JP2004086982A - Magnetic disk storage system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To safely and quickly retreat a head when power is cut off in a magnetic disk storage device. <P>SOLUTION: This magnetic disk storage device is provided with a spindle motor 310, a magnetic head, a voice coil motor 340 for moving the magnetic head, and a voice coil motor driving circuit 120 for controlling the driving current of the voice coil motor. In this case, a retract control circuit 130 is disposed to detect the moving speed of the head at the time of power cut-off based on a counter electromotive voltage, and to generate a current command value for the voice coil motor driving circuit according to the result of the detection, and a booster circuit is disposed to boost a voltage obtained by flow-rectifying the counter electromotive voltage of the spindle motor. When the power is cut off, the voice coil motor driving circuit and the retract control circuit are operated by the voltage boosted by the booster circuit to control a current supplied to the coil of the voice coil motor, thereby retreating the magnetic head. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control technique for a magnetic disk storage device, and also to a technology effective when applied to motor control when power is cut off such as when a power failure occurs. The present invention relates to a technology effective for use in head retraction control by a voice coil motor for moving a magnetic head for reading / writing information.
[0002]
[Prior art]
In a magnetic disk storage device, a magnetic head for reading / writing information from / to a storage track on a magnetic disk is moved in a radial direction along a surface of the disk in addition to a spindle motor for rotating the magnetic disk. Operation). In a hard disk drive, the magnetic head is configured to glide on the disk surface by wind pressure generated by the rotation of the disk. If the rotation of the disk stops, the magnetic head may contact the disk surface and cause damage. There is. Furthermore, when the magnetic recording density increases and the disk surface becomes a mirror surface, the stopped head may be attracted to the disk surface and the rotation of the disk may be hindered.
Therefore, when the rotation of the disk is stopped, an operation of retracting the magnetic head to a support called a ramp at a standby position outside the disk (referred to as unloading in this specification) is performed. On the other hand, at the start of head seek, it is necessary to move (load) the magnetic head from the ramp position onto the disk. At this time, if the moving speed of the magnetic head by the voice coil motor is too high, the magnetic head may come into contact with the disk surface and damage the disk. Therefore, conventionally, it has been generally practiced to monitor the back electromotive voltage of the voice coil motor to control the moving speed of the magnetic head.
[0003]
[Problems to be solved by the invention]
In the hard disk drive, it is necessary to retreat the magnetic head even when a power failure occurs, for the same reason as the above-described necessity of retreating the magnetic head to the ramp outside the disk when the rotation of the disk is stopped. In this specification, the retracting operation of the head to the lamp when the power is cut off is referred to as “retract”. However, when a power failure occurs, the power supply of the control circuit of the voice coil motor is also shut off, so that the voice coil motor cannot be driven and controlled.
Therefore, an evacuation driver (hereinafter, referred to as a retract driver) is provided separately from a driver for driving a voice coil motor for head seek (hereinafter, referred to as a VCM driver). There has been proposed an invention in which a retract driver is operated with a voltage obtained by rectifying the voltage (see JP-A-7-14331).
[0004]
However, since a power failure occurs suddenly, a power failure may occur when the magnetic head is moved inside the disk, or a power failure may occur when the magnetic head is moved outside. If a power failure occurs while moving the head to the inside of the disk in the direction opposite to the retracting direction, the voice coil motor generates a large driving force to reduce the speed of the magnetic head and move the head in the opposite direction. Need to give to. On the other hand, if a power failure occurs while moving the magnetic head to the outside of the disk, the back electromotive force generated by the voice coil motor must be suppressed unless the motor is braked and the head collides with the ramp. There is a risk that it will.
[0005]
However, since the retract driver according to the prior application is composed of a transistor that performs current source and cannot supply current even if it can supply current, it cannot suppress the back electromotive force of the voice coil motor to apply the brake. There is a defect. Also, when the retract driver is operated with a voltage obtained by rectifying the back electromotive force of the spindle motor when a power failure occurs, a voltage drop corresponding to the forward voltage of the diode occurs with a voltage obtained by simply rectifying the back electromotive force of the spindle motor with a diode bridge. . Therefore, it has become clear that there is a problem that the retract driver cannot be operated sufficiently when the spindle motor is a small motor having a small back electromotive force or when the spindle motor rotates slowly.
[0006]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a control technology of a voice coil motor in a magnetic disk storage device, which can reliably retract a magnetic head when power is cut off.
Another object of the present invention is to limit the back electromotive force generated by the voice coil motor when the power is cut off while the magnetic head is moving toward the ramp outside the disk in the magnetic disk storage device. An object of the present invention is to provide a voice coil motor control technique capable of preventing a magnetic head from hitting a ramp and reducing the reliability of the head by applying a brake.
Still another object of the present invention is to provide a magnetic disk storage device, in which a spindle motor is a small motor having a small back electromotive force, and even when the power is shut off when the rotation of the spindle motor is slow, the back electromotive force of the spindle motor is reduced. It is an object of the present invention to provide a voice coil motor control technique which can drive a voice coil motor with a voltage obtained by rectifying the voltage and retract the magnetic head.
Still another object of the present invention is to detect a moving speed of a magnetic head when power is cut off and control a voice coil motor in accordance with the detected moving speed to safely and promptly retract the head in a magnetic disk storage device. It is an object of the present invention to provide a voice coil motor control technique that can be controlled.
The above and other objects and features of the present invention will become apparent from the description of the present specification and the accompanying drawings.
[0007]
[Means for Solving the Problems]
The following is a brief description of an outline of typical inventions disclosed in the present application.
That is, a spindle motor for rotating a magnetic disk, a magnetic head for reading information from a storage track on the magnetic disk rotated by the spindle motor, and a voice coil motor for moving the magnetic head on the disk A voice coil motor drive circuit that includes a MOS transistor and moves the magnetic head by controlling the drive current of the voice coil motor; and a power supply voltage or a voltage obtained by rectifying a back electromotive voltage generated in the coil of the spindle motor. In a magnetic disk storage device having a booster circuit capable of boosting, a moving speed of a head when power is cut off is detected based on a back electromotive voltage generated in a coil of a voice coil motor when power is cut off. Can generate current command value for coil motor drive circuit A control circuit (retract control circuit) is provided. When the power supply is cut off, the voice coil motor drive circuit and the control circuit are operated by the voltage boosted by the booster circuit to control the current flowing through the coil of the voice coil motor to control the magnetic field. The head is moved to a predetermined standby position.
