JP3193195B2 - Emergency evacuation circuit for magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emergency evacuation circuit for a magnetic head used in a magnetic disk drive.

[0002]

2. Description of the Related Art In an emergency evacuation circuit for a magnetic head in a magnetic disk drive, it is required to operate when power is cut off, for example, during a power failure, so that a different path from the magnetic head drive circuit during normal operation is used. It is necessary to evacuate using a voice coil motor or the like by the drive circuit in the above. In addition, it is necessary to use a charge stored in a capacitor, a back electromotive force generated by a spindle motor, and the like, separately from a power supply in a normal state. In particular, the latter does not require a capacitor, and there is no need to accumulate charge in the capacitor,
Recently, the spindle motor is frequently used because it has an advantage that a brake torque can be generated in the spindle motor so that the spindle motor can be stopped quickly.

FIGS. 3 and 4 show an example of a conventional emergency retract circuit for a magnetic head (Japanese Patent Laid-Open No. 63-83980).
No.). FIG. 3 is an overall view of the emergency evacuation circuit, and FIGS.
(B) shows a specific example of an emergency evacuation command circuit and a changeover switch circuit at the time of a power failure among the emergency evacuation circuits. In the figure, 1
Is a spindle motor for rotating a magnetic disk, 2 is a spindle motor drive circuit, 3 is a voice coil motor for driving a magnetic head, 4 is a voice coil motor drive circuit, 5 is a power supply voltage monitoring circuit for issuing an emergency evacuation command, etc. , A switch 8 for switching the voice coil motor drive circuit 4 based on an emergency evacuation instruction, and 7 a rectifier circuit for supplying power to the voice coil motor drive circuit 4 during emergency evacuation.

[0004] The emergency retreat operation of the magnetic head will be described with reference to FIG. During normal operation, the changeover switch 8 is at the position of the contact a and is driven by the voice coil motor drive circuit 4. Here, the normal power supply V of the entire circuit due to a power failure or the like.
When cc is turned off, an emergency evacuation command is output, and the changeover switch 8 is set to the position of the contact b. At this time, the rotation speed of the spindle motor 1 gradually decreases, and a voltage based on the back electromotive force of each winding is output in a three-phase sine wave shape.

The rectifier circuit 7 supplies a voltage lower than the voltage of the highest phase of the three-phase sinusoidal voltages by a diode forward drop voltage to the changeover switch 8. Here, since the changeover switch 8 is at the position of the contact b,
The rectified voltage flows through the voice coil motor 3 to the ground terminal. Therefore, the voice coil motor 3 is driven, and the magnetic head is retracted.

The switch 8 includes a switch using a relay as shown in FIG. 4A and a switch using a semiconductor switch element as shown in FIG. 4B. and an auxiliary power source by the diode D _7. Further, with the recent demand for miniaturization, the use of semiconductor switches has become mainstream in order to perform quick operation. Note that Q ₁ , Q ₂ , Q ₄ , Q ₅ are
It is a switching transistor for driving the changeover switch 8.

[0007]

According to the prior art,
The voice coil motor drive current for retreating the magnetic head at the time of emergency retreat flows from the spindle motor 1 to the voice coil motor 3 through the rectifier circuit 7 and the changeover switch 8.
For this reason, a loss such as a diode forward drop voltage of the rectifier circuit 7 occurs. Conventionally, the loss when the normal power supply Vcc is high is negligible. However, as the power consumption of the device has recently been reduced and the power supply Vcc becomes 5 V or 3 V, the voltage loss generated in the rectifier circuit 7 is ignored. Will not be able to do so, which will be a serious obstacle to ensuring emergency evacuation.

For example, when the power supply Vcc is 3 V, the back electromotive force generated in the spindle motor 1 is usually about 2 Vp-p, and the diode voltage loss of the rectifier circuit 7 is 0.7 V × 2.
In this case, only 0.6 V remains, and considering the resistance loss of the changeover switch 8, the voltage applied to the voice coil motor 3 is about 0.1 to 0.2 V, which makes it difficult to supply a sufficient current. Become. Therefore, it is difficult to reliably perform the emergency evacuation operation, which may result in damage to the magnetic disk.

Due to the above problems, when the voltage of the power supply is reduced, a diode having a small forward voltage drop, such as an expensive Schottky diode, is used as the diode of the rectifier circuit 7. Method is needed,
This also hinders integration and causes problems such as an increase in the number of components. In addition, due to the diode loss of the rectifier circuit 7, the current that can flow through the voice coil motor 3 decreases, and the emergency retreat operation time of the magnetic head increases. Since the period during which the current flows from the rectifier circuit 7 to the voice coil motor 3 is reduced and the ripple of the output voltage of the rectifier circuit 7 is increased, there is a problem that a smooth emergency retreat operation is difficult.

An object of the present invention is to eliminate the need for an auxiliary power supply, reduce the occurrence of losses, increase the drive current for retracting the magnetic head, realize quick and smooth emergency retraction, facilitate integration, and reduce costs. It is to reduce.

[0011]

SUMMARY OF THE INVENTION An emergency evacuation circuit for a magnetic head according to the present invention selects the maximum voltage of the back electromotive force generated in each phase of a magnetic disk drive motor, and uses this maximum voltage as the magnetic head drive motor. A bias current is supplied to the transistor-type maximum voltage selection circuit by the back electromotive force of the magnetic disk drive motor in response to the emergency evacuation command signal and the transistor-type maximum voltage selection circuit. An activation circuit for activating the circuit.

[0012]

In the emergency retraction circuit for a magnetic head according to the present invention, the activation circuit activates the transistor type maximum voltage selection circuit using the back electromotive force of the magnetic disk drive motor in response to the emergency retraction command signal. The transistor type maximum voltage selection circuit selects the maximum voltage of the back electromotive force generated in each phase of the magnetic disk drive motor and supplies it to the magnetic head drive motor, thereby urgently retracting the magnetic head.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an emergency evacuation circuit for a magnetic head according to the present invention; FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a specific circuit diagram of a main part of FIG. 1, and the same parts as those in FIGS. 3 (a), (b) and (c) are the same. Signs are attached. In FIG. 1, reference numeral 6 denotes a transistor type maximum voltage selection circuit which selects a phase which generates a maximum voltage from a back electromotive force generated in each phase of the spindle motor 1 at the time of emergency evacuation. An activation circuit 20 activates the transistor-type maximum voltage selection circuit 6 using the back electromotive force of the spindle motor 1 in response to the emergency evacuation command signal. In the prior art, the electric current is supplied to the voice coil motor 3 by the electric charge stored in the capacitor of the auxiliary power supply circuit. However, in this embodiment, the back electromotive force of the spindle motor 1 is used instead of the external power supply.

In FIG. 2, the collectors of the transistors Q _{7 to} Q ₉ are commonly connected to each other and set to a point, and the collector of the transistor Q ₁₀ is set to b point. The points a and b in FIG.
They correspond to the points a and b in FIG. 1, respectively. Also,
The emitters of the transistors Q _{7 to} Q ₉ are respectively set at points c, d,
It is point e. Point c, point d and point e in FIG.
Point, point d, and point e respectively correspond.

In FIG. 2, transistors Q ₁ to Q ₁
Of Q _3, turned on only transistor connected to a phase which generates the maximum voltage by the spindle motor coil terminals. Only one transistor of the one and the transistor Q ₇ to Q ₉ of the transistors Q ₄ to Q ₆ are connected to the on and became transistor turned on,
The transistor connected to the phase that generates the selected maximum voltage supplies power to the voice coil motor 3 for driving the magnetic head. Considering this retraction operation, the voice coil motor 3
It can be seen that the loss in the path for supplying the current to the transistor is determined only by the transistor saturation voltage, and is much smaller than the forward voltage drop of the diode of the rectifier circuit in the case of FIG.

[0016]

According to the emergency retreat circuit of the magnetic head of the present invention, the magnetic head retreat drive current due to the back electromotive force of the magnetic disk drive motor can be increased and the ripple can be reduced, so that the emergency retreat operation can be performed. Is performed quickly and smoothly. Further, since an auxiliary power supply is not required, and a diode and a large-capacity capacitor are not required, the number of parts can be reduced, the integration of semiconductor elements can be easily performed, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an emergency evacuation circuit for a magnetic head according to the present invention.

FIG. 2 is a specific circuit diagram of a main part of FIG.

FIG. 3 is a circuit diagram of a conventional emergency evacuation circuit of a magnetic head.

FIG. 4 is a circuit diagram showing a specific example of a changeover switch of the emergency evacuation circuit.

[Explanation of symbols]

 Reference Signs List 1 spindle motor (magnetic disk drive motor) 2 spindle motor drive circuit 3 voice coil motor (magnetic head drive motor) 4 voice coil motor drive circuit 5 retract command circuit 6 transistor type maximum voltage selection circuit 7 rectifier circuit 8 changeover switch 20 activation circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-6560 (JP, A) JP-A-1-119959 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 21/12

Claims (1)

(57) [Claims] 1. A transistor-type maximum voltage selection circuit for selecting a maximum voltage of back electromotive force generated in each phase of a magnetic disk drive motor and supplying the maximum voltage to a magnetic head drive motor, an emergency evacuation command signal And an activation circuit for activating the transistor type maximum voltage selection circuit using the back electromotive force of the magnetic disk drive motor in response to the emergency response circuit.