JP4138402B2 - Magnetic disk storage system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technology effective for applying control technology for a magnetic disk storage device and further to motor control when power is cut off when a power failure occurs. For example, the present invention relates to a storage track on a magnetic disk in a hard disk device. The present invention relates to a technique which is effective for use in head retraction control by a voice coil motor that moves a magnetic head for reading / writing information.
[0002]
[Prior art]
In addition to the spindle motor that rotates the magnetic disk, the magnetic disk storage device moves a magnetic head that reads / writes information from / to a storage track on the magnetic disk in the radial direction along the surface of the disk (seeking). Voice coil motor to be operated). In hard disk drives, the magnetic head is configured to glide on the disk surface with the wind pressure generated by the rotation of the disk. When the disk rotation stops, the magnetic head may come into contact with the disk surface and damage it. There is. Further, 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 (referred to as unloading in this specification) is performed in which the magnetic head is retracted to a support called a ramp at a standby position outside the disk. On the other hand, when the head seek operation is started, 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 fast, the magnetic head may come into contact with the disk surface and be damaged. For this reason, conventionally, the back electromotive force of the voice coil motor is monitored to control the moving speed of the magnetic head.
[0003]
[Problems to be solved by the invention]
In a hard disk device, for the same reason as the necessity of retracting the magnetic head to the lamp outside the disk when the disk rotation is stopped, it is necessary to retract the magnetic head even when a power failure occurs. In this specification, the retracting operation of the head to the lamp when the power is shut off is referred to as “retract”. However, when a power failure occurs, the power supply to the control circuit for the voice coil motor is also cut off, so that the voice coil motor cannot be driven and controlled.
Therefore, a retraction driver (hereinafter referred to as a retract driver) is provided separately from a driver for driving a head seek voice coil motor (hereinafter referred to as a VCM driver), and the back electromotive force of the spindle motor in the event of a power failure. An invention has been proposed in which a retract driver is operated with a voltage obtained by rectifying the current (Japanese Patent Laid-Open No. 7-14331).
[0004]
However, since a power failure occurs suddenly, a power failure may occur when the magnetic head is moved to the inside of the disk, or a power failure may occur when the magnetic head is moved to the outside. If a power failure occurs while moving the head to the inner side of the disk opposite to the retracting direction, the voice coil motor provides a large driving force that can reduce the speed of the magnetic head and move it further in the reverse 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 motor will not brake and the head will collide with the ramp unless the back electromotive force generated by the voice coil motor is suppressed. There is a risk that.
[0005]
However, the retract driver according to the invention of the prior application is composed of a transistor that performs current source and cannot be pulled in even if current can be supplied, so that it cannot suppress the back electromotive force of the voice coil motor and apply the brake. There is a bug. 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 when the back electromotive force of the spindle motor is simply rectified by a diode bridge. . Therefore, it has been clarified that there is a problem that the reduct driver cannot be operated sufficiently in the case of a small motor with a small back electromotive force of the spindle motor or when the spindle motor rotates slowly.
[0006]
An object of the present invention is to provide a control technique for a voice coil motor capable of reliably retracting a magnetic head when a power source is cut off in a magnetic disk storage device.
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 when the magnetic head is moving in the ramp direction outside the disk in the magnetic disk storage device. It is an object of the present invention to provide a control technique for a voice coil motor capable of applying a brake and preventing a magnetic head from colliding with a ramp and reducing the reliability of the head.
Still another object of the present invention is to provide a back electromotive force of a spindle motor in a magnetic disk storage device even when the spindle motor is a small motor having a small back electromotive force or when the power is cut off when the spindle motor rotates slowly. It is an object of the present invention to provide a control technique for a voice coil motor that can drive a voice coil motor with a voltage obtained by rectifying the current and retract a magnetic head.
Still another object of the present invention is to detect the moving speed of the magnetic head when the power is cut off in the magnetic disk storage device and control the voice coil motor according to the moving speed to safely and quickly retract the head. It is an object of the present invention to provide a voice coil motor control technique that can be implemented.
The above and other objects and features of the present invention will be apparent from the description of this specification and the accompanying drawings.
