JPH08308275A - Driver for brushless motor and electric apparatus by use of it - Google Patents

Abstract

PURPOSE: To enhance the antirolling property even in the case of a type of driver used exclusively for feeding out a current, by connecting both terminals of a braking coil provided in a brushless motor through the medium of a resistor. CONSTITUTION: If both terminals 11a, 11b of a braking coil 11 are connected by short-circuiting or through the medium of a resistor, an induced electromotive force is generated in the braking coil 11 with the rotation of rotor magnets, and an induced current flows. Since a magnet is field by the braking coil 11 is reverse to a magnetic field generated by the stator coils, a magnetic field generated by this induced current functions as a brake against the rotation of the rotor magnets. The quantity of braking can be changed by changing the resistance value. Consequently, it becomes possible to enhance the antirolling property and to extend the frequency property of the response property of the motor, even in the case of a type of motor driver used exclusively for feeding a current out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit of a brushless motor suitable for use as a drive device of a capstan motor of a portable DAT (digital audio tape) device, and the DAT.
It relates to electrical equipment such as devices.

[0002]

2. Description of the Related Art For example, in a DAT device, a capstan motor causes a tape to run at a constant speed between a pinch roller, loading / unloading of a tape and a mechanism, and a supply reel stand and a take-up reel. It is also used to drive reel stands.

The table in FIG. 12 shows the types of capstan speeds and their main uses. The capstan speed for each use is "1" in SP (short play) mode. Is shown by the speed ratio. Further, the capstan FG (CFG) is a pulse generated from a pulse encoder that generates a pulse having a frequency according to the rotation speed of the capstan motor, and the numerical values shown in the table of FIG. 12 are the frequency. .

As shown in the table of FIG. 12, the tape running speed is controlled by the capstan servo using the capstan FG from 0.5 times speed to 16 times speed.
In addition, in high speed running of 25 times speed of fast cue / review, 25 times speed to 100 times speed used in fast forward / rewind, search, etc., with a capstan servo using a pulse encoder output (called a reel FG) from a reel stand, It controls the running speed of the tape.

[0005]

A brushless DC motor is used as a capstan motor for a portable DAT device.
The capstan motor of the DAT device is used from low speed to high speed, and it is difficult for one motor to satisfy the optimum specifications for each speed described above.

In addition, since it is a portable type, the operating voltage is being lowered by battery drive, and it has become necessary for the drive device of the capstan motor to be in the form of a driver for exclusive use of current supply.

That is, FIG. 13 is a principle circuit diagram of the driver for exclusive use of the current supply. The output transistor Q1 and the stator coil of the brushless motor forming a capstan are connected between the terminal where the DC power supply voltage Vs is obtained and the ground. The SC and the resistor R1 are connected in series to form a stator coil S through the output transistor Q1.
The drive current is supplied to C.

On the other hand, conventionally, as shown in FIG. 15, two output transistors Q2 and Q3 and a resistor R2 are connected in series between a terminal from which a DC power supply voltage Vs is obtained and ground. Between the connection midpoint between the transistors Q2 and Q3 and the connection point between the transistor Q3 and the resistor R2,
Although a drive circuit having a configuration for connecting the stator coil SC has been used, in the circuit configuration of FIG. 15, when the power supply voltage Vs becomes low, the voltage drop due to the transistors Q2 and Q3 causes an appropriate amount for the coil SC. Due to such a situation that current cannot be supplied, this FIG.
The circuit of is no longer usable.

For this reason, in a device such as a portable DAT device in which the operating voltage has been lowered, FIG.
Inevitably, a motor drive circuit of the driver type dedicated to current supply such as 3 is used.

However, when the driver for exclusive use of current feeding is applied to the drive circuit of the capstan motor, the rolling resistance is deteriorated. This is because, in the case of the drive circuit of FIG. 15, it is possible to control not only the acceleration direction but also the deceleration direction because the stator coil can be short-circuited by turning on the transistor Q3. In the case of the 13-current-exclusive driver type, the stator coil cannot be short-circuited, so the acceleration direction can be controlled, but the deceleration direction cannot be controlled, and the motor itself decelerates, resulting in loss torque. If it is too small, the frequency characteristic will be extremely deteriorated.

Incidentally, when the servo system is constructed by including the drive circuit shown in FIG. 15, and the frequency characteristic is as shown in FIG. 16, the servo system is constructed by using the drive circuit shown in FIG. In that case, the frequency characteristic is
As shown in FIG. 14, the frequency characteristics of the motor response characteristics cannot be extended. Frequency f01 in FIG.
And f02 are compared, f01 <f02.

