JPH0236782A - Motor stop detector circuit - Google Patents

Abstract

PURPOSE:To shorten a period of time up to the stop of a DC motor by detecting the current of the motor from its driving circuit, comparing the current values at the times of outputting normal/reverse rotation driving voltages, and generating a stop voltage output timing signal. CONSTITUTION:A disc motor 12 rotates, for example, the turntable 11 of a CD player. The motor 12 is normally or reversely rotated by a normal/reverse driving voltage from a motor driving circuit 13, and a stop voltage of zero voltage is supplied from the circuit 13 to the motor 12. An operating current DI flowing to the circuit 13 flows to a load resistor RL, and its variation is monitored by a low pass filter 20. This filter output is sampled by first-second sample-holding circuits 21-22. Thus, a coincidence pulse from a comparator 23 when the sampled values become equal turns OFF a brake voltage controller 14, and so controls to switch it as to apply a stop voltage to the circuit 13.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a compact disc player (hereinafter referred to as 1.D
player), laser disc player (hereinafter referred to as LD)
This invention relates to a motor stop detection circuit used in a circuit that controls a disc motor such as a player.

(Prior Art) In a CD player or an LD player, for example, when a performance is finished and the disc is removed, it is necessary to wait until the rotation of the disc has completely stopped before moving on to the next process.

In order to stop the rotation of the disk, it is necessary to supply a brake voltage to the disk motor and turn off the brake voltage when the rotation of the motor reaches zero. If the off timing of the brake voltage is off, normal rotation may be maintained due to motor inertia.

Otherwise, the disc may become reversed, resulting in damage to the disc.

FIG. 5 shows a conventional DC motor control circuit, and shows the portion where the brake is applied to stop the motor.

The turntable 1 is rotated by a disk motor 2. The disk motor 2 can be driven forward or backward by a 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 applied to the motor drive circuit 3. Then, the motor drive circuit 3 generates a voltage of opposite polarity to the normal rotation drive voltage.

In other words, a reverse drive voltage is output and supplied to the disk motor 2.

A rotation detection plate 5 (e.g., a disk in which magnetic and non-magnetic materials are alternately arranged in the rotational direction) as shown in FIG. 6 is coaxially attached to the rotating shaft of the disk motor 2. .

A part of the circumference of the rotation detection plate 5 is covered by the magnetic head 6.
It is arranged so that it passes through the gap part of. As a result, a pulse output having a frequency proportional to the rotational frequency of the disk motor 2 is obtained from the magnetic head 6, and this pulse is input to the rotation detection circuit 7. When the brake voltage is supplied to the disc motor 2, the rotational speed of the disc motor 2 decreases as shown in FIG.

Here, when the rotation detector 7 detects that the number of rotations of the motor 2 has become almost zero, a brake stop signal ST is obtained from the rotation detector 7. This brake stop signal ST is supplied to the brake voltage generation circuit 4 to stop generation of the brake voltage. That is, the brake voltage generation circuit 4 outputs a motor stop control signal, and the motor drive circuit 3 responds to this signal and outputs a motor stop voltage.

(Problems to be Solved by the Invention) According to the above-described motor control circuit, mechanical rotation detection means such as the rotation detection plate 5 and the magnetic head 6 are required.

For this reason, the arrangement of parts around the motor is complicated, and the number of parts is large, increasing costs. Furthermore, in order to accurately determine whether the rotation of the disk motor 2 has completely reached zero, it is necessary to increase the resolution by reducing the angle of the characteristic curve of the rotation speed. For this purpose, the number of stages of the counter in the rotation detector 7 is increased to lengthen the time. With this method, the brake voltage must be reduced, and it takes a long time to stop.

As the detection time becomes longer, the circuit scale increases.

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

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a motor drive circuit that can supply a forward rotation drive voltage, a reverse rotation drive voltage, or a stop voltage to a DC motor, and a In a motor drive system comprising a control circuit that applies a control signal and controls the output period of the forward drive voltage, the reverse drive voltage, and the output timing of the stop voltage, the current detection means detects a current proportional to the current flowing through the DC motor. A current is detected from the motor drive circuit, and of the current obtained from the current detection means, a first current value after a minute period when the forward rotation drive voltage is output and a reverse rotation drive voltage are output. when the current value is compared with a second current value after a minute period when the current value is the same, and the output from the current value comparing means indicates that the first and second current values are equal. The control circuit is configured to generate a timing signal for outputting the stop voltage.

(Function) With the above means, all the means for detecting the rotational state of the motor are realized by electric circuits, and conventional mechanical parts are not required. For this reason, the configuration around the motor is simple and compact, and the number of parts is small and the motor can be realized at low cost. Furthermore, since the rotation is detected completely electrically, the detection accuracy is increased. Accordingly, the brake voltage can also be increased, and the motor can be stopped quickly.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Disc motor 1
2 rotates the turntable 11 of a CD player, for example. The disk motor 12 has a motor drive circuit 1
It is possible to rotate in the forward direction with the forward rotation drive voltage from 3, and to reverse rotation with the reverse drive voltage of the opposite polarity to this voltage. Further, the motor drive circuit 13 can supply a zero stop voltage to the disk motor 12 .

The motor drive circuit 13 includes transistors Q-11, Q12, Q13, and Q14, as shown in FIG. 2, for example. When input terminal INI is at high level and input terminal IN2 is at low level, transistors Qll and Q14 are on, Q12.013 is off, and a current for forward rotation is supplied to the motor! ■ flows, and conversely input terminal INI is low level, input terminal IN
When 2 is at a high level, transistors Q11SQ14 are turned off, Q12 and Q13 are turned on, and the motor receives a current of 1 for reverse rotation.
Run 2.

