JPH01258266A - Motor driving circuit - Google Patents

Abstract

PURPOSE:To securely detect abnormal high speed revolution or stopping condition, etc., with the constitution of a low cost and to execute control by detecting motor speed by utilizing back electromotive force obtained in a motor terminal. CONSTITUTION:When information from a disk can not be read during reproducing in a compact disk player, etc., a microcomputer 26 turns off a switch 20 and interrupts the supply of a driving voltage to a motor 12. In such a condition, the terminal voltage of the motor 12 is compared with a prescribed reference voltage Vref by a comparator 22 and when the terminal voltage is higher than the voltage Vref, abnormal high speed revolution detecting information are outputted from the comparator 22 and transmitted to a control IC 10. The IC 10 outputs a brake signal based on these information and brake is loaded through a motor driver 18 and the switch 20. After that, the switch 20 is periodically turned off and a revolving condition is detected. Then, when the information can be exactly read, operation is returned to a reproducing condition by the normal control. Then, the control can be executed without fail.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a drive circuit for a motor in a disc motor of a CD (compact disc) player or an LV (laser vision disc) player, or in a piece of music equipment. The rotational speed of the motor can be detected accurately with a simple configuration, and the rotation of the motor can be reliably controlled to a predetermined state.

[Conventional technology]

The speed of a disc motor in a CD player, LV player, etc. is controlled based on a frequency and phase comparison between a clock signal reproduced from a disc reproduction signal and a reference tarlock signal.

[Problem to be solved by the invention]

In such speed control, if the motor rotation becomes abnormally high speed for some reason, the clock signal is no longer regenerated, so the motor continues to be in an abnormal rotation state and cannot be returned to a normal state.

In order to solve this problem, some models installed an FG (frequency generator) on the motor so that the motor rotation could be detected even when the tarot signal was not regenerated, but since the FG is required, It had the disadvantage of high cost.

The present invention solves the problems in the conventional technology, and provides a motor that allows the rotational speed of the motor to be detected accurately with a simple configuration, and that allows the rotation of the motor to be reliably controlled to a predetermined state. It is intended to provide a driving circuit.

[Failure to solve the problem]

The motor drive circuit of the present invention includes a drive voltage cutoff means for cutting off the supply of drive voltage to the motor, and detects the terminal voltage of the motor when the supply of drive voltage to the motor is cut off by the drive voltage cutoff means. The motor terminal includes a motor terminal voltage detection means and a motor drive control means for controlling the drive of the motor based on the detection result.

[For production]

According to this invention, when the supply of drive voltage to the motor is cut off by the drive voltage cutoff means (including not only the case of complete cut-off, but also the case of partial cut-off), the motor terminal is connected to the drive voltage corresponding to the motor speed. Since a back electromotive force is generated, by detecting the motor terminal voltage (not limited to the terminal voltage itself, but any voltage that corresponds to the terminal voltage, such as a voltage obtained by dividing the terminal voltage) using the motor terminal voltage detection means. The motor speed is detected and the motor drive control means can control the motor to a predetermined speed.

According to this, since the back electromotive force obtained at the motor terminals corresponds to the motor speed over a wide speed range, abnormal high-speed rotation, etc. can be reliably detected.

Therefore, rotation detection means such as FG is not required.

It can be constructed at low cost. Furthermore, if the motor terminal voltage is detected while the drive voltage is being supplied to the motor, the motor drive voltage will be superimposed, making it impossible to detect the motor speed with high precision. Since the motor terminal voltage is detected in the cut-off state, the influence of the motor drive voltage is eliminated, and the motor speed can be detected with high accuracy.

Note that if the drive voltage is cut off periodically, the motor speed can be detected periodically, and the rotation of the motor can be controlled more reliably.

[Embodiment] An embodiment of the present invention is shown in FIG. 1. This motor drive circuit can be applied, for example, as a disk motor drive circuit for a CD player or an LV player.

The control IC10 constitutes a motor drive control means, and is used to control the motor 12 to a predetermined speed based on various operation commands given by key operations, rotation information of the motor 12 inputted to the terminal l/1, etc. A drive signal is output from the terminal 16.

This drive signal is transmitted to the motor driver 18 and the switch 20.
is applied to the motor 12 via the motor 12 to drive the motor 12 at a predetermined speed.

Since the switch 20 constitutes drive voltage cutoff means, a bidirectional analog switch can be used, for example. When this switch 20 is turned on, it changes the driving voltage to the motor 1.
2, and when it is turned off, the supply of drive voltage is cut off.

The comparator 22 constitutes motor terminal voltage detection means, detects the terminal voltage of the motor 12, and detects the reference voltage V
The speed ef of the motor 12 (in this embodiment, whether it is faster or slower than the speed ef corresponding to the reference voltage V 1 ) is detected.

As shown in Figure 2, the open terminal voltage of a DC motor has a correspondence relationship with the motor speed over a wide range, so
This terminal open voltage allows the motor speed to be detected over a wide range.

The microcomputer 26 inputs the speed detection result output from the comparator 22 and outputs it to a terminal 28 as rotation information of the motor 12 (for example, information for determining whether it is rotating or stopped, information for determining an abnormally high speed state, etc.)
It is output from and fed back to the control IC10. Based on this rotation information, the control IC10 outputs a drive signal to control the drive of the motor 12 so that a predetermined rotation state given by the operation command is achieved.

Further, the microcomputer 26 outputs an on/off signal for the switch 20 from a terminal 30, and the comparator 22 outputs an on/off signal for the switch 20 from the terminal 30, and the off signal causes the comparator 22 to
The output of During the period when the drive voltage is being supplied to the motor 12, the terminal voltage of the motor 12 is the motor back electromotive voltage superimposed with the motor drive voltage, so a detection result that accurately corresponds to the motor speed cannot be obtained. However, since the detection results are captured during the period when the drive voltage is cut off,
Detection results that accurately correspond to motor speed can be obtained.

Note that during the OFF period of the switch 20, the drive of the motor 12 is temporarily interrupted, so it is desirable that the length of the OFF period be a short period that allows detection of the motor terminal voltage. Also, if the on/off signal is given periodically, the motor 1
2 speeds can be detected periodically.

According to the motor drive circuit shown in FIG. 1, various rotation states can be detected by setting the reference voltage ef. An example of rotation state detection will be explained.

(1) Detection of abnormally high speed state Suppose that a CD player, LV player, etc. becomes unable to read information from a disc for some reason during playback. At this time, it is detected by the following method whether or not the carrier 12 is rotating at an abnormally high speed.

An off signal is output from the terminal 30 of the microcomputer 26 to turn off the switch 20 and cut off the supply of drive voltage to the motor 12. In this state, the comparator 22 compares the terminal voltage of the motor 12 with the reference voltage (2). Note that at this time, the reference ef voltage Vref is set to a voltage value at which abnormally high speed rotation is determined.

If the terminal voltage of the motor 12 is higher than the reference voltage ef, the comparator 22 outputs abnormal high speed rotation detection information, and the information is transmitted to the control IC10 via the microcomputer 26. Control I
Based on this information, Cl0 outputs a brake signal (reverse voltage signal) as a drive signal, drives the motor 12 in the reverse direction via the motor driver 18 and switch 20, and applies the brake. Switch 20 is periodically turned off to turn off motor 1.
When the rotational state of the disc 2 is detected and the information on the disc can be read normally, the control IC10 outputs a drive signal based on a frequency and phase comparison between the reproduced clock and the reference clock. Then, the microcomputer 26 stops outputting the off signal, the switch 20 remains on, the motor 12 is controlled to a predetermined speed by the drive signal, and the regeneration state is returned.

(2) Detection of rotation stop state FIG. 3 shows an example of the operation when stopping the rotation from the regeneration state or the above-mentioned abnormal high speed state. At this time, control ICl0
A brake signal (reverse voltage signal) is output as a drive signal. Then, terminal 3 of the microcomputer 26
From 0, an on/off signal is periodically output to turn the switch 20 on and off. As shown in FIG. 3, T1 is an off period and T2 is an on period. During the off-period T1, the terminal voltage of the motor 12 is compared with the reference voltage ■. At this time, the reference voltage Vref is set to a value at which it is determined that the motor 12 is almost in a stopped state (that is, near zero).

When the brake is applied to the motor 12 and its terminal voltage becomes lower than the reference voltage ■, the output of the brake signal ef is stopped, and the drive of the motor 12 is stopped.
The motor 12 then stops completely. Further, the output of the on/off signal from the microcomputer 26 is also stopped.

In addition, the reference voltage ■,. If the value of 1 is automatically switched according to the detection contents, various rotation states can be detected.

[Example of change]

In the embodiment described above, the specific rotation state was detected by the comparator 22, but the terminal voltage of the motor 12 is input to the A/D converter fA input terminal of the microcomputer 26,
It can also be configured to digitally compare and detect within the microcomputer 26.

Moreover, this invention does not use a comparator, but the motor 12
motor 1 based on the deviation between the detected terminal voltage value and the set value.
It is also possible to apply servo control to a predetermined rotational state.

Further, in the embodiment described above, a case was shown in which a drive voltage cutoff means (switch 20) was inserted between the motor drive means (motor driver 18) and the motor 12, but the motor 12
As long as it is possible to cut off the supply of driving voltage to the motor, it may be placed before the motor driving means or within the motor driving means.

Further, the present invention can be applied to motor drive circuits other than disk motors of CD players and LV players, and can also be applied to drive circuits of motors other than DC brush motors (for example, DC brushless motors).

〔Effect of the invention〕

As explained above, according to the present invention, since the motor speed is detected using the back electromotive voltage obtained at the motor terminals, abnormal high speed rotation, stopped state, etc. can be reliably detected. Therefore, rotation detecting means such as FG is not required, and the structure can be constructed at low cost. Furthermore, since the motor terminal voltage is detected while the supply of drive voltage to the motor is cut off, the influence of the motor drive voltage is eliminated, and the motor speed can be detected with high accuracy.

Note that if the driving voltage is periodically cut off as shown in the embodiment, the motor speed can be detected periodically and the rotation of the motor can be controlled more reliably.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a speed-to-terminal open circuit voltage characteristic diagram of a DC motor. FIG. 3 is a waveform diagram showing the operation of the circuit of FIG. 1 when a stop command is given. 10... Control IC (motor drive control means),
12... DC brush motor, 18... Motor driver, 20... Switch (driving voltage cutoff means), 22...
...Comparator (motor terminal voltage detection means).

Claims (2)

[Claims] (1) A drive voltage cutoff means that cuts off the supply of drive voltage to the motor; and a motor terminal voltage detection means that detects the terminal voltage of the motor when the drive voltage cutoff means cuts off the supply of drive voltage to the motor. and a motor drive control means for controlling the drive of the motor based on the detection result. (2) The motor drive circuit according to claim 1, wherein the drive voltage cutoff means is operated periodically.