In view of the above points, an object of the present invention is to make it possible to improve the rolling resistance even in the drive device of the current-feeding driver type as described above.

[0013]

In order to solve the above-mentioned problems, in a drive device for a brushless motor according to the present invention, a stator coil is arranged facing a rotor magnet mounted so as to rotate integrally with a motor shaft. A drive device for a brushless motor in which a drive current is supplied to the stator coil, which uses a driver for exclusive use of current supply, in which the brushless motor is rotated separately from the stator coil as the rotor magnet rotates. A brake coil that generates a magnetic field in a direction opposite to the magnetic field generated by the stator coil by an induced current is provided, and both ends of the brake coil are connected via a resistor (including a case where the resistance value is zero). To do so.

Further, in the electric device according to the present invention, in order to drive the recording medium, the stator coil is arranged opposite to the rotor magnet mounted so as to rotate integrally with the motor shaft, and the drive current is supplied to the stator coil. Is used, and as a drive device for the brushless motor, an electric device using a current-feeding-only driver is used, in the brushless motor, separately from the stator coil, along with the rotation of the rotor magnet. A brake coil that generates a magnetic field in a direction opposite to the magnetic field generated by the stator coil by an induced current is provided, and both ends of the brake coil are connected via a resistor (including a case where the resistance value is zero). It is characterized by doing so.

[0015]

When both ends of the brake coil are short-circuited (resistance value is zero) or connected via a resistor having a predetermined resistance value, an induced electromotive force is generated in the brake coil as the rotor magnet rotates. , Induced current flows. Since the magnetic field generated by the brake coil is a magnetic field in the opposite direction to the magnetic field generated by the stator coil, the magnetic field generated by this induced current acts as a brake (loss torque) with respect to the rotation of the rotor magnet. If you change the resistance value,
The amount of brake (the amount of loss torque) can be changed.

As described above, even in the motor drive device of the driver type for feeding current, the anti-rolling characteristic can be improved and the frequency characteristic of the response characteristic of the motor can be extended.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a brushless motor drive device according to the present invention and an electric device using the drive device will be described below with reference to the drawings. The example described below is a case where the reproducing apparatus according to the present invention is applied to a DAT apparatus.

First, the brushless motor of this embodiment will be described with reference to FIGS.

FIG. 2 is a longitudinal sectional view of the brushless motor of this example, in which a rotor mounting member 2 is fixed to a rotary shaft 1, and a disc-shaped magnet mounting plate portion 3 is attached to the rotor mounting member 2. And 4 are fixed, and the rotor magnets 5 and 6 are attached to the magnet attaching plate portions 3 and 4. Magnet mounting plates 3, 4
The member 2 constitutes a rotor yoke (magnetic yoke).

The rotor magnets 5 and 6 each have a ring-shaped plate structure, and are magnetized to have a plurality of poles in the circumferential direction of the ring. In the case of this example, the magnet mounting plate portions 3 and 4 are configured to be parallel to each other with a predetermined space therebetween, and the two rotor magnets 5 and 6 have ring-shaped plate surfaces. It is mounted on the mounting plate portions 3 and 4 so as to face each other, leaving a space in which a stator coil described later is present.

On the other hand, a stator yoke 8 is arranged via a bearing 7. A printed circuit board 9 is attached to the extension portion 8A of the stator yoke 8 in a state of being inserted into the space between the rotor magnets 5 and 6, and is mounted on the printed circuit board 9 (below the printed circuit board 9 in the figure). Be on the side)
At the same time, the stator coil 10 is attached, and the brake coil 11 is attached so as to overlap the stator coil 10. In this case, the brake coil 11 is
The magnetic field generated in the brake coil 11 is provided at a position where an electromotive force is generated as the rotor magnets 5 and 6 are rotated, and a current flows through the brake coil 11 due to the induced electromotive force. The magnetic field generated by the stator coil 10 is set to be opposite. That is, the brake coil 11 is configured to generate loss torque.

FIG. 3 is a view showing an arrangement state of the stator coils 10 mounted on the printed board 9. In this example, nine coil blocks 10A1, 10A2, 10A3, 10B each wound in a ring shape.
1,10B2,10B3,10C1,10C2,10C
3 are arranged in an annular shape on the printed circuit board 9 as shown in the drawing without overlapping each other.

