CN110022115B - Motor drive device - Google Patents

Abstract

The invention provides a motor drive device having a small-sized and low-cost overvoltage protection unit for protecting a device from instantaneous excessive voltage. In the motor driving device (10), when an excessive voltage is generated, the transistors (Q3 a-Q5 b) of the upper and lower arms are turned off, so that the excessive voltage is divided by the two ends of each of the 2 transistors connected in series, and the excessive voltage applied to the 1 transistor is reduced to half of that when any one of the transistors operates, thereby protecting the transistors from being damaged. Although the switching elements (diodes D3a to D5 b) are likely to be turned on by the energy of the inductance component of the motor (51) and the induced voltage of the motor 51, the switching elements (diodes) can be turned on for a short time by electrically braking the motor (51) after turning off the transistors of both the upper and lower arms.

Description

motor drive

This application is a divisional application of an invention patent application with application number 201480070191.7 (international application number: PCT/JP2014/084110, filing date: December 24, 2014, invention name: motor drive device).

technical field

The invention relates to motor drives.

Background technique

In a device that rectifies an AC voltage to obtain a DC voltage, the DC voltage fluctuates according to the AC voltage. In particular, equipment used in areas where power supply voltage is likely to fluctuate may cause failure of the equipment no matter how the countermeasures are taken when the voltage rises. Therefore, an overvoltage protection unit as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-166815 ) is provided. The overvoltage protection unit uses the input transformer as a transformer with on-load tap changer (load time tap changer), and when the voltage above the threshold is input to the inverter for more than a specified time, the transformer with on-load tap changer The tap (tap) is switched to the low-voltage side.

Contents of the invention

The problem to be solved by the invention

However, although the above-mentioned transformer with on-load tap changer is suitable as a transformer for large-scale electrical equipment, it is difficult to apply to a drive device of a motor controlled by an inverter in home appliances and the like.

In addition, the time required for the power supply voltage to become too large is extremely short, and the above-mentioned tap switching takes too much time, so it is difficult to reliably protect such a motor drive device. Furthermore, for elements such as semiconductor elements, which can withstand overvoltage for a short period of time, it is impossible to protect them by shutting off by relays. Having said that, increasing the withstand voltage of semiconductor elements and the like just for momentary excessive voltage leads to higher cost and larger size.

Therefore, an object of the present invention is to provide a motor drive device including a small and low-cost overvoltage protection unit that protects equipment from instantaneous overvoltage.

means of solving problems

A motor drive device according to a first aspect of the present invention is a motor drive device in which a switching element constituting an upper arm corresponding to a plurality of phases of the motor and a switching element constituting a lower arm corresponding to the plurality of phases are connected in series. , output voltages to the corresponding phases from the connection points thus formed, and the switching elements are connected in parallel with the diodes for return flow, wherein the motor drive device has: a power supply part that controls the AC output from the commercial power supply The voltage is rectified to generate a DC power supply, and a DC voltage Vdc is supplied to the upper and lower arms; a voltage detection unit is connected in parallel with the upper and lower arms; and a control unit is configured to turn on and off the switching element, and the The control unit turns off the switching elements of both the upper and lower arms when the detection value of the voltage detection unit exceeds a predetermined threshold value.

In this motor drive device, while the switching element of any one of the upper and lower arms is operating, the DC voltage Vdc is applied to the switching element of the upper and lower arms, so when it becomes an excessive voltage, the excessive voltage is applied There is a high possibility that one switching element that is turned off will be damaged.

Therefore, when an excessive voltage is generated, by turning off the switching elements of both the upper and lower arms, the excessive voltage is divided by both ends of the two switching elements connected in series, and the excessive voltage applied to one switching element is reduced. To half of the time when either one is operating, it is possible to protect the switching element from damage.

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 brake circuit for the motor. The control unit brakes the motor after turning off the switching elements of both the upper and lower arms.

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

In addition, although there is a high possibility that the switching element will be turned on due to the energy contained in the inductance component of the motor and the induced voltage caused by the rotation of the motor, after turning off the switching elements of both the upper and lower arms, the motor will be electrically connected. Braking to stop it quickly can quickly consume the energy of the inductance component, and can quickly attenuate the rotational energy of the motor, shortening the conduction time of the switching element.

A motor drive device according to a third viewpoint of the present invention is the motor drive device according to a first viewpoint or a second viewpoint, and further includes a resistive load and resistive load connection means. The resistive load connecting unit connects the connection point of the two switching elements to the resistive load, or disconnects the connection point of the two switching elements from the resistive load. The control unit connects the connection point to the resistive load after turning off the switching elements of both the upper and lower arms.

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

In addition, although the switching element may be turned on due to the energy of the inductance component of the motor and the induced voltage caused by the rotation of the motor, after turning off the switching elements of both the upper and lower arms, the resistance load and the The phases of the motor are connected, and the energy of the inductance component of the motor is consumed in a short time by using the resistive load, so that the time during which the switching element is turned on can be shortened.

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

In this motor drive device, when an excessive voltage is generated, the switching elements of both the upper and lower arms are turned off, so that the excessive voltage is divided by both ends of the two switching elements connected in series, and applied to one switching element. The excessive voltage is reduced to half of the operation of either side, so the switching element can be protected from damage.

In addition, although there is a high possibility that the switching element will be turned on due to the energy of the inductance component of the motor and the induced voltage due to the rotation of the motor, after turning off the switching elements of both the upper and lower arms, mechanically control the motor. Moving to stop it quickly can attenuate the rotational energy of the motor and shorten the conduction time of the switching element.

A motor drive device according to a fifth aspect of the present invention is the motor drive device according to any one of the first aspect to the fourth aspect, wherein the control unit, when the detection value of the voltage detection unit exceeds a threshold value, After the switching elements of any one of the two switching elements of the upper and lower arms are all turned on, all the switching elements are turned off.

In this motor drive device, by turning on all the switching elements of any one of the two switching elements of the upper and lower arms, the current from the motor can be recirculated, and the damage caused by the regeneration of the rotational energy of the motor can be prevented. While boosting the DC voltage, the internal impedance of the motor is used to attenuate the current to zero. Then, by turning off all the switching elements of the upper and lower arms, even if the switching elements are turned on due to the energy of the inductance component of the motor and the induced voltage due to the rotation of the motor, the turn-on time can be shortened.

A motor drive device according to a sixth aspect of the present invention is the motor drive device according to any one of the second to fifth viewpoints, wherein the control unit does not control the motor unless the detected value of the voltage detection unit exceeds a threshold value. Apply the brakes.

In this motor drive device, unnecessary stoppage of the motor is suppressed by limiting the operation of the brake to only when an overvoltage occurs.

A motor drive device according to a seventh viewpoint of the present invention is the motor drive device according to any one of the first viewpoint to the sixth viewpoint, and further includes a bootstrap circuit. The bootstrap circuit generates a potential higher than a lower potential side of the switching element for driving power supply of the switching element on the upper arm side of the upper and lower arms.

In this motor drive device, when an excessive voltage is generated, the switching elements of both the upper and lower arms are turned off, so that the excessive voltage is divided by both ends of the two switching elements connected in series, and applied to one of the switching elements. Excessive voltage is reduced to half of the operating time of either one, so the switching element can be protected from damage. In other words, as the voltage of the DC voltage part (hereinafter, abbreviated as DC part), it must be able to withstand a voltage that is twice the withstand voltage of one element, so that the two switching elements connected in series can respectively withstand the withstand voltage of the element ( Suzi pressure resistance).

At this time, the midpoint potential of the upper and lower arms is at most about one element withstand voltage (if it is above this, the element will be destroyed, so there is no need to consider it). Therefore, for the bootstrap circuit, its circuit structure can withstand the DC part. Usually, the design of the rated voltage (that is, the withstand voltage of one element) is sufficient.

A motor drive device according to an eighth viewpoint of the present invention is the motor drive device according to any one of the first viewpoint to the sixth viewpoint, and further includes an isolated power supply. An isolated power supply is used to drive the upper arm side switching elements of the upper and lower arms.

