JPH11213526A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably keep the output of a Hall element. SOLUTION: A magnetic sensor having a Hall element circuit 62 of a constant-current system is provided with a low-pass filter 66 between a positive electrode terminal 62a and a positive electric power source terminal VA to which an electric power source voltage VCC is supplied. The low-pass filter 66 is an RC low-pass filter consisting of a resistor R21 of which one end is connected with a positive power source terminal VA and a capacitor C2 1 inserted between the other end of the resistor R2 1 and the earth terminal. The resistor R2 1 has, for example, a resistance value of 130 Ω, and the capacitor C2 1 has, for example, a capacitance value of 0.1 μF.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hall element circuit including at least one hall element used in a floppy disk drive and used for controlling a spindle motor for rotatingly driving a floppy disk inserted therein. And a magnetic sensor having the same.

[0002]

2. Description of the Related Art As is well known, a floppy disk drive (hereinafter abbreviated as FDD) records data on a disk-shaped magnetic recording medium of a floppy disk (hereinafter abbreviated as FD) inserted therein. This is a device for performing reproduction. Such a floppy disk drive is mounted on a portable electronic device such as a laptop personal computer, a notebook personal computer, or a notebook word processor.

[0003] This type of floppy disk drive is
A magnetic head for reading / writing data from / to a magnetic recording medium of a floppy disk, a carriage assembly for supporting the magnetic head at a tip thereof movably along a predetermined radial direction with respect to the floppy disk, and the carriage assembly And a spindle motor for rotating a magnetic recording medium while holding a floppy disk.

[0004] Various FDD control devices for controlling such a floppy disk drive have been proposed. For example, Japanese Patent Application Laid-Open No. 9-97493 discloses that
A read / write system (hereinafter referred to as R / W system) control circuit for reading / writing the data, and a stepping motor system (hereinafter referred to as STP system) control circuit for controlling driving of the stepping motor. And a control system (hereinafter, referred to as a CTL system) control circuit for controlling the operation of the entire floppy disk drive.
Disclosed therein. This one chip I
C is generally a MOS integrated with a large number of MOSFETs.
It is realized by an IC.

[0005] The above-mentioned FDD control device uses this one-chip IC.
In addition, a spindle motor IC for controlling the driving of the spindle motor is provided. This IC is realized by a bipolar IC in which a large number of bipolar transistors are integrated.

[0006] The specifications of the FDD differ depending on the customer. For example, Drive Select 0 or 1, with or without special seek function, with or without auto chucking function, Dens
Logic difference of ityOut signal, logic difference of mode select signal, 1M mode 250 kbps or 300 kbps. If one-chip ICs are developed for each specification so as to satisfy this specification, various types of one-chip ICs must be prepared. In order to avoid this, all the functions that satisfy all the specifications are incorporated in the 1-chip IC in advance, and the functions are selected according to the specifications. It has been proposed (see, for example, JP-A-9-97839).

On the other hand, as is well known, an FD driven by the FDD includes a disk-shaped magnetic recording medium accessed by a magnetic head, and data is written on a surface of the magnetic recording medium in a radial direction. A plurality of tracks as recording paths are formed concentrically. The number of tracks of the FD is 80 on one side, and is from the outermost track TR00 to the innermost track TR79. Here, the outermost track TR00 is referred to as an outermost track.

When the FD is accessed by the FDD magnetic head, it is necessary to position the magnetic head at a desired track position. For this purpose, the carriage assembly supporting the magnetic head at the tip may be positioned. Since a stepping motor is used as a driving means of the carriage assembly, the positioning of the carriage assembly can be easily performed in the FDD. Nevertheless, in the FDD, it is necessary to detect only the position of the outermost track TR00 of the magnetic recording medium of the FD inserted therein. In order to detect the position of the outermost track TR00, the carriage assembly is provided with a blocking plate projecting downward from the bottom thereof, and a photo interrupter is attached to a substrate close to the main frame facing the carriage assembly. (See, for example, JP-A-9-91859). That is, by blocking the optical path of the photo interrupter with the blocking plate, it is possible to detect that the magnetic head is at the position of the outermost track TR00 of the FD magnetic recording medium. Such a track position detection mechanism,
In this technical field, it is called "00 sensor".