This example is an example of a three-phase stator coil, and the coil blocks 10A1, 10A2, 10A3.
Are connected in series to form a first-phase stator coil, and the coil blocks 10B1, 10B2, 10B are connected.
3 are connected in series to form a second-phase stator coil, and further, coil blocks 10C1, 10C2, 1
0C3 is connected in series to form a third-phase stator coil.

Then, the drive currents whose phases are different from each other by 120 degrees are supplied to the stator coils of the respective phases through the above-mentioned driver for exclusive use of current supply. Therefore, in this example, the driver is provided for each phase of the three-phase stator coil, and a total of three drivers are provided. The connection between the coil blocks and the supply of the drive current described above are performed by a conductive pattern (not shown) printed on the printed board 9.

Hall elements 12A, 12B and 12C as rotational phase sensors for the rotor magnets 5 and 6 are mounted on the printed circuit board 9 corresponding to the stator coils of each phase.
The supply period of the drive current to the stator coil of each phase is controlled by the sensor outputs of B and 12C. The electrical connection between the Hall elements 12A, 12B, 12C and the outside is also made through the conductive pattern on the printed board 9 as described above. The above is the configuration and operation almost similar to the conventional brushless motor.

In this example, a magneto-resistive element (MR element) 13 is provided so that a frequency signal FG (capstan FG described above) corresponding to the rotation speed of the rotor magnets 5 and 6 can be obtained. Has been
This capstan FG is designed to obtain signals FG1 and FG2 which are 90 degrees out of phase with each other,
The direction of rotation of the rotor magnets 5 and 6 can be detected based on the advance / lag relationship of these signals FG1 and FG2.

As described above, in the case of this example, the brake coil 11 is provided so as to overlap the stator coil 10 of three phases. FIG. 1 shows an example of the brake coil 11. In this example, the magnetic flux of the rotating magnetic field generated by the rotor magnets 5 and 6 repeats peaks and valleys so as to effectively cut the brake coil 11. It has a zigzag shape.

In the case of this example, the number of turns of the brake coil 11 is determined in consideration of the required brake amount (loss torque amount). In this embodiment, there are 6 turns. The brake coil 11 may be formed by winding a wire, but in this example, the printed circuit board 9 is used.
A flexible sheet substrate in the form of a film provided on top of which a conductive pattern is formed by printing, vapor deposition, deposition, or the like is used. FIG. 4 shows a specific example in which the conductive pattern 14 forms the 6-turn brake coil 11 on the flexible sheet substrate 15.

It should be noted that instead of forming a thin-film flexible sheet substrate on which the brake coil 11 of several turns is formed by a conductive pattern, the brake coil 11 is directly formed on the printed circuit board 9. You can also do it.

As shown in FIGS. 1 and 4, one end of the brake coil 11 is led out as a terminal 11a and the other end is led out as a terminal 11b. In the case of this example, these terminals 11a and 11b are connected to a brake control circuit 20 which is switched and controlled by the output of the servo circuit of the DAT device, as will be described later.

FIG. 5 shows an example of the brake control circuit 20. The brake control circuit 20 of this example includes a switch circuit 2
1 and a variable resistor 22. The switch circuit 21 is provided with three switching positions a, b, and c. At the first switching position a, the terminal 11a is provided.
And the terminal 11b are open, and the brake amount is zero.

In the second switching position b, the terminal 1
1a and the terminal 11b are short-circuited. In this state, the brake amount becomes maximum. In the third switching position c, the variable resistor 22 is connected between the terminals 11a and 11b. At this time, a braking amount corresponding to the magnitude of the resistance value R of the variable resistor 22 is generated.

Switching control signal SW of the switch circuit 21
Is supplied from a servo circuit described later (servo and system control circuit in the example described later). For finer control, the variable resistor 22 is composed of a plurality of resistors and a switch circuit, and the switch circuit is switched to control the resistance value as a whole. In that case, the switching control signal SW from the servo circuit includes the switching circuit 21 and the switching control signal of the switching circuit for switching the plurality of resistors.

It is also possible to use a voltage control type volume as the variable resistor 22 and adjust the resistance value by a control voltage from the servo circuit.

A configuration example of a DAT device using the brushless motor configured as described above as a capstan motor and using a driver for exclusive use of current feed as a motor drive circuit will be described below. That is, FIG. 6 is a block diagram of the overall configuration of the DAT device of this example.

