JPH08275571A - Motor drive circuit - Google Patents

Abstract

PURPOSE: To stop a motor quickly and smoothly without causing reverse rotation by conducting the motor coil reversely and fixing the conducting direction when the r.p.m. of motor decreases to a predetermined value. CONSTITUTION: A switch circuit 26 is connected with the bases of transistors 14, 18, 22, 24 in order to switch the direction of a motor coil 10 depending on the rotor position. A rotation detecting circuit 72 is provided with a comparator and a detection signal is fed to the switch circuit 26 when the upper voltage of a capacitor 74 exceeds a predetermined level. The switch circuit 26 stops the switch operation in response to the detection signal. In other words, the current flowing through the motor coil 10 is fixed to one direction. Consequently, the rotor of a single-phase motor is pulled to a position corresponding to one pattern of field and the motor is locked, i.e., stopped, under that state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit for driving a motor by switching the energization direction to a motor coil, and more particularly to a mechanism for stopping the motor by a reverse torque.

[0002]

2. Description of the Related Art Conventionally, a motor has been widely used as a rotary drive source for various members. This motor can control the generated torque, the number of revolutions, and the like by controlling the drive current, so that computer control and the like are easy, and its application is expanding.

Here, in addition to the use of mechanical braking means, electric braking such as a short brake is also used for braking the motor. According to such electric braking,
Compared to mechanical brakes, no additional components are required and no durability problems occur.

[0004]

However, this short brake can shorten the motor stop time based on the reduction of the short-circuit impedance, but on the other hand, it requires a semiconductor switch exclusively for short-circuiting, which complicates the circuit configuration and increases the cost. In addition to this, the problem that the rapid oscillation is difficult to stop cannot be eliminated because the amplitude of the damping vibration of the short-circuit current decreases at low speed rotation.

On the other hand, when the motor is to be stopped rapidly, the motor is energized so that a reverse torque (reverse rotation torque) is generated in the motor. However, when the reverse rotation torque is continuously applied to the motor, the motor starts reverse rotation. Therefore, the generation of this reverse rotation torque must be stopped at an appropriate stage.

However, since it has been difficult to stop the motor accurately by this control, the reverse rotation torque is stopped early with some margin. Therefore, there is a problem that the idle rotation remains after that and the time until the stop becomes long. Therefore, in order to achieve a quick stop, it is common to use a mechanical brake having sufficient ability together.

Here, a motor is generally one in which a rotating magnetic field is formed by coils of a plurality of phases to rotate a rotor. However, a single-phase coil is used to rotate the rotor by switching the energization direction. Phase motors are also known. This single-phase motor needs special means so that the rotor starts to rotate in a predetermined direction at the time of starting, but the mechanism is simple and there is no problem in rotation after starting, so that it is particularly low-cost. It is used as a motor.

Since such a single-phase motor uses special means, for example, magnetic anisotropy, there is a possibility that an electric brake different from the conventional one can be adopted.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a motor drive circuit that can electrically and rapidly stop a motor without causing reverse rotation.

[0010]

SUMMARY OF THE INVENTION The present invention is a motor drive circuit for driving a motor by switching the energization direction to a motor coil. When the motor is stopped, a torque in the opposite direction to the rotation direction is generated in the motor. As described above, reversely energize the motor coil, and after the reverse rotation energizes the motor rotation speed to a predetermined value, fix the energization direction to the motor coil in one direction and stop the motor. Is characterized by.

Further, the present invention is a motor drive circuit for driving a motor by switching the energization direction to the motor coil, and when the motor is stopped, torque is generated in the motor in the direction opposite to the rotation direction. It is characterized in that the motor coil is energized in the reverse direction, and after the rotation speed of the motor is reduced to a predetermined value by the energization in the reverse direction, the energizing current to the motor coil is gradually reduced to stop the motor.

