JP4199484B2 - Magnetic disk storage system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technology effective for application to control technology of a magnetic disk storage device and motor control when power supply is stopped such as 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 effective for use in head retraction control by a voice coil motor that moves a magnetic head for reading / writing information in the radial direction of a disk.
[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 a hard disk device, the magnetic head is configured to glide the disk surface with the wind pressure accompanying the rotation of the disk. When the disk rotation stops, the magnetic head may come into contact with the disk surface and damage it. .
[0003]
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 is performed. Therefore, when the head seek operation is started, it is necessary to move 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.
[0004]
[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. However, since the power supply of the control circuit for the voice coil motor is cut off when a power failure occurs, the motor cannot be driven and controlled.
Therefore, a driver for retracting (hereinafter referred to as a retract driver) is provided separately from a driver (hereinafter referred to as a VCM driver) for driving a voice coil motor for head seek, and the back electromotive force of the spindle motor is generated when a power failure occurs. 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).
[0005]
However, if a power failure occurs while moving the magnetic head in the ramp direction outside the disk, the motor will not be braked unless the counter electromotive force generated by the voice coil motor is suppressed. However, the retract driver according to the invention of the prior application is composed of a transistor that performs current source, and even if it can supply current, it cannot be pulled in, so that back electromotive force cannot be suppressed.
In addition, the voltage obtained by simply rectifying the back electromotive force of the spindle motor with a diode bridge causes a voltage drop corresponding to the forward voltage of the diode. Therefore, in the case of a small motor with a small back electromotive force of the spindle motor or the spindle motor rotating slowly. It became clear that there was a problem that sometimes the revocation driver could not be operated sufficiently.
[0006]
An object of the present invention is to provide a control technique for a voice coil motor that can safely and promptly retract a magnetic head when power supply is stopped 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 supply is stopped when the magnetic head is moved in the ramp direction outside the disk in the magnetic disk storage device. Thus, it is an object of the present invention to provide a control technique for a voice coil motor capable of preventing a magnetic head from colliding with a ramp by applying a brake.
Still another object of the present invention is to provide a back electromotive force of the spindle motor in a magnetic disk storage device even when the spindle motor is a small motor having a small counter electromotive force or when the power supply is stopped when the spindle motor is slow in rotation. An object of the present invention is to provide a voice coil motor control technique capable of driving a voice coil motor with a voltage obtained by rectifying electric power to retract a magnetic head.
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 control circuit for controlling the movement of the magnetic head by controlling the drive current of the voice coil motor, and a voltage for driving a field effect transistor for passing a current through the coil of the voice coil motor In a magnetic disk storage device having a booster circuit for generating a voltage, when the supply of power is stopped, a voltage obtained by rectifying a counter electromotive voltage generated in the coil of the spindle motor is boosted by the booster circuit, and the booster circuit The voice coil motor drive control circuit is controlled by the boosted voltage. By work is obtained so as to drive and control the transistor to flow a current to the coil of the voice coil motor.
[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 supply of power is stopped without providing a power backup means. The magnetic head can be safely retracted when In addition, when the power supply is cut off, the booster circuit is operated and the voice coil motor drive control circuit is operated by the boosted voltage to drive and control the MOS transistor that supplies current to the coil of the voice coil motor. In addition, a current can be passed through the coil of the voice coil motor, whereby the magnetic head can be retracted to a predetermined standby position. In addition, even in the case of a small motor with a small back electromotive force of the first motor, the voice coil motor drive control 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 supply is stopped when moving toward the standby position to operate the voice coil motor drive control circuit, the current generated by the back electromotive force generated in the coil of the voice coil motor is used for driving. This can be sucked by the MOS transistor, thereby braking the voice coil motor and preventing the reliability of the magnetic head from colliding with the lamp at the retracted position.
[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 A motorized circuit 100 that is circuitized, a signal processing circuit 230 that drives the magnetic head HD to perform writing on the magnetic disk 300 and detects position information based on a read signal, and controls the operation of the entire magnetic disk storage device. Head position command information (track position) output Controller 260, and a compensation based on the position command information from the controller 260 and the position information (servo signal) detected by the signal processing circuit 230 to send a value corresponding to the difference to the motor drive circuit 100 as a drive current command value. 280, etc. A ramp 350 supports the arm 320 disposed outside the magnetic disk 300 and retracted.
