JPH0847295A - Motor controller - Google Patents

Abstract

PURPOSE:To always drive a motor stably by monitoring a power supply voltage level, reducing the duty of a PWM output when the power supply voltage level exceeds a reference level, and applying the power supply voltage in synchronization with the PWM output. CONSTITUTION:When the loading signal of PWM is inputted to a LOAD input terminal 4, a power supply voltage is applied to a motor 8 only during the H level of PWM and the motor 8 is rotated in loading direction. Similarly, when the loading signal is inputted to an UNLOAD input terminal 27, the motor 8' rotates in unloading direction. Then, since the duty of PWM is compensated according to a voltage level, the application time of the power supply voltage to the motor 8 decreases by 10% by causing the duty of PWM to decrease by 10% when the power supply voltage is higher than a reference level R by 10%, thus achieving a situation where the reference level R is applied with a duty of 90%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a camera-integrated V
Used for TR, the magnetic tape is pulled out from the cassette and wound around the cylinder, or the speed of the reel chassis on which the reel stand is moved back and forth with respect to the main chassis on which the cylinder is mounted The present invention relates to a drive control device for various motors to which no phase servo is applied.

[0002]

2. Description of the Related Art Conventionally, for driving control of a loading motor of a camera-integrated VTR, a driver to which a power supply voltage is applied winds a tape around a cylinder, that is, the motor is normally rotated in a so-called tape loading direction. Conversely, by supplying a drive direction command from the microcomputer that determines whether the tape wound on the cylinder is to be reversed in the tape unloading direction to be stored in the cassette, the driver will move in the direction corresponding to the drive direction command. The motor is driven, and the power supply voltage supplied from the battery is used as the drive voltage at this time.

FIG. 2 concretely shows a circuit block diagram of this conventional motor control device. In FIG.
The driver-1 has a power supply terminal 2 to which a power supply voltage is applied, a LOAD input terminal 4 for receiving a loading signal from the microcomputer 3 for instructing driving in the loading direction, and an unloading terminal.
A UNLOAD input terminal 5 is provided for receiving an unloading signal for instructing driving in the reading direction.

On the other hand, the microcomputer 3 is provided with LOAD or UNLOAD output terminals 6 and 7 for issuing a loading or unloading signal according to the mode selection operation of the operator. With such a configuration, FIG.
When a loading signal for maintaining the H level during the time period in which the motor 8 is to be normally rotated is supplied from the microcomputer 3 to the driver 1 as shown in (a), the driver 1 uses the voltage applied to the power supply terminal 2 as a drive voltage. To drive the motor 8 in the tape loading direction.

Similarly, as shown in FIG. 3B, when the unloading signal for maintaining the H level is supplied from the microcomputer 3 to the driver 1 during the period in which the motor 8 is to be rotated in the reverse direction, the driver 1 is applied to the power supply terminal 2. The drive voltage is used as the drive voltage to drive the motor 8 in the tape unloading direction.

[0006]

In the above-mentioned prior art, the power supply voltage is supplied from the battery. However, the power supply voltage from the battery may vary depending on the battery itself or other reasons. In particular, 5V from the battery is applied to the motor to which 5V is applied as the power supply voltage.
When a higher voltage is applied, the motor rotates at a speed higher than the optimum rotation speed, resulting in unstable tape loading or tape unloading operation.

Therefore, as a countermeasure against this, usually, a power supply stabilizing circuit 12 including a comparator 9 and control transistors 10 and 11 is arranged between the power supply terminal 2 and the power supply line of the battery so that the power supply is stabilized in advance to a certain level. The set reference voltage is created by the microcomputer 3, and this is set by the comparator 9
The voltage applied to one of the input terminals is compared with the value obtained by dividing the voltage applied to the power supply terminal 2, and the control transistors 10 and 11 are controlled by this comparison output to change the voltage of the power supply line of the battery. Even if the above occurs, it is essential that the voltage applied to the power supply terminal 2 be constantly maintained at a preset level.

As described above, the conventional technique has a problem that the power source stabilizing circuit dedicated to the driver is indispensable for stabilizing the driving voltage of the motor, and the circuit configuration becomes complicated.

[0009]

SUMMARY OF THE INVENTION The present invention monitors a power supply voltage level and, when the power supply voltage level exceeds a reference level, reduces the duty of a PWM output to be output as the power supply voltage level increases. Then, the motor is driven by applying the power supply voltage in synchronization with the PWM output.

[0010]

Since the present invention is configured as described above, the motor can always be stably driven even if the circuit configuration is simplified.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the apparatus of this embodiment.
In FIG. 1, the same parts as those in FIG. 2 of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, a driver-1 has a power supply terminal 2 connected to a power supply line of a battery, and a microcomputer 23.
LOAD input terminal 4 for receiving the loading signal from the unit and UNLOAD input terminal 5 for receiving the unloading signal
Is provided.

On the other hand, the microcomputer 23 is provided with a LOAD output terminal 26 for outputting a loading signal and a UNLOAD output terminal 27 for outputting an unloading signal, and the operator operates an operation button (not shown) to load the tape. When the desired mode is desired, the loading signal is output, and conversely, when the tape unloading is desired, the unloading signal is output. Further, the voltage of the power supply terminal 2 is applied to the voltage monitoring input terminal 30 of the microcomputer 23, and the level of the power supply voltage is monitored here.

Next, the operation of the above-mentioned motor control circuit will be described with reference to FIG.
This will be described with reference to the flowchart of First, the microcomputer 2
3, the power supply voltage level L applied to the voltage monitoring input terminal 30 is detected (step 50), the ratio (R / L) between this power supply voltage level L and the reference level R is calculated, and the duty is set to this ratio. Multiply by 100% which is the initial value of
Determine tee D. That is, the duty D of the PWM output is determined by the calculation formula of D = (R / L) × 100% (step 51).

In the above formula, the reference level R means the level at which the power supply voltage becomes the optimum drive voltage for the motor 8, and the duty D is determined so as to be inversely proportional to the power supply voltage level L. It is shown that. For example,
If the power supply voltage level L becomes larger than the reference level R, the duty D becomes inversely proportional to this and becomes smaller than 100% (initial value).

More specifically, the power supply voltage level L is 5.5% higher than the reference level R of 5 V, which is 5.5.
When it becomes V, the duty D becomes 90%, which is 10% less than the initial value. Further, when the power supply voltage level is stable at 5 V, the duty maintains the initial value of 100%. Thus, when the duty is determined, the PLAY, Whether the REC mode is selected, or the mode in which the tape loading is required subsequent to the cassette loading operation is automatically selected, and the VTR is in the operation mode requiring the tape loading,
On the contrary, it is judged whether the eject mode is selected and the VTR is in the operation mode requiring the tape unloading (step 52). When it is judged that the tape loading is necessary, (c) of FIG. ) Like LOA
The PWM signal whose duty is determined as described above is output from the D output terminal 26 as a loading signal (step 53).

On the contrary, when it is determined that the mode requires unloading, UNLOAD is performed as shown in FIG.
The PWM signal whose duty is determined as described above is output from the output terminal 27 as an unloading signal (step 55).

As for the PWM signal, a completion detection signal obtained by mechanically detecting completion of tape loading or unloading by a limit switch arranged in the tape loading mechanism is input to the microcomputer 23. Will continue until

In this way, when the PWM loading signal is input to the LOAD input terminal 4, the driver 1 uses the power supply voltage as the drive voltage of the motor 8 and uses the power supply voltage as the drive voltage only during the H level period of the PWM. 8 and the motor 8 rotates in the loading direction based on this (step 54).

Similarly, PW is connected to the UNLOAD input terminal 25.
When the M unloading signal is input, the driver 1 sets the power supply voltage to the drive voltage of the motor 8 and
The power supply voltage is applied as a drive voltage to the motor 8 only during the period of M H level, and the motor 8 rotates in the unloading direction (step 56).

Here, since the PWM is duty-corrected according to the power source voltage level as described above, when the power source voltage is higher than the reference level R by 10%, the PWM is performed.
By reducing the duty of 10%, the application time of the power supply voltage to the motor 8 is also reduced by 10%, and substantially the same power supply as when the reference level R is applied at a duty of 90% is supplied. Has been made to the motor.

Although it has been described that the PWM duty is determined by the microcomputer 23 so as to be inversely proportional to the power supply voltage, such measures are taken only when the power supply voltage level exceeds the reference level. When the power supply voltage level falls below the reference level, the microcomputer 23 prohibits the generation of both loading and unloading signals as an abnormal condition.

In the above embodiment, the tape loading motor for operating the tape loading mechanism has been described as an object, but the invention is not particularly limited to this, and any motor can be used so long as no speed or phase servo is applied. For example, it may be a motor for loading the cassette of the VTR.

Further, the control operation of the microcomputer 23 of FIG.
It goes without saying that it can be realized by hardware.

[0025]

As described above, according to the present invention, it is possible to realize stable rotation of the motor even if the power source voltage fluctuates without providing a power source stabilizing circuit for the power source voltage of the driver.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of a conventional example.

FIG. 3 is a waveform diagram of loading and unloading signals according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation of the microcomputer according to the exemplary embodiment of the present invention.

[Explanation of symbols]

 8 Tape loading motor 23 Microcomputer 21 Driver-

Claims (1)

[Claims] 1. A control means for monitoring a power supply voltage level and, when the power supply voltage level exceeds a reference level, reducing the duty of a PWM output to be output as the power supply voltage level increases. A motor control device comprising a driver that drives the motor by applying the power supply voltage in synchronization with the PWM output from the control means.