KR920006087Y1 - Velocity control circuit for reel motor - Google Patents

Abstract

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Description

Speed control circuit of reel motor

1 is a conventional circuit diagram.

2 is a circuit diagram of the present invention.

3 is a counter electromotive voltage characteristic diagram of a motor.

4 is a configuration diagram of the comparison unit in FIG.

* Explanation of symbols for main parts of the drawings

R1-R6: Resistance RM1-RM2: Internal resistance of the motor

1,2: comparison unit 3,4: logarithmic amplifier

5,6: inverting amplifier 7,8: exponential amplifier

9: adder 10: comparator

11: current amplifier 12: selector

M1, M2: motor

The present invention relates to a reel motor control circuit of a tape recorder, and more particularly, to a circuit capable of controlling the speed of a reel motor analogally by detecting a counter electromotive voltage of the motor.

The conventional configuration of controlling the speed of a reel motor in a tape recorder is shown in FIG.

First, in order to detect rotation of the reel motor, the reflection plates 21 and 22 are respectively installed on one side of the reel motors M1 and M2, and the reflection plates 21 and 22 rotate by using the photo couplers 23 and 24. Reflects light and generates an electrical signal due to rotation. The waveform shaping parts 25 and 26 then waveform-shape the outputs of the photocouplers 25 and 26 into digital signals, and the counters 27 and 28 convert the outputs of the waveform shaping parts 25 and 26. Count each with a reference clock.

At this time, the reel motors M1 and M2 are rotated in inverse proportion to the amount of tape wound on the reel, so that the counters 27 and 28 count the number of revolutions according to the amount of tape.

After that, the calculation processing unit 29 generates the drive signals of the motors M1 and M2 by calculating the outputs of the counters 27 and 28. At this time, the driving of the reel motor (M1, M2) should be controlled so that the sum of squares of two cycles (TA ² + TB ² = Constant) is constant. The output of the operation processor 29 is applied to a pulse width modulation generator (PWM) 30 to generate a PWM signal according to the driving of the motor, and the PWM signal is a current through the low pass filter 31 and the current amplifier 32. The signal is converted into a signal and supplied to the drive current of the motors M1 and M2. At this time, the selector 33 selects a take-up reel motor.

However, in the conventional reel motor control method as described above, since the reflection plate must be installed on the reel motor, the selection of the motor is limited, and there is a difficulty in miniaturization. there was.

Accordingly, an object of the present invention is to provide a circuit that can control the speed of the motor as a simple circuit by performing arithmetic operation analogously using the counter electromotive voltage according to the rotation of the motor.

Hereinafter, the present invention will be described in detail with emphasis on the drawings.

2 is a schematic diagram of the present invention, and includes motors M1 and M2, resistors R1 and R3, comparators 1, logarithm amplifiers 3, inverting amplifiers 5, and exponential amplifiers 7, Means for detecting the counter-electromotive voltage according to the rotation of the take-up reel motor M1 and generating a square signal of the take-up reel period according to the number of revolutions, the resistors R4 and R6, the comparator 2, It consists of a logarithmic amplifier (4), an inverting amplifier (6) and an exponential amplifier (8), and detects the counter-electromotive voltage according to the rotation of the supply reel motor (M2) to analogize the square signal of the supply reel period according to the rotation speed And a difference signal by comparing the output signal of the adder 3 with the reference signal to the adder 3 generating the periodic sum of squares signal by adding the period squared signal of the take-up and supply reels. Comparator 10 generated by the amplification, and outputs by amplifying the output of the comparator 10 with a current signal Composed of a selector (12) for connecting an output of the current amplifier 11 to the take-up reel motor (M1) or the supply reel motor (M2) depending on the state of the current amplifier 11, and a mode that.

FIG. 3 is a diagram showing generation of counter voltage according to the rotation of the motors M1 and M2, and shows that the counter voltage of the motor is proportional to the number of revolutions of the motor.

FIG. 4 is a detailed circuit diagram of the comparator 1 and 2 of FIG. 2, which includes a comparator MP for generating a counter voltage according to a difference between a signal input to a reference terminal and a comparison terminal, an X point for generating a counter voltage, and Between diodes D1 and D3 connected in a forward direction, respectively, between the Y point generating the reference voltage and the reference terminal (+) of the comparator CMP, and between the X and Y points and the comparator terminal of the comparator CMP. Regardless of the polarity of the counter electromotive voltage generated by the diodes (D2, D4) connected in the reverse direction, respectively, the signal difference can be generated to the absolute value.

Based on the above configuration, the present invention will be described in detail with reference to FIGS. 2, 3, and 4.

First, the motors M1 and M2 are driven by the current generated in the current amplifier 11 according to the connection state of the selector (multiplexerr) 12.

At this time, the selector 12 is connected to the contact A in the FF mode (Fast Forward mode, Play mode, Record mode) to select the take-up reel motor (M1), REW mode (Rewind mode) Is connected to contact B to select supply reel motor (M2).

First, when the resistors R1, R2, and R3 are set so that the resistance becomes R1: R2 = RM1: R3 while the tate-up reel motor M1 is stopped, the potential VX at the X point for detecting the counter electromotive voltage and the reference value are set. The potential VY at the point Y for generating a signal becomes the same. (VX = VY); The supply reel motor M2 also determines the values of the resistors R4, R5, and R6 in the same manner.

Then, when the motor M1 starts to rotate, a counter voltage is generated from the motor M1, and the potential at the X point changes to VA ± VR. VR is the counter voltage.

In this case, since the comparison unit 1 compares the difference between the potential of the X point and the potential of the Y point, the comparator 1 outputs a value corresponding to the counter electromotive voltage Vr.

