JP3825441B2 - Magnetic disk unit - Google Patents

Description

  The present invention relates to a magnetic disk device, and more particularly, to an auto retract function for urgently retracting a magnetic head when power supply from a power source cannot be received due to a power failure or the like during operation.

There is a situation in which the magnetic disk device cannot receive power supply from the power supply unexpectedly due to, for example, a user's erroneous operation or power failure during the operation. At this time, the magnetic disk device must urgently retract the magnetic head in order to avoid contact between the magnetic head and the magnetic disk. However, since there is no power supply from the power source during retraction, power supply to the actuator that drives the magnetic head becomes a problem. (Hereinafter, the situation in which the magnetic disk device cannot receive power supply from the power supply and urgently retreats the magnetic head is referred to as "at the time of retraction." Called "time".)
Patent Document 1 discloses a technique for supplying an induced electric power generated in a motor that rotationally drives a magnetic disk to an actuator during retraction. This utilizes the fact that the motor functions as a generator at that time because the magnetic disk continues to rotate for a while due to the inertial force even when the power supply from the power supply is lost.

FIG. 1 is a diagram showing a configuration of a magnetic disk device disclosed in Patent Document 1. As shown in FIG.
The spindle motor 51 is a three-phase AC motor that rotationally drives a magnetic disk. The SPM drive circuit 52 supplies drive power to the spindle motor 51.
The voice coil motor 76 is a kind of actuator that drives a magnetic head. The voice coil motor 76 receives power supply from the VCM drive circuit 71 when normal, and receives power supply from the spindle motor 51 when retracted. The switching of the power supply source is performed by the switching circuit 53 switching the switches 78 and 79.

The rectifier circuit 75 is a circuit that rectifies three-phase AC induced power generated in the spindle motor 51. Each switch provided in the rectifier circuit 75 is ON / OFF controlled by the control circuit 77.
The voltage of each phase of the induced power shows a waveform close to a sine wave, and the phase is different by 120 degrees in terms of electrical angle. That is, among the three phases, the phase with the maximum voltage changes with time. Therefore, the maximum detection circuit 72 controls each of the switches 65, 66, and 67 so that only the switch of the phase with the maximum induced power voltage is turned on in order to efficiently rectify. In addition, the minimum detection circuit 73 controls each switch so that only the switch of the phase with the minimum induced power voltage among the switches 68, 69, and 70 is turned on.

Thus, the magnetic disk device can rectify the induced power generated in the spindle motor 51 and supply it to the voice coil motor 76.
On the other hand, in recent years, magnetic disk devices have been increasingly miniaturized, and accordingly, there has been a demand for miniaturization of semiconductor chips on which the above-described circuits are integrated. In the magnetic disk apparatus shown in FIG. 1, when the switches 78 and 79 are integrated in a semiconductor chip, a total of four power transistors are required. The power transistor has a large volume per unit for handling a large current, and the smaller the number, the smaller the semiconductor chip. Therefore, the inventor of the present application examined reference examples shown below in the course of development.

FIG. 2 is a diagram showing a configuration of a magnetic disk device of a reference example.
In the magnetic disk apparatus shown in FIG. 2, a terminal 58 that is an output terminal of the rectifier circuit 75 and a power input terminal of the VCM drive circuit 71 are connected, and a switch 57 is provided between the terminal 58 and the power source.
The magnetic disk device supplies power to the VCM drive circuit 71 by turning on the switch 57 when it is normal and turning off the switch 57 when retreating. With such a configuration, the number of power transistors (corresponding to the switch 57) used for switching the power supply source can be reduced to one.
JP 2001-307408 A

However, although the magnetic disk device can satisfy the demand for downsizing of the semiconductor chip, the following problems are newly generated.
The maximum detection circuit 72 does not operate when it is normal, and performs on / off control of the switches 65, 66, and 67 when it is retracted. The reason why the motor does not operate normally is that if any of the switches 65, 66, and 67 is turned on, the DC voltage of the power source is applied to the spindle motor 51, and normal driving of the spindle motor 51 is hindered. It is. At the time of retraction, the induced power of the spindle motor 51 is used for on / off control of the switches 65, 66, and 67. Usually, since the voltage of the induced power is relatively low, it can be considered that the voltage is boosted and the switch is turned on / off in order to make the switch fully conductive.

However, since the capacitor needs to be charged first for boosting, on / off control with a sufficiently boosted voltage cannot be expected immediately after the operation of the maximum detection circuit 72 starts. Therefore, it has become difficult to design the magnetic head so that the retracting of the magnetic head is completed reliably under a situation where the induced electric power is decreasing due to the miniaturization of the magnetic disk device.
An object of the present invention is to provide a technique capable of completing the retraction of a magnetic head even in a situation where induced power is decreasing due to downsizing of a magnetic disk device.

A magnetic disk device according to the present invention is a magnetic disk device having an auto retract function, wherein a determination circuit for monitoring a power supply voltage to determine whether or not a predetermined value or less, a coil of a motor for rotating the magnetic disk, is provided on the wiring connecting the actuator for driving the magnetic head, and a switching element for switching an oN state and an oFF state in response to the voltage applied to the control input terminal, the control of the actuators and the switching element is provided on the wiring connecting the input terminal, a control input of the switching element by boosting the voltage that will be supplied to the actuator via the switching element when said determination circuit determines that less than a predetermined value A booster circuit for obtaining a voltage to be supplied to the terminal, and when the determination circuit determines that the voltage is less than a predetermined value, By the ON state by applying a voltage obtained by the boosting circuit control input terminal, and a switch control means for supplying the induced electric power generated in the motor to the actuator.

According to the above configuration, in the magnetic disk device, when the power supply voltage becomes a predetermined value or less, the booster circuit has already boosted the voltage supplied to the actuator. Here, the voltage supplied to the actuator is a power supply voltage if the power supply voltage is not lower than a predetermined value, and is an induced power voltage if the power supply voltage is lower than a predetermined value.
Thus, the magnetic disk device can drive the switch element with the output voltage of the booster circuit immediately after determining that the magnetic disk needs to be evacuated, so that the induced power can be efficiently supplied to the actuator. Therefore, the magnetic disk device can complete the retraction of the magnetic head even if the induced power is small.

  The booster circuit includes a capacitor having a first electrode and a second electrode, a clock generation circuit that generates a clock signal that repeats a high level and a low level at a predetermined cycle, and outputs the clock signal to the first electrode, the clock A step-up control circuit that inputs a voltage supplied to the actuator to the second electrode when a signal is at a low level and outputs a voltage at the second electrode when the clock signal is at a high level. Also good.

According to the above configuration, the magnetic disk apparatus employs a so-called charge pump type booster circuit.
For example, if the high level of the clock signal is the voltage supplied to the actuator and the low level is the ground voltage, the booster circuit can boost the voltage supplied to the actuator by about twice. In this case, if the voltage for fully conducting the transistor is about 5 volts, the magnetic disk device efficiently supplies the induced power to the actuator until the induced power drops to about 2.5 volts. Can do. Therefore, the magnetic disk device can complete the retraction of the magnetic head even if the induced power is small.

