JP4890796B2 - Motor drive circuit and disk device using the same - Google Patents

Description

  The present invention relates to a technique for controlling rotation of a rotor, and more particularly to a motor drive circuit that controls rotation of a motor including a stator having a plurality of coils and a magnetic rotor.

  In an electronic device using a disk-type medium such as a portable CD (Compact Disc) device or a DVD (Digital Versatile Disc), a brushless DC motor is used to rotate the disk. Brushless direct current (DC) motors generally include a rotor with a permanent magnet and a stator with a plurality of star-connected coils of a phase, and the coil is excited by controlling the current supplied to the coil. The rotor is driven by rotating relative to the stator. In order to detect the rotational position of the rotor, the brushless DC motor generally includes a sensor such as a Hall element or an optical encoder, and switches the current supplied to the coil of each phase according to the position detected by the sensor. And apply an appropriate torque to the rotor.

  In order to further reduce the size of the motor, a sensorless motor that detects the rotational position of the rotor without using a sensor such as a Hall element has also been proposed (for example, see Patent Document 1). The sensorless motor obtains position information by detecting the induced voltage generated in the coil, for example, by measuring the potential of the midpoint wiring of the motor.

In Patent Document 2, as described as a problem to be solved by the invention, in such a sensorless motor, spike-like noise is generated in the counter electromotive voltage generated in each coil due to counter electromotive noise or the like, and rotation of the motor is performed. There is a problem that becomes unstable.
JP-A-3-207250 Japanese Patent Laid-Open No. 10-243865

  In order to reduce the influence of the back electromotive noise, the applicant of the above-mentioned Patent Document 2 masks signal level transitions caused by the back electromotive noise during a predetermined period in which the back electromotive noise is generated. Proposed a technique to reduce the impact on motor drive. In the technique proposed in Patent Document 2, since the period for masking back electromotive noise is fixed to a predetermined value, there is room for improvement in the stability of the motor in an application in which the rotational speed of the motor changes greatly. .

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a motor drive circuit capable of removing noise and stabilizing the rotation even when the rotation speed of the motor changes.

  One embodiment of the present invention relates to a motor drive circuit that drives a multiphase motor by supplying a drive current. The motor drive circuit compares a back electromotive voltage generated in each phase coil of a multiphase motor with a multiphase midpoint voltage, and generates a first rectangular wave signal for each phase. A masking process for removing the noise component of the first rectangular wave signal of each phase output from the occurrence detection comparator and outputting as a second rectangular wave signal of each phase, and a second rectangular wave signal of each phase Based on the output circuit that supplies the drive current to the coils of each phase of the multiphase motor and the frequency generation that detects the edge of the second rectangular wave signal of each phase and generates a frequency generation signal that switches the level for each detected edge A circuit, and a mask signal generation circuit that generates a mask signal having a predetermined level for a period obtained by multiplying the pulse width of the frequency generation signal by a predetermined coefficient after the level transition of the frequency generation signal. The mask circuit performs a masking process for invalidating the level fluctuation of the first rectangular wave signal during a period in which the mask signal is at a predetermined level.

  According to this aspect, the period for invalidating the fluctuation of the first rectangular wave signal defined by the mask signal changes according to the pulse width of the frequency generation signal, that is, the rotational speed of the motor. Even when the number fluctuates, the back electromotive noise and the like can be suitably removed from the first rectangular wave signal, and the motor can be rotated stably.

  The mask signal generation circuit is reset at each level transition of the frequency generation signal, and starts counting, a register that holds a count value at the time of reset counted by the counter, and a count value held in the register A mask width setting unit that outputs a mask signal having a pulse width corresponding to a numerical value obtained by multiplying by a coefficient.

  The register may hold the count value of the previous frequency generation signal with respect to the mask signal to be output. In this case, since the rotation speed of the immediately preceding motor is reflected in the mask time, even when the rotation speed of the motor is rapidly changed, the mask can be driven stably.

The mask signal generation circuit may output a mask signal having a predetermined fixed value as a pulse width at the start of driving of the multiphase motor.
At the start of driving the motor, the frequency signal can be fixed by fixing the pulse width of the mask signal.

  The motor drive circuit may be integrated on a single semiconductor substrate. The integration here includes a case where all of the circuit components are formed on a semiconductor substrate and a case where the main components of the circuit are integrally integrated. Part of the resistors, capacitors, and the like may be provided outside the semiconductor substrate.

  Another embodiment of the present invention is an electronic device. This electronic apparatus includes a spindle motor that rotates a disk and the above-described motor drive circuit that drives the spindle motor.

  According to this aspect, it is possible to suppress the influence of back electromotive noise and stabilize the rotational speed of the disk.

  ADVANTAGE OF THE INVENTION According to this invention, even if the rotation speed of a motor changes, the motor drive circuit which can remove a noise and can stabilize rotation can be provided.

  FIG. 1 is a circuit diagram showing a configuration of a motor drive circuit 100 according to the embodiment. The motor drive circuit 100 supplies a drive current to a sensorless brushless DC motor 50 (hereinafter simply referred to as “motor 50”) to control rotation. The motor 50 is a three-phase DC motor including U-phase, V-phase, and W-phase coils 50a to 50c.

  The motor drive circuit 100 includes a back electromotive force detection comparator 10, a mask circuit 12, an output circuit 14, a frequency generation circuit 20, and a mask signal generation circuit 30. The motor drive circuit 100 is a functional IC integrated on a single semiconductor substrate.

  The back electromotive force detection comparator 10 compares the back electromotive voltages Vu to Vw generated in the coils 50a to 50c of each phase of the motor 50 with the midpoint voltage Vn of the multiphase coils, respectively, and the first rectangular wave signal Pu of each phase. ~ Pw is generated. The first rectangular wave signal Pu is at a high level when Vu> Vn, and is at a low level when Vu <Vn. Similarly, the first rectangular wave signal Pv is high when Vv> Vn, and low when Vv <Vn. The first rectangular wave signal Pw is high when Vw> Vn, and low when Vw <Vn. Become a level.

  The mask circuit 12 performs a masking process for removing noise components of the first rectangular wave signals Pv to Pw of each phase output from the back electromotive force detection comparator 10, and outputs the second rectangular wave signals Mu to Mw of each phase. . The output circuit 14 supplies a drive current to the coils 50a to 50c of each phase of the motor 50 based on the second rectangular wave signals Mu to Mw of each phase.

  The frequency generation circuit 20 is a position detection circuit for detecting the position of the rotor, detects the transition edge of the second rectangular wave signals Mu to Mw of each phase, and the level is high for each detected edge. And a frequency generation signal SigFG that switches between low level and low level. For example, the frequency generation signal SigFG can be generated by calculating the exclusive OR of the second rectangular wave signals Mu to Mw.

  The mask signal generation circuit 30 generates a mask signal MSK that is at a high level during a period obtained by multiplying the pulse width Tp of the frequency generation signal SigFG by a predetermined coefficient. The pulse width Tp of the frequency generation signal SigFG refers to the time from the transition of the signal level to the next transition. The mask signal MSK is output to the mask circuit 12.

  The mask signal generation circuit 30 includes a counter 32, a register 34, and a mask width setting circuit 36. The counter 32 counts a clock signal CK input from the outside. The frequency generation signal SigFG is input to the counter 32, and the count value CNT is reset each time the signal level is switched, and counting is started again. Each time the counter 32 is reset, the register 34 sequentially holds the count value CNT at the time of reset. The mask width setting circuit 36 outputs a mask signal MSK that is at a high level for a period corresponding to a numerical value obtained by multiplying the count value CNT held in the register 34 by a predetermined coefficient α.

  The mask circuit 12 performs a masking process for invalidating the level fluctuations of the first rectangular wave signals Pu to Pw during a period when the mask signal MSK is at a high level after any of the first rectangular wave signals Pu to Pw transitions. . That is, even when the signal level of the first rectangular wave signals Pu to Pw varies during the period when the mask signal MSK is at the high level, the variation is not reflected in the second rectangular wave signals Mu to Mw. On the other hand, during the period when the mask signal MSK is at a low level, the second rectangular wave signals Mu to Mw are equal to the first rectangular wave signals Pu to Pw, respectively.

  The output circuit 14 controls the current supplied to the three-phase coils 50 a to 50 c constituting the stator of the motor 50. The output circuit 14 includes a drive signal synthesis circuit 16 and a power transistor circuit 18. The power transistor circuit 18 includes six switching transistors Tr1 to Tr6, and currents supplied to the coils 50a to 50c are turned on and off by turning on and off the transistors Tr1 to Tr6. On / off of the transistors Tr1 to Tr6 is controlled by the drive signal synthesis circuit 16.

  The drive signal synthesis circuit 16 generates drive signals Duu to Dul to be applied to the gates of the transistors Tr1 to Tr6 based on the second rectangular wave signals Mu to Mw output from the mask circuit 12.

  The operation of the motor drive circuit 100 configured as described above will be described. 2A to 2M are time charts showing operation states of the motor drive circuit 100. FIG. 2A to 2C show the back electromotive voltages Vu to Vw generated in the coils 50a to 50c of each phase of the motor 50, and FIG. 2D shows the midpoint voltage Vn of the coils 50a to 50c. (E)-(g) shows the first rectangular wave signals Pu-Pw, (h)-(j) shows the second rectangular wave signals Mu-Mw, and (k) shows the frequency generation signal SigFG. (L) shows the count value CNT held in the register 34, and (m) shows the mask signal MSK.

  A drive current is supplied to the coils 50a to 50c by the output circuit 14, and the resulting back electromotive force voltages Vu to Vw are periodic signals whose phases are shifted from each other by 120 °. The back electromotive force detection comparator 10 compares the back electromotive force voltages Vu to Vw and the midpoint voltage Vn, respectively, and generates first rectangular wave signals Pu to Pw. Spike-like counter electromotive noises Nv1 to Nv3 are generated in the counter electromotive voltages Vu to Vw, and these counter electromotive noises appear as Np1 to Np3 also in the first rectangular wave signals Pu to Pw.

  When the second rectangular wave signal Mu transitions from the low level to the high level at time T0, the frequency generation circuit 20 detects this rising edge (positive edge) and switches the frequency generation signal SigFG to the low level. The counter 32 of the mask signal generation circuit 30 is reset simultaneously with the transition of the frequency generation signal SigFG and starts a new count.

  At time T1 when the back electromotive noise Nv1 appears, the mask signal MSK is at a high level. As described above, the mask circuit 12 invalidates the level fluctuations of the first rectangular wave signals Pu to Pw while the mask signal MSK is at a high level. Therefore, focusing on the W phase, the noise component Np1 appearing in the first rectangular wave signal Pw does not appear in the second rectangular wave signal Mw, and a flat signal from which the influence of back electromotive noise has been removed is obtained.

  At time T2, the mask signal MSK becomes low level, and at time T3, the first rectangular wave signal Pw becomes low level. At time 3, the mask signal MSK is at a low level, and the mask circuit 12 outputs the second rectangular wave signal Mw following the level fluctuation of the first rectangular wave signal Pw, so that the second rectangular wave signal Mw is also low. Become a level. The frequency generation circuit 20 detects a falling edge (negative edge) of the second rectangular wave signal Mw and switches the frequency generation signal SigFG from the low level to the high level. The counter 32 is reset again at time T3, and the count value cnt1 up to that time is written in the register 34. The count value cnt1 is a value corresponding to the pulse width Tp1 of the frequency generation signal SigFG indicated by Tp1 in the drawing. In other words, if the period of the clock signal CK input to the counter 32 is Tck, cnt1 = Tp1 / Tck.

  The mask width setting circuit 36 has a mask period Tmsk1 = α × cnt1 × Tck corresponding to a value (α × cnt1) obtained by multiplying the count value cnt1 written in the mask width setting circuit 36 by a predetermined coefficient α. The mask signal MSK is set to high level. For example, the predetermined coefficient α may be set to about 13/16. Back electromotive noise Nv2 is generated at time T4, and back electromotive noise Np2 appears in the first rectangular wave signal Pv. At time T4 when the back electromotive noise Nv2 appears, the mask signal MSK is at a high level, so no noise component appears in the second rectangular wave signal Mv. Since the mask signal MSK is at the low level at time T5, the mask circuit 12 sets the second rectangular wave signal Mv to the high level at the same time as the first rectangular wave signal Pv becomes the high level. The frequency generation circuit 20 detects the positive edge of the second rectangular wave signal Mv and switches the frequency generation signal SigFG to a low level.

  As described above, according to the motor drive circuit 100 according to the present embodiment, the mask time Tmsk based on the mask signal MSK is changed according to the pulse width Tp of the frequency generation signal SigFG, that is, the rotational speed of the motor 50. As a result, even when the rotational speed of the motor 50 fluctuates, back electromotive noise and the like can be suitably removed from the first rectangular wave signals Vu to Vw, and the motor can be rotated stably.

  Further, in the mask signal generation circuit 30, the register 34 holds the count value CNT for the frequency generation signal SigFG immediately before the mask signal MSK to be output, and the mask time of the mask signal MSK based on this count value. Set Tmsk. As a result, since the previous rotation speed of the motor 50 is reflected in the mask time Tmsk, stable driving can be achieved even when the rotation speed of the motor is rapidly changed.

3A to 3M are time charts showing operation states of the motor drive circuit 100 when the motor 50 is accelerated. FIGS. 3A to 3M show waveforms corresponding to FIGS. 2A to 2M, respectively.
As the rotational speed of the motor 50 increases, the time for supplying the drive current to the coils 50a to 50c of each phase becomes shorter. As a result, the cycle times of the counter electromotive voltages Vu to Vw, the first rectangular wave signals Pu to Pw, and the second rectangular wave signals Mu to Mw are gradually shortened. When the cycle time of the second rectangular wave signals Mu to Mw is shortened, the time Tp for transitioning the signal level of the frequency generation signal SigFG is also shortened, and the count value CNT of the counter 32 held in the register 34 is decreased. As a result, the mask time Tmsk of the mask signal MSK set by the mask width setting circuit 36 gradually decreases as the rotational speed of the motor 50 increases.

  The mask signal generation circuit 30 may set the mask time Tmsk of the mask signal MSK to a predetermined fixed value regardless of the pulse width Tp of the frequency generation signal SigFG at the start of driving of the motor 50. Immediately after the start of driving of the motor 50, no count value is held in the register 34. Therefore, the mask time Tmsk of the mask signal MSK is determined with a predetermined fixed value as an initial value, and the back electromotive noise is removed from the first rectangular wave signals Pu to Pw based on the mask time Tmsk of the mask signal MSK. Thereafter, by setting the mask time Tmsk of the mask signal MSK according to the pulse width Tp of the frequency generation signal SigFG as described above, the motor 50 is stably rotated during the period from the start of driving to the predetermined rotation speed. be able to.

  Similarly, even when the motor 50 is decelerated, the mask time Tmsk of the mask signal MSK is gradually increased by the same operation, and the back electromotive noise can be suitably removed.

Next, an application of the motor drive circuit 100 according to the present embodiment will be described. FIG. 4 is a block diagram showing a configuration of a disk device 200 on which the motor drive circuit 100 of FIG. 1 is mounted. The disk device 200 is a unit that performs recording and reproduction processing on an optical disk such as a CD or a DVD, and is mounted on an electronic device such as a CD player, a DVD player, or a personal computer. The disk device 200 includes a pickup 210, a signal processing unit 212, a disk 214, a motor 50, and a motor driving circuit 100.
The pickup 210 writes desired data by irradiating the disk 214 with a laser, or reads the data written on the disk 214 by reading reflected light. The signal processing unit 212 performs necessary signal processing such as amplification processing, A / D conversion, or D / A conversion on data read and written by the pickup 210. The motor 50 is a spindle motor provided for rotating the disk 214. Since the disk device 200 as shown in FIG. 4 is particularly required to be downsized, a sensorless type that does not use a Hall element or the like is used as the motor 50. The motor drive circuit 100 according to the present embodiment can be suitably used to stably drive such a sensorless spindle motor.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the embodiment, the case of driving a three-phase motor has been described. However, the present invention can also be suitably used for driving a sensorless motor other than the three-phase motor.

  In the embodiment, the counter electromotive detection comparator 10 compares the counter electromotive voltages Vu to Vw generated in the coils 50a to 50c of each phase of the motor 50 with the midpoint voltage Vn of each phase coil. Accordingly, the first rectangular wave signals Pu to Pw may be generated by dividing the voltage using resistors and comparing the divided voltages.

  The high-level and low-level logic settings of the signals described in the embodiment are merely examples, and various modifications can be considered for the configuration of the logic circuit block, and such modifications are also included in the scope of the present invention.

It is a circuit diagram which shows the structure of the motor drive circuit which concerns on embodiment. 2A to 2M are time charts showing operation states of the motor drive circuit of FIG. FIGS. 3A to 3M are time charts showing operation states of the motor drive circuit of FIG. 1 during acceleration of the motor. It is a block diagram which shows the structure of the disc apparatus carrying the motor drive circuit of FIG.

Explanation of symbols

  100 motor drive circuit, 10 back electromotive force detection comparator, 12 mask circuit, 14 output circuit, 20 frequency generation circuit, 30 mask signal generation circuit, 32 counter, 34 register, 50 motor, 200 disk device, 214 disk.

Claims (5)

A motor drive circuit that drives a multiphase motor by supplying a drive current,
A back electromotive force detection comparator that compares the back electromotive voltage generated in each phase coil of the multiphase motor with the midpoint voltage of each phase and generates a first rectangular wave signal of each phase;
A mask circuit that performs a masking process to remove a noise component of the first rectangular wave signal of each phase output from the back electromotive detection comparator, and outputs a second rectangular wave signal of each phase;
Includes a plurality of transistors, based on the second rectangular wave signal of the phase, an output circuit for generating a drive signal to be applied to the gates of the plurality of transistors,
A frequency generation circuit for detecting an edge of the second rectangular wave signal of each phase and generating a frequency generation signal whose level is switched for each detected edge;
A mask signal generation circuit that generates a mask signal that has a predetermined level after a level transition of the frequency generation signal, a period obtained by multiplying a pulse width of the frequency generation signal by a predetermined coefficient;
And the mask circuit performs a masking process for invalidating a level fluctuation of the first rectangular wave signal during a period in which the mask signal is at the predetermined level. The mask signal generation circuit includes:
A counter that is reset at each level transition of the frequency generation signal and starts counting;
A register that holds a count value at reset counted by the counter;
A mask width setting unit that outputs a mask signal having a pulse width corresponding to a numerical value obtained by multiplying the count value held in the register by the predetermined coefficient;
The motor drive circuit according to claim 1, comprising: The mask signal generation circuit includes:
2. The motor drive circuit according to claim 1, wherein the mask signal having a predetermined fixed value as a pulse width is output at the start of driving of the multiphase motor.   4. The motor drive circuit according to claim 1, wherein the motor drive circuit is integrated on a single semiconductor substrate. A spindle motor that rotates the disk;
The motor drive circuit according to any one of claims 1 to 3, which drives the spindle motor;
A disk device comprising:

Images