JP2660113B2 - Sensorless spindle motor control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensorless spindle motor control circuit used for a magnetic disk drive or the like.

[0002]

2. Description of the Related Art A spindle motor for driving a magnetic recording medium or the like of a magnetic disk drive is provided with a position sensor using a Hall element, and the position of the rotor is detected by the position sensor. For this reason, the position of the rotor can be detected even at the time of starting the motor, the phase for supplying current is determined at the time of starting, and the motor can be started normally.

On the other hand, recently, a sensorless spindle motor has been used to reduce the size of a magnetic disk drive. When this sensorless spindle motor is used, the position of the rotor cannot be directly detected, so the voltage of the counter-electromotive voltage generated in the stator side coil and the voltage of the coil common terminal are compared by a voltage comparator to generate a rotor position signal. The switching timing of the excitation phase is set based on the rotor position signal.

When this sensorless spindle motor is used, a back electromotive force is not generated unless the rotor rotates, so that when the motor is started, the excitation phase is set to 1 regardless of the position of the rotor.
A driving method based on so-called forced rotation in which the rotor is rotated by rotating the rotor is generally used.

[0005]

However, in the above-mentioned conventional driving method, after performing the forced rotation driving for rotating the excitation phase once, it is determined in the following procedure whether or not the rotor has rotated correctly. Therefore, there has been a problem that the rotation state of the rotor cannot be detected at the stage of the forced rotation, and the startup control cannot be performed quickly.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a sensorless spindle motor control circuit capable of determining whether or not a rotor is rotating correctly during forced rotation driving, and enabling quick and reliable start-up control.

[0007]

SUMMARY OF THE INVENTION The present invention provides a rotor position detecting means for outputting a rotor position signal based on a back electromotive voltage generated in a motor coil and a voltage of a coil common terminal,
In a sensorless spindle motor control circuit provided with control means for determining the rotor position from the rotor position signal detected by the detection means and performing switching control of the excitation phase, when the spindle motor is forcibly rotated at startup, The rotor position detection signal output from the rotor position detection means is compared immediately after the phase switching and immediately before the switching to the next phase, and the presence or absence of rotor rotation is determined based on a change in the signal level. It is.

[0008]

When starting the motor, the back electromotive voltage is not generated at first, so that the motor is forcibly rotated at a speed at which the back electromotive voltage is generated, and then the control is shifted to the control using the back electromotive voltage. I do. At this time, the position signals of the non-excitation phase immediately before switching the excitation phase and immediately before switching to the next phase are compared, and if the position signal has changed, a back electromotive force is generated. It is determined that there is.

As described above, immediately after switching the excitation phase and immediately before switching to the next phase, the rotation state of the rotor is detected from the rotor position signal in the non-excitation phase. It is possible to determine whether or not the restart has been performed, and if it has not been started, the restart procedure can be reliably performed.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, 11 is a CPU, 12 is an excitation phase switching circuit, 13 is, for example, a three-phase sensorless spindle motor, and 14 is a rotor position detection circuit.

The CPU 11 outputs a motor control signal 15 for rotating the motor 13 to the excitation phase switching circuit 12. The excitation phase switching circuit 12 generates a motor drive signal 16 based on a motor control signal 15 from the CPU 11, supplies the motor drive signal 16 to the motor 13, and inputs the motor drive signal 16 to the rotor position detection circuit 14.

The motor 13 includes U-phase, V-phase, and W-phase stator-side motor coils 13a, 13b, 13c and a rotor (not shown), and the motor coils 13a, 13b, 13c are driven by a motor drive signal 16. Generates a rotating magnetic field for the rotor. When the rotor is driven to rotate,
A back electromotive voltage is generated in the motor coils 13a, 13b, 13c, and the back electromotive voltage is superimposed on the motor drive signal 16 from the excitation phase switching circuit 12, and the rotor position detection circuit 14
Is input to Further, the motor coils 13a, 13b, 1
The voltage Va output from the common terminal 17 of 3c is input to the rotor position detection circuit 14. This rotor position detection circuit 14 is, for example, a comparator 14 as shown in FIG.
a, 14b, and 14c.
3 based on the common terminal voltage Va of the motor coil 13
a, 13b, and 13c are compared with each other, and the comparison result is output to the CPU 11 as the rotor position signal 18. C
The PU 11 determines the rotor position from the rotor position signal 18 and creates the motor control signal 15.

Next, the operation of the above embodiment will be described. FIG.
5 is a diagram showing waveforms of an excitation voltage, a back electromotive voltage, a position detection signal, and the like in one phase of the motor 13. FIG. FIG. 3A shows an excitation waveform, and shows a drive voltage (output voltage of the excitation phase switching circuit 12) applied to one phase.

