KR20010103652A - Silent spin sine wave generator - Google Patents

Abstract

A method and circuit for operating a multiphase dc motor in which the driving voltage is applied to the winding of the motor in a predetermined phase is presented. At each winding of the motor a zero crossing of the current flow is detected and the phase of the drive voltage is adjusted to zero crossing substantially simultaneously with the detected zero crossing of the current flow at each winding of the motor. The method includes generating these sets of three waveforms 45, 46, 47 to apply a drive voltage to each winding of the motor. Each waveform has a first segment 43 having a zero value for 120 °, a second segment 50 having a "up-slope" shape for a subsequent 60 °, two consecutive "for subsequent 120 °. A 360 ° period with a third segment having a “cap” shape followed by a fourth segment 52 having a “down slope” shape with respect to 60 °. Each waveform of the set is moved 120 ° from each other. This reduces the acoustic motor noise.

Description

Silent Spin Sine Wave Generator {SILENT SPIN SINE WAVE GENERATOR}

The present invention relates to an improvement in a method and circuit for driving a DC brushles polyphase motor, such as a spindle motor, such as a hard disk drive, in particular a drive that reduces at least acoustic noise in this kind of motor. Improvements in methods and circuits and improvements in driving methods and circuits for driving such motors using drive voltages approximating waveforms substantially constructed from substantially linear approximations of such waveform approximations, constructed substantially from sinusoidal portions. will be.

In the operation of a DC brushless, effective motor drive, a type of multiphase motor to which the present invention relates, requires that the excitation current applied to the motor phase be aligned with the bemf generated by the individual phase. One of the best schemes to achieve this alignment is to use a phase locked loop that adjusts the phase and frequency of the commutation, so that the bemf of the undriven winding passes zero at the center of the appropriate rectification state. This scheme works well when the shape of the commutation waveform includes an undriven region, as in the conventional six states, i.e., +1, +1, 0, -1, -1, 0 sequence.

Since the +1, +1, 0, -1, -1, 0 sequences have sharp transitions between driving states, this sequence has many high frequency components. These tend to excite mechanical resonances in the motor, causing undesirable acoustic noise to be produced. Moreover, the step function tri-state of the undriven motor phase, along with the step function waveform, creates the angle of torque ripple in the motor itself. Torque ripple becomes uneven in motor rotation, which excites resonance in the motor and also generates undesirable acoustic noise.

Thus, if it is desirable to reduce acoustic noise, sinusoidal excitation signals are more suitable than six-state sequences. If the motor driver is configured with a sinusoidal current source, the same voltage sensing PLL described above can be used. However, when the driver's duty cycle changes sinusoidally, the motor drive excitation is pulse width modulated (PWM) to minimize power dissipation in the driver IC. This lowers packaging costs and reduces system costs as a whole. In the past, however, it has been difficult to generate a current with a pure sine wave, especially when the current is relatively high and when a PWM scheme is desired to be used.

In previous application number 09 / 300,754, after the initial baseline erase, the drive waveform consisted of a chain segment of zero at 120 °, followed by “up hook” at 120 ° and “down hook” at 120 °. Up hook and down hook waveforms were generated in two MDACs. The operation of MDAC has a problem that it is difficult to form a desirable drive waveform. In particular, circuit tradeoffs needed to be made so that the resulting waveforms could operate properly in a multiphase DC motor environment.

In addition, forming waveform segments that form themselves from sinusoidal waveform combinations using MDAC requires special MDAC design and operation considerations. Designs that can be constructed from linear waveform segments that approximate sine wave segment combinations will make implementation and operation of such MDACs quite easy.

As a result, there is a need for a disk driver and method that operates by reducing or removing noise associated with driving during operation. There is an additional need for a disk drive and method that employs a drive signal generated from a sinusoidal signal segment and can be generated by easily approximating a concatenated linear signal segment.

Accordingly, in view of the above, it is an object of the present invention to provide an improved disk drive and method which operates by reducing or removing noise associated with the drive during operation.