[0011]
The controller 260 is composed of a microcomputer (CPU) or the like. 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 booster circuit 140 that boosts the power supply voltage are provided. The motor drive circuit 100 further includes a D / A converter 150 that converts a drive current command value in digital data format supplied from the compensator 280 into an analog drive current command value, and a power source that detects the occurrence of a power failure. A monitor circuit 160 is provided.
[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]
The output of the control amplifier 123 is configured to be input to the coil drive amplifiers 121 and 122 through the switch SW1, and during normal operation, the output of the control amplifier 123 is input to the coil drive amplifier through the switch SW1. 121 and 122. When a power failure occurs, the switch SW1 is switched to control the VCM driver 120 to brake the voice coil motor 340 and to retract the magnetic head, and the output Vret of the retract control circuit 130 is the coil drive amplifier. 121 and 122.
[0014]
The retract control circuit 130 includes a timer counter 131, a constant current source 132, a current-voltage conversion resistor 133, and the like. The constant current source 132 is configured so that the current can be switched in two stages. In addition, the timer counter 131 starts timing operation at the same time as the occurrence of a power failure, and after a predetermined time, switches the current of the constant current source 132 to increase. As a result, when a predetermined time elapses after the occurrence of the power failure, the voltage Vret converted and output by the resistor 133 is changed stepwise.
[0015]
The time measured by the timer counter 131 takes into account the time required for the magnetic head to move from the innermost to the outer ramp position of the magnetic disk. In addition, the output voltage Vret supplied to the VCM driver 120 is increased after a predetermined time has elapsed because a larger driving force is required when the ramp is raised than when the magnetic head is moved on the disk. It is.
[0016]
In FIG. 2, 140 is a booster circuit that boosts the power supply voltage Vcc, and 145 is an oscillator that generates an operation clock φc of the booster circuit 140. For example, as shown in FIG. 7, the booster circuit 140 includes a charge storage capacitive element C2, a switch S1 connected between one terminal of the capacitive element C2 and the power supply voltage terminal Vcc (Vspn), and a capacitive element C2. A switch S2 that switches the voltage applied to the other terminal between the ground potential and the power supply voltage Vcc (Vspn), and a directional charge such as a MOSFET that acts as a diode that transfers the charge charged in the capacitor C2 in one direction. It is composed of a circuit called a charge pump comprising transfer means QTM and the like, and when a power failure occurs, it operates with a back electromotive force Vspn of a spindle motor described later and boosts Vspn to a voltage about 5V higher than that.
[0017]
FIG. 7 shows the principle of a known charge pump, which is slightly different from an actual circuit. Since various types of charge pumps have been proposed, specific circuit examples and description of operations are omitted. The charge storage capacitance element C2 has a capacitance value of about 1/10 of the smoothing capacitance C1. In this embodiment, since the charge storage capacitor element C2 has a capacitance value of about 0.2 μF, external capacitor elements are used for the charge storage capacitor element C2 and the smoothing capacitor C1.
[0018]
The boost voltage Vbst boosted by the booster 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 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.
[0019]
In this embodiment, the oscillator 145 is configured to be operated by the boost voltage Vbst boosted by the booster 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 booster circuit 140, but when the boost voltage Vbst is used, the power voltage Vcc is switched to the back electromotive force Vspn when the power failure occurs. 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.
[0020]
The timer counter 131 of the retract control circuit 130 is not particularly limited, but is counted by a clock φc that boosts the booster circuit 140 generated by the oscillator 145. The power supply voltage of the timer counter 131 uses the boost voltage Vbst in order to ensure a stable operation. On the other hand, the power source of the constant current source 132 uses a voltage Vspn obtained by rectifying the counter electromotive force of the spindle motor in order to suppress the consumption of the electric charge accumulated in the smoothing capacitor C1.
[0021]
For example, as shown in FIG. 8, the constant current source 132 of the retract control circuit 130 includes two current sources CI1 and CI2 and a switch element SW0 connected in series with one current source CI1. Turns off the switch SW0 and causes the current of one current source CI2 to flow through the resistor 133. When a predetermined time has elapsed since the occurrence of a power failure, the switch SW0 is turned on by the output of the timer counter 131 and the current of the other current source CI1 is also added. Thus, the current can be increased by flowing it through the resistor 133, and the voltage Vret converted by the resistor 133 can be changed.
[0022]
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 booster circuit 140.
[0023]
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.
[0024]
In this embodiment, each of the output transistors M1 to M6 is composed of an N channel type MOSFET, and body diodes D1 to D6 parasitic between the source and drain thereof are used as coils Lu, Lv, The counter electromotive voltage generated in Lw is rectified to operate as a rectifier circuit that supplies power to the spindle motor driver circuit 110, the VCM driver circuit 120 that drives the voice coil motor 340, the retract control circuit 130, and the booster circuit 140. It is configured as follows.