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

At this time, when an excessive voltage is generated, by turning off the switching elements of both the upper and lower arms, the midpoint potential of the upper and lower arms is maximized to about one element's withstand voltage (the element will be destroyed if it is above this). Therefore, for insulation As for the power supply, a design capable of withstanding the normal rated voltage of the DC section (that is, a withstand voltage of one element) is sufficient.

A motor drive device according to a ninth viewpoint of the present invention is further provided with a balance circuit in addition to the motor drive device according to the first viewpoint. The balance circuit is arranged between a pair of DC buses connecting the power supply unit and the upper and lower arms, and the connection point. The control unit turns on and off the switching element. Also, when the detection value of the voltage detection unit exceeds a predetermined threshold value, the control unit turns off the switching elements of both the upper and lower arms.

While the switching elements of either of the upper and lower arms are operating, the DC voltage Vdc is applied to the switching elements of the upper and lower arms that are turned off. Therefore, when the excessive voltage becomes excessive, the excessive voltage is applied to one of the switching elements that is turned off. On the other hand, there is a high possibility of destroying the switching element.

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

However, since the DC voltage Vdc is not divided equally due to the difference in impedance between the two switching elements, the DC voltage Vdc is divided approximately equally by both ends of the two switching elements by connecting a balance circuit.

A motor drive device according to a tenth aspect of the present invention is the motor drive device according to the ninth aspect, wherein the balancing circuit is arranged so as to correspond to the switching elements of the plurality of upper and lower arms, respectively.

In this motor drive device, for example, in the case of an inverter circuit, three pairs of upper and lower arms are connected in parallel. Therefore, by connecting a balance circuit to each of the upper and lower arms, the direct current voltage Vdc is controlled by each of the upper and lower arms at the time of overvoltage. Both ends of the two switching elements divide the voltage substantially equally, so that the switching elements can be protected from damage.

An overvoltage protection circuit according to an eleventh aspect of the present invention is the motor drive device according to the ninth aspect or the tenth aspect, and includes a switch. The switch is used to connect a connection point of two switching elements connected in series to an intermediate point of a pair of balanced circuits corresponding to the two switching elements, or to connect a connection point of the two switching elements to the middle point of a pair of balanced circuits corresponding to the two switching elements. The connection between the intermediate points of a pair of balanced circuits corresponding to the switching elements is cut off. The control unit connects the balance circuit when the detection value of the voltage detection unit exceeds a predetermined threshold.

In this motor driving device, by arranging a switch between the connection point NU, NV, NW and the intermediate point of a pair of balance circuits corresponding to the connection point NU, NV, NW and connecting the balance circuit only when the inverter is off circuit, the power consumption of the balance circuit can be suppressed.

A motor drive device according to a twelfth aspect of the present invention is the motor drive device according to any one of the ninth aspect to the eleventh aspect, wherein the balancing circuit is constituted by a resistance element.

In this motor drive device, since the resistance element is relatively cheap, it is possible to suppress an increase in cost due to provision of the balancing circuit.

The effect of the invention

In the motor drive device according to the first aspect of the present invention, when an excessive voltage is generated, the switching elements of both the upper and lower arms are turned off, so that the excessive voltage is divided by both ends of the two switching elements connected in series, and applied. Excessive voltage to one switching element is reduced to half of that when either one is operating, so that the switching element can be protected from damage.

In the motor drive device according to the second aspect of the present invention, when the switching elements of both the upper and lower arms are turned off, the switching elements are turned on due to the energy contained in the inductance component of the motor and the induced voltage caused by the rotation of the motor. It is possible, but after turning off the switching elements of both the upper and lower arms, the electric brake is applied to the motor to quickly stop it, and the time during which the switching elements are turned on can be shortened.

In the motor drive device according to the third aspect of the present invention, when the switching elements of both the upper and lower arms are turned off, although the switching elements are turned on due to the energy contained in the inductance component of the motor and the induced voltage caused by the rotation of the motor However, after turning off the switching elements of both the upper and lower arms, by connecting the resistive load to each phase of the motor, the energy contained in the inductance component of the motor can be consumed in a short time by the resistive load, and the conduction of the switching elements can be shortened. pass time.

In the motor drive device according to the fourth aspect of the present invention, when the switching elements of both the upper and lower arms are turned off, although the switching elements are turned on due to the energy contained in the inductance component of the motor and the induced voltage caused by the rotation of the motor It is possible, but after turning off the switching elements of both the upper and lower arms, the motor is mechanically braked to quickly stop the motor, and the time during which the switching elements are turned on can be shortened.

In the motor drive device according to the fifth aspect of the present invention, by turning on all the switching elements of any one of the two switching elements of the upper and lower arms, the current from the motor can be recirculated, and the rotation caused by the motor can be prevented. While boosting the DC voltage due to energy regeneration, the current is attenuated to zero by the internal impedance of the motor. Then, by turning off all the switching elements of the upper and lower arms, even if the switching elements are turned on due to the energy of the inductance component of the motor and the induced voltage, the turn-on time can be shortened.

In the motor drive device according to the sixth viewpoint of the present invention, unnecessary stoppage of the motor is suppressed by limiting the operation of the brake to only the time of overvoltage.

In the motor drive device according to the seventh aspect of the present invention, when an excessive voltage is generated, by turning off the switching elements of both the upper and lower arms, the midpoint potential of the upper and lower arms reaches a maximum of one element withstand voltage. In the case of a circuit, a design capable of withstanding the normal rated voltage of the DC part (that is, a withstand voltage of one element) is sufficient.

In the motor drive device according to the eighth aspect of the present invention, when an excessive voltage is generated, by turning off the switching elements of both the upper and lower arms, the midpoint potential of the upper and lower arms reaches a maximum level of the withstand voltage of one element. As for the power supply, a design capable of withstanding the normal rated voltage of the DC section (that is, a withstand voltage of one element) is sufficient.

In the motor drive device according to the ninth aspect of the present invention, the DC voltage Vdc is applied to the off switching elements of the upper and lower arms while the switching elements of the upper and lower arms are operating. , there is a high possibility that the excessive voltage is applied to one switching element that is turned off, and the switching element is destroyed.

Therefore, when an excessive voltage is generated, by turning off the switching elements of both the upper and lower arms, the excessive voltage is divided by both ends of the two switching elements connected in series, and the excessive voltage applied to one switching element is reduced. It is about half of the time when either one is operating, so the switching element can be protected from damage.

However, since the DC voltage Vdc is not divided equally due to the difference in impedance between the two switching elements, the DC voltage Vdc is divided approximately equally by both ends of the two switching elements by connecting a balance circuit.

In the motor drive device according to the tenth aspect of the present invention, in the case of the inverter circuit, three pairs of upper and lower arms are connected in parallel, so by connecting a balance circuit to each of the upper and lower arms, the DC voltage Vdc Since the voltage is divided approximately equally by both ends of the two switching elements of the upper and lower arms, the switching elements can be protected from damage.

In the motor drive device according to the eleventh aspect of the present invention, by disposing a switch between the connection points NU, NV, NW and the intermediate point of a pair of balance circuits corresponding to the connection points NU, NV, NW, only the inverse By connecting the balance circuit when the inverter is off, the power consumption of the balance circuit can be suppressed.

In the motor drive device according to the twelfth aspect of the present invention, since the resistive element is relatively inexpensive, it is possible to suppress an increase in cost due to the provision of the balancing circuit.

Description of drawings

1 is a block diagram showing the overall configuration of a system using a motor drive device according to a first embodiment of the present invention and a circuit configuration of the motor drive device.

FIG. 2A is a diagram illustrating a manner in which voltages are applied to the upper and lower arms during operation of the motor drive device.

FIG. 2B is a diagram illustrating a manner in which voltage is applied to the upper and lower arms when the motor drive device is stopped.

3 is a block diagram showing the overall configuration of a system using a motor drive device according to a second embodiment of the present invention and a circuit configuration of the motor drive device.

4 is a block diagram showing the overall configuration of a system using a motor drive device according to a third embodiment of the present invention and a circuit configuration of the motor drive device.