It is another object of the present invention to provide a disk drive and method that employs multiple drive signals having segments having substantially continuous chain waveforms constructed from or approximating segments of the sine signal.

Other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description when read in conjunction with the accompanying drawings and claims.

Thus, according to a broad aspect of the present invention, a method of operating a three phase dc motor is presented. The method includes generating three sets of waveforms to provide a drive voltage to each winding of the motor. Each waveform has a first segment having a zero value for 120 °, a second segment having a "up slope" shape for 60 ° following it, a second segment having two consecutive "cap" shapes for 120 ° following it. It has a 360 ° period with three segments, a fourth segment having a “down slope” shape for a subsequent 60 °. Each waveform of the set is moved from each other by 120 °. The waveform is then applied to each winding of the motor. Each segment Approx., Where VMAG is the maximum amplitude of each waveform, ωt is the phase angle of the waveform, and φ is the initial phase angle, but in a preferred embodiment each waveform segment comprises at least one linear waveform. Preferably, the waveform segment may have two linear portions with a breakpoint at the center.

According to a broad aspect of the present invention, a method of reducing acoustic noise in operating a multiphase dc motor is presented. The present invention includes generating a set of n waveforms and applying a driving voltage to the windings of each motor, where n is the number of phases of the multiphase dc motor. Each waveform has a 360 ° period, a first segment having a zero value for (360 / n) °, a second segment having a "up slope" shape for (360 / 2n) °, followed by ( A third segment having two consecutive "cap" shapes for 360 / n) °, followed by a fourth segment having a "down slope" shape for (360 / 2n) °. Each waveform of the set is shifted by (360 / n) ° from each other. A waveform is applied to each of the windings of the motor to drive the motor. The waveform may be pulse width modulated with the drive voltage prior to application to the driver.

Each segment

Can be approximated to, where VMAG is the maximum amplitude of each waveform, n is the number of phases of the motor, ωt is the phase angle of the waveform, and φ is the initial phase angle. The waveform segment may comprise at least one linear waveform, and more particularly each of the waveform segments may have two linear portions with breakpoints in the center.

According to another broad aspect of the present invention, a circuit for operating an n-phase dc motor is presented. The circuit has a driver for applying an n drive signal waveform to the motor. A source of drive signal waveforms is provided. Each drive signal waveform is a first segment having a zero value for (360 / n) °, a second segment having a "up slope" shape for (360 / 2n) °, followed by (360 / n) It has a 360 ° period with a third segment having two consecutive "cap" shapes for °, followed by a fourth segment with a "down slope" shape for (360 / 2n) °. Each waveform of the set is shifted from each other by (360 / n) °. The drive signal waveform may comprise substantially linear segments more specifically two linear portions having breakpoints in the center thereof. Circuitry may also be provided to pulse width modulate the drive signal waveform prior to application to the driver.

Each segment

Can be approximated to, where VMAG is the maximum amplitude of each waveform, ωt is the phase angle of the waveform, and φ is the initial phase angle.

According to another broad aspect of the present invention, a disk brush product of a dc brushless, Hall-less, three-phase motor type that rotates data containing media is presented. The product includes a three driver circuit that applies a drive signal to each selected set of windings in the motor. 3 The source of the motor drive voltage waveform provides the drive signal. Each waveform has a 360 ° period. The first segment has zero value for 120 °. The second segment has a "up slope" shape for 60 °. The third segment has two consecutive "cap" shapes for 120 ° and the fourth segment has a "down slope" shape for 60 °. Each waveform of the set is moved from each other by 120 °. The drive signal voltage waveform is formed substantially as a linear segment, more specifically in two linear portions having a breakpoint at the center. Each segment Can be approximated to, where VMAG is the maximum amplitude of each waveform, ωt is the phase angle of the waveform, and φ is the initial phase angle.

In the various figures, like reference numerals are used to indicate same or similar parts.

1 is an ideal drive signal waveform diagram suitable for a three phase dc motor;

2 is a block diagram of a portion of a circuit for applying a drive signal to a multiphase dc motor according to a preferred embodiment of the present invention.

