JPH02290174A - Motor control device for magnetic disc device - Google Patents

Abstract

PURPOSE:To remove current due to counter electromotive force, generated in a spindle motor upon the abnormality of a power source, from the spindle motor by a method wherein a switch means, short-circuit between a coil and an earth, is provided to set the switch means in ON condition when the abnormality of the power source supplied to a motor driving means is detected. CONSTITUTION:When a power source voltage, supplied to a motor driving circuit 13, is reduced or a power source is intercepted, the operation of the motor driving circuit 13 becomes impossible. In this case, the gate voltage of a FET 15 is biased to Vt. When the FET is put ON, the coil phases 12b, 12c of a spindle motor 11 are short-circuited. The spindle motor 11 is being rotated by an inertia force and current due to counter electromotive force, generated by the rotation, may be consumed at the place of the short-circuit as an energy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention J (Field of Industrial Application) The present invention relates to a motor control device for a magnetic disk device suitable for controlling a motor in the event of a power failure.

(Prior Art) In a magnetic disk device, a disk, which is a recording medium, is rotated by driving a spindle motor.

By the way, when the motor drive is stopped due to a power supply abnormality such as a drop in electrical voltage or a power cut, the spindle motor does not stop immediately and continues to rotate due to inertia for a while. Here, if it is rotating due to inertia,
There is a problem in that a back electromotive force is generated, and a current due to this back electromotive force flows through the coils that constitute the motor, resulting in a delay in the rotation stop time of the spindle motor.

In magnetic disk devices, especially hard disk devices, when the rotational speed of the disk decreases, the magnetic head comes into contact with the disk, causing damage to the head, so it is necessary to quickly stop the rotation of the spindle motor in the event of a power failure.

(Problems to be Solved by the Invention) As described above, conventionally, there has been a problem in that the rotation of the spindle motor does not stop promptly when a power failure occurs, leading to damage to the head and the like.

The present invention has been made in view of the above-mentioned points, and is capable of quickly stopping the rotation of a spindle motor in the event of a power failure, and
The purpose of this invention is to provide a motor control device for magnetic disk drives that can prevent head damage.

[Structure 1 of the Invention (Means for Solving the Problems) That is, a motor control device for a magnetic disk drive according to the present invention is provided with a switch means for short-circuiting between the phases of the coils constituting the spindle motor or between the coils and the ground. When an abnormality in the power supply supplied to the motor driving means is detected, the switch means is set to the ON state. The current generated by the back electromotive force generated when the motor is running is removed from the spindle motor.

Further, the present invention is characterized in that a field effect transistor is used as the switch means.

That is, the field effect transistor is set to short-circuit between the phases of the coil or between the coil and the ground by applying a gate voltage, and when a power supply abnormality is detected, the gate voltage is applied to the field effect transistor, In addition, a capacitor or the like is used to maintain the gate voltage.

(Function) According to the above configuration, when a power supply abnormality occurs such as a decrease in the power supply voltage or a power supply interruption, a short circuit occurs between the coil phases or between the coil and the ground. therefore,
The current due to the back electromotive force generated in the spindle motor can be removed from the spindle motor in a short time, and its rotation can be stopped more quickly than if it were not short-circuited. By preventing contact, damage to the head can be prevented.

(Embodiment) Hereinafter, a motor III control device for a magnetic disk drive according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the circuit configuration thereof. The spindle motor 11 is a motor that rotates a disk (not shown), and is composed of, for example, a brushless DC motor, and has three-phase coils 12a to 12C.

Each of the coils 12a-12c has one end connected in common, and the other end connected to the motor drive circuit l3.

The motor drive circuit 13 receives power supplied from the power supply circuit 14 and drives the spindle motor 1l.

That is, each coil 12a to 12c is sequentially energized to rotate the spindle motor 11.

In this case, there are two drive methods: a full-wave drive method in which the coil is energized in both directions, and a half-wave drive method in which the coil is energized in one direction. According to the drive method, a voltage is applied to the common terminal of each coil 12axl2c, and the coils 12a to 12c are sequentially energized in one direction to drive the spindle motor l1.

Here, a field effect transistor (
A FET (hereinafter referred to as FET) 15 is interposed.

This FET 15 is controlled on/off by a bias circuit 1G, which will be described later, and is set to short-circuit the coils when turned on (when a gate voltage is applied).

The bias circuit 1B mainly includes a transistor TRI for turning on the FET 15 (applying a gate voltage) when a power supply abnormality is detected by a detection circuit 17, which will be described later, and a capacitor C for holding the gate voltage. There is. Note that R1 to R4 are resistors, and D1 is a diode.

The detection circuit 17 is a circuit that detects an abnormality in the power supply supplied to the motor drive circuit l3, such as a drop in the power supply voltage or a cutoff of the power supply, and when a power supply abnormality is detected, a detection signal of the rLJ level is sent to the motor drive circuit. output to l3 and bias circuit l6.

Next, the operation of this embodiment will be explained.

When normal power is supplied from the power supply circuit 14 to the motor drive circuit 13, the detection circuit 17 outputs a detection signal at the rHJ level. This rHJ level detection signal enables the motor drive circuit I3 to operate. Also, by the same signal, the transistor T of the bias circuit l6
RI turns on.

When the transistor TRI is in the on state, the collector voltage becomes close to OV, so the FET15 is turned off (the source-drain resistance is opened). As a result, the coils 12a to 12c are normally sequentially energized through the motor drive circuit l3, and the spindle motor l1 rotates.

Here, the motor drive circuit! When the power supply voltage supplied to 3 decreases or the power supply is cut off, the detection circuit 17
A detection signal of the rLJ level is output from. This rLJ
The level detection signal causes the motor drive circuit l3 to become inoperable. Also, by the same signal, the bias circuit l
Transistor TRI of No. 6 is turned off.

At the same time, diode D1 becomes reverse biased as Vcc (power supply) drops and it becomes below Vt, shown below. At this time, since the transistor TRI is in the off state, the gate voltage of the FET15 is biased to Vt.

In the above equation, VCH is the reflector-emitter voltage of the transistor TRI when it is saturated, and VD is the forward voltage drop of the diode DI.

In this way, the bias circuit 16
When a gate voltage is applied to FET15, FET15 is turned on (the source-drain resistance is short-circuited).

When the FET 15 is turned on, the coil phases of the coils 12b and 12c of the spindle motor l1 are short-circuited. At this time, the spindle motor 11 is rotating due to inertia force while the drive of the motor drive circuit 13 is stopped, and due to the short circuit between the coil phases, a current due to the back electromotive force generated by the rotation is transmitted to the short circuit point. Consumed as energy.

Therefore, the current due to the back electromotive force generated in the spindle motor 1l can be removed from the spindle motor 11 in a short time, and its rotation can be stopped more quickly than in the normal case, that is, when there is no short circuit. This prevents the magnetic head from coming into contact with the rotating recording medium, thereby preventing damage to the head.

In this case, even if the gate voltage cannot be applied to the FET 15 due to power cutoff, for example, the gate voltage can be maintained for a predetermined period of time by the capacitor C provided in the bias circuit l6.

This period is determined by the time constants of capacitor C and resistor R3. Note that the gate voltage at this time decreases due to leakage current from the capacitor C, but F E T 1
Since the gate input current of FET 5 is very small, the FET 15 can be kept in the ON state until the spindle motor 11 stops rotating.

In this embodiment, the FET 15 is provided between the coil phases of the spindle motor l1, but for example, as shown in FIG. Even with this configuration, the same effects as in the above embodiment can be obtained.

Also, instead of FETl5, a relay circuit 21 is used as shown in FIG. 3, and normally the switch 22 of the relay circuit 2l
is set to the b side, and the detection circuit! When a power supply abnormality is detected by 7, the switch 22 may be switched to the a side to short-circuit the coil phases. However, when such a relay circuit is used, it requires a large mounting area and there are problems such as lack of reliability of the mechanical part of the relay, so it is inferior to the case of FET.

[Effect 1 of the Invention As described above, according to the present invention, the current due to the back electromotive force generated in the spindle motor can be removed from the spindle motor in a short time when the power supply is abnormal. Therefore, it is possible to quickly stop the rotation of the spindle motor and prevent damage to the head.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a circuit configuration according to an embodiment of the present invention, FIG. 2 is a diagram showing a circuit configuration when using an FET according to another embodiment of the present invention, and FIG. 3 is a diagram showing a circuit configuration according to an embodiment of the present invention. It is a figure which shows the circuit structure in the case of using the relay circuit based on another Example. ! l... Spindle motor, 12a to 12c... Coil, l3... Motor drive circuit, 14... Power supply circuit, 15... FET (field effect transistor), l6.
...Bias circuit, 17...Detection circuit, TRI...
Transistor, Rl to R4...Resistance, DI...Diode, C...Condenser, 21...Relay circuit, 22...Switch. Applicant's agent Patent attorney Takehiko Suzue】V Figure 3 Figure 2

Claims (2)

[Claims] (1) A spindle motor that rotates a recording medium, a motor drive means that drives this spindle motor, a detection means that detects an abnormality in the power supplied to this motor drive means, and when in an on state, the spindle motor a switch means for short-circuiting between the phases of the coil constituting the coil or between the coil and the ground, and a switch control means for setting the switch means to an on state when a power supply abnormality is detected by the detection means, A motor control device for a magnetic disk drive, characterized in that a current due to a back electromotive force generated in the spindle motor is removed from the spindle motor when an abnormality occurs. (2) A spindle motor that rotates a recording medium, a motor drive means that drives this spindle motor, a detection means that detects an abnormality in the power supplied to this motor drive means, and a phase gap between coils that constitute the spindle motor. or a field effect transistor that is interposed between the coil and ground and shorts between the phases of the coil or between the coil and ground when a gate voltage is applied; and when the power supply abnormality is detected by the detection means;
a bias circuit that applies a gate voltage to the field effect transistor and has a holding means for holding the gate voltage, and when a power failure occurs, a current due to a back electromotive force generated in the spindle motor is transferred to the spindle motor. A motor control device for a magnetic disk device, characterized in that the motor control device is removed from the motor.