The rotary drum 41 is provided with a rotary magnetic head and is driven to rotate by a drum motor 42. And
A tape (not shown) as a recording medium is wound around a drum over a predetermined angle range, and is sandwiched by a capstan and a pressure roller driven by a capstan motor 43, and the capstan motor 43 will be described later. Servo control is performed as described above, and the tape is transported at a tape speed according to the application as described above.

Then, the servo control is performed in the state of the predetermined capstan speed as described above, and the digital audio signal is recorded on the tape by the rotary magnetic head in the tape running state of the predetermined tape speed. ,
The rotary magnetic head reproduces the recorded digital audio signal from the tape.

That is, when recording, the input terminal 30
The left and right two-channel analog audio signals input through L and 30R are supplied to the A / D converter 32 through the audio amplifier 31 and converted into digital signals. This digital signal is supplied to the recording / reproducing signal processing circuit 33, and after signal processing for recording such as error correction encoding processing is performed, it is supplied to the rotary head of the drum 41 through the RF circuit 34, and the tape is supplied. Is recorded.

At the time of reproduction, the signal from the rotary head of the drum 41 is supplied to the recording / reproduction signal processing circuit 33 through the RF circuit 34, and reproduction signal processing such as error correction decoding processing is performed. Then, the reproduced digital signal is supplied to the D / A converter 36 through the digital filter 35 and converted into an analog signal, the left and right two-channel audio signals are reproduced through the low-pass filter 37 for band limitation, and the output terminals 38L and 38R are reproduced. Be derived to.

Servo and system control circuit 5
0 controls the servo of the capstan motor 43 so that the tape speed corresponds to each reproduction mode and application, and also controls the servo of the drum motor 42.

The drum motor servo is performed as follows. That is, the frequency signal DFG having a frequency corresponding to the rotation speed of the drum from the drum motor 42 and the signal DPG corresponding to the rotation phase of the drum are supplied to the system control circuit 50 through the sensor amplifier 44, and the system control circuit 50 responds to these signals. The control signal is supplied to the drum motor 42 via the filter circuit 45 and the drum motor drive circuit 46, and the rotational speed and rotational phase of the drum are controlled.

Next, servo control of the capstan motor 43 will be described. FIG. 7 is a more detailed block diagram in which only the capstan servo system is extracted from the configuration diagram of FIG. 6, and will be described below also with reference to FIG. 7.

That is, the capstan FG (CF) which is a signal of a frequency corresponding to the rotation speed of the motor 43 from the pulse encode 48 provided in the capstan motor 43.
G) is supplied to the servo and system control circuit 50 through the sensor amplifier 44. The cycle detection circuit 51 of the servo and system control circuit 50 is
The cycle of the capstan FG is detected and the detection output is supplied to the angular velocity error detection circuit 52. The angular velocity error detection circuit 52 detects the angular velocity error of the capstan motor from the change in the detected period of the capstan FG, and supplies the error detection signal to the servo arithmetic processing circuit 53.

At the time of reproduction, the recording / reproduction signal processing circuit 33 supplies an auto-tracking control signal (reproduction pilot signal for ATF) to the servo and system control circuit 50. The ATF reproduction pilot signal is converted into a digital signal in the A / D converter 54 and supplied to the servo arithmetic processing circuit 53 via the switch circuit 55. The switch circuit 55 is
It is turned off during recording and turned on during reproduction by a switching signal from the system control block 56.

The system control block 56
A signal for instructing the mode and the application is supplied to the capstan speed control circuit 58. The capstan speed control circuit 58 supplies the servo arithmetic processing circuit 53 with speed reference data and the like according to the mode and application.

The servo arithmetic processing circuit 53 generates only the speed control signal from the error signal from the angular speed error detection circuit 52 because the switch circuit 55 is off at the time of recording, and at the time of reproduction, this speed control circuit 53 In addition to the signal, a tracking control signal based on the above-mentioned ATF reproduction pilot signal is generated and supplied to the output data generation circuit 57. The output data generation circuit 57 converts the servo control signal from the servo calculation processing circuit 53 into a PWM signal and outputs it.

The PWM signal of the servo control signal is supplied to the capstan motor drive circuit 47 via the filter circuit 45, and the capstan motor 43 is adapted to the mode or application as shown in the table of FIG. The speed is controlled to be the rotation speed, and at the time of reproduction, the recording track is properly scanned.

As described above, the capstan motor drive circuit 47 of this example has the structure of a driver for exclusive use of current feed.

At this time, the capstan speed control circuit 58 also generates a control signal for generating a brake (loss torque) corresponding to the speed according to the above-mentioned mode and other uses. In this example, this control signal is supplied to the brake control circuit 20 as shown in FIG. As described above, this control signal is the switching control signal SW for the switch circuit 21 and the resistor.
Is.

In this example, the mode is LP mode or SP.
In the mode, the switch circuit 21 switches to the switching position b.
Is connected to both ends 11a, 11 of the brake coil 11.
Between b, the circuit is short-circuited, the amount of brake is relatively large, and the frequency characteristic of the servo circuit is extended. When the speed in the soft tape mode is 1.5 times, the switch circuit 21 is connected to the switching position c, and a resistor is inserted between the terminals 11a and 11b to which both ends of the brake coil 11 are connected. However, its resistance value is considered to be relatively small.

When the speed is 1 × or more and during acceleration, the switch circuit 21 is connected to the switching position a, and both ends of the brake coil 11 are connected to the terminal 11.
Between a and 11b is open so that the brake is not applied, but during deceleration, the switch circuit 21 is connected to the switching position b or c so that a predetermined brake is applied.

As described above, the capstan speed control circuit 58 controls the switching of the brake control circuit 20 according to the speed of the capstan motor, so that the speed of each capstan motor can be changed to a desired value when necessary. The brake can be applied and the optimum characteristics at that time are obtained.

FIG. 8 shows the servo response characteristics when the terminals 11a and 11b to which both ends of the brake coil 11 are connected are opened, and FIG. 9 shows that both ends of the brake coil 11 are connected. It is a servo response characteristic when the terminals 11a and 11b are short-circuited. Comparing the frequencies of 3 dB drop, it was proved that the frequency characteristic was 0.6 Hz when open and 1.3 Hz when short-circuited, which doubled the frequency characteristic.

As described above, in the case of this example, it is opened at the time of fast-forwarding and rewinding where the frequency characteristic is not so much required, so that it is the same as the conventional one, but in the LP mode or the SP mode, Both ends 1 of the coil 11 for
Since 1a and 11b are short-circuited, the frequency characteristic of the servo is extended as compared with the conventional one, and the optimum frequency characteristic is obtained.

[Other Embodiments] The brake coil of the above example has a structure in which the brake coil having a required number of turns is wound by a conductive pattern on a printed board or one sheet-like flexible board. But each one
In order to obtain a required brake amount, a required number of sheets out of the plurality of sheet-shaped coils is formed by stacking a plurality of sheet-shaped flexible substrates on which coils with 1 to n turns are formed. It is also possible to adopt a configuration in which the selection is switched to select.

FIG. 10 shows an example of a coil overlapping structure of a brushless motor as a capstan motor in the case of a three-layer brake coil. That is, in the case of this example, the sheet-like coils 61 and 62 each having a structure in which a conductive pattern as a wire is wound 6 turns around a flexible sheet substrate as shown in FIG. , 63 are stacked, for example, in three layers, and the stator coil 10 is mounted thereon.

In the case of this example, the brake control circuit 20 is constructed as shown in FIG. That is, the switch circuit 71 is connected between both ends 61a and 61b of the sheet coil 61. Then, the other end 61b of the sheet coil 61 is connected to one end 62a of the sheet coil 62, and the switch circuit 72 is connected between the one end 61a of the sheet coil 61 and the other end 62b of the sheet coil 62. . Further, the other end 62b of the sheet coil 62 is connected to one end 63a of the sheet coil 63, and the switch circuit 73 is connected between one end 61a of the sheet coil 61 and the other end 63b of the sheet coil 63. .

Although not shown, the above-mentioned FIG.
The capstan speed control circuit 58 supplies the ON / OFF control signals for the three switch circuits 71, 72, 73 according to the speed of the capstan motor 43.

In this example, the switch circuits 71 to 7
When all three are off, the brakes are not applied. When the switch circuit 71 is on, the brake amount is small, when the switch circuit 72 is on, the brake amount is medium, and when the switch circuit 73 is on, the brake amount is maximum.

In this example as well, similar to the above example, not only the coils are short-circuited, but also the configuration in which they are connected via a resistor is used in combination, so that finer brake control can be performed.

Further, as described above, the three sheet-shaped coils 61, 62, 63 are not switched so as to be connected in series by the switch circuits 71-73, but both ends of each of the sheet-shaped coils 61, 62, 63 are switched. By providing a switch circuit between them and turning on / off each switch circuit, it is possible to switch so as to change the number of sheet-like coils that short-circuit between both ends. Furthermore, in that case, for each sheet coil,
A variable resistor may be provided in association with each switch circuit as the circuit configuration shown in FIG. 5 described above.

