JPH06141582A - Pwm control circuit and servo system equipped with pwm control circuit - Google Patents

Abstract

PURPOSE:To allow fine speed control at the time of startup of a motor by providing a PWM circuit generating PWM pulses having a duty corresponding to the output from a PWM data selecting means. CONSTITUTION:A section for raising the speed of a capstan motor 1 to a reference level comprises a timing level controller 12, a level selector 13, a register group 14, and a data setting circuit 15, wherein the timing level controller 12 switches a switching circuit 7 forcibly to S side at a predetermined timing. On the other hand, outputs from the register group 14 are fed selectively to S side of the switching circuit 7 by switching the level selector 13 sequentially. The register group store PWM data D1-Dn for controlling the speed of the capstan motor 1 finely and the PWM data D1-Dn are set by the data setting circuit 15. Since a driving voltage of (n) levels is fed at the time of rising of the capstan motor 1, rotational speed reaches quickly to a reference level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PWM control circuit, and more particularly to a PWM control circuit suitable for speed control of a VTR capstan motor or drum motor.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing the structure of a conventional capstan servo system, which is composed of a part for controlling the capstan motor to a reference speed in a steady state and a part for raising the capstan motor to the reference speed. ing. First, the part that controls the capstan motor to the reference speed in the steady state will be described. Capstan motor 1
The rotation speed of is detected by the frequency generator (FG) 2,
It is input to the speed detection circuit 3. The speed detection circuit 3 detects the rotation speed of the capstan motor 1 by measuring the output pulse interval of the frequency generator 2. The output of the speed detection circuit 3 is supplied to the reference speed signal (SPEED) in the subtractor 4.
-REF) and the error signal is input to the arithmetic circuit 5. The arithmetic circuit 5 calculates PWM data for controlling the capstan motor 1 to the reference speed based on the error signal, and sets it in the register 6. The PWM data set in the register 6 is input to the PWM circuit 8 through the switching circuit 7 set to the N side in the steady state.
A PWM pulse having a duty corresponding to the PWM data input to the PWM circuit 8 is generated. The PWM pulse is supplied to the capstan motor 1 via the low pass filter 9 and the driver 10. Here, the speed detection circuit 3, the subtractor 4, and the arithmetic circuit 5 are configured by software of a microcomputer (not shown). With the above configuration, the capstan motor 1 can be controlled to the reference speed in the steady state.

Next, a portion for raising the capstan motor to the reference speed will be described. For example, when performing intermittent slow playback with a slow ratio of about 1/2 by repeating still playback of approximately 2 fields and normal playback of approximately 2 fields, an operation of raising the capstan motor to the reference speed is performed every approximately 2 fields. . In order to perform this operation, a timing controller 11 composed of hard logic
Switches the switching circuit 7 to the S side forcibly every two fields, and fixedly inputs high-level (hereinafter, referred to as “H” level) PWM data to the S side of the switching circuit 7. Therefore, the capstan motor 1
Is supplied with a PWM pulse of a duty corresponding to the PWM data of "H" level about every two fields.

FIG. 4 is a timing chart showing this operation, where (a) shows the drive voltage supplied to the capstan motor 1 and (b) shows the rotation speed of the capstan motor 1. The switching circuit 7 is switched to the S side at t = t1,
The capstan motor 1 is supplied with a drive voltage corresponding to the PWM data of the “H” level, the switching circuit 7 is switched to the N side at t = t2, and the capstan motor 1 corresponds to the PWM data set in the register 7. Supply the driving voltage. That is, the starting operation is from t = t1 to t = t2, and the steady operation is from t = t2.

Here, the reason why the hard logic is used at the time of starting is that it is difficult to start at an accurate timing when controlled by software.

[0006]

However, in the conventional capstan servo device, the "H" is generated at the time of start-up.
Since the PWM data of the level is fixedly input to the PWM circuit, fine speed control cannot be performed when the capstan motor is started up, and the rotation speed of the capstan motor as shown in FIG. Had a problem such as a large overshoot.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a PWM control circuit capable of fine speed control at the time of starting a motor and a servo device including the PWM control circuit.

[0008]

In order to solve the above-mentioned problems, the present invention provides a PWM control circuit for storing a plurality of PWM data, and a PWM data storage means for storing the PWM data.
PWM data setting means for setting WM data, PWM data selecting means for switching and outputting the plurality of PWM data at a predetermined timing, and PWM for generating a PWM pulse having a duty corresponding to the output of the PWM data selecting means. It is equipped with a circuit.

Further, according to the present invention, the PWM data corresponding to the error between the rotation speed of the motor and the reference speed is input to the PWM circuit, and the PWM circuit generates a PWM pulse having a duty corresponding to the PWM data to drive the motor. In the servo device, the P that stores a plurality of PWM data
WM data storage means and P in this PWM data storage means
A PWM data setting means for setting WM data and a PWM data selecting means for switching and outputting a plurality of PWM data at a predetermined timing are provided, and the output of the PWM data selecting means is provided to the PWM circuit at the time of starting the motor. It is configured to input.

[0010]

According to the present invention, since the PWM control circuit is constructed as described above, the PWM data selecting means allows the PWM
A plurality of PWM data stored in the data storage means can be switched at a predetermined timing and supplied to the PWM circuit. Therefore, for example, a multi-step PWM pulse can be generated within one field of the video signal.

Further, according to the present invention, since the servo device is configured as described above, a plurality of PWMs switched at a predetermined timing when the motor is started up.
The motor can be driven by the PWM pulse having the duty corresponding to the data. Therefore, for example, since it is possible to supply a multi-step drive voltage to the motor within one field of the video signal, fine speed control becomes possible.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a capstan servo device according to an embodiment of the present invention.
Here, parts corresponding to those in FIG. 3 are assigned the same numbers. Like the conventional example, this embodiment also includes a portion for controlling the capstan motor to the reference speed in the steady state and a portion for raising the capstan motor to the reference speed.However, in the steady state, the capstan motor is set to the reference speed. Since the configuration of the control part is the same as the conventional one, the description of this part is omitted.

In this embodiment, the portion for raising the capstan motor 1 to the reference speed is composed of a timing / level controller 12, a level selector 13, a register group 14 and a data setting circuit 15. The timing / level controller 12 forcibly switches the switching circuit 7 to the S side and switches the level selector 13 sequentially at a predetermined timing. The level selector 13 is switched under the control of the timing / level controller 12, and selectively outputs the output of the register group 14 to the S side of the switching circuit 7. A register group composed of n registers stores PWM data D1 to Dn for finely controlling the speed of the capstan motor 1. The PWM data setting circuit 15 is composed of software of a microcomputer (not shown) and sets the PWM data D1 to Dn.

2A and 2B are operation timing charts of the capstan servo system according to the embodiment of the present invention. FIG. 2A is a drive voltage supplied to the capstan motor 1, and FIG. 2B is a rotation speed of the capstan motor 1. Show. The operation of this embodiment will be described below with reference to FIGS. The timing / level controller 12 operates from t = t3 to t =
Until t4, the switching circuit 7 is forcibly switched to the S side. Further, the level selector 13 is switched between t = t3 and t = t4 to sequentially output the PWM data D1 to Dn of the register group 14 to the S side of the switching circuit 7. As a result, when the capstan motor 1 rises, as shown in FIG.
= 5), the rotation speed of the capstan motor 1 quickly reaches the reference speed as shown in FIG. 2 (b).

Here, the timing level controller 1
2 is a timing t at which the switching circuit 7 switches to the S side.
The timing of switching between 3 to t4 and the level selector 12 is set by writing in a table in the timing / level controller 12. In addition, PWM data D1
Dn is set by the microcomputer (not shown) as described above. The setting process of the PWM data D1 to Dn will be exemplified below.

(1) The PWM data D1 to Dn are set for each rising operation of the capstan motor 1. (2) PWM data D1 to Dn are set according to the load of the capstan motor 1. As a method of measuring the load, for example, the tape position is calculated from the number of rotations of the supply reel and the number of rotations of the take-up reel. Since the load is small, the drive voltage is relatively low, or the temperature is measured by a temperature sensor.When the temperature is low, the load is large, so the drive voltage is relatively large. To be relatively small. (3) PWM data D1 ~ based on the past tape stop position
Set Dn. That is, the tape stop position during intermittent slow playback is measured, and the current PWM data D1 to Dn are set according to the deviation from the track. (4) Settings are made according to the VTR operation mode (slow, FF, etc.).

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention. For example, the above embodiment relates to speed control of the capstan motor during intermittent slow reproduction, but the present invention can also be applied to speed control of the drum motor during intermittent slow reproduction. Also, not only speed control during intermittent slow playback, but also speed control of the capstan motor when moving from pause mode to recording mode, speed control of the capstan motor and drum motor when moving from stop mode to playback mode, It can also be applied to speed control of the reel motor in the FF mode and the rewind mode.

Further, in the above embodiment, the switching of the switching circuit and the level selector is controlled by the timing / level controller, but the control data written in the table of the timing / level controller is sent to the microcomputer, and the control data sent is sent. Alternatively, the level selector and the output selector may be switched by hardware.

[0019]

As described above in detail, the present invention has the following effects. (1) It is possible to generate multi-stage PWM pulses within a predetermined period. (2) Since a multi-step drive voltage can be supplied when starting the motor, the motor can be started smoothly. For example, when applied to the speed control of a capstan motor of a VTR, it is possible to supply a multi-step drive voltage within a rise time within one field. (3) A smooth and optimum startup can be performed by supplying a drive voltage of a level according to the load of the motor and past data.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a capstan servo device according to an embodiment of the present invention.

FIG. 2 is an operation timing chart of the capstan servo device according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional capstan servo device.

FIG. 4 is an operation timing chart of a conventional capstan servo device.

[Explanation of symbols]

 1 Capstan motor 8 PWM circuit 12 Timing level controller 13 Level selector 14 Register group 15 Data setting circuit

Claims (2)

[Claims] 1. (a) P for storing a plurality of PWM data
WM data storage means, (b) PWM data setting means for setting PWM data in the storage means, (c) PWM data selection means for switching and outputting the plurality of PWM data at a predetermined timing, d) A PWM control circuit comprising a PWM circuit for generating a PWM pulse having a duty corresponding to the output of the PWM data selection means. 2. A PWM circuit inputs PWM data corresponding to an error between a motor rotation speed and a reference speed, and the PWM circuit generates a PWM pulse having a duty corresponding to the PWM data to drive the motor. In the servo device, (a) PWM data storage means for storing a plurality of PWM data, (b) PWM data setting means for setting PWM data in the storage means, and (c) a plurality of the PWM data PWM data selecting means for switching and outputting at a predetermined timing is provided, and the PWM circuit selects the PW when the motor starts up.
A servo device characterized in that the output of the M data selecting means is inputted.