JP3930415B2 - Magnetic disk unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to current consumption control of a magnetic disk device, particularly a magnetic disk device connected to a computer by USB.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a magnetic disk device is known which is a flexible magnetic disk (hereinafter abbreviated as FD) device that is connected to a computer via USB and operates by receiving power supply from the computer via USB without receiving external power supply. ing. When receiving power supply from the host computer, the current consumption Ibus in the entire FD device needs to satisfy Ibus ≦ 500 mA.
[0003]
On the other hand, in recent years, even higher speed is required for a magnetic disk device, which is an FD device, and the rotational speed of a spindle motor (SPM) for rotationally driving the FD is changed from 300 rpm to 600 rpm (2 × speed), and further 1200 rpm (4 × speed). Therefore, current consumption in the FD device tends to increase. Therefore, it is necessary to reduce the current consumption while simultaneously increasing the speed as much as possible.
[0004]
It is to be noted that the magnetic disk device has a technology for switching to a high-speed rotation mode when power is supplied from a commercial power source, and switching to a low-speed rotation mode to reduce power consumption when power is supplied from a battery. It has been. Switching from the high-speed rotation mode to the low-speed rotation mode is performed by switching the number of turns of the U, V, and W phases of the DC pulse motor by turning on / off the transistor switch.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-162483 (pages 4 to 8)
[0006]
[Problems to be solved by the invention]
If the rotational load value (or moment of inertia) of the FD is within the allowable range, it is possible to suppress the current consumption to 500 mA or less even if the rotational drive is performed at 1200 rpm, but the specification of the rotational load value of the FD is strictly The current situation is that the rotational load value is different for each FD or for each manufacturer. For example, even if an FD having a large rotational load value (large moment of inertia) is driven at 1200 rpm, the restriction is 500 mA or less. There is a possibility that it cannot be driven by the conversion. In the above prior art, in the case of battery driving, the power consumption is reduced by switching to the low-speed rotation mode, but variations in the rotational load value of the magnetic disk to be driven are not taken into consideration.
[0007]
The present invention has been made in view of the above-described problems of the prior art, and its purpose is to drive a magnetic disk at high speed only by supplying power from a host computer even if the rotational load or moment of inertia of the magnetic disk varies. An object of the present invention is to provide a magnetic disk device that can be driven.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a magnetic disk device that is USB-connected to a computer and is driven by power supply from the computer via the USB, and a drive unit that rotationally drives the magnetic disk; It has a detection means for detecting the drive current of the drive means, and a control means for controlling the rotational speed of the drive means in accordance with the magnitude of the drive current. When the rotational load or moment of inertia of the magnetic disk is large, the drive current for driving the magnetic disk at a predetermined rotational speed also increases. In the present invention, paying attention to this fact, the rotational speed of the magnetic disk is controlled by evaluating the magnitude of the rotational load of the magnetic disk based on the drive current value. That is, according to the present invention, the rotational speed is adaptively controlled for each magnetic disk, and thereby, even when a magnetic disk with a large rotational load is driven, an increase in current consumption is suppressed, and driving by power supply from a computer is performed. Make it possible.
[0009]
The control means preferably reduces the rotational speed when the drive current exceeds a predetermined threshold value as compared with the case where the drive current is equal to or less than the threshold value. The required drive current can be reduced by reducing the rotation speed.
[0010]
And a head driving unit that drives a head that performs recording (or erasing) or reproduction with respect to the magnetic disk, and the detecting unit detects the driving current when the head driving unit is not driven. Is preferred. The current consumption of the entire magnetic disk device is almost determined by the SPM and the head drive means (stepping motor (STM), etc.), and the ratio of the drive current of the SPM to the total current consumption when the head drive means is in the non-drive state. Therefore, even if the rotational load of the magnetic disk is large and the drive current value increases, this can be detected and the rotation can be controlled.
[0011]
The drive means rotates the magnetic disk at a first rotation speed after the USB connection, and the detection means detects the drive current when driven at the first rotation speed, and performs the control When the drive current exceeds the predetermined threshold value, the means switches to a second rotation speed lower than the first rotation speed, and the drive current is equal to or less than the predetermined threshold value. It is also preferable to maintain and control the first rotational speed.
[0012]
The drive means can be constituted by a motor capable of switching the number of turns of the stator coil to a plurality of stages, for example, and the control means performs switching control so as to increase the number of turns of the motor when the predetermined threshold value is exceeded. be able to.
[0013]
The present invention also relates to a magnetic disk device that is connected to a computer via USB and is driven by power supply from the computer via the USB, the spindle motor driving the magnetic disk, and the stepping driving the recording / reproducing head. A motor, a circuit for distributing power from the computer to the spindle motor and the stepping motor, a comparison circuit for comparing a drive current of the spindle motor in a non-driven state with a predetermined threshold value, And a control circuit that reduces the drive current by reducing the rotation speed of the spindle motor when the drive current exceeds the threshold value in accordance with an output from the comparison circuit.
[0014]
Here, the spindle motor is, for example, a three-phase motor having a tap for switching the number of coil turns in each phase, and the control circuit switches the tap when the drive current exceeds the threshold value, It is preferred to increase the number of coil turns of the phase.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 shows a state in which an FD device, which is a magnetic disk device of this embodiment, is connected to a host computer (PC). The PC 1 and the FD device 10 are connected by a USB cable 5. As is well known, the USB cable 5 has a power line and a data line. The USB cable 5 supplies power to the FD device 10 through the power line, and supplies control signals and recording / reproduction data to the FD device 10 through the data line. As described above, the upper limit of the current consumption Ibus in the FD device 10 when operated by receiving the power supply from the PC 1 is 500 mA.
[0017]
The FD device 10 mainly includes a drive current detection unit 12, an SPM control unit 14, and an SPM 16. The drive current detection unit 12 detects a drive current value ISPM when the SPM 16 is driven by power supply from the PC 1 and compares the detected value with a predetermined threshold value. The comparison with the threshold value is for determining whether the rotational load value of the FD that is a magnetic disk is larger than the allowable rotational load value or whether the inertia moment of the FD is larger than the allowable inertia moment. The threshold value is set as appropriate. The drive current detection unit 12 outputs the result of comparison between the detected value and the threshold value to the SPM control unit 14.
[0018]
The SPM control unit 14 controls the rotation speed of the SPM 16 according to the comparison result signal from the drive current detection unit 12. Specifically, when the drive current value ISPM exceeds the threshold value, the rotational load or moment of inertia of the FD is greater than the allowable value, and the FD cannot be driven under the current consumption condition of 500 mA or less at the current rotational speed. Judgment is made and the SPM 16 is controlled to drive at a lower rotational speed than the current rotational speed. For example, when driving at a rotational speed of 1200 rpm (4 × speed), the speed is reduced to 600 rpm (2 × speed). As described above, the SPM control unit 14 controls the rotation speed of the SPM 16 according to the drive current value of the SPM 16.
[0019]
FIG. 2 shows a basic processing flowchart in the present embodiment. First, the FD device (USB FDD) 10 is connected to the PC 1 and power is supplied from the PC 1 to the FD device 10 via the USB cable 5 (S101). The SPM control unit 14 starts driving the SPM 16 at a predetermined rotation speed (for example, 1200 rpm), and the drive current detection unit 12 detects the drive current ISPM of the SPM 16 at that time (S102). The drive current ISPM of the SPM 16 is proportional to the rotational load (load torque) of the FD, and when the rotational load of the FD is large, the drive current ISPM for driving at a predetermined rotational speed also increases. If the rotational load of the FD is within the allowable range, the drive current ISPM is also less than or equal to the threshold value. However, if the rotational load of the FD exceeds the allowable range, the drive current ISPM also exceeds the threshold value, and the total current consumption value is 500 mA. The following conditions cannot be satisfied. Therefore, the drive current ISPM is compared with a threshold value (S103), and if it is equal to or less than the threshold value, it can be driven at the current rotation speed, and the current rotation speed (high-speed rotation) is maintained (S104). If it exceeds the value, the SPM 16 is driven at a rotational speed lower than the current rotational speed (S105). By driving at a low rotational speed, even if the rotational load of the FD is larger than the allowable value, the drive current decreases, and the FD can be driven under conditions of 500 mA or less by reducing the overall current consumption. .
[0020]
Hereinafter, the rotation speed control in the present embodiment will be described in more detail.
