JP2692873B2 - Motor stop detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention controls a disc motor such as a compact disc player (hereinafter referred to as a CD player), a laser disc player (hereinafter referred to as an LD player), and the like. The present invention relates to a motor stop detection circuit used in a circuit that operates.

(Prior Art) In a CD player or an LD player, for example, when playing is finished and the disc is taken out, it is necessary to completely stop the rotation of the disc before proceeding to the next process.

In order to stop the rotation of the disc, it is necessary to supply the brake voltage to the disc motor and turn off the brake voltage when the rotation of the motor becomes zero. If the off timing of the brake voltage is deviated, the normal rotation may be maintained or the reverse rotation may occur due to the inertia of the motor, resulting in damage to the disk.

FIG. 5 shows a conventional DC motor control circuit, in which a portion for applying a brake to stop the circuit is taken out and shown.

The turntable 1 is rotated by the disc motor 2. The disk motor 2 can be driven to rotate normally or reversely by the motor drive circuit 3. When stopping the rotation of the disk motor 2 in the normal rotation state, a brake control signal from the brake voltage generation circuit 4 is given to the motor drive circuit 3. Then
The motor drive circuit 3 outputs a voltage having a polarity opposite to that of the forward drive voltage, that is, a reverse drive voltage and supplies it to the disk motor 2.

A rotation detecting plate 5 (for example, a disc in which magnetic substances and non-magnetic substances are alternately arranged in the rotation direction) as shown in FIG. 6 is coaxially attached to the rotation shaft of the disk motor 2. . A part of the circumference of the rotation detection plate 5 is arranged so as to pass through the gap portion of the magnetic head 6. As a result, a pulse output having a frequency proportional to the rotation frequency of the disk motor 2 is obtained from the magnetic head 6, and this pulse is input to the rotation detection circuit 7. Disk motor 2
When the brake voltage is supplied to the disk motor 2, the rotation speed of the disk motor 2 decreases as shown in FIG. Here, the rotation detector 7 indicates that the rotation speed of the motor 2 has become almost zero.
Is detected, a brake stop signal ST is obtained from the rotation detector 7. The brake stop signal ST is supplied to the brake voltage generation circuit 4 to stop the generation of the brake voltage. In other words, the brake voltage generation circuit 4 outputs a motor stop control signal to the motor drive circuit 3
Responds and outputs the motor stop voltage.

(Problems to be Solved by the Invention) According to the motor control circuit described above, mechanical rotation detecting means such as the rotation detecting plate 5 and the magnetic head 6 is required. Therefore, the parts arrangement around the motor is complicated, the number of parts is large, and the cost is high. Further, in order to accurately determine whether or not the rotation of the disk motor 2 has become completely zero, it is necessary to reduce the angle of the characteristic curve of the number of rotations to improve the resolution. For this purpose, the number of stages of the counter in the rotation detector 7 is increased to extend the time. In such a method, the brake voltage must be reduced, the time until stoppage becomes long, the detection time becomes long, and the circuit scale increases.

Therefore, an object of the present invention is to provide a motor stop detection circuit that can be realized at a low cost with a simple configuration and that can accurately detect a zero motor rotation speed state.

[Means for Solving the Problems] The present invention relates to a motor drive circuit for switching and outputting a forward rotation drive signal, a reverse rotation drive signal, and a stop signal to a DC motor, and to this motor drive circuit. A control circuit that supplies a control signal to control the output of the normal rotation drive signal, the reverse rotation drive signal, and the stop signal, and detects a signal proportional to the current flowing through the DC motor. A signal detection means and a signal value comparison means, and a first signal value when the normal rotation drive signal is output among the signals obtained from the signal detection means by the signal value comparison means, The second signal value when the reverse drive signal is output is compared, and the output from the signal value comparison means is such that the first signal value and the second signal value are substantially equal. When indicated, which is constituted to generate a timing signal for the stop signal output to said control circuit.

(Operation) By the above means, all the means for detecting the rotation state of the motor are realized by the electric circuit, and the conventional mechanical parts are unnecessary. For this reason, the structure around the motor is simplified, downsizing is achieved, and the number of parts is small and the motor can be realized at low cost. Further, the detection accuracy is high because the rotation is completely electric. Along with this, the brake voltage can be increased and a quick motor stop can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Disk motor
12 rotates, for example, the turntable 11 of the CD player. The disk motor 12 can be normally rotated by a normal rotation drive voltage from the motor drive circuit 13, and can be reversed by a reverse rotation drive voltage having a polarity opposite to this voltage. Also motor drive circuit
From 13, it is possible to supply a stop voltage of zero voltage to the disk motor 12.

The motor drive circuit 13 has transistors Q11, Q12, Q13, Q14, for example, as shown in FIG. When the input terminal IN1 is at high level and the input terminal IN2 is at low level, the transistors Q11 and Q14 are turned on, Q12 and Q13 are turned off, and the current i1 for forward rotation is applied to the motor. Conversely, the input terminal IN1 is low level and the input terminal Transistor Q1 when IN2 is high level
1, Q14 is off, Q12, Q13 is on, and the motor has a reverse current.
Stream i2.

Here, the operating current DI flowing through the drive circuit 13 flows through the load resistance RL, and its fluctuation state is shown in FIG.
Can be monitored at 20.

That is, referring back to FIG. 1, the operating current of the motor drive circuit 20 is supplied to the low-pass filter 20. The output of the low pass filter 20 is supplied to the first and second sample and hold circuits 21 and 22. In the sample hold circuits 21 and 22, the following sampling operation is performed. That is, after a minute period in which the polarity of the brake voltage is inverted from the reverse rotation drive voltage to the normal rotation drive voltage, for example, the sample hold circuit
Sampling in 21 is performed, and then in the sample-hold circuit 22, sampling is performed after a minute period in which the forward drive voltage application state is switched to the reverse drive voltage application state.