A magnetic sensor (rotor position detector) is used to control the spindle motor.
A Hall element is generally used as the detection element.
A spindle motor using such a Hall element is also called a “Hall motor”. As is well known, the “Hall effect” refers to a phenomenon that when a magnetic field is applied to a current flowing in a conductor in a direction perpendicular to the conductor, an electromotive force is generated in a direction perpendicular to each of the current and the magnetic field. In the applied semiconductor device, a voltage generated at that time is called a Hall voltage. That is, the Hall element is an element that changes a magnetic field to a voltage.

A conventional magnetic sensor (rotor position detector) will be described with reference to FIGS. The magnetic sensor includes a Hall element circuit including at least one Hall element. There are two types of Hall element circuits. That is, there are a constant current method and a constant voltage method as a method of using the Hall element. FIG. 10 shows a rotor position detector including a Hall element circuit 62 of a constant current type, and FIG. 11 shows a rotor position detector including a Hall element circuit 64 of a constant voltage type.

As shown in FIG. 10, the Hall element circuit 62 of the constant current system is a circuit in which three Hall elements 606, 607 and 608 are connected in series. On the other hand, as shown in FIG. 11, the constant voltage type Hall element circuit 64 is a circuit in which three Hall elements 606 to 608 are connected in parallel. Each of the Hall elements 606 to 608 has a positive side and a negative side.
And a pair of signal output terminals connected to an input terminal of a spindle motor IC (not shown).

In FIG. 10, a constant current type Hall element circuit 62 has a positive electrode terminal 62p and a negative electrode terminal 62n. Resistor R ₂₁ between the positive power supply terminal to which a positive electrode terminal 62p and the power supply voltage Vcc is supplied is provided, the negative electrode terminal 6
It is resistor R ₂₂ is provided between the 2n and the ground terminal. These resistors R ₂₁ and R ₂₂ are biasing resistors for adjusting the current and common mode input voltage. The magnetic sensor employing the constant current type Hall element circuit 62 having such a configuration has the advantage that the current values flowing through the three Hall elements 606 to 608 are the same, and output variations are eliminated. However, since there is a possibility that the breaking of the Hall element is generated, it is necessary to set to an appropriate probability of the current value of the current flowing through the Hall element circuit 62 in the bias resistors R ₂₁ and R _22.

Similarly, in FIG. 11, a constant voltage type Hall element circuit 64 includes a positive electrode terminal 64p and a negative electrode terminal 64p.
and n. Resistor R ₂₁ between the positive power supply terminal to which a positive electrode terminal 64p and the power supply voltage Vcc is supplied, to which a resistor R ₂₂ is provided between the ground terminal negative electrode terminal 64n. These resistors R ₂₁ and R ₂₂ are biasing resistors for adjusting the current and common mode input voltage. The Hall element circuit 64 of the constant voltage type having such a configuration.
In the magnetic sensor adopting the above, since the current value is determined by the internal resistance of the Hall element, it is necessary to unify the rank of the Hall element. Also, the current consumption is three times as large as that of the constant current type. However, there is an advantage that the output is larger than that of the constant current type.

Next, adjustment of the common mode input voltage will be described. The signal output from the Hall element circuit 62 or 64 when inputting to the spindle motor IC must be in the range of 1.5 V to (Vcc-1 V) at DC level. In order to adjust this, bias resistors R ₂₁ and R ₂₂ are provided, and D
The C level has been determined.

A Hall element is also used as a magnetic sensor for detecting an index.

[0016]

In a floppy disk drive, noise having a high-frequency component is often superimposed on a power supply line for supplying a power supply voltage Vcc. When noise is superimposed on the power supply line, the output from the Hall element circuit of the magnetic sensor shown in FIGS. 10 and 11 is not stabilized, and as a result, the spindle motor IC using such a magnetic sensor malfunctions. There is.

Next, this problem will be described in some detail. As described above, the Hall element has a pair of + and-signal output terminals. In the spindle motor IC, signals from the pair of signal output terminals are processed differentially.
On the other hand, the noise superimposed on the power supply line is output to the pair of signal output terminals of the Hall element in the same phase. However, +
If there is a difference in the pattern capacitance between the signal output terminal on the negative side and the signal output terminal on the negative side, a phase shift occurs. In general, there is usually a difference between such pattern capacities. In such a case, the spindle motor IC cannot cancel the phase-shifted noise, and malfunctions with the output waveform due to the influence of the noise. Therefore, some measure is required to stabilize the output from the Hall element circuit of the magnetic sensor.

