JPS6329360A - Servo circuit - Google Patents

Abstract

PURPOSE:To attain the drive at a prescribed drive speed by adding the 1st voltage corresponding to the difference between number of revolutions of a body to be driven and a setting number of revolutions and the 2nd voltage corresponding to the accumulated value over the setting period of the difference at a setting ratio and applying the 3rd voltage to the drive motor. CONSTITUTION:A count X is subtracted from a count of a counter 3 read in a subtractor 4, the result is latched by a latch circuit 5, converted into an analog signal by a D/A converter 6, added to a voltage of a voltage source 7 by an adder 11 to drive a motor 13 via a drive circuit 12. An output of the subtractor 4 corresponds to the deviation between an present number of revolutions and an object number of revolutions of a turntable 1 and the motor 13 is driven by a voltage corresponding to the sum of the deviation and the object number of revolutions given as a voltage Z. As a result, the turntable 1 reaches rapidly the object number of revolutions at start with the sum between the voltage Z and the voltage corresponding to the deviation and after the object number of revolutions is reached, the voltage Z is increased/ decreased by the voltage corresponding to the deviation to control the number of revolutions of the turntable to the object number of revolutions. Thus, the number of revolutions of the body to be driven is kept within the setting range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a record player, a rotating body of a digital audio disc, and a servo circuit for driving the rotating body.

(Background of the invention) Conventionally, P has been used to drive the turntable of record players.
Using LL circuit? A circuit is used to constantly apply large feedback to stabilize the turntable rotation speed.

However, if there is a large speed change such as during startup, a large overshoot will occur when returning to the steady rotation speed, so even if the drive is at a steady rotation speed, small speed changes may occur. It was making N etc. worse.

In order to improve all of these, it is necessary to increase the inertia of the turntable and increase the total torque of the drive motor.
Even so, there was a problem that overshoot occurred.

(Objective of the Invention) In view of the above, the present invention provides a system for driving a rotating body at a constant rotational speed without causing overshoot due to large disturbances or deteriorating the S/Nt as in the case of using all conventional PLL circuits. The purpose is to provide circuits.

(Means for solving the problems) Does the present invention have the above problems? In order to solve the problem, I configured it as follows.

As soon as the first voltage corresponds to the difference between the rotational speed of the driven body and the set rotational speed, the first voltage and the second voltage corresponding to the value obtained by accumulating the difference over the set period are added at a set ratio. 3 voltage is applied to the driven object drive motor.

(Function) In the present invention configured as described above, the first voltage corresponding to the difference between the rotational speed of the driven body and the set rotational speed and the difference are accumulated for each set period, and the second voltage corresponding to the t value is accumulated. As soon as the voltages 3 and 3 are added at a set ratio, the et pressure is applied to the driven body drive motor in relation to the voltage 3, and the driven body drive motor is driven.

Therefore, by setting the setting period and the setting ratio it-, it is possible to maintain the rotational speed of the driven body within the set range, and it is also possible to lengthen the rotational speed fluctuation period of the driven body. .

(Example of the invention) The present invention will be explained below with reference to Examples.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

The present invention is applied to a turntable for a record player.

The rotation of the turntable 1 is detected by an encoder 2, and counted by a counter section 3, which will be described later.

As shown in FIG. 2, the counter section 3 supplies the output signal h f of the encoder 2 to a D flip-flop 31 which divides the frequency by 2, and the output of the D flip-flop 31 is divided by 2 and the output signal h f is divided by 2.
During the high potential period of the Q output of the D flip-flop 31, the ANDf-) 32 is controlled to be in the open state. The oscillation output of a reference clock signal generator 33 is supplied to the AND-DATE 32, and is supplied to a counter 34 for counting while the AND-DATE 32 is in the open state. On the other hand, when the Q output of the D flip-flop 31 becomes a low potential, the count value of the counter 34 is supplied to a subtracter 4, which will be described later, at its falling edge. Furthermore, the Q output of the D flip-flop 31 and the counter 3
The read end signal for the count value of 4 is supplied to the reset signal generation circuit 35, and the Q output of the D flip-flop 31 becomes a low potential and the read end signal for the count value of the counter 34 is input, so that the reset signal is generated. is generated,
The counter 34 is reset and ready for the next count.

The count value f17 is counted by the counter section 3. The count value is obtained by subtracting the count value X corresponding to the target rotation speed of the turntable by a subtracter 4, and the output of the subtracter 4 is latched by a latch circuit 5. The latch output is converted into an analog signal by the D/A converter 6. At the same time, the output of the subtracter 4 is supplied to an accumulator 8 for accumulation, the accumulation result is supplied to a latch circuit 9 and latched, and the latch output of the latch circuit 9 is sent to a D/A converter 10 as an analog signal. Convert to On the other hand, the fc voltage Z of the constant voltage source 7 corresponding to the target rotation speed of the turntable, the output analog magnetic pressure of the D/A converter 6 and the output analog voltage of the D/A converter 10 are supplied to the adder 11. Add, adder 1
The add output of 1 drives the turntable drive motor 13 via the drive circuit 12.

The output of the subtractor 4 is supplied to deinotal comparators (hereinafter simply referred to as comparators) 14 and 15, and the comparator 14 compares the low limit value LL with the output of the subtractor 4.
The upper limit value UL and the output of the subtracter 4 are compared at The output of the comparator 15 is OR f-
) 16 to reset the accumulator 8 by the output of the OR gate 16.

In the present invention configured as described above, upon application of the power supply voltage, the turntable 1 starts to be rotated by the drive circuit 12 that receives the voltage from the power supply 7.