In the clock generation circuit, an odd number of three or more inverters are connected in cascade, and the output voltage of the last-stage inverter is output as a clock signal, and the output voltage is input as the input voltage of the first-stage inverter. It may be a ring oscillator.
According to the above configuration, the booster circuit employs a ring oscillator as the clock generation device. Since the ring oscillator has a very simple circuit configuration and does not require a bias circuit, the ring oscillator can stably generate a clock signal even at an extremely low voltage (for example, less than 1 volt).

Thus, the magnetic disk device can operate the booster circuit stably even when the induced power is low.
The switch element is a MOS (Metal Oxide Semiconductor) type transistor, the source of the transistor is connected to the motor side, the drain is connected to the actuator side, and the switch control means is configured such that the determination circuit has a predetermined value or less. When the output voltage is applied to the gate of the transistor, the drain and the source are made conductive, and when the determination circuit does not determine a predetermined value or less, the output voltage is not applied to the gate of the transistor. It is good also as not conducting between sources.

According to the above configuration, the magnetic disk device can achieve integration and power saving of the switch element in the semiconductor chip.
A magnetic disk device according to the present invention is a magnetic disk device having an auto retract function, wherein a determination circuit for monitoring a power supply voltage to determine whether or not a predetermined value or less, a coil of a motor for rotating the magnetic disk, When the switch element provided on the wiring connecting the power supply terminal of the actuator that drives the magnetic head and the determination circuit determines that the value is not more than a predetermined value, the voltage on the motor side of the switch element is greater than the voltage on the actuator side. In the case where the switch element is turned on, the induced power generated in the magnetic disk is supplied to the actuator, and the motor side voltage of the switch element is lower than the actuator side voltage. Switch control means for turning the switch element off.

  According to the above configuration, the magnetic disk device supplies induced power to the actuator when the voltage on the motor side is higher than the voltage on the actuator side during retraction. As a result, the magnetic head is retracted. Conversely, if the voltage on the actuator side is higher than the voltage on the motor side, the magnetic disk device turns off the transistor. As a result, the magnetic disk device prevents the power on the actuator side from flowing back to the motor side, and does not hinder the normal rotation of the motor.

  This means that even if the power supply voltage is temporarily restored due to chattering, the power supply voltage is not applied to the motor side, so that the rotation stoppage of the motor is not accelerated. Therefore, when chattering stops and the power supply voltage becomes zero again, the magnetic disk device can supply the induced power to the actuator again and continue the retraction of the magnetic head.

  Further, the power source is a DC power source, the motor is a three-phase AC motor, the switch element is provided in each phase between the three-phase AC motor and the actuator, and the switch When the motor side voltage of any one of the switch elements is higher than the actuator side voltage, the control means selectively turns on each switch element to thereby turn on the three-phase alternating current. The induced power of the three-phase AC generated in the motor is rectified and supplied to the actuator. When the voltage on the motor side of all the switch elements is lower than the voltage on the actuator side, all the switch elements are turned off. It is good as well.

According to the above configuration, the magnetic disk device can rectify the three-phase AC induced power and supply it to the actuator by selectively turning on each transistor.
Further, the switch control means detects a motor-side voltage and an actuator-side voltage for each of the switch elements, and is specified with a specifying circuit that specifies a location indicating the maximum voltage among the detected voltages. If the selected part is on the motor side of any switch element, turn on only that switch element. If the specified part is on the actuator side of any switch element, turn off all switch elements. And a control circuit.

  The induced power of the motor is three-phase alternating current, so the phase where the voltage is maximum changes periodically. The magnetic disk device having the above configuration can efficiently rectify the induced power by turning on only the transistor having the phase of the maximum induced power voltage. Further, when the power supply voltage is temporarily restored by chattering, the voltage on the actuator side becomes high, so that the magnetic disk device can detect it and turn off all the transistors.

  Further, the switch control means determines that the motor side voltage is higher than the actuator side voltage by the comparison circuit comparing the motor side voltage and the actuator side voltage for each of the switch elements. And a control circuit that turns off the switch element that has been determined that the voltage on the motor side is lower than the voltage on the actuator side.

  The induced power of the motor is three-phase alternating current, so the phase where the voltage is maximum changes periodically. The magnetic disk device having the above configuration can efficiently rectify the induced power by turning on a transistor whose voltage on the motor side is higher than that on the actuator side. When the power supply voltage is temporarily restored by chattering, the voltage on the actuator side becomes higher than the voltage on the motor side, so that all transistors are turned off.

  The magnetic disk device further includes a booster circuit that boosts a voltage supplied to the actuator, the switch element is a MOS (Metal Oxide Semiconductor) type transistor, and the source of the transistor is on the motor side. In addition, the drains are respectively connected to the actuator side, and when the drain voltage of the transistor is lower than the source voltage, the switch control means applies the output voltage of the booster circuit to the gate of the transistor. When the source is made conductive and the drain voltage is higher than the source voltage, the drain-source may not be made conductive by not applying the output voltage of the booster circuit to the gate of the transistor.

According to the above configuration, the magnetic disk device can achieve integration and power saving of the switch element in the semiconductor chip.
The switch control means further supplies power from the power source to the motor by turning on the switch element when the determination circuit does not determine that the value is equal to or less than a predetermined value. May be driven to rotate.

According to the above configuration, the magnetic disk device can supply power from the power supply to the motor through the transistor when the power supply voltage is not determined to be equal to or lower than the predetermined value. In other words, the transistor fulfills two functions of supplying power from the power source to the motor when normal and supplying induced power from the motor to the actuator when retracting.
In this manner, the magnetic disk device can reduce the size of the entire circuit by sharing the transistor.

The power source is a DC power source, and the motor is a three-phase AC motor.
The switch element is provided in each phase between the three-phase AC motor and the actuator, and the switch control means selectively turns on one of the switch elements. By doing so, it is good also as converting the electric power of the said DC power supply into the electric power of a three-phase alternating current, and supplying to the said three-phase alternating current motor.

  According to the above configuration, the magnetic disk device can convert the power from the DC power source into the three-phase AC and supply it to the motor by selectively turning on each transistor.

(Embodiment 1)
<Overview>
The magnetic disk device according to the first embodiment completes charging of the capacitor by operating the booster circuit even during normal operation. Therefore, even when power supply cannot be received, the booster circuit can immediately apply the boosted voltage to the switch element in the rectifier circuit. As a result, the magnetic disk device can immediately start the operation of retracting the magnetic head.

<Overall configuration of magnetic disk device>
FIG. 3 is a diagram showing the configuration of the magnetic disk apparatus according to the present invention.
The magnetic disk device includes a spindle motor 1, an SPM drive circuit 2, a voice coil motor 26, a VCM drive circuit 21, a determination circuit 3, a switch element 7, a rectifier circuit 25, and a control circuit 27. The magnetic disk device operates by receiving power supply from a DC power source when it is normal.

