JP2016077157A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device including small-sized and cost-reduced overvoltage protection means for protecting equipment from an instantaneous excessive voltage.SOLUTION: In a motor drive device 10, transistors Q3a-Q5b of both upper and lower arms are turned off when the excessive voltage is generated, such that the excessive voltage is divided into both terminals of two transistors connected in series. The excessive voltage to be applied to one transistor is reduced to a half during operation of any one transistor, such that the transistors can be protected from destruction. Further, a possibility to turn on a switching element (diodes D3a-D5b) by energy that an inductance component of a motor 51 has and an induction voltage of the motor 51 is high but after the transistors of both the upper and lower arms are turned off, electrical brake is applied to speedily stop the motor 51. Thus, a time in which the switching element (diodes) is turned on can be shortened.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor drive device.

  In a device that obtains a DC voltage by rectifying an AC voltage, the DC voltage varies according to the AC voltage. In particular, a device used in an area where the power supply voltage is likely to fluctuate may cause a failure of the device depending on a countermeasure against a voltage increase. Therefore, overvoltage protection means as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-166815) is provided. In this overvoltage protection means, the input transformer is a transformer with a load tap changer, and when the voltage exceeding the threshold is input to the inverter over a predetermined time, the tap of the transformer with the load tap changer is lowered. Switched to the side.

  However, although the transformer with a load tap changer as described above is suitable for a large-scale electric facility, it is not easy to apply to an inverter-controlled motor drive device such as a home appliance.

  In addition, the time required for the power supply voltage to become excessive is extremely short, and the tap switching as described above takes too much time, so that it is difficult to reliably protect such a motor drive device. Furthermore, a semiconductor element such as a semiconductor element that has a short time to withstand overvoltage cannot be protected by being interrupted by a relay. However, increasing the withstand voltage of a semiconductor element or the like only for an instantaneous excessive voltage leads to an increase in cost and size.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor drive device including a small and low-cost overvoltage protection means that protects a device from a momentary excessive voltage.

  In the motor drive device according to the first aspect of the present invention, each of a plurality of upper and lower arms corresponding to each of a plurality of phases of the motor is configured by connecting two switching elements in series, and a connection point formed thereby A motor driving device that outputs a voltage to the corresponding phase from each, and includes a power supply unit, a voltage detection unit, and a control unit. The power supply unit supplies a DC voltage Vdc to the upper and lower arms. The voltage detector is connected in parallel to the upper and lower arms. The control unit turns on and off the switching element. In addition, when the detection value of the voltage detection unit exceeds a predetermined threshold, the control unit turns on all the switching elements of one of the two switching elements of all the upper and lower arms, and then turns on all the upper and lower arms. Both switching elements are turned off.

  In this motor drive device, the DC voltage Vdc is applied to the switching element in which the upper and lower arms are off while any of the switching elements in the upper and lower arms is operating. There is a high possibility that an excessive voltage is applied to one switching element and it is destroyed.

  For example, by turning off both the switching elements of the upper and lower arms when an excessive voltage is generated, the excessive voltage is divided across the two switching elements connected in series, and the excessive voltage applied to one switching element is either one. Is reduced to half that when the device is operating, so that the switching element can be protected from destruction.

  However, if the switching elements of all the upper and lower arms are turned off, the switching elements (diodes) may be turned on by the energy of the motor inductance component and the induced voltage due to the rotation of the motor.

  Therefore, by first turning on all the switching elements of one of the two switching elements of all the upper and lower arms, the current from the motor is circulated and the DC voltage boost due to regeneration of the rotational energy of the motor is prevented. However, the current is attenuated to 0 by the internal impedance of the motor. After that, even if the switching elements of all the upper and lower arms are turned off and the switching elements are turned on due to the energy of the motor inductance component and the induced voltage due to the rotation of the motor, the on-time can be shortened. .

  A motor drive device according to a second aspect of the present invention is the motor drive device according to the first aspect, and further includes a motor brake circuit. The control unit brakes the motor after turning off both switching elements of the upper and lower arms.

  In this motor drive device, when the excessive voltage is generated, both switching elements of the upper and lower arms are turned off, whereby the excessive voltage is divided across the two switching elements connected in series, and the excessive voltage applied to one switching element. Is reduced to half that when either one is operating, so that the switching element can be protected from destruction.

  In addition, the switching element is likely to be turned on by the energy of the motor inductance component and the induced voltage due to the rotation of the motor, but after turning off both the switching elements of the upper and lower arms, the motor is electrically braked and stopped quickly. As a result, the energy of the inductance component can be quickly consumed, the rotational energy of the motor can be quickly attenuated, and the time during which the switching element is on can be shortened.

  The motor drive device according to the third aspect of the present invention is the motor drive device according to the first aspect or the second aspect, and further includes a resistive load and a resistive load connecting means. The resistive load connecting means connects or blocks between the connection point of the two switching elements and the resistive load. The control unit turns off both the switching elements of the upper and lower arms, and then connects the connection point and the resistive load.

  In this motor drive device, when the excessive voltage is generated, both switching elements of the upper and lower arms are turned off, whereby the excessive voltage is divided across the two switching elements connected in series, and the excessive voltage applied to one switching element. Is reduced to half that when either one is operating, so that the switching element can be protected from destruction.

  In addition, the switching element is likely to be turned on by the energy of the motor inductance component and the induced voltage due to the rotation of the motor, but after turning off both switching elements of the upper and lower arms, a resistive load is connected to each phase of the motor. By consuming the energy of the inductance component of the motor with a resistive load in a short time, the time during which the switching element is on can be shortened.

  A motor driving device according to a fourth aspect of the present invention is the motor driving device according to any one of the first to third aspects, and further includes a mechanical brake that is attachable to and detachable from a rotating shaft of the motor. . The control unit mechanically brakes the motor after turning off both switching elements of the upper and lower arms.

  In this motor drive device, when the excessive voltage is generated, both switching elements of the upper and lower arms are turned off, whereby the excessive voltage is divided across the two switching elements connected in series, and the excessive voltage applied to one switching element. Is reduced to half that when either one is operating, so that the switching element can be protected from destruction.