As the turntable 1 rotates, the output & of the encoder 2 becomes as shown in FIG. 3(a). Encoder 2 output a
The duty ratio of D flip-flop 3 is not accurate.
The frequency is divided by 2 by 1. D flip-flop 31 of 4
The output is as shown in FIG. 3(b), and the Q output of the D flip-flop 31 is as shown in FIG. 3 (cl), and this period is accurate regardless of variations in the duty ratio.

Therefore, the variation in the duty ratio is eliminated.

During the period when the Q output of the D flip-flop 31 is at a high potential, the oscillation output of the reference clock signal oscillator 33 is
Output from 2. Therefore, the output from the AND gate 32 is counted by a counter 34 as shown in FIG. 3(d). As a result, when the rotation speed of the turntable 1 is small, the D flip-flop 3 shown in FIG.
The period in which the Q output of 1 is at a high potential is long, and the count value of the counter 34 becomes large. Conversely, when the rotation speed of the turntable 1 is high, the period during which the Q output of the D free lag flop 31 shown in FIG.
The count value of 4 becomes smaller. D flip prop 31 Q
When the output becomes a low potential, the count value of the counter 34 is changed to the subtracter 4.
When the reading is completed and a reading end signal is supplied, the count value of the counter 34 is reset.

The count value X is subtracted from the count value of the counter 34 read into the subtracter 4, and latched by the latch circuit 5.
The converter 6 converts the signal n into an analog signal, which is added to the voltage of the voltage source 7 by an adder 11, and then the motor 13 is driven via the drive circuit 12. However, the output value of the subtractor 4 corresponds to the deviation between the target rotation speed and the current rotation speed of the turntable 1, and is a voltage corresponding to the sum of the target rotation speed given by voltage 2 and the deviation. The motor 13 will be driven.

Note that the above deviation may be multiplied by a coefficient by adjusting the gain of the D/A converter 6, or the coefficient may be multiplied by adding the coefficient using the adder 11.

As a result, the turntable 1 quickly reaches the target rotation speed at startup due to the sum of voltage 2 and the voltage corresponding to the deviation, and after reaching the target rotation speed, voltage 2 becomes equal to the deviation. The rotational speed of the turntable is controlled to the target rotational speed by increasing or decreasing the rotational speed according to the corresponding voltage.

Furthermore, the deviation is accumulated by an accumulator 8. On the other hand, the deviation, that is, the output of the subtracter 4, is compared with the low limit LL and the low limit UL in comparators 14 and 15, respectively.

Therefore, the rotation speed of the turntable 1 is as shown in FIG. 4(a).
As shown in , when the rotation speed is below the low limit value LL and above the upper limit (i[UL), the accumulated value of the accumulator 8 is latched by the latch circuit 9, and the D/A A converter 10 converts the voltage into an analog direct voltage, an adder 11 adds the voltage 2 to the voltage corresponding to the deviation, and this voltage is applied to a drive circuit 12 .

Now let's set the limit iUL and low limit value LL
This is because when the number of rotations of the turntable 1 decreases, the count value of the counter section 3 increases, and when the number of rotations increases, the count value decreases.

On the other hand, the output of the subtractor 4 is Atsuno J - IJ Mitsuto value U
If it is less than L or if it exceeds the low limit value LLi, the accumulator 8 ViIJ is set and the output from the 6% D/A converter 10 is zero and does not affect the drive of the motor 13.

However, while the latch circuit 5 reads the subtracted value by the subtracter 4 in synchronization with the falling edge of FIG. It will be held in

Here n is a natural number.

Therefore, the value latched by the latch circuit 5, that is, the output value of the subtracter 4, is set to α1 every time the subtracter 4 reads the value. α8
．． α1. α4. If α, . . . (n=4,
As shown in the table above, the latch output of the latch circuit 9 is α1°α1
．． α1. α8, (α, +α2+α, +α4), (α1+
α, +α, +α4)... When the output of the subtracter 4 is higher than the upper limit tUL and lower than the low limit value LL, the accumulator 8 outputs the latch output 'i shown in the table above. That will happen. As a result, the sum of the voltage Z and the converted voltages of the D/A converters 6 and 10 is applied to the drive circuit 12, and the motor 13 is driven. Therefore, by setting the value n and setting the gains of the D/A converters 6 and 9, the fluctuation in the rotational speed of the turntable 1 can be adjusted to the low limit value LL and the upper limit value UL, as shown in FIG. 4(i). It is possible to maintain the fluctuation period between
S/N can be improved. Incidentally, FIG. 4(b) illustrates the variation in the rotational speed of the turntable 1 when a PLL circuit is used.

(Effects of the Invention) As explained above, according to the present invention, a voltage of 1 is applied as soon as the difference between the rotational speed of the driven body and the set rotational speed is applied, and the difference is accumulated over the set period. The second voltage corresponding to the set value is added at a set ratio, and the third voltage resulting from this addition is applied to the driven object drive motor. This makes it possible to maintain the rotational speed of the driven body within a set range, lengthen the rotational speed fluctuation period of the driven body, and achieve reproduction with a good S/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. FIG. 2 is a block diagram showing an example of a counter section in an embodiment of the present invention. FIGS. 3 and 4 are waveform diagrams and rotation speed characteristic diagrams for explaining the operation of an embodiment of the present invention. 1... Turntable, 2... Encoder, 3...
- Counter section, 4... Subtractor, 5 and 9... Latch circuit, 6 and 10... D/A converter, 8... Accumulator, 11... Adder, 12...・Drive circuit, 13・
...Motor, 14 and 15...Comparator.

Claims (1)

[Claims] A first voltage corresponding to the difference between the rotational speed of the driven body and the set rotational speed and a second voltage corresponding to the value obtained by accumulating the difference over a set period are added at a set ratio, and this addition is performed. A servo circuit characterized in that a third voltage according to the invention is applied to a driven object drive motor.