5 is a block diagram showing the overall configuration of a system using a motor drive device according to another embodiment of the present invention and the internal structure of the motor drive device.

6 is a graph of voltage/current characteristics showing the relationship between the voltage applied across the electrolytic capacitor and the current flowing through the electrolytic capacitor.

FIG. 7A is a graph showing control for changes in DC voltage Vdc.

7B is a graph showing changes in voltage Vds across both ends of a semiconductor element having an avalanche region loaded in the graph of FIG. 7A showing control for changes in DC voltage Vdc.

8 is a circuit diagram of a main part of a motor drive device having a bootstrap circuit.

Fig. 9 is a circuit diagram of a main part of a motor drive device having an isolated power supply.

10 is a circuit diagram of a main part of a motor drive device having a charge pump circuit.

11 is a block diagram showing a circuit configuration of a motor drive device according to a fourth embodiment of the present invention.

FIG. 12A is a diagram illustrating a manner in which voltage is applied to the upper and lower arms during operation of the motor drive device.

FIG. 12B is a diagram illustrating a mode of applying voltages to the upper and lower arms when the motor drive device is stopped.

FIG. 12C is a diagram showing a mode of applying voltages to the upper and lower arms when the balance circuit is connected after the motor drive device stops.

13 is a block diagram showing a circuit configuration of a motor drive device according to a fifth embodiment of the present invention.

FIG. 14 is a diagram showing a mode of applying voltages to the upper and lower arms when the balance circuit is connected after the motor drive device of another embodiment is stopped.

detailed description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the following embodiment is a specific example of this invention, and does not limit the technical scope of this invention.

(first embodiment)

(1) Summary

FIG. 1 is a block diagram showing an overall configuration of a system 100 using a motor drive device 10 according to a first embodiment of the present invention and an internal configuration of the motor drive device 10 . In FIG. 1 , a system 100 is composed of a motor drive device 10 and a motor 51 .

(1-1) Motor 51

The motor 51 is a three-phase brushless DC motor and has a stator 52 and a rotor 53 . The stator 52 includes star-connected U-phase, V-phase, and W-phase drive coils Lu, Lv, and Lw. One end of each drive coil Lu, Lv, and Lw is connected to drive coil terminals TU, TV, and TW of the respective U-phase, V-phase, and W-phase wirings extending from the inverter 25 . The other ends of the drive coils Lu, Lv, and Lw are connected to each other as terminals TN. These three-phase drive coils Lu, Lv, and Lw are rotated by the rotor 53 to generate induced voltages corresponding to the rotation speed and the position of the rotor 53 .

The rotor 53 includes permanent magnets with multiple poles including N poles and S poles, and rotates about the rotation axis relative to the stator 52 .

In addition, the motor 51 is, for example, a compressor motor or a fan motor of a heat pump air conditioner.

(1-2) Motor drive device 10

As shown in FIG. 1 , the motor drive device 10 includes: a rectification unit 21 ; a smoothing capacitor 22 ; a voltage detection unit 23 ; a current detection unit 24 ; an inverter 25 ; a gate drive circuit 26 ; The above-mentioned parts may be mounted on, for example, one printed circuit board.

(2) Detailed structure of the motor drive device 10

(2-1) Rectification unit 21

The rectification unit 21 is configured in a bridge shape by four diodes D1a, D1b, D2a, and D2b. Specifically, the diodes D1a and D1b, D2a and D2b are connected in series with each other. Both cathode terminals of diodes D1 a and D2 a are connected to the positive side terminal of smoothing capacitor 22 , and function as positive side output terminals of rectification unit 21 . Both the anode terminals of the diodes D1b and D2b are connected to the negative side terminal of the smoothing capacitor 22 and function as the negative side output terminal of the rectification unit 21 .

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

(2-2) Smoothing capacitor 22

One end of the smoothing capacitor 22 is connected to the positive output terminal of the rectification unit 21 , and the other end is connected to the negative output terminal of the rectification unit 21 . The smoothing capacitor 22 smoothes the voltage rectified by the rectification unit 21 . Hereinafter, for convenience of description, the voltage smoothed 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 rectification unit 21 and the smoothing capacitor 22 constitute the power supply unit 20 for the inverter 25 .

In addition, examples of types of capacitors include electrolytic capacitors, film capacitors, and tantalum capacitors. In this embodiment, a film capacitor is used as the smoothing capacitor 22 .

(2-3) Voltage detection unit 23

The voltage detection unit 23 is connected to the output side of the smoothing capacitor 22 and detects the value of the DC voltage Vdc which is the voltage across the smoothing capacitor 22 . The voltage detection unit 23 is configured, for example, by connecting two resistors connected in series to each other in parallel to the smoothing capacitor 22 to divide the DC voltage Vdc. The voltage value at the connection point between these 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 is 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 the total value of the three-phase currents.

The current detection unit 24 may be constituted 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

The inverter 25 and three upper and lower arms respectively 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 are connected to the output side of the smoothing capacitor 22 .

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

Transistors Q3a and Q3b, Q4a and Q4b, Q5a and Q5b are connected in series with each other to form respective upper and lower arms, and the output lines go from the connection points NU, NV and NW thus formed to drive coils Lu, Lv, Lw extended.

The respective diodes D3a to D5b are connected in parallel to the respective transistors Q3a to Q5b such that the collector terminals of the transistors are connected to the cathode terminals of the diodes, and the emitter terminals of the transistors are connected to the anode terminals of the diodes. The transistors and diodes connected in parallel constitute switching elements.

The inverter 25 is supplied with the DC voltage Vdc from the smoothing capacitor 22 via the DC bus (power supply lines 801, 802), and the respective transistors Q3a to Q5b are turned on and off at the timing instructed by the gate drive circuit 26, thereby generating Drive voltages SU, SV, SW for driving the motor 51 . The drive voltages SU, SV, SW are output to the drive coils Lu, Lv, Lw of the motor 51 from connection points NU, NV, NW of the respective transistors Q3a, Q3b, Q4a, Q4b, Q5a, Q5b.

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

(2-6) Gate drive circuit 26

The gate drive circuit 26 changes the on and off states of the respective transistors Q3a to Q5b of the inverter 25 according to the command voltage Vpwm from the control unit 40 . Specifically, the gate drive circuit 26 generates gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz to be applied to the gates of the respective transistors Q3a to Q5b so that the output from the inverter 25 to the motor 51 has The pulse-shaped driving voltages SU, SV, and SW of the duty ratio determined by the unit 40 . The generated gate control voltages Gu, Gx, Gv, Gy, Gw, and 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 is a part that drives the motor 51 without a rotor position sensor. In addition, since it is not limited to the rotor position sensorless system, it can also be performed by the sensor system.

The rotor position sensorless method refers to a method that uses various parameters indicating the characteristics of the motor 51, the detection results of the voltage detection unit 23 after the motor 51 is started, the detection results of the current detection unit 24, and regulations related to the control of the motor 51. The mathematical model of the rotor, the estimation of the rotor position and the rotational speed, the PI control for the rotational speed, the PI control for the motor current, etc., are used to drive. 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. In addition, there are many patent documents regarding the rotor position sensorless control, so for details, please refer to these patent documents (for example, Japanese Patent Laid-Open No. 2013-17289).

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

(2-8) Brake circuit 61

In FIG. 1 , the braking circuit 61 is composed of three transistors 61u, 61v, and 61w. The transistor 61u is connected to the middle of the wiring connecting the U-phase drive coil Lu and the common connection point N. The transistor 61v is connected to the middle of the wiring connecting the V-phase drive coil Lv and the common connection point N. The transistor 61w is connected to the middle of the wiring connecting the W-phase drive coil Lw and the common connection point N. In addition, the transistors 61u to 61w are respectively connected to diodes for return flow.

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

During normal rotation of the motor 51, the control unit 40 does not output drive signals to the respective bases of the three transistors 61u, 61v, and 61w. Therefore, the respective collectors and emitters of the three transistors 61u, 61v, and 61w are negative. conduction state.

