JPH09168289A - Motor speed control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feedback speed control circuit having good response characteristic during the switching of motor operating conditions. SOLUTION: A speed changeover switch 14 is connected to an F-V converter 12 in the output stage of a speed detector 11 formed of FG of a motor 1. An integral circuit 16 is provided in the output stage of the F-V converter 12. A charging circuit 20 is connected to a capacitor 19 of this integral circuit 16. A charging voltage Va of the charging circuit 20 is impressed to a capacitor 19 via a diode 24. The capacitor 19 is previously charged to the predetermined voltage by the charging voltage. Moreover, when a voltage of the integral capacitor 19 becomes lower than the predetermined value at the time of changing over the speed of the motor 1 by the operation of the switch 14, the capacitor 19 is charged via the diode 24, impeding voltage drop of the capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control circuit for a motor for running a recording medium magnetic tape, rotating a recording medium disk, and the like.

[0002]

2. Description of the Related Art A typical feedback speed control circuit for a motor includes a speed detector comprising a frequency generator (FG) for generating a frequency signal corresponding to the speed of the motor, and a voltage signal output from the speed detector. And a reference voltage source for generating a reference voltage corresponding to a desired speed of the motor, and an output corresponding to a difference between a speed detection voltage signal obtained from the frequency-voltage converter and the reference voltage. (For example, a voltage obtained by adding a reference voltage to the difference), and a drive circuit that drives the motor in response to the output of the error amplifier.

[0003]

However, since the integration circuit includes a capacitor, a response delay occurs when the operation state of the motor is switched. For example, when the motor is started, even if a start command is given, the rotation of the motor does not start until the integrating capacitor is charged to a predetermined level or more.
In addition, even when the motor is switched from a high rotation speed to a low rotation speed, the integration capacitor is discharged following the decrease in the voltage level of the control signal, and control for obtaining a desired low rotation speed that occurs thereafter. The motor cannot be driven until the signal charges the integrating capacitor again above a predetermined level.

It is an object of the present invention to provide a feedback speed control circuit with good responsiveness when changing the operating state of a motor.

[0005]

In order to achieve the above object, the present invention provides a frequency signal generator for generating a frequency signal corresponding to the rotation speed of a motor, and an output frequency signal of the frequency signal generator. A voltage signal is converted into a voltage signal, and when the output frequency signal is in a region lower than the first predetermined frequency (F1), a constant high level voltage (VH) is generated, and the output frequency signal is the first frequency signal. Predetermined frequency (F1
) Is higher than a second predetermined frequency (F2) higher than the second predetermined frequency (F2), a constant low level voltage (VL) lower than the high level voltage (VH) is generated, and the output frequency signal is equal to the first frequency. When it is between the predetermined frequency (F1) and the second predetermined frequency (F2), the speed voltage that changes in inverse proportion to the change of the output frequency signal is set to the high level voltage (VH) and the low level voltage. (VL) and a frequency-to-voltage converter configured to generate it and a speed changeover switch for changing over the speed of the motor. In response to the speed changeover switch being operated to switch to a lower rotation speed state, the low level voltage (V
L) is generated from the frequency-voltage converter and the
The frequency-voltage converter includes a speed switching control unit for generating a speed voltage from the frequency-voltage converter that changes in inverse proportion to the output frequency signal when the rotational speed of the rotor is in the speed controllable range; An integrating circuit connected to the frequency-voltage converter so as to integrate the speed voltage obtained from the voltage converter, a reference voltage generating circuit,
A difference signal forming circuit for generating a voltage corresponding to the difference between the integrated output voltage obtained from the integrating circuit and the reference voltage obtained from the reference voltage generating circuit, and responsive to the output of the difference signal forming circuit. The present invention relates to a motor speed control circuit including a motor drive circuit for driving the motor and a charging circuit for preventing the voltage of the capacitor of the integration circuit from falling below a predetermined value. It is preferable that a charging circuit be configured by connecting a voltage source to the capacitor via a diode. As described in claim 3, the integrating circuit can be configured by combining the operational amplifier (opamp) and the capacitor. Further, as described in claim 4, it is possible to provide a circuit for charging a capacitor for integrating a comparison output of the frequency signal corresponding to the rotation speed of the motor and the reference frequency signal.

[0006]

The charging circuit according to the invention of each claim charges the integrating capacitor so as to prevent the voltage of the integrating capacitor from dropping below a predetermined value. Therefore,
The capacitor can be charged to a predetermined voltage even during the motor stop period. When the capacitor is charged to a predetermined level, driving of the motor can be started quickly. Further, even when the motor is switched from high speed to low speed, the voltage of the capacitor does not drop below a predetermined value, so that it is possible to quickly shift to the low speed state.