The spindle motor 1 is a three-phase AC motor that rotationally drives a magnetic disk, and includes three motor coils 1a, 1b, and 1c. Terminals 4, 5, and 6 are U-phase, V-phase, and W-phase terminals, respectively.
The SPM drive circuit 2 is a circuit for driving the spindle motor 1, and converts the power of the DC power source from DC to three-phase AC and supplies it to the spindle motor 1 when it is normal.

The voice coil motor 26 is a kind of actuator used for positioning the magnetic head, and is driven by electric power supplied to a power supply terminal.
The VCM drive circuit 21 is a circuit that drives the voice coil motor 26.
The determination circuit 3 monitors the power supply voltage VCC and determines whether or not it is necessary to retreat based on whether or not it is equal to or less than a predetermined value. If it is determined that the value is equal to or less than a predetermined value, that is, it is necessary to save, the SPM drive circuit 2, the switch element 7, and the control circuit 27 are notified of this. Here, for the notification, for example, a signal voltage that is at a high level during normal operation and at a low level during saving is used. Further, it is assumed that a holding circuit is built in the determination circuit 3 so that once the signal voltage becomes low level, even if the power supply voltage is restored, it does not become high level unless the magnetic head is completely retracted.

The switch element 7 is turned on when the signal voltage from the determination circuit 3 is at a high level, and is turned off when the signal voltage is at a low level. The switch element 7 is a double diffused MOS transistor, and the attached diode 7a is a body diode that is structurally provided in the double diffused MOS transistor.
The rectifier circuit 25 rectifies the three-phase AC induced power generated in the spindle motor 1 during retraction and supplies the rectified circuit to the VCM drive circuit 21. The rectifier circuit 25 includes switch elements 15 to 20 inside. Each switch element is a double diffusion type MOS transistor, and includes a body diode.

The switch elements 15, 16, and 17 have one end commonly connected to the output terminal 8 and the other end connected to the terminals 4, 5, and 6, respectively. These switch elements are controlled to be turned on and off by the maximum detection circuit 22.
The switch elements 18, 19, and 20 have one end connected in common to the ground terminal 24 and the other end connected to the terminals 4, 5, and 6, respectively. These switch elements are controlled to be turned on and off by the minimum detection circuit 23.

  The control circuit 27 controls the on / off state of each switch element in the rectifier circuit 25. Specifically, all switch elements in the rectifier circuit 25 are turned off during normal operation, and each switch element is selectively turned on so as to rectify the induced power of the spindle motor 1 during retraction. Here, whether it is normal or evacuation is determined by the signal voltage from the determination circuit 3. The control circuit 27 includes a maximum detection circuit 22 and a minimum detection circuit 23 in order to efficiently rectify the induced power to the rectification circuit 25 at the time of saving.

  The maximum detection circuit 22 monitors U-phase, V-phase, and W-phase voltages, and switches on the phase with the maximum voltage among the switch elements 15, 16, and 17 provided for each phase. And The minimum detection circuit 23 monitors U-phase, V-phase, and W-phase voltages, and selects the switch with the minimum voltage among the switch elements 18, 19, and 20 provided for each phase. Turn on.

As a result, the VCM drive circuit 21 can receive power supply from the power source when normal, and can receive induced power from the spindle motor 1 when retracted.
Hereinafter, the maximum detection circuit 22 which is a characteristic part of the present invention will be described in detail.
<Maximum detection circuit>
FIG. 4 is a diagram showing a configuration of the maximum detection circuit 22.

The maximum detection circuit 22 includes a booster circuit 28, a switch element 29, a constant current source I1, resistors R1 to R3, and transistors Q1 to Q6.
The booster circuit 28 boosts the voltage V8 at the terminal 8. The voltage V8 is equal to the voltage supplied to the VCM drive circuit 21. That is, it is substantially equal to the power supply voltage VCC in the normal state and equal to a voltage obtained by rectifying the induced power of the spindle motor 1 at the time of retraction.

  In order to efficiently use the induced power at the time of evacuation, it is important to completely switch the switch elements 15, 16, and 17. For this purpose, a voltage of about 5 volts needs to be applied to the gate of each switch element. However, the voltage of the induced power is only about 2 to 3 volts at most. Accordingly, the maximum detection circuit 22 applies the voltage boosted by the booster circuit 28 to the switch elements 15, 16, and 17 so that each switch is completely turned on.

The constant current source I1 is a circuit for flowing a constant current.
According to the signal voltage from the determination circuit 3, the switch element 29 is turned off when normal and turned on when retracted. When the switch element 29 is turned on, a constant current flows through the transistors Q4, Q5, and Q6, so that the maximum detection circuit 22 starts operating. If the constant current source I1 has a switch function, the operation of the maximum detection circuit 22 may be started using the switch function of the constant current source I1 instead of the switch element 29. In that case, the switch element 29 can be omitted.

The resistors R1, R2, and R3 are all resistors having the same resistance value.
The transistors Q1, Q2, and Q3 are all MOS transistors having similar electrical characteristics. The transistors Q1, Q2, and Q3 have sources connected to the booster circuit 28 in common and drains connected to the gates of the switch elements 15, 16, and 17, respectively. Resistors R1, R2, and R3 are interposed between the gates and sources of the transistors Q1, Q2, and Q3, respectively.

The transistors Q4, Q5, and Q6 are all bipolar transistors having similar electrical characteristics.
The transistors Q4, Q5, and Q6 have collectors connected to the gates of the transistors Q1, Q2, and Q3, respectively, and emitters commonly connected to the switch element 29. The bases of the transistors Q4, Q5, and Q6 are connected to terminals 4, 5, and 6, respectively.

The operation of the maximum detection circuit 22 having the above configuration will be described separately for the normal time and the save time.
When normal, the voltage V8 at the terminal 8 is substantially the power supply voltage VCC. The booster circuit 28 boosts the power supply voltage VCC and supplies it to the sources of the transistors Q1, Q2, and Q3.
In the normal state, the signal voltage from the determination circuit 3 is at a high level, and the switch element 29 is in an OFF state accordingly. Accordingly, the collector currents of the transistors Q4, Q5, and Q6 are all zero.

Since the collector currents of the transistors Q4, Q5, and Q6 are all zero, the gate voltages of the transistors Q1, Q2, and Q3 are equal to the source voltage, and the transistors Q1, Q2, and Q3 are all turned off.
As a result, since the gates of the switch elements 15, 16, and 17 are all at the low level, the switch elements 15, 16, and 17 are all turned off.

On the other hand, at the time of evacuation, the voltage V8 is a voltage obtained by rectifying the induced power of the spindle motor 1 by the switch elements 15, 16, and 17. The booster circuit 28 boosts the voltage V8 and supplies it to the sources of the transistors Q1, Q2, and Q3.
At the time of saving, the signal voltage from the determination circuit 3 becomes low level, and the switch element 29 is turned on accordingly. Therefore, transistors Q4, Q5, Q6 are driven. Among the transistors Q4, Q5, and Q6, only the transistor having the maximum base voltage is turned on.