FIG. 3B shows a motor coil (13a,
In the back electromotive voltage waveforms of 13b and 13c), when the rotor is moving according to the drive voltage of (a), the back electromotive voltage having the waveform is generated in this manner. FIG. 3 (c) shows the case of 1 during steady rotation.
It is a waveform of a phase, in which the drive voltage of (a) and the back electromotive voltage of (b) are superimposed. FIG. 3D shows the rotor position detection circuit 14 based on the superimposed signal shown in FIG.
Is the rotor position signal 18 output from the above (c)
Is a comparison output between the superimposed voltage and the common terminal voltage Va. FIG. 3 (e) shows the state when the rotor rotates during the forced rotation control.
It is a superimposed voltage waveform of the phase, and the point where the back electromotive voltage slightly generated at this time crosses the center voltage by the sudden acceleration of the rotor at the time of the excitation phase switching is closer to the center of the excitation phase switching timing. Is also getting faster. FIG. 3 (f)
This is a rotor position signal 18 output from the rotor position detection circuit 14 based on the voltage of (e), and its change timing is earlier in the same manner as the voltage waveform of (e). FIG. 3 (g) is a one-phase voltage waveform when the rotor is stopped during the forced rotation control. Since there is no back electromotive voltage when the rotor is stopped, the voltage is maintained at a stable voltage at the non-excitation timing. Does not cross voltage. FIG. 3 (h)
This is a rotor position signal 18 output from the rotor position detection circuit 14 based on the voltage of (g).

The CPU 11 transmits a motor control signal 15 for driving the motor 13 to the excitation phase switching circuit 12.
Output to The excitation phase switching circuit 12 outputs the motor control signal 1
The excitation phase is switched in accordance with 5 and the motor 13 is driven. In other words, the excitation phase switching circuit 12 applies the excitation waveform drive signals shown in FIG. 3A to the three-phase motor coils 13a to 13c with a phase difference of 120 °.

When the motor 13 rotates, the motor coil 1
The counter electromotive voltages shown in FIG. 3 (b) are generated in 3a, 13b, 13c with a phase difference of 120 °, respectively, and are superimposed on the drive voltage of (a) and input to the rotor position detection circuit 14.
The composite waveform of the driving voltage and the back electromotive voltage at this time is shown in FIG.
The result is as shown in FIG. Also, the rotor position detection circuit 1
4 is a voltage Va generated at the common terminal 17 of the motor 13.
Is entered. The rotor position detection circuit 14 compares the common terminal voltage Va with the back electromotive voltage of the motor coils 13a, 13b, 13c, generates a rotor position signal 18 as shown in FIG. . At the time of the control of the steady rotation, the CPU 11 changes the excitation phase from the rotor position signal 18 at a timing of 30 ° delay which is an optimal phase switching timing, and drives the motor 13 to rotate.

However, when the motor 13 is started, the above-described control cannot be performed because the back electromotive voltage is not generated. Therefore, after the forced rotation is performed at such a speed as to generate the back electromotive voltage, the control is shifted to the control using the back electromotive voltage. Therefore, if the back electromotive voltage generated during forced rotation is detected,
It can be seen that the rotor is rotating. When detecting this back electromotive voltage, according to the present invention, as shown in FIGS. 3 (e) and 3 (f), immediately after the excitation phase is switched (t1) and immediately before switching to the next phase (t2), the non-excitation is performed. The phase position signals are compared, and if they have changed, it is determined that the rotor has rotated and a back electromotive voltage has been generated. That is, when the rotor is not rotating, since no back electromotive voltage is generated, the phase voltage at the time of non-excitation stays at a stable voltage as shown in FIG.
Does not cross the center voltage. In addition, even when the rotor is not rotating, the stable voltage in each phase at the time of non-excitation is not as shown in FIG.
If the center voltage is different from the center voltage as shown by the broken line A in (g), the rotor position signal may be switched in the middle of the non-excitation time, for example, as indicated by α when the excitation signal falls, At the next rise, the rotor position signal is not switched as indicated by β. Therefore, as shown in FIG. 3, by confirming whether or not the rotor position signal has changed at both t1, t2 at the time of the fall of the excitation signal and at t3, t4 at the time of the rise, the rotation of the rotor is determined. Detection can be performed more reliably.

