JP3037969B2 - Starting method and starting device for sensorless motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sensorless motor having a permanent magnet in a rotor and a motor coil in a stator, and in particular, does not include a sensor for detecting the position of the rotor such as a Hall element. The present invention relates to startup control of a sensorless motor.

[Related Art] When a rotor having a permanent magnet passes near a motor coil, a starting force is generated in the motor coil due to a change in magnetic field.
Therefore, during the rotation of the rotor, the position of the rotor can be detected by measuring the electromotive force generated in the motor coil without providing a rotor position detecting element.

In the drive circuit of the sensorless motor, a circuit for converting the coil electromotive force generated in the motor coil into a signal is provided,
The circuit is operated using the converted signal as a rotor position signal.

However, when the motor is started, the motor is still in a stopped state, and no electromotive force is generated in the coil. Therefore,
The starting is performed in a state where the position of the rotor is unknown.
In this start-up mode, an excitation procedure for rotating the rotor in the forward direction is performed in a fixed sequence regardless of the positions of the coils of the stator and the permanent magnets of the rotor.

FIG. 2A shows a circuit of a driving section of a sensorless motor according to a conventional technique. The motor coil of the motor 21 receives the exciting current from the output transistor 23 controlled by the control circuit 22. When the motor is rotating, the electromotive force generated in the motor coil is detected by the detection circuit 24 and supplied to the control circuit 22 as a rotor position signal. Based on this position signal, the control circuit turns on / off the output transistor 23,
The rotor is rotated in a predetermined direction.

At the time of startup, the motor is not rotating, and therefore there is no output of the detection circuit 24. Therefore, the switch 27 is connected to the starting circuit 25.
To the side. The starting circuit 25 supplies a signal for exciting the motor coil in a predetermined sequence to the control circuit 22. When the rotor starts rotating, an electromotive force is generated in the motor coil, so that the switch 27 is switched to the detection circuit 24 side.

However, at the time of startup, the rotor may slightly move in the opposite direction at first, because the excitation is performed in a fixed procedure regardless of the position of the rotor. Since the entire start-up mode is a forward rotation sequence, the rotor is not accelerated until the rotor rotates reversely at a high speed. However, the required rotation speed may not reach the required rotation speed even after a predetermined time has elapsed. In order to cope with such startup failure, a control system as shown in FIG. 2 (B) is usually provided. When a start instruction is given and control is started, first, as shown in step S1, the start / brake signal S / B is changed from a high level to a low level to execute a motor start mode. Referring to the circuit of FIG. 2A, the switch 27 is connected to the starting circuit 25, and a signal for exciting the stator coil is sent to the control circuit 22 in a predetermined order. The stator coil of the motor 21 is excited based on this signal.

After executing the predetermined startup procedure, it is determined in step S2 whether or not the motor has actually started by detecting an electromotive force induced in the stator coil (detection mode).
For example, when a rotation speed of 90% or more of the predetermined rotation speed is obtained,
The launch is considered successful.

When the start is successful, it accelerates further and moves to constant speed rotation.

If the activation has failed, the S / B signal is changed from low to high to perform predetermined braking (step S3). This is called a brake mode. Thereafter, the S / B signal is changed from high to low again, and the start mode is executed again.

For example, in a hard disk drive motor of a personal computer, the drive of the hard disk is instructed at the same time as the personal computer is turned on. Normally, the start-up operation needs to be completed in about 10 seconds. Therefore, for example, a counter is prepared, and the counter is incremented when the startup fails. When the number of startup failures reaches a predetermined number of times (for example, eight times), a message such as "Press the reset button" is displayed on the display of the personal computer, and the stand is started again. Repeat the above operation.

