JP2008220087A - Device and method for driving motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely start the rotation of a three-phase brushless motor in a short time. <P>SOLUTION: In the rotation stop state of a rotor, a transistor Tr11 is energized, and a common terminal C is kept at constant voltage, and in this condition, the same voltage for current detection is applied in order to each of coils L1-L3. In a register 16, the peak value of the current flowing each time the voltage for current detection is applied to each of the coils L1-L3 is stored, and a phase judging circuit 17 judges the position of a rotor, based on the phase when the maximum value of those peak values appears. At this time, the voltage for current detection is applied to a motor coil for one phase, so the time until the current reaches its peak value is shortened. A drive control circuit 13 starts controlling a power output circuit 11 so as to supply the coils L1-L3 with power in specified order so that the rotor may turn together, based on the judgement results by the phase judging circuit 17. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor driving apparatus and method for driving a three-phase brushless motor, and more particularly to a motor driving apparatus and method capable of optimizing the operation at the start of rotation of a rotor.

  There is a so-called sensorless drive system that does not use a rotor position detection sensor such as a Hall element in the motor drive circuit. As such a motor drive circuit, a counter electromotive voltage generated in a coil when the rotor rotates. A method is known in which the position of the rotor is detected by detecting the current and the coil is appropriately energized according to the position (see, for example, Patent Document 1).

However, in the motor drive circuit of such a system, the back electromotive voltage is not generated at the time of start-up, so that the rotor position cannot be detected. As a countermeasure at the time of starting, there is a method called inductive sensing, in which a voltage is applied between coil phases, and the phase of the rotor is detected by comparing peak amplitude values of currents flowing at that time (for example, Patent Document 2).
Japanese Patent Laid-Open No. 10-136691 (paragraph numbers [0002] to [0003], FIG. 1) Japanese Patent No. 2547778 (page 6, FIG. 4)

  However, in this inductive sensing, when the inductance of the coil increases, it becomes difficult for current to flow through the coil, and it takes a long time to detect the phase. As a result, problems such as an audible switching noise occurring before the rotor phase is detected or a phase cannot be detected correctly due to the rotor moving.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a motor driving apparatus and method capable of reliably starting rotation of a motor in a short time.

  In the present invention, in order to solve the above-mentioned problem, in a motor driving apparatus for driving a three-phase brushless motor, a feeding circuit that selectively feeds current to motor coils of each phase, and a state where rotation of the rotor is stopped Only when the common terminal to which one end of the motor coil of each phase is connected is held at a constant voltage, and when the switch circuit is turned on and the common terminal is at the constant voltage, A voltage application circuit that sequentially applies the same current detection voltage to the motor coil of each of the motor coils, and a peak value of a current that flows each time the current detection voltage is applied to the motor coil of each phase, The rotor position discriminating circuit at start-up that discriminates the position of the rotor on the basis of the phase when the maximum value appears, and the power feeding circuit are controlled so that the rotor rotates. And a power supply control circuit for starting power supply in the predetermined order based on a determination result of the starting rotor position determination circuit. The

  In such a motor drive device, under the control of the power supply control circuit, the rotor rotates by supplying current in a predetermined order from the power supply circuit of the motor coil of each phase so that the rotor is rotated. In addition, when the rotation of the rotor is stopped, the switch circuit is turned on, and the common terminal to which one end of each phase of the motor coil is connected is held at a constant voltage. The same current detection voltage is sequentially applied to the motor coils. Then, the starting rotor position discriminating circuit detects the peak value of the current that flows each time the current detection voltage is applied to the motor coil of each phase, and based on the phase when the maximum value of those peak values appears. The position of the rotor is determined. The power supply control circuit starts power supply in a predetermined order from the power supply circuit to the motor coils of each phase based on the determination result by the rotor position determination circuit at startup.

