CN103259468B - Motor drive circuit and there is the motor unit of this motor drive circuit - Google Patents

Abstract

The present application discloses a motor driving circuit and a motor unit having the motor driving circuit, wherein the motor driving circuit has an inverter circuit and a control circuit. The inverter circuit supplies power to the coils in the motor. The inverter circuit has an upper arm side switching element and a lower arm side switching element. The upper arm side switching element is connected between the terminal to which the motor voltage is applied and the coil. The lower arm side switching element is connected between the upper arm side switching element and the ground. The control circuit has a switch control unit and a bootstrap capacitor. The switch control unit switches the switching element included in the inverter circuit on or off with reference to the speed command voltage input from the outside and the detection signal. The bootstrap capacitor can store electric power for driving the switching element on the upper arm side. When the speed command voltage becomes equal to or higher than a predetermined voltage, the switch control unit charges the bootstrap capacitor for a predetermined time.

Description

Motor drive circuit and motor unit having the same

technical field

The invention relates to a motor drive circuit and a motor unit with the motor drive circuit.

Background technique

A brushless DC motor can be operated by being supplied with a drive voltage from an inverter circuit. Japanese Laid-Open Publication No. 2003-158887 discloses an inverter circuit for supplying a driving voltage to a brushless DC motor. The inverter circuit has a plurality of switching elements for supplying voltages to the respective coils of the brushless DC motor. There is a bootstrap boot method for driving the switching elements. In the bootstrap boot method, capacitors are connected to each of the plurality of switching elements, and the switching elements are turned on by charges stored in the capacitors.

Contents of the invention

In the general bootstrap boot method, there are few structures as countermeasures against disturbance. For example, in a motor installed in an outdoor unit of an air conditioner, when an impeller connected to an output shaft of the motor is rotated by wind or the like in a state where a speed command signal is not input to an inverter circuit, the motor operates to generate electricity. Since the regenerative voltage generated by the motor power generation is supplied to the inverter circuit, the voltage of the inverter circuit may increase.

The motor drive circuit disclosed in this application has an inverter circuit and a control circuit. The inverter circuit supplies power to the coils installed in the motor. The inverter circuit has an upper arm side switching element and a lower arm side switching element. The upper arm side switching element is connected between the terminal to which the motor voltage is applied and the coil. The lower arm side switching element is connected between the upper arm side switching element and the ground. The control circuit has a switch control unit and a bootstrap capacitor. The switch control unit switches the switching element included in the inverter circuit on or off with reference to the speed command voltage input from the outside and the detection signal. The bootstrap capacitor can store electric power for driving the switching element on the upper arm side. When the speed command voltage becomes equal to or higher than a predetermined voltage, the switch control unit charges the bootstrap capacitor for a predetermined time.

In the motor drive circuit disclosed in the present application, the switch control unit calculates the rotation frequency of the motor, and compares the rotation frequency with a predetermined rotation frequency. When the rotation frequency does not reach a predetermined rotation frequency, charging of the bootstrap capacitor is performed.

In the motor drive circuit disclosed in the present application, the switch control unit calculates the rotation frequency by referring to the induced voltage of the motor, and compares the rotation frequency with a predetermined rotation frequency. When the rotation frequency does not reach a predetermined rotation frequency, charging of the bootstrap capacitor is performed.

In the motor drive circuit disclosed in the present application, the switch control unit includes a PWM signal generation unit, a timing control unit, an energization signal formation unit, and a drive circuit. The PWM signal generator generates a PWM signal from the speed command signal. The timing control unit adjusts the timing of the PWM signal. The energization signal forming unit generates the energization signal by referring to the PWM signal output from the timing control unit. The drive circuit switches the upper arm side switching element and the lower arm side switching element on or off using the energization signal.

In the motor drive circuit disclosed in the present application, the drive circuit has an upper arm side switch control circuit, a lower arm side switch control circuit, and a bootstrap capacitor. The upper arm switch control circuit switches the upper arm switch element on or off. The lower arm switch control circuit switches the lower arm switch element on or off.

A motor unit disclosed in the present application has a motor, an inverter circuit, and a control circuit. The motor includes a stationary part having a coil and a rotating part rotatably supported by the stationary part. The inverter circuit has an upper arm side switching element and a lower arm side switching element. The upper arm side switching element is connected between the terminal to which the motor voltage is applied and the coil. The lower arm side switching element is connected between the upper arm side switching element and the ground. The control circuit has a switch control unit and a bootstrap capacitor. The switch control unit switches the switching element included in the inverter circuit on or off with reference to the speed command voltage input from the outside and the detection signal. The bootstrap capacitor can store electric power for driving the switching element on the upper arm side. When the speed command voltage becomes equal to or higher than a predetermined voltage, the switch control unit charges the bootstrap capacitor for a predetermined time.

In the motor unit disclosed in the present application, the motor has a position detection unit. The position detecting unit detects the rotational position of the rotating unit and outputs a detection signal. The switch control unit calculates the rotation frequency using the detection signal, and compares the rotation frequency with a predetermined rotation frequency. When the rotation frequency does not reach a predetermined rotation frequency, charging of the bootstrap capacitor is performed.

The motor unit disclosed in the present application further includes an induced voltage detection unit. The induced voltage detection unit detects the induced voltage generated in the static unit. The switch control unit calculates the rotation frequency using the induced voltage detected by the induced voltage detection unit, and compares the rotation frequency with a predetermined rotation frequency. When the rotation frequency does not reach a predetermined rotation frequency, charging of the bootstrap capacitor is performed.

In the motor unit disclosed in the present application, the switching control unit includes a PWM signal generating unit, a timing control unit, an energization signal forming unit, and a drive circuit. The PWM signal generator generates a PWM signal from the speed command signal. The timing control unit adjusts the timing of the PWM signal. The energization signal forming unit generates the energization signal by referring to the PWM signal output from the timing control unit. The drive circuit switches the upper arm side switching element and the lower arm side switching element on or off using the energization signal.

The drive circuit of the motor unit disclosed in the present application includes an upper arm side switch control circuit, a lower arm side switch control circuit, and a bootstrap capacitor. The upper arm switch control circuit switches the upper arm switch element on or off. The lower arm switch control circuit switches the lower arm switch element on or off.

According to one embodiment exemplified in the present application, even if the motor performs power generation operation due to noise, it is possible to prevent high voltage from being applied to the inverter circuit.

Description of drawings

FIG. 1 is a block diagram of a motor unit according to the present embodiment.

FIG. 2 is a circuit diagram of an inverter circuit and a 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 shows a modified example of the motor unit according to the present embodiment.

detailed description

<Embodiment 1>

1. The structure of the motor drive circuit

FIG. 1 is a block diagram of a motor unit according to one embodiment of the present embodiment. The motor unit has 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 has a shunt resistor R1.

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

The inverter circuit 2 has switching elements. The inverter circuit 2 may also have, for example, transistors, field effect transistors (FETs), and insulated gate bipolar transistors (IGBTs) as switching elements. In this embodiment, the inverter circuit 2 has a field effect transistor as an example of a switching element. The number of switching elements is preferably a number 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 has six switching elements. In this embodiment, since the motor 1 is a three-phase brushless DC motor, the inverter circuit 2 has six switching elements.

The control circuit 3 has a triangular wave oscillation circuit 31 , a comparator 32 , a PWM signal generator 33 , a timing controller 34 , an energization signal generator 35 , a drive circuit 36 , a comparator 37 , a position detector 38 and a charging controller 39 . The control circuit 3 can be constituted by 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 sent from an external controller or the like. The control circuit 3 operates the motor 1 at a speed following 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 from the triangular wave oscillation circuit 31 with the speed command voltage Vsp input from the outside.

The PWM signal generator 33 generates a PWM signal from the comparison result output from the comparator 32 . Specifically, the PWM signal generator 33 refers to the comparison result output from the comparator 32 to generate a pulse signal whose on-period is defined as a period in which the speed command voltage Vsp is larger than the triangular wave, and in a period in which the speed command voltage Vsp is smaller than the triangular wave. for the disconnection period.

The timing control unit 34 adjusts the timing (for example, rising edge timing) of the PWM signal output from the PWM signal generating unit 33 with reference to the rotational position signal output from the position detecting unit 38 . The timing control unit 34 can detect the terminal voltage of the shunt resistor R1 to 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 to the inverter circuit 2 a signal capable of controlling ON/OFF of the switching elements of the inverter circuit 2 . Specifically, the drive circuit 36 generates control signals with reference to the energization signal output from the energization signal forming unit 35 , and the control signals are applied to the six switching elements included in the inverter circuit 2 . The drive circuit 36 sends the generated control signal to the six switching elements included in the inverter circuit 2 .

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

The charging control unit 39 controls the charging operation of 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 to generate a charge control signal for charging the bootstrap capacitors C1 to C3 at predetermined timing.

The sensor 4 is included in the motor 1 and arranged near the rotating portion. The sensor 4 preferably comprises a plurality of sensor elements, in the present embodiment three sensor elements. The sensor elements included in the sensor 4 are arranged at intervals of an electrical angle of 120 degrees around the rotation axis of the rotary unit. 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 detects the magnetic flux of a magnet included in the rotating unit. For example, Hall elements are used as magnetic sensors. In addition, although the number of objects of the sensor 4 is three in this embodiment, it is not limited to this. The positions of the sensors 4 are arranged at intervals of an electrical angle of 120 degrees in the present embodiment, but the present invention is 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 has six switching elements Q1 to Q6. In addition, in this specification, the switching elements Q1, Q3, and Q5 are referred to as "upper arms", and the switching elements Q2, Q4, and Q6 are referred to as "lower arms." The drive circuit 36 has 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, a diode D1～D3, current limiting resistors R11～R13 and bootstrap capacitors C1～C3. A motor voltage Vm is applied to the drains of the switching elements Q1, Q3, and Q5. In the switching element Q1, the gate is connected to the first upper arm drive circuit 36a, and the source is connected to the U-phase coil of the motor 1 and the drain of the switching element Q2. In the switching element Q2, the gate is connected to the first lower arm drive circuit 36b, and the source is grounded. In the switching element Q3, the gate is connected to the second upper arm drive circuit 36c, and the source is connected to the V-phase coil of the motor 1 and the drain of the switching element Q4. In the switching element Q4, the gate is connected to the second lower arm drive circuit 36d, and the source is grounded. In the switching element Q5, the gate is connected to the third upper arm drive circuit 36e, and the source is connected to the W-phase coil of the motor 1 and the drain of the switching element Q6. In the switching element Q6, the gate is connected to the third lower arm drive circuit 36f, and the source is 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 R11 is connected to the anode of the diode D1. The current limiting resistor R12 is connected to the anode of the diode D2. The current limiting resistor R13 is connected to the anode of the diode D3. The current limiting resistors R11~R13 prevent the occurrence of overcurrent limiting operation through the initial charging current of the bootstrap capacitors C1~C3.

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

2. Operation of the motor unit

2-1. Operation of the 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. 3 . In addition, the flow shown in FIG. 3 assumes that the motor 1 is stopped without the speed command voltage Vsp being applied to the Vsp input terminal 40, and the charging operation of the bootstrap capacitor is stopped. Moreover, as an example, the motor unit of this embodiment is a motor which rotates the fan mounted in the outdoor unit of an air conditioner. Therefore, an impeller is connected to the shaft of the motor 1 as a load. In addition, the outdoor unit operates based on a command from the indoor unit of the air conditioner.

The indoor unit of the air conditioner transmits an operation command to an external controller after receiving a signal including a command to switch the power supply from off to on from a remote controller or the like. After 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 sequence control unit 34 continues to execute the comparison operation ( S2 ).

The charging control unit 39 refers to the rotational position signal sent from the position detection unit 38 to calculate the rotational frequency f of the rotating portion of the motor 1 . The charging control unit 39 compares the calculated rotation frequency f with the reference frequency fth. The charging control unit 39 sends the frequency comparison result to the timing control unit 34 as a charging control signal. In addition, the reference voltage Vth is only required to be a value capable of detecting the application of the speed command voltage Vsp, and is 2.1 volts as an example in the present embodiment ( S3 ).

When the timing control unit 34 determines with reference to the charge control signal that the rotation frequency f has not reached the reference frequency fth (YES in S3 ), it starts charging the bootstrap capacitors C1 to C3 included in the drive circuit 36 . In addition, the reference frequency fth should just be a value which can detect the stoppage of the rotation operation of the rotating part of the motor 1, and it is 1 Hz as an example in this embodiment. In addition, the rotation frequency less than the reference frequency fth includes the rotation frequency (0 Hz) when the rotating part of the motor 1 is stopped. Furthermore, the timing control unit 34 has a timer, and starts counting 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 of 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 generates a UL signal for turning on the lower arm of the inverter circuit 2. VL signal and WL signal. 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 raises 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.

Since the switching elements Q1 and Q2 operate as described above, since the drain of the switching element Q2 becomes a low potential, a current based on the control voltage Vcc flows through the diode D1, the bootstrap capacitor C1, and the switching element Q2, and the bootstrap capacitor C1 being charged. Furthermore, since the switching elements Q3 and Q4 operate as described above, since the drain of the switching element Q4 becomes a low potential, a current based on the control voltage Vcc flows through the diode D2, the bootstrap capacitor C2, and the switching element Q4, thereby bootstrapping Capacitor C2 is charged. Furthermore, since the switching elements Q5 and Q6 operate as described above, since the drain of the switching element Q6 becomes a low potential, a current based on the control voltage Vcc flows through the diode D3, the bootstrap capacitor C3, and the switching element Q6, thereby bootstrapping 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. In addition, the predetermined charging time is preferably the shortest time for the bootstrap chargers C1 to C3 to complete charging (full charge). The larger the capacity of the bootstrap capacitors C1-C3 is, the longer the predetermined charging time is, and the smaller the capacity is, the shorter the predetermined charging time is. In an example of this embodiment, the predetermined charging time is 1.5 milliseconds ( S5 ).

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

The timing control unit 34 sequentially turns on and off the switching elements Q1 to Q6 of the inverter circuit 2 to perform inverter control. The inverter circuit 2 executes the inverter control, so that the motor 1 continues to operate (S7).

The specific operation of the motor unit will be described below.

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 generator 33 . The PWM signal generator 33 generates a PWM signal based on the comparison result sent from the comparator 32 . Specifically, a pulse signal that is at a high level is transmitted only while the speed command voltage Vsp exceeds the value of the triangular wave. That is, the comparator 32 and the PWM signal generator 33 perform PWM control to 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 the PWM signal (pulse signal) to the timing control unit 34 .

The timing control unit 34 controls the rising edge timing of the PWM signal with reference to the PWM signal and the position signal transmitted from the position detection unit 38 . The timing control unit 34 sends the PWM signal to the energization signal forming unit 35 .

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

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 36d 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 rotate the rotating part of the motor 1 by selectively turning on and off the switching elements Q1 to Q6 to energize the three-phase coils of the motor 1 . For example, by turning on switching elements Q1 and Q4 , a current based on motor voltage Vm flows through switching element Q1 , the U-phase coil, and switching element Q4 sequentially. Then, by energizing switching elements Q3 and Q6 , a current based on motor voltage Vm flows through switching element Q3 , the V-phase coil, and switching element Q6 sequentially. Then, by energizing switching elements Q5 and Q2 , a current based on motor voltage Vm flows through switching element Q5 , the W-phase coil, and switching element Q2 sequentially.

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. In addition, since the switching elements Q2 , Q4 , and Q6 are turned on with a phase difference of 120 degrees, the bootstrap capacitors C1 to C3 are charged at a cycle of 120 degrees.

By operating the inverter circuit 2 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 operation of the motor 1 and the charging operation of the bootstrap capacitors C1 to C3 according to the present embodiment. FIG. 4( a ) shows the rotational position signal output from the position detector 38 , and the high period indicates a period in which the sensor 4 detects the magnetic flux of the magnet. FIG. 4( b ) is a charging control signal output by the charging control unit 39 , and the high period is a period in which charging of the bootstrap capacitors C1 to C3 is performed. FIG. 4( c ) shows the speed command voltage Vsp.

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

The timing control unit 34 compares the speed command voltage Vsp with the reference voltage Vth, and if it judges that the speed command voltage Vsp exceeds the reference voltage Vth, it turns on the lower arm (switching elements Q2, Q4, and Q6 shown in FIG. 2 ) to bootstrap the capacitor C1 ~ C3 start charging. (timing t2)

The timing control unit 34 starts counting time from timing t2 when charging of the bootstrap capacitors C1 to C3 starts. When the preset predetermined time T has elapsed from timing t2 , the timing control unit 34 stops charging of the bootstrap capacitors C1 to C3 (timing t3 ).

The sequence control unit 34 performs inverter control on the inverter circuit 2 after the sequence t3. The inverter circuit 2 performs inverter control after timing t3 to start the operation of the motor 1 .

2-2. Operation of the motor unit when the load rotates due to external factors

The outdoor unit of the air conditioner is mostly installed outside the house. In such an outdoor unit, if wind or the like blows to the impeller (load) while the motor is not operating, the impeller rotates. When the motor 1 is not in operation, if the impeller rotates due to external factors (wind, etc.), the rotating part of the motor 1 connected to the impeller also rotates. When the rotating part rotates, a regenerative voltage is generated in the stationary part of the motor 1 .

One of the characteristics of this embodiment is that, as shown in FIG. 3 , a step ( S2 ) of monitoring the speed command voltage Vsp and a step ( S3 ) of monitoring the rotation frequency f of the motor 1 are included. 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, when the motor 1 is operated while the impeller is rotating due to external factors (wind, etc.), since the bootstrap capacitors C1 to C3 are not charged, the voltage of the inverter circuit 2 can be prevented from greatly increasing.

For example, in a flow without the step of monitoring the speed command voltage Vsp, when the impeller rotates due to external factors, the speed command voltage Vsp is applied to the motor unit, and the bootstrap capacitor is charged when the speed command voltage Vsp exceeds the reference voltage Vth. While the bootstrap capacitor is charging, the lower arm (switching elements Q2, Q4, Q6 shown in Figure 2) is turned on. When the lower arm is turned on, the voltages at the node of switching elements Q1 and Q2, the node of switching elements Q3 and Q4, and the node of switching elements Q5 and Q6 rise, thereby applying braking to the rotating rotating part. At this time, when the rotation speed of the rotating part rotating due to external factors is high, a high regenerative voltage is applied to the stationary part of the motor 1, and 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.

2-3. Action of the motor unit after the motor stops due to external factors

When the power supply to the motor unit is cut off during the operation of the motor unit, the speed command voltage Vsp, the control voltage Vcc, and the motor voltage Vm drop rapidly.

One of the characteristics of this embodiment is that, as shown in FIG. 3 , a step ( S2 ) of monitoring the speed command voltage Vsp and a step ( S3 ) of monitoring the rotational frequency f of the motor 1 are included. 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, if the power supply to the motor unit is cut off and the rotating part of the motor 1 rotates due to inertia or the like, the bootstrap capacitors C1 to C3 are not charged. Therefore, it is possible to prevent the voltage of the inverter circuit 2 from increasing significantly.

For example, in the flow without the step of monitoring the speed command voltage Vsp and the step of monitoring the rotation frequency f of the motor 1, when the motor 1 is running, the power supply is cut off, the speed command voltage Vsp drops to the charging operation level, and bootstrap is performed. charging of the capacitor. When the bootstrap capacitor is charged, the lower arm (switching elements Q2, Q4, Q6 shown in Figure 2) is turned on. When the lower arm is turned on, the voltage at the node of switching elements Q1 and Q2 , the node of switching elements Q3 and Q4 , and the node of switching elements Q5 and Q6 rises, and braking is applied to the rotating part of motor 1 . At this time, when the rotational speed of the rotating portion is high immediately before the brake is applied, the regenerative voltage generated at the stationary portion of the motor 1 increases. 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 Embodiments and Others

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 rotation frequency f of the rotating part of the motor 1 in the driving flow. In the motor unit, the bootstrap capacitors C1 to C3 are charged 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 structure, when the load such as the impeller connected to the motor 1 rotates due to external factors such as wind, even if the speed command voltage Vsp is applied, the bootstrap capacitors C1 to C3 are not charged, thereby preventing the motor 1 from generating a high voltage. regenerative voltage. Therefore, it is possible to prevent a voltage rise in the inverter circuit 2 and prevent damage to switching elements included in the inverter circuit 2 .

In addition, even if the motor 1 is powered off during operation and the speed command voltage Vsp drops rapidly due to this, it is possible to prevent a high regenerative voltage from being generated in the motor 1 by charging the bootstrap capacitors C1 to C3. Therefore, it is possible to prevent a voltage rise in the inverter circuit 2 and to prevent damage to switching elements included in the inverter circuit 2 .

Furthermore, in the present embodiment, the timing control unit 34 has a timer for monitoring the charging time of the bootstrap capacitors C1 to C3. Accordingly, the timing control unit 34 can reduce power consumption by limiting the charging operation of the bootstrap capacitors C1 to C3 to a predetermined time.

In addition, in this embodiment, the charging time of the bootstrap capacitors C1 to C3 is 1.5 milliseconds, and this value is required to ensure the necessary charging amount when the capacitance of the bootstrap capacitors C1 to C3 is 1 microfarad (an example). shortest time. The necessary charging amount is not limited to full charging, and the charging time may be intentionally shortened (for example, 0.5 milliseconds, etc.).

Also, in this embodiment, the sensor 4 is used to detect the rotational frequency of the rotating part of the motor 1 , but it may be configured to detect an induced voltage generated in the motor 1 to detect the rotational frequency of the rotating part. FIG. 5 shows a modified example of the motor unit according to this embodiment. The motor unit shown in FIG. 5 further includes a detection circuit 41 in the motor unit shown in FIG. 1 . The detection circuit 41 can detect an induced voltage generated in the motor 1 . The detection circuit 41 sends the value of the detected induced voltage to the position detection unit 38 . The position detection unit 38 detects the frequency of the induced voltage from the value of the induced voltage transmitted 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 frequency of the reference voltage. When the frequency of the induced voltage is lower than the frequency of the reference voltage, the timing control unit 34 determines that the rotating portion of the motor 1 is stopped. The sequence control unit 34 uses the judgment result as a judgment criterion in the judgment step S3 in FIG. 3 .

Furthermore, the control circuit 3 may be configured to supply power to the coils connected to the respective bootstrap capacitors C1 to C3 when the charge amounts of the bootstrap capacitors C1 to C3 have not reached a predetermined value. Such a structure can be realized by having a low voltage protection circuit.

Furthermore, the motor drive circuit can be configured to include a packaged IC including the control circuit 3 and a packaged IC including the inverter circuit 2 . Also, the motor drive circuit can have a packaged IC including the inverter circuit 2 and the control circuit 3 . In addition, the motor drive circuit can be formed to include a triangular wave oscillation circuit 31, a comparator 32, a PWM signal generating unit 33, a timing control unit 34, an energization signal forming unit 35, a comparator 37, a position detecting unit 38, and a charging control unit 39. A packaged IC and a structure of a packaged IC including the inverter circuit 2 and the drive circuit 36 . That is, the configurations included in the inverter circuit 2 and the control circuit 3 can be packaged in an IC in any combination.

Furthermore, the substrate on which the motor drive circuit device 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 applicable to a motor drive circuit device and a motor unit having the motor drive circuit.