When the motor 13 is forcibly rotated, the excitation phase is slowly changed without confirming the position of the rotor. Therefore, the rotor is greatly accelerated at the moment when the excitation phase is switched, and the timing for switching to the next phase is required. In this case, the motor is decelerated without switching the excitation phase. Therefore, the change point of the position signal is earlier than the center of the non-excitation time, which is the original change point. Therefore, the detection timing t1
, T2 (t3, t4) are too long from the excitation phase switching point, the signal after the change is captured, and if too short, the signal takes in an unstable state. For this reason, the detection timings t1 and t2 are set to １ ／ of the one-phase non-excitation time when the motor 13 is at the maximum rotation speed. This timing is the timing of ta as shown by the waveform in FIG. In this position, the output is stable, and even if the rotor rotates quickly, a signal can be captured before the position signal is switched. For example, a motor that makes one rotation in six cycles is 6,000 rpm
When rotating to m, 1 / (6000 [rpm] ÷ 60 [sec] × 6 [phase]
× 6 [period] × 4) = 69 [μs]. That is, the positions of t1, t2 (t3, t4) may be set at intervals of 69 [μs] from the excitation phase switching point.

FIG. 4 shows a start control operation at the time of the forced rotation. When starting, the CPU 11 first excites an arbitrary phase, for example, a U-phase motor coil 13a with the drive voltage shown in FIG. 3A (step S1).
After the fall of the drive voltage, the control waits until a predetermined time ta elapses, that is, until the detection timing of t1 is reached (step S2). Then, at time t1, the level of the rotor position signal 18 output from the rotor position detection circuit 14 is checked (step S3), and thereafter, it waits until the detection timing of t2 comes (step S4).
That is, in this step S4, "phase non-excitation time-
Wait for "2ta time". Then, at the detection timing of t2, the CPU 11 re-executes the rotor position detection circuit 14 again.
The level of the rotor position signal 18 is checked (step S5) and compared with the level of the rotor position signal 18 checked in the previous step S3 (step S6) to determine whether or not the position signal has changed (step S6). S7).

If the position signal has changed, it is determined whether or not the position signal has changed for the second time, that is, whether or not the rise and fall of the excitation signal have changed. If it is the first time, the process proceeds to step S9 and the next phase motor coil, in this case, the V phase motor coil 13b
To excite. Further, even if it is determined in step S7 that the position signal has not changed, the processing in step S9 is executed.

Next, after the elapse of the phase excitation time, the motor coil 13c of the next phase, that is, the W phase, is excited (step S10). Further, after the elapse of the phase excitation time, step S1
And the above-described activation processing is executed again. And C
When the PU 11 detects in step S8 that the position signal has changed at both the rise and fall of the excitation signal, the PU 11 determines that the motor 13 has correctly rotated, terminates the startup processing, and proceeds to the next acceleration sequence. enter.

As described above, during the process of the forced rotation, it can be detected whether or not the motor 13 has been started correctly.

[0023]

As described above in detail, according to the present invention, the rotor position signals in the non-excitation phase are compared immediately after switching the excitation phase and immediately before switching to the next phase. When a change is detected in the position signal, it is determined that the rotor is rotating.Therefore, without waiting for the next procedure of the forced rotation, whether or not the motor is started during the process of the forced rotation is determined. It can be determined, and if it has not been started, the restart procedure can be performed reliably.
Therefore, the sensorless spindle motor can be started quickly,
And it can be performed reliably.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a sensorless spindle motor control circuit according to one embodiment of the present invention.

FIG. 2 is a block diagram showing details of a rotor position detection circuit in the embodiment.

FIG. 3 is a signal waveform diagram of each section for explaining an excitation phase switching operation of the embodiment.

FIG. 4 is a flowchart showing a control operation at the time of startup in the embodiment.

[Explanation of symbols]

11 CPU, 12 excitation phase switching circuit, 13 sensorless spindle motor, 14 rotor position detection circuit, 1
5 ... motor control signal, 16 ... motor drive signal, 17 ... common terminal, 18 ... rotor position signal.

Claims (1)

(57) [Claims] 1. A sensorless spindle motor, excitation phase switching means for switching an excitation phase of the spindle motor, rotor position detection means for generating a rotor position signal based on a back electromotive voltage generated by the spindle motor, and Control means for determining the rotor position from the rotor position signal detected by the means, and controlling the excitation phase switching means;
Forcible rotation driving means for forcibly driving the motor through the excitation phase switching means at the time of starting the spindle motor,
At the time of forced rotation driving of the motor by this driving means, the rotor position detection signal output from the rotor position detecting means is compared between immediately after the phase switching and immediately before the switching to the next phase. A sensorless spindle motor control circuit, comprising: