KR100396483B1 - Head retract circuit in hard disk drive - Google Patents

Abstract

The present invention relates to a head return circuit of a hard disk drive. The head return circuit is a head return circuit for returning a head which reads and writes information from a hard disk drive to a safe area, and supplies a constant current to the voice coil motor for moving the head to the safe area of the head. After causing the movement of the head, when the head is moved to the safety area and positioned at a specific position is to supply a constant voltage to the voice coil motor. According to the present invention, since the instantaneous electromotive force of the voice coil motor becomes zero or the first bounce is about to occur, the constant current mode is automatically changed from the constant current mode to the constant voltage mode, thereby increasing the size of the initial constant current to prevent head return failure. When the counter electromotive force reaches zero, a constant voltage is applied so that sufficient current is supplied to the voice coil motor at the moment, eliminating bouncing, but the magnitude of the instantaneous peak current is smaller than in the constant constant voltage mode to reduce the current breakdown voltage of the semiconductor. It is also costly.

Description

Head return circuit of hard disk drive {HEAD RETRACT CIRCUIT IN HARD DISK DRIVE}

The present invention relates to a drive circuit of a hard disk drive, and more particularly, to a head return circuit of a hard disk drive for returning the head to a safe area when necessary.

In general, when a hard disk drive system loses power, a voice coil motor (hereinafter referred to as a VCM) is used to write data to the disk or to prevent the data stored on the internal disk from being lost. It is essential to have a head return circuit which allows the head reading the recorded data to operate to evacuate the safety zone without damaging the disk.

In the head return circuit, there are two methods of supplying power to the VCM so that the VCM performs the head return operation. The first method uses a constant current to supply power to the VCM, and the second method uses a constant voltage. to be.

In the first method, a constant current is applied to the VCM, in order to move the VCM to the safe area, a constant current flows to the VCM so that the head mounted on the VCM moves to the safe area. There is a problem that a malfunction occurs such as a bouncing phenomenon and a head return failure that protrude while colliding with the mechanism of the spindle motor.

If the constant current is large, bounce may occur while the VCM moves to the safe area depending on the counter electromotive force of the VCM and the timing of the head return operation, causing noise and disk wear. In order to minimize the occurrence of this bouncing and to stably move the head to the safe area, the constant current must be reduced. In this case, the head may not be located in the safe area due to the head return failure. When the disc is damaged can happen.

As a first means to solve this problem, a head return circuit has been provided in which the constant current applied to the VCM has two levels. Korean Patent Laid-Open No. 1999-006464 discloses a head return circuit of this type.

As soon as the power supplied to the spindle motor 12 from the spindle motor driver 108 is cut off and the spindle motor 12 is powered off, the first line 201 is high due to the voltage charged in the capacitor 210. FETs 82 and 84 including the first switch are turned on.

When the FETs 82, 84 are turned on, the bipolar transistors 90, 91, 92, 93 are turned on to supply a single-phase rectified current to the VCM 14 for head return.

Meanwhile, the capacitor 232 is charged from the capacitor 210 after the transistor 214 is turned off. After a predetermined delay time determined by the time constant of the RC circuit 230, when the capacitor 232 is charged, the line 203 goes high and the second switch FET 250 is turned on. This turns the remaining bipolar transistors 94 and 95 on, which completely enables all three phases of the rectifier circuit 80.

The effect of turning on the phase of the spindle motor 12 is the effect of providing a varying duty cycle of the return circuit current as a result. If only one phase is turned on, the current in the return circuit has a duty cycle of about one third. Then, if the remaining phase is turned on, the current in the return circuit will have a duty cycle of 100%.

This change in duty cycle effectively acts as a change in torque and actuator acceleration because the modulation rate is very fast relative to the actuator's time response.

