JPH055234B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a motor drive device for an electronic still camera. More specifically, the present invention relates to a drive device for a motor for controlling disk rotation in an electronic still camera that integrates a recording means using a magnetic disk.

[Background of the invention]

This type of motor drive device is configured to reset the vertical synchronization signal so as to synchronize it with the PG signal generated as the motor rotates when the rotation reaches a specified rotation, thereby effectively reducing the motor's rise time. The applicant previously proposed a shortened version, but when applying this to a motor drive device for electronic still cameras, if a motor with low inertia such as a coreless motor is used as the motor, the shutter button can be shortened. It is also possible to perform an operation such as starting the motor at the time of release. In this case, the motor only needs to be rotating from the shutter button release to the completion of recording, which reduces power consumption and magnetic head drive. It also reduces wear and tear.
However, since it is installed in a small camera for an electronic still camera, the use of a brushless DC motor will naturally be considered since it is advantageous in terms of space. But brushless
A DC motor has several times the inertia of a coreless motor, and if the motor starts when the shutter button is released, it will take too long to become possible to record, and there is a risk that the video signal will deteriorate. In addition, when pre-rotating the motor to enable recording by performing an action prior to recording during a shooting sequence, such as pressing the shutter button halfway, the photographer may sometimes aim to press the shutter button halfway. This is undesirable because power consumption and wear of the magnetic head due to driving the motor during preliminary rotation increase.

Also, even when using a coreless motor, it is difficult to supply a large current when starting rotation with electronic still cameras, which have limited power supply capacity, so the motor starts when the shutter button is released. The problem was that it took too much time.

[Purpose of the invention]

The present invention has been made in view of these shortcomings in the prior art, and it shortens the time from motor startup to when shutter release is possible, from shutter release to start of recording, and reduces the time required for preliminary rotation of a magnetic disk. The present invention aims to realize a motor drive device with a simple configuration that reduces power consumption and wear of the magnetic head.

[Summary of the invention]

The present invention starts the rotation of the motor in a preliminary shooting operation prior to recording such as pressing the shutter halfway, controls the preliminary rotation at a speed within a certain range lower than the rated rotation speed, and records the video signal on the magnetic disk. The technical point is to shift the phase of the video signal so that the phase of the vertical synchronization signal of the video signal coincides with the rotational phase of the magnetic disk immediately before the magnetic disk.

[Explanation of Examples]

FIG. 1 is a block diagram showing an example of a device according to the present invention. In this figure, 1 is a brushless DC motor, 2 is a magnetic disk rotated by the DC motor 1, and 3 is a magnetic head for recording on this magnetic disk 2. During recording, a signal is sent from a video signal processing circuit 5 via a switch 4. Recording current is supplied. 6
7 is a frequency generator (hereinafter abbreviated as FG) that outputs a frequency signal (FG signal) corresponding to the rotation of the magnetic disk 2; 7 is a phase signal generator (hereinafter abbreviated as PG);
Hall elements 8 and 9 detect the rotation of the motor 1, and the motor 1 is rotated by a control circuit 10 and a drive circuit 11. Reference numeral 12 denotes a servo circuit, which controls the speed of the motor 1 based on the FG signal outputted from the FG 6 so that the period of one rotation of the motor 1 coincides with the vertical synchronization period. 13 is a jitter detection circuit, FG
Based on the signal, it is detected whether the rotation speed of the motor 1 is recordable. 14 is a synchronizing signal generator, and the phase of the VD signal is changed by a signal applied to a reset terminal. 15 is a PG signal output from PG7, a release signal, and a jitter detection circuit 13
This is a recording timing control circuit which inputs signals from the synchronous signal generator 14 and outputs a signal l to be applied to the reset terminal of the synchronization signal generator 14 and a drive signal m to the switch 4. 16, 17 are retriggerable monostable multivibrators (hereinafter abbreviated as RMM), 18,
19 is a D flip-flop (hereinafter abbreviated as DFF),
20 is an AND gate, and 21 is an OR gate.
The portion surrounded by this one-dot chain line constitutes a characteristic circuit in the present invention.

Figures 2 and 3 are timing charts for explaining the operation of the device in Figure 1. Figure 2 shows the speed control operation by switching during preliminary rotation, and Figure 3 shows the timing of the overall operation. It shows.

From the servo circuit 12 to RMM16 and 17
Pulse width T ₁ output at a period corresponding to the FG signal
A pulse signal a as shown in FIG. 2a is applied. The pulse widths of RMM16 and 17 are T ₂ and T ₃ (T ₃ >
T ₁ + T ₂ ), and from here on, the second
Pulse width signals b and c as shown in FIGS. b and c are output. In the DFF 18, the pulse width signal b from the RMM 16 is applied to the D input terminal, the a signal is applied to the CK terminal, and the pulse width signal c from the RMM 17 is applied to the R terminal. Therefore, when the period of the FG signal is within T ₁ + T ₂ , the D input terminal is at “H” level and the CK input rises, so the output _goes to “ _L ” level. At this time, the D input terminal is at "H" level and the CK input rises, so the output becomes "H" level.
To prevent malfunction, when the period of the FG signal exceeds _T3 , the DFF 18 is reset and the output becomes "H" level. This output signal d is shown in Figure 2 d.
Shown below.