  In addition, the switching element is highly likely to be turned on by the energy of the motor inductance component and the induced voltage due to the rotation of the motor, but after turning off both switching elements of the upper and lower arms, the motor is mechanically braked and stopped quickly. As a result, the rotational energy of the motor is attenuated, and the time during which the switching element is on can be shortened.

  A motor drive device according to a fifth aspect of the present invention is the motor drive device according to the second aspect or the fourth aspect, wherein the control unit is the motor except that the detection value of the voltage detection unit exceeds a threshold value. Do not apply the brake.

  In this motor drive device, unnecessary motor stops are suppressed by limiting the operation of the brake only to overvoltage.

  A motor drive device according to a sixth aspect of the present invention is the motor drive device according to any one of the first to fifth aspects, further comprising an insulated power supply. The insulated power supply is used to drive the upper arm side switching element of the upper and lower arms.

  In this motor drive device, when the excessive voltage is generated, both switching elements of the upper and lower arms are turned off, whereby the excessive voltage is divided across the two switching elements connected in series, and the excessive voltage applied to one switching element. Is reduced to half that when either one is operating, so that the switching element can be protected from destruction.

  At this time, by turning off both switching elements of the upper and lower arms when an excessive voltage is generated, the midpoint potential of the upper and lower arms is at most about one element withstand voltage (the element is destroyed beyond that). Is sufficient to have a design that can withstand the normal rated voltage (that is, one-element breakdown voltage) of the DC section.

  In the motor drive device according to the first aspect of the present invention, when the excessive voltage is generated, both switching elements of the upper and lower arms are turned off, whereby the excessive voltage is divided across the two switching elements connected in series. Since the excessive voltage applied to one switching element is reduced to half of when one of the switching elements is operating, the switching element can be protected from destruction.

  In the motor drive device according to the second aspect of the present invention, when both the switching elements of the upper and lower arms are turned off, there is a high possibility that the switching elements are turned on by the energy of the motor inductance component and the induced voltage due to the rotation of the motor. After switching off both the switching elements of the upper and lower arms, connecting the resistive load to each phase of the motor, the switching element is turned on by consuming the energy of the motor's inductance component in the resistive load in a short time Time can be shortened.

  In the motor drive device according to the third aspect of the present invention, when both the switching elements of the upper and lower arms are turned off, there is a high possibility that the switching elements are turned on by the energy of the motor inductance component and the induced voltage due to the rotation of the motor. After the switching elements of both the upper and lower arms are turned off, the time during which the switching elements are turned on can be shortened by applying a mechanical brake to the motor and quickly stopping the motor.

  In the motor drive device according to the fourth aspect of the present invention, by turning on all the switching elements of one of the two switching elements of all the upper and lower arms, the current from the motor is circulated to rotate the motor. While preventing the DC voltage from being boosted due to energy regeneration, the current is attenuated by the internal impedance of the motor to zero. Thereafter, even if the switching elements of all the upper and lower arms are turned off and the switching elements are turned on by the energy and induced voltage of the inductance component of the motor, the on-time can be shortened.

  In the motor drive device according to the fifth aspect of the present invention, unnecessary motor stops are suppressed by limiting the operation of the brake only to overvoltage.

  The motor drive device according to the sixth aspect of the present invention turns off both switching elements of the upper and lower arms when an excessive voltage is generated, so that the midpoint potential of the upper and lower arms is at most about one element withstand voltage. With respect to, a design that can withstand the normal rated voltage (that is, one-element breakdown voltage) of the DC section is sufficient.

1 is a block diagram showing an overall configuration of a system in which a motor drive device according to a first embodiment of the present invention is employed and a circuit configuration of the motor drive device. The figure which shows how to apply the voltage to an up-and-down arm at the time of operation | movement of a motor drive device. The figure which shows how to apply the voltage to an up-and-down arm at the time of a motor drive device stopping. The block diagram which shows the whole structure of the system by which the motor drive device which concerns on 2nd Embodiment of this invention is employ | adopted, and the circuit structure of a motor drive device. The block diagram which shows the whole structure of the system by which the motor drive device which concerns on 3rd Embodiment of this invention is employ | adopted, and the circuit structure of a motor drive device. The block diagram which shows the whole structure of the system by which the motor drive device which concerns on other embodiment of this invention is employ | adopted, and the internal structure of a motor drive device. The graph of the voltage-current characteristic which shows the relationship between the voltage concerning the both ends of an electrolytic capacitor, and the electric current which flows into an electrolytic capacitor. The graph which shows the control with respect to the change of DC voltage Vdc. FIG. 7B is a graph showing a change in the voltage Vds at both ends of a semiconductor element having an avalanche region on the graph showing the control with respect to the change in the DC voltage Vdc in FIG. 7A. The circuit diagram of the principal part of the motor drive device provided with the bootstrap circuit. The circuit diagram of the principal part of the motor drive device provided with the insulated power supply. The circuit diagram of the principal part of the motor drive device provided with the charge pump circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention.

<First Embodiment>
(1) Overview FIG. 1 is a block diagram showing an overall configuration of a system 100 in which a motor drive device 10 according to a first embodiment of the present invention is employed and an internal configuration of the motor drive device 10. In FIG. 1, a system 100 includes a motor driving device 10 and a motor 51.

(1-1) Motor 51
The motor 51 is a three-phase brushless DC motor, and includes a stator 52 and a rotor 53. The stator 52 includes U-phase, V-phase, and W-phase drive coils Lu, Lv, and Lw that are star-connected. One ends of the drive coils Lu, Lv, and Lw are connected to drive coil terminals TU, TV, and TW of U-phase, V-phase, and W-phase wirings extending from the inverter 25, respectively. The other ends of the drive coils Lu, Lv, and Lw are connected to each other as a terminal TN. These three-phase drive coils Lu, Lv, and Lw generate an induced voltage according to the rotational speed and the position of the rotor 53 as the rotor 53 rotates.

  The rotor 53 includes a plurality of permanent magnets including N poles and S poles, and rotates about the rotation axis with respect to the stator 52.

  The motor 51 is, for example, a compressor motor or a fan motor of a heat pump type air conditioner.

(1-2) Motor drive device 10
As shown in FIG. 1, the motor driving device 10 includes a rectifying unit 21, a smoothing capacitor 22, a voltage detecting unit 23, a current detecting unit 24, an inverter 25, a gate driving circuit 26, and a control unit 40. I have. These may be mounted on, for example, one printed board.

(2) Detailed configuration of motor drive device (2-1) Rectifier 21
The rectifying unit 21 is configured in a bridge shape by four diodes D1a, D1b, D2a, and D2b. Specifically, the diodes D1a and D1b and D2a and D2b are respectively connected in series. The cathode terminals of the diodes D1a and D2a are both connected to the plus side terminal of the smoothing capacitor 22 and function as the positive side output terminal of the rectifying unit 21. The anode terminals of the diodes D1b and D2b are both connected to the negative side terminal of the smoothing capacitor 22 and function as the negative side output terminal of the rectifying unit 21.

  A connection point between the diode D1a and the diode D1b is connected to one pole of the commercial power supply 91. A connection point between the diode D2a and the diode D2b is connected to the other pole of the commercial power supply 91. The rectifying unit 21 rectifies the AC voltage output from the commercial power supply 91 to generate a DC power supply, and supplies this to the smoothing capacitor 22.

(2-2) Smoothing capacitor 22
The smoothing capacitor 22 has one end connected to the positive output terminal of the rectifying unit 21 and the other end connected to the negative output terminal of the rectifying unit 21. The smoothing capacitor 22 smoothes the voltage rectified by the rectifying unit 21. Hereinafter, for the convenience of explanation, the voltage after smoothing by the smoothing capacitor 22 is referred to as a DC voltage Vdc.

  The DC voltage Vdc is applied to the inverter 25 connected to the output side of the smoothing capacitor 22. That is, the rectifying unit 21 and the smoothing capacitor 22 constitute a power supply unit 20 for the inverter 25.

  In addition, as a kind of capacitor | condenser, although an electrolytic capacitor, a film capacitor, a tantalum capacitor etc. are mentioned, a film capacitor is employ | adopted as the smoothing capacitor 22 in this embodiment.

(2-3) Voltage detection unit 23
The voltage detector 23 is connected to the output side of the smoothing capacitor 22 and detects the voltage across the smoothing capacitor 22, that is, the value of the DC voltage Vdc. For example, the voltage detection unit 23 is configured such that two resistors connected in series with each other are connected in parallel to the smoothing capacitor 22 and the DC voltage Vdc is divided. The voltage value at the connection point between the two resistors is input to the control unit 40.

(2-4) Current detection unit 24
The current detection unit 24 is connected between the smoothing capacitor 22 and the inverter 25 and connected to the negative output terminal side of the smoothing capacitor 22. The current detection unit 24 detects the motor current Im flowing through the motor 51 after the motor 51 is started as a total value of currents for three phases.

  The current detection unit 24 may be configured by, for example, an amplifier circuit using a shunt resistor and an operational amplifier that amplifies the voltage across the resistor. The motor current detected by the current detection unit 24 is input to the control unit 40.

(2-5) Inverter 25
In the inverter 25, three upper and lower arms corresponding to the U-phase, V-phase, and W-phase drive coils Lu, Lv, and Lw of the motor 51 are connected in parallel to each other and to the output side of the smoothing capacitor 22.

  In FIG. 1, an inverter 25 includes a plurality of IGBTs (insulated gate bipolar transistors, hereinafter referred to simply as transistors) Q3a, Q3b, Q4a, Q4b, Q5a, Q5b and a plurality of free-wheeling diodes D3a, D3b, D4a, D4b, D5a and D5b are included.

  Transistors Q3a and Q3b, Q4a and Q4b, Q5a and Q5b are connected to each other in series to form each upper and lower arm, and the corresponding phase from each of connection points NU, NV, and NW formed thereby. Output lines extend toward the drive coils Lu, Lv, and Lw.

  The diodes D3a to D5b are connected in parallel to the transistors Q3a to Q5b so that the collector terminal of the transistor and the cathode terminal of the diode are connected, and the emitter terminal of the transistor and the anode terminal of the diode are connected. Each of these transistors and diodes connected in parallel constitutes a switching element.

  The inverter 25 is applied with the DC voltage Vdc from the smoothing capacitor 22 and the transistors Q3a to Q5b are turned on and off at the timing instructed by the gate drive circuit 26, whereby the drive voltages SU, SV and SW are generated. The drive voltages SU, SV, SW are output to the drive coils Lu, Lv, Lw of the motor 51 from the connection points NU, NV, NW of the transistors Q3a and Q3b, Q4a and Q4b, and Q5a and Q5b.

  In addition, although the inverter 25 of this embodiment is a voltage source inverter, it is not limited to it, A current source inverter may be sufficient.

(2-6) Gate drive circuit 26
The gate drive circuit 26 changes the on / off states of the transistors Q3a to Q5b of the inverter 25 based on the command voltage Vpwm from the control unit 40. Specifically, the gate drive circuit 26 includes the transistors Q3a to Q5b so that pulsed drive voltages SU, SV, and SW having a duty determined by the control unit 40 are output from the inverter 25 to the motor 51. Gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz to be applied to the gate are generated. The generated gate control voltages Gu, Gx, Gv, Gy, Gw, Gz are applied to the gate terminals of the respective transistors Q3a to Q5b.

(2-7) Control unit 40
The control unit 40 is connected to the voltage detection unit 23, the current detection unit 24, and the gate drive circuit 26. In the present embodiment, the control unit 40 drives the motor 51 by a rotor position sensorless method. In addition, since it is not limited to a rotor position sensorless system, you may carry out by a sensor system.

  The rotor position sensorless method uses various parameters indicating the characteristics of the motor 51, the detection result of the voltage detection unit 23 after the motor 51 is started, the detection result of the current detection unit 24, a predetermined mathematical model related to the control of the motor 51, and the like. Thus, the rotor position and the rotational speed are estimated, the PI control for the rotational speed, the PI control for the motor current, and the like are driven. Examples of various parameters indicating the characteristics of the motor 51 include the winding resistance, inductance component, induced voltage, and number of poles of the motor 51 used. Since there are many patent documents regarding the rotor position sensorless control, refer to them for details (for example, JP 2013-17289 A).

  The control unit 40 also monitors the detection value of the voltage detection unit 23, and performs protection control to turn off the transistors Q3a to Q5b when the detection value of the voltage detection unit 23 exceeds a predetermined threshold value.

(2-8) Brake circuit 61
In FIG. 1, the brake circuit 61 includes three transistors 61u, 61v, and 61w. The transistor 61u is connected in the middle of the wiring connecting the U-phase drive coil Lu and the common connection point N. The transistor 61v is connected in the middle of the wiring connecting the V-phase drive coil Lv and the common connection point N. The transistor 61w is connected in the middle of the wiring connecting the W-phase drive coil Lw and the common connection point N. In addition, a reflux diode is connected to each of the transistors 61u to 61w.

  The bases of the three transistors 61u, 61v, 61w are connected to the control unit 40 via signal lines.

  While the motor 51 is rotating normally, the control unit 40 does not output drive signals to the bases of the three transistors 61u, 61v, 61w, and therefore, between the collectors and emitters of the three transistors 61u, 61v, 61w. Is a non-conductive state.

  However, when the control unit 40 outputs drive signals to the bases of the three transistors 61u, 61v, 61w, the collectors and emitters become conductive, the drive coils Lu, Lv, Lw are connected, and the motor 51 is braked. Take it.

(3) Operation of Motor Drive Device 10 Hereinafter, the operation of the motor drive device 10 will be described. In FIG. 1, the control unit 40 outputs a waveform to the gate drive circuit 26 and controls the waveform output state to drive the motor 51 at a predetermined rotational speed.

  FIG. 2A is a diagram illustrating how voltage is applied to the upper and lower arms during operation of the motor drive device 10, and FIG. 2B is a diagram illustrating how voltage is applied to the upper and lower arms when the motor drive device 10 is stopped.

  As shown in FIG. 2A, during operation, the upper arm transistor Q3a corresponding to the drive coil Lu, the lower arm transistor Q4b corresponding to the drive coil Lv, and the lower arm transistor Q5b corresponding to the drive coil Lw are turned on. The DC voltage Vdc is applied to the switching elements (transistors Q3b, Q4a, Q5a, diodes D3b, D4a, D5a) in which the upper and lower arms are off.

  At this time, when the DC voltage Vdc becomes an excessive voltage, the excessive voltage is applied to the transistor and the diode of the switching element that is turned off. When the element breakdown voltage of one switching element (transistors Q3a to Q5b and diodes D3a to D5b) is Vr, the transistors Q3a to Q5b or the diodes D3a to D5b of the switching element are destroyed when the DC voltage Vdc> the element breakdown voltage Vr. There is a high possibility of being.

  Therefore, when the control unit 40 determines that the detection value of the voltage detection unit 23 exceeds a predetermined threshold value, the control unit 40 turns off the transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of the upper and lower arms.

  Thereby, as shown in FIG. 2B, the excessive voltage is applied to each of the two switching elements (transistors Q3a, Q3b, Q4a, Q4b, Q5a, Q5b, diodes D3a, D3b, D4a, D4b, D5a, D5b) connected in series. Divided at both ends. For example, the divided voltage value V1 is applied to both ends of the upper arm switching elements (transistors Q3a, Q4a, Q5a, diodes D3a, D4a, D5a), and the lower arm switching elements (transistors Q3b, Q4b, Q5b, diodes D3b, D4b). , D5b) is applied with a partial pressure value V2. Ideally, V1 = V2 if the impedance of each switching element is equal, so that the overvoltage applied to one switching element is reduced to half that when either one is operating, and each switching element is destroyed. Can be protected.

  Further, after turning off the transistors Q3a to Q5b, the control unit 40 outputs a drive signal to each base of the three transistors 61u, 61v, 61w of the brake circuit 61, and makes each collector-emitter conductive. As a result, the motor 51 is braked.

  The purpose of braking the motor 51 is that the diodes D3a to D5b of the switching elements are highly likely to be turned on by the energy of the inductance component of the motor 51 and the induced voltage due to the rotation of the motor 51. Even if the diodes D3a to D5b are turned on, the time during which the diodes D3a to D5b are turned on can be shortened by applying an electric brake to the motor 51 and quickly stopping it.

  In the present embodiment, the control unit 40 does not brake the motor 51 except when the detection value of the voltage detection unit 23 exceeds the threshold value. That is, unnecessary motor stops are suppressed by limiting the operation of the brake only to overvoltage.

(4) Features of the first embodiment (4-1)
In the motor drive device 10, when the excessive voltage is generated, the transistors Q3a to Q5b of the upper and lower arms are turned off, so that the excessive voltage is divided across the two switching elements connected in series, and one switching element (transistor) Since the excessive voltage applied to Q3a to Q5b and the diodes D3a to D5b) is reduced to half that when either one is operating, the switching element can be protected from destruction.

(4-2)
In the motor drive device 10, there is a high possibility that the diodes D3a to D5b are turned on due to the energy of the inductance component of the motor 51 and the induced voltage due to the rotation of the motor 51, but after turning off both the transistors Q3a to Q5b of the upper and lower arms, By applying an electric brake to the motor 51 and quickly stopping it, the time during which the diodes D3a to D5b are on can be shortened.

Second Embodiment
(1) Overview FIG. 3 is a block diagram showing an overall configuration of a system 100 in which a motor drive device 10 according to a second embodiment of the present invention is employed and an internal configuration of the motor drive device 10.

  In FIG. 3, the motor drive device 10 according to the second embodiment is provided with a resistance load 71 and a relay circuit 73 in place of the brake circuit 61 in the first embodiment shown in FIG. Accordingly, the resistance load 71 and the relay circuit 73 will be described here, and the other elements are the same as those in the first embodiment (the configuration excluding the brake circuit 61). Is omitted.