  According to the motor drive device of the present invention, in a state where the rotation of the rotor is stopped, the common terminal is held at a constant voltage, and the same current detection voltage is sequentially applied to the motor coils of each phase. The position of the rotor is determined based on the peak value of the current flowing through the motor coil of each phase. For this reason, the impedance of the coil to which the voltage for current detection is applied is lowered, and the time until the magnitude of the current flowing through the coil reaches the peak value is shortened. Therefore, the time until the rotor position is determined can be shortened, and the rotation of the rotor can be started in a short time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of a motor drive circuit according to the first embodiment.
A motor drive circuit 1 shown in FIG. 1 is a circuit for driving a three-phase brushless DC motor, and includes a power output circuit 11, a back electromotive voltage detection circuit 12, a drive control circuit 13, a startup sequence generation circuit 14, and a current detection circuit. 15, a register 16, a phase discrimination circuit 17, and a transistor Tr11.

  The power output circuit 11 is a circuit for causing a current to flow to the coils L1 to L3 constituting the stator (stator). Here, the pnp transistors Tr1 to Tr3, the npn transistors Tr4 to Tr6, and It is constituted by. A power supply voltage VCC is applied to the emitters of the transistors Tr1 to Tr3, and the emitters of the transistors Tr4 to Tr6 are grounded via a resistor R1 described later. The collectors of the transistors Tr1 to Tr3 and the transistors Tr4 to Tr6 are connected to each other, and one ends of the coils L1 to L3 are connected to the connection points U to W, respectively. The other ends of the coils L1 to L3 are connected by a common terminal C.

  The back electromotive voltage detection circuit 12 detects the voltage between the connection points U to W and the common terminal C, and compares this voltage with a predetermined voltage, thereby the polarity of the back electromotive voltage generated in the coils L1 to L3. Is detected.

  The drive control circuit 13 outputs a switching control signal to the base terminals of the transistors Tr1 to Tr6 of the power output circuit 11 at a timing at which the rotor is rotated. In a normal state, the drive control circuit 13 generates a switching timing based on the detection result of the back electromotive voltage detection circuit 12, but operates at the time of startup in accordance with a processing sequence generated by the startup sequence generation circuit 14, so-called inductive. The position (phase) of the rotor is determined by sensing. The drive control circuit 13 also outputs a control signal for turning on / off the transistor Tr11, and turns on the transistor Tr11 only at the time of activation, as will be described later.

  The startup sequence generation circuit 14, the current detection circuit 15, the register 16, and the phase determination circuit 17 constitute a startup control circuit that operates only at the start of motor rotation. The startup sequence generation circuit 14 generates a predetermined processing sequence at the start of rotation of the motor and controls the drive control circuit 13.

  The current detection circuit 15 is a circuit that detects a current flowing through each phase (here, coils L1 to L3) of the motor coil at the time of start-up. Here, the current detection circuit 15 detects a current from a voltage across the resistor R1 for current detection. . The current detection position is not limited to this method. For example, the current flowing from the collectors of the transistors Tr4 to Tr6 to the emitter may be detected.

  The register 16 stores the peak value of the current detection value by the current detection circuit 15. The phase determination circuit 17 determines the position (phase) of the rotor based on the value stored in the register 16 and supplies the determination result to the drive control circuit 13.

  The emitter of the transistor Tr11 is connected to the input terminal of the power supply voltage VCC, and the collector is connected to the common terminal C of the coils L1 to L3. The transistor Tr11 selectively connects the common terminal C to the input terminal of the power supply voltage VCC according to a control signal supplied from the drive control circuit 13 to the base.

  The motor drive circuit 1 having the above configuration is a sensorless drive circuit that does not have a rotor position detection element such as a hall element. During normal operation, the motor drive circuit 1 detects a counter electromotive voltage generated in the coils L1 to L3, thereby detecting the rotor. Is determined, and the energization timing of each of the coils L1 to L3 is determined. However, since no back electromotive force is generated in the coils L1 to L3 when the motor is stopped, a voltage is applied to the coils L1 to L3 when the motor starts rotating, and the position of the rotor is determined based on the peak value of the current flowing at that time. An operation called inductive sensing is performed.