The above example is an example in which the electric device is a DAT device, but the present invention uses a brushless motor for running or rotating the recording medium, and
The present invention can be applied to all recording / reproducing devices or reproducing devices that use a driver for supplying current to the drive device.

[0063]

As described above, according to the present invention, the frequency characteristic of the servo response characteristic can be extended and the rolling resistance characteristic can be improved even if the drive type is a current-feeding type brushless motor. A good brushless motor can be obtained.

Further, in the electric equipment according to the present invention using this brushless motor for driving the recording medium, even if the power supply voltage becomes low as in the portable type,
It becomes possible to perform optimum speed control according to various speeds of the recording medium.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of portions of a stator coil and a brake coil of an embodiment of a brushless motor according to the present invention.

FIG. 2 is a vertical sectional view of an embodiment of the brushless motor according to the present invention.

FIG. 3 is a diagram showing an arrangement state of stator coils in an embodiment of the brushless motor according to the present invention.

FIG. 4 is a diagram showing a configuration example of a brake coil in an embodiment of the brushless motor according to the present invention.

FIG. 5 is a diagram showing an example of a control circuit for performing brake control of an embodiment of the brushless motor according to the present invention.

FIG. 6 is a block diagram of an embodiment of a DAT device as an example of an electric device according to the present invention.

7 is a block diagram showing a configuration example of a main part of the DAT device of FIG.

FIG. 8 is a diagram showing servo response characteristics of an embodiment of the brushless motor according to the present invention.

FIG. 9 is a diagram showing servo response characteristics of an embodiment of the brushless motor according to the present invention.

FIG. 10 is a diagram for explaining another example of the portions of the stator coil and the brake coil of the embodiment of the brushless motor according to the present invention.

11 is a diagram showing an example of a control circuit for controlling the brake of the brushless motor of the example of FIG.

FIG. 12 is a DAT as an example of an electric device according to the present invention.
It is a figure for demonstrating the kind of speed of the capstan motor of an apparatus.

FIG. 13 is a principle circuit diagram of an example of a drive device for a brushless motor.

FIG. 14 is a frequency characteristic diagram of an example of a drive device for the brushless motor of FIG.

FIG. 15 is a principle circuit diagram of another example of the drive device of the brushless motor.

16 is a frequency characteristic diagram of another example of the drive device for the brushless motor of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 motor shaft 3, 4 rotor yoke 5, 6 rotor magnet 8 stator yoke 9 printed circuit board 10 stator coil 11 brake coil 11a brake coil one end 11b brake coil other end 12A, 12B, 12C Hall element 13 magnetic sensitive element 14 Conductive pattern 20 Brake control circuit 21 Switch circuit 22 Variable resistor 43 Capstan motor 47 Capstan motor drive circuit 50 Servo and system control circuit 58 Capstan speed control circuit 61, 62, 63 Sheet-shaped brake coil 71, 72, 73 switch circuit

Claims (5)

[Claims] 1. A drive device for a brushless motor, wherein a stator coil is arranged so as to face a rotor magnet mounted so as to rotate integrally with a motor shaft, and a drive current is supplied to the stator coil. Using a dedicated driver, in the brushless motor, a brake coil that generates a magnetic field in a direction opposite to the magnetic field generated by the stator coil by a current induced by rotation of the rotor magnet, separately from the stator coil. And a drive device for a brushless motor, wherein the both ends of the brake coil are connected via a resistance (including a case where the resistance value is zero). 2. The drive device for a brushless motor according to claim 1, wherein the brake coil is in the form of a sheet. 3. A brushless motor in which a stator coil is arranged to face a rotor magnet mounted so as to rotate integrally with a motor shaft to drive a recording medium, and a drive current is supplied to the stator coil. In the electric device, which is used as a drive device of this brushless motor, a driver for exclusive use of current supply is used, and in the brushless motor, the stator is driven separately from the stator coil by a current induced by rotation of the rotor magnet. A braking coil that generates a magnetic field in a direction opposite to the magnetic field generated by the coil is provided, and both ends of the braking coil are connected via a resistor (including a case where the resistance value is zero). Electrical equipment. 4. The electric device according to claim 3, wherein the value of the resistance connected between both ends of the brake coil is changed according to the driving speed of the recording medium. . 5. The electric device according to claim 3, wherein the brake coil is formed of a sheet-shaped coil.