However, when the control unit 40 outputs drive signals to the respective bases of the three transistors 61u, 61v, and 61w, the respective collectors and emitters are in a conduction state, and the drive coils Lu, Lv, and Lw are connected, thereby controlling the motor. 51 for braking.

(3) Operation of the motor drive device 10

Next, 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 , controls the state of the waveform output, and drives the motor 51 at a predetermined rotational speed.

FIG. 2A is a diagram showing how voltages are applied to the upper and lower arms when the motor drive device 10 is operating, and FIG. 2B is a diagram showing how voltages are applied to the upper and lower arms when the motor drive device 10 is stopped.

As shown in FIG. 2A, during operation, the transistor Q3a of the upper arm corresponding to the drive coil Lu, the transistor Q4b of the lower arm corresponding to the drive coil Lv, and the transistor Q5b of the lower arm corresponding to the drive coil Lw perform conduction operations. During this period, the DC voltage Vdc is applied to the off switching elements (transistors Q3b, Q4a, Q5a, diodes D3b, D4a, D5a) of the respective upper and lower arms.

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 are turned off. If the element withstand voltage of one switching element (transistors Q3a~Q5b and diodes D3a~D5b) is set to Vr, when the DC voltage Vdc>element withstand voltage Vr, the transistors Q3a~Q5b or diodes D3a~D5b of the switching element are There is a high possibility of damage.

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

As a result, as shown in FIG. 2B , each of the two switching elements (transistors Q3a, Q3b, Q4a, Q4b, Q5a, Q5b, diodes D3a, D3b, D4a, D4b, D5a, D5b) to which the excessive voltage is connected in series terminal pressure. For example, the divided voltage value V1 is applied to both ends of the switching elements of the upper arm (transistors Q3a, Q4a, Q5a, diodes D3a, D4a, D5a), and the divided voltage value V2 is applied to the switching elements of the lower arm (transistors Q3b, Q4b, Q5b, Diodes D3b, D4b, D5b) both ends. Ideally, if the impedance of each switching element is equal, then V1=V2, therefore, the excessive voltage applied to one switching element is reduced to half of that when either one is operating, and each switching element can be protected from damage .

Furthermore, after the control unit 40 turns off the transistors Q3a to Q5b, it outputs a driving signal to the respective bases of the three transistors 61u, 61v, and 61w of the braking circuit 61, and turns on each collector-emitter. As a result, the motor 51 is braked.

The purpose of braking the motor 51 is to increase the possibility that the diodes D3a to D5b of the switching elements will 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 and the electric brake is applied to stop the motor 51 quickly, the time during which the diodes D3a to D5b are turned on can be shortened.

In addition, in this embodiment, the control part 40 does not brake the motor 51 except when the detection value of the voltage detection part 23 exceeds a threshold value. That is, unnecessary stopping of the motor is suppressed by limiting the operation of the brake to only at the time of overvoltage.

(4) Features of the first embodiment

(4-1)

In the motor drive device 10, when an excessive voltage is generated, the transistors Q3a to Q5b of both the upper and lower arms are turned off, so that the excessive voltage is divided by both ends of the two switching elements connected in series and applied to one Since the excess voltage of the switching elements (transistors Q3a to Q5b and diodes D3a to D5b) is reduced to half of that when any one is operating, the switching elements can be protected from destruction.

(4-2)

In the motor drive device 10, although the energy of the inductance component of the motor 51 and the induced voltage caused by the rotation of the motor 51 may cause the diodes D3a to D5b to be turned on, the transistors on both the upper and lower arms After Q3a to Q5b are turned off, by electrically braking the motor 51 to quickly stop it, it is possible to shorten the conduction time of the diodes D3a to D5b.

(second embodiment)

(1) Summary

3 is a block diagram showing the overall configuration of a system 100 using the motor drive device 10 according to the second embodiment of the present invention and the internal configuration of the motor drive device 10 .

In FIG. 3 , a motor drive device 10 according to the second embodiment is provided with a resistive load 71 and a relay circuit 73 instead of the brake circuit 61 in the first embodiment shown in FIG. 1 . Therefore, here, the resistive load 71 and the relay circuit 73 will be described, and since the other elements are the same as those of the first embodiment (configuration other than the brake circuit 61), the same names and numerals will be given, and A detailed description thereof is omitted.

(2) Detailed structure of the motor drive device 10

(2-1) Resistance load 71

In FIG. 3 , the resistive load 71 is composed of three resistive elements 71u, 71v, and 71w. The resistance element 71u is connected in the middle of the line connecting the U-phase drive coil Lu and the common connection point N. As shown in FIG. The resistance element 71v is connected to the middle of the line connecting the V-phase drive coil Lv and the common connection point N. As shown in FIG. The resistance element 71w is connected in the middle of the line connecting the W-phase drive coil Lw and the common connection point N. As shown in FIG. Usually, the above-mentioned respective lines are cut off by the relay circuit 73 .

(2-2) Relay circuit 73

The relay circuit 73 includes drive coils Lu, Lv, and Lw of the respective phases of the motor 51, a relay contact 73a that electrically opens and closes a line connected to the respective resistance elements 71u, 71v, and 71w corresponding to them, and a relay contact 73a that connects the respective resistance elements 71u, 71v, and 71w. The relay coil 73b that operates, and the transistor 73c that energizes and de-energizes the relay coil 73b. 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 the presence or absence of the base current of the transistor 73c, conducts and cuts off the collector and the emitter, and performs energization and non-energization to the relay coil 73b.

(3) Operation of the motor drive device 10

Next, the operation of the motor drive device 10 will be described. Note that the control unit 40 is the same as the first embodiment up to the point at which the transistors Q3a to Q5b of both the upper and lower arms are turned off when the detection value of the voltage detection unit 23 is determined to exceed a predetermined threshold, and thus description thereof will be omitted.

After the control unit 40 turns off the transistors Q3a to Q5b, it outputs a drive signal to the base of the transistor 73c of the relay circuit 73 to bring the respective collectors and emitters into a conductive state. At this time, the relay coil 73b is excited, the relay contact 73a is closed, and the resistance element 71u is connected to the drive coil Lu of the U phase, or the resistance element 71v is connected to the drive coil Lv of the V phase, and then the resistance element 71w is connected to the drive coil Lw of the W phase. Electric braking is performed by dissipating energy contained in the inductance component of the motor 51 in a short time by the resistive elements 71u, 71v, and 71w.

Although there is a high possibility that the diodes D3a to D5b will be turned on due to the energy of the inductance component of the motor 51 and the induced voltage, even assuming that the diodes D3a to D5b are turned on, by using the resistance elements 71u, 71v, and 71w in a short time Energy contained in the inductance component of the motor 51 is internally consumed, and the conduction time of the diodes D3a to D5b can also be shortened.

(4) Features of the second embodiment

(4-1)

In the motor drive device 10, when an excessive voltage is generated, by turning off the transistors Q3a to Q5b of both the upper and lower arms, each of the two switching elements (transistors Q3a to Q5b and diodes D3a to D5b) connected in series to the excessive voltage is Divide the voltage across both ends of the switching element (transistors Q3a~Q5b, diodes D3a~D5b) to reduce the excessive voltage to one half of the operation of either one, so the transistors Q3a~Q5b and diodes of the switching element can be protected. D3a～D5b are protected from damage.

(4-2)

In the motor drive device 10, although there is a high possibility that the diodes D3a to D5b will be turned on due to the energy of the inductance component of the motor 51 and the induced voltage caused by the rotation of the motor, the transistors on both the upper and lower arms are turned off. Then, by consuming the energy contained in the inductance component of the motor 51 in a short time by the resistance elements 71u, 71v, and 71w, it is possible to shorten the conduction time of the diodes D3a to D5b.

(third embodiment)

(1) Summary

4 is a block diagram showing the overall configuration of a system 100 using the motor drive device 10 according to the third embodiment of the present invention and the internal configuration of the motor drive device 10 .

In FIG. 4, in the motor drive device 10 of the third embodiment, in the structure after removing the electric brake circuit 61 in the first embodiment shown in FIG. The mechanical brake 81 that the output shaft is disassembled. Therefore, here, the brake 81 will be described, and since the other elements are the same as those of the first embodiment (configuration other than the brake circuit 61), the same names and symbols will be used, and detailed descriptions will be omitted. .