Accordingly, the comparator 1 uses an absolute comparator as shown in FIG. That is, the take-up reel motor M1 operates when the take-up reel motor M1 is grounded with the counter electromotive voltage in the FF mode and the supply reel motor M2 detects the counter electromotive voltage in the REW mode. In the F and F modes, the supply reel motor M2 is forcibly rotated in the reverse direction of the normal state, so the counter electromotive voltage VR becomes (-).

On the contrary, in REW mode, the counter electromotive voltage becomes negative because the take-up reel motor M1 rotates in the reverse direction.

Accordingly, the output of the comparator 1 and 2 becomes a negative value, and when this is calculated through the logarithm amplifiers 3 and 4, unwanted characteristics are obtained.

In order to improve this, the present invention uses a bridge comparator that outputs the difference of the signal in absolute value regardless of the positive and negative polarity of the input signal. Therefore, if the signal input from the X terminal is larger than the Y terminal, the voltage of the X terminal is applied to the (+) terminal of the comparator (CMP) through the diode (D1), the voltage of the Y terminal is applied to the comparator through the diode (D4) Applied to the negative terminal. In addition, when the signal input from the Y terminal is higher than the X terminal, the voltage of the Y terminal is applied to the (+) terminal of the comparator (CMP) through the diode (D2), the voltage of the X terminal of the comparator through the diode (D3) Applied to the negative terminal.

Therefore, the comparator CMP always outputs an output corresponding to the absolute value of the counter electromotive voltage VR so that the counter electromotive voltage is converted into the number of revolutions regardless of the rotational direction of the motors M1 and M2.

In this case, since the counter electromotive voltage VR outputting the comparator 1 is proportional to the rotation speed NA of the motor M1 as shown in FIG. 3, the output of the comparator 1 can be expressed as the rotation speed NA of the motor M1. In the same way, the output of the comparator 2 can be expressed as the rotation speed NB of the motor M2.

When the linear velocity of the tape is constantly controlled during the high-speed search, the sum of squares of the rotation period TB of the TA of the tape-up reel motor M1 and the rotation period TB of the supply reel motor M2 always occurs at a constant value K. If this is expressed as a formula, it is the same as the following formula (1), and the rotation period T of the reel is inversely proportional to the motor rotational speed N.

Therefore, when the equation (2) is converted back into a logarithm and an exponential function, the equation (2) is changed to the equation (3).

Therefore, when the rotational speeds NA and NB outputted by the comparator 1 and 2 are analogically calculated, the linear velocity of the tape can be controlled constantly.

Therefore, the rotation speed NA of the motor M1 output from the comparator 1 becomes logNA through the logarithm AMP (3), and -2 logNA through the inverting amplifier 5 whose gain is -2 times. When the exponent amplifier 7 is used, it becomes e ^{-2log NA} , which is a square signal of the rotation period of the take-up reel motor M1.

In addition, the rotation speed NB of the motor M2 output from the comparator 2 becomes log NB through the logarithmic amplifier 4, -2 log NB through the inverting amplifier 6, and the exponential amplifier 8 E- ^{2log NB} . At this time, the added value is always a constant value (K) that the motor is normally driven.

However, if the output of the adder 9 is larger or smaller than the predetermined value K, the rotation speed of the motor should be adjusted.

Therefore, the comparator 10 controls the speed of the motor by outputting the output of the adder 9 and the reference signal K as the secondary signal and the current amplifier 11. That is, if the output of the adder 9 is larger than the reference signal K, the motor speed is slow. Therefore, the comparator 10 increases the applied voltage to speed up the driving of the motor, and if the output of the adder 9 is smaller than the reference signal K, Since the speed of the motor is high, the comparator 10 lowers the applied voltage to slow the driving of the motor.

Therefore, the tape recorder can control the line speed of the tape at high speed search such as FF mode and REW mode.

As described above, the tape recorder detects the counter electromotive voltage of the reel motor, detects the rotational speed, and then performs arithmetic processing using a logarithmic and exponential amplifier to maintain a constant linear speed of the tape during high-speed search by controlling the reel motor analogously. There is an advantage to this.

Claims (3)

Take-up and supply reel motors M1 and M2, a selector for selecting the motors M1 and M2 according to the state of the mode, and a current amplifier for outputting the motor drive current to the selector by a predetermined drive power source; 1. A speed control circuit of a reel motor, comprising: first means for detecting a counter voltage according to rotation of the take-up reel motor M1 and generating a square signal of a take-up period according to the rotation speed analogously; Second means for generating a square signal of a supply reel period according to rotational speed by detecting a counter electromotive voltage according to rotation of the reel motor M2, and take-up and supply reel periods of the first and second means; An adder for generating a periodic sum of squares signal by adding a square signal, and a comparator for generating a difference signal as a motor driving power source by comparing the output of the adder 9 with a reference signal. Reel motor speed control circuit. 2. The apparatus according to claim 1, wherein the first and second means respectively detect counterweight voltage directly proportional to the rotation of the motor, a comparator for generating a rotational speed N of the motor according to the counterweight voltage, and the comparator. A logarithmic amplifier for logarithmic output (log N), an inverting amplifier for inverting amplification (-2log N) of the output of the logarithmic amplifier to gain -2, and an exponential amplification (e ^{-2log N} ) for the output of the inverting amplifier. A speed control circuit for a reel motor, characterized in that it consists of an exponential amplifier. 3. The speed control circuit according to claim 2, wherein the comparator comprises a bridge diode and a comparator and operates to generate a motor speed signal that is a difference signal regardless of the polarity of the counter electromotive voltage.