3 is a "up slope" partial waveform diagram generated at the output of one of the MDAC circuits of FIG. 2 to approximate the ideal waveform of FIG. 1 in accordance with a preferred embodiment of the present invention.

4 is a "cap" partial waveform diagram generated at the output of the other of the MDAC circuits of FIG. 1 to approximate the ideal waveform of FIG. 1 in accordance with a preferred embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

12: "cap" MDAC

14: "Slope" MDAC

16: multiplexer

18: three phase dc motor

19: Disk of MDSD

21: Multiplexer Controller

22: clock generator

36: "cap" PWM modulator

38: "Slope" PWM Modulator

According to a preferred embodiment of the present invention, the drive waveform applied to the winding of the motor to be driven is derived from the sinusoidal waveform by the method disclosed in US patent application 09 / 300,754. The motor may be of the type described above, and in particular of the multiphase DC motor type described in US patent application 09 / 300,754. In the illustrated embodiment, the motor is preferably a three phase DC motor.

In the illustrated embodiment, three signals are defined to be shifted 120 degrees out of the other driving each phase of the motor. It should be noted that the motor windings are driven by two of the three coil winding nodes of the driven “Y” coil structure and one is used as a sink, so it is not necessary to drive each node with a pure sine wave. It is sufficient if the voltage difference between the two driven nodes is substantially sinusoidal. A graph showing three consecutive drive waveforms 45, 46, 47 in accordance with a preferred embodiment of the present invention is shown in FIG. 1. Each waveform 45, 46, 47 is applied to and driven by a pair of input terminals of the motor, which are mutually determined, respectively.

To construct the drive waveforms 45, 46, 47, the values of the sine waveforms having instantaneous minimum values of the set of sine waveforms 120 ° cut-of-phase from each other are subtracted from the other waveforms. The set of waveforms shown in FIG. 1 is consequently similar to the set of waveforms disclosed in US patent application 09 / 300,754. Thus, each segment Where VMAG is the maximum amplitude of each waveform, n is the number of phases of the motor, ωt is the phase angle of the waveform, and φ is the initial phase angle. Each waveform has an uphook portion 40 and a downhook portion 42. Thus, while appearing as a sine wave segment, the drive waveform segment is not actually a sine wave segment. Furthermore, each motor phase is triangulated at 120 ° for the commutation cycle and each waveform has a segment 43 that is zero for 120 °.

In accordance with a preferred embodiment of the present invention, a portion 10 of a circuit for applying a drive signal to a multiphase dc motor is shown in FIG. The circuit includes a "cap" generation MDAC 12 and a "slope" generation MDAC 14 to be described below. The cap and slope MDACs 12 and 14 are updated once each PMW CLK cycle and provide shaping signals for selection by the multiplexer 16 for application to a three phase dc motor 18. The dc motor 18 rotates, for example, the spindle of the disk 19 used in the mass data storage device. If desired, the output of MDAC 12, 14 can be pulse width modulated in a known manner by PWM modulators 36, 38 as shown, thereby controlling the power applied to motor 18.

MDAC 14 generates a signal at its output having a slope waveform that can be induced to approximate a segment of a sine wave, particularly a 60 ° segment of the sine wave. MDAC 14 may generate segments in ascending or descending order, such that the ascending waveform substantially follows the “up-slope” segment 50 shown in FIG. 1 or the descending waveform is shown in FIG. 2. As is substantially followed by the "down-slope" segment. If the period of the waveform is considered 360 °, the "up-slope" segment 50 or "down-slope" segment 52 is (360 / 2n) ° in length, where n is the number of phases of the motor.

The waveform generated by the " slope " MDAC 14 is preferably a linear waveform, as shown, for example, by waveform 60 in FIG. As shown, waveform 60 includes a breakpoint 62 about half way between the top and bottom of the waveform, so that the overall shape of each half of waveform 60 is an “up-slope” shown in FIG. 1. It is almost the same curve as segment 50 or "down-slope" segment 60. One of the advantages of using linear waveforms during the operation of MDAC 14 is that it can be easily generated by providing a linear counter that selectively counts up or down at a predetermined rate.