[0008]
According to the above-described means, since the drive current to the voice coil motor is obtained from the back electromotive force of the spindle motor when the power is cut off, when the power is cut off without providing the power backup means, The magnetic head can be safely retracted. Further, even when the power supply is cut off, the booster circuit is operated to operate the voice coil motor drive circuit and the control circuit with the boosted voltage, so that even when the power supply is cut off, current can flow through the coil of the voice coil motor. Thereby, the magnetic head can be retracted to a predetermined standby position. Moreover, even when the spindle motor is a small motor having a small back electromotive force, the voice coil motor drive circuit is operated with the boosted voltage, so that the magnetic head can be reliably retracted.
[0009]
Further, according to the above-mentioned means, a drive current for retracting the magnetic head when power is cut off is supplied to the voice coil motor coil by using a MOS transistor that supplies a current to the voice coil motor coil during normal operation. In order to operate the voice coil motor driving circuit, even if the power is cut off while moving toward the standby position, the current generated by the back electromotive force generated in the coil of the voice coil motor is generated by the driving MOS transistor. The suction can be performed, whereby the brake is applied to the voice coil motor, thereby preventing the magnetic head from colliding with the ramp at the retracted position and reducing the reliability. Further, since a control circuit for detecting the moving speed of the head when the power is turned off and generating a current command value for the voice coil motor drive circuit according to the detection result is provided, the magnetic head can be more safely and quickly ramped. Can be evacuated.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a motor control system in a magnetic disk storage device to which the present invention is applied.
As shown in FIG. 1, the magnetic disk storage device of this embodiment includes a magnetic disk 300, a spindle motor 310 for driving the magnetic disk 300 at high speed, and information stored in a storage track on the magnetic disk 300. Arm 320 having at its tip a magnetic head HD for reading / writing data, a voice coil motor 340 for moving the magnetic head HD on the magnetic disk 300 via the arm, and a semiconductor integrated device for driving the voice coil motor 340 Motorized driving circuit 100, signal processing circuit 230 for driving magnetic head HD to write to magnetic disk 300 and detect position information based on a read signal, and controls the entire operation of the magnetic disk storage device Output head position command information (track position). A compensator that sends a value corresponding to a difference between the position command information from the controller 260 and the position information (servo signal) detected by the signal processing circuit 230 to the motor drive circuit 100 as a drive current command value 280, and so on. A ramp 350 is disposed outside the magnetic disk 300 and supports the arm 320 when the disk rotation is stopped. The ramp 350 has a latch portion 351 for locking the arm 320.
[0011]
The controller 260 includes a microcomputer (CPU) and the like. In this case, the function of the compensator 280 can also be taken into the CPU. The drive current command value output from the compensator 280 is sent to the motor drive circuit 100, and the voice coil motor 340 is drive-controlled. The motor drive circuit 100 includes a spindle motor driver 110, a VCM driver 120, a retract control circuit 130, and a boost circuit 140 for boosting a power supply voltage. Further, the motor drive circuit 100 includes a D / A converter 150 that converts a digital data format drive current command value supplied from the compensator 280 into an analog format drive current command value, and serially outputs from the compensator 280. A serial I / O (input / output port) 155 that receives the supplied drive current command value, converts it into parallel data, and inputs it to the D / A converter 150, and a power supply monitor circuit 160 that detects the occurrence of a power failure are provided. I have.
[0012]
FIG. 2 shows an embodiment of a motor drive control circuit in the magnetic disk storage device of FIG.
In FIG. 2, LVCM is a drive coil of a voice coil motor 340 for moving a magnetic head on a magnetic disk, Rsns is a sense resistor for current detection connected in series with the coil LVCM, and 120 is a VCM driver. The driver 120 drives a voice coil motor by passing a current corresponding to the output of the D / A converter 150 to the coil LVCM. The VCM driver 120 is coupled to the connection terminals P1 and P2 of the coil LVCM and supplies N-channel type power MOSFETs M7, M8, M9 and M10 for flowing a current through the coil, and gate voltages of these power MOSFETs M7, M8, M9 and M10. And a control amplifier that compares the detection value of the sense resistor Rsns with the output value of the D / A converter 150 to generate an input signal for the coil drive amplifiers 121 and 122. 123. As a result, a current that matches the drive current command value input to the D / A converter 150 flows through the coil LVCM.
[0013]
In this embodiment, the voltage between both ends of the drive coil LVCM of the voice coil motor 340 is input to the retract control circuit 130, and when the power failure occurs, the VCM driver 120 is controlled to apply a brake to the voice coil motor 340 or to retract the magnetic head. The retract control for causing the operation is performed.
[0014]
Reference numeral 140 denotes a boost circuit including a charge pump for boosting the power supply voltage Vcc, and reference numeral 145 denotes an oscillator for generating an operation clock φc of the boost circuit 140. The boost circuit 140 is constituted by, for example, a booster circuit such as a charge pump, and operates at a voltage Vspn obtained by rectifying the back electromotive force of the spindle motor 310 when a power failure occurs to boost the voltage to about twice or three times Vspn. I do.
[0015]
The boost voltage Vbst boosted by the boost circuit 140 is stored in the smoothing capacitor C1. The stored boost voltage Vbst is supplied as a power supply voltage to the coil drive amplifiers 121 and 122 that control the gate voltages of the power MOSFETs M7, M8, M9, and M10 that supply current to the coil of the voice coil motor 340 when a power failure occurs. Even if the power MOSFETs M7, M8, M9, M10 are composed of N-channel MOSFETs, they can be sufficiently turned on and the magnetic head can be retracted. The reason why N-channel MOSFETs are used as the power MOSFETs M7, M8, M9, and M10 is that the chip size can be reduced as compared with the case where P-channel MOSFETs are used.
[0016]
In the present embodiment, the oscillator 145 is also configured to be operated by the boost voltage Vbst boosted by the boost circuit 140. The oscillator 145 can be operated by the back electromotive force of the spindle motor when a power failure occurs, similarly to the boost circuit 140. However, by using the boost voltage Vbst, when the power supply voltage switches from the power supply voltage Vcc to the back electromotive force Vspn when a power failure occurs. In this case, it is possible to prevent the oscillation operation from stopping due to the temporary absence of the voltage. Since the oscillator 145 can be constituted by a known circuit such as a ring oscillator, illustration and description of a specific circuit will be omitted.