[Problems to be Solved by the Invention] As described above, in starting the sensorless motor, the starting procedure is performed without confirming the position of the rotor. For this reason, it is inevitable that a startup failure will occur even with a small probability. For example, one startup failure occurs every 1000 times. When the start-up fails, the vehicle enters the brake mode, stops the motor, restores the motor to an initial state, and starts the operation by performing the start-up mode again. Here, the start modes repeated are independent of each other. Therefore, failure by one start mode is 1/1000
Then, even if the start mode is repeated twice, there is a 1/1000 failure probability for each time. It is desired that startup failures be reduced as much as possible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a starting method and a starting device for a sensorless motor that can significantly reduce the probability of starting failure with a simple configuration.

[Means for Solving the Problems] A starting method for a sensorless motor according to the present invention includes a first step of sequentially supplying a drive current in an order of rotating a rotor to a predetermined direction to a plurality of coils of a stator; Following the step of one step, the rotor is left unattended without supplying a drive current in an order to rotate the rotor in a predetermined direction to the plurality of coils of the stator or a braking current in an order to stop the rotor. And a second step of sequentially supplying a drive current to the plurality of coils of the stator in order to rotate the left rotor in a predetermined direction, following the pause step. To repeat the stepping process, a counter circuit can be used.

[Operation] The sensorless motor normally reaches the predetermined rotation speed in one stepping step. However, if the rotation speed has not reached the predetermined rotation speed, the sensorless motor performs the second stepping step after the idle period. A predetermined rotation speed is reached. When the startup fails in the first stepping step, the rotation speed is lower than the predetermined value, but a certain degree of rotation has occurred. Therefore, if the second stepping step is performed after pausing without performing braking, it is possible to start up almost certainly. For this reason, the probability of starting failure after the repeated stepping step can be regarded as substantially zero.

Embodiment FIGS. 1A, 1B, and 1C show a method and an apparatus for starting a sensorless motor according to an embodiment of the present invention.

FIG. 1A shows a signal waveform of a stepping pulse (reference signal) for driving a motor coil. Fig. 1 (B)
Shows a behavior in which the rotation speed of the motor is increased by the drive current based on the stepping pulse as shown in FIG. 1 (A). FIG. 1 (C) is a block diagram showing a circuit for supplying a drive current to a motor coil based on a stepping pulse as shown in FIG. 1 (A).

As shown in FIG. 1 (C), the sensorless motor
The case where the motor has three-phase, V-phase, and W-phase three-phase coils will be described.

The stepping pulse waveform shown in FIG. 1A has a U-phase, a V-phase,
This is a clock signal for setting the timing of the W-phase drive current. In the illustrated case, nine stepping pulses are set in the first stepping step, and six stepping pulses are set in the second stepping step. Since the rotor has started to rotate to some extent in the first step, the number of step pulses in the second step is set to be small.

First, a drive current is supplied based on nine step pulses, and a first step is performed.

When the motor starts rotating smoothly due to these drive currents, the rotation speed of the motor increases to a predetermined value or more as shown by a curve r1 in FIG. 1 (B). That is, the start of the motor is successful. However, at the beginning of the first step, acceleration does not take place at an appropriate time. For example, when the motor reversely rotates in the initial stage, the reverse rotation of the motor gradually decreases due to the subsequent drive current, and the motor shifts to forward rotation. The rotation speed of the motor after the completion of one step is still low as shown by the curve r2. If the obtained rotational speed does not reach the predetermined value, it is considered that the motor has failed to start. In the present embodiment, even if a predetermined rotation speed cannot be obtained by one stepping step, the second stepping step is performed without considering that the startup has failed.

In the stepping pulse waveform of FIG. 1A, six stepping pulses are shown as the second stepping step. That is, after the first stepping step, after a predetermined pause period, the second step
Step steps are performed. The second step may be equivalent to the first step, or may be shortened as shown. Even when the rotation speed obtained by the first stepping step has not reached the predetermined rotation speed, the rotation of the motor has already been started because the rotation of the motor has already been started. improves. In this way, as shown in FIG. 1 (B), even if the rotation speed of the motor has not reached the predetermined rotation speed by the first stepping step, the rotation speed of the motor is maintained at the predetermined rotation speed by the second stepping step. Can be reached.

