JPS6141065B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arm driving circuit in an arm feeding device for a video disc player.

FIG. 1 shows a system diagram of the arm feeding device and needle control section of a video disc player.

In FIG. 1, a recorded signal on a video disk 10 is read with a pick-up stylus tip 1. The read signals include video signals (including audio signals) and track signals. Therefore, the signal processing circuit 2 separates the two signals using, for example, a bandpass filter.

The video signal is transmitted to the video circuit 3, where it undergoes appropriate processing, and the image recorded on the video disk 10 is projected onto the cathode ray tube. On the other hand, the track signal is sent to the needle control circuit 4, and the coil drive circuit 5 drives the needle control coil 6. Then, using the magnetic field of the coil 6 and the attraction and repulsion of the magnet 7, the pick-up needle 9 is moved using a point 8A on the support rod 8 as a fulcrum, and the pick-up needle tip 1 tracks the signal recorded on the video disk 10. Control is performed so that the playback is performed without any problem.

Furthermore, the amount of displacement of the pickup needle 9 is detected by the coil drive circuit 5, and is compared with a reference voltage 13 by a comparator 12 through a low-pass filter 11. When the amount of displacement of the pick-up needle 9 exceeds the set value of the comparator 12, a signal is output to the operating circuit 14 to drive the drive motor 16 of the arm 20 for an arbitrary set time. Then, motor drive circuit 1
5 is energized, the motor 16 is driven for an arbitrary set time, and the arm 20 is moved an arbitrary distance via the deceleration mechanism 17, pulley 18, and belt 19. At this time, since there is a possibility that the pick-up needle tip 1 may cause track deviation, the output of the comparator 12 is fed back to the needle control circuit 4 to prevent track deviation.

FIG. 2 shows a coil drive circuit 5, a low-pass filter 11, a comparator 12, and a motor drive circuit 1.
5 shows a detailed circuit configuration example.

In FIG. 2, the signal from the signal processing circuit 2 is processed by the needle control circuit 4, drives the coil drive amplifier 5A, changes the current flowing through the needle control coil 6, attracts the magnet 7 attached to the pick-up needle, The pick-up needle is controlled by using repulsive force. This control current is detected as a voltage change by the resistor 5B, amplified by the differential amplifier 21 via the low-pass filter 11, and then applied to the positive input terminal of the differential amplifier 22A constituting the hysteresis comparator 22.

When the current flowing through the needle control coil 6 exceeds the value set in the hysteresis comparator, the output of the differential amplifier 22A changes instantaneously from a low level to a high level. This output is fed back to the needle control circuit 4 as described above, and is also applied to the monostable multivibrator 23.
The transistor 25 is turned on for the arbitrary time set in step 3, and the motor 16 is driven.

The setting time of the aforementioned monostable multivibrator 23, that is, the moving distance of the arm 20 by the motor 16, is within a dynamic range in which at most the movement of the arm 20 can be covered only by the rotational movement of the pick-up needle 9. must be selected. On the other hand, if the time is too short, the torque of the motor (DC motor) 16 will not be large enough to drive the arm 20, and therefore the motor 16 will not rotate and the arm 20 will not be driven. There will be no.

Through the above-described operation, the arm 20 is moved an arbitrary distance according to the movement of the pick-up needle 9, but if the drive time of the motor 16 is short or
There may be cases where the amount of movement of the arm 20 is small due to various causes such as a non-operating section of the mechanical system between the motor 16 and the arm 20. In such a case, the current flowing through the needle control coil 6 will not decrease sufficiently,
There may be cases where the input voltage to the hysteresis comparator 22 does not fall below the set value.

Therefore, the output of the differential amplifier 22A constituting the hysteresis comparator 22 does not return from a high level to a low level, but remains at a high level. After this condition occurs, the monostable multivibrator 23 will no longer be triggered and therefore its output will no longer flip from a low level to a high level. Therefore, the motor 16 is not driven, and even if the amount of displacement of the pick-up needle tip 1 exceeds the set value of the hysteresis comparator 22, the arm 20 does not move.

SUMMARY OF THE INVENTION An object of the present invention is to provide an arm drive circuit for a video disc player that eliminates the above-mentioned drawbacks of the prior art and allows normal arm feeding at all times.

The key point of the present invention is that after driving the arm drive motor with a monostable multivibrator for an arbitrary period of time using a signal in which the output of the hysteresis comparator changes from a low level to a high level, the output of the hysteresis comparator is forced from a high level to a low level. The reason is that it is configured to return to the target.

