JPH04109891A - Sensor-less spindle motor control circuit - Google Patents

Abstract

PURPOSE:To realize highly efficient acceleration at the time of start and reduce the rising time by a method wherein the revolution of a rotor is measured with the position of the rotor and the time for the change of the position and the timing of switching the excited phase of a motor is controlled in accordance with the position and the revolution of the rotor. CONSTITUTION:A CPU 11 outputs a motor control signal 15 for starting a motor 13 to an excited phase switching circuit 12. The excited phase is switched in accordance with the motor control signal 15 to drive the motor 13. When the motor 13 rotates, U-shape, V-shape and W-phase counter electromotive forces which have a phase difference of 120 deg. between each other are generated in motor coils 13a, 13b and 13c respectively and transmitted to a rotor position detecting circuit 14. The counter electromotive forces of the motor coils 13a, 13b and 13c are compared with a common terminal voltage Va and rotor position signals 18 of the U-phase, the V-phase and the W-shape are generated and inputted to the CPU 11. The CPU 11 generates a timing with a phase delay of 30 deg., which is an optimum phase switching timing, from the rotor position signal 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a sensorless spindle motor control circuit used in magnetic disk drives and the like.

(Prior art) A spindle motor that drives the magnetic recording medium of a magnetic disk device is equipped with a position sensor using a Hall element, and this position sensor detects the position of the rotor and controls excitation phase switching. .

On the other hand, sensorless medium spindle motors have recently been used to downsize magnetic disk drives. When using this sensorless spindle motor, the rotor position cannot be directly detected, so a rotor position signal is created by comparing the back electromotive force generated in the stator side coil with the voltage at the coil common terminal using a voltage comparator. The excitation phase switching timing is set based on this rotor position signal. In this case, since the switching timing is too early when the level of the rotor position signal changes, a certain time delay is required. This delay time is optimally a phase delay of 30°, that is, 1/12 of one period of excitation phase change. Therefore, during acceleration, it is necessary to change the optimum delay time as the rotational speed increases. Conventionally, the delay time is adjusted using a delay circuit.

(Problems to be Solved by the Invention) However, when the delay time during acceleration is adjusted by a delay circuit as in the conventional method, multi-stage switching is impossible because switching the delay time is complicated. For this reason, the delay time can only be changed in two to three stages, which poses a problem in that high acceleration efficiency cannot be obtained and it takes time to reach constant speed rotation.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sensorless spindle motor control circuit that can efficiently accelerate the motor at startup and shorten the start-up time.

[Structure of the Invention (Means for Solving the Problems) The present invention provides a sensorless spindle motor control circuit that compares the back electromotive force generated in each coil of each pole of the motor with the voltage at a common terminal of the coil. The position of the rotor is detected, the rotational speed of the rotor is measured from this rotor position and its change time, and the excitation phase switching timing applied to the motor is controlled based on the rotor position and rotational speed. be.

(Function) When the motor starts, a back electromotive voltage is generated in each pole coil on the stator side as the rotor rotates. This back electromotive voltage of each pole is compared in magnitude with the voltage of the coil common terminal,
The comparison output is taken out as a rotor position signal. Then, based on this rotor position signal, the period is measured and the rotational speed of the rotor is determined. Further, based on this rotational speed, an optimum delay time corresponding to the rotational speed is calculated, and the excitation phase is switched according to this delay time and the rotor position.

Therefore, when starting the motor, the optimum delay time is always set according to the rotational speed of the motor, and the excitation phase is switched at the optimum timing, thereby efficiently accelerating the motor.

(Example) 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 FIG. 1, 11 is a CPU, 12 is an excitation phase switching circuit, 13 is a sensorless spindle motor, and 14 is a rotor position detection circuit.

The CPU II 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 the motor control signal 15 from the CPU 11, supplies it to the motor 13, and inputs it to the rotor position detection circuit 14. The motor 13 includes U-phase, ■-phase, and W-phase stator-side motor coils 13a, 13b, and 13c and a rotor (not shown).
3a, 13b, and 13c are driven to generate a rotating magnetic field for the rotor. When the rotor is driven to rotate, the motor coils 13a, 13b.

A back electromotive voltage is generated at 13c, and this back electromotive voltage is superimposed on the motor drive signal 16 from the excitation phase switching circuit 12 and input to the rotor position detection circuit 14. Furthermore, motor coils 13a and 13b.

The voltage Va output from the common terminal 17 of the rotor 13c is input to the rotor position detection circuit 14. The rotor position detection circuit 14 detects the motor coils 13a and 13b based on the common terminal voltage Va of the motor 13.

The back electromotive force of the rotor 13c is compared and the comparison result is output to the CPU 1 as a rotor position signal 18.

The CPU II calculates the optimum delay time based on the rotor position signal 18 and creates the motor control signal 15.

Next, the operation of the above embodiment will be explained with reference to the timing chart of FIG.

FIG. 2(a) shows motor coils 13a and 13b.

13c shows the relationship between the back electromotive voltage of three phases (U phase, ■ phase, and W phase) and the common terminal voltage Va.

FIG. 2(b) shows a comparison output between the three-phase back electromotive voltage and the common terminal voltage Va output from the rotor position detection circuit 14, that is, the three-phase rotor position signal 18.

FIG. 2(c) shows the motor control signal 15 from the CPU II.
The excitation timing of the motor drive signal 16 generated by the excitation phase switching circuit 12 is shown according to the diagram. Further, in this motor drive signal 16, "+" indicates the power supply voltage, "-" indicates the ground potential, and "0" indicates the center potential.

When the power is turned on to start the motor 13, the CPU 11 outputs a motor control signal 15 for starting the motor 13 to the excitation phase switching circuit 12. The excitation phase switching circuit 12 switches the excitation phase according to the motor control signal 15 and drives the motor 13. When the motor 13 rotates, the second
As shown in Figure (a), U-phase, ■-phase, and W-phase back electromotive voltages each having a phase difference of 120' are generated and sent to the rotor position detection circuit 14 together with the voltage Va at the common terminal 17. This rotor position detection circuit 14 has a common terminal voltage Va and motor coils 13a and 13b.

13c and generates a three-phase rotor position signal 18 of U phase, ■ phase, and W phase as shown in FIG. 2(b).
Enter in PUII. The CPU II generates timing with a phase delay of 306, which is the optimum phase switching timing, from the rotor position signal 18 using the following procedure.

[I] First, for example, from the U-phase rotor position signal 18 in FIG. Optimal delay time Δ corresponding to a rotation angle of 30°
Calculate t.

[■] After calculating the optimum delay time Δt, when the signal level of the rotor position signal 18 changes, that is, as shown in FIG. 2(b)
Assuming that the U-phase rotor position signal 18 rises from a low level to a high level at time t1 in FIG.
As shown in C), the current motor excitation state is maintained for the delay time Δt. In the motor excitation state at this time, a "+" potential (power supply voltage) is applied to the ■ phase, and a "-" potential (ground level) is applied to the W phase.

[■] Then, when the delay time Δt has elapsed, the phase is switched to the next excitation phase. That is, in this case, FIG. 2(c)
As shown in , the excitation voltage of the U phase is raised from the center potential 0 to the "+" potential, and the excitation voltage of the ■ phase is lowered from the "+" potential to the center potential "0".

Hereinafter, the above [1], [n], [II
Repeat the process of [I] and obtain the rotor position signal 1 of the ■ phase and W phase.
8, an optimum delay time Δt is determined and the delay operation is performed to create an excitation switching timing that always has a phase delay of 30° in accordance with the rotational speed of the motor 13.

The motor drive signal 16 outputted from the excitation phase switching circuit 12 is supplied to the motor 13, but at this time, the back electromotive voltage of the motor coils 13a to 13c is superimposed, and as shown in FIG.
) will result in a composite waveform as shown in Note that FIG. 2(d) shows a composite waveform of the U-phase excitation voltage of the excitation phase switching circuit 12 and the back electromotive force (U-phase) of the motor coil 13a.

Therefore, where the common terminal voltage Va of the motor coils 13a to 13c intersects with the back electromotive force, the pole thereof is not excited, and therefore, only the pure back electromotive voltage that is not affected by the excitation voltage appears. As a result, a stable output can be obtained from the rotor position detection circuit 14, and control operations can be performed reliably.

In the above embodiment, the switching timing of the excitation phase of the motor 13 is entirely controlled by the CPU II. It is also possible to provide a delay circuit for the optimum delay time at startup, control the optimum delay time at startup using the CPU II, and provide a constant delay time by the delay circuit after steady rotation is reached. In this case, the CPU II only needs to control (optimum delay time) - (optimum delay time during steady rotation), and the load on the CPU 11 during steady rotation can be reduced.

[Effects of the Invention] As detailed above, according to the present invention, in a sensorless spindle motor, it is possible to always obtain the optimum excitation phase switching timing according to the rotational speed at the time of startup.
Therefore, the motor can be started efficiently, the motor start-up time can be shortened, and power consumption can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a sensorless spindle motor control circuit according to an embodiment of the present invention, and FIG. 2 is a signal waveform diagram of each part for explaining excitation phase switching operation of the embodiment. 11... CPU, 12... Excitation phase switching circuit, 13.
...Sensorless spindle motor, 14...Rotor position detection circuit, 15...Motor control signal, 16...
Motor drive signal, 17... Common terminal, 18... Rotor position signal. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] In a sensorless spindle motor control circuit, there is a position detection means that detects the rotor position by comparing the magnitude of the back electromotive force generated in each coil of each pole of the motor with the voltage of the coil common terminal, and the position detection means detects the position of the rotor. and a control means for controlling excitation phase switching timing applied to the motor based on the rotor position and rotation speed. Sensorless spindle motor control circuit.