If desired, MDAC 14 may include a scaling circuit that determines the overall amplitude of waveform 60 generated. The scaling circuit can be individually addressably selected to provide the biasing current required for generation of the desired waveform, for example. Also, if desired, waveform 60 may be generated by subtracting the count value from the predetermined bias value.

Similarly, the "cap" MDAC 12 may be configured to generate two consecutive "cap" waveforms 65 as shown in FIG. Each " cap " waveform 65, 66 is formed as a linear up count with a subsequent break point 68, and then linearly counted down to its original starting value. The resulting waveforms 65, 66 correspond to the waveforms 67, 68 in FIG. 1. Again, by using a linear waveform technique with, for example, a linear up and down counter, the sine wave segments 67 and 68 can be easily approximated. Also, if desired, scaling circuitry may be included in MDAC 12, such that the overall scale of the waveform may be determined by, for example, an addressing circuit or the like. If the waveform has a period of 360 °, each cap segment can be a length (360 / 2n) ° over the full length (360 / n) °, where n is the number of motor phases.

The output from each MDAC 12, 14 is selectively applied to the motor control lines 30-32 by the multiplexer circuit 16 for application to the three phase motor 18. The multiplexer circuit 16 is controlled by the multiplexer controller 21 and receives clock pulses from the clock generator 22 divided by the divider circuit 24. For example, the multiplexer controller 21 may be an address circuit that repeatedly applies an address to the multiplexer 16 to generate the repetitive waveforms 45-47 shown in FIG. 1.

If desired, as shown, the output from MDAC 12, 14 may be pulse width modulated by, for example, each PWM modulator 36, 38 shown. Pulse width modulation can be performed in a known manner. Typically, a triangle wave is used as a pass waveform to modulate the signal so that it is only transmitted when greater than the value of the instantaneous triangle wave. One of the advantages that can be realized using the circuit of FIG. 2 is that a common clock signal derived from clock generator 22 can be used to generate linear waveform segments in MDAC circuits 12 and 14, as described above. Since the same clock signal can be used to control the timing between the pulse width modulations of the pulse width modulators 36 and 38, each waveform generated by the MDAC is delayed in the signal applied to the three phase motor 18. And can be easily adjusted to avoid discontinuities.

While the present invention has been described and illustrated at a particular angle, the present disclosure has been made by way of example only, and various changes in combination and arrangement of parts may be made by one skilled in the art without departing from the spirit and scope of the claims to be described below.

According to the present invention, it is possible to reduce or eliminate noise associated with driving during operation of a disk driver, and to generate a multiple drive signal having a segment having a substantially continuous chain waveform constructed from or approximating a segment of the sine signal. It can be adopted.

Claims (26)