However, in the prior art shown in FIG. 1, the problem is that the RC time constant of the RC circuit 230 is made irrespective of the situation of the VCM. In other words, if the head position is close to the safe area, a small current can move to the safe area, but if it is far away, a larger current is required. Therefore, the amount of current must be changed each time according to the position of the arm. You can do less. However, in the conventional constant current return method, since it is difficult to determine the position of the head of the VCM at the point of time for the return operation, it is difficult to vary the return current amount.

On the other hand, as a second means for solving the above problems, a head return circuit for applying a constant voltage to the VCM has been provided. Korean Laid-Open Patent Publication No. 1998-032551 discloses a head return circuit of this type.

Hereinafter, a conventional head return circuit for applying a constant voltage to the VCM will be described with reference to FIG. 2.

The speed at which the actuator motor 54 can move the head attached to it varies with the magnitude of the voltage across the nodes 56 and 58.

When the disk drive unit is in the head return mode, the current source 110 and the rest of the voltage interrupt circuit 100 are activated by other elements (not shown) on the control chip 46.

In this mode current is supplied to the actuator motor 54 by the FET 112 via the node 56.

Unless transistor 70 is triggered by overheating of circuit 53, the total amount supplied to actuator motor 54 is initially determined by the resistance of resistor 106 and the current supplied by current source 110. do.

When the temperature of transistor 70 is raised enough to turn on transistor 70, FET 98 turns on to diverge current from the emitter of transistor 108 to ground, effectively grounding the emitter.

Thus, the equilibrium potential of node 56 drops to one diode voltage drop (about 0.55V) above ground potential, that is, about one third of the equilibrium potential of FET 98.

Thus, the potential at node 56 drops sufficiently when transistor 70 is turned on, reducing the return circuit current supplied to actuator motor 54.

In this way, if the temperature rises due to an abnormal situation or other situation, the potential at both ends of the VCM is reduced to protect against overheating, but the inrush current due to the counter electromotive force or the timing of the head return operation of the VCM cannot be prevented.

Although current limiting is achieved by transistor 116 and resistor 114, the problem is that current can flow up to this current limit and the value must be large.

Accordingly, an object of the present invention is to provide a head return circuit of a hard disk drive for safely returning a head to a safe area by supplying a constant voltage again after supplying a constant current to the VCM. have.

1 is a block diagram of a conventional head return circuit having a magnitude of a constant current applied to a VCM in two stages.

2 is a block diagram of a conventional head return circuit for applying a constant voltage to the VCM.

3 is a circuit diagram of a head return circuit according to an embodiment of the present invention.

4 is an equivalent circuit diagram of a general VCM.

5 is a diagram illustrating a control signal according to a head return operation according to an embodiment of the present invention, and a current and a voltage applied to a VCM over time.

A feature of the present invention for achieving the above object is a head return circuit for returning a head for reading and writing information in a hard disk drive to a safe area, by supplying a constant current to the voice coil motor to move the head After causing the head to move to the safe area, the head is supplied to the voice coil motor when the head is moved to the safe area and positioned at a specific position.

The specific position is characterized in that the head is moved to the safety area and stopped momentarily, so that the counter electromotive force of the voice coil motor becomes zero.

Means for achieving the above features of the present invention comprises a spindle motor for constantly rotating the disk; A rectifier for full-wave rectifying and outputting current generated by the counter electromotive force of the spindle motor; A first capacitor connected between the output of the rectifier and ground; And a first constant current source connected between the capacitor and the voice coil motor.

Here, the voice coil motor is driven by the electric power charged in the first capacitor by the counter electromotive force of the spindle motor to cause a return operation of the head, and the first constant current until the head reaches the specific position. The current from the circle is supplied to the voice coil motor.

In addition, the means of the present invention includes a switch unit for interrupting the output of the rectifier by a head return request signal, an internal chip temperature rise signal of the hard disk drive, and a power on reset signal; A second constant current source connected to the switch unit, and a second capacitor connected to the second constant current source; An operational amplifier having a non-inverting terminal connected to a contact point of the second constant current source and the second capacitor and an inverting terminal connected to a reference voltage; And a first transistor connected to an output of the operational amplifier, a collector terminal connected to one terminal of the voice coil motor, and an emitter terminal grounded.