(2) Structure of the motor drive device 10

The brake 81 is a mechanical brake and is composed of an electromagnetic clutch 83 and a load 85 , wherein the load 85 is connected to the rotating shaft of the motor 51 via the electromagnetic clutch 83 . The electromagnetic clutch 83 connects or uncouples the rotation shaft of the motor 51 and the load 85 based on a drive signal from the control unit 40 .

Since the load 85 attenuates the rotational force of the rotor 53 , it is constituted by a rotating disk or a rotational damper having a sufficiently larger moment of inertia than the rotor 53 of the motor 51 . Of course, the load 85 is not limited to the rotating disk and the rotating damper as long as it can attenuate the rotational force of the rotor 53 .

(3) Operation of the motor drive device 10

Next, the operation of the motor drive device 10 will be described. Note that the control unit 40 is the same as the first embodiment up to the point where the transistors Q3a to Q5b of both the upper and lower arms are turned off when the detection value of the voltage detection unit 23 is determined to exceed a predetermined threshold, and thus description thereof will be omitted.

The control unit 40 activates the electromagnetic clutch 83 after turning off the transistors Q3 a to Q5 b to connect the rotating shaft of the motor 51 and the 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 will be turned on due to the energy contained in 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 inductance component of the motor 51 is turned on. The existing energy and the rotational energy of the motor 51 are consumed in a short time as energy to rotate the load 85, and the time during which the diodes D3a to D5b are turned on can also be shortened.

(4) Features of the third embodiment

(4-1)

In the motor drive device 10, when an excessive voltage is generated, by turning off the transistors Q3a to Q5b of both the upper and lower arms, each of the two switching elements (transistors Q3a to Q5b and diodes D3a to D5b) connected in series to the excessive voltage is Divide the voltage across both ends of the switching element (transistors Q3a~Q5b, diodes D3a~D5b) to reduce the excessive voltage to one half of the operation of either one, so the transistors Q3a~Q5b and diodes of the switching element can be protected. D3a～D5b are protected from damage.

(4-2)

In the motor drive device 10, although the energy of the inductance component of the motor 51 and the induced voltage caused by the rotation may cause the diodes D3a-D5b to be turned on, the transistors Q3a-D5b on both the upper and lower arms are turned on. After Q5b is turned off, the energy of the inductance component of the motor 51 and the rotational energy of the motor 51 are consumed in a short time by the mechanical brake 81, so that the time during which the diodes D3a to D5b are turned on can be shortened.

＜Others＞

(A)

In the first, second, and third embodiments, an electric brake or a mechanical brake is provided, and by braking the motor 51, the inductance component of the motor 51 is consumed in a short time. The energy and the rotational energy of the motor 51 shorten the conduction time of the switching elements (diodes D3a-D5b).

However, there are cases where it is not possible to provide a brake circuit or a mechanical brake from the viewpoint of cost and structure. 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 any one arm of the two transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of the upper and lower arms are turned on. After being turned on, all the transistors Q3a to Q5b are turned off.

By turning on all the transistors of any one of the two transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of the upper and lower arms, the current from the motor 51 can be recirculated, preventing the rotation energy of the motor 51 from being Simultaneously with boosting the DC voltage due to regeneration, the current is attenuated to zero by the internal impedance of the motor 51 .

Then, all the transistors Q3a-Q5b of the upper and lower arms are turned off, even if the diodes D3a-D5b are turned on due to the energy of the inductance component of the motor 51 and the induced voltage of the motor 51, the conduction time can be shortened.

(B)

(B-1) Summary

5 is a block diagram showing the overall configuration of a system 100 using the motor drive device 10 according to another embodiment of the present invention and the internal structure of the motor drive device 10 .

In FIG. 5 , in the motor drive device 10 of this embodiment, in the structure in which the brake circuit 61 is removed from the first embodiment shown in FIG. 1 , a relay circuit for cutting off the power line is newly provided. 75. In addition, a smoothing capacitor is used as the electrolytic capacitor 77 . Therefore, here, the relay circuit 75 and the electrolytic capacitor 77 will be described, and since the other elements are the same as those of the first embodiment (configuration other than the brake circuit 61), the same names and reference numerals will be given, and A detailed description thereof is omitted.

(B-2) Structure of the motor drive device 10

(B-2-1) Relay circuit 75

In FIG. 5 , the relay circuit 75 opens and closes the power line 801 . Here, opening and closing the power supply line 801 refers to making the power supply line 801 conductive or disconnecting it to be non-conductive.

As shown in FIG. 5, the relay circuit 75 includes a relay contact 75a for opening and closing the power 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.

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

Normally, the relay circuit 75 closes the power supply line 801 , that is, turns it into a conduction state. On the other hand, in the event of an overvoltage, the relay circuit 75 receives a signal output from the control unit 40 to cut off the power supply line 801 .

(B-2-2) Electrolytic capacitor 77

The electrolytic capacitor 77 is an electrolytic capacitor connected in parallel to the inverter 25 . Here, the state where the overvoltage is applied to the electrolytic capacitor 77 continues for about 10 msec after the relay circuit 75 receives the signal output from the control unit 40 until the power line 801 is cut off. That is, a possibility is assumed that the overvoltage value exceeds the breakdown voltage of the electrolytic capacitor 77 in the period after the voltage detection unit 23 detects the overvoltage until the relay circuit 75 cuts off the power supply line 801 .

FIG. 6 is a graph of voltage/current characteristics of 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 the electrolytic capacitor 77, when a voltage higher than the withstand voltage of the oxide film is applied, a chemical conversion process for forming the oxide film is performed (the voltage at this time is referred to as a chemical conversion voltage (formation voltage)), and the flow The current in the electrolytic capacitor 77 increases.

Among them, the electrolytic capacitor 77 will not be destroyed in about 10 msec, and the voltage at both ends thereof is clamped at the forming voltage.

(B-3) Operation of the motor drive device 10

FIG. 7A is a graph showing control for changes in DC voltage Vdc. In FIGS. 5 and 7A , when the DC voltage Vdc rises and the detection value of the voltage detection unit 23 exceeds the overvoltage threshold, the control unit 40 cuts off the power line 801 via the relay circuit 75 .

Although the DC voltage Vdc exceeds the withstand voltage of the capacitor for about 10 msec until the relay contact 75a of the relay circuit 75 cuts off the power supply line 801, the DC voltage Vdc is clamped at the forming voltage (generally 1.3 to 1.5 times the withstand voltage of the capacitor) about). Here, if the element withstand voltage of the semiconductor switching element (transistor, diode) is set in advance to a value higher than the formation voltage of the capacitor, the relay contact 75a will cut off the power supply line 801 during the voltage clamping period, so , DC voltage Vdc will not reach the withstand voltage of semiconductor components.

Therefore, during the period when the voltage across the electrolytic capacitor 77 is clamped at the formation voltage, the overvoltage applied to the inverter 25 can be suppressed at the formation voltage of the electrolytic capacitor 77, and the relay circuit 75 connects the power line to the formation voltage during this period. 801 cutoff, thereby preventing the electrolytic capacitor 77 from being destroyed, and reducing the stress on the semiconductor element having no avalanche region such as the transistor (IGBT) of the inverter 25 .

In addition, the avalanche region refers to a region of a phenomenon in which carriers rapidly flow beyond a certain withstand voltage of a semiconductor.

Next, FIG. 7B is a graph of changes in voltage Vds across the semiconductor element having an avalanche region loaded in the graph representing the control for changes in DC voltage Vdc of FIG. 7A . In FIG. 7B , for example, when the transistors of the inverter 25 are replaced with IGBTs and MOSFETs are used, the voltage Vds across the MOSFETs generally becomes higher than the DC voltage due to a surge due to wiring inductance or a boost operation, etc. Vdc. Furthermore, the voltage Vds rises with the rise of the DC voltage Vdc accompanying the rise of the power supply voltage.