[0021]
FIG. 3 shows the relationship between the general load torque T and the rotational speed N of the SPM 16 and the relationship with the current consumption. In the figure, the horizontal axis represents the load torque T, and the vertical axis represents the rotational speed N. The case where the SPM 16 is driven at 600 rpm (double speed) and 1200 rpm (four times speed) is shown. When driven at quadruple speed, it is driven at the rotational speed N1 until the load torque T reaches T1, and when the load torque T becomes larger than T1, the rotational speed N decreases from N1. On the other hand, the current consumption increases in proportion to the load torque T. On the other hand, when driven at double speed, the load torque T is driven at the rotational speed N2 up to Tmax larger than T1, and the current consumption increases in proportion to the load torque T, but is smaller than in the case of quadruple speed.
[0022]
Therefore, if the load torque of the FD to be rotated is T1 or less, it can be driven at a quadruple speed, but if the load torque of the FD exceeds T1, it cannot be driven at the quadruple speed, and the load torque of the FD is Tmax. In other words, it must be driven at double speed, and switching to double speed can reduce current consumption compared to quadruple speed.
[0023]
FIG. 4 shows the relationship between the load torque T and the rotational speed N when the SPM controller 14 controls the SPM 16. Driving is performed at quadruple speed until the load torque T is T1, and when the load torque T exceeds T1, it is driven at double speed at which the maximum load torque is Tmax. As can be seen from FIG. 3, the current consumption can be suppressed by Δ as compared with the case of driving at the quadruple speed, and it can be driven only by the power source of the PC 1.
[0024]
In addition, when the load torque of FD becomes still larger than Tmax, it is also possible to drive at equal speed instead of double speed. In short, it is only necessary to automatically switch to the optimum double speed in accordance with the FD, thereby increasing the speed for each FD under the condition of 500 mA.
[0025]
In the above description, the rotational speed is switched and controlled in accordance with the drive current ISPM. However, the FD device 10 includes a stepping motor (STM) that drives a magnetic head that performs recording / reproduction on the FD in addition to the SPM 16. There is also current consumption in the control unit 14. Therefore, the total consumption current Ibus of the FD device 10 is obtained by using the drive current ISPM of the SPM 16, the drive current ISTM of the STM, and the consumption current ICC of the control unit.
[Expression 1]
Ibus = ISPM + ISTM + ICC
It becomes. The Ibus is maximized when the STM is driven (the magnetic head seeks) while the SPM 16 is driven. In the present embodiment, whether or not the FD has a large load is determined based on the magnitude of the drive current of the SPM 16, so that it is more convenient to detect a larger drive current when the STM is not driven. Therefore, it is desirable to detect the drive current when the STM is not driven. When the STM is in a non-driven state, for example, it is immediately after the FD device 10 is activated. When the STM is not driven, Ibus is accurately determined by ISTM and ICC, but ICC may be ignored because it is relatively small. Of course, it is also possible to detect ISPM + ICC and compare it with a threshold value (in this case, the threshold value can be set in consideration of ICC).
[0026]
FIG. 5 shows a detailed configuration diagram of the FD apparatus 10 in the present embodiment. The power from the power line Vbus of the USB cable 5 is distributed and supplied to the SPM 16 and STM 18. More precisely, power from Vbus is distributed to voltage Vspm to SPM 16, voltage Vcc / VDD to FDDLSI, and SVCC to control logic circuit. The SPM 16 and the STM 18 are controlled by the FDD LSI as the control unit 14.
[0027]
The drive current detection unit 12 includes resistors R1, R2, and R3 and a comparator, and is connected to Vbus. R1 has a small resistance value, and converts the current value between VD (input voltage) and VSPM (input voltage of SPM 16), that is, the drive current ISPM, into a potential difference and supplies it to the inverting input terminal of the comparator. On the other hand, a voltage obtained by dividing VD by resistors R2 and R3 is applied to the non-inverting input terminal of the comparator, and a threshold value is determined by R2 and R3. The comparator compares the voltage value of the drive current IsPM with the threshold voltage value, and outputs the comparison result as a Vs signal to the control logic circuit in the FDDLSI. Vs is Hi or Low, and when the drive current IsPM exceeds the threshold value, Low is output.
[0028]
The control logic circuit has an FDC (FD controller) and an FDMC (FD motion controller). The FDC records and erases data supplied from the PC 1 by switching and controlling the transfer rate for recording and erasing. At the same time, the data read from the FD is processed by a reproduction circuit including an amplifier, a filter, a comparator, and a TDF (time domain filter) and returned to the PC 1 side. The FDMC controls the rotational speed of the SPM 16 based on a control command from the FDC, and controls the seek operation of the STM 18. The FDC issues a command to the FDMC to drive the SPM 16 at quadruple speed if the Vs value input from the drive current detector 12 is Hi, and drives the SPM 16 at double speed if the Vs value is Low. Command to FDMC. Note that when the FDC switches from 4 × speed to 2 × speed according to the value of Vs, the transfer rate of the recording circuit (write circuit), erase circuit (erase circuit) and playback circuit is switched from 4 × speed to 2 × speed. Recording and playback.
[0029]
FIG. 6 shows a process flowchart in the configuration of FIG. First, when it is detected that an FD has been inserted (S201), the FDC instructs the FDMC to control the FD to be driven at quadruple speed (S202, S203). Then, it is confirmed that the STM 18 is not driven (S204), and it is determined whether or not the drive current of the SPM 16 when the STM 18 is not driven exceeds a threshold value (S205, S206). That is, the FDC determines whether or not the value of the output Vs from the drive current detection unit 12 is Low when the STM 18 drive command has not yet been issued to the FDMC and only the SPM 16 is driven. . If it is determined that Vs is Hi, that is, the drive current ISPM is less than or equal to the threshold value, the FDC and FDMC continue to control the SPM 16 at the current rotational speed (four times speed) (S207). On the other hand, when Vs is Low, that is, when the drive current ISPM exceeds the threshold value, the FDC and FDMC are controlled by switching the SPM 16 to double speed (S208).
[0030]
To switch from the 4 × speed to the 2 × speed, two types of coils for each phase on the stator side of the SPM 16 are prepared for high speed and low speed, and the high speed coil is switched to the low speed coil. The number of turns of the low speed coil is set larger than that of the high speed coil. Increasing the number of turns of the coil increases the magnetic flux density and increases the torque even with the same drive current. That is, an FD with a large load can be driven with a small drive current. However, when the number of turns of the coil increases, inductance loss occurs and the rotational speed decreases. This is why low speed control is used.
[0031]
When switching from the 4 × speed control to the 2 × speed control, the FDC further switches the parameter, that is, the transfer rate of each of the recording, reproducing, and erasing circuits to the 2 × speed (S209). With the above processing, when driving an FD with a large load, the 4 × speed is automatically switched to 2 × speed according to the drive current ISPM, and the total current consumption of the FD device 10 is reduced to 500 mA or less.
[0032]
FIG. 7 shows an equivalent circuit diagram of the stator coil of the SPM 16. The coils of U, V, W, and each phase are respectively composed of a first coil and a second coil, and taps TUH, TVH, and TWH for high speed control are formed between the first coil and the second coil, respectively. . In quadruple speed control, the high speed control tap is used to drive using only the first coil in each phase. In double speed control, the low speed control taps TUL, TVL, TWL are switched to the first coil and the second coil. To drive. It is of course possible to switch the number of turns of the coil by turning on / off the transistor switch as in the prior art instead of switching the tap.
[0033]
FIG. 8 shows the configuration of the stator coil of the SPM 16. A low-speed rotating coil and a high-speed rotating coil are wound around a U-phase, V-phase, and W-phase stator core, respectively. The low-speed rotating coil is one reciprocating winding from the base to the tip of the pole of the stator core (winding from the root to the tip, and further from the tip to the root), and the high-speed rotating coil is the low-speed rotating coil. Is a reciprocating winding from the middle of the pole of the stator core to the tip. Therefore, (the number of turns of the low-speed rotating coil)> (the number of turns of the high-speed rotating coil). The U-phase, V-phase, and W-phase of the low-speed rotation coil and the high-speed rotation coil are star-connected at neutral points, and a low-speed rotation tap and a high-speed rotation tap are formed. The FDMC drives a high-speed rotation coil using a high-speed rotation tap immediately after the operation of the FD apparatus 10 based on a command from the FDC, and drives the FD at a quadruple speed. Based on the switching command from the FDC, the high-speed rotation tap is switched to the low-speed rotation tap to drive the low-speed rotation coil, and the FD is driven at double speed.
[0034]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.
[0035]
For example, in this embodiment, as shown in FIG. 5, the drive current detection unit 12 is configured by resistors R1 to R3 and a comparator, and the drive current is converted into a voltage value and compared with a threshold voltage. It can be configured. A configuration example of the drive current detection unit 12 is shown below.
[0036]
FIG. 9 shows a case where the drive current detection unit 12 includes an operational amplifier 12a and a grounded emitter transistor 12b. The operational amplifier 12a converts the drive current ISPM into a voltage value, applies the voltage value to the base of the transistor 12b, and outputs the collector voltage as Vs to the control logic circuit. If the drive current IsPM is less than or equal to the threshold value, the transistor 12b is OFF and Vs remains Hi. If the drive current ISPM exceeds the threshold value, the transistor 12b is turned ON and Vs becomes Low.
[0037]
FIG. 10 shows a case where the drive current detection unit 12 includes an operational amplifier 12a, a low-pass filter LPF 12c, and a comparator 12d. As in FIG. 9, the operational amplifier 12a converts the drive current Ispm into a voltage value. However, since the drive current may vary due to noise, the low-pass filter 12c removes the noise, and then the comparator 12d sets the threshold value. Compare. The output of the comparator 12d is output to the control logic circuit as Vs.
[0038]
In this embodiment, in the case of an FD with a large load, the rotational speed is switched from 4 × speed to 2 × speed. More generally, the FD is first driven at the first rotational speed, and driving at that time is performed. When the current exceeds the threshold value, the FD can be driven at a second rotation speed lower than the first rotation speed. If the drive current when the FD is driven at the second rotational speed still exceeds the threshold value, the FD may be driven at a third rotational speed that is lower than the second rotational speed.
[0039]
【The invention's effect】
As described above, according to the present invention, even if there are variations in the magnetic disk, the rotational speed is adaptively controlled for each magnetic disk, so that the magnetic disk can be driven at high speed only by supplying power from the host computer. it can.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a connection state between a computer and an FD device.
FIG. 2 is a basic processing flowchart of the FD apparatus.
FIG. 3 is a graph showing torque characteristics of SPM.
FIG. 4 is a graph showing torque characteristics of the embodiment.
FIG. 5 is a configuration block diagram of the FD device.
FIG. 6 is a detailed process flowchart of the FD apparatus.
FIG. 7 is an equivalent circuit diagram of an SPM stator coil.
FIG. 8 is a configuration diagram of an SPM stator coil.
FIG. 9 is another configuration diagram of the drive current detector shown in FIG. 5;
FIG. 10 is still another configuration diagram of the drive current detection unit shown in FIG. 5;
[Explanation of symbols]
1 Computer (PC), 5 USB cable, 10 FD device.

Claims (7)

A magnetic disk device connected to a computer via USB and driven by power supply from the computer via the USB,
Drive means for rotationally driving the magnetic disk;
Detecting means for detecting a driving current of the driving means;
Control means for controlling the rotational speed of the drive means according to the magnitude of the drive current;
A magnetic disk device comprising: The apparatus of claim 1.
The magnetic disk apparatus according to claim 1, wherein the control means reduces the rotational speed when the drive current exceeds a predetermined threshold value as compared with a case where the drive current is equal to or less than the threshold value. The apparatus of claim 1, further comprising:
Head driving means for driving a head for recording or reproducing with respect to the magnetic disk;
Have
The magnetic disk apparatus according to claim 1, wherein the detecting means detects the driving current when the head driving means is not driven. The apparatus of claim 1.
The drive means rotationally drives the magnetic disk at a first rotational speed after the USB connection,
The detection means detects the drive current when driven at the first rotational speed;
The control means switches to a second rotation speed lower than the first rotation speed when the drive current exceeds the predetermined threshold value, and the drive current is equal to or less than the predetermined threshold value. In this case, the magnetic disk apparatus is controlled to maintain the first rotational speed. In the apparatus in any one of Claims 1-4,
The drive means is a motor capable of switching the number of turns of the stator coil to a plurality of stages,
The magnetic disk device according to claim 1, wherein the control means performs switching control so as to increase the number of turns of the motor when the predetermined threshold value is exceeded. A magnetic disk device connected to a computer via USB and driven by power supply from the computer via the USB,
A spindle motor that drives a magnetic disk;
A stepping motor for driving the recording / reproducing head;
A circuit for distributing power from the computer to the spindle motor and the stepping motor;
A comparison circuit that compares the drive current of the spindle motor when the stepping motor is not driven with a predetermined threshold;
A control circuit for reducing the drive current by reducing the rotation speed of the spindle motor when the drive current exceeds the threshold value according to an output from the comparison circuit;
A magnetic disk device comprising: The apparatus of claim 6.
The spindle motor is a three-phase motor having a tap for switching the number of coil turns in each phase,
The control circuit switches the tap to increase the number of coil turns of each phase when the drive current exceeds the threshold value.

Images