Claims (8)

1. A motor drive circuit, which has: an inverter circuit that supplies power to the coils that the motor has; and inverter control circuit, The inverter circuit has: 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 inverter control circuit has a position detection unit, a timing control unit, a bootstrap capacitor, and a charging control unit, The position detecting unit detects the rotational position of the rotating unit of the motor and outputs a rotational position signal, The timing control unit switches the upper arm side switching element and the lower arm side switching element on and off with reference to the speed command voltage input from the outside and the rotational position signal, the bootstrap capacitor stores electric power for driving the upper arm side switching element, It is characterized by: The charging control unit calculates the rotational frequency of the rotating unit of the motor with reference to the rotational position signal, and outputs a charging control signal to the timing control unit, When the speed command voltage is equal to or higher than a reference voltage and the rotation frequency is less than a reference rotation frequency, the timing control unit turns on the lower arm side switching element to charge the bootstrap capacitor for a predetermined time, After the bootstrap capacitor is charged for a predetermined time, the upper arm side switching element and the lower arm side switching element are sequentially turned on or off to start the motor, When the rotation frequency is equal to or higher than the reference rotation frequency, the timing control unit does not charge the bootstrap capacitor, and sequentially turns on or off the upper arm side switching element and the lower arm side switching element, so that The motor starts running. 2. The motor drive circuit according to claim 1, characterized in that: The timing control unit calculates a rotation frequency with reference to an induced voltage of the motor. 3. The motor drive circuit according to claim 1, characterized in that: The inverter control circuit includes a PWM signal generating part, an energization signal forming part and a drive circuit, the PWM signal generator generates a PWM signal from the speed command signal, the timing control unit adjusts the timing of the PWM signal, The energization signal forming unit generates an energization signal with reference to the PWM signal output by the timing control unit, The drive circuit switches the upper arm side switching element and the lower arm side switching element on or off using the energization signal. 4. The motor drive circuit according to claim 3, characterized in that: The drive circuit has: an upper arm side switch control circuit that switches the upper arm side switching element on or off; a lower arm side switch control circuit that switches the lower arm side switching element on or off; and the bootstrap capacitor. 5. A motor unit having: motor; inverter circuit; and inverter control circuit, The motor has: a stationary portion having a coil; and a rotating part rotatably supported by the stationary part, The inverter circuit has: 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 inverter control circuit has a position detection unit, a timing control unit, a bootstrap capacitor, and a charging control unit, The position detecting unit detects the rotational position of the rotating unit of the motor and outputs a rotational position signal, The timing control unit switches the upper arm side switching element and the lower arm side switching element on and off with reference to the speed command voltage input from the outside and the rotational position signal, the bootstrap capacitor stores electric power for driving the upper arm side switching element, It is characterized by: The charging control unit calculates the rotational frequency of the rotating unit of the motor with reference to the rotational position signal, and outputs a charging control signal to the timing control unit, When the speed command voltage is equal to or higher than a reference voltage and the rotation frequency is less than a reference rotation frequency, the timing control unit turns on the lower arm side switching element to charge the bootstrap capacitor for a predetermined time, After the bootstrap capacitor is charged for a predetermined time, the upper arm side switching element and the lower arm side switching element are sequentially turned on or off to start the motor, When the rotation frequency is equal to or higher than the reference rotation frequency, the timing control unit does not charge the bootstrap capacitor, and sequentially turns on or off the upper arm side switching element and the lower arm side switching element, so that The motor starts running. 6. The motor unit of claim 5, wherein: The motor unit further includes an induced voltage detection unit that detects an induced voltage generated at the stationary unit. 7. The motor unit of claim 5, wherein: The inverter control circuit has a PWM signal generating unit, an energization signal forming unit, and a drive circuit, the PWM signal generator generates a PWM signal from the speed command signal, the timing control unit adjusts the timing of the PWM signal, the energization signal forming unit generates an energization signal with reference to the PWM signal output from the timing control unit, The drive circuit switches the upper arm side switching element and the lower arm side switching element on or off using the energization signal. 8. The motor unit of claim 7, wherein: The drive circuit has: an upper arm side switch control circuit that switches the upper arm side switching element on or off; a lower arm side switch control circuit that switches the lower arm side switching element on or off; and the bootstrap capacitor.