(2) Detailed configuration of motor drive device (2-1) Resistance load 71
In FIG. 3, the resistance load 71 is composed of three resistance elements 71u, 71v, 71w. The resistance element 71u is connected in the middle of a line connecting the U-phase drive coil Lu and the common connection point N. The resistance element 71v is connected in the middle of a line connecting the V-phase drive coil Lv and the common connection point N. The resistance element 71 w is connected in the middle of a line connecting the W-phase drive coil Lw and the common connection point N. Usually, each line is interrupted by a relay circuit 73.

(2-2) Relay circuit 73
The relay circuit 73 includes a relay contact 73a for electrically opening and closing lines connecting the drive coils Lu, Lv, and Lw of each phase of the motor 51 and the corresponding resistance elements 71u, 71v, and 71w, and a relay contact 73a. A relay coil 73b to be operated and a transistor 73c for energizing and de-energizing the relay coil 73b are included. One end of the relay coil 73b is connected to the positive electrode of the driving power supply Vb, and the other end is connected to the collector side of the transistor 73c. The control unit 40 switches between the presence and absence of the base current of the transistor 73c, turns on and off the collector and the emitter, and energizes and de-energizes the relay coil 73b.

(3) Operation of Motor Drive Device 10 Hereinafter, the operation of the motor drive device 10 will be described. Note that when the control unit 40 determines that the detection value of the voltage detection unit 23 has exceeded a predetermined threshold, it is the same as in the first embodiment until the transistors Q3a to Q5b of the upper and lower arms are turned off. The description is omitted.

  The control unit 40 turns off the transistors Q3a to Q5b, and then outputs a drive signal to the base of the transistor 73c of the relay circuit 73 to make each collector-emitter conductive. At this time, the relay coil 73b is excited, the relay contact 73a is closed, the resistance element 71u and the U-phase drive coil Lu, the resistance element 71v and the V-phase drive coil Lv, and further the resistance elements 71w and W The phase drive coil Lw is connected, and the energy of the inductance component of the motor 51 is consumed in a short time by the resistance elements 71u, 71v, 71w, and an electric brake is applied.

  Although there is a high possibility that the diodes D3a to D5b are turned on by the energy and induced voltage of the inductance component of the motor 51, even if the diodes D3a to D5b are turned on, the energy of the inductance component of the motor 51 is converted into resistance elements 71u, By consuming 71v and 71w in a short time, the time during which the diodes D3a to D5b are on can be shortened.

(4) Features of the second embodiment (4-1)
In the motor drive device 10, when an excessive voltage is generated, both transistors Q3a to Q5b of the upper and lower arms are turned off, whereby the excessive voltage is applied to both ends of two switching elements (transistors Q3a to Q5b, diodes D3a to D5b) connected in series. And the excessive voltage applied to one switching element (transistors Q3a to Q5b, diodes D3a to D5b) is reduced to half that when either one is operating, so that the transistors Q3a to Q5b of the switching elements and The diodes D3a to D5b can be protected from destruction.

(4-2)
In the motor drive device 10, there is a high possibility that the diodes D3a to D5b are turned on by the energy of the inductance component of the motor 51 and the induced voltage due to the rotation of the motor. By consuming the energy of the component in the resistance elements 71u, 71v, 71w in a short time, the time during which the diodes D3a to D5b are on can be shortened.

<Third Embodiment>
(1) Overview FIG. 4 is a block diagram showing an overall configuration of a system 100 in which a motor drive device 10 according to a third embodiment of the present invention is employed and an internal configuration of the motor drive device 10.

  4, the motor drive device 10 according to the third embodiment can be attached to and detached from the output shaft of the motor 51 in a configuration in which the electric brake circuit 61 in the first embodiment shown in FIG. 1 is removed. A mechanical brake 81 is newly provided. Therefore, the brake 81 will be described here, and the other elements are the same as those in the first embodiment (the configuration excluding the brake circuit 61).

(2) Configuration of Motor Drive Device 10 The brake 81 is a mechanical brake, and includes an electromagnetic clutch 83 and a load 85 connected to the rotating shaft of the motor 51 via the electromagnetic clutch 83. The electromagnetic clutch 83 connects or releases the rotating shaft of the motor 51 and the load 85 according to a drive signal from the control unit 40.

  The load 85 is constituted by a rotating disk or a rotary damper having a moment of inertia sufficiently larger than that of the rotor 53 of the motor 51 in order to attenuate the rotational force of the rotor 53. Of course, the load 85 is not limited to the rotary disk and the rotary damper, and the load 85 may be anything that can attenuate the rotational force of the rotor 53.

(3) Operation of Motor Drive Device 10 Hereinafter, the operation of the motor drive device 10 will be described. Note that when the control unit 40 determines that the detection value of the voltage detection unit 23 has exceeded a predetermined threshold, it is the same as in the first embodiment until the transistors Q3a to Q5b of the upper and lower arms are turned off. The description is omitted.

  After turning off transistors Q3a-Q5b, control unit 40 operates electromagnetic clutch 83 to connect the rotating shaft of motor 51 and load 85.

  At this time, the energy of the inductance component of the motor 51 and the rotational energy of the motor 51 are consumed in a short time as energy for rotating the load 85.

  Although there is a high possibility that the diodes D3a to D5b are turned on by the energy of the inductance component of the motor 51 and the induced voltage due to rotation, even if the diodes D3a to D5b are turned on, the energy of the inductance component of the motor 51 and the motor 51 Is consumed in a short time as energy to rotate the load 85, so that the time during which the diodes D3a to D5b are on can be shortened.

(4) Features of the third embodiment (4-1)
In the motor drive device 10, when an excessive voltage is generated, both transistors Q3a to Q5b of the upper and lower arms are turned off, whereby the excessive voltage is applied to both ends of two switching elements (transistors Q3a to Q5b, diodes D3a to D5b) connected in series. And the excessive voltage applied to one switching element (transistors Q3a to Q5b, diodes D3a to D5b) is reduced to half that when either one is operating, so that the transistors Q3a to Q5b of the switching elements In addition, the diodes D3a to D5b can be protected from destruction.