Here, the operating current DI flowing through the drive circuit 13 flows through the load resistor RL, and its fluctuation can be monitored by the low-pass filter 20 shown in FIG.

That is, returning 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 first and second sample and hold circuits 21 and 22. In the sample and hold circuits 21 and 22, the following sampling operation is performed. That is, after a minute period during which the polarity of the brake voltage is reversed from the reverse drive voltage to the forward drive voltage, sampling is performed in the sample and hold circuit 21, for example, and then the state of applying the forward drive voltage is switched to the state of applying the reverse drive voltage. After the short period, sampling in the sample hold circuit 22 is performed.

FIG. 3 is a timing chart showing a sampling operation when a brake operation is performed while the motor is rotating normally. FIG. 3(a) shows the brake voltage, in which a forward rotation drive voltage v2 of opposite polarity is superimposed on the reverse rotation drive voltage v1. FIG. 3(b) shows the waveform of the motor drive current. When the motor drive current is switched from a current in the reverse drive direction to a current in the forward drive direction, that is, when a voltage is applied that accelerates the motor in the direction in which it is rotating, the current in the forward drive direction is reduced. The effect of trying to do this works. In addition, when switching from the forward direction drive current to the reverse direction drive current, when the motor is rotating in the forward direction, the reverse drive current becomes a current to which the back electromotive force of the motor is added, so The current is larger than the drive current.

Here, when sampling this current change, time points A and B indicated by white circles in FIG. 3(b) are sampled alternately by the first and second sample-and-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, assuming that the drive voltage is constant. In Fig. 4, the reversal portion of the horizontal axis representing the rotation speed shows the situation when a motor that is currently rotating in the normal direction is forcibly reversed, and when a reverse drive voltage is applied to the motor that is currently rotating in the normal direction,
In other words, a drive voltage of opposite polarity will be viewed as a negative rotational speed. As can be seen from this figure, as the rotation speed in the normal rotation direction increases, the motor drive current decreases.

At zero rotation speed, if the forward rotation drive voltage and reverse rotation drive voltage are switched at high speed with the same duty and the forward rotation drive current and reverse rotation drive current become equal, or when a stop voltage of zero is applied. This is the case. Also at this time, current is flowing through the drive circuit.

As shown in Fig. 4, when the motor is rotating in the normal direction, if a brake voltage as shown in Fig. 3(a) is applied,
When the rotation speed is large, the difference between the two sampled current values is large, but as the rotation speed approaches zero,
When the difference becomes smaller and the rotational speed becomes zero, as shown at the point AB- in FIG. 3, the two sampled current values become equal.

When the sampled values are equal as shown above,
Since the rotational speed of the motor 12 is zero, the matching pulse obtained from the comparator 23 turns off the brake voltage control circuit 14 and performs switching control to apply a stopping voltage to the motor drive circuit 13. do. In this way, according to the circuit of the present invention, the polarity of the drive voltage is
By sampling and comparing the drive currents at points, it is possible to accurately detect when the motor rotation speed has reached zero. In addition, the sample hold circuit 21.2
As a means of giving a sampling pulse to 2,
The control signal given to the brake voltage generation circuit 14 may be used, or the sampling pulse may be generated using the voltage directly output from the brake voltage generation circuit 14.

Furthermore, if the entire system is controlled by a digital control circuit, pulses from the timing circuit may be used.

Although the above embodiment has been described as detecting changes in the drive current in an analog manner, the drive current may be digitized and the rotation status of the motor may be determined through processing by a digital circuit. Further, in the above embodiment, the stop detection circuit for a disk motor used in a CD player or an LD player has been described, but the present invention is not limited to the type of equipment.

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

[Brief explanation of the drawing]

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 shown in FIG. 1, and FIG. 3 is a circuit diagram showing an example of the motor drive circuit shown in FIG. 1. Fig. 4 is a characteristic diagram showing the relationship between motor rotation speed and drive current, Fig. 5 is a diagram showing a conventional motor stop detection circuit, and Fig. 6 is a diagram showing the rotation detection plate of Fig. 5. , FIG. 7 is an explanatory diagram showing the relationship between brake voltage and motor rotation speed in the circuit of FIG. 5. DESCRIPTION OF SYMBOLS 11... Turntable, 12... Disc motor, 13... Motor drive circuit, 14... Brake voltage generation circuit, 20... Low pass filter, 21.22.
...Sample and hold circuit, 23...Comparator. 1st co-applicant's agent Patent attorney Takehiko Suzue g2:A drop 3 5th figure stem 6 figure

Claims (1)

[Scope of Claims] A motor drive circuit that can switch and supply a forward rotation drive voltage, a reverse rotation drive voltage, and a stop voltage to a DC motor; a control circuit that controls the output period of the drive voltage and the output timing of the stop voltage; a current detection means that detects, from the motor drive circuit, a current proportional to the current flowing through the DC motor; and a current obtained from the current detection means. Among them, a current value comparison that compares a first current value after a minute period when the forward rotation drive voltage is outputted and a second current value after a minute period when the reverse rotation drive voltage is outputted. and means for causing the control circuit to generate a timing signal for outputting the stop voltage when the output from the current value comparison means indicates that the first and second current values are equal. A motor stop detection circuit featuring: