate drive circuit, can be incorporated into the IPM 30C.

[0048] The configuration of the inverter protection circuit 1C is as described in the explanation of the inverter protection circuit 1B in Figure 3. The inverter protection circuit 1C may be entirely incorporated into the IPM30C, or only a portion of the functions of the inverter protection circuit 1B and the isolator element 6 may be incorporated into the IPM30C. The parts to be incorporated can be selected as appropriate, as in the case of Embodiment 1.

[0049] (Embodiment 3) Figure 5 is a block diagram showing the motor drive circuit 2D equipped with the inverter protection circuit 1D of Embodiment 3 connected to the motor M. The motor drive circuit 2D is incorporated into the motor control device 3D, as in the above embodiments. As shown in Figure 5, the motor drive circuit 2D comprises an inverter circuit 4, a control element 5, an isolator element 6, and an inverter protection circuit 1D.

[0050] (Inverter protection circuit) As shown in Figure 5, the inverter protection circuit 1D comprises a first resistor R1, a first detection circuit 11, and a first protection circuit 12, and a second resistor R2, a second detection circuit 21, and a second protection circuit 22. The arrangement of the first resistor R1 and the second resistor R2 is as described in each of the above embodiments. The first detection circuit 11 outputs a first detection signal E1 when a ground fault or inter-phase short circuit occurs. The second detection circuit 21 outputs a second detection signal E2 when an inter-phase short circuit occurs.

[0051] The first protection circuit 12 cuts off the supply of signals to drive the switching elements of the inverter circuit 4 based on the input of the first detection signal E1. The second protection circuit 22 cuts off the supply of signals to drive the switching elements of the inverter circuit 4 based on the input of the second detection signal E2.

[0052] Specifically, similar to the above configuration, the first protection circuit 12 and the second protection circuit 22 each directly cut off the power supply to the isolator element 6. When the control element 5 receives at least one of the signal F1 from the first protection circuit 12 and the signal F2 from the second protection circuit 22, it stops outputting the PWM signal and cuts off the power supply to the isolator element 6. As a result, the motor drive circuit 2 stops the switching operation of the inverter circuit 4 and cuts off the supply of U-phase voltage, V-phase voltage, and W-phase voltage to the motor M. Furthermore, the control element 5 outputs an error signal to notify the outside of the occurrence of a ground fault or inter-phase short circuit.

[0053] (Effects and Benefits) As described above, the inverter protection circuit 1D of Embodiment 3 includes, in addition to the first resistor R1, first detection circuit 11, and first protection circuit 12 of Embodiment 1, a second resistor R2 connected between the inverter circuit 4 and the ground-side power supply line 8, a second detection circuit 21 that outputs a second detection signal E2 indicating that a phase-to-phase short circuit has been detected based on the current flowing through the second resistor R2, and a second protection circuit 22 that cuts off the supply of signals for driving the switching elements based on the second detection signal E2.

[0054] This configuration provides the same functionality as Embodiment 2. Specifically, a ground fault is detected by the first resistor R1, and a phase-to-phase short circuit is detected by the second resistor R2. Furthermore, if either a ground fault or a phase-to-phase short circuit occurs, the supply of signals for driving the switching elements is interrupted, thereby stopping the switching operation of the inverter circuit 4 and interrupting the supply of U-phase voltage, V-phase voltage, and W-phase voltage to the motor M. Therefore, similar to the above configuration, it is possible to avoid further switching operation occurring in an element damaged by a large current flowing through it due to a ground fault or phase-to-phase short circuit, which could result in current flowing through the damaged element and exacerbating the damage through explosion or other means.

[0055] Furthermore, similar to the above configuration, the first protection circuit 12 and the second protection circuit 22 directly cut off the power supply to the isolator element 6, and in addition, they stop the output of the PWM signal from the control element 5 and cut off the power supply to the isolator element 6 from the control element 5. Therefore, it is possible to avoid the damage escalating due to switching operations occurring before the control element 5 stops the PWM signal and cuts off the power supply to the isolator element 6.