The output signal d of the DFF 18 is applied to the motor control circuit 10 through an AND gate 20 and an OR gate 21, which are turned on when the shutter button is pressed halfway, and turns on the motor 1 when the period of the FG signal is T ₁ + T ₂ or more. , T ₁ + T ₂ , a switching operation is performed to turn off the motor 1, and the motor 1 is rotated at a constant rotation speed or higher. Note that during this preliminary rotation, the motor 1 is rotating at a speed below the rated rotation speed, so the servo circuit 12 always operates to supply the maximum voltage to the motor, and the servo circuit 12
Preliminary rotation speed control can be realized by switching operation without changing the configuration.

Next, the overall operation will be explained with reference to FIG. First, as shown in FIG. 3e, when the signal e caused by half-pressing the shutter button is applied to the AND gate 20 at time _t1 , the signal d from the output of the DFF 18 passes through here, and passes through the OR gate 21 to the control circuit. 10, and a voltage is applied to the motor 1 as shown in FIG. 3g. As a result, the rotation speed of the motor 1 gradually increases as shown in FIG. 3h, and eventually enters a pre-rotation state due to the switching operation.

DFF19, after pressing the shutter button halfway,
“H” at the first falling edge of DFF18 output
level, and at this time, since the rotational speed of the motor 1 is above a certain value, this is output as a photographing enable signal n as shown in FIG. 3n. This signal n is
It is used for the LED display inside the viewfinder and for operations such as releasing the shutter release lock. In the pre-rotation state of motor 1, the motor voltage is as shown in Fig. 3g.
As shown in the figure, it is turned on and off by switching operation, and the power consumption can be reduced compared to when the servo is applied at the rated speed. Also, since the control speed is slower than the rated speed, wear on the head can be reduced. .

When the shutter is released at time _t2 as shown in FIG.
An H level is applied to one input terminal of the OR gate 21 to maintain the output of the OR gate 21 at an H level. Here, the timing control circuit 15 outputs an H level at least until the fall of the recording control signal shown in FIG. 3m, so that the output of the OR gate 21 is kept at an H level. As a result, the motor 1 is always on, the servo circuit 12 is operated, and the motor is turned on as shown in FIG.
As shown in the figure, it is controlled at the rated rotation speed (3600r.pm) and becomes ready for recording. At this time _t3 , the output signal i of the jitter detection circuit 13 becomes "H" level as shown in FIG. 3i, and VD is reset.
After the phases of the PG signal and the VD signal are matched as shown in FIG. 3 j, k, l, the timing control circuit 1
5 outputs a recording control signal m as shown in FIG. 3m to the switch 4, and recording on the magnetic disk 2 is performed.

In this way, even when using a motor with large inertia such as a brushless motor, or a motor with small inertia such as a coreless motor, even when driving with a power supply that cannot supply a large current at startup, preliminary rotation is required. By doing so, even if the servo circuit is operated after the shutter release, the time until the recordable state is achieved can be shortened, and therefore, it is not necessary to always operate the servo circuit by pressing the shutter button halfway.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a motor drive circuit that can reduce power consumption and wear of the head even when a motor with large inertia is used and a power supply with a small capacity is used. Further, since the shutter can be released when the rotational speed of the motor exceeds a certain value, the time required for the shutter to be released after pressing the shutter button halfway can be shortened.

Furthermore, when the motor reaches the rated rotational speed after the shutter release, the video signal is phase-shifted so that the phase of the vertical synchronization signal of the video signal matches the rotational phase of the magnetic disk, so recording starts from the shutter release. You can shorten the time it takes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the apparatus according to the present invention, and FIGS. 2 and 3 are timing charts for explaining the operation of the apparatus shown in FIG. DESCRIPTION OF SYMBOLS 1... Motor, 2... Magnetic disk, 3... Magnetic head, 4... Switch, 5... Video signal processing circuit, 10... Motor control circuit, 11... Motor drive circuit, 12... Servo circuit, 16,17...
RMM, 18, 19...DFF, 20...and gate, 21...or gate.

Claims (1)

[Scope of Claims] 1. In a motor drive device for an electronic still camera that includes a motor that rotates a magnetic disk, the motor is started by a preliminary photographing operation prior to recording on the magnetic disk, and the rotation speed of the motor is lower than or equal to the rated rotation speed of the motor. a first control means for pre-rotation control based on speed; a first detection means for detecting that the rotation speed of the motor has reached a certain range below the rated rotation speed and releasing the shutter release lock; a second control means for controlling the rotation of the motor to the rated rotation speed based on a tar release signal; a second detection means for detecting that the motor has reached the rated rotation speed; a phase shifting means for shifting the phase of a video signal to be recorded on the magnetic disk based on a signal so that the phase of a vertical synchronization signal of the video signal matches the rotational phase of the magnetic disk; A motor drive device for an electronic still camera, comprising: third control means for outputting a signal to start recording on the magnetic disk after the phase shift is performed.