(4-2)
In the motor drive device 10, there is a high possibility that the diodes D3a to D5b are turned on by the energy of the inductance component of the motor 51 and the induced voltage caused by the rotation. By consuming the energy of the inductance component and the rotational energy of the motor 51 in a short time by the mechanical brake 81, the time during which the diodes D3a to D5b are on can be shortened.

<Others>
(A)
In the first embodiment, the second embodiment, and the third embodiment, an electric brake or a mechanical brake is provided to brake the motor 51 with the energy of the inductance component of the motor 51 and the rotational energy of the motor 51. Is consumed in a short time, and the time during which the switching elements (diodes D3a to D5b) are on is shortened.

  However, in some cases, a brake circuit or a mechanical brake cannot be provided from a cost and structural viewpoint. In such a case, it is effective to perform the following control.

  For example, when the control unit 40 determines that the detection value of the voltage detection unit 23 exceeds the threshold value, all the transistors in one of the two transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of all the upper and lower arms After turning on, all the transistors Q3a to Q5b are turned off.

  By turning on all the transistors of one of the two transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of all the upper and lower arms, the current from the motor 51 is returned and the rotational energy of the motor 51 is reduced. While preventing the DC voltage from being boosted due to regeneration, the current is attenuated to 0 by the internal impedance of the motor 51.

  After that, the transistors Q3a to Q5b of all the upper and lower arms are turned off, and even if the diodes D3a to D5b are turned on by the energy of the inductance component of the motor 51 and the induced voltage of the motor 51, the on time is shortened. be able to.

(B)
(B-1) Overview FIG. 5 is a block diagram showing an overall configuration of a system 100 in which a motor drive device 10 according to another embodiment of the present invention is employed and an internal configuration of the motor drive device 10.

  In FIG. 5, the motor drive device 10 according to the present embodiment has a configuration in which the brake circuit 61 is removed from the first embodiment shown in FIG. Yes. The smoothing capacitor is an electrolytic capacitor 77. Therefore, here, the relay circuit 75 and the electrolytic capacitor 77 will be described, and the other elements are the same as those in the first embodiment (the configuration excluding the brake circuit 61). Is omitted.

(B-2) Configuration of Motor Drive Device 10 (B-2-1) Relay Circuit 75
In FIG. 5, the relay circuit 75 opens and closes the power supply line 801. Here, opening and closing the power supply line 801 is to turn the power supply line 801 on or off to make it non-conductive.

  As shown in FIG. 5, the relay circuit 75 includes a relay contact 75a for opening and closing the power supply line 801, a relay coil 75b for operating the relay contact 75a, and a transistor 75c for energizing and de-energizing the relay coil 75b. Contains.

  One end of the relay coil 75b is connected to the positive electrode of the driving power supply Vb, and the other end is connected to the collector side of the transistor 75c. The controller 40 switches between the presence and absence of the base current of the transistor 75c, turns on and off the collector and the emitter, and performs energization and de-energization of the relay coil 75b.

  Normally, the relay circuit 75 closes the power supply line 801, that is, makes it conductive. On the other hand, at the time of overvoltage, the relay circuit 75 cuts off the power supply line 801 in response to a signal output from the control unit 40.

(B-2-2) Electrolytic capacitor 77
The electrolytic capacitor 77 is an electrolytic capacitor connected in parallel with the inverter 25. Here, the state in which the overvoltage is applied to the electrolytic capacitor 77 continues for a period of about 10 msec from when the relay circuit 75 receives the signal output from the control unit 40 to when the power supply line 801 is cut off. That is, it is assumed that the overvoltage value may exceed the withstand voltage of the electrolytic capacitor 77 between the time when the voltage detection unit 23 detects the overvoltage and the time when the relay circuit 75 shuts off the power supply line 801.

  FIG. 6 is a graph of voltage / current characteristics showing the relationship between the voltage applied to both ends of the electrolytic capacitor 77 and the current flowing through the electrolytic capacitor 77.

  In FIG. 6, in the case of a capacitor 77 that is an electrolytic capacitor, when a voltage higher than the withstand voltage of the oxide film is applied, formation of the oxide film is performed (the voltage at this time is referred to as a formation voltage), The current flowing through increases.

  However, the electrolytic capacitor 77 is not broken in about 10 msec, and the voltage at both ends thereof is clamped by the formation voltage.

(B-3) Operation of Motor Drive Device 10 FIG. 7A is a graph showing control with respect to a change in DC voltage Vdc. 5 and 7A, when the DC voltage Vdc increases and the detection value of the voltage detection unit 23 exceeds the overvoltage threshold, the control unit 40 cuts off the power supply line 801 through the relay circuit 75.

  The DC voltage Vdc exceeds the capacitor withstand voltage until the relay contact 75a of the relay circuit 75 cuts off the power supply line 801, but is clamped to the formation voltage (generally about 1.3 to 1.5 times the capacitor withstand voltage). Is done. Here, if the element breakdown voltage of the semiconductor switching element (transistor, diode) is set to a value higher than the formation voltage of the capacitor, the relay contact 75a cuts off the power supply line 801 during the voltage clamping period, so the DC voltage Vdc is The breakdown voltage of the semiconductor device is not reached.

  Therefore, during the period in which the voltage across the electrolytic capacitor 77 is clamped by the formation voltage, the overvoltage applied to the inverter 25 can be suppressed to the formation voltage of the electrolytic capacitor 77, and the relay circuit 75 is connected to the power line 801 within that period. By shutting off, it is possible to prevent the electrolytic capacitor 77 from being destroyed, and to reduce stress on a semiconductor element that does not have an avalanche region, such as the transistor (IGBT) of the inverter 25.

  Note that the avalanche region is a region in which a phenomenon in which carriers rapidly flow exceeding a certain breakdown voltage of a semiconductor occurs.

  Next, FIG. 7B is a graph in which the change in the voltage Vds at both ends of the semiconductor element having the avalanche region is placed on the graph showing the control with respect to the change in the DC voltage Vdc in FIG. 7A. In FIG. 7B, for example, when a MOSFET is employed instead of the transistor of the inverter 25, the voltage Vds across the MOSFET generally becomes higher than the DC voltage Vdc due to a surge generated by wiring inductance or a boosting operation. The voltage Vds rises as the DC voltage Vdc rises as the power supply voltage rises.