[0017]
In FIG. 2, reference numeral 161 denotes a comparator constituting the power supply monitor circuit 160, and 162 denotes a power supply / cutoff power supply switch for which the SW2 is operated and turned on / off by the output of the comparator 161. The comparator 161 uses the power supply voltage Vcc as a power supply, the power supply voltage Vcc is applied to the non-inverting input terminal, the reference voltage Vref is applied to the inverting input terminal, and the output P-OFF of the comparator 161 is supplied while the power supply voltage Vcc is supplied. Is set to a high level to turn on the power switch 162 at a voltage obtained by multiplying R2 by I3, and when the power supply voltage Vcc is cut off, the output P-OFF of the comparator 161 is changed to a low level and SW2 is turned off. And the power switch 162 is turned off. The reason why the power switch 162 is turned off is to prevent the back electromotive force of the spindle motor 310 from flowing back to the power supply side. The power supply of the comparator 161 may use the boost voltage Vbst boosted by the boost circuit 140.
[0018]
Lu, Lv, and Lw are coils of a spindle motor that rotationally drives the magnetic disk. Although not particularly limited, in this embodiment, a three-phase brushless motor is used as the spindle motor. Reference numeral 110 denotes output transistors M1, M2, M3, M4, M5, and M6 connected between the coupling terminals of the coils Lu, Lv, and Lw and the power supply voltage terminal and the ground terminal, respectively, and supplies current to each coil of the spindle motor. A spindle driver circuit for driving the motor to rotate, a control circuit for determining a phase coil through which a current flows based on a back electromotive force of each coil, and 112, 113, and 114 receiving a control signal from the control circuit 111 and outputting the same. This is a preamplifier that controls the transistors M1 to M6 to be turned on and off, respectively, and allows current to flow sequentially through the coils Lu, Lv, and Lw. The control circuit 111 controls the current flowing to each coil by a PWM (pulse width modulation) method during normal operation, and controls on / off of a transistor performing rectification based on the back electromotive force of each coil when a power failure occurs. Is performed.
[0019]
In this embodiment, even if the synchronous rectification control is not performed, each of the output transistors M1 to M6 is constituted by an N-channel MOSFET, and the body diodes D1 to D6 parasitic between their sources and drains are provided. It can operate as a rectifier circuit that rectifies the back electromotive force generated in the coils Lu, Lv, and Lw of the spindle motor and supplies power to the spindle motor driver circuit 110 and the boost circuit 140. In this embodiment, the voltage boosted by the boost circuit 140 is supplied to the VCM driver circuit 120 that drives the voice coil motor 340, the retract control circuit 130, the spindle driver circuit 110, and the like.
[0020]
When the spindle driver circuit 110 is configured to operate at the voltage boosted by the boost circuit 140 when a power failure occurs, the power supply Vcc-side transistor of that phase when the back electromotive voltage is the highest of the three phases, By performing synchronous rectification control to turn on the ground-side transistor when the back electromotive voltage is the lowest, the amount of voltage drop can be reduced, so that even when the back electromotive voltage of the spindle motor is small, that is, when the rotation speed is low, the voice is reduced. By driving the coil motor, the retreat operation can be reliably performed.
[0021]
FIG. 3 shows a configuration example of the retract control circuit 130. In FIG. 3, the drive coil LVCM of the voice coil motor 340 is represented as an equivalent circuit including an original inductance Lvcm, an internal resistance Rvcm, and a voltage source Vbemf that generates a back electromotive voltage.
The retract control circuit 130 generates a control signal for operating a circuit inside the control circuit in a predetermined order, a voltage sense amplifier 132 for detecting a voltage VVCM between terminals of the drive coil LVCM, and a detected voltage VVCM. A / D conversion circuit 133 for converting to a digital value, register 134 for holding the A / D-converted value, and difference between voltage command value VBEMFC supplied from sequencer 131 and feedback voltage * VBEMF from coil. A first subtractor 135, an integration circuit (digital filter) 136 for integrating the output of the subtractor 135, and a multiplication circuit 137 for calculating the product of the output of the integration circuit 136 and the value held in the register 134; , A second subtractor 1 that calculates a difference between the output of the multiplication circuit 137 and the output of the A / D conversion circuit 133. And 8, and is configured from a timer 139.
[0022]
By providing the integration circuit 136, a subtractor 135-integration circuit 136-D / A converter 150-VCM driver 120-back electromotive force Vbemf-voltage sense amplifier 132-A / D conversion circuit 133-subtractor 138-subtractor 138 can be prevented from oscillating.
[0023]
A drive current command value supplied from the compensator 280 via the serial I / O 155 or the output of the integration circuit 137 is selectively supplied between the integration circuit 137 and the D / A converter 150. A changeover switch SW1 for inputting to the / A converter 150 is provided. This switch SW1 allows the D / A converter 150 to input the drive current command value supplied from the compensator 280 in the normal operation state by the output (power cutoff detection signal) P-OFF of the power monitor circuit 160. When a power outage occurs, the operation of inputting the output of the integration circuit 137 to the D / A converter 150 is performed.
[0024]
In this embodiment, when the timer 139 monitors the output of the integration circuit 136 and detects that the magnetic head has reached the latch position of the ramp 350, it starts a timekeeping operation, and sends a time-up signal to the sequencer 131 when a predetermined time has elapsed. The sequencer 131 sends a brake signal BRK to the spindle motor control circuit 110 to stop the rotation of the spindle motor 310.
[0025]
The timer 139 may be configured to send a time-up signal to the sequencer 131 when a predetermined time has elapsed from the time of occurrence of a power failure. In this case, the time measured by the timer 131 is desirably determined in consideration of the longest time required for the magnetic head to move from an arbitrary position on the magnetic disk to the outer ramp position. Further, the timer 139 can be operated by the clock signal φc supplied from the oscillator 145 to the boost circuit 140.
[0026]
The sequencer 131 includes a ROM (Read Only Memory) that stores a microprogram including a plurality of instruction codes, a counter that sequentially reads instructions from the ROM, and a decoder that decodes the read instructions and generates a control signal. And a circuit having a configuration similar to that of the microprogram type control circuit or a random logic.