[0007]
[Means for Solving the Problems]
Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
That is, a spindle motor that rotates a magnetic disk, a magnetic head that reads information from a storage track on the magnetic disk rotated by the spindle motor, and a voice coil motor that moves the magnetic head on the disk And a voice coil motor drive circuit that includes a MOS transistor to move the magnetic head by controlling the drive current of the voice coil motor, and a voltage obtained by rectifying a power supply voltage or a back electromotive voltage generated in the spindle motor coil. In a magnetic disk storage device having a booster circuit capable of boosting, the moving speed of the head when the power is cut off is detected based on a back electromotive voltage generated in the coil of the voice coil motor when the power is turned off, and the voice is detected according to the detection result. Can generate a current command value for the coil motor drive circuit A control circuit (retract control circuit) is provided to operate the voice coil motor drive circuit and the control circuit with the voltage boosted by the booster circuit when the power is turned off 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, the power is cut off without providing a power backup means. The magnetic head can be safely retracted. In addition, since the booster circuit is operated even when the power is shut down and the voice coil motor drive circuit and the control circuit are operated by the boosted voltage, a current can flow through the coil of the voice coil motor even when the power is shut off. Thus, the magnetic head can be retracted to a predetermined standby position. Moreover, even if the spindle motor is a small motor with a small back electromotive force, the voice coil motor drive circuit is operated with the boosted voltage, so that the magnetic head can be retracted reliably.
[0009]
Further, according to the above-described means, a MOS transistor that allows current to flow through the coil of the voice coil motor during normal operation is used so that a drive current that causes the magnetic head to retract when the power is shut off flows through the coil of the voice coil motor. Even if the power is cut off when moving toward the standby position to operate the voice coil motor drive circuit, the current generated by the back electromotive force generated in the coil of the voice coil motor is generated by the driving MOS transistor. Thus, the voice coil motor can be braked to prevent the magnetic head from colliding with the lamp at the retracted position and reducing the reliability. Furthermore, the magnetic head is ramped more safely and quickly because it has a control circuit that detects the moving speed of the head when the power is shut off and generates a current command value for the voice coil motor drive circuit according to the detection result. Can be evacuated.
[0010]
DETAILED DESCRIPTION OF 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 that drives the magnetic disk 300 to rotate at high speed, and information on storage tracks on the magnetic disk 300. An arm 320 having a magnetic head HD for reading / writing the head, a voice coil motor 340 for moving the magnetic head HD on the magnetic disk 300 via the arm, and a semiconductor integrated circuit for driving the voice coil motor 340 Control circuitized motor drive circuit 100, signal processing circuit 230 for driving the magnetic head HD to perform writing on the magnetic disk 300 and detecting position information based on the read signal, and the operation of the entire magnetic disk storage device Output head position command information (track position) A controller 260, a compensator for sending a value corresponding to the difference based on 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, etc. 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 that locks the arm 320.
[0011]
The controller 260 is composed of a microcomputer (CPU) or 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 driven and controlled. In the motor drive circuit 100, a spindle motor driver 110, a VCM driver 120, a retract control circuit 130, and a boost circuit 140 that boosts the power supply voltage are provided. 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 a serial output from the compensator 280. A serial I / O (input / output port) 155 that receives the supplied drive current command value and converts it into parallel data and inputs the parallel data to the D / A converter 150, and a power supply monitor circuit 160 that detects the occurrence of a power failure are provided. Yes.
[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 that moves the magnetic head on the magnetic disk, Rsns is a sense resistor for current detection connected in series with this coil LVCM, 120 is a VCM driver, and this VCM The driver 120 supplies the coil LVCM with a current corresponding to the output of the D / A converter 150 to drive the voice coil motor. The VCM driver 120 is coupled to the connection terminals P1 and P2 of the coil LVCM, and N-channel power MOSFETs M7, M8, M9, and M10 that pass current through the coils, and gate voltages of these power MOSFETs M7, M8, M9, and M10. A pair of coil drive amplifiers 121 and 122 for controlling the control, and a control amplifier for comparing the detection value of the sense resistor Rsns and the output value of the D / A converter 150 to generate an input signal of 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 is passed through the coil LVCM.
[0013]
In this embodiment, the voltage across 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 brake the voice coil motor 340 or retract the magnetic head. Retraction control for causing the operation is performed.
[0014]
Reference numeral 140 denotes a boost circuit including a charge pump that boosts the power supply voltage Vcc. Reference numeral 145 denotes an oscillator that generates an operation clock φc of the boost circuit 140. The boost circuit 140 is constituted by a booster circuit such as a charge pump, for example. When a power failure occurs, the boost circuit 140 operates with a voltage Vspn obtained by rectifying the counter electromotive force of the spindle motor 310 and boosts the voltage to a voltage about 2 to 3 times Vspn. To do.
[0015]
The boost voltage Vbst boosted by the boost circuit 140 is stored in the smoothing capacitor C1. The accumulated 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 flow current to the coil of the voice coil motor 340 when a power failure occurs. Even if the power MOSFETs M7, M8, M9, and M10 are N-channel MOSFETs, they can be sufficiently turned on to retract the magnetic head. The reason why the 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 the P-channel MOSFETs are used.
[0016]
In this 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 as in the boost circuit 140. However, when the power supply voltage Vcc is switched to the back electromotive force Vspn when a power failure occurs, the boost voltage Vbst is used. Therefore, it is possible to avoid the oscillation operation from being stopped due to the voltage being temporarily lost. Since the oscillator 145 can be configured by a known circuit such as a ring oscillator, illustration and description of a specific circuit are omitted.
[0017]
In FIG. 2, reference numeral 161 denotes a comparator constituting the power supply monitor circuit 160, and 162 denotes a power supply / shutoff power switch that is controlled to be turned on / off by the operation of SW <b> 2 by the output of the comparator 161. The comparator 161 uses the power supply voltage Vcc as the power supply, the power supply voltage Vcc is applied to the non-inverting input terminal and 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 the high level, and the power switch 162 is turned on with the voltage obtained by multiplying R2 by I3. When the power supply voltage Vcc is cut off, the output P-OFF of the comparator 161 is changed to the low level and the 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 source 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. 110 comprises output transistors M1, M2, M3, M4, M5, and M6 connected between the coupling terminals of the coils Lu, Lv, and Lw, 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 rotating the motor, 111 a control circuit for determining a phase coil through which a current flows based on the counter electromotive force of each coil, and 112, 113, 114 receiving the control signal from the control circuit 111 and outputting the above-mentioned output This is a preamplifier in which the transistors M1 to M6 are turned on and off, respectively, and currents are sequentially supplied to the coils Lu, Lv, and Lw. The control circuit 111 controls the current flowing through each coil by a PWM (pulse width modulation) method during normal operation, and controls on / off of a transistor that performs rectification based on the back electromotive force of each coil when a power failure occurs. Synchronous rectification control is performed.
[0019]
In this embodiment, even if the synchronous rectification control is not performed, the output transistors M1 to M6 are constituted by N-channel MOSFETs, respectively, and body diodes D1 to D6 parasitic between their source and drain are provided. It can operate as a rectifier circuit that rectifies the back electromotive voltage 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]
Since the spindle driver circuit 110 is configured to be operated with the voltage boosted by the boost circuit 140 when a power failure occurs, the power source Vcc side transistor of the phase is also turned on when the back electromotive voltage is the highest among the three phases. By performing synchronous rectification control to turn on the ground side transistor when the back electromotive force voltage is the lowest, the voltage drop can be reduced, so that even when the back electromotive force voltage of the spindle motor is small, that is, when the rotation speed is slow, The coil motor can be driven to perform the retreat operation reliably.
[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 comprising the original inductance Lvcm, the internal resistance Rvcm, and a voltage source Vbemf that generates a counter electromotive voltage.
The retract control circuit 130 includes a sequencer 131 that generates a control signal for operating the circuits in the control circuit in a predetermined order, a voltage sense amplifier 132 that detects a voltage VVCM between terminals of the drive coil LVCM, and a detected voltage VVCM. The A / D conversion circuit 133 for converting to a digital value, the register 134 for holding the A / D converted value, the voltage command value VBEMFC supplied from the sequencer 131 and the feedback voltage * VBEMF from the coil are taken. A first subtractor 135, an integration circuit (digital filter) 136 that integrates the output of the subtractor 135, and a multiplication circuit 137 that calculates the product of the output of the integration circuit 136 and the value held in the register 134; , A second subtractor 138 for taking a difference between the output of the multiplier circuit 137 and the output of the A / D converter circuit 133, a timer 139, etc. It is al configuration.
[0022]
By providing the integration circuit 136, the subtractor 135-integration circuit 136-D / A converter 150-VCM driver 120-back electromotive voltage Vbemf-voltage sense amplifier 132-A / D conversion circuit 133-subtracter 138-subtractor It is possible to prevent the speed control loop composed of 138 from oscillating.
[0023]
Further, between the integration circuit 137 and the D / A converter 150, the 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 D. A changeover switch SW1 for input to the / A converter 150 is provided. The changeover switch SW1 causes 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 the power failure occurs, the output of the integration circuit 137 is operated to be input to the D / A converter 150.
[0024]
In this embodiment, when the timer 139 monitors the output of the integrating circuit 136 and detects that the magnetic head has reached the latch position of the ramp 350, the timer starts a time measuring operation. The feed 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 since the occurrence of a power failure. In this case, the time measured by the timer 131 is preferably 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. The timer 139 can be operated by a clock signal φc supplied from the oscillator 145 to the boost circuit 140.
[0026]
The sequencer 131 includes a ROM (read only memory) storing a microprogram composed of 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. It can be configured by a circuit having a configuration similar to the microprogram control circuit or random logic.
[0027]
Since the voltage command value VBEMFC supplied to the subtracter 135 can be a fixed value, when 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. However, 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 from the controller 260 via the serial I / O 155 by initialization processing or the like at the time of system startup. Alternatively, the voltage command value VBEMFC may be given using wiring logic that generates a predetermined code by the power supply voltage Vcc or wiring connected to the ground point. When the register is used, the 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 situation where a power failure occurs while moving the magnetic head from the inside to the outside of the disk. When the magnetic head is moved from the inside to the outside, in the VCM driver circuit 120, the power MOSFETs M7 and M10 are turned on, M8 and M9 are turned off, and the coil LVCM of the voice coil motor has a terminal P1 (VCMP terminal). Current Id from P2 to P2 (VCMN terminal) flows.
[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 a low level and the power switch 162 is turned off (timing t1 in FIG. 5). Then, the voltage Vspn obtained by rectifying the back electromotive voltage generated in the coils Lu, Lv, and Lw of the spindle motor is supplied to the VCM driver circuit 120 and the boost circuit 140. In the boost circuit 140, the booster voltage Vbst obtained by boosting the power supply voltage Vcc before the power supply is held by the smoothing capacitor C1, so that the boost circuit 140 and the oscillator 145 continue to operate even after the power supply is cut off. 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 the power supply voltage Vcc by the voltage drop VR due to the ON resistances 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]
When the master power supply (Vcc) is dropped, the switch SW1 in the VCM driver circuit 120 is switched by the output P-OFF from the power supply monitor circuit 160, and the retract control circuit 130 instead of the current command value from the compensator 280. 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 output from the sequencer 131 to the integration circuit 136, and a driver is output to the VCM driver circuit 120. A control signal HI-Z for making the output of the high impedance output is output. As a result, the integration circuit 136 is cleared and the output n is set to the reference value “1”, for example, and the voice coil motor 134 cuts off the drive current of the coil LVCM (step S1 in FIG. 4).
[0033]
Then, at this time, the magnetic head continues to move by inertia, and between the terminals of the coil LVCM, a counter electromotive voltage BEMF proportional to the moving direction and speed of the head (a positive counter electromotive voltage when moving outward, an inner side) Negative back electromotive force) occurs. In this state, the sequencer 131 gives the store signal STORE to the register 134 and A / D-converts the voltage Vvcm detected by the voltage sense amplifier 132 by the A / D conversion circuit 133, and uses the register 134 as the initial voltage value Vtemp. (Step S2). As a result, the head moving speed when the power failure occurs is held in the register 134.
[0034]
Next, the sequencer 131 cancels the output high impedance command to the VCM driver circuit 120 so as to flow a predetermined reference current Io to 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 according to the time constant of the coil so as not to change the moving speed of the head, and is 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 supplied to the coil.
[0035]
The voltage between the terminals of the coil during the application of the reference current Io is detected by the voltage sense amplifier 132, converted into a digital value by the A / D conversion circuit 133, and the head held in the register 134. A voltage value Vtemp corresponding to the moving speed is supplied to the subtractor 138, and a value obtained by taking the difference between them is stored in the register 134 again (step S4). At this time, since the output n of the integration circuit 136 is n = “1” by the clear signal, the value held in the register is Vvcmd−Vtemp. As a result, the voltage drop amount (Io × RL) due to the parasitic resistance Rvcm of the coil LVCM is held in the register 134. If the voltage drop when n = “1” is (Io × RL), the voltage drop due to the parasitic resistance Rvcm is n × (Io × RL) due to the drive current flowing in the coil LVCM when n changes. It is.
[0036]
Subsequently, the sequencer 131 outputs the target speed command value VBEFMC of the magnetic head and sets the clear signal CLR for the integration circuit 136 to the low level to start closed loop control (step S5). Then, a value obtained by subtracting the output of the second subtracter 138 from the target speed command value VBEMFC by the first subtractor 135, that is, a control error amount is input to the integrating circuit 136.
[0037]
Here, the output of the second subtracter 138 is obtained from the value Vvcmd (= * Vbemf + n · Io · RL) obtained by A / D conversion of the voltage Vvcm (= Vbemf + n · Io · RL) between both terminals of the coil. A value obtained by subtracting a value (n · Io · RL) obtained by multiplying the holding 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 from the first subtractor 135 to the integration circuit 136 is VBEMFC− * Vbemf (= target speed command value−coil back 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 subtracter 138 is smaller than the target speed command value VBEMFC. The output of the circuit 136 is increased, and a forward current (current in a direction to move the head outward) is caused to flow 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 larger than the target speed, the output * Vbemf of the second subtracter 138 is larger than the target speed command value VBEMFC, so that the integration circuit The output of 136 is reduced, and a reverse current (current that moves the head inward) is applied to the coil to decelerate the head (timing t3 to t4). When the head reaches the ramp and the head speed decreases, the counter electromotive force of the coil tends to decrease, but control is performed in such a way that the output of the integration circuit 136 increases in order to keep 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 lamp (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 ramp stop position (latch) and the speed decreases, the output of the integration circuit 136 increases to maintain the head speed at the target value. At this time, the limiter operates to limit the output level. Thus, it is possible to avoid a sudden increase in the driving force of the coil, thereby preventing the head from coming off the lamp (timing t5 to t6).
[0041]
In this embodiment, the timer 139 is activated when the limiter of the integrating circuit 136 is activated, and the sequencer 131 detects the spindle motor control circuit 110 when a predetermined time elapses after the timer 139 is activated. The brake start signal BRK is output (timing t6). Then, the spindle motor control circuit 110 turns on all of the ground side transistors M2, M4, and M6, for example, of the drive transistors M1 to M6 of the spindle motor, and brakes the spindle motor.
As a result, the voltage Vspn obtained by rectifying the counter electromotive voltage generated in the coils Lu, Lv, and Lw of the spindle motor and the booster voltage Vbst boosted by the boost circuit 140 are lowered, and the driving of the voice coil motor 340 is also stopped. (Timing t7).
[0042]
In the head retract method using a retract driver composed of a conventional source follower type MOSFET, the coil current 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 voice coil motor is not braked, the magnetic head may collide with the lamp. On the other hand, in this embodiment, as described above, the retraction operation is performed using the VCM driver circuit 120 that can draw the current in any direction of the coil, so that the moving speed toward the outside of the magnetic head is too high. 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 lamp. In addition, in this embodiment, since the moving speed of the head at the time of the occurrence of a power failure is detected and the current flowing through the voice coil motor is controlled accordingly, a more accurate retreat operation is possible.
[0043]
FIG. 6 shows an embodiment of the VCM driver 120 described above. In FIG. 6, the coil LVCM of the voice coil motor 340 is represented as an equivalent circuit including the original inductance Lvcm, the internal resistance Rvcm, and the counter electromotive voltage source Vbemf. As shown in FIG. 6, the VCM driver circuit 120 includes power drive MOSFETs M7, M8, M9, and M10 that pass current through the coils, coil drive amplifiers 121 and 122, and a detected value of the sense resistor Rsns and the above It comprises a control amplifier 123 that compares the output value of the D / A converter 150 and generates an input signal of the coil drive amplifiers 121 and 122, a voltage changeover 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]
The control amplifier 123 also has a current sense amplifier 231 to which the voltage at both terminals of the current sense resistor Rsns is input, and a voltage input that receives the output of the current sense amplifier 231 and the output of the D / A converter 150 as inputs. A current output type differential amplifier circuit (hereinafter referred to as a gm amplifier) 232 and a phase compensation circuit 233 that performs phase compensation of the current control loop. A reference voltage VREF is applied to one input terminal of each of the output amplifiers 210 and 220 and the current sense amplifier 231 via resistors R1, R7, and R12, 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 so that circuit operation characteristics such as gain become desired characteristics by optimally determining the constants of 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 amplifier is continued even when a power failure occurs.
[0046]
The coil drive amplifiers 121 and 122 have predetermined voltage gains set by 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 source, and the operation of the amplifier 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 passed through the coil Lvcm by the power MOSFETs M7 to M10. This drive current is configured to flow in both directions by the pair of coil drive amplifiers 121 and 122, and the magnetic head can be arbitrarily set in either the inner or outer direction of the disk depending on the direction in which the drive current flows. It is designed to move 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 having the voltage output from the control amplifier 232 or the retract control voltage Vret and the reference voltage VREF as inputs, and this differential. The 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 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 a voltage follower at the input terminal, capacitors C11 and C12 for phase compensation connected between the non-inverting input terminal and the power supply voltage terminal of the buffer amplifiers 213 and 214, and a buffer In series between the non-inverting input terminal of the amplifiers 213 and 214 and the coil terminal VCMP (VCMN), respectively. It is configured of a connection to a resistor R7 and a MOSFET M3 and R8 and M4.
[0048]
The gm amplifier 212 is an amplifier whose characteristics are set so that the output changes almost linearly according to the change in the output voltage of the differential amplifier 211 in the previous stage. The inverting input terminal (−) of the amplifier 212 has a voice The voltage of the coil terminal VCMP (VCMN) to which the coil Lvcm of the coil motor is connected is fed back through the resistor R6, and the gm amplifier 212 and the buffer amplifiers 213 and 214 and the output transistors M7 and M8 connected to the subsequent stage are connected. As a whole circuit including the above, constants of elements constituting the circuit are set so as to amplify the input voltage with a high gain and output a drive voltage that changes in accordance with a change in input.
[0049]
Next, a circuit portion including 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 buffer amplifier 213 operates as a voltage follower with its output voltage fed back to its inverting input terminal. The reason why such an amplifier is provided is that the output transistor M1 is large in size and has a large gate capacity, and the driving force is insufficient to drive directly with the output of the gm amplifier 212 while maintaining the desired characteristics. is there.
[0050]
The resistor R7 and the MOS transistor M3 connected in series between the positive phase side output terminal of the buffer amplifier 213 and the coil terminal VCMP are the MOS transistor M3 because the buffer amplifier 213 operates as a voltage follower. It can be seen that the voltage applied to the gate of the output transistor M7 and the gate of the output transistor M7 are the same, and M7 and M3 constitute a current mirror circuit. Accordingly, if the size ratio of the MOS transistors M7 and M3 is N, the output transistor M7 is driven to pass 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 buffer amplifier 214 operates as a voltage follower with its output voltage fed back to its inverting input terminal. Further, the resistor R8 and the MOS transistor M4 connected in series between the positive phase side 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, the output transistor M8 is driven so as to flow a current N times the drain current of M4, where N is the size ratio of the MOS transistors M2 and M6.
[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 from the point where the input current exceeds a certain value. Will come to be. As a result, the gate-source voltage of the output transistors M7 and M8 is controlled to change more rapidly than the change in the input voltage of the gm amplifier 212.
[0053]
In the circuit of FIG. 7, for example, by setting the amplitude level of the positive phase side output and the amplitude level of the negative phase side output of the gm amplifier 212 appropriately, the gate-source voltage of the output transistor M7 is raised. The fall is designed to start earlier than the rise of the gate-source voltage of the output transistor M8. As a result, the output transistors M7 and M8 are simultaneously turned on so that no through current flows, and an increase in power consumption is suppressed. Similarly, the rise of the gate-source voltage of the output transistor M8 may be designed so that the rise starts earlier than the fall of the gate-source voltage of the output transistor M7.
[0054]
FIG. 8 shows a configuration example of a circuit that performs synchronous rectification control of the spindle motor when the magnetic head retract control is performed especially when a power failure occurs in the control circuit 111 in the spindle driver circuit 110 shown in FIG. .
In FIG. 8, 410 is a PWM control unit that generates a control signal for PWM control during normal operation, 420 is a synchronous rectification control unit that generates a control signal for synchronous rectification control during retract control, and 430 is PWM control. The selector unit 440, which selects either the control signal output from the unit 410 or the control signal output from the synchronous rectification control unit 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 stepping down the boost voltage Vbst.
[0055]
The logic power supply unit 440 includes a resistor voltage dividing circuit that generates a desired potential by dividing the boost voltage Vbst with resistors R21 and R22, and a buffer amplifier AMP that outputs a voltage at 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. When the power supply is cut off, the output from the synchronous rectification control unit 420 is selected instead of the output from the PWM control unit 410, and the coils U, V , W includes selectors SEL1 to SEL6.
[0056]
The synchronous rectification control unit 420 compares the two terminal voltages U, V, and W of the drive coils of the U phase, V phase, and W phase of the spindle motor that is a three-phase brushless motor. And AND gates G1 to G6 that receive a combination of the output signals of these comparators CMP1, CMP2, and CMP3 and their inverted signals, and detect the magnitude of the back electromotive voltage of the coil to flow through 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, the control is performed such that the power source Vcc side output transistor of the phase with the highest counter electromotive voltage and the ground side output transistor of the phase with the lowest back electromotive voltage are turned on to pass a current through the coil.
[0057]
FIG. 9 is a block diagram showing a configuration example of the entire hard disk device 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 shown in FIG. Is.
In FIG. 9, 310 is a spindle motor that rotates the magnetic disk 300, 320 is an arm having a magnetic head (including a write magnetic head and a read magnetic head) HD at the tip, and 330 is a carriage that rotatably holds the arm 320. The voice coil motor 340 moves the magnetic head by moving the carriage 330, and the motor driving 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. The voice coil motor 340 and the spindle motor 310 are servo-controlled so that the magnetic head seeks to a desired track and the relative speed of the magnetic head is 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 the drive current of the magnetic head HD. A hard disk 240 receives read data transmitted from the signal processing circuit 230 and performs error correction processing, or performs error correction coding 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 considering magnetic recording characteristics, and reads position information from the 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 the personal computer body via the interface controller 250. . A buffer cache memory 270 temporarily stores read data read from the magnetic disk at high speed. A system controller 260 comprising 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. The sector position and the like are calculated based on the address information.
[0061]
As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Not too long. For example, in the above-described embodiment, the power required after the power supply is cut off is extracted by synchronous rectification control of the output transistors M1 to M6 that drive the spindle motor. However, the output transistors M1 to M6 are not subjected to the synchronous rectification control. The back electromotive force may be rectified by the body diode, or a rectifying diode bridge may be separately provided.
[0062]
In the embodiment, a lamp as a standby position is provided outside the disk and the magnetic head is retracted to the lamp when the power is cut off. However, a standby position is provided inside the disk and the magnetic head is turned off when the power is cut off. The present invention can also be applied to the case where the disk is retracted to the inside of the disk.
[0063]
In the above description, the case where the invention made mainly by the present inventor is applied to the hard disk storage device which is the field of use behind the invention has been described. However, the present invention is not limited to the present invention. Can be used.
[0064]
【The invention's effect】
The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
That is, in the magnetic disk storage device, the moving speed of the magnetic head when the power is cut off is detected, and the voice coil motor is controlled based on the moving speed and the target speed. It is possible to limit the back electromotive force generated by the voice coil motor when the power is cut off when the magnetic head is moved in the direction of the ramp outside the disk. Collisions can be prevented.
[0065]
Further, according to the present invention, in a magnetic disk storage device, a voice coil is generated with a voltage obtained by synchronously rectifying the back electromotive force of the spindle motor even when the power is cut off when the small motor with low back electromotive force or the spindle motor rotates slowly. The magnetic head can be securely retracted by driving the motor. As a result, a retract driver is not required, the chip size of the voice coil motor drive control IC can be reduced, and 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 spindle motor control system in a magnetic disk storage device according to the present invention.
FIG. 2 is a block diagram showing an 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 retract control of a voice coil motor when a power failure occurs.
FIG. 4 is a flowchart illustrating an example of a procedure for retract control of a voice coil motor when a power failure occurs by the retract control circuit according to the embodiment.
FIG. 5 is a timing chart showing signal timings of respective units at the time of 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 showing a more detailed configuration example of a coil drive circuit (VCM driver) constituting a drive control circuit of a 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 spindle motor drive control circuit;
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]
Driving coil of LVCM voice coil motor
Rsns Resistance for current detection
100 Motor drive control circuit (IC)
110 Spindle motor driver
120 Voice coil motor driver
121,122 Coil drive amplifier
123 Control amplifier
130 Retract Control Circuit
131 Sequencer
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 Head holding arm
330 Carriage
340 Voice coil motor
350 Head retraction position (lamp)

Claims (9)

A first motor for rotating the magnetic disk;
A magnetic head for reading information from a storage track on a magnetic disk rotated by the first motor;
A second motor for moving the magnetic head on the disk;
Includes a field effect transistor for controlling a current to be supplied to the second motor coil, a second motor drive circuit for moving the magnetic head in the normal operation by controlling the gate voltage of the transistor according to the first current command value,
A control circuit capable of generating a second current command value for the second motor drive circuit when the power is shut off; and a booster circuit capable of boosting a power supply voltage or a voltage obtained by rectifying a counter electromotive voltage generated in the coil of the first motor. Equipped,
The control circuit includes a register and a subtraction circuit,
The control circuit detects the moving speed of the magnetic head based on a counter electromotive voltage generated in the coil with the transistor turned off when the power is shut off, and holds a voltage value corresponding to the moving speed in the register. Then, a reference current that does not affect the moving speed of the magnetic head is supplied to the coil to detect the voltage across the coil, and the potential difference due to the parasitic resistance of the coil is determined from the value held in the register by the subtracting circuit. And the second current command value is generated so as to be a target speed, and the difference between the potential difference due to the parasitic resistance of the coil held in the register and the second current command value is generated. A value based on is supplied to the second motor drive circuit,
The second motor drive circuit is operated by the voltage boosted by the booster circuit, and controls the current flowing in the coil of the second motor according to the second current command value from the control circuit when the power is cut off. A magnetic disk storage system configured to move the disk to a predetermined standby position. The current command value is a digital value,
A D / A conversion circuit for converting the first or second current command value into an analog signal;
Switching means for supplying the D / A conversion circuit with the second current command value generated by the control circuit instead of the first current command value supplied from the outside during normal operation when the power is shut off;
The magnetic disk storage system according to claim 1, further comprising: A first motor drive control circuit for controlling rotation of the magnetic disk by controlling a drive current of the coil, including a transistor for passing a current to the coil of the first motor;
The first motor drive control circuit drives the transistor by a pulse width control method during normal operation,
3. The magnetic disk storage system according to claim 2, wherein when the power is shut off, the back electromotive force of the first motor is rectified by sequentially driving the transistors in synchronization with the rotation of the first motor. The control circuit includes a timer circuit,
When a predetermined time has elapsed after power-off, a signal instructing the first motor drive control circuit to stop the rotation of the first motor is sent.
4. The magnetic disk storage system according to claim 3 , wherein the first motor drive control circuit is configured to brake the rotation of the first motor in response to the instruction signal. The control circuit is
Voltage detecting means for detecting a voltage between terminals of the coil of the second motor;
An A / D conversion circuit for converting the voltage detected by the voltage detection means into a digital value;
An integration circuit for integrating the difference between the potential difference due to the parasitic resistance of the coil and the second current command 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 taking a difference between the output of the multiplication circuit and the output of the A / D conversion circuit;
A control loop including a second subtraction circuit for calculating a difference between the output of the first subtraction circuit and the second current command value;
By detecting the voltage across between the coil which the control loop is operating, the current the product of the potential difference amount with a predetermined value for the reference current due to the parasitic resistance which is held in the register by the first subtraction circuit parasitic resistance and potential difference due to obtain the value from the voltage across obtained by subtracting the voltage difference between the coil which the control loop is operating in,
Calculated value and the differences between the second current command value Ri preparative the second subtraction circuit, the result value obtained by integrating the above integrating circuit is supplied to the D / A conversion circuit coil of the second motor The magnetic disk storage system according to claim 2 , wherein the magnetic disk storage system is configured to control a current flowing through the disk. 6. The magnetic disk storage system according to claim 5 , wherein the integration circuit has a limiter function for limiting a maximum output. A first motor drive control circuit for controlling rotation of the magnetic disk by controlling a drive current of the coil, including a transistor for passing a current to the coil of the first motor;
The first motor drive control circuit includes:
During normal operation, the above transistors are driven by a pulse width control method.
7. The magnetic disk storage system according to claim 6, wherein when the power is cut off, the back electromotive force of the first motor is rectified by sequentially driving the transistors in synchronization with the rotation of the first motor. The control circuit includes a timer circuit,
When a predetermined time elapses after the limiter function is activated , a signal instructing the first motor drive control circuit to stop rotation of the first motor is sent to the first motor drive control circuit. 8. The magnetic disk storage system according to claim 7 , wherein the magnetic disk storage system is configured to brake the rotation of the first motor accordingly. A first motor for rotating the magnetic disk;
A magnetic head for reading information from a storage track on a magnetic disk rotated by the first motor;
A second motor for moving the magnetic head on the disk;
Includes a field effect transistor for controlling a current to be supplied to the second motor coil, a second motor drive circuit for moving the magnetic head in the normal operation by controlling the gate voltage of the transistor according to the first current command value,
A control circuit for generating a second current command value for the second motor drive circuit when the power is shut off;
A booster circuit for further boosting a voltage obtained by rectifying a power supply voltage or a back electromotive voltage generated in the coil of the first motor;
A system controller for generating the first current command value for giving a target value of a current to be passed through the coil of the second motor to the second motor drive circuit;
A voltage obtained by rectifying a counter electromotive voltage generated in the coil of the first motor when the power is shut off is boosted by the boosting circuit,
Operating the second motor driving circuit and the control circuit by the voltage boosted by the boosting circuit;
The control circuit detects the moving speed of the magnetic head based on a counter electromotive voltage generated in the coil with the transistor turned off when the power is shut off, and holds a voltage value corresponding to the moving speed in the register. Then, a reference current that does not affect the moving speed of the magnetic head is supplied to the coil to detect the voltage across the coil, and the potential difference due to the parasitic resistance of the coil is determined from the value held in the register by the subtracting circuit. And the second current command value is generated so as to be a target speed, and the difference between the potential difference due to the parasitic resistance of the coil held in the register and the second current command value is generated. Is supplied to the second motor drive circuit, and the current supplied to the coil of the second motor is controlled without the intervention of the system control device to control the magnetic force. Magnetic disk storage system characterized by moving the de to a predetermined standby position.

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