Further, the present invention is a motor drive circuit for driving a motor by switching the energization direction to the motor coil, and when the motor is stopped, torque is generated in the motor in a direction opposite to the rotation direction. The motor coil is energized in the reverse direction, and after the rotation speed of the motor has decreased to a specified value by this energization in the reverse direction, the energizing direction to the motor coil is fixed in one direction and the energizing current to the motor coil is gradually increased. It is characterized in that it is decreased and the motor is stopped.

Further, a current control signal generating means for controlling energization to the motor by an output from a switching circuit whose output is regulated by a constant current circuit and for generating a current control signal for controlling an energization current to the motor coil. , A capacitor for removing high frequency components of this current control signal, and controlling the current amount of the constant current circuit by the current control signal from which the high frequency components have been removed by the output of this capacitor, and energizing the motor coil. Control, and after the number of rotations of the motor has decreased to a predetermined value, the output of the current control signal is turned off, the output of the capacitor is gradually decreased, and the current value of the constant current circuit is gradually decreased. It is characterized by

Further, a pulse generating means for generating a pulse according to the rotation of the motor, an integrating circuit for charging the capacitor with a constant current and discharging by the pulse generated by the pulse generating means, and an output of the integrating circuit are predetermined. Comparing means for comparing with the threshold value of 1), and detecting that the number of rotations of the motor has decreased to a predetermined value based on the comparison result of the comparing means.

[0015]

As described above, according to the present invention, when the motor is energized in the reverse direction, torque is generated in the motor in the direction opposite to the rotation direction. Therefore, the rotation speed sharply decreases. Then, when the motor speed decreases to a predetermined value, the energization direction to the motor coil is fixed in one direction. Therefore, the induced magnetic field generated by energization is fixed. Therefore, the rotor magnet is fixed (locked) at a position according to the direction of the fixed induction magnetic field, regardless of its magnetic poleability.
Attempts are made to stop the rotation of the motor.

According to another aspect of the invention, when the motor rotation speed decreases to a predetermined value, the current supplied to the motor coil is gradually decreased. As a result, the reverse torque applied to the motor gradually decreases, and the motor stops.

Further, according to another invention, when the number of rotations of the motor decreases to a predetermined value, the energization direction to the motor coil is fixed in one direction and the energization current to the motor coil is gradually decreased. As a result, the electric current for fixing the rotor is gradually reduced automatically, and a smooth stop is possible.

Further, by stopping the output of the current control signal of the motor coil, the current supplied to the capacitor for removing the high frequency component of the current signal control signal becomes zero. Therefore,
The current amount of the constant current circuit whose current amount is determined according to the output of the capacitor gradually decreases as the capacitor discharges. Then, the constant current circuit controls the motor energization current amount by the amount of current, whereby the motor energization current can be gradually reduced.

A decrease in the number of rotations of the motor is detected by providing a capacitor to be discharged by a pulse signal generated with the rotation of the motor and detecting that the output voltage of the capacitor has exceeded a predetermined value.

If the motor is a single-phase motor, by making the energizing direction of the motor coil one direction, a magnetic field having a one-to-one correspondence with the magnetic poles of the rotor is generated especially when this motor is a synchronous type. To be done. Therefore, the magnetic field effectively damps the rotation of the rotor. Similar analogy can be made when the motor is asynchronous.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a CD-ROM reader will be described below with reference to the drawings. In the case of the energized CD-ROM, an asynchronous motor is used, but for simplicity, it will be described using a synchronous motor. The motor of this embodiment has, for example, one motor coil 10. The motor coil 10 is, for example, sequentially wound around four projecting portions of the stator or individually wound around each projecting portion and connected in series. Therefore,
By energizing, N poles and S poles are alternately generated in each protrusion, and N and S are inverted by switching the energizing direction. And, four magnetic poles (N pole,
Rotors of which the south poles are arranged alternately). Therefore, the motor can be rotationally driven by controlling the energization of the motor coil 10 so that the S pole of the stator moves slightly ahead of the N pole of the rotor.