  In the conventional inductive sensing, by switching the transistors Tr1 to Tr6 of the power output circuit 11, two-phase coils, that is, between the coils L1 and L2, between the coils L2 and L3, and between the coils L3 and L1 The position of the rotor was detected by sequentially applying the same voltage between them and detecting the peak value of the current (amplitude) when each voltage was applied. In other words, depending on the position of the rotor at this time, the peak value of the current when one of the voltages is applied is larger than the other peak value, so the position of the rotor is determined from the phase of the motor where the peak value is maximum. it can. However, this method has a problem in that since current flows through the two coils connected in series, the inductance increases and the rise of the current flowing through the coil is delayed.

  On the other hand, in the present embodiment, at the start of rotation of the motor, the transistors Tr1 to Tr3 in the power output circuit 11 are turned off and the transistor Tr11 is turned on so that the common terminal C and the input terminal of the power supply voltage VCC are turned on. And connect. In this state, the transistors Tr4 to Tr6 are sequentially turned on one by one in order to apply a constant voltage (that is, the power supply voltage VCC) to the coils L1 to L3 one by one, and the peak value of the current flowing each time. Is detected. At this time, the peak value of the current flowing through one of the coils L1 to L3 is larger than the other peak values, and from this, the position of the rotor can be determined.

  Here, in the conventional method in which a current is passed through coils for two phases, it can be considered that a coil for two phases is wound around a continuous magnetic core and a current is passed through such a coil. Since the inductance of the coil is proportional to the square of the number of turns, the inductance of the coil for two phases is four times that for one phase. As a result, the current response to voltage application is theoretically four times slower when a voltage is applied to a coil for two phases than for a single phase. However, even if a current is passed through a coil for two phases, the number of turns is twice that when a current is passed through a coil for one phase, so the magnetomotive force when the same current flows is for one phase. It is only twice as much.

  For these reasons, the amount of change in magnetic flux density that induces a change in magnetic permeability of the magnetic core (iron core) that causes the difference in the peak value of the current described above is the coil for one phase as in this embodiment. When the voltage is applied to the current, the theoretically doubles in the same time as in the case of the conventional two-phase, which means that the time required for the current rising is twice as fast. Therefore, the time until the peak value of the current is detected can be theoretically reduced to ½.

Here, FIG. 2 and FIG. 3 are graphs showing measurement examples of current rising curves when a voltage is applied to a coil for two phases and a coil for one phase, respectively.
2 and 3 show the current detection values when the same voltage (2 V) is applied to each of the two-phase iron core coils and the one-phase iron core coils. The two-phase iron core coil used in this measurement has a resistance of 6.5Ω and an inductance of about 0.8 mH.

  2 and 3, timings T1 and T3 are voltage application start timings, and timings T2 and T4 are timings when the current detection value reaches 90% of the peak value. In this measurement example, the time until the current of 90% of the peak value flows is shortened by about 62% when the voltage is applied to the coil for one phase, compared with the case for two phases.

FIG. 4 is a flowchart showing a flow of control processing in the motor drive circuit at the start of rotation of the motor.
[Step S11] The operation of the activation sequence generation circuit 14 is started, and the drive control circuit 13 first turns on the transistor Tr11 connected to the common terminal C under the control of the activation sequence generation circuit 14. At this time, the data stored in the register 16 is cleared.

  [Step S12] The drive control circuit 13 turns off the transistors Tr1 to Tr3 of the power output circuit 11 according to the timing controlled by the activation sequence generation circuit 14, and sequentially turns on the transistors Tr4 to Tr6 in this state. Further, during the period in which the transistors Tr4 to Tr6 are turned on, the peak value of the current detection value by the current detection circuit 15 is stored in the register 16.

  [Step S13] The phase discrimination circuit 17 reads the peak value of the current from the register 16, discriminates the position (phase) of the rotor based on the generation timing of the maximum value of those peak values, and notifies the drive control circuit 13 of it. To do.