  Since the induced electric power of the spindle motor 1 is a three-phase alternating current, the voltage waveform of each phase differs in phase by 120 degrees as an electrical angle. Accordingly, the voltage V4 at the terminal 4 becomes maximum in a certain time zone, and the terminal having the maximum voltage periodically changes such that the voltage V5 at the terminal 5 becomes maximum in the next time zone. Accordingly, of the transistors Q4, Q5, and Q6, the transistors that are turned on are sequentially changed.

  For example, when the voltage V4 is the maximum among the voltages V4, V5, and V6, only the transistor Q4 is turned on among the transistors Q4, Q5, and Q6. At this time, the collector current of the transistor Q4 flows through the resistor R1, and a certain potential difference is generated between both ends of the resistor R1. As a result, the transistor Q1 is turned on. Then, the output voltage V40 of the booster circuit 28 is applied to the gate of the switch element 15, and the switch element 15 is turned on. Since the transistors Q5 and Q6 are in the off state, the switch elements 16 and 17 are in the off state.

By the same operation, when the voltage V5 is maximum, only the switch element 16 is turned on, and when the voltage V6 is maximum, only the switch element 17 is turned on.
Thereby, the maximum detection circuit 22 can turn on the switch of the phase in which the voltage is maximum among the switch elements 15, 16, and 17 provided one for each phase.
Further, the detailed configuration of the booster circuit 28 will be described below.

FIG. 5 is a diagram illustrating an example of the configuration of the booster circuit 28.
The clock generation circuit 281 generates and outputs a clock signal that periodically repeats a high level (voltage V8) and a low level (ground voltage). Specifically, a ring oscillator is employed.
The ring oscillator is an oscillator in which an odd number of three or more inverters are cascade-connected, and the output voltage of the last-stage inverter is output as a clock signal, and the output voltage is input as the input voltage of the first-stage inverter.

The inverter INV1 inverts the phase of the clock signal and outputs it.
The capacitor C1 charges the power from the terminal 8 through the diode D1 when the output of the inverter INV1 is at a low level. At this time, the charging voltage of the capacitor C1 is affected by the forward voltage of the diode D1. When the forward voltage of the diode D1 is VD1 (about 0.7V), the charging voltage is (V8−VD1).

On the contrary, when the output of the inverter INV1 becomes high level, the capacitor C1 is discharged to the capacitor C2 through the diode D2. At this time, a voltage obtained by adding the charging voltage of the capacitor C1 to the voltage V8 is applied to the capacitor C2. At this time, the charging voltage of the capacitor C2 is affected by the forward voltage of the diode D2 and decreases accordingly.
The booster circuit 28 has a voltage V8 that is large enough to ignore the forward voltage of the diodes D1 and D2, and the capacitances of the capacitors C1 and C2 are appropriate according to the power consumption of the load (each element in the maximum detection circuit 22). If it is set to, a voltage twice the voltage V8 can be output.

<Overall operation of magnetic disk device>
The overall operation of the magnetic disk drive having the above configuration will be described below.
FIG. 6 is a diagram showing the voltage of each terminal in the magnetic disk device.
FIG. 6 shows voltage on the vertical axis and time on the horizontal axis. In FIG. 6, VCC indicates the power supply voltage, V4, V5, and V6 indicate the voltages of the terminals 4, 5, and 6, respectively, and V8 indicates the voltage of the terminal 8. V7on is a voltage drop (about 0.3 volts) due to the ON resistance of the switch element 7. Von is a voltage drop (about 0.3 volts) due to the ON resistance of each of the switch elements 15 to 20.

In FIG. 6, it is assumed that the magnetic disk is initially supplied with power from the power source, but unexpectedly cannot be supplied with power from the power source at time t1. Therefore, the power supply voltage VCC is a normal value at t0, but thereafter becomes zero at t1.
Under such circumstances, the magnetic disk device operates as follows.
From t0 to t1, that is, in a normal state, the switch element 7 is in an on state. Therefore, the power from the power source is supplied to the VCM drive circuit 21 through the switch element 7. At this time, the voltage V8 is lower than the power supply voltage VCC by V7on and becomes VCC-V7on. The voltage V8 is equal to the voltage given to the VCM drive circuit 21.

  Thereafter, at t1, the power supply voltage VCC becomes zero. At this time, the determination circuit 3 determines that retraction is required, and notifies the SPM drive circuit 2, the switch element 7, and the control circuit 27 to that effect. Upon receiving this notification, the switch element 7 is turned off. The SPM drive circuit 2 cuts off the system connecting the spindle motor 1 and the power source. As a result, the induced power is prevented from being supplied to the power supply through the switch element 7 or the SPM drive circuit 2.

When notified from the determination circuit 3, the control circuit 27 starts the operation of the maximum detection circuit 22 and the minimum detection circuit 23 and performs on / off control of the switch elements 15 to 20 so as to rectify the induced power of the spindle motor 1. . Here, since the booster circuit 28 in the maximum detection circuit 22 has been operating before t1, the maximum detection circuit 22 can immediately perform on / off control.
Since the induced electric power of the spindle motor 1 is a three-phase alternating current, the phase in which the voltage is maximum changes periodically. According to FIG. 6, the voltage V4 is maximum from t1 to t2, the voltage V5 is maximum from t2 to t3, and the voltage V6 is maximum from t3 to t4.

The maximum detection circuit 22 detects the U-phase, V-phase, and W-phase voltages V4, V5, and V6, and of the switch elements 15, 16, and 17, only the switch element having the maximum voltage is turned on. And That is, the switch elements that are turned on are as follows.
From t1 to t2 Switch element 15
From t2 to t3 Switch element 16
From t3 to t4 Switch element 17
The induced power is supplied to the VCM drive circuit 21 through the switch element that is turned on. Thereby, the voltage V8 becomes as follows.

From t1 to t2 V4-Von
From t2 to t3 V5-Von
From t3 to t4 V6-Von
As described above, the magnetic disk device can efficiently rectify the induced power by turning on only the switching element of the phase having the maximum voltage.

As described above, the booster circuit 28 boosts the voltage V8 regardless of whether it is normal or saved. As a result, the booster circuit 28 can immediately apply the boosted voltage V40 to the switch elements 15 to 20 in the rectifier circuit 25 at the time of saving. Therefore, the magnetic disk device can immediately start the operation of retracting the magnetic head when retracting.
Further, the maximum detection circuit 22 turns off all the switch elements 15, 16, and 17 when normal, and selectively turns on the switch elements 15, 16, and 17 when retracted. Thus, the maximum detection circuit 22 can prevent a DC voltage from being applied to the spindle motor 1 during normal operation, and can rectify the induced power during retraction.

A ring oscillator is employed as the clock generation circuit 281. This is due to the following reason.
At the time of evacuation, since there is only an induced electric power of the spindle motor 1, a high voltage is not applied to the booster circuit. Therefore, the clock generation circuit 281 is required to have a performance capable of stably generating a clock signal even at a low voltage. Since the ring oscillator has a very simple circuit configuration and does not require a bias circuit, the ring oscillator can stably generate a clock signal even at an extremely low voltage (for example, less than 1 volt). For this reason, it is preferable to employ a ring oscillator.