In a method of operating a multiphase dc motor, Generating a set of three waveforms to apply a drive voltage to each winding of the motor, each waveform having a first segment having a zero value for 120 ° followed by a “up slope” shape for 60 ° Having a 360 ° period with two segments, a third segment having two consecutive "cap" shapes for a subsequent 120 °, a fourth segment having a "down slope" shape for a subsequent 60 °, Each waveform is moved from each other by 120 °; And Applying the waveform to the respective windings of a motor Method for operating a multiphase dc motor comprising a. 2. The method of claim 1, further comprising pulse width modulating a drive voltage prior to application to the motor windings. The method of claim 1, wherein each of said segments Nice to, and here VMAG is the maximum amplitude of each waveform, ωt is the phase angle of the waveform, φ is the initial phase angle. The method of claim 1, wherein each waveform segment comprises at least one linear waveform. 5. The method of claim 4, wherein each waveform segment has two linear portions having a breakpoint at the center. In a method for reducing acoustic noise in operating a multiphase dc motor, generating a set of n waveforms to apply a driving voltage to the windings of each motor, where n is the number of phases of the multiphase dc motor, each waveform having a first value with a zero value for (360 / n) ° Segment, second segment having a "up slope" shape for (360 / 2n) ° followed by a third segment with two consecutive "cap" shapes for (360 / n) °, followed Have a 360 ° period with a fourth segment having a “down slope” shape with respect to (360 / 2n) ° and each waveform of the set is shifted with each other (360 / n) °; And Applying the waveform to the respective windings of a motor Acoustic noise reduction method when operating a multiphase dc motor comprising a. 7. The method of claim 6, further comprising pulse width modulating the drive voltage prior to application to the winding. The method of claim 6, wherein each of said segments Nice to, and here VMAG is the maximum amplitude of each waveform, n is the number of phases of the motor, ωt is the phase angle of the waveform, φ is the initial phase angle. The method of claim 6, wherein each of the waveform segments comprises at least one linear waveform. 10. The method of claim 9, wherein each of the waveform segments has two linear portions having a breakpoint at the center thereof. In a circuit that operates an n-phase dc motor, A driver for applying an n drive signal waveform to the motor; And The source of the drive signal waveform Including, Each waveform has a first segment with a zero value for (360 / n) °, a second segment with a "up slope" shape for a subsequent (360 / 2n) °, followed by (360 / n) °. Each waveform of the set having a 360 ° period with a third segment having two consecutive “cap” shapes for the fourth segment, followed by a fourth segment having a “down slope” shape for the subsequent (360 / 2n) ° Are circuits which are moved from one another by (360 / n) °. 12. The circuit of claim 11 wherein the source of the drive signal waveform is a first MDAC that generates the "up slope" and "down slope" waveforms and a second MDAC that generates the waveform of the "cap" shape. 13. The circuit of claim 12, wherein the drive signal waveform comprises a substantially linear segment. The circuit of claim 13, wherein each of the waveforms has two linear portions with breakpoints in the center. 12. The circuit of claim 11 further comprising a multiplexer connected to receive the output of the MDAC, wherein the multiplexer is operative to selectively apply the output of the MDAC to the driver. 12. The circuit of claim 11, further comprising circuitry for pulse width modulating a drive signal waveform prior to application to the driver. 12. The circuit of claim 11 wherein n is three. The method of claim 11, wherein the segments are each Nice to, and here VMAG is the maximum amplitude of each waveform, ωt is the phase angle of the waveform, φ is the initial phase angle circuit. In dc brushless, Hall-less, three-phase motor type disk drive products that rotate data containing media, A three driver circuit for applying a drive signal to each selected set of windings in the motor; A source of a 3 motor drive voltage waveform applying the drive signal Including, Each waveform has a first segment having a zero value for 120 °, a second segment having a "up slope" shape for 60 ° following it, a second segment having two consecutive "cap" shapes for 120 ° following it. A disk drive product having a 360 ° period with three segments, a fourth segment having a “down slope” shape for a subsequent 60 °, wherein each waveform in the set is moved from each other by 120 °. 20. The disk drive product of claim 19, wherein each of the driver circuits comprises a pair of FETs connected in series between a power supply and a reference potential, together at a drive signal node. 20. The disk drive product of claim 19, further comprising a multiplexer connected to receive the motor drive voltage waveform and selectively apply the motor drive voltage waveform to the driver circuit. 20. The disk drive product of claim 19, further comprising circuitry for pulse width modulating the motor drive voltage waveform prior to application to the drive circuit. 20. The disk drive product of claim 19, wherein the drive signal voltage waveform comprises a substantially linear segment. 24. The disk drive product of claim 23, wherein each of the waveforms has two linear portions having a breakpoint at the center. The method of claim 24, wherein the segments are each Nice to, and here VMAG is the maximum amplitude of each waveform, ωt is the phase angle of the waveform, φ is a disc drive product with an initial phase angle. 20. The disk drive product of claim 19, wherein the data comprising media is magnetic media of a hard disk drive.