Here, the second constant current source when any one of the head return request signal, the internal chip temperature rise signal of the hard disk drive, and the power on reset signal is enabled to request return of the head to the safe area. Limiting the driving of the voice coil motor until the voltage charged in the second capacitor reaches the reference voltage.

In addition, the means of the present invention includes a first resistor to which one terminal is connected to the output of the rectifier; A second resistor connected between the other terminal of the first resistor and a ground; And a second transistor having a base terminal connected to the other terminal of the first resistor, a collector terminal connected to the first capacitor, and an emitter terminal connected to the other terminal of the voice coil motor.

Here, as soon as the head returns to the safe area and is located at the specific position, the second transistor is turned on and a constant voltage based on the voltage applied to the second resistor is supplied to the voice coil motor.

On the other hand, there is a specific relationship between the current supplied by the first constant current source and the current flowing through the first resistor based on the scaling factor determined inside the chip of the hard disk drive.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a circuit diagram of a head return circuit according to an embodiment of the present invention.

As shown in Figure 3, the head return circuit according to an embodiment of the present invention includes a SPM (SPindle Motor, 2100) for constantly rotating the disk; A rectifier 2200 for full-wave rectifying and outputting current generated by the back EMF of the SPM 2100; A diode D4 having a cathode terminal connected to the output of the rectifying unit 2200 and an anode terminal connected to the power supply voltage Vcc; A capacitor C1 connected between the cathode terminal of the diode D4 and ground; A transistor Q1 having a collector terminal connected to the cathode terminal of the diode D4; A constant current source Icrt connected between the cathode terminal of the diode D4 and the emitter terminal of the transistor Q1; A VCM 2300 having one side connected to an emitter terminal of the transistor Q1; A VCM driver 2400 connected between the emitter terminal of the transistor Q1 and the other terminal of the VCM 2300; A transistor Q2 having a collector terminal connected to the other terminal of the VCM 2300 and having an emitter terminal grounded; A resistor R1 connected between the base terminal of the transistor Q1 and ground; A resistor connected between the resistor R1 and the cathode terminal of the diode D4; A switch unit 2600 for receiving a head return signal Retract, a temperature rising signal TSD, and a power-on reset signal POR to interrupt a flow of current output from the rectifier 2200; A capacitor C2 having one terminal grounded; A constant current source Icret connected between the other terminal of the capacitor C2 and the output terminal of the switch unit 2600; And an operational amplifier 2500 having a non-inverting terminal connected to the other terminal of the capacitor C2, an inverting terminal connected to the reference voltage Vref1, and an output terminal connected to the base terminal of the transistor Q2.

Here, the rectifier 2200 is connected to three output terminals of the SPM 2100, respectively, and includes three diodes D1, D2, and D3 to which the output terminals are commonly connected.

In addition, the switch unit 2600 receives the head return signal Retract, the temperature rise signal TSD, and the power-on reset signal POR, and performs an AND operation on the AND gate 2610, and an AND gate 2610. And a switch S1 for controlling the connection of the rectifying unit 2200 and the constant current unit Icret according to the output of the control unit 2200.

Hereinafter, the head return circuit of the present invention will be described with reference to FIGS. 4 and 5.

First, when the hard disk drive operates normally, the switch S1 is not operated because the head return signal (Retract), the temperature rise signal (TSD), and the power on reset signal (POR) are not all enabled. Do not. Therefore, the VCM 2300 is normally driven by the VCM driver 2400.

However, a head return signal (Retract) when the normal head return is necessary, a temperature rise signal (TSD) when the user interface or the internal temperature of the chip rises, or a power-on reset signal to which a reset signal is applied from the power supply circuit ( When POR is enabled, the output signal Retract_on of the AND gate 2610 is enabled, and the switch S1 is turned on according to the signal to connect the output of the rectifier 2200 to the constant current unit Icret.

Referring to FIG. 5, when a head return is required, that is, a time point when the output signal Retract_on of the AND gate 2610 is enabled, t0 may be started. However, when the head return request, the VCM driver 2400 is turned off and the transistor Q2 is also turned off, so there is no current flowing through the VCM 2300. Therefore, head return does not start from time t0.

When the power supply to the SPM 2100 is cut off to return the head, back electromotive force is generated in the SPM 2100, and the current is supplied to the rectifier 2200, full-wave rectified, and supplied to the capacitor C1. From this time, the capacitor C1 starts to be charged, and when only the SPM 2100 is turned off without powering off the hard disk, the capacitor C1 is charged to the power supply voltage Vcc through the diode D4. The power charged in the capacitor C1 is used as a power source to retract the VCM 2300 when the transistor Q2 is later turned on.

On the other hand, when the switch S1 is turned on, the external capacitor C2 is charged by the current source Icret until it reaches a constant voltage. At this time, the constant voltage is determined by Vref1 connected to the inverting terminal of the operational amplifier 2500, where it is specified as 2.0V.

When the external capacitor C2 is charged to reach a predetermined voltage, that is, 2.0V or more, the output of the operational amplifier 2500 becomes high, thereby turning on the transistor Q2. The time at this time is t1.

As described above, when the transistor Q2 is turned on at the time t1 after a predetermined time elapses, the constant current Irct starts to flow to the VCM. At this time, the constant current Irct can be easily adjusted by the external resistor R1, and the constant current Irct is obtained by the following formula.

Here, Ki is about 300 as the scaling factor determined inside the chip, and Irct is linked to Iret. In other words, changing the Iret value also changes the Irct value.

Since current flows in the VCM 2300 at a time t1, the VCM 2300 moves the head to the safe area.

Meanwhile, referring to FIG. 4, the VCM 2300 may be represented by an equivalent circuit including a winding resistance R, an inductance L, and a counter electromotive force Vbemf of the VCM 2300.

If the voltage between a point and b point, that is, the voltage applied to the VCM 2300 is expressed in Vvcm, and the direction of the counter electromotive force is positive when the head moves to the safe area, the voltage across the VCM 2300 causes the transistor ( Since Q1) is off, the current flowing to the VCM 2300 is equal to the amount of current caused by the current source Irct, so that a constant current Irct flows into the VCM 2300 until the time t2 so that the voltage across the VCM 2300 becomes It will increase as the counter electromotive force increases. This amount of current graph is shown in FIG.

On the other hand, when the head reaches the safe area for the first time by the VCM 2300 after the time t1, when the constant current Icrt applied to the VCM 2300 is applied to the size that the head is stably stopped, the head stops at once. If the size of the constant current Icrt is increased in preparation for the return failure, bouncing may occur in which the head moves back from the safe area to the data area.

Therefore, when the head reaches the safe region at time t2, the VCM 2300 stops momentarily, so the back electromotive force of the VCM 2300 becomes zero, and the voltage across the VCM 2300 rapidly decreases. At this time, since the transistor Q1 is turned on due to the decrease in the voltage across the VCM 2300, the voltage at the point a is Vbe (the voltage between the base and the emitter of the transistor Q1, rather than the voltage Vc at the point c) (about 0.6). Controlled to be as small as V).

Therefore, after time t3 when the transistor Q1 is turned on, the constant voltage Vbe smaller than the voltage Vc at the point c is applied to the VCM 2300 so that the current flowing to the VCM 2300 Iretract = Vvcm / R = (Vc-Vbe) / R

This operation continues until time t4, after which a constant current, a constant voltage is applied to the VCM 2300.

The time periods t3 and t4 vary depending on the size of the constant current source, the magnitude of the counter electromotive force, and the timing of the head return operation. The peak value of the current flowing through the VCM 2300 also changes, but the magnitude of the counter electromotive force is zero when the VCM 2300 reaches the safety region. When switching to the constant voltage mode, the peak current is limited by the motor winding resistance (R).

Although the present invention has been described with reference to the most practical and preferred embodiments, the present invention is not limited to the above disclosed embodiments, but also includes various modifications and equivalents within the scope of the following claims.

In the conventional simple constant voltage control, if the head was moving to the safe area in the read and write mode at time t1, the current flowing to the VCM 2300 at time t1 flows much more peak current than when the counter electromotive force is zero. Therefore, in the present invention, since the instantaneous electromotive force of the VCM 2300 becomes zero or the first bounce is about to occur in the above-described manner, the constant current mode is automatically changed from the constant current mode to the constant voltage mode, thereby increasing the size of the initial constant current. Prevents head return failure, applies a constant voltage when the back electromotive force reaches zero, and instantaneously sufficient current is supplied to the VCM 2300, eliminating bouncing, but the magnitude of the instantaneous peak current is smaller than in the constant constant voltage mode. The current breakdown voltage can be reduced, making it stable and low cost.

Claims (8)

A head return circuit for returning a head for reading and writing information in a hard disk drive to a safe area, After supplying a constant current to the voice coil motor for moving the head to cause the head to move to the safe area, the head is moved to the safe area and momentarily stopped so that the counter electromotive force of the voice coil motor becomes zero. Supplying a constant voltage to the voice coil motor when Head return circuit of hard disk drive. delete The method of claim 1, A spindle motor in which the head return circuit rotates the disk constantly; A rectifier for full-wave rectifying and outputting current generated by the counter electromotive force of the spindle motor; A first capacitor connected between the output of the rectifier and ground; And a first constant current source connected between the capacitor and the voice coil motor, The voice coil motor is driven by the electric power charged in the first capacitor by the counter electromotive force of the spindle motor to cause a return operation of the head, and to the first constant current source until the head reaches the specific position. Current is supplied to the voice coil motor. Head return circuit of hard disk drive. The method of claim 3, A switch unit for interrupting the output of the rectifying unit by a head return request signal, an internal chip temperature rise signal of the hard disk drive, and a power-on reset signal; A second constant current source connected to the switch unit, and a second capacitor connected to the second constant current source; An operational amplifier having a non-inverting terminal connected to a contact point of the second constant current source and the second capacitor and an inverting terminal connected to a reference voltage; A first transistor connected to an output of the operational amplifier, a collector terminal connected to one terminal of the voice coil motor, and an emitter terminal grounded; The second constant current source when any one of the head return request signal, the internal chip temperature rise signal of the hard disk drive, and the power on reset signal is enabled to require return of the head to the safe area; Limiting the driving of the voice coil motor until the voltage charged in the second capacitor reaches the reference voltage. Head return circuit of hard disk drive. The method of claim 4, wherein A first resistor having one terminal connected to an output of the rectifier; A second resistor connected between the other terminal of the first resistor and a ground; A second transistor having a base terminal connected to the other terminal of the first resistor, a collector terminal connected to the first capacitor, and an emitter terminal connected to the other terminal of the voice coil motor; The second transistor is turned on and a constant voltage based on the voltage applied to the second resistor is supplied to the voice coil motor as soon as the head returns to the safe area and is located at the particular position. Head return circuit of hard disk drive. The method of claim 5, The current Irct supplied by the first constant current source is expressed as Where Ki is the scaling factor inside the hard disk drive chip, Iiret is a current flowing through the first resistor, Vref is the voltage across the first resistor, Riret is the resistance value of the first resistor, R1 is the resistance value of the second resistor Characterized in that Head return circuit of hard disk drive. The method of claim 3, And the rectifier (2200) includes three diodes each of which three spindle motors are connected to a phase output, and three diodes whose output terminals are commonly connected to each other. The method of claim 4, wherein An AND gate which receives the head return request signal, an internal chip temperature rise signal of the hard disk drive, a power-on reset signal, and performs an AND operation on the switch; A head return circuit of a hard disk drive, comprising a switch for interrupting a connection between constant current sources.