(Embodiment 2)
<Overview>
In the first embodiment, a situation in which the power supply voltage is constantly zero at the time of evacuation is assumed, and a magnetic disk device suitable for the situation is described. However, there is a rare situation where the power supply voltage does not constantly become zero during retraction. For example, if a mechanical switch is included in a magnetic disk device or a power supply system that supplies power to the magnetic disk device, chattering may occur. Chattering is a phenomenon in which on / off is repeated in a very short time when a switch is switched. If chattering occurs, the power supply voltage VCC is intermittently restored even at the time of evacuation, so that power from the power supply is supplied to the terminal 8 through the body diode 7a of the switch element 7.

  On the other hand, at the time of evacuation, since the maximum detection circuit 22 has already started operation, one of the switch elements 15, 16, and 17 is in an on state. At this time, when the power supply voltage VCC is temporarily restored, the power supply voltage VCC is higher than the induced power voltage, and therefore, a phenomenon called latch-up in which the on-state switch element keeps the on-state fixed occurs. For example, if the switch element 15 is in the ON state, the voltage V4 is pulled up to the voltage V8 and is always the maximum among the voltages V4, V5, and V6. As a result, the switch element 15 is fixedly kept on.

  If latch-up occurs, DC power is supplied to the spindle motor 1 through a switch element that is fixedly turned on. This hinders normal rotation of the spindle motor 1 and accelerates the rotation stoppage. As a result, the magnetic disk device cannot efficiently use the induced power, and there is a possibility that the power supplied to the VCM drive circuit 21 is insufficient and the magnetic head cannot be completely retracted.

Therefore, in the magnetic disk device according to the second embodiment, if chattering occurs during retraction, all the switch elements 15, 16, and 17 are turned off. As a result, the magnetic disk device can prevent the DC power from being supplied to the spindle motor 1 and complete the retraction of the magnetic head.
<Overall configuration of magnetic disk device>
The magnetic disk device according to the second embodiment differs from the magnetic disk device according to the first embodiment only in the maximum detection circuit 22, and the other configurations are the same. Therefore, only the maximum detection circuit will be described, and the description of other components will be omitted.

<Maximum detection circuit>
FIG. 7 is a diagram showing a configuration of the maximum detection circuit 30. As shown in FIG.
The maximum detection circuit 30 is configured by adding a transistor Q7 to the maximum detection circuit 22 according to the first embodiment.
Transistor Q7 is a bipolar transistor having the same electrical characteristics as transistors Q4, Q5, and Q6. The transistor Q7 has a collector connected to the terminal 8 and an emitter connected to the switch element 29.

The operation of the maximum detection circuit 30 having the above configuration will be described separately for the normal time and the save time.
Since the switch element 29 is in the off state at the normal time, the switch elements 15, 16, and 17 are all in the off state as in the first embodiment.
On the other hand, at the time of retraction, switch element 29 is turned on, and transistors Q4, Q5, Q6, and Q7 are driven. Among the transistors Q4, Q5, Q6, and Q7, only the transistor having the maximum base voltage is turned on.

  Usually, at the time of evacuation, the voltage V8 once becomes zero. Therefore, of the transistors Q4, Q5, and Q6, the transistor that is turned on periodically changes, and the induced power of the spindle motor 1 is rectified. At this time, the voltage V8 is equal to the rectified voltage. For example, if the switch element 15 is on, V8 = V4−Von. If the switch element 16 is on, V8 = V5-Von. If the switch element 17 is on, V8 = V6-Von. Regardless of which switch element is on, the voltage V8 does not become the maximum among the voltages V4, V5, V6, and V8, and the transistor Q7 remains off.

  However, if chattering occurs, the power supply voltage VCC recovers and the voltage V8 increases. At this time, if the voltage V8 rises higher than the voltages V4, V5, V6, the transistor Q7 is turned on and the transistors Q4, Q5, Q6 are turned off. Thereby, all the switch elements 15, 16, and 17 are turned off. In this way, the magnetic disk device can prevent DC power from being supplied to the spindle motor 1 by turning off all the switch elements 15, 16, and 17 when the power supply voltage VCC is restored. .

When chattering stops and the voltage V8 becomes lower than any of the voltages V4, V5, and V6, the induced power of the spindle motor 1 is again rectified and supplied to the VCM drive circuit 21.
<Overall operation of magnetic disk device>
The overall operation of the magnetic disk drive having the above configuration will be described below.

FIG. 8 is a diagram showing the voltage at each terminal in the magnetic disk device.
V7off in FIG. 8 is a voltage drop due to the body diode 7a (about 0.7 volts).
In FIG. 8, it is assumed that the power supply voltage VCC is restored by chattering during the period from tc to td at the time of saving. Therefore, the power supply voltage VCC shows a normal value in the chattering period from tc to td.

Under such circumstances, the magnetic disk device operates as follows.
The operation of the magnetic disk device is the same as that of the first embodiment up to tc. At this time, of the voltages V4, V5, V6, and V8, the voltage V8 does not become the maximum, and the transistor Q7 maintains the off state.
Thereafter, the power supply voltage VCC returns to a normal value from tc to td. At this time, since the switch element 7 is kept off, the terminal 8 is supplied with power from the power supply through the body diode 7a of the switch element 7. Therefore, the voltage V8 is VCC-V7off. In this case, the voltage V8 can exceed all of the voltages V4, V5, and V6. Then, of the transistors Q4, Q5, Q6, and Q7, only the transistor Q7 is turned on, and all the switch elements 15, 16, and 17 are turned off. As a result, the magnetic disk device can prevent DC power from being supplied to the spindle motor 1. Therefore, a decrease in the rotation speed of the spindle motor 1 during the chattering period can be minimized.

After td, the power supply voltage VCC becomes zero again. At this time, the induced power of the spindle motor 1 is again rectified and supplied to the VCM drive circuit 21.
As described above, the maximum detection circuit 30 sets all the switch elements 15, 16, and 17 to the OFF state when chattering occurs at the time of retraction. As a result, the magnetic disk device can prevent DC power from being supplied to the spindle motor 1, and can minimize the decrease in the rotational speed of the spindle motor 1 during the chattering period.
(Embodiment 3)
<Overview>
In the third embodiment, a magnetic disk device using a comparator for the maximum detection circuit will be described.

<Overall configuration of magnetic disk device>
The magnetic disk device according to the third embodiment is different from the magnetic disk device according to the second embodiment only in the maximum detection circuit 22, and the other configurations are the same. Therefore, only the maximum detection circuit will be described, and the description of other components will be omitted.
<Maximum detection circuit>
FIG. 9 is a diagram illustrating a configuration of the maximum detection circuit 31.

The maximum detection circuit 31 includes a booster circuit 28, a switch element 29, and comparators 32, 33, and 34.
The booster circuit 28 boosts and outputs the voltage V8 whether it is normal or evacuated.
According to the signal voltage from the determination circuit 3, the switch element 29 is turned off when normal and turned on when retracted.

  The comparators 32, 33, and 34 compare the voltages at the plus terminal and the minus terminal, respectively, and output the voltage at the power supply terminal if the voltage at the plus terminal is large, and the voltage at the ground terminal if the voltage at the minus terminal is large. Output. Here, the power supply terminal of each comparator is commonly connected to the switch element 29, and the ground terminal is connected to the ground. Further, the voltage at the power supply terminal is the voltage V40 (high level) boosted by the booster circuit 28 if the switch element 29 is on, and the voltage at the ground terminal is the ground voltage (low level).

The operation of the maximum detection circuit 31 having the above configuration will be described separately for the normal time and the save time.
When normal, the voltage V8 is substantially the power supply voltage VCC. The booster circuit 28 boosts the power supply voltage VCC and supplies it to the switch element 29.
In the normal state, the signal voltage from the determination circuit 3 is at a high level, and the switch element 29 is in an off state accordingly. Therefore, the comparators 32, 33 and 34 are not driven.

As a result, the gates of the switch elements 15, 16, and 17 are all at a low level, so that the switch elements 15, 16, and 17 are all turned off.
On the other hand, at the time of retraction, the switch element 29 is turned on, and the comparators 32, 33, and 34 are driven.
The comparator 32 compares the voltage V4 and the voltage V8, and outputs a high level if the voltage V4 is high, and outputs a low level if the voltage V8 is high. Therefore, when the voltage V4 is higher than the voltage V8, the switch element 15 is turned on. Conversely, when the voltage V4 is lower than the voltage V8, the switch element 15 is turned off.

The comparator 33 compares the voltage V5 and the voltage V8, and outputs a high level if the voltage V5 is high, and outputs a low level if the voltage V8 is high. Therefore, when the voltage V5 is higher than the voltage V8, the switch element 16 is turned on. Conversely, when the voltage V5 is lower than the voltage V8, the switch element 16 is turned off.
The comparator 34 compares the voltage V6 and the voltage V8, and outputs a high level if the voltage V6 is high, and outputs a low level if the voltage V8 is high. Therefore, when the voltage V6 is higher than the voltage V8, the switch element 17 is turned on. Conversely, when the voltage V6 is lower than the voltage V8, the switch element 17 is turned off.

Since the induced power is a three-phase alternating current, the phase of the voltage waveform of each phase differs by 120 degrees in terms of electrical angle. Therefore, the voltage V4 is maximized in a certain time zone, and the voltage V5 is maximized in the next time zone. In response to this, the comparators 32, 33, and 34 periodically output a high level.
For example, when the voltage V4 is the maximum among the voltages V4, V5, and V6, the comparator 32 outputs a high level, and the switch element 15 is turned on accordingly. At this time, the voltage V4 is inputted to the plus terminal of the comparator 32, and the voltage V8 (= V4-Von) is inputted to the minus terminal.

The voltage V4 gradually decreases in a sine wave shape with the passage of time, and the voltage V5 gradually increases. When the voltage V5 becomes higher than the voltage V8 (= V4-Von), the comparator 33 outputs a high level, and the switch element 16 is turned on accordingly. At this moment, the comparator 32 is still on, and the switch element 15 is also on accordingly.
Immediately thereafter, the voltage V4 further decreases and the voltage V5 further increases, so that the voltage V4 becomes lower than the voltage V8 (= V5-Von). As a result, the comparator 32 outputs a low level, and the switch element 15 is turned off accordingly. At this time, since the voltage V5 is higher than the voltage V8, the comparator 33 outputs a high level, and accordingly, the switch element 16 is kept on.

Thus, the comparators 32, 33, and 34 periodically output a high level, so that the switch elements 15, 16, and 17 are periodically turned on, and the induced power can be efficiently rectified. .
Here, if chattering occurs, the power supply voltage VCC is restored, and the voltage V8 rises. At this time, if the voltage V8 rises higher than the voltages V4, V5, and V6, all of the comparators 32, 33, and 34 output a low level. Thereby, all the switch elements 15, 16, and 17 are turned off. In this way, the magnetic disk device can prevent DC power from being supplied to the spindle motor 1 by turning off all the switch elements 15, 16, and 17.

When chattering stops and the voltage V8 becomes lower than any of the voltages V4, V5, and V6, the induced power of the spindle motor 1 is again rectified and supplied to the VCM drive circuit 21.
(Embodiment 4)
<Overview>
The SPM drive circuit 2 according to the second embodiment includes a DC / AC converter therein, and converts DC power of the power source into three-phase AC and supplies it to the spindle motor 1 when it is normal. On the other hand, the rectifier circuit 25 is a kind of AC / DC converter. These are common for converting three-phase alternating current and direct current, although the direction of conversion is reversed. In addition, since the SPM drive circuit 2 operates only when it is normal and the rectifier circuit 25 operates only when saved, they do not operate simultaneously. Therefore, in the magnetic disk device according to the fourth embodiment, the SPM drive circuit 2 and the rectifier circuit 25 share a common part in structure, thereby reducing the size of the semiconductor chip.
<Overall configuration of magnetic disk device>
The magnetic disk device according to the fourth embodiment is different from the magnetic disk device according to the second embodiment only in the SPM drive circuit 2 and the rectifier circuit 25, and the other configurations are the same. Therefore, only the SPM drive circuit 2 and the rectifier circuit 25 will be described, and description of other configurations will be omitted.

FIG. 10 is a diagram showing a configuration of a magnetic disk device according to the present invention.
The conversion circuit 35 converts the DC power from the power source into a three-phase AC when it is normal and supplies it to the spindle motor 1, and converts the induced power of the three-phase AC of the spindle motor 1 into a DC when retracted to convert the DC motor into a VCM drive circuit 21. To supply. The connection relationship of the switch elements 15 to 20 is the same as that of the second embodiment.

The control circuit 36 includes a maximum detection circuit 22, a minimum detection circuit 23, and an SPM control circuit 37.
The SPM control circuit 37 causes the conversion circuit 35 to convert the power of the power supply from a direct current to a three-phase alternating current by selectively giving the switch elements 15 to 20 a high level and a low level in a normal state. At the time of saving, neither high level nor low level is output to each switch element.

<Overall operation of magnetic disk device>
The overall operation of the magnetic disk drive having the above configuration will be described below.
When normal, the switch element 7 is in an on state. Accordingly, the power from the power source is supplied to the VCM drive circuit 21 through the switch element 7 and is also supplied to the conversion circuit 35 through the terminal 8. The conversion circuit 35 converts the direct current into a three-phase alternating current under the control of the SPM control circuit 37 and drives the spindle motor 1.
At the time of evacuation, the conversion circuit 35 rectifies the induced power of the spindle motor 1 and supplies it to the VCM drive circuit 21 as in the rectifier circuit 25 of the second embodiment.

The operation when chattering occurs during retraction is the same as in the second embodiment.
As described above, in the magnetic disk device, the SPM driving circuit 2 and the rectifier circuit 25 share a common part in the structure, so that the semiconductor chip can be reduced in size.
In all the embodiments, the spindle motor is described as a three-phase AC motor. However, the present invention is not limited to this and may be a single-phase AC motor.

In all the embodiments, the rectifier circuit performs full-wave rectification. However, the present invention is not limited to this, and half-wave rectification may be performed.
In all the embodiments, the switch elements 7, 15, 16, 17, 18, 19, and 20 use double diffusion MOS transistors. However, the present invention is not limited to this as long as it switches between the on state and the off state in accordance with the voltage applied to the control input terminal. For example, it may be a MOS transistor other than a double diffusion type, a bipolar transistor, or a thyristor. However, since the MOS transistor can have a smaller on-resistance than the bipolar transistor, it can be formed on the semiconductor chip in a smaller shape, which is advantageous for integration on the semiconductor chip.

In the first embodiment, an example of the configuration of the booster circuit 28 has been described with reference to FIG.
FIG. 11 is a diagram illustrating an example of the configuration of the booster circuit 28.
In FIG. 11, P-channel MOS transistors Tr1 and Tr2 are used instead of the diodes D1 and D2 in FIG.

  The level shifter 282 is a circuit that expands the level of the output signal with respect to the input signal. Thereby, inverter INV2 can operate | move reliably. The level shifter 282 outputs a voltage V40 of the terminal 40 when outputting a high level, and outputs a ground voltage when outputting a low level. It is assumed that the output signal has the same phase as the input signal. Here, when the level shifter 282 has an inverter function and the output signal has a phase opposite to that of the input signal, the inverter INV2 is unnecessary.

  When a discrete product is used, the transistor Tr1 is used by connecting a diode in parallel. At this time, as shown in FIG. 11, the source S of the transistor Tr1 and the anode of the diode are connected, and the drain D of the transistor Tr1 and the cathode of the diode are connected. When the transistor Tr1 is configured in the semiconductor integrated circuit, the semiconductor substrate or a diffusion layer corresponding to the semiconductor substrate and the drain diffusion layer are electrically connected. As a result, a diode is equivalently connected in parallel to the transistor Tr1. The same applies to the transistor Tr2.

This booster circuit operates as follows.
The inverter INV1 receives the clock signal from the clock generation circuit 281 to perform a switching operation, inverts the phase of the clock signal, and outputs the inverted signal.
Since the transistor Tr1 is turned on when the output of the inverter INV1 is at a low level, the capacitor C1 is charged with power from the terminal 8. The voltage drop due to the on-resistance of the transistor Tr1 is about 0.3 volts, which is smaller than the forward voltage (about 0.7 volts) of the diode D1. Therefore, the charging voltage of the capacitor C1 becomes higher than that in the case of FIG. Further, when the output of the inverter INV1 is low level, the transistor Tr2 is turned off because the output of the inverter INV2 is high level. Therefore, the charge accumulated in the capacitor C2 does not flow back to the capacitor C1.

  Next, when the output of the inverter INV1 is at a high level, the capacitor C1 is discharged to the capacitor C2 through the transistor Tr2. At this time, since the transistor Tr1 is in an off state, the charge of the capacitor C1 does not flow backward to the terminal 8. Further, the transistor Tr2 is in an ON state because the output of the inverter INV2 is at a low level if the output of the inverter INV1 is at a high level. Here, the voltage drop due to the on-resistance of the transistor Tr2 is about 0.3 volts, which is smaller than the forward voltage (about 0.7 volts) of the diode D2. Therefore, the charging voltage of the capacitor C2 becomes higher than that in the case of FIG.

Thus, this booster circuit has a higher boosting capability than the booster circuit of FIG. 5, and is useful in a situation where the power at the time of saving is limited.
Further, paying attention to further miniaturization, the booster circuit may be configured as follows.
FIG. 12 is a diagram illustrating an example of the configuration of the booster circuit 28.
In FIG. 12, an N-channel MOS transistor Tr3 is used instead of the transistor Tr1 in FIG.

In general, an N-channel MOS transistor has a current-carrying capacity two to three times that of a P-channel MOS transistor. For this reason, the entire chip area of the semiconductor integrated circuit can be reduced by employing an N-channel MOS transistor. The cost merit that the chip unit price can be reduced can be expected when the chip area is reduced.
The N-channel MOS transistor Tr3 is used by connecting a diode in parallel when a discrete product is used. At this time, as shown in FIG. 12, the source S of the transistor Tr3 and the anode of the diode are connected, and the drain D of the transistor Tr3 and the cathode of the diode are connected. When the transistor Tr3 is configured inside the semiconductor integrated circuit, the semiconductor substrate or a diffusion layer corresponding to the semiconductor substrate and the source diffusion layer are electrically connected. As a result, a diode is equivalently connected in parallel to the transistor Tr3.

The transistor Tr3 is not turned on unless a voltage higher than the source voltage is input to the gate. Therefore, on / off control is performed by the output of the inverter INV2.
Note that the transistor Tr2 cannot be replaced with an N-channel MOS transistor that requires a voltage higher than the source voltage as a gate voltage.
This booster circuit operates as follows.

The inverter INV1 receives the clock signal from the clock generation circuit 281 to perform a switching operation, inverts the phase of the clock signal, and outputs the inverted signal.
When the output of the inverter INV1 is at a low level, the output of the inverter INV2 is at a high level, so that the transistor Tr3 is turned on. At this time, the capacitor C1 is charged with electric power from the terminal 8. The voltage drop due to the on-resistance of the transistor Tr3 is about 0.3 volts, which is smaller than the forward voltage (about 0.7 volts) of the diode D1. Therefore, the charging voltage of the capacitor C1 becomes higher than that in the case of FIG. Further, when the output of the inverter INV1 is low level, the transistor Tr2 is turned off because the output of the inverter INV2 is high level. Therefore, the charge accumulated in the capacitor C2 does not flow back to the capacitor C1.

  Next, when the output of the inverter INV1 is at a high level, the capacitor C1 is discharged to the capacitor C2 through the transistor Tr2. At this time, since the transistor Tr3 is in an OFF state, the charge of the capacitor C1 does not flow backward to the terminal 8. Further, the transistor Tr2 is in an ON state because the output of the inverter INV2 is at a low level if the output of the inverter INV1 is at a high level. Here, the voltage drop due to the on-resistance of the transistor Tr2 is about 0.3 volts, which is smaller than the forward voltage (about 0.7 volts) of the diode D2. Therefore, the charging voltage of the capacitor C2 becomes higher than that in the case of FIG.

  Note that this booster circuit cannot fully conduct the transistor Tr3 at the beginning of the operation, that is, when the output voltage V40 is not sufficiently boosted. Therefore, initially, the capacitor C1 receives power through a diode connected in parallel with the transistor Tr3, and the boosting capability of the boosting circuit is not good. However, when the output voltage 40 is sufficiently boosted with the passage of time, the transistor Tr3 is completely turned on, and the boosting capability of the boosting circuit is improved.