[0025]
Next, a specific operation of the voice coil motor drive circuit shown in FIG. 2 when a power failure occurs will be described with reference to the timing chart of FIG. FIG. 3 shows a situation where a power failure occurs while the magnetic head is moving 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.
[0026]
When the master power supply (Vcc) drops due to a power failure or the like, the output of the power supply monitor circuit 160 changes to a low level and the power switch is turned off (timing t1). Then, the voltage Vspn obtained by rectifying the counter electromotive voltage generated in the coils Lu, Lv, and Lw of the spindle motor is supplied to the VCM driver circuit 120, the retract control circuit 130, and the booster circuit 140. Further, since the booster voltage Vbst is held by the smoothing capacitor C1, the booster circuit 140 and the oscillator 145 continue to operate even after the power is turned off, and the booster voltage Vbst is generated. Further, since the spindle driver circuit performs synchronous rectification control by generating Vbst, Vspn is lower than the power supply voltage Vcc by the voltage drop VR due to the ON resistance of the output transistor.
[0027]
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 is used instead of the output of the DA converter (DAC) 150. Is supplied to the VCM driver circuit 120. As a result, the voltage of the coil terminal P1 (VCMP terminal) is lowered. Then, a reverse current tends to flow through the coil due to the back electromotive force BEMF generated in the coil LVCM. Since this reverse current is absorbed by the power MOSFET M8 of the VCM driver circuit 120, the reverse current flows through the coil and the voice coil motor 340 is braked.
[0028]
In the head retracting method using the conventional retract driver, when the retract driver is composed of a source follower type MOSFET, current cannot be drawn, so the magnetic head is moving from the inside to the outside of the disk. When a power failure occurs, the voice coil motor is not braked and the magnetic head may collide with the lamp. However, in this embodiment, since the reverse current of the coil can be drawn by the VCM driver circuit 120 as described above, the voice coil motor 340 can be braked, and the magnetic head can collide with the lamp. It can be avoided.
[0029]
Further, in the present embodiment, when a power failure occurs and the input to the VCM driver circuit 120 is switched from the DAC output to the voltage Vret from the retract control circuit 130, a predetermined time elapses, so that Vret increases. (Timing t2). As a result, the current passed through the coil LVCM of the voice coil motor by the VCM driver circuit 120 is increased, so that the magnetic head can move up the ramp slope and reach the standby position (timing t3). When a predetermined time sufficiently longer than the time required for the head to raise the lamp elapses, for example, the spindle-side transistors M2, M4, and M6 among the drive transistors M1 to M6 of the spindle motor are turned on to turn on the spindle. The motor is braked, and 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 booster circuit 140 are dropped (timing t4).
[0030]
FIG. 4 shows an embodiment of the VCM driver 120 described above. In FIG. 4, the voice coil motor 340 is represented as an equivalent circuit including a coil inductance Lvcm, an internal resistance Rvcm, and a counter electromotive voltage source Vbemf.
As shown in FIG. 4, the VCM driver circuit 120 includes power drive MOSFETs M7, M8, M9, and M10 that drive current to the coils, coil drive amplifiers 121 and 122, and the 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).
[0031]
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.
[0032]
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 Vcc as a power source, and the operation of the amplifier is stopped when a power failure occurs. However, at this time, the switch SW1 is switched, and the voltage Vret from the retract control circuit 130 is supplied to the coil drive amplifiers 121 and 122 in place of the output voltages of the amplifiers 231 and 232.
[0033]
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.
[0034]
FIG. 5 shows a specific circuit configuration example of the output amplifier 210 (220) in the circuit shown in FIG.
As shown in FIG. 5, 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, and the differential amplifier 211. 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.
[0035]
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.
[0036]
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. 5 will be described.
As shown in FIG. 5, 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.
[0037]
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.
[0038]
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.
[0039]
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.
[0040]
In the circuit of FIG. 5, the gate-source voltage of the output transistor M7 is increased by, for example, appropriately 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. 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.
[0041]
FIG. 6 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. 6, 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.
[0042]
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.
[0043]
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 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.
[0044]
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.
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
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 embodiment, the power required after the power supply is cut off is obtained by rectifying the back electromotive force of the spindle motor with the body diodes of the output transistors M1 to M6. May be provided separately.