Therefore, an object of the present invention is to provide a magnetic sensor which can always keep the output from the Hall element stable.

[0019]

According to the present invention, a spindle motor for rotating a magnetic recording medium of a floppy disk in a floppy disk drive for driving an inserted floppy disk is controlled. A magnetic sensor having at least one Hall element circuit, wherein the Hall element circuit has a positive electrode terminal and a negative electrode terminal, and has a positive electrode terminal and a positive electrode terminal. A magnetic sensor characterized by providing a low-pass filter between the power supply terminal and the power supply terminal is obtained.

[0020]

By forming a low-pass filter between the positive power supply terminal and the Hall element circuit, high-frequency component noise superimposed on the power supply line is removed, and the output of the Hall element is kept stable.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

First, with reference to FIGS. 3 and 4, a description will be given of a 3.5-inch floppy disk drive to which a magnetic sensor according to the present invention is applied and which can be mounted on a portable electronic device. FIG. 3 is an exploded perspective view, and FIG. 4 is a perspective view seen from the front side.

The floppy disk drive shown in FIG.
This is a device for driving a 3.5-inch floppy disk (described later). The inserted floppy disk is inserted into the floppy disk drive from the direction shown by the arrow A in FIGS. The inserted floppy disk is placed on the disk table 11 on its rotating shaft 1.
1a and the center axis of the floppy disk are held in alignment. The rotating shaft 11a of the disk table 11 is connected to a bearing 1 provided on a frame 13 via a spring 12.
3a, whereby the disk table 11 is rotatably supported on the surface of the frame 13. Therefore, the axial direction B of the rotating shaft 11a of the disk table 11
Is parallel to the thickness direction of the frame 13. The disk table 11 is driven to rotate by a spindle motor (not shown) provided on the back surface of the frame 13.
Thereby, the magnetic recording medium of the floppy disk rotates. A board (not shown) on which a large number of electronic components are mounted is attached to the back surface of the frame 13.

The floppy disk drive has a pair of upper and lower magnetic heads 14 (only the upper magnetic head is shown) for reading / writing data from / to a magnetic recording medium of a floppy disk. Magnetic head 14
Is supported at its tip by a carriage assembly 15 provided on the back side of the floppy disk drive. That is, the carriage assembly 15 has an upper carriage 15U that supports the upper magnetic head 14, and a lower carriage 15L that supports the lower magnetic head. The carriage assembly 15 is disposed on the surface of the frame 13 so as to be separated from the frame 13 as described later, and moves the magnetic head 14 at a tip thereof in a predetermined radial direction with respect to the floppy disk (arrows in FIGS. (Direction indicated by C).

The side wall 131 on the rear side of the frame 13
, A stepping motor 16 is fixed. The stepping motor 16 drives the carriage assembly 15 linearly in a predetermined radial direction C. More specifically, the stepping motor 16 has a rotating shaft (drive shaft) 161 extending parallel to a predetermined radial direction C, and the rotating shaft 161 is provided with a male screw. This rotating shaft 161
The tip 132a of the hole 132a is formed in a bent portion 132 which is cut and raised from the surface of the frame 13.
And a steel ball 162 is provided. The rotation shaft 1 is formed by the hole 132a and the steel ball 162.
61 is regulated so as to extend in parallel with a predetermined radial direction C, and its tip 161a is rotatably held.

On the other hand, the carriage assembly 15 has an arm 151 extending from the lower carriage 15L to the rotation shaft 161. The tip 151a of this arm 151 engages with the male screw root of the rotation shaft 161. . Therefore, when the rotation shaft 161 of the stepping motor 16 rotates, the tip 151a of the arm 151 is moved along the valley portion of the male screw of the rotation shaft 161, whereby the carriage assembly 15 itself moves in the predetermined radial direction C. Move. In any case, the stepping motor 16 functions as a driving unit for linearly moving the carriage assembly 15 in the predetermined radial direction C.

Since the rotating shaft 161 of the stepping motor 16 is provided on one side of the carriage assembly 15, one side of the carriage assembly 15 is movably supported by the rotating shaft 161 while being separated from the frame 13. Is done. However, this rotating shaft 161
Cannot support the entire carriage assembly 15 apart from the surface of the frame 13. For this reason, the guide bar 17 guides the carriage assembly 15 while supporting the carriage assembly 15 on the other side. The guide bar 17 is provided on the opposite side of the rotation shaft 161 of the stepping motor 16 with the carriage assembly 15 interposed therebetween. Guide bar 1
7 extends parallel to a predetermined radial direction C, and one end 171 and the other end 172 are fixed on the surface of the frame 13 as described later, and guide the carriage assembly 15 along the predetermined radial direction C. . As a result, the entire carriage assembly 15 is disposed apart from the surface of the frame 13.

A flexible printed circuit (FPC) 152 extends from the carriage assembly 15 to the guide bar 17 side.
2 is electrically connected to a substrate attached to the back surface of the frame 13.

The guide bar 17 is held by a guide bar clamp 18 on the surface of the frame 13. The guide bar clamp 18 is fixed to the surface of the frame 13 at the center thereof by means of a binding screw 19. More specifically, the guide bar clamp 18 has a rectangular fixing member 180 that is slightly longer than the guide bar 17, and the screw shaft 1 of the bind screw 19 is provided substantially at the center of the rectangular fixing member 180.
A hole 180a is formed so that the hole 90 can pass through.
A pair of arms 181 and 182 for holding one end 180b and the other end 172 of the rectangular fixing member 180 extend.

Since the guide bar clamp 18 simply holds the guide bar 17, the guide bar 17 cannot be fixed to the surface of the frame 13 by this alone. For this purpose, both ends 171 and 1
A pair of positioning members for regulating the position of 72 are required. The pair of positioning members include a frame 1
A pair of bent portions 201 and 202 formed by cutting and raising a part of 3 on the surface side of the frame 13 are used.

The lower carriage 15L of the carriage assembly 15 connects the carriage assembly 15 to the guide bar 1.
It also functions as a support frame that slidably supports along 7. The lower carriage 15L has a protruding portion (not shown) protruding toward the guide bar 17 side.
Are slidably fitted.

The floppy disk drive further has an eject plate 21 and a disk holder 22.
The frame 13, the eject plate 21, and the disk holder 22 are formed by punching, pressing, bending, or the like on a metal plate.

The eject plate 21 is provided on the frame 13 so as to be slidable along the direction A of inserting the floppy disk and the opposite direction. The eject plate 21 holds the floppy disk in cooperation with the disk holder 22 when the floppy disk drive operates, as described later. Further, the eject plate 21 enables the floppy disk to be inserted into the floppy disk drive along the insertion direction A, or allows the floppy disk to be removed from the floppy disk drive along the direction opposite to the insertion direction A. To enable this, the floppy disk is held so that it can slide along the insertion direction A. A pair of side walls 210 facing each other are formed on the eject plate 21. This side wall 210
Are formed with a pair of cam portions 211. Further, both side walls 210 are provided on the bottom surface of the eject plate 21.
A notch 213 is formed along the bottom surface of the eject plate 21 so as to surround the disc table 11. Further, a pin (described later) is provided on the lower surface of the eject plate 21, and this pin engages with a locking portion of an eject lever described later.

The disk holder 22 is disposed on the eject plate 21. In the disk holder 22,
A main surface 220 and a pair of side walls 221 facing each other at both ends of the main surface 220 are formed. Protrusions 222 (only one is shown) are formed on both side walls 221. These protruding pieces 222 are connected to the holes 1 of the frame 13 through the cutouts 212 of the eject plate 21.
33. The protrusion 222 is inserted into the hole 133 of the frame 13 so that the disk holder 2
2, the position of the insertion direction A with respect to the frame 13 is determined, and at the same time, the disk holder 22 can reciprocate along the axial direction B of the rotating shaft 11 a of the disk table 11. A pair of pins 2 is provided on each of the side walls 221.
23 are provided. This pin 223 is inserted into a cam portion 211 formed on the side wall 210 of the eject plate 21. An eject spring 23 is provided between the disc holder 22 and the eject plate 21.

In this embodiment, the projection 222 is provided on the disk holder 22 and the hole 133 is provided on the frame 133. However, the present invention is not limited to this, and the projection may be provided on the frame and the hole may be provided on the disk holder. I do not care.