[Step S14] The drive control circuit 13 turns off the transistor Tr11.
[Step S15] Based on the phase notified from the phase discrimination circuit 17, the drive control circuit 13 discriminates the transistors in the power output circuit 11 to be turned on first in order to rotate the rotor. The power is turned on to start power supply to the corresponding coils (two of the coils L1 to L3). Thereby, rotation of a rotor is started. Further, the drive control circuit 13 may sequentially switch the energization timings of the coils L1 to L3 for a predetermined period thereafter in accordance with the timing instructed from the activation sequence generation circuit 14.

  [Step S16] As the rotor starts rotating, the counter electromotive voltage detection circuit 12 starts detecting the counter electromotive voltage generated in the coils L1 to L3. The drive control circuit 13 ends the operation under the control of the startup sequence generation circuit 14 and starts feeding control to the coils L1 to L3 based on the detection result of the back electromotive voltage. Specifically, the drive control circuit 13 performs a counting operation based on the zero cross timing of the voltages of the coils L1 to L3 based on the detection result of the back electromotive voltage, and sets a timing that is a reference of the energization timing of each phase. Generate. Then, on / off operation of each of the transistors Tr1 to Tr6 in the power output circuit 11 is switched according to the generated timing, and a current is selectively applied to the coils L1 to L3 so that the rotor rotates in a certain direction. Shed.

FIG. 5 is a diagram illustrating an example of the on / off timing of a transistor in inductive sensing.
In FIG. 5, a signal COM_tr indicates a control signal for controlling on / off of the transistor Tr11 connected to the common terminal C, and signals U_tr, V_tr, W_tr are switching control for controlling the transistors Tr4, Tr5, Tr6, respectively. Signals are shown. These signals are all output from the drive control circuit 13.

  After the transistor Tr11 is turned on at timing T11 (corresponding to step S11 in FIG. 4), the signals U_tr, V_tr, and W_tr are sequentially set to the high level, whereby the transistors Tr4 to Tr6 are sequentially turned on (in step S12). Correspondence). While the signals U_tr, V_tr, and W_tr are at a high level, the peak values of the current detection values in the corresponding coils L1 to L3 are stored in the register 16, and then at timing T12 (corresponding to step S14). The transistor Tr11 is turned off.

  As described above, in this embodiment, since the voltage is individually applied to the coils of each phase (that is, each of the coils L1 to L3), the response of rising of the current with respect to the voltage application is improved, and in a shorter time. The peak value of the current can be detected. Therefore, even if the pulse widths of the signals U_tr, V_tr, and W_tr at the time of inductive sensing are reduced, the current peak value can be accurately detected, and the period of the timings T11 to T12 in FIG. 5 can be shortened. .

  Therefore, the time required to detect the position of the rotor is shortened, and the rotation of the motor can be started in a short time. In particular, even a motor having a coil with a large inductance can detect the position of the rotor in a short time with a driving voltage lower than that of the conventional method, and can start rotating, thereby reducing its power consumption. .

  Even when the coil inductance is large, the pulse width of the applied voltage for rotor position detection can be shortened, so the possibility that the rotor will move during the period until position detection is reduced, and the motor starts more reliably. Can be made. Furthermore, the possibility of audible switching noise occurring during that period is reduced, and the user's comfort can be improved.

  In the above embodiment, a voltage is applied to each of the coils L1 to L3 once. However, depending on the specifications of the motor, such a processing sequence is repeated a plurality of times so that the peak value of the current can be more accurately determined. You may make it detect to.

  In the first embodiment, the common terminal C is connected to the input terminal of the power supply voltage VCC by turning on the transistor Tr11 during inductive sensing. However, in inductive sensing, It is only necessary to make the voltage of the common terminal C constant, and this voltage is not limited to the power supply voltage VCC. Further, the common terminal C may be switched to a plurality of voltages, and the current flowing through the coils L1 to L3 in each voltage state may be detected to improve the phase discrimination accuracy.

  FIG. 6 is a diagram illustrating a configuration of a motor drive circuit according to the second embodiment. In FIG. 6, circuits corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  In the motor drive circuit 2 shown in FIG. 6, a pnp transistor Tr12 and an npn transistor Tr13 are provided as circuits for switching the common terminal C to a constant voltage. The emitter of the transistor Tr12 is connected to the input terminal of the power supply voltage VCC via the resistor R2, and the collector is connected to the common terminal C. The emitter of the transistor Tr13 is grounded via the resistor R3, and the collector is connected to the common terminal C. The on / off operations of these transistors Tr12 and Tr13 are both controlled by a control signal from the drive control circuit 13.

  In addition to the current detection circuit 15a corresponding to the current detection circuit 15 of FIG. 1, the motor drive circuit 2 includes a current detection circuit 15b that detects the current flowing through the coils L1 to L3 based on the voltage across the resistor R3. Is provided. The detection results of these current detection circuits 15a and 15b are stored in the register 16.

  In the motor drive circuit 2 having this configuration, the common terminal C can be switched to two types of voltages. Therefore, the current flowing through the coils L1 to L3 in each state is detected, the peak value of the current is accurately detected, and the position of the rotor can be accurately determined based on the detection result.

  Specifically, first, the transistor Tr12 is turned on and the transistor Tr13 is turned off, whereby the common terminal C becomes a constant voltage obtained by subtracting the voltage drop due to the resistor R2 from the power supply voltage VCC. In this state, the transistors Tr1 to Tr3 are turned off, and the transistors Tr4 to Tr6 are sequentially turned on exclusively, whereby a constant voltage is applied to each of the coils L1 to L3. The register 16 stores the peak value of the current detected by the current detection circuit 15a.

  Next, by turning off the transistor Tr12 and turning on the transistor Tr13, the common terminal C is grounded via the resistor R3. In this state, the transistors Tr4 to Tr6 are turned off, and the transistors Tr1 to Tr3 are sequentially turned on exclusively, whereby a constant voltage different from the above is applied to each of the coils L1 to L3. The register 16 stores the peak value of the current detected by the current detection circuit 15b.

  The phase discriminating circuit 17 discriminates the position of the rotor based on the current peak values detected in the above two states. For example, the position of the rotor is determined based on the detection result with the larger difference between the maximum peak value for each coil and the other peak value. Thereby, the position of the rotor can be determined more accurately. Note that after the rotor position is determined, both the transistors Tr12 and Tr13 may be turned off, and the processing after step S15 in FIG. 4 may be executed.

  In addition to changing the voltage of the common terminal C as described above, for example, depending on the specifications of the motor to be connected, only appropriate ones of the transistors Tr13 and Tr14 are turned on, and only in one of the two states. The position of the rotor may be detected, thereby increasing the versatility of the circuit.

  In each of the embodiments described above, the transistors Tr11 to Tr13 are used as the switching circuit for temporarily setting the common terminal C to a constant voltage. However, the present invention is not limited to this, and other switch circuits such as a relay are used. May be used.

It is a figure which shows the structure of the motor drive circuit which concerns on 1st Embodiment. It is a graph which shows the example of a measurement of the rise curve of an electric current when a voltage is applied to the coil for two phases. It is a graph which shows the example of a measurement of the rise curve of an electric current when a voltage is applied to the coil for 1 phase. It is a flowchart which shows the flow of the control processing in a motor drive circuit at the time of the rotation start of a motor. It is a figure which shows the example of the on / off timing of the transistor in inductive sensing. It is a figure which shows the structure of the motor drive circuit which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,2 ... Motor drive circuit, 11 ... Power output circuit, 12 ... Back electromotive voltage detection circuit, 13 ... Drive control circuit, 14 ... Start-up sequence generation circuit, 15, 15a, 15b ... Current detection circuit , 16... Register, 17... Phase discrimination circuit, C... Common terminal, L1 to L3 .. coil, R1 to R3... Resistor, Tr1 to Tr6, Tr11 to Tr13. ... Connection point, VCC ... Power supply voltage