[0049]
In the embodiment, the booster circuit that generates a voltage for driving the MOS transistor that supplies current to the coil of the voice coil motor during normal operation is also operated when the power is shut off. It is also possible to provide a booster circuit that generates the power supply voltage for the driver that drives the voice coil motor by boosting the voltage obtained by rectifying the electric power, separately from the booster circuit that generates the power supply voltage for the driver during normal operation. is there. 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.
[0050]
Further, in the embodiment, the motor drive control circuit 100 alone performs the retracting operation of the magnetic head when the power is shut off, but means for backing up the controller 260 that supplies the motor drive control circuit 100 with a current command value. It is also possible to provide a configuration in which the magnetic head is retracted by driving the voice coil motor 340 in response to a command from the controller 260 when the power is shut off.
[0051]
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 it, has been described. However, the present invention is not limited to the present invention. Can be used.
[0052]
【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, when the power supply is stopped, the magnetic head can be safely and promptly retracted, and the magnetic head is powered when the magnetic head is moved in the ramp direction outside the disk. When the supply is stopped, the counter electromotive force generated by the voice coil motor is limited and the brake is applied to prevent the magnetic head from colliding with the lamp. Further, according to the present invention, in the magnetic disk storage device, even when the power supply is stopped when the small motor with low back electromotive force or the spindle motor is slow to rotate, the back electromotive force of the spindle motor is synchronously rectified. An effect is obtained that the voice head can be reliably retracted by driving the voice coil motor.
[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 timing chart illustrating signal timings of respective units during voice coil motor retraction control when a power failure occurs by the motor drive control circuit of the embodiment.
FIG. 4 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. 5 is a block diagram showing a specific example of an output amplifier constituting a coil drive circuit (VCM driver).
FIG. 6 is a block diagram showing a more detailed configuration example of a spindle motor drive control circuit.
FIG. 7 is a circuit configuration diagram showing the principle of a charge pump circuit as a boost circuit.
FIG. 8 is a circuit configuration diagram showing a more detailed configuration example of a retract 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]
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 Retract control circuit 140 Booster 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 (5)

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;
A second motor drive control circuit that includes a field effect transistor for passing a current to the coil of the second motor and controls the movement of the magnetic head by controlling the drive current of the coil;
A booster circuit for generating a voltage for driving the transistor,
When the supply of power to the magnetic disk storage system is stopped, a voltage obtained by rectifying the back electromotive voltage generated in the coil of the first motor is boosted by the booster circuit, and the second motor is boosted by the voltage boosted by the booster circuit. The drive control circuit is operated to drive and control the transistor that supplies current to the coil of the second motor to move the magnetic head to a predetermined standby position.
The booster circuit is a charge pump circuit that performs a boost operation by a clock signal, and includes a clock generation circuit that operates by a voltage boosted by the charge pump circuit to generate the clock signal.
Current detection means for detecting a current flowing in the coil of the second motor;
The second motor drive control circuit has a control amplifier that compares the target current value signal and the current value detected by the current detection means, and outputs a signal corresponding to the difference,
A predetermined control voltage is supplied instead of the output of the control amplifier when the power is shut off,
The control voltage can be switched between a first level and a second level higher than the first level. When the power is shut off, the first level control voltage is supplied, and then the second level control voltage is supplied. Configured to
A timer circuit for measuring a time during which the control voltage of the first level is supplied ;
The magnetic disk storage system according to claim 1, wherein the timer circuit measures a time during which the control voltage of the first level is supplied by the clock signal generated by the clock generation circuit. 2. The magnetic disk storage system according to claim 1, wherein the timer circuit is operated by a voltage boosted by the booster circuit. A voltage generation circuit for generating the first level control voltage and the second level control voltage;
The voltage generation circuit includes a constant current source and a resistance element that converts a current supplied from the constant current source into a voltage, and is configured to be able to switch a magnitude of a current flowing through the constant current source. 3. The magnetic disk storage system according to claim 1, wherein the magnetic disk storage system is a magnetic disk storage system. The voltage generation circuit includes a first constant current source, a second constant current source, and a switch element provided between any one of the constant current sources and the resistance element. 4. The magnetic disk storage system according to claim 3, wherein the magnetic disk storage system is configured to be on / off controlled by a signal from the timer circuit . 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;
2. The first motor drive control circuit drives the transistors by a pulse width control method during normal operation, and sequentially drives the transistors in synchronization with rotation of the first motor when power is shut off. A magnetic disk storage system according to any one of claims 1 to 4 .

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