An embodiment of the invention is shown in FIG.

Similarly to FIG. 2, FIG. 3 shows a coil drive circuit 5, a low-pass filter 11, a comparator 12,
A detailed circuit configuration example of the motor drive circuit 15 is shown.

In FIG. 3, as in the conventional example, the signal from the signal processing circuit 2 is processed by the needle control circuit 4, the coil drive amplifier 5A is driven, and the current flowing through the needle control coil 6 is controlled. Detect this current with a resistor 5B,
After passing through the low-pass filter 11 and amplifying it with the differential amplifier 21, it is applied to the positive input terminal of the differential amplifier 22A constituting the hysteresis comparator 22.

When the current flowing through the needle control coil 6 exceeds the set value of the hysteresis comparator 22, the differential amplifier 2
The 2A output changes instantly from low level to high level. This output is sent to the needle control circuit 4 as described above.
At the same time, it is applied to the monostable multivibrator 23. Monostable multivibrator 23
When the input is applied, the transistor 25 is turned on for a set arbitrary time, and the motor 16 is driven.

In the present invention, this monostable multivibrator 2
The inverted output of the monostable multivibrator 23 is configured to be fed back to the negative input terminal of the differential amplifier 22A via the differentiating circuit 27, and when the inverted output of the monostable multivibrator 23 is inverted from a low level to a high level, the differential amplifier 22A The negative input terminal of the differential amplifier 22A is momentarily brought to a high level, and the output of the differential amplifier 22A is forced to a low level.

By operating in this manner, the position of the pick-up needle 9 is adjusted to the hysteresis comparator 2.
When the set value of 2 is exceeded, the arbitrary setting time arm 2
Drive the motor that drives 0. In this case, the amount of displacement of the pick-up needle 9 may exceed the output of the hysteresis comparator 22 due to the influence of, for example, the drive time of the motor 16 being short or the motionless section (play) of the mechanical system between the motor 16 and the arm 20. Arm 20 is only far enough away to return to the initial low level.
Even if hysteresis comparator 2 does not move,
The output of No. 2 is reliably returned to a low level again by the above operation.

Therefore, if the amount of displacement of the pick-up needle 9 exceeds the amount set by the hysteresis comparator 22 again thereafter, the monostable multivibrator 23 is activated and the motor 16 can be reliably driven.

Although the above description has been made regarding the case where the arm is sent in the forward direction, it will be easily understood that the case where the arm is sent in the reverse direction can be carried out in the same manner.

Also, although in the example described above the output of the multivibrator 23 is used to restore the hysteresis comparator 22, it is clear that any other suitable signal could be used, such as an inverted version of the output of the differential amplifier 22A. be.

As described above, according to the present invention, when the pick-up needle is displaced beyond the amount set in the hysteresis comparator, in a device configuration in which the arm is moved an arbitrary distance, the arm does not move sufficiently due to various factors, and the hysteresis occurs. The problem that the comparator does not reverse and normal arm feeding is not possible can be solved by a simple method.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of the arm feeding device and pick-up needle control section of a video disc player, FIG. 2 is a detailed block diagram of the conventional arm drive circuit shown in FIG. 1, and FIG. 3 is a diagram showing one embodiment of the present invention. FIG. 2 is a block diagram similar to FIG. 2 shown in FIG. 1... Pick-up needle tip, 2... Signal processing circuit, 3... Video circuit, 4... Needle control circuit, 5...
Coil drive circuit, 6... needle control coil, 9... pick-up needle, 10... video disk, 15...
...Motor drive circuit, 20...Arm, 21, 22
A differential amplifier 2, hysteresis comparator, 2
3... Monostable multivibrator, 24... Power supply.

Claims (1)

[Claims] 1 A circuit that detects the amount of displacement of the pick-up needle,
A hysteresis comparator that compares the amount of displacement of the pick-up needle with a set value and inverts the output when the amount of displacement exceeds the set value, and a hysteresis comparator that detects that the output of the comparator has been reversed and sets an arbitrary set time. In the arm drive circuit of a video disc player, the arm drive circuit for a video disc player is provided with a means for driving a motor for moving the arm, and after the motor drive means is energized, a signal of opposite polarity is supplied to the comparator to invert its output again. An arm drive circuit for a video disc player, characterized in that the arm drive circuit is configured to