JP5817021B2 - Motor drive circuit and motor unit including the same - Google Patents

Description

  The present invention relates to a motor drive circuit and a motor unit including the same.

  The brushless DC motor can operate by being supplied with a drive voltage from an inverter circuit. Patent Document 1 discloses an inverter circuit that supplies a drive voltage to a brushless DC motor. The inverter circuit includes a plurality of switching elements for supplying a voltage to each coil of the brushless DC motor. There is a bootstrap method as a driving method of the switching element. The bootstrap system is a system in which a capacitor is connected to each of a plurality of switching elements, and the switching elements are turned on by electric charges accumulated in the capacitors.

JP 2003-158887 A

  In a general bootstrap system, there are few configurations in which measures against disturbance are taken. For example, a motor provided in an outdoor unit of an air conditioner performs a power generation operation when an impeller coupled to an output shaft of the motor rotates due to wind or the like in a state where no speed command signal is input to the inverter circuit. The regenerative voltage generated by the motor is supplied to the inverter circuit, and the voltage in the inverter circuit may increase.

The motor drive circuit disclosed in the present application includes an inverter circuit that supplies electric power to a coil provided in the motor, and a control circuit. The inverter circuit includes an upper arm side switching element connected between a terminal to which a motor voltage is applied and the coil, and a lower arm side switching element connected between the upper arm side switching element and a ground. . The control circuit includes a position detection unit, a switching control unit, and a bootstrap capacitor. The position detection unit detects a rotation position of the motor rotation unit and outputs a rotation position signal, and the switching control unit refers to a speed command voltage input from the outside and the rotation position signal, and switching the switching elements included in the inverter circuit on or off, the bootstrap capacitor, and electric power for driving the upper arm side switching element, the switching control unit refers to the rotational position signal Calculating the rotational frequency of the rotating part of the motor, and when the speed command voltage is equal to or higher than a predetermined voltage and the rotational frequency is lower than the predetermined rotational frequency , the lower arm side switching element is turned on for a predetermined time, run the charging of the bootstrap capacitor, after charging the bootstrap capacitor, the upper arm switching When the rotation frequency is equal to or higher than a predetermined number of rotations, the lower arm side switching element is turned off to stop the charging of the bootstrap capacitor, and the bootstrap capacitor is charged. After stopping, the upper arm switching element and the lower arm switching element are sequentially turned on or off .

The motor unit disclosed in the present application includes a motor, an inverter circuit, and a control circuit. The motor includes a stationary part that includes a coil and a rotating part that is rotatably supported by the stationary part. The inverter circuit includes an upper arm side switching element connected between a terminal to which a motor voltage is applied and the coil, and a lower arm side switching element connected between the upper arm side switching element and a ground. . The control circuit includes a position detection unit, a switching control unit, and a bootstrap capacitor. The position detection unit detects a rotation position of the motor rotation unit and outputs a rotation position signal, and the switching control unit refers to a speed command voltage input from the outside and the rotation position signal, and switching the switching elements included in the inverter circuit on or off, the bootstrap capacitor, and electric power for driving the upper arm side switching element, the switching control unit refers to the rotational position signal Calculating the rotational frequency of the rotating part of the motor, and when the speed command voltage is equal to or higher than a predetermined voltage and the rotational frequency is lower than the predetermined rotational frequency , the lower arm side switching element is turned on for a predetermined time, run the charging of the bootstrap capacitor, after charging the bootstrap capacitor, the upper arm switching When the rotation frequency is equal to or higher than a predetermined number of rotations, the lower arm side switching element is turned off to stop the charging of the bootstrap capacitor, and the bootstrap capacitor is charged. After stopping, the upper arm switching element and the lower arm switching element are sequentially turned on or off.

  ADVANTAGE OF THE INVENTION According to this invention, even if a motor performs electric power generation operation | movement by disturbance, it can prevent that a high voltage is applied to an inverter circuit.

FIG. 1 is a block diagram of a motor unit according to the present embodiment. FIG. 2 is a circuit diagram of the inverter circuit and the drive circuit according to the present embodiment. FIG. 3 is a flowchart of the motor unit according to the present embodiment. FIG. 4 is a timing chart of the motor unit according to the present embodiment. FIG. 5 is a modification of the motor unit according to the present embodiment.

(Embodiment 1)
[1. Configuration of motor drive circuit]
FIG. 1 is a block diagram of a motor unit according to the present embodiment. The motor unit includes a motor 1, an inverter circuit 2, and a control circuit 3. The control circuit 3 operates the inverter circuit 2. The inverter circuit 2 supplies a drive voltage to the motor 1. The motor unit includes a shunt resistor R1.

  The motor 1 is, for example, a brushless DC motor. The motor 1 includes a stationary part and a rotating part. The stationary part includes a stator core, a coil, and the like. The rotating unit includes a rotor core, a magnet, a shaft, and the like. The motor 1 includes a sensor 4 for detecting the rotational position of the rotating unit.

  The inverter circuit 2 includes a switching element. The inverter circuit 2 may include, for example, a transistor, a field effect transistor (FET), or an insulated gate bipolar transistor (IGBT) as a switching element. In the present embodiment, the inverter circuit 2 includes an FET as an example of a switching element. The number of switching elements is preferably proportional to the number of phases of the motor 1. For example, when the motor 1 is a three-phase motor, the inverter circuit 2 preferably includes six switching elements. In the present embodiment, since the motor 1 is a three-phase brushless DC motor, the inverter circuit 2 includes six switching elements.

  The control circuit 3 includes a triangular wave oscillation circuit 31, a comparator 32, a PWM signal generation unit 33, a timing control unit 34, an energization signal formation unit 35, a drive circuit 36, a comparator 37, a position detection unit 38, and a charge control unit 39. Prepare. The control circuit 3 can be composed of a control IC. The control circuit 3 can be driven by being supplied with a DC control voltage Vcc supplied from a control power supply. The control circuit 3 is applied with a speed command voltage Vsp from an external controller or the like. The control circuit 3 can operate the motor 1 at a speed according to the speed command voltage Vsp.

  The triangular wave oscillation circuit 31 outputs a triangular wave (sawtooth wave) signal.

  The comparator 32 compares the triangular wave signal output from the triangular wave oscillation circuit 31 with the speed command voltage Vsp input from the outside.

  The PWM signal generation unit 33 generates a PWM signal from the comparison result output from the comparator 32. Specifically, the PWM signal generation unit 33 refers to the comparison result output from the comparator 32, and the period in which the speed command voltage Vsp is larger than the triangular wave is the ON period, and the period in which the speed command voltage Vsp is smaller than the triangular wave. A pulse signal for an OFF period is generated.

  The timing control unit 34 refers to the rotational position signal output from the position detection unit 38 and adjusts the timing (for example, the rising timing) of the PWM signal output from the PWM signal generation unit 33. The timing control unit 34 can detect the terminal voltage of the shunt resistor R <b> 1 and calculate the value of the current flowing through the inverter circuit 2.

  The energization signal forming unit 35 generates an energization signal for driving the switching element 6 based on the PWM signal adjusted by the timing control unit 34. The energization signal forming unit 35 outputs the generated energization signal to the drive circuit 36.

  The drive circuit 36 refers to the energization signal output from the energization signal forming unit 35 and sends a signal to the inverter circuit 2 that can turn on / off the switching element of the inverter circuit 2. Specifically, the drive circuit 36 refers to the energization signal output from the energization signal forming unit 35 and generates a control signal to be applied to each of the six switching elements included in the inverter circuit 2. The drive circuit 36 sends the generated control signal to six switching elements included in the inverter circuit 2.

  The position detection unit 38 refers to the detection signal output from the sensor 4 and detects the rotation position of the rotation unit included in the motor 1. The position detection unit 38 sends information on the detected rotation position of the rotation unit to the timing control unit 34 as a rotation position signal.

  The charging control unit 39 controls the charging operation to the bootstrap capacitors C1 to C3 included in the drive circuit 36. Specifically, the charge control unit 36 refers to the position information detected by the position detection unit 38, and generates a charge control signal for charging the bootstrap capacitors C1 to C3 at a predetermined timing.

  The sensor 4 is included in the motor 1 and is disposed in the vicinity of the rotating unit. The sensor 4 preferably includes a plurality of sensor elements. In the present embodiment, the sensor 4 includes three sensor elements. The sensor elements included in the sensor 4 are preferably arranged at an interval of an electrical angle of 120 degrees around the rotation axis of the rotating part. The sensor 4 can detect the rotational position of the rotating part. The sensor 4 can be realized by, for example, a magnetic sensor that can detect the magnetic flux of a magnet included in the rotating unit, and can be realized by, for example, a Hall element. The number of sensors 4 is three in the present embodiment, but is not limited to this. The positions of the sensors 4 are arranged at intervals of 120 electrical angles in the present embodiment, but are not limited thereto.

  FIG. 2 is a circuit diagram of the inverter circuit 2 and the drive circuit 36. As shown in FIG. 2, the inverter circuit 2 includes six switching elements Q1 to Q6. In this specification, switching elements Q1, Q3, and Q5 are referred to as “upper arms”, and switching elements Q2, Q4, and Q6 are referred to as “lower arms”. The drive circuit 36 includes a first upper arm drive circuit 36a, a first lower arm drive circuit 36b, a second upper arm drive circuit 36c, a second lower arm drive circuit 36d, a third upper arm drive circuit 36e, A third lower arm drive circuit 36f, diodes D1 to D3, current limiting resistors R11 to R13, and bootstrap capacitors C1 to C3 are provided. Motor voltage Vm is applied to the drains of switching elements Q1, Q3 and Q5. Switching element Q1 has a gate connected to first upper arm drive circuit 36a and a source connected to the U-phase coil of motor 1 and the drain of switching element Q2. The switching element Q2 has a gate connected to the first lower arm drive circuit 36b and a source grounded. Switching element Q3 has a gate connected to second upper arm drive circuit 36c and a source connected to the V-phase coil of motor 1 and the drain of switching element Q4. The switching element Q4 has a gate connected to the second lower arm drive circuit 36d and a source grounded. Switching element Q5 has a gate connected to third upper arm drive circuit 36e, and a source connected to the W-phase coil of motor 1 and the drain of switching element Q6. The switching element Q6 has a gate connected to the third lower arm drive circuit 36f and a source grounded.

  The terminal UH is connected to the first upper arm drive circuit 36a. The terminal UL is connected to the first lower arm drive circuit 36b. The terminal VH is connected to the second upper arm drive circuit 36c. The terminal VL is connected to the second lower arm drive circuit 36d. The terminal WH is connected to the third upper arm drive circuit 36e. The terminal WL is connected to the third lower arm drive circuit 36f. The energization signal output from the energization signal forming unit 35 is input to the terminals UH to WL.

  The current limiting resistor R1 is connected to the anode of the diode D1. The current limiting resistor R2 is connected to the anode of the diode D2. The current limiting resistor R3 is connected to the anode of the diode D3. The current limiting resistors R1 to R3 are for preventing an overcurrent limiting operation from occurring due to the initial charging current of the bootstrap capacitors C1 to C3.

  Bootstrap capacitor C1 is connected between diode D1 and the source of switching element Q1. Bootstrap capacitor C2 is connected between diode D2 and the source of switching element Q3. Bootstrap capacitor D3 is connected between diode D3 and the source of switching element Q5. The diodes D1 to D3 are connected to a control voltage input terminal. Therefore, the bootstrap capacitor C1 is charged when the switching element Q1 is off and the switching element Q2 is on. When the switching element Q3 is off and the switching element Q4 is on, the bootstrap capacitor C2 is charged. When the switching element Q5 is off and the switching element Q6 is on, the bootstrap capacitor C3 is charged.

[2. Motor unit operation)
[2-1. Operation of motor unit)
FIG. 3 is a flowchart showing the operation of the motor unit. Hereinafter, the operation of the motor unit will be described with reference to FIG. The flow shown in FIG. 3 is based on the premise that the speed command voltage Vsp is not applied to the Vsp input terminal 40 and the motor 1 is stopped and the bootstrap capacitor charging operation is stopped. . Further, as an example, the motor unit of the present embodiment is a motor that rotates a fan mounted on an outdoor unit of an air conditioner. Therefore, an impeller is connected to the shaft of the motor 1 as a load. The outdoor unit operates based on a command from the indoor unit of the air conditioner.

  When the indoor unit of the air conditioner receives a signal including a command for switching the power supply from off to on from a remote controller or the like, the indoor unit sends an operation command to the external controller. When receiving the operation command, the external controller applies the speed command voltage Vsp to the Vsp input terminal 40 of the motor unit (S1).

  Next, the timing control unit 34 compares the speed command voltage Vsp with the reference voltage Vth. The timing control unit 34 continuously performs the comparison operation (S2).

  The charging control unit 39 refers to the rotation position signal sent from the position detection unit 38 and calculates the rotation frequency f of the rotation unit of the motor 1. The charge control unit 39 compares the calculated rotation frequency f with the reference frequency fth. The charge control unit 39 sends the frequency comparison result to the timing control unit 34 as a charge control signal. The reference voltage Vth only needs to be a value that can detect that the speed command voltage Vsp is applied. In the present embodiment, the reference voltage Vth is 2.1 volts as an example (S3).

  When the timing control unit 34 refers to the charge control signal and determines that the rotation frequency f is less than the reference frequency fth (YES determination in S3), the timing control unit 34 starts charging the bootstrap capacitors C1 to C3 included in the drive circuit 36. . The reference frequency fth may be a value that can detect that the rotation operation of the rotating portion of the motor 1 is stopped, and is set to 1 hertz as an example in the present embodiment. Further, the rotation frequency lower than the reference frequency fth includes a rotation frequency (0 Hz) when the rotating portion of the motor 1 is stopped. The timing control unit 34 includes a timer, and starts timing from the timing when charging of the bootstrap capacitors C1 to C3 is started (S4).

  Specifically, the timing control unit 34 sends a command to turn off the upper arm and turn on the lower arm in the inverter circuit 2 to the energization signal forming unit 35. The energization signal forming unit 35 generates a UH signal, a VH signal, and a WH signal for turning off the upper arm of the inverter circuit 2 based on a command from the timing control unit 34, and turns on the lower arm of the inverter circuit 2. The UL signal, the VL signal, and the WL signal are generated. The energization signal forming unit 35 sends the generated signal to the drive circuit 36.

  The first upper arm drive circuit 36a lowers the gate voltage of the switching element Q1 to turn off the switching element Q1. The second upper arm drive circuit 36c lowers the gate voltage of the switching element Q3 to turn off the switching element Q3. The third upper arm drive circuit 36e lowers the gate voltage of the switching element Q5 to turn off the switching element Q5. The first lower arm drive circuit 36b increases the gate voltage of the switching element Q2 to turn on the switching element Q2. The second lower arm drive circuit 36d increases the gate voltage of the switching element Q4 to turn on the switching element Q4. The third lower arm drive circuit 36f increases the gate voltage of the switching element Q6 to turn on the switching element Q6.

  As the switching elements Q1 and Q2 operate as described above, the drain of the switching element QQ2 becomes a low potential, so that the current based on the control voltage Vcc flows to the diode D1, the bootstrap capacitor C1, and the switching element Q2. The bootstrap capacitor C1 is charged. Further, since the switching elements Q3 and Q4 operate as described above to cause the drain of the switching element QQ4 to have a low potential, the current based on the control voltage Vcc is applied to the diode D2, the bootstrap capacitor C2, and the switching element Q4. The bootstrap capacitor C2 is charged. Further, since the switching elements Q5 and Q6 operate as described above, the drain of the switching element QQ6 becomes a low potential, so that the current based on the control voltage Vcc flows to the diode D3, the bootstrap capacitor C3, and the switching element Q6. The bootstrap capacitor C3 is charged.

  The timing control unit 34 determines whether or not the charging time of the bootstrap capacitors C1 to C3 has passed a predetermined charging time. Note that the predetermined charging time is preferably the shortest time required to complete the charging of the bootstrap capacitors C1 to C3 (reaching full charge). The predetermined charging time can be lengthened if the capacity of the bootstrap capacitors C1 to C3 is large, and can be shortened if the capacity is small. The predetermined charging time is 1.5 milliseconds as an example in the present embodiment (S5).

  When the timing controller 34 determines that the charging time of the bootstrap capacitors C1 to C3 has passed the predetermined charging time (YES determination in S5), the timing controller 34 stops the charging of the bootstrap capacitors C1 to C3. Specifically, the timing control unit 34 releases the state in which the upper arm in the inverter circuit 2 is turned off and the lower arm is turned on (S6).

  The timing control unit 34 sequentially turns on or off the switching elements Q1 to Q6 of the inverter circuit 2 to perform inverter control. The inverter circuit 2 performs inverter control and continues the operation of the motor 1 (S7).

  Hereinafter, a specific operation of the motor unit will be described.

  The comparator 32 compares the speed command voltage Vsp applied to the Vsp input terminal 40 with the triangular wave sent from the triangular wave oscillation circuit 31, and sends the comparison result to the PWM signal generation unit 33. The PWM signal generation unit 33 generates a PWM signal based on the comparison result sent from the comparator 32. Specifically, a pulse signal that is HIGH only during a period in which the speed command voltage Vsp exceeds the triangular wave value is generated. That is, the comparator 32 and the PWM signal generation unit 33 execute PWM control, and generate a pulse signal whose pulse width (duty ratio) is modulated according to the level of the speed command voltage Vsp. The PWM signal generation unit 33 sends a PWM signal (pulse signal) to the timing control unit 34.

  The timing control unit 34 refers to the PWM signal and the position signal sent from the position detection unit 38, and controls the rising timing of the PWM signal. The timing control unit 34 sends the PWM signal to the energization signal forming unit 35.

  The energization signal forming unit 35 refers to the PWM signal and generates an energization signal corresponding to the three-phase coil of the motor 1. Specifically, the energization signal forming unit 35 generates a U-phase UH signal and UL signal, a V-phase VH signal and VL signal, and a W-phase WH signal and WL signal. The energization signal forming unit 35 sends the generated signal to the drive circuit 36. The UH signal, the VH signal, and the WH signal are signals for operating the upper arm of the inverter circuit 2. The UL signal, the VL signal, and the WL signal are signals for operating the lower arm of the inverter circuit 2. The UH signal, the VH signal, and the WH signal have a phase difference of 120 degrees, for example. The UL signal, the VL signal, and the WL signal have a phase difference of 120 degrees, for example.

  The UH signal is input to the first upper arm drive circuit 36 a of the drive circuit 36. The first upper arm drive circuit 36a turns on or off the gate of the switching element Q1 based on the UH signal. The UL signal is input to the first lower arm drive circuit 36 b of the drive circuit 36. The first lower arm drive circuit 36b turns on or off the gate of the switching element Q2 based on the UL signal. The VH signal is input to the second upper arm drive circuit 36 c of the drive circuit 36. The second upper arm drive circuit 36c turns on or off the gate of the switching element Q3 based on the VH signal. The VL signal is input to the second lower arm drive circuit 36 d of the drive circuit 36. The second lower arm drive circuit 36d turns on or off the gate of the switching element Q4 based on the VL signal. The WH signal is input to the third upper arm drive circuit 36 e of the drive circuit 36. The third upper arm drive circuit 36e turns on or off the gate of the switching element Q5 based on the WH signal. The WL signal is input to the third lower arm drive circuit 36 f of the drive circuit 36. The third lower arm drive circuit 36f turns on or off the gate of the switching element Q6 based on the WL signal.

  The inverter circuit 2 can energize the three-phase coil of the motor 1 by selectively turning on and off the switching elements Q1 to Q6 to rotate the rotating portion of the motor 1. For example, when switching elements Q1 and Q4 are turned on, a current based on motor voltage Vm flows in the order of switching element Q1, U-phase coil, and switching element Q4. Further, by energizing switching elements Q3 and Q6, a current based on motor voltage Vm flows in the order of switching element Q3, V-phase coil, and switching element Q6. Further, by energizing switching elements Q5 and Q2, a current based on motor voltage Vm flows in the order of switching element Q5, W-phase coil, and switching element Q2.

  The bootstrap capacitor C1 is discharged at the timing when the switching element Q1 is turned on. The bootstrap capacitor C2 is discharged at the timing when the switching element Q3 is turned on. The bootstrap capacitor C3 is discharged at the timing when the switching element Q5 is turned on.

  On the other hand, the bootstrap capacitor C1 is charged at the timing when the switching element Q2 is turned on. The bootstrap capacitor C2 is charged at the timing when the switching element Q4 is turned on. The bootstrap capacitor C3 is charged at the timing when the switching element Q5 is turned on. Note that the timing at which the switching elements Q2, Q4, and Q6 are turned on has a phase difference of 120 degrees, so that the bootstrap capacitors C1 to C3 are charged with a period of 120 degrees.

  As the inverter circuit 2 operates as described above, the rotating portion of the motor 1 rotates at a rotation speed corresponding to the speed command voltage Vsp.

  FIG. 4 is a timing chart showing the driving operation of the motor 1 and the charging operation of the bootstrap capacitors C1 to C3 according to the present embodiment. FIG. 4A is a rotational position signal output from the position detection unit 38, and the HIGH period indicates a period during which the sensor 4 detects the magnetic flux of the magnet. FIG. 4B is a charge control signal output from the charge control unit 39, and the HIGH period is a period during which the bootstrap capacitors C1 to C3 are charged. FIG. 4C shows the speed command voltage Vsp.

  In FIG. 4, when the indoor unit of the air conditioner receives a signal including a command to switch the power source from off to on from a remote controller or the like, the indoor unit sends an operation command to the external controller. When receiving the operation command, the external controller applies the speed command voltage Vsp to the Vsp input terminal 40 of the motor unit (timing t1).

  When the timing control unit 34 compares the speed command voltage Vsp with the reference voltage Vth and determines that the speed command voltage Vsp exceeds the reference voltage Vth, the timing control unit 34 turns on the lower arm (switching elements Q2, Q4, Q6 shown in FIG. 2). Then, charging of the bootstrap capacitors C1 to C3 is started (timing t2).

  The timing control unit 34 measures time from timing t2 when charging of the bootstrap capacitors C1 to C3 is started. The timing control unit 34 stops the charging of the bootstrap capacitors C1 to C3 when a predetermined time T set in advance has elapsed from the timing t2 (timing t3).

  The timing control unit 34 causes the inverter circuit 2 to execute inverter control after the timing t3. The inverter circuit 2 starts the operation of the motor 1 by executing inverter control after the timing t3.

[2-2. Operation of the motor unit when the load rotates due to external factors)
Air conditioner outdoor units are often installed outdoors. In such an outdoor unit, when wind or the like blows on the impeller (load) when the motor is not operating, the impeller may rotate. When the impeller rotates due to an external factor (wind or the like) while the motor 1 is not operating, the rotating portion of the motor 1 connected to the impeller rotates. When the rotating part rotates, a regenerative voltage is generated in the stationary part of the motor 1.

  As shown in FIG. 3, the present embodiment includes a step (S2) of monitoring the speed command voltage Vsp and a step (S3) of monitoring the rotational frequency f of the motor 1 as one of the features. Yes. That is, in the present embodiment, when the speed command voltage Vsp is equal to or higher than the reference voltage Vth and the rotation frequency f of the motor 1 is higher than the reference frequency fth, the bootstrap capacitors C1 to C3 are not charged. That is, when the speed command voltage Vsp is applied while the impeller is rotating due to an external factor, the bootstrap capacitors C1 to C3 are not charged. With such a configuration, the bootstrap capacitors C1 to C3 are not charged when the motor 1 is operated while the impeller is rotated by an external factor (wind or the like), so that the voltage of the inverter circuit 2 is greatly increased. Can be prevented from rising.

  For example, in a flow in which there is no step for monitoring the speed command voltage Vsp, when the speed command voltage Vsp is applied to the motor unit when the impeller rotates due to an external factor, and the speed command voltage Vsp exceeds the reference voltage Vth, The bootstrap capacitor is charged. When the bootstrap capacitor is charged, the lower arm (switching elements Q2, Q4, Q6 shown in FIG. 2) is turned on. When the lower arm is turned on, the voltages at the nodes of the switching elements Q1 and Q2, the nodes of the switching elements Q3 and Q4, and the nodes of the switching elements Q5 and Q6 increase, and the rotating rotating part is braked. At this time, when the rotational speed of the rotating part rotating due to an external factor is high, a high value of the regenerative voltage is applied to the stationary part of the motor 1 and the motor voltage Vm of the inverter circuit 2 is increased. If the motor voltage Vm exceeds the withstand voltage of the inverter circuit 2, the switching element may be damaged.

[2-3. Operation of the motor unit when the motor stops due to an external factor)
When the power supply to the motor unit is interrupted while the motor unit is operating, the speed command voltage Vsp, the control voltage Vcc, and the motor voltage Vm are rapidly reduced.

  As shown in FIG. 3, the present embodiment includes a step (S2) of monitoring the speed command voltage Vsp and a step (S3) of monitoring the rotational frequency f of the motor 1 as one of the features. Yes. That is, in the present embodiment, when the speed command voltage Vsp is equal to or higher than the reference voltage Vth and the rotation frequency f of the motor 1 is higher than the reference frequency fth, the bootstrap capacitors C1 to C3 are not charged. With such a configuration, when the speed control signal Vsp is applied, when the power supply to the motor unit is cut off and the rotating portion of the motor 1 is rotated due to inertia or the like, the bootstrap capacitors C1 to C1. C3 is not charged. Therefore, it is possible to prevent the voltage of the inverter circuit 2 from significantly increasing.

  For example, in a flow that does not include the step of monitoring the speed command voltage Vsp and the step of monitoring the rotation frequency f of the motor 1, the power supply is cut off when the motor 1 is operating, and the speed command voltage Vsp is at the charge operation level. When the voltage decreases, the bootstrap capacitor is charged. When the bootstrap capacitor is charged, the lower arm (switching elements Q2, Q4, Q6 shown in FIG. 2) is turned on. When the lower arm is turned on, the voltages at the nodes of the switching elements Q1 and Q2, the nodes of the switching elements Q3 and Q4, and the nodes of the switching elements Q5 and Q6 increase, and the rotating portion of the motor 1 is braked. At this time, when the rotational speed of the rotating part immediately before the brake is applied is high, the regenerative voltage generated in the stationary part of the motor 1 becomes high. When the regenerative voltage increases, the motor voltage Vm of the inverter circuit 2 increases. If the motor voltage Vm exceeds the withstand voltage of the inverter circuit 2, the switching element may be damaged.

[3. Effects of the embodiment, etc.]
The motor unit according to the present embodiment includes a step (S2) of monitoring the speed command voltage Vsp and a step (S3) of monitoring the rotational frequency f of the rotating part of the motor 1 in the drive flow. The motor unit charges the bootstrap capacitors C1 to C3 when the speed command voltage Vsp is equal to or higher than the reference voltage Vth and the rotation frequency f is lower than the reference frequency fth. With such a configuration, even if the speed command voltage Vsp is applied when a load such as an impeller connected to the motor 1 is rotating due to an external factor such as wind, the bootstrap capacitors C1 to C3 Since charging is not performed, generation of a high regenerative voltage in the motor 1 can be prevented. Therefore, an increase in voltage in the inverter circuit 2 can be prevented, and damage to the switching element included in the inverter circuit 2 can be prevented.

  Further, even if the power supply is interrupted while the motor 1 is in operation and the speed command voltage Vsp is suddenly reduced, the bootstrap capacitors C1 to C3 are not charged, so that a high regenerative voltage is prevented from being generated in the motor 1. it can. Therefore, an increase in voltage in the inverter circuit 2 can be prevented, and damage to the switching element included in the inverter circuit 2 can be prevented.

  In the present embodiment, the timing control unit 34 includes a timer that monitors the charging time of the bootstrap capacitors C1 to C3. Thereby, since the timing control part 34 performs the charging operation to the bootstrap capacitors C1-C3 only for a predetermined time, it can reduce power consumption.

  In this embodiment, the charging time of the bootstrap capacitors C1 to C3 is 1.5 milliseconds, but this value is necessary charge when the capacity of the bootstrap capacitors C1 to C3 is 1 microfarad (an example). This is the shortest time required to secure the quantity. The required charge amount is not limited to full charge, and the charge time may be intentionally shortened (for example, 0.5 milliseconds) in order to suppress a reduction in power consumption.

  In the present embodiment, the sensor 4 is used to detect the rotation frequency of the rotating portion of the motor 1. However, the configuration may be such that the induced voltage generated in the motor 1 is detected to detect the rotating frequency of the rotating portion. Good. FIG. 5 shows a modification of the motor unit according to the present embodiment. The motor unit shown in FIG. 5 further includes a detection circuit 41 in addition to the motor unit shown in FIG. The detection circuit 41 can detect an induced voltage generated in the motor 1. The detection circuit 41 sends the detected induced voltage value to the position detection unit 38. The position detector 38 detects the frequency of the induced voltage from the value of the induced voltage sent from the detection circuit 41. The position detection unit 38 sends the frequency of the induced voltage to the timing control unit 34. The timing control unit 34 compares the frequency of the induced voltage with the reference voltage frequency. The timing control unit 34 determines that the rotating unit of the motor 1 is stopped when the frequency of the induced voltage is lower than the reference voltage frequency. The timing control unit 34 uses the determination result as a determination criterion in the determination step S3 in FIG.

  The control circuit 3 may be configured not to supply power to the coils connected to the bootstrap capacitors C1 to C3 when the amount of charge of the bootstrap capacitors C1 to C3 is less than a predetermined value. Such a configuration can be realized by providing a low voltage protection circuit.

  Further, the motor drive circuit can be configured to include a package IC including the control circuit 3 and a package IC including the inverter circuit 2. Further, the motor drive circuit can include a package IC including the inverter circuit 2 and the control circuit 3. The motor drive circuit includes a triangular wave oscillation circuit 31, a comparator 32, a PWM signal generation unit 33, a timing control unit 34, an energization signal formation unit 35, a comparator 37, a position detection unit 38, and a charge control unit 39. An IC and a package IC including the inverter circuit 2 and the drive circuit 36 can be provided. That is, the inverter circuit 2 and the configuration included in the control circuit 3 can be packaged in an IC in any combination.

  Further, the substrate on which the motor drive circuit is mounted may be disposed inside the motor 1, may be supported on the outer surface of the motor 1, or may be independent from the motor 1.

  The present invention is useful for a motor drive circuit and a motor unit including the same.

DESCRIPTION OF SYMBOLS 1 Motor 2 Inverter circuit 3 Inverter control circuit 4 Sensor 31 Triangular wave oscillation circuit 32 Comparator 33 PWM signal generation part 34 Timing control part 35 Energization signal formation part 36 Drive circuit 37 Comparator 38 Position detection part 39 Charging control part 40 Vsp input terminal 41 Detection circuit

Claims (8)

An inverter circuit for supplying power to the coil of the motor;
A control circuit;
With
The inverter circuit is
An upper arm side switching element connected between a terminal to which a motor voltage is applied and the coil;
A lower arm switching element connected between the upper arm switching element and the ground,
The control circuit includes a position detection unit, a switching control unit, and a bootstrap capacitor,
The position detection unit detects a rotation position of the motor rotation unit, and outputs a rotation position signal;
The switching control unit refers to a speed command voltage input from the outside and the rotational position signal, and switches a switching element included in the inverter circuit on or off ,
The bootstrap capacitor stores electric power for driving the upper arm side switching element ,
The switching controller is
Referring to the rotational position signal, the rotational frequency of the rotating part of the motor is calculated,
When the speed command voltage is equal to or higher than a predetermined voltage and the rotation frequency is lower than the predetermined rotation frequency , the lower arm side switching element is turned on, and the bootstrap capacitor is charged for a predetermined time, and the boot After charging the strap capacitor, the upper arm switching element and the lower arm switching element are sequentially turned on or off,
When the rotation frequency is equal to or higher than a predetermined number of rotations, the lower arm switching element is turned off to stop charging the bootstrap capacitor, and after stopping the bootstrap capacitor charging, the upper arm switching element and the lower arm switching element A motor drive circuit that sequentially turns on and off .
The motor drive circuit according to claim 1,
The switching control unit, it calculates the rotation frequency by referring to the induced voltage of the motor, the motor drive circuit.
The motor drive circuit according to claim 1,
The switching controller is
A PWM signal generator for generating a PWM signal from the speed command signal;
A timing control unit for adjusting the timing of the PWM signal;
An energization signal forming unit that generates an energization signal with reference to a PWM signal output from the timing control unit;
And a drive circuit that switches the upper arm side switching element and the lower arm side switching element on or off using the energization signal.
The motor drive circuit according to claim 3 ,
The drive circuit is
An upper arm side switching control circuit for switching the upper arm side switching element on or off;
A lower arm side switching control circuit for switching the lower arm side switching element on or off;
A motor drive circuit comprising the bootstrap capacitor.
A motor, an inverter circuit, and a control circuit;
The motor is
A stationary part comprising a coil;
A rotating part rotatably supported by the stationary part,
The inverter circuit is
An upper arm side switching element connected between a terminal to which a motor voltage is applied and the coil;
A lower arm switching element connected between the upper arm switching element and the ground,
The control circuit includes a position detection unit, a switching control unit, and a bootstrap capacitor,
The position detection unit detects a rotation position of the motor rotation unit, and outputs a rotation position signal;
The switching control unit refers to a speed command voltage input from the outside and the rotational position signal, and switches a switching element included in the inverter circuit on or off ,
The bootstrap capacitor stores electric power for driving the upper arm side switching element ,
The switching controller is
Referring to the rotational position signal, the rotational frequency of the rotating part of the motor is calculated,
When the speed command voltage is equal to or higher than a predetermined voltage and the rotation frequency is lower than the predetermined rotation frequency , the lower arm side switching element is turned on, and the bootstrap capacitor is charged for a predetermined time, and the boot After charging the strap capacitor, the upper arm switching element and the lower arm switching element are sequentially turned on or off,
When the rotation frequency is equal to or higher than a predetermined number of rotations, the lower arm switching element is turned off to stop charging the bootstrap capacitor, and after stopping the bootstrap capacitor charging, the upper arm switching element and the lower arm switching element A motor unit that turns on and off sequentially .
The motor unit according to claim 5 ,
An induced voltage detector that detects an induced voltage generated in the stationary part,
The switching control unit, it calculates the rotation frequency using the detected induced voltage in the induced voltage detection unit, the motor unit.
The motor unit according to claim 5 ,
The switching controller is
A PWM signal generator for generating a PWM signal from the speed command signal;
A timing control unit for adjusting the timing of the PWM signal;
An energization signal forming unit that generates an energization signal with reference to a PWM signal output from the timing control unit;
And a drive circuit that switches the upper arm side switching element and the lower arm side switching element on or off using the energization signal.
The motor unit according to claim 7 ,
The drive circuit is
An upper arm side switching control circuit for switching the upper arm side switching element on or off;
A lower arm side switching control circuit for switching the lower arm side switching element on or off;
A motor unit comprising the bootstrap capacitor.

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