In this case, even if it is assumed that the breakdown voltage of the semiconductor element of the MOSFET is lower than the formation voltage of the electrolytic capacitor, the voltage Vds exceeds the breakdown voltage of the semiconductor element before the voltage across the electrolytic capacitor 77 is clamped to the formation voltage. Since the voltage Vds is clamped at the avalanche voltage, the voltage across the electrolytic capacitor 77 is also clamped at the formation voltage during this period, and then the relay contact 75 a 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 overvoltage is received by the avalanche operation, so it is not necessary to make the MOSFET a high withstand voltage component.

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

(C)

In the third embodiment, only the mechanical brake is used, but the brakes (electric brakes) as in the first embodiment and the second embodiment may be used together.

(D)

(D-1) Problems when using the charge pump circuit 46

In the first, second, and third embodiments described above, the description has focused on the overvoltage protection of the switching elements of the upper and lower arms. However, in actual use, the overvoltage is not limited to the switching element, but also involves the output circuit of the gate drive circuit 26 .

In particular, when the charge pump method is adopted as the method for making the power supply for driving the switching elements on the upper arm side (increasing the gate potential in accordance with the fluctuating upper and lower arm connection point potentials), the resistance of the switches constituting the charge pump circuit, etc. The voltage is generally designed as the withstand voltage level of a switching element (that is, the level of the normal DC voltage Vdc), so the final withstand voltage strength is limited to the withstand voltage of the switches constituting the charge pump circuit (see Figure 10). strength.

In FIG. 10 , in the charge pump circuit 46 , the first capacitor 461 is charged by turning on the first switching element 465 and turning off the second switching element 466 . Then, by turning off the first switching element 465 and turning on the second switching element 466 , the charge accumulated in the first capacitor 461 is transferred to the second capacitor 462 . By repeating this operation, an upper arm drive power supply (charged second capacitor 462) can be produced. Charging of the first capacitor 461 and the second capacitor 462 is performed by the oscillation circuit 464 .

Although the second capacitor 462 is charged to Vb, since the low potential side of the second capacitor 462 is connected to Vdc, the high potential side of the second capacitor 462 is Vb+Vdc.

Therefore, in the charge pump circuit 46, both the first switching element 465 and the second switching element 466 require a withstand voltage of Vb+Vdc or higher, and are generally designed to have a withstand voltage corresponding to one of the switching elements (that is, usually When the degree of DC voltage Vdc). Therefore, there is a problem that the withstand voltage at the time of overvoltage is limited to the withstand voltage of the first switching element 465 and the second switching element 466 .

(D-2) Using a bootstrap circuit 31

Therefore, it is preferable to adopt a bootstrap method as a method for producing a driving power supply for the switching element on the upper arm side (the gate potential is raised in accordance with the fluctuating upper and lower arm connection point potentials).

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

(D-2-1) Structure of the gate drive circuit 26

The gate drive circuit 26 internally has an upper arm side drive circuit 26a for driving the transistors Q3a, Q4a, and Q5a on the upper arm side and a lower arm side drive circuit 26b for driving the transistors Q3b, Q4b, and Q5b on the lower arm side. It has 10 terminals of Vcc, Vdd, Hin, Lin, Vss, Vbo, Ho, Vs, Lo, and COM.

In the gate drive circuit 26 , the anode of the driving power supply Vb for driving the transistor is connected to the terminal Vcc, and the anode of the logic power supply 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 poles of the driving power supply Vb and the logic power supply Vc are connected to the terminal Vss, and also connected to the negative poles of the motor power supply (DC voltage Vdc).

In addition, a line branched from one pole on the high potential side of the capacitor 311 of the bootstrap circuit 31 is connected to the terminal Vbo, the respective emitters of the transistors Q3a, Q4a, and Q5a are connected to the terminal Vs, and the respective emitters of the transistors Q3b, Q4b, and Q5b are connected to the terminal Vs. Terminal COM connection. In addition, 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.

Transistors Q3 a , Q4 a , Q5 a , Q3 b , Q4 b , and Q5 b are turned on and off by gate drive circuit 26 by controlling the gate potential through terminal Ho and terminal Lo. The operation of the gate drive circuit 26 is controlled by the control unit 40 based on the duty ratio control signal input to the terminal Hin and the terminal Lin.

(D-2-2) Structure of the bootstrap circuit 31

In the gate drive circuit 26, a bootstrap circuit 31 is provided between the anode of the drive power supply Vb connected to the terminal Vcc and the respective emitters of the transistors Q3a, Q4a, and Q5a, so that the transistors Q3a, Q4a on the upper arm side , Q5a input grid potential.

In FIG. 8, 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 are described, but in fact, each of the three sets of upper and lower arms corresponds to each arm. The ground is provided with a gate drive circuit and a bootstrap circuit.

The bootstrap circuit 31 is composed of 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 anode of the drive power supply Vb via a resistor 312 and a diode 313 .

Resistor 312 is set to limit the charging current of capacitor 311, and the forward direction of diode 313 is from the positive side of the driving power supply Vb to the side of capacitor 311, so that capacitor 311 is not discharged through resistor 312, and when Vs potential changes, Current also does not flow through Vb.

The upper arm side drive circuit 26a inside the gate drive circuit 26 takes a high potential from the capacitor 311 to control the on and off of the transistor Q3a. In addition, although the lower arm side drive circuit 26b inside the gate drive circuit 26 controls the on and off of the transistor Q3b, since the emitter side of the transistor Q3b is grounded, only the positive electrode of the drive power supply Vb connected to the terminal Vcc is passed. Potential can be controlled.

By using the lower arm side drive circuit 26b to turn on the transistor Q3b on the lower arm side, the current flows between the driving power supply Vb (positive electrode)-diode 313-resistor 312-capacitor 311-lower arm side transistor Q3b-driving power supply Vb( flow in the path of the negative pole). At this time, since the capacitor 311 is charged, it can be used as a power source for driving the upper arm side. Although the Vs potential is changed from Vdc to 0 by switching the transistors of the upper and lower arms, current does not flow to the Vb side due to the diode 313 . Here, the withstand voltage of the diode 313 is generally designed to be a value that can withstand the normal rated voltage of the DC section (that is, one element withstand voltage).

(D-3) Effects when using the bootstrap circuit 31

In the motor drive device 10, when an excessive voltage is generated, the transistors Q3a to Q5b of both the upper and lower arms are turned off, so that the excessive voltage is divided by both ends of the two switching elements connected in series and applied to one switch. The excess voltage of the elements (transistors Q3a to Q5b, diodes D3a to D5b) is reduced to half of that when any one is operating, so that the switching elements can be protected from destruction. In other words, the voltage of the DC part must be able to withstand a voltage that is twice the withstand voltage of one element, so that each of the two switching elements connected in series can withstand the withstand voltage of the element.

At this time, the midpoint potential of the upper and lower arms is at most the level of a component withstand voltage (if it is above this, the component will be destroyed, so there is no need to consider it), so the bootstrap circuit 31 can withstand DC in its circuit structure. The usual rated voltage (that is, a component withstand voltage) design is sufficient.

(E)

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

FIG. 9 is a circuit diagram of main parts of the motor drive device 10 having the isolated power supply 36 . In FIG. 9, the gate of each upper arm is provided with an isolated power supply 36. In FIG. 9, only the gate drive circuit 26 corresponding to the transistors Q3a and Q3b of the upper and lower arms and the insulating power supply 36 corresponding to the gate drive circuit 26 are described, but in fact, each of the three sets of upper and lower arms corresponds to each arm. Equipped with gate drive circuit and isolated power supply.

As described above in the bootstrap circuit, in the motor drive device 10, when an excessive voltage is generated, the transistors Q3a to Q5b of both the upper and lower arms are turned off, so that the midpoint potential of the upper and lower arms reaches a maximum of one. The degree of withstand voltage of the element (beyond this, the element will be destroyed). Therefore, for the isolated power supply 36, a design that can withstand the normal rated voltage of the DC part (that is, the withstand voltage of one element) is sufficient.

(fourth embodiment)

(1) Summary

FIG. 11 is a block diagram showing a circuit configuration of a motor drive device 10 according to a fourth embodiment of the present invention. In FIG. 11 , the system 100 as a whole is constituted by the motor drive device 10 and the motor 51 .

In FIG. 11, in the motor drive device 10 of the fourth embodiment, in addition to the structure in which the brake circuit 61 is removed from the first embodiment shown in FIG. 33b, 34a, 34b, 35a, 35b, in addition, electrolytic capacitors are used as the smoothing capacitor 22.

In the present embodiment, a portion constituted by the voltage detection unit 23 , the current detection unit 24 , and the balance circuits 33 a , 33 b , 34 a , 34 b , 35 a , and 35 b is called an overvoltage protection circuit 50 .

For the description, the other elements are the same as those of the first embodiment (configuration other than the brake circuit 61 ), so the same names and symbols are assigned to them, and detailed descriptions thereof are omitted.

(2) Balance circuits 33a, 33b, 34a, 34b, 35a, 35b

The balance circuits 33a to 35b are composed of resistance elements. A pair of balance circuits 33a, 33b corresponds to a pair of switching elements (transistors Q3a, Q3b and diodes D3a, D3b) constituting the upper and lower arms. Similarly, a pair of balancing circuits 34a, 34b corresponds to a pair of switching elements (transistors Q4a, Q4b and diodes D4a, D4b), and a pair of balancing circuits 35a, 35b corresponds to a pair of switching elements (transistors Q5a, Q5b and diodes D5a, D5b). )correspond.

The balance circuits 33a and 33b, 34a and 34b, 35a and 35b are connected in series with each other, and the connection points MU, MV, and MW formed thereby are connected in series with each other through transistors Q3a and Q3b, Q4a and Q4b, Q5a and Q5b respectively. The connection points NU, NV, and NW are connected.

For convenience of description, let the wiring connecting the connection point MU and the connection point NU be a line 47u, let the wiring connecting the connection point MV and the connection point NV be a line 47v, and let the wiring connecting the connection point MW and the connection point NW be a line 47w.

(3) Operation of the motor drive device 10

Next, the operation of the motor drive device 10 will be described. In FIG. 11 , the control unit 40 outputs a waveform to the gate drive circuit 26 and controls the state of the waveform output to drive the motor 51 at a predetermined rotational speed.

FIG. 12A is a diagram showing how voltages are applied to the upper and lower arms when the motor drive device 10 is running, and FIG. 12B is a diagram showing how voltages are applied to the upper and lower arms when the motor driver 10 is stopped.

As shown in FIG. 12A, during operation, the transistor Q3a of the upper arm corresponding to the drive coil Lu, the transistor Q4b of the lower arm corresponding to the drive coil Lv, and the transistor Q5b of the lower arm corresponding to the drive coil Lw perform conduction operations. During this period, the DC voltage Vdc is applied to the transistors of each upper and lower arm that are turned off.

At this time, when the DC voltage Vdc becomes an excessive voltage, the excessive voltage is applied to the transistors Q3b, Q4a, Q5a and diodes D3b, D4a, D5a of the switching elements that are turned off. If the element withstand voltage of one switching element (transistors Q3a~Q5b and diodes D3a~D5b) is set to Vr, when the DC voltage Vdc>element withstand voltage Vr, the transistors Q3a~Q5b or diodes D3a~D5b of the switching element are The possibility of damage is high.

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

As a result, as shown in FIG. 2B , each of the two switching elements (transistors Q3a, Q3b, Q4a, Q4b, Q5a, Q5b, diodes D3a, D3b, D4a, D4b, D5a, D5b) to which the excessive voltage is connected in series terminal pressure. For example, the divided voltage value V1 is applied to both ends of the switching elements of the upper arm (transistors Q3a, Q4a, Q5a, diodes D3a, D4a, D5a), and the divided voltage value V2 is applied to the switching elements of the lower arm (transistors Q3b, Q4b, Q5b, Diodes D3b, D4b, D5b) both ends. Ideally, if the impedance of each switching element is equal, then V1=V2, therefore, the excess voltage applied to one switching element is reduced to half of that when either one is operating, thereby protecting each switching element (transistor Q3a ~ Q5b, diodes D3a ~ D5b) from damage.

However, in reality, the internal resistance (leakage current) of the switching elements (transistors Q3a, Q3b, Q4a, Q4b, Q5a, Q5b, diodes D3a, D3b, D4a, D4b, D5a, D5b) and the capacitance of the switching elements on both the upper and lower arms The ingredients are divided accordingly, so they don't become equally divided.

Therefore, as shown in FIG. 1, the balance circuits 33a, 33b correspond to switching elements (transistors Q3a, Q3b, diodes D3a, D3b), and the balance circuits 34a, 34b correspond to switching elements (transistors Q4a, Q4b, diodes D4a, D4b). The balance circuits 35a, 35b are connected so as to correspond to the switching elements (transistors Q5a, Q5b, diodes D5a, D5b).

Thus, the divided voltage value V1 applied to both ends of the switching elements (transistors Q3a, Q4a, Q5a, diodes D3a, D4a, D5a) of the upper arm and the switching element (transistors Q3b, Q4b, Q5b, diode D3b) of the lower arm can be made equal to each other. , D4b, D5b) the divided voltage value V2 at both ends is equal.

(4) Features of the first embodiment

(4-1)

In the motor drive device 10, when an overvoltage is generated, the control unit 40 turns off the transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of both the upper and lower arms, so that the overvoltage is applied to each of the two switching elements connected in series. Divide the voltage across both ends of the switching element (transistors Q3a~Q5b, diodes D3a~D5b) to reduce the excessive voltage to one half of the operation of any one, so it can protect the switching elements (transistors Q3a~Q5b, diodes D3a～D5b) are protected from damage.

(4-2)

The balance circuits 33a and 33b correspond to the transistors Q3a and Q3b and the diodes D3a and D3b, the balance circuits 34a and 34b correspond to the transistors Q4a and Q4b and the diodes D4a and D4b, and the balance circuits 35a and 35b correspond to the transistors Q5a and Q5b and the diodes D5a, D5b is connected in a corresponding manner, so the divided voltage value V1 applied to both ends of the switching elements (transistors Q3a, Q4a, Q5a, diodes D3a, D4a, D5a) of the upper arm and the switching elements (transistors Q3b, Q3b, The voltage division value V2 at both ends of Q4b, Q5b, diodes D3b, D4b, D5b) is equal, which can prevent the switching elements (transistors Q3a-Q5b and diodes D3a-D5b) from being damaged due to unequal voltage division.

(fifth embodiment)

(1) Summary

FIG. 13 is a block diagram showing a circuit configuration of a motor drive device 10 according to a second embodiment of the present invention. In FIG. 13 , the system 100 as a whole is constituted by the motor drive device 10 and the motor 51 .

In FIG. 13 , in the motor drive device 10 of the second embodiment, relay circuits 43 , 44 , and 45 are provided in addition to the fourth embodiment shown in FIG. 11 . Therefore, here, the relay circuits 43 , 44 , and 45 will be described, and since the other elements are the same as those of the first embodiment, the same names and numerals will be used, and detailed descriptions thereof will be omitted.

(2) Detailed structure of the motor drive device 10

(2-1) Relay circuits 43, 44, 45

The relay circuits 43, 44, 45 are used to open and close the lines 47u, 47v, 47w. Here, opening and closing the lines 47u, 47v, and 47w means connecting between the connection point MU and the connection point NU, between the connection point MV and the connection point NV, between the connection point MW and the connection point NW, Alternatively, the connection between the connection point MU and the connection point NU, between the connection point MV and the connection point NV, and between the connection point MW and the connection point NW is cut off.

The relay circuits 43, 44, 45 include relay contacts 43a, 44a, 45a, relay coils 43b, 44b, 45b, and transistors 43c, 44c, 45c.

Relay contacts 43a, 44a, 45a open and close lines 47u, 47v, 47w. The relay coils 43b, 44b, and 45b operate the relay contacts 43a, 44a, and 45a.