The disk holder 22 has a substantially rectangular opening extending in a predetermined radial direction C at a position corresponding to the upper carriage 15U of the carriage assembly 15 in a central portion on the back side in the insertion direction A. 224 are provided. The periphery of the opening 224 is raised upward from the main surface 220 of the disk holder 22 around the opening 224.
A substantially U-shaped raised edge 225 is formed. On the other hand, the carriage assembly 15 includes a pair of side arms 153 extending laterally, and the side arms 153 are located above the rising edge 225. As will be described later, when the floppy disk is ejected from the disk holder 22, the side arm 153 engages with the raised edge 225, thereby causing the pair of upper and lower magnetic heads 1 to move.
4 are separated from each other. Further, the disk holder 22
Also has an opening 226 shaped to allow rotation of a later-described eject lever lever from the opening 224 to the right on the back side in the insertion direction A.

An eject lever 24 is rotatably provided on the frame 13 near the carriage assembly 15. More specifically, the frame 13 has a rod-shaped pin 134 that extends upward from the surface thereof. The eject lever 24 includes a tubular portion 240 into which the rod-shaped pin 134 is fitted, an arm portion (lever portion) 241 extending in a radial direction from the tubular portion 240, and an upper portion provided at a free end of the arm portion 241. Projection 2 extending to
42 and an arc-shaped locking portion 243 extending in the circumferential direction from the free end side of the arm portion 241. An eject lever spring 25 is attached to the eject lever 24 around the cylindrical portion 240, and the eject lever spring 25
The eject lever 24 is urged counterclockwise in the drawing. The protrusion 242 of the eject lever 24 is loosely fitted in the opening 226 of the disc holder 22. The projection 242 is engaged with a right upper edge of a shutter of a floppy disk described later to control opening and closing of the shutter. In addition, as shown in FIG.
A screw 26 is screwed into the end of the rod 34, thereby preventing the eject lever 24 from coming off the rod-shaped pin 134.

A front panel 27 is attached to the front end of the frame 13. Front panel 2
7 is an opening 271 for inserting and removing a floppy disk.
And a door 272 that opens and closes the opening 271. The front panel 27 includes an eject button 2
8 is provided so as to be movable in the front-rear direction. The eject button 28 is fitted into a protrusion 214 that projects forward at the front end of the eject plate 21.

Referring to FIG. 5, a floppy disk (FD) driven by the floppy disk drive (FDD) shown in FIGS. 2 and 3 will be described.
The illustrated floppy disk 40 includes a disk-shaped magnetic recording medium 41, a shell 42 that covers the magnetic recording medium 41,
And a shutter 43 slidable in the direction of arrow D. The shutter 43 has a window 43a. Shutter 43
Is urged by a spring member (not shown) in a direction opposite to the arrow D direction. The shell 42 has an opening 42a that allows the magnetic head 14 of the floppy disk drive to access the magnetic recording medium 41. When the floppy disk 40 is not inserted into the floppy disk drive, the opening 42a is covered with a shutter 43 as shown in the figure. When the floppy disk 40 is inserted into the floppy disk drive, the protrusion 242 of the eject lever 24 engages the upper right edge 43b of the shutter 43, and slides the shutter 43 in the direction of arrow D.

The shell 42 has a chamfered portion 42b at the upper right corner for preventing reverse insertion (insertion with the front and back and the insertion direction reversed).
Are formed. Further, a write protection hole 44 is formed in the shell 42 at the left corner at the rear end in the insertion direction A.

As described above, in the floppy disk 40 driven by the floppy disk drive, the magnetic recording medium 41 accessed by the magnetic head 14
A plurality of tracks (not shown) as paths for recording data are formed concentrically along the radial direction. The number of tracks of the floppy disk 40 is 80 on one side, and is from the outermost track (most end track) TR00 to the innermost track TR79.

Referring to FIG. 6 in addition to FIG. 3, a track position detecting mechanism (00 sensor) for detecting the position of the outermost track TR00 of the magnetic recording medium 41 will be described.

In the carriage assembly 15, the lower carriage 15L is provided with a blocking plate 154 projecting downward from the bottom thereof. On the other hand, a main printed circuit board 30 is disposed on the lower surface side of the main frame 13 facing the carriage assembly 15, and a photo interrupter 31 used as a track position detecting mechanism (00 sensor) is provided on the main printed circuit board 30. Has been implemented. For this reason, a hole 13b for passing the photo interrupter 31 is formed in the main frame 13.

As is well known, the photo interrupter 31
Is a first protruding portion 3 in which a light emitting element (described later) is incorporated.
11 and a second protrusion 312 in which a light receiving element (described later) is built. The first protrusion 311 and the second protrusion 312 are arranged so as to face each other as shown in the drawing, and an opening (not shown) is provided on each facing wall surface. An optical path from the light emitting element to the light receiving element is formed through these two openings. Then, the blocking plate 154 passes through a passage between the first protrusion 311 and the second protrusion 312 as illustrated.

In the 00 sensor having such a configuration, the optical path of the photo-interrupter 31 is blocked by the blocking plate 154, so that the magnetic head 14 is connected to the floppy disk 40.
Can be detected at the position of the outermost track TR00 of the magnetic recording medium 41.

Referring to FIGS. 7 and 8, an FDD control device for controlling the floppy disk drive (FDD) shown in FIGS. 3 and 4 will be described.

The illustrated FDD control device has a one-chip IC 5
0 (FIG. 7) and the spindle motor IC 60 (FIG. 8)
And a power supply circuit 80. These one-chip ICs
The 50, the spindle motor IC 60, and the power supply circuit 80 are mounted on the main printed circuit board 30 (FIG. 6). The spindle motor IC 60 is an IC for controlling the driving of the spindle motor, and is realized by a bipolar IC in which a large number of bipolar transistors are integrated. On the other hand, the one-chip IC 50 has a large number of MOS transistors.
This is realized by a MOS IC in which FETs are integrated. The power supply circuit 80 is a circuit for supplying a voltage of 5 V when a power switch (not shown) is turned on, and has a first power terminal VA and a second power terminal VB.

Referring to FIG. 9 in addition to FIG. 7, one-chip IC 50 has R / W control circuit 51, STP control circuit 52, and CTL control circuit 53 incorporated therein. The R / W system control circuit 51 is a control circuit for reading / writing data. The STP control circuit 52 is a control circuit for controlling the driving of the stepping motor 16 (FIG. 3). The CTL control circuit 53 is a control circuit for controlling the operation of the entire floppy disk drive, and is also called a logic circuit. 1-chip IC50
Represents the function selection circuit 54 described above and the host I / F circuit 5
5 and a spindle motor control I / F circuit 56. The CTL control circuit 53 includes an R / W control circuit 51, an STP control circuit 52, a function selection circuit 54, a host I / F circuit 55, and a spindle motor control I / F.
It is connected to the F circuit 56.

The R / W control circuit 51 is connected to the upper magnetic head 14 (FIG. 3) and the lower magnetic head via a HEAD1 line 71 and a HEAD0 line 72, respectively. The STP system control circuit 52 is S-MOT
It is connected to the stepping motor 16 (FIG. 3) via the OR line 73. The host I / F circuit 55 has an I / F
It is connected to a host system (not shown) via the F line 74. I / F circuit 56 for spindle motor control
Is the spindle motor IC 6 via the FFC line 75
Connected to 0.

Next, the input / output terminals of the one-chip IC 50 will be described. One-chip IC 50 has R / W output terminals (ER1, RW1A, RW1B, ER0, RW) connected to HEAD1 line 71 and HEAD0 line 72.
0A, RW0B, and VCC (R)). One chip 1C50 has STP output terminals (ST1, ST1B, ST4, ST4) connected to the S-MOTOR line 73.
B). Further, the one-chip IC 50 includes a host input / output terminal (DCO, S1) connected to the I / F line 74.
I, RDO, WPO, TKO, WGI, WDI, ST
P, DIR, MTI, DSI, ID0, HDOO, HD
IS). The one-chip IC 50 has an FFC line 75
Motor control input / output terminal (ID
I, MTO, 360, HDI3, HDI, DSO, DK
I, WPI, 1MCLK). In addition to these input / output terminals, the one-chip IC 50 has two function selection input terminals (1M36 / HDOS / WPOS, ACHS / DSS /
DRS) and three input terminals (AMP /
FIL, TKI, TKS).

