JPH04124899U - motor control circuit - Google Patents

Abstract

(57) [Summary] [Purpose] In an open-loop voltage-controlled motor drive circuit, by slowing down the startup of the motor during high-speed tape feeding, it is less affected by load fluctuations and tape damage is reduced. Reduce. [Configuration] In order to realize smooth motor startup while absorbing load variations when starting the motor, by monitoring the rotational frequency F of the motor, the rate of change K of the control voltage V at motor startup can be adjusted to Switch depending on the motor rotation speed. Specifically, when the rotation speed of the motor is low, the rate of change of the control voltage is increased, and when the rotation speed of the motor exceeds a predetermined value, the change rate is lowered.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention is a magnetic recording/reproducing device such as a video tape recorder (hereinafter referred to as VTR). High-speed tape feeding when the capstan motor is used for reel drive This invention relates to a motor starting control circuit.

0002

[Conventional technology]

So-called tape fast forwarding (referred to as FFWD) or tape rewinding (referred to as REW) When running the tape at high speed, if the motor is suddenly started, abnormal tension may occur on the tape. There is a concern that this may damage the tape. in tape high speed feed mode The feedback loop method, so-called closed loop method, is used to control the motor when starting the motor. There are two types: loop control method and open loop control method.

0003 In the case of a closed-loop control method, it is not affected by variations in the motor or tape, and is always safe. It has the advantage of providing a certain motor start-up characteristic, but on the other hand, The feedback loop method has a complicated circuit configuration, and is difficult to use with microcomputer servo ICs, etc. The disadvantage is that the hardware costs are high. Therefore, the model When controlling the motor speed by continuously varying it when starting the motor, it is easy to control. This is generally done in an open loop manner. Specifically, the motor control voltage is This is done by changing it at a constant rate of change.

0004

[Problem that the idea aims to solve]

As mentioned above, when starting the motor, the motor control voltage is continuously changed at a constant rate. The open-loop control method that allows The actual speed response of the motor may vary due to variations in the load on the motor due to position, etc. will vary. In particular, the load varies greatly depending on the tape winding position. The response speed of the motor changes greatly between the beginning and end of tape winding. cormorant.

[0005] Figure 4(a) shows the case with a small load, and Figure 4(b) shows the case with a large load. Changes in motor control voltage versus time and motor speed versus time are shown, respectively. It is something. Even if the control voltage is changed in the same way, there will be cases where the load is small and cases where the load is large. In extreme cases, there is a time lag and variation before the motor starts. I can understand that. The more smoothly you try to control motor speed changes, the more Since the control voltage changes slowly, the motor's response to load variations is less biased. The rattling also gets bigger.

[0006] This invention uses an open-loop control method to suppress load variations as much as possible. This allows the motor to start smoothly.

[0007]

[Means to solve the problem]

In this invention, when starting the motor, the motor smoothens while absorbing load variations. In order to achieve smooth starting, the rate of change of the control voltage at motor starting is It is characterized by switching depending on the rotation speed of the motor by monitoring the number of rotations. shall be. Specifically, when the motor rotation speed is low, the rate of change of the control voltage is increased. However, the rate of change is reduced when the rotational speed of the motor exceeds a predetermined value.

[0008]

[Effect]

Due to the configuration of this invention, it is possible to reduce the load when the motor rotation speed is low and the load is large. The motor starts up in a short time, and when the rotation speed of the motor exceeds the specified value, the motor starts up. The number of revolutions increases slowly and smoothly until it reaches the desired number of revolutions.

[0009]

【Example】

A specific embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a flowchart of the present proposal, FIG. 2 is a circuit block diagram thereof, and FIGS. 3(a) and (b) are diagrams showing changes in motor control voltage versus time and motor rotational speed versus time, respectively. It is. In the figure, 1 is a servo microcomputer, and the servo microcomputer 1 includes: The detection frequency of the rotation frequency (FG) detector 3 of the capstan motor 2 is input, and the corresponding input The control voltage for driving the motor 2 at the power frequency is varied, and the next stage PWM (Pu lse Wide Modulation) Supply control voltage to circuit 4. The control voltage is After being shaped into a predetermined voltage waveform in circuit 4, it is amplified in motor drive circuit 5, and the voltage waveform is The motor 2 is driven to rotate.

As shown in the flowchart of FIG. 1 and FIG. 3, the motor drive circuit of the present invention operates such that when the FFWD or REW button (not shown) is operated, the motor starts starting (step 6) at the same time. The control voltage V of the motor increases at a constant rate of change _K1 . That is, V = K ₁ (t-t ₀ ) (step 7). At this time, when the rotational speed of the motor increases and its frequency F exceeds F ₀ (step 8), the control voltage becomes V=V ₁ (step 9). If F<F ₀ , return to step 7 again.

When the control voltage V becomes V ₁ in step 9, the voltage change rate K changes from K ₁ to K ₂ , and the control voltage V becomes V=V ₁ +K ₂ (t−t ₁ ), and its rate of increase is Slow down (step 10). When the rotational speed of the motor increases further and its frequency exceeds F ₁ (step 11), the motor is then controlled at a constant speed (step 12). If the motor rotation frequency does not reach _F1 , return to step 10 again.

[0012]The changes in the control voltage and motor rotational speed over time described above are as shown in FIGS. 3(a) and 3(b). That is, the motor control circuit of the present invention changes the rate of change K of the motor control voltage V when the rotational speed of the motor 2 exceeds a predetermined rotational speed _F0 , that is, changes the initial rate of change _K1 to an intermediate change. Keep the rate sufficiently larger than _K2 . By increasing K ₁ , it is possible to absorb fluctuations at the start of startup, where the startup of the motor 2 is most likely to vary, and by decreasing K ₂ , smooth startup can be achieved.

[0013]

[Effect of the idea]

This invention makes it less susceptible to load variations due to tape position, and Since the rotation speed of the motor can be increased smoothly, tape damage will occur. It is possible to realize smooth motor start-up without any trouble.

[Brief explanation of drawings]

FIG. 1 is a flowchart diagram of the present invention.

FIG. 2 is a circuit block diagram of the present invention.

FIG. 3 is a diagram showing changes in control voltage and motor rotation speed with respect to time according to the present invention.

FIG. 4 is a diagram showing changes in motor control voltage and motor speed versus time in a conventional example.

[Explanation of symbols]

1 Servo microcomputer 2 Capstan motor 3 Rotation speed (FG) detector F Motor rotation frequency V Motor control voltage

Claims (1)

[Scope of utility model registration request] 1. In an open-loop voltage-controlled motor drive circuit, when the motor is started in a tape high-speed feeding mode, the number of revolutions of the motor is detected, and the number of revolutions of the motor is detected when the number of revolutions exceeds a predetermined number of revolutions. A motor control circuit characterized by detecting and switching a rate of change of the control voltage.