One end of the motor coil 10 is connected to an intermediate point between two NPN transistors connected in series, a first power supply side transistor 12 and a first ground side transistor 14. The other end of the motor coil 10 has two NPN transistors connected in series, a second
The intermediate point between the power supply side transistor 16 and the second ground side transistor 18 is connected. The collectors of the transistors 12 and 16 are connected to the power supply VM via the current detection resistor 20, and the emitters of the transistors 14 and 18 are grounded. The transistors 12 and 1
The base of 6 has a PN whose emitter is connected to the power supply VM.
The collectors of the P transistors 22 and 24 are connected.

Therefore, by setting the bases of the transistors 22 and 14 to L (low level) and the bases of the transistors 24 and 18 to H (high level), the transistor 1
The transistors 2 and 18 are turned on, the transistors 16 and 14 are turned off, and a current flows to the motor coil 10 in the right direction in the drawing. On the contrary, by setting the bases of the transistors 22 and 14 to H (low level) and the bases of the transistors 24 and 18 to L (high level), the transistors 12 and 18 are turned off, and the transistors 16 and 14 are turned on. A current flows to the left in the drawing in the coil 10. Therefore, such a control signal causes the transistors 12, 1
By controlling the on / off of 4, 16, 18, 22, 24, the current flowing through the motor coil 10 is switched,
The generated magnetic field can be switched. Further, the amount of current flowing through the motor coil 10 is controlled by the levels of H and L of the control signal.

An energization switching circuit 26 is connected to the bases of the transistors 14, 18, 22 and 24, and on / off and current amounts of these transistors are controlled by a control signal from the circuit. Here, the on / off of the transistors 14, 18, 22, 24 must be controlled according to the rotation of the motor (the relative position of the rotor and the stator depending on the rotation direction). Therefore, a Hall element 28 for detecting the position of the rotor is provided near the rotor. The output side of the Hall element 28 is connected to the energization switching circuit 26 via the Hall amplifier 30, and the energization switching circuit 26 switches the energization direction of the motor coil 10 according to the position of the rotor. Therefore, the motor can be rotated by energizing the rotor magnet at a point where the magnetic field induced by the motor coil 10 is always at a predetermined position. The output of the Hall element 28, which changes in a sine curve according to the change of the magnetic field, is amplified by the Hall amplifier 30 into a rectangular wave.

Further, in the present embodiment, there is additionally provided a motor rotation speed control system utilizing a read signal from the disk. That is, in the signal processing circuit 40 for processing the read signal from the disk, the rotation speed of the disk is detected from the supply state of the read signal. A servo circuit 42 is connected to the signal processing circuit 40, and the servo circuit 42 causes the speed command E regarding the rotation speed to be output.
Output c.

This speed command Ec is applied to the V type control amplifier 44.
Is supplied to the positive input terminal of. The reference voltage EcR is supplied to the negative input terminal of the V-type control amplifier 44, and the V-type control amplifier 44 obtains an output having the characteristics shown in FIG. 2 by comparing both input signals. That is, the speed command Ec is equal to the reference voltage E.
A positive voltage proportional to the difference is output regardless of whether it is larger or smaller than cR.

The output of the V-type control amplifier 44 is connected to the base of the transistor 45. This transistor 4
In 5, the collector is connected to the power source VM via the resistor, the emitter is connected to the ground via the resistor, and the collector is connected to the current control amplifier 46. Therefore, the higher the output of the V-type control amplifier 44, the lower the voltage supplied to the current control amplifier 46. The current control amplifier 46 is connected to the collector voltage of the transistor 45, the transistor 12,
The upper side voltage of 16 (the lower side voltage of the current detection resistor 20) is compared. Since substantially the same current as that flowing through the motor coil 10 flows through the current detection resistor 20, the upper voltage of the transistors 12, 16 drops below the power supply voltage VM by a voltage corresponding to the current flowing through the motor coil. The voltage is on. That is, the energization amount in the motor coil 10 is detected based on this voltage value. Then, the current control amplifier 46 outputs a current that increases as the voltage of the output of the V-type control amplifier 44 increases according to the comparison result.

The output of the current control amplifier 46 is connected to a capacitor 48 whose other end is connected to the ground, and
A diode-connected (collector-base short-circuited) transistor 52 is connected via the resistor 50. Also,
The base of the transistor 52 is connected to the base of the transistor 54, and the transistors 52 and 54 form a current mirror. The emitters of the transistors 52 and 54 are grounded.

Therefore, the high frequency component of the current control amplifier 46 is removed by the capacitor 48, and the current control amplifier 4
A current corresponding to the output of 6 flows in the transistors 52 and 54. The collector of the transistor 54 functions as a constant current source of the current switching circuit 26. Therefore,
When the output current of the current control amplifier 46 decreases, the output of the current switching circuit 26 decreases accordingly, and the current flowing through the motor coil 10 decreases accordingly. On the other hand, when the output current of the current control amplifier 46 increases, the output of the current switching circuit 26 increases correspondingly, which increases the current flowing through the motor coil 10. By such control, the current amount of the motor coil 10 is changed to a predetermined value according to the speed command Ec which is the output of the servo circuit 42. Further, the current value of the motor coil 10 is fed back to the current control amplifier 46, and feedback control is performed so as to match the output of the V-type control amplifier 44.

Further, when the eject button is pressed while the disk is operating, a motor stop command is issued. This stop command is issued by the brake circuit 60.
Is input to A forward / reverse rotation switching circuit 62 is connected to the brake circuit 60, and the forward / reverse rotation switching circuit 6 is connected.
2 sends a signal to the energization switching circuit 26 in response to the stop command to switch the switching timing to the reverse rotation timing. That is, the energization switching circuit 26 controls the timing of the signals supplied to the transistors 22, 14, 24, 18 to apply reverse torque to the rotor.
This is done by passing a current through the motor coil 10 such that there is a magnetic pole due to the induced magnetic field that opposes the magnetic poles of the rotor magnet and produces an opposite torque for forward rotation. Unlike the short brake, this current does not cause damped vibration and is basically kept at a constant value, so a strong reverse torque is generated with respect to the rotation of the motor, and the electric rapid brake operates.

The rectangular wave signal of the rotation of the rotor, which is the output of the Hall amplifier 30, is supplied to the edge pulse generating circuit 70. The edge pulse generation circuit 70 detects the rising edge and the falling edge of the pulse signal which is the output of the Hall amplifier, and outputs the short-term edge pulse. The output of the edge pulse generation circuit 70 is supplied to the rotation detection circuit 72.

A capacitor 74 whose other end is connected to the ground is connected to the rotation detecting circuit 72, and a transistor 77 which connects the upper side of the capacitor 74 to the ground.
The base of is connected. Then, the rotation detection circuit 72
Constantly charges the capacitor 74 with a predetermined constant current, and also supplies the edge pulse supplied from the edge pulse generation circuit 70 to the base of the transistor 76 to periodically discharge the charging voltage of the capacitor 74. Therefore, as shown in FIG. 3, the upper voltage of the capacitor 74 becomes higher as the period of the edge pulse becomes longer.

The rotation detecting circuit 72 is provided with a comparator, which compares a predetermined high voltage Vs with the upper voltage of the capacitor 74, and the upper voltage of the capacitor 74 exceeds the voltage Vs. Sometimes, it outputs a detection signal. This signal is supplied to the energization switching circuit 26.

The energization switching circuit 26 includes a rotation detecting circuit 62.
The switching is stopped in response to the detection signal from. That is, the transistors 12 and 18 are turned on and the transistor 1 is turned on.
The transistors 6 and 14 are turned off (or vice versa) to fix the state of the transistor so that the current flowing through the motor coil 10 is fixed in one direction. Thus, when the current flowing through the motor coil 10 is fixed, the rotor of the single-phase motor is pulled to a position according to the magnetic field of one form generated by the motor coil 10 and fixed in this state, that is, the motor stops. To be done. When the rotation detection circuit 62 generates the detection signal, the generation of the edge pulse is prohibited. Therefore, the upper potential of the capacitor 74 becomes a predetermined constant potential.

As described above, according to the present embodiment, when the motor rotation speed becomes equal to or lower than the predetermined value due to the reverse braking (when the interval between the edge pulses becomes equal to or higher than the predetermined value), the motor coil 10 is driven. The current supplied is fixed in one direction. This allows the motor to be stopped rapidly without reverse rotation.

Here, in the case of a single-phase motor, depending on the positional relationship between the rotor and the stator at the time of starting, there is a possibility that the motor may rotate in the reverse direction or may not move at all. Therefore, this must be resolved. So, for example,
By imparting anisotropy to the magnetic characteristics of the iron core around which the motor coil 10 is wound, the direction of the generated magnetic field is slightly shifted depending on the direction of energization of the motor coil 10. Then, it is conceivable that the energization for the forward rotation and the energization for the reverse rotation are alternately performed, the energization is continued as it is after the forward rotation, and the energization for the forward rotation is switched when the reverse rotation is started. Such a structure was proposed in Japanese Patent Application No. 6-172677.

With such a structure, in order to alternately generate a signal for repeating normal rotation and reverse rotation, the capacitor is charged and discharged with a predetermined constant current, and a reverse rotation command is issued when a predetermined high voltage is reached. A circuit for generating a forward rotation command when the voltage is generated and reaches a predetermined low voltage is adopted. Further, when the rotation is started at the time of the reverse rotation command, the above-mentioned edge pulse discharges the capacitor so that the reverse rotation command is not generated thereafter.

Therefore, the edge pulse generating circuit 70 can be used in the structure for such activation, and the capacitor 7 can be used.
4 can be used. Then, the start-up and the stop are at different timings, and by using these members in common, the number of members can be reduced and an efficient circuit can be obtained. It should be noted that the amount of charging current to the capacitor 74 at the time of start-up and the amount of charging current at the time of stop must be different.

The output of the rotation detection circuit 70 is supplied to the current control amplifier 46, and the operation of the current control amplifier 46 is stopped by the detection signal. Specifically, the constant current source of the current control amplifier 46 (for example, the constant current source that determines the sum current amount of the pair of differential transistors) is determined by H of the detection signal output from the rotation detection circuit 72. Set the current to 0.

When the operation of the current control amplifier 46 is stopped in this way, its output also becomes zero. The output is turned off by turning off the transistors on the ground side and the power supply side. Here, the output of the current control amplifier 46 is
A capacitor 48 is connected and holds a predetermined charge. Therefore, the electric charge of the capacitor 48 flows toward the ground via the resistor 50 and the transistor 52. Therefore, the current flowing through the transistor 54 gradually decreases and becomes zero in a predetermined time.

Therefore, the output of the energization switching circuit 26 also gradually decreases, and the current flowing through the motor coil 10 gradually becomes zero. That is, when the motor is rotated at a predetermined low speed, the energization direction to the motor coil 10 is fixed in one direction, and this current amount is automatically and gradually reduced. Therefore, after the motor stops, unnecessary current does not continue to flow to the motor.

It should be noted that stopping the energization of the motor coil 10
It may be performed by other means such as a timer, and in this case, the control for stopping the operation of the current control amplifier 46 becomes unnecessary.

Further, it is possible to omit the control for fixing the energization direction to the motor coil 10 in one direction by the energization switching circuit 26. Also in this case, the energization current of the motor coil 10 is gradually reduced by the output of the energization switching circuit 26, but the energization direction of the motor coil 10 is continuously switched. Then, due to this energization, the reverse torque continues to be generated, but this torque gradually decreases and the motor stops.

The motor of the present invention is not limited to a single phase, and other motors can be similarly braked as long as the induction magnetic field is fixed by a constant current during braking.

[0045]

As described above, according to the present invention, when the motor speed decreases to a predetermined value, the direction of energization to the motor coil is fixed in one direction, and the magnetic field generated by energization is fixed. . Therefore, the rotor is fixed at a position according to the direction of the fixed magnetic field, and the rotation of the motor is stopped.
As a result, the motor can be stopped rapidly without reverse rotation.