The photo interrupter 31 operating as the 00 sensor is a light emitting diode (LED) as a light emitting element.
31a and a phototransistor 31b as a light receiving element. The anode of the LED 31a is connected to the first power supply terminal V
A, and the cathode is connected to the TKS terminal of the one-chip IC 50. The collector of the phototransistor 31b is connected to the first power supply terminal VA. The emitter of the phototransistor 31b will is grounded through a resistor R _4, is connected to the TKI terminal of one chip IC50 and AMP / FIL terminal.

Referring to FIG. 8, IC for spindle motor
The spindle motor controlled by the U-phase, the V-phase, and the W-phase
Phase three coils (stator windings) 601, 602, 60
3 is a brushless three-phase DC motor. The spindle motor includes a permanent magnet type rotor (not shown),
A rotor position detector (to be described later). on the other hand,
The spindle motor IC 60 includes a drive transistor (transistor commutator) including a plurality of bipolar transistors. In other words, the spindle motor turns on and off the bipolar transistor of the drive transistor according to the rotor position of this motor, passes current through the corresponding stator winding, and generates torque between the rotor magnetic poles. , Rotate the rotor. With the rotation of the rotor, the rotor position detection signal output from the rotor position detector is also sequentially switched, and the stator winding through which current flows is switched to maintain the rotation.

The spindle motor has a frequency generation pattern F for detecting the rotation speed (rotation speed) of the rotor.
Has GPT. The spindle motor IC 60 switches the stator winding through which current flows based on the rotor speed detected by the frequency generation pattern FGPT and with reference to the rotor position detection signal from the rotor position detector.

As shown in FIG. 8, three Hall elements 606, 607, and 608 are used as the rotor position detector. For a detailed arrangement relationship among these three Hall elements 606 to 608, see, for example, U.S. Pat. No. 4,882,511 (the corresponding publication is JP-A-61-164454). The other Hall element 609 is for detecting an index.

Next, the configuration of the magnetic sensor (rotor position detector) according to the first embodiment of the present invention will be described with reference to FIG. 1 in addition to FIG. The rotor position detector according to the present embodiment has a Hall element circuit 62 of a constant current type.
A magnetic sensor having, between the positive power supply terminal VA to the positive electrode terminal 62a and the power supply voltage Vcc is supplied, except in that a low-pass filter 66 instead of the resistor R _21, in FIG. 10 It has a configuration similar to that shown. Therefore, components having the same functions as those shown in FIG. 10 are denoted by the same reference numerals, and their description is omitted for simplification of description.

The illustrated low-pass filter 66 includes a resistor R ₂₁ having one end connected to the positive power supply terminal VA,
Capacitor C ₂₁ inserted between the other end of ₂₁ and the ground terminal
And an RC low-pass filter comprising: In the example shown, the resistor R ₂₁ has a resistance of 130Ω and the capacitor C ₂₁ has a capacitance of 0.1 μF, but these values should be selected appropriately so as to cut off the influence noise. Can be.

As described above, since the low-pass filter 66 is formed between the positive power supply terminal VA and the Hall element circuit 62, high-frequency component noise superimposed on the power supply line is removed, and the Hall element circuit 62 is formed. Element 606 ~
The signal output from 608 can be kept stable. As a result, malfunction of the spindle motor IC 60 can be prevented.

Referring to FIG. 2, the configuration of a magnetic sensor (rotor position detector) according to a second embodiment of the present invention will be described. The rotor position detector according to the present embodiment,
A magnetic sensor having a Hall element circuit 64 of the constant-voltage system, and between the positive power supply terminal VA to the positive electrode terminal 64a and the power supply voltage Vcc is supplied, the low-pass filter 66 instead of the resistor R ₂₁ is provided Except for this, it has the same configuration as that shown in FIG. Therefore, components having the same functions as those shown in FIG. 11 are denoted by the same reference numerals, and description thereof is omitted for simplification of description. Since the configuration of the low-pass filter 66 is the same as that shown in FIG. 1, the description is omitted.

As described above, since the low-pass filter 66 is formed between the positive power supply terminal VA and the Hall element circuit 64, high-frequency component noise superimposed on the power supply line is removed, and the Hall element circuit 64 is formed. Element 606 ~
The signal output from 608 can be kept stable. As a result, malfunction of the spindle motor IC 60 can be prevented.