  In this case, suppose that the semiconductor device breakdown voltage of the MOSFET is lower than the formation voltage of the electrolytic capacitor, and the voltage Vds exceeds the semiconductor device breakdown voltage before the voltage across the electrolytic capacitor 77 is clamped by the formation voltage. Even when it is clamped by the avalanche voltage, the voltage across the electrolytic capacitor 77 is clamped by the formation voltage during that time, and then the relay contact 75a cuts off the power supply line 801.

  As described above, during the period of about 10 msec until the power supply line 801 is cut off, the avalanche operation can withstand overvoltage, so that the MOSFET does not need to have a high breakdown voltage.

  In addition, the avalanche energy of the MOSFET can be suppressed by clamping the voltage across the capacitor 77 (electrolytic capacitor) with the formation voltage.

(C)
Although only the mechanical brake is used in the third embodiment, a brake (electric brake) as in the first embodiment or the second embodiment may be used in combination.

(D)
(D-1) Issues When Adopting Charge Pump Circuit 46 In the first, second, and third embodiments, the overvoltage protection of the switching elements of the upper and lower arms has been described mainly. However, in actual use, the overvoltage extends not only to the switching element but also to the output circuit of the gate drive circuit 26.

  In particular, when a charge pump system is employed as a system for creating a power supply for driving the upper arm side switching element (increasing the gate potential corresponding to the varying upper and lower arm connection point potential), a charge pump circuit is configured. Since the withstand voltage of the switch or the like is generally designed to be about the withstand voltage of one switching element (that is, about the normal DC voltage Vdc), the final withstand voltage capability is the withstand voltage of the switch or the like constituting the charge pump circuit (see FIG. 10). Limited by ability.

  In FIG. 10, in the charge pump circuit 46, the first switch element 465 is turned on and the second switch element 466 is turned off, whereby the first capacitor 461 is charged. Thereafter, the first switch element 465 is turned off and the second switch element 466 is turned on, whereby the charge accumulated in the first capacitor 461 is transferred to the second capacitor 462. By repeating this operation, the upper arm driving power source (charged second capacitor 462) can be created. Charging of the first capacitor 461 and the second capacitor 462 is performed by the oscillation circuit 464.

  The second capacitor 462 is charged up to Vb, but since the low potential side of the second capacitor 462 is connected to Vdc, the high potential side of the second capacitor 462 becomes Vb + Vdc.

  Therefore, in the charge pump circuit 46, both the first switch element 465 and the second switch element 466 need to have a breakdown voltage equal to or higher than Vb + Vdc, and are normally designed with a breakdown voltage equivalent to one switching element (that is, about a normal DC voltage Vdc). Is done. Therefore, there remains a problem that the breakdown voltage at the time of overvoltage is limited to the breakdown voltage of the first switch element 465 and the second switch element 466.

(D-2) Adoption of Bootstrap Circuit 31 Therefore, the bootstrap system is used as a system for creating a power supply for driving the upper arm side switching element (increasing the gate potential in accordance with the varying upper and lower arm connection point potential). It is preferable.

  FIG. 8 is a circuit diagram of a main part of the motor driving apparatus 10 including the bootstrap circuit 31. In FIG. 8, a bootstrap circuit 31 is provided to increase the gate potential of the upper arm side switching element. Here, the gate drive circuit 26 and the bootstrap circuit 31 will be described.

(D-2-1) Configuration of Gate Drive Circuit 26 The gate drive circuit 26 includes an upper arm side drive circuit 26a for driving the upper arm side transistors Q3a, Q4a, and Q5a, and a lower arm side transistor Q3b, A lower arm side drive circuit 26b for driving Q4b and Q5b, and 10 terminals Vcc, Vdd, Hin, Lin, Vss, Vbo, Ho, Vs, Lo, and COM.

  In the gate drive circuit 26, the positive electrode of the driving power source Vb for driving the transistor is connected to the terminal Vcc, and the positive electrode of the logic power source Vc is connected to the terminal Vdd. The signal line from the control unit 40 is connected to the terminal Hin and the terminal Lin, and the negative electrodes of the driving power supply Vb and the logic power supply Vc are connected to the terminal Vss and also connected to the negative electrode of the motor power supply (DC voltage Vdc). ing.

  The line branched from the high potential side pole of the capacitor 311 of the bootstrap circuit 31 is connected to the terminal Vbo, the emitters of the transistors Q3a, Q4a, and Q5a are connected to the terminal Vs, and the transistors Q3b, Q4b, and Q5b are connected to each other. The emitter is connected to the terminal COM. Further, the gates of the transistors Q3a, Q4a, and Q5a are connected to the terminal Ho, and the gates of the transistors Q3b, Q4b, and Q5b are connected to the terminal Lo.

  The transistors Q3a, Q4a, Q5a, Q3b, Q4b, and Q5b are turned on / off by the gate drive circuit 26 controlling the gate potential via the terminal Ho and the terminal Lo. The operation of the gate drive circuit 26 is controlled based on a duty ratio control signal input from the control unit 40 to the terminal Hin and the terminal Lin.

(D-2-2) Configuration of Bootstrap Circuit 31 The gate drive circuit 26 includes a drive power supply Vb connected to the terminal Vcc in order to appropriately input a gate potential to the transistors Q3a, Q4a, Q5a on the upper arm side. The bootstrap circuit 31 is provided between the positive electrode of the transistor and the emitters of the transistors Q3a, Q4a, and Q5a.

  FIG. 8 shows only the gate drive circuit 26 corresponding to the transistors Q3a and Q3b of the upper and lower arms and the bootstrap circuit 31 corresponding to the gate drive circuit 26. A gate drive circuit and a bootstrap circuit are provided correspondingly.

  The bootstrap circuit 31 includes a capacitor 311, a resistor 312, and a diode 313. One end of the capacitor 311 is connected to a connection point NU between the emitter of the transistor Q3a on the upper arm side and the collector of the transistor Q3b on the lower arm side. The other end of the capacitor 311 is connected to the positive electrode of the driving power supply Vb via a resistor 312 and a diode 313.