FIG. 1C schematically shows a circuit for starting the sensorless motor as described above.

The reference signal source 1 outputs a reference signal of a predetermined frequency to a counter 3
To supply. The counter 3 counts the supplied reference signal and generates a step pulse signal. For example, as shown in FIG. 1 (A), in the first step, nine step pulse signals are generated, a rest period is set, and then the second step is started. Then, six more stepping pulses are supplied. In response to these stepping pulses, the control circuit 5
Supplies a drive current to the stator coil 7 of the motor.
Then, via a detection circuit as shown in FIG.
The mode shifts to a mode for detecting the motor rotation speed, it is confirmed that a predetermined number of rotations has been reached, and then the mode proceeds to an acceleration mode or the like. As compared with the conventional starting operation shown in FIG. 2 (B), the rotation monitoring and braking shown in steps S2 and S3 are omitted while the starting shown in step S1 is repeated. For this reason, not only the time required for activation can be shortened, but also an unnecessary braking operation can be omitted, and the activation probability can be improved.

3A and 3B show a more specific embodiment of the present invention.

FIG. 3A is a block diagram showing a starting circuit portion in the motor driving IC.

The motor drive IC 31 includes a frequency dividing circuit 32 that receives and divides the oscillation signal supplied from the oscillation circuit to generate a reference signal, and the reference signal includes two ring counters.
The pulse is supplied to a double (W) ring counter 33 that counts n pulses first and then m pulses after the idle period. The W-ring counter 33 counts the reference signal and supplies the stepping pulse signal to an energization switching circuit 34 for switching energization of each phase coil. The W-ring counter 33 also supplies a step-up pulse signal to the energization switching logic circuit 35. The energization switching logic circuit 35 performs a logical operation on how and in what order the U-phase, V-phase, and W-phase coils are switched, and supplies an output to the energization switching circuit 34. The energization switching circuit 34
A current control signal for each layer of the phase, the V phase, and the W phase is supplied to the phase switching circuit 36. The phase switching circuit 36 drives a current supply transistor to supply a current to each phase coil.

The energization switching logic circuit 35 gives a control signal on how to drive each phase coil so as to rotate the rotor forward in accordance with the start mode. After the end of the start-up mode, the electromotive force detected from each phase coil is supplied to the energization switching circuit 34,
A drive current corresponding to the rotation angle of the rotor is supplied.

FIG. 3B shows a configuration example of the double ring counter 33.

Ring counters 41 and 43 are arranged in parallel,
An output is formed upon receiving the signal. The activation signal is supplied directly to the counter 41 and to the counter 43 via a delay circuit 42. That is, the counter 43 starts operating after a time delay determined by the delay circuit 42. The outputs of both counters are taken out via OR circuit 45. In this way, for example, nine stepping pulses are supplied first, and then six stepping pulses are supplied after a rest period.

FIG. 3 (C) is a waveform diagram showing a step pulse of the reference signal and a current waveform supplied to each stator coil.
The upper part shows the waveform of the reference signal. In the case shown, nine reference signals P1 to P9 form a stepping pulse, and the current waveform supplied to the stator coil is controlled based on the stepping pulse. That is, current is sequentially supplied to the U-phase, V-phase, and W-phase coils, and the rotation of the rotor is controlled. More specifically, at the rise of the first stepping pulse P1, the U-phase and the V-phase are turned off, and the W-phase is turned on (intermediate state). The U-phase is turned on at the rise of the second stepping pulse P2. That is, U
Drive current flows through the phase and the W phase. At the rise of the third stepping pulse P3, the W phase is turned off, and only the U phase remains. The V phase is turned on by the fourth stepping pulse P4, and the U phase and the V phase are turned on. The U phase is turned off by the fifth step pulse P5, and only the V phase remains. The W phase is turned on by the sixth step pulse P6, and the V phase and the W phase are turned on. At the next seventh step pulse P7, the V phase is turned off, and only the W phase remains. This state is the same as the state of the first step pulse. Similarly, the eighth and ninth step pulses P8 and P9 are the second and third stepping pulses.
Works in the same way as the stepping pulses P2 and P3. After nine step pulses are generated, the drive current is cut off, and the mode shifts to the sleep mode. After a certain period of inactivity, the same driving is performed in the second stepping step. However, the second drive need not be the same as the first drive. For example, the number of steps, timing, and the like may be changed.