[0027]
Since the voltage command value VBEMFC supplied to the subtractor 135 can be a fixed value, if the sequencer 131 has a ROM for storing the instruction code, it is stored in the ROM as a part of the instruction code or separately from the instruction code. Then, it can be configured to output at a predetermined timing. Further, a register may be provided instead of the ROM, and the voltage command value VBEMFC may be set in the register via the serial I / O 155 from the controller 260 by initialization processing or the like at the time of system startup. Alternatively, the voltage command value VBEMFC may be given using a wiring logic that generates a predetermined code by a wiring connected to the power supply voltage Vcc or the ground point. When a register is used, a voltage command value VBEMFC corrected according to the characteristic variation can be set for each system.
[0028]
Next, a specific operation of the retract control circuit 130 shown in FIG. 3 when a power failure occurs will be described with reference to the flowchart of FIG. 4 and the timing chart of FIG. FIG. 5 shows a case where a power failure occurs during the movement of the magnetic head from the inside to the outside of the disk. When the magnetic head is moved from the inside to the outside, the power MOSFETs M7 and M10 are turned on and the M8 and M9 are turned off in the VCM driver circuit 120, and the coil LVCM of the voice coil motor has a terminal P1 (VCMP terminal). A current Id flows from the terminal to P2 (VCMN terminal).
[0029]
When the master power supply (Vcc) drops due to a power failure or the like, the output P-OFF of the power supply monitor circuit 160 changes to low level, and the power switch 162 is turned off (timing t1 in FIG. 5). Then, a voltage Vspn obtained by rectifying the back electromotive force generated in the coils Lu, Lv, Lw of the spindle motor is supplied to the VCM driver circuit 120 and the boost circuit 140. Further, in the boost circuit 140, the booster voltage Vbst obtained by boosting the power supply voltage Vcc before the power is cut off is held by the smoothing capacitor C1, so that the boost circuit 140 and the oscillator 145 continue to operate even after the power is cut off, and the booster voltage Vbst becomes lower. Generated.
[0030]
Here, since the spindle driver circuit 110 is operated by the boosted voltage Vbst generated by the boost circuit 140 and performs synchronous rectification control, Vspn is equal to the power supply voltage Vcc by the voltage drop VR due to the on-resistance of the output transistors M1 to M6. Lower voltage. However, this voltage drop VR is smaller than the voltage drop (forward voltage of the diode) due to the body diodes of the output transistors M1 to M6 when the synchronous rectification control is not performed.
[0031]
Further, when the master power supply (Vcc) drops, the switch SW1 in the VCM driver circuit 120 is switched by the output P-OFF from the power supply monitor circuit 160, and instead of the current command value from the compensator 280, the retract control circuit 130 Is supplied to a DA converter (DAC) 150.
[0032]
In the retract control circuit 130, when the power cutoff detection signal P-OFF is input to the sequencer 131, a high-level clear signal CLR is sent from the sequencer 131 to the integration circuit 136, and a driver is sent to the VCM driver circuit 120. Is output as a control signal HI-Z which causes the output of the control signal HI to become high impedance. As a result, the integration circuit 136 is cleared, the output n is set to, for example, the reference value “1”, and the drive current of the coil LVCM of the voice coil motor 134 is cut off (step S1 in FIG. 4).
[0033]
Then, at this time, the magnetic head continues to move by inertia, and a back electromotive force BEMF proportional to the moving direction and speed of the head (a positive back electromotive voltage when moving to the outside; (A negative back electromotive voltage) is generated. In this state, the sequencer 131 applies the store signal STORE to the register 134, converts the voltage Vvcm detected by the voltage sense amplifier 132 from A / D by the A / D conversion circuit 133, and sets the value Vvcmd as the initial voltage value Vtemp in the register 134. (Step S2). Accordingly, the head moving speed at the time of the occurrence of the power failure is held in the register 134.
[0034]
Next, the sequencer 131 cancels the output high impedance command to the VCM driver circuit 120 so that a predetermined reference current Io flows through the coil LVCM in order to detect a voltage drop due to the parasitic resistance Rvcm of the coil LVCM. As a result, the VCM driver circuit 120 is driven (step S3 in FIG. 4, timing t2 in FIG. 5). The reference current Io flowing through the coil at this time is about several mA in accordance with the time constant of the coil so as not to change the moving speed of the head, and is set to a short period such as several hundred μsec. . Specifically, when the output n of the integration circuit 136 is “1”, a reference current Io that does not change the head speed is caused to flow through the coil.
[0035]
Then, the voltage between the terminals of the coil is detected by the voltage sense amplifier 132 while the reference current Io is being supplied, and a value Vvcmd obtained by converting the voltage into a digital value by the A / D conversion circuit 133 and the head held in the register 134 are output. The voltage value Vtemp corresponding to the moving speed is supplied to the subtractor 138, and the value obtained by taking the difference is stored in the register 134 again (step S4). At this time, since the output n of the integration circuit 136 is set to n = 1 by the clear signal, the value held in the register is Vvcmd-Vtemp. As a result, the voltage drop (Io × RL) due to the parasitic resistance Rvcm of the coil LVCM is held in the register 134. When the voltage drop amount when n = “1” is (Io × RL), the voltage drop amount due to the parasitic resistance Rvcm is n × (Io × RL) due to the driving current flowing through the coil LVCM when n changes. It is.
[0036]
Subsequently, the sequencer 131 outputs the target speed command value VBEFMC of the magnetic head, sets the clear signal CLR to the integration circuit 136 to low level, and starts the closed loop control (step S5). Then, the value obtained by subtracting the output of the second subtractor 138 from the target speed command value VBEMFC by the first subtractor 135, that is, the control error amount, is input to the integration circuit 136.
[0037]
Here, the output of the second subtractor 138 is obtained from the value Vvcmd (= * Vbemf + nIo · RL) obtained by A / D conversion of the voltage Vvcm (= Vbemf + n · Io · RL) between both terminals of the coil from the output of the register 134. A value obtained by subtracting a value (n · Io · RL) obtained by multiplying the held value (Io · RL) by the output n of the integration circuit 136 by the multiplier 137, that is, an estimated back electromotive voltage value * Vbemf. Therefore, the value input to the integration circuit 136 from the first subtractor 135 is VBEMFC- * Vbemf (= target speed command value-back coil electromotive force).
[0038]
Thus, the coil of the voice coil motor 340 is driven by the VCM driver circuit 120 so that the moving speed of the magnetic head becomes the target speed, and the speed is accurately controlled by the control loop of the control circuit 130 (step S6). For example, when the moving speed of the magnetic head is lower than the target speed or when the head is moving inward, the output * Vbemf of the second subtractor 138 becomes smaller than the target speed command value VBEMFC. The output of the circuit 136 increases, and a forward current (current for moving the head outward) flows through the coil to accelerate the head.
[0039]
On the other hand, as shown in the timing chart of FIG. 5, when the moving speed of the magnetic head is higher than the target speed, the output * Vbemf of the second subtractor 138 becomes higher than the target speed command value VBEMFC. The output of 136 is reduced, and a reverse current (current for moving the head inward) is supplied to the coil to decelerate the head (timing t3 to t4). When the head reaches the ramp and the speed of the head decreases, the back electromotive force of the coil tends to decrease. However, control is performed in the direction in which the output of the integration circuit 136 increases to maintain the head speed at the target value. As a result, the driving force of the coil is increased, and the head can move up the ramp (timing t4 to t5).
[0040]
Further, in this embodiment, the integration circuit 136 is provided with a limiter for limiting the maximum level of the output. Therefore, when the head reaches the stop position (latch) of the ramp and the speed decreases, the output of the integrating circuit 136 increases to maintain the head speed at the target value. At this time, the limiter operates to limit the output level. In addition, it is possible to avoid a sudden increase in the driving force of the coil, thereby preventing the head from coming off the ramp (timing t5 to t6).
[0041]
Further, in this embodiment, when the limiter of the integration circuit 136 is activated, the timer 139 is started, and the sequencer 131 sends the spindle motor control circuit 110 a predetermined time after the activation of the timer 139. A brake start signal BRK is output (timing t6). Then, the ground-side transistors M2, M4 and M6 of the drive transistors M1 to M6 of the spindle motor, for example, are all turned on by the spindle motor control circuit 110, and the spindle motor is braked.
As a result, the voltage Vspn obtained by rectifying the back electromotive force generated in the coils Lu, Lv, and Lw of the spindle motor and the booster voltage Vbst obtained by boosting the voltage by the boost circuit 140 drop, and the driving of the voice coil motor 340 is stopped. (Timing t7).
[0042]
In the conventional head retracting method using a retract driver composed of source-follower type MOSFETs, the current of the coil cannot be drawn, so a power failure occurs while the magnetic head is moving from the inside to the outside of the disk. Then, since the brake is not applied to the voice coil motor, the magnetic head may collide with the ramp. On the other hand, in the present embodiment, as described above, since the retraction operation is performed using the VCM driver circuit 120 that can draw the current in any direction of the coil, the moving speed toward the outside of the magnetic head is too fast. In this case, the coil current can be drawn to brake the voice coil motor 340, and the magnetic head can be prevented from colliding with the ramp. In addition, in this embodiment, since the moving speed of the head at the time of the occurrence of the power failure is detected and the current flowing to the voice coil motor is controlled accordingly, the evacuation operation with higher precision can be performed.
[0043]
FIG. 6 shows an embodiment of the VCM driver 120. In FIG. 6, the coil LVCM of the voice coil motor 340 is represented as an equivalent circuit including an original inductance Lvcm, an internal resistance Rvcm, and a back electromotive force source Vbemf. As shown in FIG. 6, the VCM driver circuit 120 includes coil drive amplifiers 121 and 122 that drive power MOSFETs M7, M8, M9, and M10 that supply current to the coils, detection values of the sense resistor Rsns, and It comprises a control amplifier 123 for comparing output values of the D / A converter 150 to generate input signals for the coil drive amplifiers 121 and 122, a voltage switch SW1, and the like. The coil drive amplifier 121 (122) includes an output amplifier 210 (220), a feedback resistor R2 (R6), and input resistors R1, R3, R4 (R5, R7, R8).
[0044]
Further, the control amplifier 123 includes a current sense amplifier 231 to which the voltage of both terminals of the current sense resistor Rsns is input, and a voltage input to which the output of the current sense amplifier 231 and the output of the D / A converter 150 are input. A current output type differential amplifier circuit (hereinafter, referred to as a gm amplifier) 232 and a phase compensation circuit 233 for compensating the phase of the current control loop. A reference voltage VREF is applied to one input terminal of the output amplifiers 210 and 220 and one input terminal of the current sensing amplifier 231 via resistors R1, R7 and R12, respectively, and a voltage corresponding to a potential difference between the reference voltage VREF and each input voltage. Is output.
[0045]
The amplifiers 231 and 232 are set such that circuit operating characteristics such as gain are each desired characteristics by optimally determining the constants of elements such as resistors and transistors in the amplifiers. The amplifiers 231 and 232 use the power supply voltage Vspn and the booster voltage Vbst as power supplies, and the operation of the amplifiers is continued even when a power failure occurs.
[0046]
The coil drive amplifiers 121 and 122 have predetermined voltage gains set by the resistors R1 to R4 and R5 to R8, respectively. The coil drive amplifiers 121 and 122 use the boosted boost voltage Vbst as a power supply, and the operation of the amplifiers is continued even if a power failure occurs. The coil Lvcm of the voice coil motor 108 and the sense resistor Rsns are connected in series between the coil terminals VCMP-VCMN to which the power MOSFETs M7 to M10 driven by the coil drive amplifiers 121 and 122 are connected. A drive current is supplied to the coil Lvcm by the power MOSFETs M7 to M10. This drive current is configured to be able to flow in both directions by a pair of coil drive amplifiers 121 and 122, and the magnetic head can be arbitrarily set in either the inside or outside direction of the disk according to the direction in which the drive current flows. Is moved in the direction of.
[0047]
FIG. 7 shows a specific circuit configuration example of the output amplifier 210 (220) in the circuit shown in FIG.
As shown in FIG. 7, the output amplifier 210 (220) includes a differential amplifier 211 that receives the voltage output from the control amplifier 232 or the retract control voltage Vret and the reference voltage VREF, A gm amplifier 212 to which a voltage obtained by dividing the output of the amplifier 211, the voltage of the coil terminal VCMP (VCMN), and the reference voltage VCMREF by the resistors R5 and R6 is input, and one of the differential outputs of the gm amplifier 212 is non-inverted. A pair of buffer amplifiers 213 and 214 operating as receiving voltage followers at input terminals; phase compensation capacitors C11 and C12 connected between non-inverting input terminals of the buffer amplifiers 213 and 214 and a power supply voltage terminal; Between the non-inverting input terminals of the amplifiers 213 and 214 and the coil terminal VCMP (VCMN) It is constituted respectively connected in series with a resistor R7 and a MOSFET M3 and R8 and the like M4.
[0048]
The gm amplifier 212 is an amplifier whose characteristics are set so that the output changes almost linearly in accordance with the change in the output voltage of the preceding-stage differential amplifier 211. The inverting input terminal (-) of the amplifier 212 has a voice input terminal. The voltage of the coil terminal VCMP (VCMN) to which the coil Lvcm of the coil motor is connected is fed back via the resistor R6, and the gm amplifier 212 is connected to the buffer amplifiers 213 and 214 and the output transistors M7 and M8 connected to the subsequent stage. The constants of the elements constituting the circuit are set so that the entire circuit including the circuit amplifies the input voltage with high gain and outputs a drive voltage that changes according to a change in input.
[0049]
Next, a circuit portion including the buffer amplifiers 213 and 214 provided between the gm amplifier 212 and the output transistors M7 and M8 in FIG. 7 will be described.
As shown in FIG. 7, the positive-phase output (+) of the gm amplifier 212 is input to the non-inverting input terminal of the buffer amplifier 213, and the output voltage of the buffer amplifier 213 is applied to the gate terminal of the output transistor M7. ing. The output voltage of the buffer amplifier 213 is fed back to its own inverting input terminal, and operates as a voltage follower. The reason why such an amplifier is provided is that the output transistor M1 has a large size and therefore a large gate capacitance, and the driving force becomes insufficient to directly drive the output of the gm amplifier 212 while maintaining desired characteristics. is there.
[0050]
The resistor R7 and the MOS transistor M3 connected in series between the positive-phase output terminal of the buffer amplifier 213 and the coil terminal VCMP are connected to the MOS transistor M3 because the buffer amplifier 213 operates as a voltage follower. And the voltage applied to the gate of the output transistor M7 is the same, and it can be seen that M7 and M3 form a current mirror circuit. Therefore, assuming that the size ratio between the MOS transistors M7 and M3 is N, the output transistor M7 is driven to flow a current N times the drain current of M3.
[0051]
Similarly, the negative phase output (-) of the gm amplifier 212 is input to the non-inverting input terminal of the buffer amplifier 214, and the output voltage of the buffer amplifier 214 is applied to the gate terminal of the output transistor M9. The output voltage of the buffer amplifier 214 is fed back to its own inverting input terminal, and the buffer amplifier 214 operates as a voltage follower. Further, the resistor R8 and the MOS transistor M4 connected in series between the positive-phase output terminal of the buffer amplifier 214 and the coil terminal VCMP have a voltage applied to the gate of the MOS transistor M4 and the gate of the output transistor M8. Since they are the same, M4 and M8 constitute a current mirror circuit. Therefore, assuming that the size ratio between the MOS transistors M2 and M6 is N, the output transistor M8 is driven to flow a current N times the drain current of M4.
[0052]
The resistors R7 and R8 provided in series with the transistors M3 and M4 have little meaning when a relatively small current is input from the gm amplifier 212. When a relatively large current is input from the gm amplifier 212 and a large current flows through the transistors M3 and M4, the gate-source voltage of the transistors M3 and M4 suddenly increases when the input current exceeds a certain value. Will be done. As a result, the gate-source voltages of the output transistors M7 and M8 are controlled so as to change more steeply than the change in the input voltage of the gm amplifier 212.
[0053]
In the circuit of FIG. 7, the voltage between the gate and the source of the output transistor M7 is set up by, for example, appropriately setting the amplitude level of the positive-phase output and the negative-phase output of the gm amplifier 212. It is designed so that the fall starts earlier than the rise of the gate-source voltage of the output transistor M8. As a result, the output transistors M7 and M8 are turned on at the same time to prevent a through current from flowing, thereby suppressing an increase in power consumption. Similarly, the rise of the gate-source voltage of the output transistor M8 may be designed to start earlier than the fall of the gate-source voltage of the output transistor M7.
[0054]
FIG. 8 shows a configuration example of a circuit for performing synchronous rectification control of the spindle motor when performing a retraction control of the magnetic head particularly when a power failure occurs in the control circuit 111 in the spindle driver circuit 110 shown in FIG. .
In FIG. 8, reference numeral 410 denotes a PWM control unit that generates a control signal for PWM control during normal operation, 420 denotes a synchronous rectification control unit that generates a control signal for synchronous rectification control during retract control, and 430 denotes PWM control. A selector section 440 that selects either the control signal output from the section 410 or the control signal output from the synchronous rectification control section 420 and supplies it to the preamplifiers 112 to 114 in FIG. 2 is supplied from the boost circuit when a power failure occurs. The logic power supply unit generates a power supply Vddsr necessary for the operation of the logic circuit in the synchronous rectification control unit 420 by lowering the boost voltage Vbst.
[0055]
The logic power supply unit 440 includes a resistor voltage dividing circuit that divides the boost voltage Vbst by the resistors R21 and R22 to generate a desired potential, and a buffer amplifier AMP that outputs a voltage having the same level as the divided voltage with low impedance. Consists of The selector unit 430 is switched by the output P-OFF from the power supply monitor circuit 160, and selects the output from the synchronous rectification control unit 420 instead of the output from the PWM control unit 410 when the power supply is cut off, and selects the coils U and V , W supplied to the selectors SEL1 to SEL6.
[0056]
The synchronous rectification control unit 420 compares comparators CMP1, CMP2, and CMP3 for comparing terminal voltages U, V, and W of the U-phase, V-phase, and W-phase drive coils of the spindle motor composed of a three-phase brushless motor two by two. And AND gates G1 to G6 to which a combination of the output signals of these comparators CMP1, CMP2 and CMP3 and their inverted signals are input, and detects the magnitude of the back electromotive voltage of the coil and sends it to each coil. By determining the direction and timing of the current, synchronous rectification control for driving the coil in synchronization with the rotation of the motor is performed. Specifically, control is performed such that a power supply Vcc-side output transistor of the phase having the highest back electromotive voltage and a ground side output transistor of the phase having the lowest back electromotive voltage are turned on so that current flows through the coil.
[0057]
FIG. 9 is a block diagram showing a configuration example of an entire hard disk drive as an example of a magnetic disk system including a voice coil motor control system, a spindle motor control system, and a magnetic head drive control system having the configuration as shown in FIG. Things.
9, reference numeral 310 denotes a spindle motor for rotating the magnetic disk 300; 320, an arm having a magnetic head (including a write magnetic head and a read magnetic head) HD at its tip; and 330, a carriage for rotatably holding the arm 320. The voice coil motor 340 moves the magnetic head by moving the carriage 330, and the motor drive circuit 100 performs servo control so that the center of the magnetic head coincides with the center of the track.
[0058]
The motor drive circuit 100 is a semiconductor integrated circuit in which a voice coil motor drive control circuit and a spindle motor drive control circuit as shown in FIG. 2 are integrated, and operates according to a control signal supplied from the controller 260. Then, the servo control of the voice coil motor 340 and the spindle motor 310 is performed so as to move the magnetic head to a desired track or to keep the relative speed of the magnetic head constant.
[0059]
200 amplifies a current corresponding to a change in magnetism detected by the magnetic head HD and transmits a read signal to a signal processing circuit (data channel processor) 230 or amplifies a write pulse signal from the signal processing circuit 230. This is a read / write IC that outputs a drive current for the magnetic head HD. Reference numeral 240 denotes a hard disk which receives read data transmitted from the signal processing circuit 230 and performs error correction processing, or performs error correction encoding processing on write data from the host and outputs the data to the signal processing circuit 230.・ It is a controller. The signal processing circuit 230 performs signal processing such as modulation / demodulation processing suitable for digital magnetic recording and waveform shaping in consideration of magnetic recording characteristics, and reads position information from a read signal of the magnetic head HD.
[0060]
Reference numeral 250 denotes an interface controller for transferring and controlling data between the system and an external device. The hard disk controller 240 is connected to a host computer such as a microcomputer of a personal computer via the interface controller 250. . Reference numeral 270 denotes a buffer cache memory for temporarily storing read data read from the magnetic disk at high speed. A system controller 260 including a microcomputer determines which operation mode is based on a signal from the hard disk controller 240, controls each part of the system in accordance with the operation mode, and is supplied from the hard disk controller 240. A sector position or the like is calculated based on the address information.
[0061]
As described above, the invention made by the inventor has been specifically described based on the embodiments. However, it is noted that the present invention is not limited to the above embodiments, and that various changes can be made without departing from the gist of the invention. Not even. For example, in the above-described embodiment, the power required after the power is turned off is extracted by performing synchronous rectification control on the output transistors M1 to M6 that drive the spindle motor. May be obtained by rectifying the back electromotive force with the body diode described above, or a diode bridge for rectification may be separately provided.
[0062]
Further, in the embodiment, a lamp as a standby position is provided outside the disk and the magnetic head is retracted to this lamp when the power is turned off. However, a standby position is provided inside the disk and the magnetic head is Can be applied to the case in which the disk is retracted to the inside of the disk.
[0063]
In the above description, the case where the invention made by the present inventor is mainly applied to a hard disk storage device, which is the field of use as the background, has been described. However, the present invention is not limited to the present invention. Can be used.
[0064]
【The invention's effect】
The following is a brief description of an effect obtained by a representative one of the inventions disclosed in the present application.
That is, in the magnetic disk storage device, since the moving speed of the magnetic head when the power is turned off is detected and the voice coil motor is controlled based on the moving speed and the target speed, the magnetic head is safely and quickly retracted. When the power is cut off while the magnetic head is being moved toward the ramp outside the disk, the back electromotive force generated by the voice coil motor is limited and the brake is applied by applying a brake to the magnetic head. Collision can be prevented.
[0065]
Further, according to the present invention, in the magnetic disk storage device, even when the power is cut off when the rotation of the small motor or the spindle motor with a small back electromotive force is slow, the voice coil is synchronously rectified with the back electromotive force of the spindle motor. The magnetic head can be reliably retracted by driving the motor. As a result, the retract driver is not required, and the chip size of the drive control IC for the voice coil motor can be reduced, so that a small and highly reliable magnetic disk storage device can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a voice coil motor and a spindle motor control system in a magnetic disk storage device according to the present invention.
FIG. 2 is a block diagram showing one embodiment of a drive control circuit for a voice coil motor and a spindle motor in the magnetic disk storage device according to the present invention.
FIG. 3 is a block diagram illustrating a more detailed configuration example of a retract control circuit that performs evacuation control of the voice coil motor when a power failure occurs.
FIG. 4 is a flowchart illustrating an example of a procedure of a retract control of the voice coil motor when a power failure occurs by the retract control circuit of the embodiment.
FIG. 5 is a timing chart showing timings of signals of respective units during a retract control of the voice coil motor when a power failure occurs by the motor drive control circuit of the embodiment.
FIG. 6 is a block diagram illustrating a more detailed configuration example of a coil drive circuit (VCM driver) included in a drive control circuit of the voice coil motor.
FIG. 7 is a block diagram showing a specific example of an output amplifier constituting a coil drive circuit (VCM driver).
FIG. 8 is a block diagram showing a more detailed configuration example of a drive control circuit of a spindle motor.
FIG. 9 is a block diagram showing an overall schematic configuration of a magnetic disk storage device to which the present invention is applied.
[Explanation of symbols]
LVCM Voice coil motor drive coil
Rsns Current detection resistor
100 Motor drive control circuit (IC)
110 Spindle motor driver
120 Voice coil motor driver
121,122 Coil drive amplifier
123 Control amplifier
130 Retraction control circuit
131 PLC
132 Voltage sense amplifier between coil terminals
135,138 subtractor
137 Multiplier
140 boost circuit (boost circuit)
210, 220 output amplifier
300 magnetic disk
310 spindle motor
320 Arm for holding head
330 carriage
340 voice coil motor
350 Head retract position (ramp)

Claims (10)

A first motor for rotating a magnetic disk, a magnetic head for reading information from a storage track on the magnetic disk rotated by the first motor, and a second motor for moving the magnetic head on the disk A second motor drive circuit including a field effect transistor for controlling a current flowing through a coil of the second motor and controlling a gate voltage of the transistor in accordance with a current command value to move the magnetic head; A control circuit capable of generating a current command value for the two-motor drive circuit; and a booster circuit capable of boosting a power supply voltage or a voltage obtained by rectifying a back electromotive voltage generated in the coil of the first motor,
The control circuit detects the moving speed of the head based on the back electromotive voltage generated in the coil of the second motor in a state where the transistor is turned off when the power is turned off, and generates a current command value so as to reach the target speed. Supply to the second motor drive circuit,
The second motor drive circuit operates with the voltage boosted by the booster circuit, and controls the current flowing through the coil of the second motor in accordance with a current command value from the control circuit when the power supply is cut off, thereby controlling the magnetic head to a predetermined value. A magnetic disk storage system configured to be moved to a standby position. The control circuit includes a register and a subtraction and multiplication circuit, detects a back electromotive voltage corresponding to a moving speed of a head generated in the coil in a state where the transistor is turned off when power is turned off, and stores the back electromotive force in the register, A reference current that does not affect the moving speed of the head is applied to detect the voltage between both ends of the coil, and a potential difference due to the parasitic resistance of the coil is obtained from the value held in the register by the subtraction circuit and held in the register. After that, the voltage between both ends of the coil is detected, and the product of the current difference and the potential difference with respect to the reference current due to the parasitic resistance held in the register is corrected as the potential difference due to the current parasitic resistance. 2. The magnetic device according to claim 1, wherein a current command value to be supplied to the second motor drive circuit is generated based on a value giving a speed. Disk storage system. The current command value is a digital value, a DA converter circuit for converting the current command value into an analog signal, and a current generated by the control circuit in the event of power supply interruption in place of a current command value supplied from outside during normal operation. 3. The magnetic disk storage system according to claim 1, further comprising switching means for supplying a command value to the DA conversion circuit. A first motor drive control circuit that includes a transistor that causes a current to flow through the coil of the first motor and controls the drive current of the coil to control the rotation of the magnetic disk; the first motor drive control circuit operates normally The transistor is sometimes driven by a pulse width control method, and the back electromotive voltage of the first motor is rectified by sequentially driving the transistor in synchronization with the rotation of the first motor when power is cut off. Item 4. A magnetic disk storage system according to any one of Items 1 to 3. The control circuit includes a timer circuit, and sends a signal for instructing the first motor drive control circuit to stop the rotation of the first motor when a predetermined time has elapsed after power-off, and the first motor drive control circuit 5. The magnetic disk storage system according to claim 4, wherein a brake is applied to the rotation of the first motor in response to the instruction signal. The control circuit includes:
Voltage detection means for detecting a voltage between terminals of the coil of the second motor, an A / D conversion circuit for converting a voltage detected by the voltage detection means into a digital value, an integration circuit for integrating a target speed value, A multiplication circuit for obtaining a product of the output of the integration circuit and the value held in the register; a first subtraction circuit for obtaining a difference between an output of the multiplication circuit and an output of the A / D conversion circuit; and a first subtraction circuit And a control loop including a second subtraction circuit for calculating a difference between the output of the above and the target speed command value,
When the transistor is turned off when the power is turned off, a back electromotive voltage corresponding to the moving speed of the head generated in the coil is detected and held in the register, and a reference current that does not affect the moving speed of the magnetic head is detected. The voltage between both ends of the coil is detected, and the potential difference due to the parasitic resistance of the coil is obtained from the value held in the register by the first subtraction circuit and held in the register. And a value obtained by subtracting the product of the current difference and the potential difference from the reference current due to the parasitic resistance held in the register by the first subtraction circuit from the both-ends voltage as the potential difference due to the current parasitic resistance. The difference between the calculated value and the target speed value is obtained by the second subtraction circuit, and the result obtained by integrating the result by the integration circuit is supplied to the DA conversion circuit. Magnetic disk storage system according to claim 3, characterized in that it is configured to control the current flowing through the coil of the second motor with. 7. The magnetic disk storage system according to claim 6, wherein the integration circuit has a limiter function for limiting a maximum output. A first motor drive control circuit that includes a transistor that causes a current to flow through the coil of the first motor and controls the drive current of the coil to control the rotation of the magnetic disk; the first motor drive control circuit operates normally The transistor is sometimes driven by a pulse width control method, and the back electromotive voltage of the first motor is rectified by sequentially driving the transistor in synchronization with the rotation of the first motor when power is cut off. Item 8. The magnetic disk storage system according to item 6 or 7. The control circuit includes a timer circuit, and sends a signal for instructing the first motor drive control circuit to stop the rotation of the first motor to the first motor drive control circuit when a predetermined time has elapsed after the limiter has functioned. 9. The magnetic disk storage system according to claim 8, wherein the motor drive control circuit is configured to brake the rotation of the first motor in response to the instruction signal. A first motor for rotating a magnetic disk, a magnetic head for reading information from a storage track on the magnetic disk rotated by the first motor, and a second motor for moving the magnetic head on the disk A second motor drive circuit including a field effect transistor for controlling a current flowing through a coil of the second motor and controlling a gate voltage of the transistor in accordance with a current command value to move the magnetic head; A control circuit for generating a current command value for the two-motor drive circuit, a booster circuit for further boosting a power supply voltage or a voltage obtained by rectifying a back electromotive voltage generated in the coil of the first motor, and a And a system controller for providing a target value of the current flowing through the coil of the second motor.
A voltage obtained by rectifying a back electromotive voltage generated in the coil of the first motor when power is cut off is boosted by the booster circuit, and the second motor drive circuit and the control circuit are operated by the boosted voltage by the booster circuit; The control circuit detects a back electromotive voltage corresponding to the moving speed of the head generated in the coil of the second motor in a state where the transistor is turned off when the power is turned off, and determines the moving speed of the magnetic head according to the detection result. A command value of a current flowing through the coil of the second motor is generated so as to be equal to the command value and supplied to the second motor drive circuit, and a current flowing through the coil of the second motor without the intervention of the system control device And the magnetic head is moved to a predetermined standby position.

Images