FIG. 3 is a timing chart showing the sampling operation when the braking operation is performed when the motor is rotating normally. FIG. 3 (a) shows the brake voltage,
The reverse rotation drive voltage V1 has a polarity opposite to that of the reverse rotation drive voltage V1.
V2 is superimposed. FIG. 3B shows the waveform of the motor drive current. When the motor drive current is switched from the current in the reverse rotation drive direction to the current in the forward rotation drive direction, that is, when a voltage that accelerates in the direction in which the motor is rotating is applied, the current in the forward rotation drive direction is reduced. The action to try works. Also, when the normal rotation direction drive current is switched to the reverse rotation direction drive current, in the situation where the motor is rotating in the forward direction, the reverse rotation drive current becomes the current to which the counter electromotive force of the motor is added. The current is larger than the drive current.
Here, when sampling this current change, the time points A and B indicated by white circles in FIG. 3B are alternately sampled by the first and second sample hold circuits 21 and 22.

On the other hand, the relationship between the motor drive current and the rotation speed of the motor is as shown in FIG. 4 when the drive voltage is constant. In FIG. 4, the reverse rotation portion of the horizontal axis representing the rotation speed shows the situation when the motor that is rotating forward is forcibly rotated in the reverse direction. It will be seen as a negative number of revolutions with respect to the drive voltage of the polarity. As can be seen from this figure, the motor drive current decreases as the number of rotations in the forward direction increases. At zero rotation speed, when the forward rotation drive voltage and the reverse rotation drive voltage are switched at the same duty at high speed and the forward rotation direction drive current becomes equal to the reverse rotation direction drive current, or a zero stop voltage is applied. That is the case. At this time as well, current is flowing through the drive circuit.

As can be seen from FIG. 4, when the brake voltage as shown in FIG. 3 (a) is supplied while the motor is rotating normally, the difference between the two sampled current values is large when the rotation speed is large. However, as the rotational speed gradually approaches zero, the difference becomes smaller, and when the rotational speed becomes zero, the two sampled current values become equal, as at the time points indicated by A'and B'in FIG. .

When the sampled values are equal as described above, the number of revolutions of the motor 12 is zero, so that the coincidence pulse obtained from the comparator 23 turns off the brake voltage control circuit 14 and Switching control is performed so that a stop voltage is applied to the drive circuit 13. As described above, according to the circuit of the present invention, it is possible to accurately detect that the number of rotations of the motor has become zero by sampling and comparing the drive currents at two points immediately after the polarity of the drive voltage is switched. be able to. As a means for applying a sampling pulse to the sample and hold circuits 21 and 22, a control signal provided to the brake voltage generation circuit 14 may be used, and the voltage directly output from the brake voltage generation circuit 14 may be used. You may make use of it and may make a sampling pulse.
Further, when the entire system is controlled by the digital control circuit, the pulse from the timing circuit may be used.

In the above embodiment, the change in the drive current is detected in an analog manner, but the drive current may be digitized and the rotation state of the motor may be determined by processing by a digital circuit. Further, in the above embodiment, the stop detection circuit of the disk motor used in the CD player or the LD player has been described, but the invention is not limited to the type of device.

[Effects of the Invention] As described above, since the present invention does not use a mechanical rotation detecting means as in the prior art, it can be realized at a low cost with a simple configuration. Further, even if the rotation of the motor becomes slow, it is possible to detect the stopped state reliably without taking time, and moreover, it is possible to accurately detect the zero state of the motor rotation speed. Furthermore, most of the time is effective in shortening the time until the motor is stopped because the drive voltage that maximizes the brake can be applied.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of the motor drive circuit of FIG. 1, and FIG. 3 is shown for explaining the operation of the circuit of FIG. A timing chart, FIG. 4 is a characteristic diagram showing the relationship between the rotation speed of the motor and the drive current, FIG. 5 is a diagram showing a conventional motor stop detection circuit, and FIG. 6 is the rotation detection plate of FIG. Figure, 7th
The figure is an explanatory diagram showing the relationship between the brake voltage and the motor speed in the circuit of FIG. 11 …… Turntable, 12 …… Disc motor, 13 ……
Motor drive circuit, 14 ... Brake voltage generation circuit, 20
...... Low pass filter, 21,22 …… Sample and hold circuit, 2
3 ... comparator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Minoru Yoneda 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Home Appliances Technology Laboratory, Toshiba Corporation Yokohama Works (72) Hiroshi Kobata Shin-isogo, Isogo-ku, Yokohama-shi, Kanagawa 33, Machi Toshiba Audio / Video Engineering Co., Ltd. Isogo Office

Claims (1)

(57) [Claims] 1. A motor drive circuit for switching and outputting a forward rotation drive signal, a reverse rotation drive signal and a stop signal to a DC motor, and a control signal supplied to the motor drive circuit to supply the forward rotation drive signal, In a motor drive system including a control circuit that controls the output of the reverse rotation drive signal and the stop signal, a signal detection unit that detects a signal proportional to a current flowing in the DC motor, and a signal detection unit that is obtained from the signal detection unit. Of the signals, a signal value comparison means for comparing a first signal value when the forward drive signal is output and a second signal value when the reverse drive signal is output, and the signal value Means for causing the control circuit to generate the timing signal for outputting the stop signal when the output from the comparing means indicates that the first signal value and the second signal value are substantially equal to each other. Motor stop detection circuit, characterized in that it comprises a.