Claims (8)

In a motor drive device for driving a three-phase brushless motor,
A power feeding circuit that selectively feeds current to the motor coils of each phase;
Only when the rotation of the rotor is stopped, a switch circuit that holds the common terminal connected to one end of the motor coil of each phase at a constant voltage;
A voltage application circuit that sequentially applies the same current detection voltage to the motor coils of each phase when the switch circuit is turned on and the common terminal is set to the constant voltage;
Start that detects the peak value of the current that flows each time the current detection voltage is applied to the motor coil of each phase, and determines the position of the rotor based on the phase when the maximum value of the peak value appears Rotor position discrimination circuit,
The power feeding circuit is controlled so that the motor coils of the respective phases are fed in a predetermined order so that the rotor is rotated. A power supply control circuit for starting
A motor drive device comprising:   When power supply in the predetermined order is started for the motor coils of each phase by the control of the power supply control circuit, a back electromotive voltage generated in the motor coils of each phase is detected and the back electromotive force is detected. 2. The motor drive device according to claim 1, further comprising a normal-time rotor position determination circuit that determines the position of the rotor based on a voltage detection result and notifies the power supply control circuit of the determination result.   The voltage application circuit controls the power supply circuit so that one end of the motor coil of each phase is electrically connected to a power supply side terminal or a ground side terminal of the power supply circuit when the common terminal is set to the constant voltage. The motor driving device according to claim 1, wherein the current detection voltage is sequentially applied to the motor coils of the respective phases. The switch circuit holds the common terminal at the constant voltage by conducting the power supply side terminal of the power supply circuit and the common terminal,
The voltage application circuit controls the power supply circuit so that one end of the motor coil of each phase is electrically connected to the ground side terminal of the power supply circuit when the common terminal is electrically connected to the power supply side terminal. , Sequentially applying the current detection voltage to the motor coils of each phase;
The motor driving apparatus according to claim 1. The switch circuit holds the common terminal at the constant voltage by conducting the ground side terminal of the power supply circuit and the common terminal,
The voltage application circuit controls the power supply circuit so that one end of the motor coil of each phase is electrically connected to the power supply side terminal of the power supply circuit when the common terminal is electrically connected to the ground side terminal. , Sequentially applying the current detection voltage to the motor coils of each phase;
The motor driving apparatus according to claim 1. A plurality of the switch circuits for holding a common terminal connected to one end of the motor coil of each phase at a plurality of the constant voltages;
The current detection voltage corresponding to each of the switch circuits can be applied to the motor coil of each phase, and when any one of the switch circuits is turned on, the current detection voltage corresponding to the switch circuit The voltage application circuit sequentially applying to the motor coil of each phase;
The motor drive device according to claim 1, wherein The voltage application circuit sequentially conducts the plurality of switch circuits, and each time, the corresponding current detection voltage is sequentially applied to the motor coils of the respective phases,
The startup rotor position determination circuit detects the peak value when each of the switch circuits is conductive, and determines the position of the rotor based on the detection results.
The motor driving device according to claim 6. In a motor driving method for driving a three-phase brushless motor,
The control circuit conducts the switch circuit in a state where the rotation of the rotor is stopped, and maintains the common terminal to which one end of the motor coil of each phase is connected at a constant voltage,
The control circuit causes the voltage application circuit to apply the same current detection voltage to the motor coils of each phase in a state where the common terminal is held at the constant voltage,
The starting rotor position determination circuit detects the peak value of the current that flows each time the current detection voltage is applied to the motor coil of each phase, and based on the phase when the maximum value of the peak value appears. To determine the position of the rotor,
The control circuit starts an operation of controlling the power feeding circuit so that the motor coils of the respective phases are fed in a predetermined order so that the rotor is rotated based on the determination result by the rotor position determination circuit at the time of starting. ,
The motor drive method characterized by the above-mentioned.

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