Further, the motor can be smoothly stopped without rotating in the reverse direction by gradually reducing the current supplied to the motor coil.

Further, by fixing the energization direction to the motor coil in one direction and gradually decreasing the energization current to the motor coil, the current for fixing the rotor is gradually decreased automatically, and after stopping. It is possible to prevent supply of unnecessary current. Moreover, the number of parts can be reduced by gradually reducing the energizing current of the motor coil by utilizing the capacitor for high frequency removal in the rotation control.

By providing a capacitor to be discharged by the pulse signal generated by the rotation of the motor, it is possible to efficiently detect that the rotational speed has become low.

If the motor is a single-phase motor, a magnetic field corresponding to the magnetic pole of the rotor in a one-to-one relationship is generated by setting the energization direction to the motor coil in one direction. Therefore,
This magnetic field can effectively stop the rotation of the rotor.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an embodiment.

FIG. 2 is a diagram showing characteristics of a V-type control amplifier.

FIG. 3 is a diagram showing a waveform of each part such as an edge pulse.

[Explanation of symbols]

10 motor coils, 12, 14, 16, 18, 2
2, 24, 52, 54 transistors, 20 current detection resistor, 26 energization switching circuit, 28 hall element, 30
Hall amplifier, 40 signal processing circuit, 42 servo circuit, 44 V type control amplifier, 46 current control amplifier, 4
8,74 capacitor, 60 brake circuit, 62 forward / reverse rotation switching circuit, 70 edge pulse generating circuit, 7
2 Rotation detection circuit.

Claims (5)

[Claims] 1. A motor drive circuit for driving a motor by switching the energization direction to the motor coil, wherein when the motor is stopped, a torque is applied to the motor coil so that a torque in a direction opposite to the rotation direction is generated in the motor. The motor drive circuit is characterized in that reverse rotation energization is performed, and after the rotation speed of the motor has decreased to a predetermined value due to this reverse energization, the energization direction to the motor coil is fixed in one direction and the motor is stopped. 2. A motor drive circuit for driving a motor by switching the energization direction to the motor coil, wherein when the motor is stopped, a torque is applied to the motor coil in a direction opposite to the rotational direction of the motor coil. A motor drive circuit characterized in that reverse rotation energization is performed, and after the rotation speed of the motor has decreased to a predetermined value due to this reverse energization, the energizing current to the motor coil is gradually reduced to stop the motor. 3. A motor drive circuit for driving a motor by switching the energization direction to the motor coil, wherein when the motor is stopped, a torque is applied to the motor coil so that a torque in a direction opposite to the rotation direction is generated in the motor. Reverse rotation energization is performed, and after the rotation speed of the motor has decreased to a predetermined value due to this reverse rotation energization, the energization direction to the motor coil is fixed in one direction, and the energization current to the motor coil is gradually reduced to A motor drive circuit characterized by stopping. 4. The circuit according to claim 2 or 3, wherein energization of the motor is controlled by an output from a switching circuit whose output is regulated by a constant current circuit, and current is energized to a motor coil. A current control signal generating means for generating a control signal and a capacitor for removing a high frequency component of the current control signal are provided, and the current of the constant current circuit is controlled by the current control signal from which the high frequency component is removed by the output of the capacitor. Control the amount of electricity to the motor coil, and after the number of rotations of the motor has dropped to a predetermined value, turn off the output of the current control signal and gradually decrease the output of the capacitor. A motor drive circuit characterized by gradually reducing the current value of a constant current circuit. 5. The circuit according to claim 1, further comprising: pulse generating means for generating a pulse according to rotation of the motor; and a capacitor charged with a constant current to generate the pulse by the pulse generating means. It has an integrator circuit which is discharged by a pulse and a comparing means for comparing the output of this integrator circuit with a predetermined threshold value. Based on the comparison result of the comparing means, it is detected that the rotation speed of the motor has decreased to a predetermined value. A motor drive circuit characterized by the above.