Since the booster circuit according to the present invention operates in advance from the normal time even if the initial boosting capability is not good, it is considered that the booster circuit is sufficiently boosted until it becomes necessary to retract the magnetic head. Therefore, it is considered that there is no problem in actual use.
In the first embodiment, a ring oscillator is employed as the clock generation circuit 281. However, the present invention is not limited to this as long as the clock signal can be stably generated even at a low voltage.

  The magnetic disk device of the present invention can be used for a hard disk drive (HDD).

1 is a diagram showing a configuration of a magnetic disk device disclosed in Patent Document 1. FIG. It is a figure which shows the structure of the magnetic disk apparatus of a reference example. 1 is a diagram showing a configuration of a magnetic disk device according to the present invention. 2 is a diagram illustrating a configuration of a maximum detection circuit 22. FIG. 3 is a diagram illustrating an example of a configuration of a booster circuit 28. FIG. It is a figure which shows the voltage of each terminal in a magnetic disc unit. 2 is a diagram showing a configuration of a maximum detection circuit 30. FIG. It is a figure which shows the voltage of each terminal in a magnetic disc unit. 3 is a diagram showing a configuration of a maximum detection circuit 31. FIG. 1 is a diagram showing a configuration of a magnetic disk device according to the present invention. 3 is a diagram illustrating an example of a configuration of a booster circuit 28. FIG. 3 is a diagram illustrating an example of a configuration of a booster circuit 28. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spindle motor 2 SPM drive circuit 3 Judgment circuit 7 Switch element 15-20 Switch element 21 VCM drive circuit 22, 30 Maximum detection circuit 23 Minimum detection circuit 25 Rectifier circuit 26 Voice coil motor 27, 36 Control circuit 28 Booster circuit 29 Switch element 31 Maximum detection circuit 32, 33, 34 Comparator 35 Conversion circuit 37 SPM control circuit 281 Clock generation circuit 282 Level shifter

Claims (9)

A magnetic disk device having an auto retract function,
A determination circuit for monitoring the power supply voltage to determine whether or not it is equal to or less than a predetermined value;
Is provided on the wiring connecting the actuator for driving the coil and the magnetic head of the motor for rotating the magnetic disk, and a switching element for switching an ON state and an OFF state in response to the voltage applied to the control input terminal ,
Said actuator and is provided on a wiring connecting the control input terminal of the switching element, wherein the decision circuit boosts the voltage supplied to the actuator via the switching element when it is determined that the predetermined value or less A booster circuit for obtaining a voltage to be supplied to the control input terminal of the switch element,
When the determination circuit determines that the value is equal to or less than a predetermined value, the induced power generated in the motor is supplied to the actuator by applying the voltage obtained by the booster circuit to the control input terminal of the switch element and turning it on. And a switch control means. The booster circuit includes:
And tree Yapashita,
A clock generation circuit that generates a clock signal that repeats a high level and a low level at a predetermined period and outputs the clock signal to the first terminal of the capacitor ;
Enter the voltage the clock signal is supplied to the actuator at a low level to a second terminal of said capacitor, said clock signal to output a voltage from the second terminal of the capacitor at the high level The magnetic disk apparatus according to claim 1, further comprising: a step-up control circuit. The clock generation circuit includes:
It is a ring oscillator in which an odd number of three or more inverters are connected in cascade, and the output voltage of the last stage inverter is output as a clock signal, and the output voltage is input as the input voltage of the first stage inverter. The magnetic disk device according to claim 2. The switch element is a MOS (Metal Oxide Semiconductor) type transistor, the source of the transistor is connected to the motor side, and the drain is connected to the actuator side.
The switch control means includes
When said determination circuit determines that less than a predetermined value, a voltage obtained by said boosting circuit to conduct between the drain and the source by applying a gate of said transistor, when said determination circuit determines that no less than a predetermined value, the booster 2. The magnetic disk device according to claim 1, wherein the drain and the source are not conducted by not applying the voltage obtained by the circuit to the gate of the transistor. A magnetic disk device having an auto retract function,
A determination circuit for monitoring the power supply voltage to determine whether or not it is equal to or less than a predetermined value;
A plurality of switching elements are provided respectively on each phase of the wiring connecting the actuator for driving each coil and the magnetic head of the three-phase motor for rotating the magnetic disk,
It said actuator and is provided on a wiring connecting the control input terminals of the plurality of switching elements, supply the decision circuit when it is determined that the predetermined value or less is rectified by the plurality of switching elements to said actuator A booster circuit that obtains a voltage to be supplied to the control input terminals of the plurality of switch elements by boosting the generated voltage;
A specific circuit for specifying a location indicating the maximum voltage among the voltages on the motor side of the plurality of switch elements;
When the determination circuit determines that it is less than or equal to a predetermined value, the voltage obtained by the booster circuit is applied only to the control input terminal of the switch element at the specified location to turn on the switch element, thereby And a control circuit that rectifies the induced electric power of the motor and supplies the rectified electric power to the actuator. The specific circuit detects a voltage on the motor side of the plurality of switch elements and a voltage on the actuator side of the switch elements, and specifies a location indicating the maximum voltage among the detected voltages ,
6. The magnetic disk device according to claim 5 , wherein the control circuit turns off all the switch elements when the specified location is on the actuator side of the plurality of switch elements . Wherein the plurality of switching elements, MOS is (Metal Oxide Semiconductor) transistor, the source of the transistor to the motor side, the magnetic according to claim 5, characterized in that the drain is connected to the actuator side Disk unit. The control circuit further includes:
When the determination circuit does not determine that the value is equal to or less than a predetermined value, the plurality of switch elements are selectively turned on to supply three-phase AC power to the three-phase motor and rotate the magnetic disk. The magnetic disk device according to claim 5, wherein the magnetic disk device is driven. A magnetic disk device having an auto retract function,
A determination circuit for monitoring the power supply voltage to determine whether or not it is equal to or less than a predetermined value;
A plurality of switching elements are provided respectively on each phase of the wiring connecting the actuator for driving each coil and the magnetic head of the three-phase motor for rotating the magnetic disk,
Provided on the wiring connecting the actuator and the control input terminals of the plurality of switch elements, and when the determination circuit determines that the value is equal to or less than a predetermined value, is rectified by the plurality of switch elements and supplied to the actuator A step-up circuit for obtaining a voltage to be supplied to the control input terminals of the plurality of switch elements by boosting the voltage;
A plurality of comparison circuits for comparing the voltage on the motor side and the voltage on the actuator side of each of the plurality of switch elements;
When the determination circuit determines that the voltage is equal to or less than a predetermined value, the switch element determined by the plurality of comparison circuits that the motor side voltage is higher than the actuator side voltage is turned on, and the motor side voltage is the actuator side voltage. And a control circuit that rectifies the induced power of the three-phase motor and supplies it to the actuator by turning off the switch element determined to be lower than the switching element.

Images