  The resistor 312 is provided to limit the charging current of the capacitor 311, and the diode 313 is arranged in order so that the capacitor 311 is not discharged via the resistor 312, and the current does not flow to Vb even when the Vs potential changes. The direction is directed from the positive electrode side of the driving power supply Vb to the capacitor 311 side.

  The upper arm side drive circuit 26a inside the gate drive circuit 26 takes in a high potential from the capacitor 311 in order to control on / off of the transistor Q3a. The lower arm side drive circuit 26b in the gate drive circuit 26 controls on / off of the transistor Q3b. However, since the emitter side of the transistor Q3b is grounded, the potential of the positive electrode of the drive power supply Vb connected to the terminal Vcc. Can only be controlled.

  By turning on the lower arm side transistor Q3b by the lower arm side drive circuit 26b, the drive power supply Vb (positive electrode) -diode 313-resistor 312-capacitor 311-lower arm side transistor Q3b-drive power supply Vb (negative electrode) Current flows through the path. At this time, since the capacitor 311 is charged, it can be used as an upper arm side driving power source. The Vs potential changes between Vdc and 0 due to switching of the upper and lower arm transistors, but no current flows to the Vb side due to the diode 313. Here, the withstand voltage of the diode 313 is normally designed to a value that can withstand the normal rated voltage (that is, one element withstand voltage) of the DC section.

(D-3) Effect when Bootstrap Circuit 31 is Adopted In the motor drive device 10, when the excessive voltage is generated, both transistors Q3a to Q5b of the upper and lower arms are turned off, so that the excessive voltage is applied to each of the two switching elements connected in series. Since the overvoltage applied to one switching element (transistors Q3a to Q5b and diodes D3a to D5b) is reduced to half that when either one is operating, the switching element is protected from destruction. can do. In other words, since each of the two switching elements connected in series can withstand the element withstand voltage, the voltage of the DC section can withstand a voltage that is twice the withstand voltage of one element.

  At this time, the midpoint potential of the upper and lower arms is at most about one device breakdown voltage (there is no need to consider since the device will be destroyed if it is higher), so the bootstrap circuit 31 has a circuit configuration. A design that can withstand the normal rated voltage (that is, one-element breakdown voltage) of the DC section is sufficient.

(E)
In the above (D), the bootstrap circuit 31 (see FIG. 8) is recommended as a method for raising the gate potential of the upper arm side switching element instead of the charge pump method, but is not limited thereto.

  FIG. 9 is a circuit diagram of the main part of the motor drive device 10 provided with the insulated power supply 36. In FIG. 9, an insulated power source 36 is provided for each gate of the upper arm. FIG. 9 shows only the gate drive circuit 26 corresponding to the transistors Q3a and Q3b of the upper and lower arms and the insulated power supply 36 corresponding to the gate drive circuit 26. Correspondingly, a gate drive circuit and an insulated power supply are provided.

  Similarly to the bootstrap circuit described above, in the motor drive device 10, by turning off the transistors Q3a to Q5b of the upper and lower arms when an excessive voltage is generated, the middle point potential of the upper and lower arms is at most one element withstand voltage. Since the power supply becomes to the extent (the element is destroyed beyond that), a design that can withstand the normal rated voltage (that is, the one-device breakdown voltage) of the DC section is sufficient for the insulated power supply 36.

  Since the present invention can protect each transistor of the upper and lower arms from overvoltage, it is useful not only for motor drive devices but also for other drive devices using inverters.

DESCRIPTION OF SYMBOLS 10 Motor drive device 20 Power supply part 23 Voltage detection part 31 Bootstrap circuit 36 Insulated power supply 40 Control part 51 Motor 61 Brake circuit 71 Resistance load 73 Relay circuit (resistance load connection means)
81 Brake (mechanical brake)
Q3a transistor (switching element)
Q3b transistor (switching element)
Q4a transistor (switching element)
Q4b transistor (switching element)
Q5a transistor (switching element)
Q5b Transistor (switching element)
D3a Diode (switching element)
D3b Diode (switching element)
D4a Diode (switching element)
D4b Diode (switching element)
D5a Diode (switching element)
D5b Diode (switching element)
NU Connection point NV Connection point NW Connection point Vdc DC voltage

JP 2007-166815 A

Claims (6)

A plurality of upper and lower arms corresponding to a plurality of phases of the motor respectively connect two switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b, D3a, D3b, D4a, D4b, D5a, D5b) in series. A motor driving device configured to output a voltage from each of the connection points (NU, NV, NW) formed thereby to the corresponding phase,
A power supply unit (20) for supplying a DC voltage (Vdc) to the upper and lower arms;
A voltage detector (23) connected in parallel to the upper and lower arms;
A control unit (40) for turning on and off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b);
With
When the detection value of the voltage detection unit (23) exceeds a predetermined threshold value, the control unit (40) detects the two switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of all the upper and lower arms. ) After turning on all the switching elements of one of the arms, turning off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of all the upper and lower arms,
Motor drive device (10). The motor further includes a brake circuit (61),
The controller (40) brakes the motor after turning off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of both the upper and lower arms.
The motor drive device (10) according to claim 1. A resistive load (71);
A resistance load connection means (73) for connecting or blocking between the connection point (NU, NV, NW) and the resistance load (71);
Further comprising
The controller (40) turns off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of both the upper and lower arms, and then connects the connection point (NU, NV, NW) and the resistive load ( 71)
The motor drive device (10) according to claim 1 or claim 2. A mechanical brake (81) detachably attached to the rotating shaft of the motor;
The controller (40) mechanically brakes the motor after turning off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of the upper and lower arms,
The motor drive device (10) according to any one of claims 1 to 3. The controller (40) does not apply the brake to the motor except when the detected value of the voltage detector (23) exceeds the threshold value.
The motor drive device (10) according to claim 2 or 4. An insulation power source (36) used for driving the upper arm side switching elements (Q3a, Q4a, Q5a) of the upper and lower arms;
The motor drive device (10) according to any one of claims 1 to 5.

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