Returning to FIG. 8, an index circuit for index detection, which is a magnetic sensor according to the third embodiment of the present invention, will be described. The index circuit includes the Hall element 609, a positive electrode terminal 609p of the Hall element 609, and a positive power supply terminal V to which the power supply voltage Vcc is supplied.
A and a low-pass filter (to be described later) provided therebetween. The low-pass filter includes a resistor R ₂₃ whose one end to the positive power supply terminal VA is connected, the resistor R ₂₃
Which is the other end an RC lowpass filter composed of the inserted capacitor C ₂₂ Metropolitan between the ground terminal of the. Incidentally, the negative electrode terminal 609n of the Hall element 609 is grounded.

[0061] Thus, between the positive power supply terminal VA and the Hall element 609, since a low-pass filter consisting of resistor R ₂₃ and capacitor C ₂₂ Prefecture, removes noise of the high frequency component superimposed on the power line And the Hall element 609
Can be kept stable. As a result, malfunction of the spindle motor IC 60 can be prevented.

The present invention is not limited to the above embodiment,
It goes without saying that various changes and modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment,
Although the case where the number of Hall elements constituting the Hall element circuit is one and three is described, the number of Hall elements is not limited to these, and the same applies to the case of two or four or more. . In addition, the low-pass filter is not limited to the RC low-pass filter, and a low-pass filter having another configuration may be used.

[0063]

As is apparent from the above description, according to the present invention, a low-pass filter is formed between the positive power supply terminal to which the power supply voltage is supplied and the Hall element circuit, so that the high-frequency By removing the noise of the component, the signal output from the Hall element constituting the Hall element circuit can be kept stable. Thus, there is an advantage that a malfunction in the spindle motor IC can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a magnetic sensor (rotor position detector) according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a magnetic sensor (rotor position detector) according to a second embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a main part of a floppy disk drive to which the magnetic sensor according to the present invention is applied.

FIG. 4 is a schematic perspective view of the floppy disk drive shown in FIG. 3 as viewed obliquely from the front.

FIG. 5 is a plan view showing a floppy disk driven by a floppy disk drive.

FIG. 6 is a sectional view for explaining an installation structure of a track position detection mechanism (00 sensor) used in the floppy disk drive.

FIG. 7 is a plan view showing the appearance of a one-chip IC of the FDD control device to which the present invention is applied.

8 is a plan view showing the appearance of a spindle motor IC of the FDD control device used together with the one-chip IC shown in FIG. 7;

FIG. 9 is a block diagram showing a schematic configuration inside the one-chip IC shown in FIG. 7;

FIG. 10 is a circuit diagram showing a configuration of a first conventional magnetic sensor (rotor position detector).

FIG. 11 is a circuit diagram showing a configuration of a second conventional magnetic sensor (rotor position detector).

[Explanation of symbols]

60 IC spindle motor 62 Hall element circuit 66 low-pass filter 606-609 Hall element R ₂₁ to R ₂₃ resistors C ₂₁ -C ₂₂ capacitor

Claims (7)

[Claims] 1. A magnetic sensor used for controlling a spindle motor for rotating and driving a magnetic recording medium of a floppy disk in a floppy disk drive for driving an inserted floppy disk. The sensor has a Hall element circuit including at least one Hall element, the Hall element circuit has a positive electrode terminal and a negative electrode terminal, and a low-pass filter is provided between the positive electrode terminal and a positive power supply terminal. A magnetic sensor comprising: 2. The magnetic sensor according to claim 1, further comprising a resistor between the negative electrode terminal and a ground terminal. 3. The magnetic sensor according to claim 2, wherein the Hall element circuit is a constant current type Hall element circuit in which a plurality of Hall elements are connected in series. 4. The magnetic sensor according to claim 2, wherein the Hall element circuit is a constant voltage type Hall element circuit in which a plurality of Hall elements are connected in parallel. 5. The low-pass filter includes a resistor having one end connected to the positive power supply terminal, and a capacitor inserted between the other end of the resistor and the ground terminal.
The magnetic sensor according to claim 1, which is a low-pass filter. 6. The magnetic sensor according to claim 1, wherein the magnetic sensor is a rotor position detector for detecting a position of a rotor of the spindle motor. 7. The magnetic sensor according to claim 1, wherein the magnetic sensor is an index circuit for detecting an index.