After repeating the stepping process, the control of the energization switching logic 35 is stopped, the electromotive force from the coil is measured to monitor the rotation of the rotor, and then the mode is shifted to the acceleration mode.

The case where the reference signal is counted using the W-ring counter to form the stepping pulse in the first stepping step and the stepping pulse in the second stepping step has been described. It can also be done by configuration. For example, it can be implemented using a timer.

 FIG. 4 is a partial circuit diagram of an embodiment using a timer.

The start signal is supplied to the counter circuit 48 via the OR circuit 47, and is also supplied to the timer 46. The timer 46 starts counting time in response to a start signal, and generates an output signal when a predetermined time has elapsed. This output signal passes through an OR circuit 47,
It is supplied to the counter circuit 48. The counter circuit 48 counts the FG signal a predetermined number of times.

For example, the counter circuit 48 receives 9
After generating the number of stepping pulses, after receiving the output of the timer 46 after the pause, nine stepping pulses are generated again.

Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[Effects of the Invention] As described above, according to the present invention, after the first stepping step is completed, the second stepping step is performed after a pause period, so that the first stepping step is performed. Even when the predetermined rotation speed is not reached depending on the traveling, the predetermined rotation speed can be almost surely reached by the second stepping step. For this reason, the probability of starting failure becomes almost zero.

[Brief description of the drawings]

1 (A), 1 (B) and 1 (C) are diagrams for explaining an embodiment of the present invention. FIG. 1 (A) is a waveform diagram showing a stepping pulse, and FIG. 1 (B). ) Is a graph showing the change over time of the rotation speed of the motor, FIG. 1 (C) is a circuit diagram of the starting circuit, and FIGS. 2 (A) and 2 (B) are diagrams for explaining the prior art. FIG. 2 (A) is a circuit diagram, FIG. 2 (B) is a flowchart showing a control sequence of a starting operation, and FIGS. 3 (A), (B) and (C) show specific embodiments of the present invention. FIG. 3A is a circuit diagram in a motor driving IC, FIG. 3B is a circuit diagram of a double ring counter, FIG. 3C is a signal waveform diagram, FIG. FIG. 11 is a partial circuit diagram for explaining another embodiment of the present invention. In the figure, 1 ... reference signal source 3 ... counter 5 ... control circuit 7 ... stator coil

Claims (2)

(57) [Claims] A first step of sequentially supplying a drive current in a sequence for rotating a rotor to a predetermined direction to a plurality of coils of the stator; and following the first step, the plurality of coils of the stator are successively provided. A suspension step of leaving the rotor unattended without supplying a drive current in an order to rotate the rotor in a predetermined direction or a braking current in an order to stop the rotor with respect to the coil, and following the suspension step, A second step of sequentially supplying a drive current in an order to rotate the rotor to a predetermined direction to the plurality of coils of the stator. 2. A reference signal source for generating a reference signal of a predetermined frequency, a counter for counting reference signals generated by the reference signal source and outputting a count, and a counter from the counter when a start instruction is received. The number is n
During the increase, a drive current for driving the rotor to rotate in a predetermined direction is supplied to the stator coil. Subsequently, while the count number increases by 1, the drive current for driving the rotor to rotate the rotor in the predetermined direction also rotates the rotor. A control circuit that supplies the drive current to the stator coil to rotate the left rotor again in the predetermined direction while the rotor is left without supplying the control current to stop the rotor and subsequently while the count number increases by m, Starting circuit for a sensorless motor.