The transistors 43c, 44c, and 45c energize and de-energize the relay coils 43b, 44b, and 45b.

One end of the relay coils 43b, 44b, and 45b is connected to the positive electrode of the drive power supply Vb, and the other end is connected to the collector side of the transistors 43c, 44c, and 45c.

The control unit 40 switches the presence or absence of base currents of the transistors 43c, 44c, and 45c, turns on and off between collectors and emitters, and energizes and de-energizes the relay coils 43b, 44b, and 45b.

Normally, the relay circuits 43, 44, and 45 maintain the lines 47u, 47v, and 47w in a non-conductive state. And, when the respective bases of the transistors 43c, 44c, and 45c of the relay circuits 43, 44, and 45 are output from the control unit 40 with drive signals, the respective relay coils 43b, 44b, and 45b are excited, so that the relay contacts 43a, 44a , 45a operate in the direction of conducting the lines 47u, 47v, 47w.

(3) Operation of the motor drive device 10

Next, the operation of the motor drive device 10 will be described. Note that the control unit 40 is the same as the first embodiment up to the point at which the transistors Q3a to Q5b of both the upper and lower arms are turned off when the detection value of the voltage detection unit 23 is determined to exceed a predetermined threshold, and thus description thereof will be omitted.

When the control unit 40 turns off the transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of both the upper and lower arms, the balance circuits 33a, 33b are connected to the transistors Q3a, Q3b and the diodes D3a, D3b via the relay circuits 43, 44, and 45. Correspondence and balance circuits 34a and 34b are connected so that transistors Q4a and Q4b and diodes D4a and D4b correspond, and balance circuits 35a and 35b correspond to transistors Q5a and Q5b and diodes D5a and D5b.

Thus, the divided voltage value V1 applied to both ends of the switching elements (transistors Q3a, Q4a, Q5a, diodes D3a, D4a, D5a) of the upper arm and the switching element (transistors Q3b, Q4b, Q5b, diode D3b) of the lower arm can be made equal to each other. , D4b, D5b) the divided voltage value V2 at both ends is equal.

(4) Features of the fifth embodiment

(4-1)

In the motor drive device 10, when an excessive voltage is generated, by turning off the transistors Q3a to Q5b of both the upper and lower arms, each of the two switching elements (transistors Q3a to Q5b and diodes D3a to D5b) connected in series to the excessive voltage is Divide the voltage across both ends of the switching element (transistors Q3a~Q5b, diodes D3a~D5b) to reduce the excessive voltage to one half of the operation of either one, so the transistors Q3a~Q5b and diodes of the switching element can be protected. D3a～D5b are protected from damage.

(4-2)

When the control unit 40 turns off the transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b of both the upper and lower arms, the balance circuits 33a, 33b are connected to the transistors Q3a, Q3b and the diodes D3a, D3b via the relay circuits 43, 44, and 45. Correspondingly, the balance circuits 34a and 34b are connected in such a manner that the transistors Q4a and Q4b and the diodes D4a and D4b correspond, and the balance circuits 35a and 35b correspond to the transistors Q5a and Q5b and the diodes D5a and D5b, so that the switching elements applied to the upper arm can be The divided voltage value V1 across both ends (transistors Q3a, Q4a, Q5a, diodes D3a, D4a, D5a) and the divided voltage value V2 applied to both ends of the lower arm switching elements (transistors Q3b, Q4b, Q5b, diodes D3b, D4b, D5b) Evenly, it is possible to prevent destruction of the switching elements (transistors Q3a to Q5b and diodes D3a to D5b) due to unequal voltage division.

(4-3)

By arranging a switch between the connection point NU, NV, NW and the intermediate point of a pair of balanced circuits corresponding to said connection point NU, NV, NW and connecting the balanced circuit only when the inverter is off, it is possible to suppress the loss of the balanced circuit. power consumption.

That is, when there is no switch and the balance circuit is always connected, when the switching element of the inverter is turned on, since the DC voltage Vdc is applied to the balance circuit on the side of one arm, if, for example, the resistance of the balance circuit is If the value is set to R, the power consumption of the balance circuit is (Vdc)2/R, but in the state where the balance circuit is not connected, the power consumption of the balance circuit is (Vdc)2/2R, so the power consumption can be reduced to Suppressed at 1/2.

＜Other Embodiments＞

(A)

Instead of a relay, the switch may use a semiconductor switch such as a MOSFET. In this case, since the balance circuit can be connected at a higher speed, it is possible to quickly get rid of the state of uneven voltage division.

(B)

In order to further reduce power consumption compared to the second embodiment, a second switch for connecting/disconnecting the balancing circuit itself may be provided.

Fig. 14 is a diagram showing one side of voltage application to the upper and lower arms when the balance circuits 33a and 33b are connected after the motor drive device 10 of another embodiment is stopped. In Fig. 14, the second switch 47 generally sets the contact 47a as disconnected (opened) in advance, and the relay contact 43a of the relay circuit 43 is connected, and at the same time, the second switch 47 makes the contact 47a connected (closed), thereby The power consumption of the balance circuit in a normal state can be reduced to zero.

Industrial availability

The invention of the present application can protect the respective transistors of the upper and lower arms from overvoltage, and therefore is not limited to a motor drive device, but is also useful for other drive devices using an inverter.

Label description

10: Motor drive device;

20: Power supply department;

23: Voltage detection unit;

31: bootstrap circuit;

33a: balancing circuit;

33b: balance circuit;

34a: balancing circuit;

34b: balance circuit;

35a: balance circuit;

35b: balance circuit;

36: Insulated power supply;

40: control department;

43: relay circuit (switch);

44: relay circuit (switch);

45: relay circuit (switch);

50: overvoltage protection circuit;

51: motor;

61: braking circuit;

71: resistive load;

73: relay circuit (resistive load connection unit);

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.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2007-166815

Claims (6)

1. A motor driving device (10), wherein, the switching elements (Q3a, Q4a, Q5a) constituting the upper arm respectively corresponding to a plurality of phases (U, V, W) of the motor, and the The corresponding switching elements (Q3b, Q4b, Q5b) of the lower arm are connected in series, and voltages are output from the connection points (NU, NV, NW) formed thereby to the corresponding phases respectively, and the switching elements (Q3a, Q3b , Q4a, Q4b, Q5a, Q5b) and return diodes (D3a, D3b, D4a, D4b, D5a, D5b) are connected in parallel, wherein, The motor drive (10) has: a power supply unit (20), which rectifies the AC voltage output from the commercial power supply (91) to generate a DC power supply, and supplies a DC voltage (Vdc) to the upper and lower arms; a voltage detection part (23) connected in parallel with the upper and lower arms; and a control unit (40) for turning on and off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b), The control unit (40) turns the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of both the upper and lower arms to due. 2. The motor drive device (10) according to claim 1, wherein, The motor driving device (10) also has a braking circuit (61) of the motor, The control unit (40) brakes the motor after turning off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of both the upper and lower arms. 3. The motor drive device (10) according to claim 1 or 2, wherein the motor drive device (10) further has: resistive load (71); and a resistive load connection unit (73), which connects the connection point (NU, NV, NW) to the resistance load (71), or connects the connection point (NU, NV, NW) to the The connection between the resistive load (71) is cut off, The control unit (40) connects the connection points (NU, NV, NW) to the A resistive load (71) is connected. 4. The motor drive device (10) according to claim 1 or 2, wherein, The motor driving device (10) also has a mechanical brake (81), which can be disassembled relative to the rotating shaft of the motor, The control unit (40) mechanically brakes the motor after turning off the switching elements (Q3a, Q3b, Q4a, Q4b, Q5a, Q5b) of the upper and lower arms. 5. The motor drive device (10) according to claim 2, wherein, The control unit (40) does not perform the braking on the motor except when the detection value of the voltage detection unit (23) exceeds the threshold value. 6. The motor drive device (10) according to claim 1 or 2, wherein, The motor driver (10) further includes an isolated power supply (36) used to drive upper arm side switching elements (Q3a, Q4a, Q5a) of the upper and lower arms.

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