[0056] (Integration of the inverter protection circuit of Embodiment 3 into the IPM) Figure 6 is a block diagram showing the inverter protection circuit 1E incorporated into the IPM30E. As shown in Figure 6, the motor control device 3E includes a motor drive circuit 2E. The motor drive circuit 2E includes an inverter protection circuit 1E. All parts constituting the inverter protection circuit 1E, and the isolator element 6 that provides the function of a gate drive circuit, can be incorporated into the IPM30E.

[0057] The configuration of the inverter protection circuit 1E is as described in the explanation of the inverter protection circuit 1D in Figure 4. The inverter protection circuit 1E may be entirely incorporated into the IPM30E, or only a portion of the functions of the inverter protection circuit 1D and the isolator element 6 may be incorporated into the IPM30E. The parts to be incorporated can be selected as appropriate, as in the cases of Embodiments 1 and 2.

[0058] (Embodiment 4) Figure 7 is a block diagram showing the motor drive circuit 2F, equipped with the inverter protection circuit 1F of Embodiment 4, connected to the motor M. The motor drive circuit 2F is incorporated into the motor control device 3F, as in the above embodiments. The motor drive circuit 2F comprises an inverter circuit 4, a control element 5, an isolator element 6, and an inverter protection circuit 1F.

[0059] The inverter protection circuit 1F is an inverter protection circuit 1B of Embodiment 2 with the addition of a third protection circuit 40. As shown in Figure 7, the inverter protection circuit 1F includes an IPM30F. The IPM30F is an element in which the inverter circuit 4 and the third protection circuit 40 are packaged together.

[0060] The third protection circuit 40 includes an overcurrent detector that detects when a short-circuit current flows through the second resistor R2, and based on the detection of a short-circuit current by the overcurrent detector, the IPM 30F stops supplying the drive voltage to the motor M. For example, the third protection circuit 40 includes a gate interruption circuit that interrupts the gate of a switching element constituting the inverter circuit 4 based on the detection of a short-circuit current by the overcurrent detector.

[0061] The overcurrent detector and gate cutoff circuit can be configured such that, for example, when a current exceeding a preset threshold flows through the second resistor R2, a switch inside the overcurrent detector is switched, and when this signal is input to the gate cutoff circuit, the gate of the switching element is cut off. The gate cutoff circuit may cut off the gate of the low-side switching element of the inverter circuit 4, or it may cut off the gate of the high-side switching element of the inverter circuit 4.

[0062] The third protection circuit 40 inputs a signal to the second detection circuit 21 when a current exceeding a preset threshold flows through the second resistor R2. For example, if a current exceeding a preset threshold flows through the second resistor R2, it outputs an error signal to the outside, causing the second photocoupler 23 to light up.

[0063] (Effects and Benefits) As described above, the inverter protection circuit 1F of Embodiment 4 comprises a first resistor R1 and a first detection circuit 11, a second resistor R2 and a second detection circuit 21, and a protection circuit 15. Furthermore, the inverter protection circuit 1F includes a third protection circuit 40 packaged together with the inverter circuit 4 as IPM30F. The third protection circuit 40 cuts off the supply of signals for driving the switching elements inside the IPM30F based on the current flowing through the second resistor R2. The second detection circuit 21 outputs a second detection signal E2 to the protection circuit 15 based on the signal input via the third protection circuit 40.

[0064] In this way, in addition to the effects of Embodiment 2, it becomes possible to stop the switching operation of the inverter circuit 4 within the IPM30F based on the current flowing through the second resistor R2, without going through the control element 5 or the isolator element 6. Therefore, if a phase short circuit occurs, the switching operation can be stopped quickly, thus preventing current from flowing through a damaged element and avoiding the damage from spreading due to explosion of the damaged element.

[0065] (Modified form of Embodiment 4) Internally, in addition to the third protection circuit 40 described above, or instead of the third protection circuit 40, a fourth protection circuit may be added to the IPM30F to stop the switching operation of the inverter circuit 4 based on the current flowing through the first resistor R1. The fourth protection circuit may be equipped with an overcurrent detector and a gate tripping circuit that detect when a ground fault current or short-circuit current flows through the first resistor R1, similar to the third protection circuit 40. In this case, the first detection circuit 11 may be configured to output a first detection signal E1 based on a signal input via the fourth protection circuit.

[0066] Furthermore, in Embodiment 3, a third protection circuit 40 can be added, and an IPM configuration incorporating the inverter circuit 4 and the third protection circuit 40 can be adopted. Moreover, in Embodiment 1, the switching operation of the inverter circuit 4 can be stopped based on the current flowing through the first resistor R1. By adding a fourth protection circuit to stop the operation, an IPM configuration can be adopted that incorporates the inverter circuit 4 and the fourth protection circuit.

[0067] (Example of changing the element that shuts off the power supply) Figure 8 is a block diagram showing examples of changes to the element that shuts off the power supply by the inverter protection circuit. In each of the above configurations, a PWM signal is input from the control element 5 to the isolator element 6. As shown in Figure 8, a general-purpose logic element 50, such as a buffer element or an inverter element that inverts the signal, can be interposed between the control element 5 and the isolator element 6. When the general-purpose logic element 50 receives a PWM signal from the control element 5, it can output an equivalent PWM signal based on the input signal. Therefore, the isolator element 6 can generate a signal to drive the gate of the switching element based on the PWM signal supplied from the general-purpose logic element 50 and supply it to the inverter circuit 4.

[0068] In the example shown in Figure 8, when a ground fault or phase-to-phase short circuit occurs, the first protection circuit 12 shuts off the power supply to the general-purpose logic element 50 instead of the isolator element 6 based on the first detection signal E1. Similarly, the control element 5 also shuts off the power supply to the general-purpose logic element 50 instead of the isolator element 6. The general-purpose logic element 50 is an element that will not be damaged even if a PWM signal is input when the power supply is shut off. Alternatively, the first protection circuit 12 may shut off the power supply to the general-purpose logic element 50, and the control element 5 may shut off the power supply to the isolator element 6.

[0069] If the configuration shown in Figure 8 is adopted, the range of elements that can be used as the isolator element 6 can be expanded. That is, if the power supply to the isolator element 6 is directly cut off by the first protection circuit 12, the power supply to the isolator element 6 is cut off before the output of the PWM signal from the control element 5 stops. Therefore, only elements that will not be damaged even if a PWM signal is input when the power supply is cut off can be used as the isolator element 6. For example, an isolated gate driver using a photocoupler as an isolated signal transmission circuit will not be damaged even if a PWM signal is input when the power supply is cut off, so it can be used as the isolator element 6.

[0070] In the configuration shown in Figure 8, the isolator element 6 is not limited to an element using a photocoupler as an isolated signal transmission circuit. Therefore, the degree of freedom in selecting the isolator element 6 can be increased.

[0071] (Other embodiments) Each of the above-described inverter protection circuits can be applied to the drive circuits of various electrical devices driven using inverter circuits. Furthermore, the inverter protection circuit of Embodiment 1 can be applied to the drive circuit of a single-phase motor.

[0072] (summary) A summary of this disclosure is provided below. (1) A first resistor is connected between an inverter circuit equipped with a switching element that generates a drive voltage to be applied to an electrical device and a positive power supply line that supplies a constant voltage to the inverter circuit, A first detection circuit that outputs a first detection signal based on the current flowing through the first resistor, An inverter protection circuit characterized by having a first protection circuit that cuts off the supply of a signal for driving the switching element based on the first detection signal.

[0073] (2) The first protection circuit is, Based on the first detection signal, the power supply to the element interposed between the control element supplying the PWM signal and the switching element is cut off, The inverter protection circuit according to (1) above, characterized in that it stops the output of the PWM signal from the control element based on the first detection signal.

[0074] (3) An isolator element equipped with an isolated signal transmission circuit is interposed between the control element and the switching element. A general-purpose logic element that outputs a signal based on the PWM signal is interposed between the control element and the isolator element. The inverter protection circuit according to (2) above, characterized in that the first protection circuit cuts off the power supply to the general-purpose logic element based on the first detection signal.

[0075] (4) An isolator element comprising an isolated signal transmission circuit including a photocoupler is interposed between the control element and the switching element. The inverter protection circuit according to (2) above, characterized in that the first protection circuit cuts off the power supply to the isolator element based on the first detection signal.

[0076] (5) The inverter protection circuit according to any one of (1) to (4) above, characterized in that at least a portion of the first detection circuit and the first protection circuit are incorporated into the intelligent power module including the inverter circuit.

[0077] (6) The inverter protection circuit according to any one of (1) to (4) above, characterized in that the first detection circuit and the first protection circuit are provided outside the intelligent power module including the inverter circuit.

[0078] (7) A second resistor is connected between the inverter circuit and the ground-side power line, A second detection circuit outputs a second detection signal based on the current flowing through the second resistor, An inverter protection circuit according to any one of (1) to (4) above, characterized by having a second protection circuit that cuts off the supply of a signal for driving the switching element based on the second detection signal.

[0079] (8) The inverter protection circuit according to (7) above, characterized in that at least a portion of the first detection circuit, the first protection circuit, the second detection circuit, and the second protection circuit are incorporated into the intelligent power module including the inverter circuit.

[0080] (9) The inverter protection circuit according to (7) above, characterized in that the first detection circuit, the first protection circuit, the second detection circuit, and the second protection circuit are provided outside the intelligent power module including the inverter circuit.

[0081] (10) A first resistor connected between an inverter circuit equipped with a switching element that generates a drive voltage to be applied to an electrical device and a positive power supply line that supplies a constant voltage to the inverter circuit, and a second resistor connected between the inverter circuit and the ground power supply line, A first detection circuit that outputs a first detection signal based on the current flowing through the first resistor, A second detection circuit outputs a second detection signal based on the current flowing through the second resistor, The system includes a protection circuit connected to the first detection circuit and the second detection circuit, The aforementioned protection circuit is An inverter protection circuit characterized by interrupting the supply of a signal for driving the switching element when at least one of the first detection signal and the second detection signal is input.

[0082] (11) The inverter protection circuit according to (10) above, characterized in that at least a portion of the first detection circuit, the second detection circuit, and the protection circuit are incorporated into the intelligent power module including the inverter circuit.

[0083] (12) The intelligent power module, which includes the inverter circuit, incorporates a third protection circuit that cuts off the supply of a signal for driving the switching element based on the current flowing through the second resistor. The inverter protection circuit according to (10) above, characterized in that the second detection circuit outputs the second detection signal based on a signal input via the third protection circuit.

[0084] (13) The inverter protection circuit according to (10) above, characterized in that the first detection circuit, the second detection circuit, and the protection circuit are provided outside the intelligent power module including the inverter circuit.

[0085] (14) The inverter protection circuit according to any one of (1) to (13) above, characterized in that the first detection circuit comprises a first photocoupler having a light-emitting element that emits light based on the current flowing through the first resistor, and a first latch circuit that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the first photocoupler.

[0086] (15) The inverter protection circuit according to any one of (7) to (13) above, characterized in that the second detection circuit comprises a second photocoupler having a light-emitting element that emits light based on the current flowing through the second resistor, and a second latch circuit that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the second photocoupler.

[0087] (16) Having an inverter protection circuit as described in any of (1) to (15) above, The aforementioned electrical device is a motor drive circuit characterized by being a three-phase motor.

[0088] (17) A motor control device characterized by having the motor drive circuit described in (16) above. [Explanation of Symbols]

[0089] 1, 1A, 1B, 1C, 1D, 1E, 1F... Inverter protection circuit, 2, 2A, 2B, 2C, 2D, 2E, 2F... Motor drive circuit, 3, 3A, 3B, 3C, 3D, 3E, 3F... Motor control device, 4... Inverter circuit, 5... Control element, 6... Isolator element, 7... Positive power line, 8... Ground power line, 9... Smoothing capacitor, 11... First detection circuit, 12... First protection circuit, 13... First photocoupler, 14... First latch circuit, 15... Protection circuit, 21... Second detection circuit, 22... Second protection circuit, 23... Second photocoupler, 24... Second latch circuit, 30, 30C, 30E, 30F... IPM, 40... Third protection circuit, 50... General-purpose logic element Child, 100...Inverter circuit, 101...Resistor, E1...First detection signal, E2...Second detection signal, F, F1, F2...Signal, M...Motor, R1...First resistor, R2...Second resistor

Claims

1. A first resistor is connected between an inverter circuit equipped with a switching element that generates a drive voltage to be applied to an electrical device and a positive power supply line that supplies a constant voltage to the inverter circuit, A first detection circuit that outputs a first detection signal based on the current flowing through the first resistor, An inverter protection circuit characterized by having a first protection circuit that cuts off the supply of a signal for driving the switching element based on the first detection signal.

2. The first protection circuit is, Based on the first detection signal, the power supply to the element interposed between the control element supplying the PWM signal and the switching element is cut off, The inverter protection circuit according to claim 1, characterized in that it stops the output of the PWM signal from the control element based on the first detection signal.

3. An isolator element equipped with an isolated signal transmission circuit is interposed between the control element and the switching element. A general-purpose logic element that outputs a signal based on the PWM signal is interposed between the control element and the isolator element. The inverter protection circuit according to claim 2, characterized in that the first protection circuit cuts off the power supply to the general-purpose logic element based on the first detection signal.

4. An isolator element comprising an isolated signal transmission circuit including a photocoupler is interposed between the control element and the switching element. The inverter protection circuit according to claim 2, characterized in that the first protection circuit cuts off the power supply to the isolator element based on the first detection signal.

5. The inverter protection circuit according to claim 1, characterized in that at least a portion of the first detection circuit and the first protection circuit are incorporated into the intelligent power module including the inverter circuit.

6. The inverter protection circuit according to claim 1, characterized in that the first detection circuit and the first protection circuit are provided outside the intelligent power module including the inverter circuit.

7. A second resistor is connected between the inverter circuit and the ground-side power line, A second detection circuit outputs a second detection signal based on the current flowing through the second resistor, The inverter protection circuit according to claim 1, further comprising a second protection circuit that cuts off the supply of a signal for driving the switching element based on the second detection signal.

8. The inverter protection circuit according to claim 7, characterized in that at least a portion of the first detection circuit, the first protection circuit, the second detection circuit, and the second protection circuit are incorporated into the intelligent power module including the inverter circuit.

9. The inverter protection circuit according to claim 7, characterized in that the first detection circuit, the first protection circuit, the second detection circuit, and the second protection circuit are provided outside the intelligent power module including the inverter circuit.

10. A first resistor connected between an inverter circuit equipped with a switching element that generates a drive voltage to be applied to an electrical device and a positive power supply line that supplies a constant voltage to the inverter circuit, and a second resistor connected between the inverter circuit and the ground power supply line, A first detection circuit that outputs a first detection signal based on the current flowing through the first resistor, A second detection circuit outputs a second detection signal based on the current flowing through the second resistor, The first detection circuit and the second detection circuit are connected to a protection circuit, The aforementioned protection circuit is An inverter protection circuit characterized by interrupting the supply of a signal for driving the switching element when at least one of the first detection signal and the second detection signal is input.

11. The inverter protection circuit according to claim 10, characterized in that at least a portion of the first detection circuit, the second detection circuit, and the protection circuit are incorporated into the intelligent power module including the inverter circuit.

12. The intelligent power module, which includes the inverter circuit, incorporates a third protection circuit that cuts off the supply of a signal for driving the switching element based on the current flowing through the second resistor. The inverter protection circuit according to claim 10, characterized in that the second detection circuit outputs the second detection signal based on a signal input via the third protection circuit.

13. The inverter protection circuit according to claim 10, characterized in that the first detection circuit, the second detection circuit, and the protection circuit are provided outside the intelligent power module including the inverter circuit.

14. The inverter protection circuit according to claim 1, characterized in that the first detection circuit comprises a first photocoupler having a light-emitting element that emits light based on the current flowing through the first resistor, and a first latch circuit that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the first photocoupler.

15. The inverter protection circuit according to claim 7, characterized in that the second detection circuit comprises a second photocoupler having a light-emitting element that emits light based on the current flowing through the second resistor, and a second latch circuit that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the second photocoupler.

16. The inverter protection circuit according to claim 10, characterized in that the second detection circuit comprises a second photocoupler having a light-emitting element that emits light based on the current flowing through the second resistor, and a second latch circuit that maintains an ON state based on the rising or falling edge of the output of the light-receiving element of the second photocoupler.

17. Having an inverter protection circuit according to any one of claims 1 to 16, The aforementioned electrical device is a motor drive circuit characterized by being a three-phase motor.

18. A motor control device characterized by having the motor drive circuit of claim 17.

Images