Next, the integrating circuit will be described. The feedback speed control circuit includes a feedback speed control circuit shown in FIG.
An integrating circuit as shown in is connected in series. This integrator circuit has a first resistor R connected in series to the control signal line.
1 and a capacitor C connected between the output terminal and the ground via a second resistor R2. The frequency characteristic of the integrating circuit configured in this way is as shown in FIG. 12, and there is substantially no attenuation in the frequency region lower than the first angular frequency ω1, and the gain is substantially 0 dB or 1 time. , A second angular frequency ω2 higher than the first angular frequency ω1
The gain is 20 log [R2 / (R1 +
R2)] dB or R2 / (R1 + R2) times. In addition,
The first angular frequency ω1 is determined by 1 / C (R1 + R2) and the second angular frequency ω2 is determined by 1 / CR2.

The integrating circuit having the characteristics shown in FIG. 12 has little attenuation for components that change over time, that is, very low frequency components, that is, DC components or steady components, but high frequency components, such as wow and flutter, that are transient components in a magnetic tape device. Or, it shows a large attenuation for the AC component. Therefore,
The DC component of the feedback control signal, which indicates a long-term change in the load torque of the motor, that is, a long-term deviation from a reference value at the time of manufacturing the load torque, is transmitted without substantially attenuating, is well compensated by the feedback control, and the desired The rotation speed is maintained. The change in the DC component also occurs when a long-term change in the motor itself, that is, when the relationship between the drive voltage of the motor and this output torque changes due to aging or temperature change. As in the case, it is effectively compensated by the feedback control. On the other hand, a high frequency component such as wow and flutter, that is, a transient component or an AC component is suppressed by the integration circuit, so that the gain of the feedback control circuit for the AC component is prevented from becoming excessive, and oscillation is prevented. .

[0009]

First Embodiment Next, a speed or torque control circuit of a capstan motor in a magnetic tape recording / reproducing apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, a motor 1 is a brushless DC motor, which is connected between a DC power source end 2 and a ground via a drive circuit 3. The driving circuit 3 includes an amplifier 4 and a transistor 5 as shown in principle, and a motor 1
The current of the motor 1 is controlled by controlling the transistor 5 connected between the power supply and the ground by the output of the amplifier 4, and the output torque of the motor 1, that is, the rotation speed is controlled. A capstan 9 for driving the magnetic tape 8 at a constant speed between the pair of reels 6 and 7 is coupled to the motor 1 as a load.

In order to feedback control the DC motor 1, a speed voltage generator 10 for generating a speed voltage corresponding to the rotation speed of the motor 1 is provided. The speed voltage generator 10 outputs a known speed detector 11 including a frequency generator or a frequency generator (FG) that generates a frequency signal corresponding to the rotation speed of the motor 1 and an output frequency signal of the speed detector 11. It is composed of a well-known frequency-voltage converter or FV converter 12 for converting into a voltage signal. This F
As shown in FIG. 2, the −V converter 12 uses the first frequency F
A speed voltage that varies inversely with the input frequency is generated between 1 and the second frequency F2, and a constant high level voltage VH is generated in a region lower than the first frequency F1 and the second frequency F2 is generated. It is configured to generate a constant low level voltage VL in a higher region.

The FV converter 12 is connected to a switch 13 for controlling the start and stop of the motor 1 and a speed switching switch 14 for the motor 1. The FV converter 12 first generates a voltage of high level VH in response to the start / stop control switch 13 being turned on, and then outputs a speed voltage indicating the rotation speed when the rotation speed enters a predetermined lock range. . Further, the FV converter 12 has a built-in circuit for switching the level of the output speed voltage, and in response to the turning on of the speed switching switch 14, the speed voltage of the level for bringing the motor 1 to the first rotation speed. And outputs a speed voltage of a level for making the motor 1 a second rotation speed higher than the first rotation speed in response to the speed switch 14 being turned off. However, when switching from high speed to low speed, F-
A low level VL, that is, a voltage of zero volt is generated from the V converter 12, and a speed voltage for low speed is generated when a low speed lock range is reached.

An integration circuit 16 is connected to an output line 15 of the FV converter 12. This integrating circuit 16 is F-
A first terminal connected in series to the output line 15 of the V converter 12
, A second resistor 18 and a capacitor 1 connected between the output terminal of the first resistor 17 and the ground.
9 in series. For example, the value of the first resistor 17 is 10 kΩ, the value of the second resistor 18 is 5.6 kΩ, and the value of the capacitor 19 is 220 μF. This integration circuit 16 is the same as the circuit shown in FIG. 11, and has the frequency characteristics shown in FIG.

A charging circuit 20 for preventing voltage drop according to the present invention is connected to one end of the integrating capacitor 19.
This charging circuit 20 has a charging voltage V of the integrating capacitor 19.
This is a circuit for preventing c from becoming lower than a predetermined value V1, and is a voltage dividing circuit composed of a resistor 22 and a variable resistor 23 connected between the DC power supply terminal 21 and the ground, and this voltage dividing circuit. It is composed of a reverse current blocking diode 24 connected between the voltage dividing point P1 and the one end of the capacitor 19. The voltage Vc of the capacitor 19 is a value obtained by subtracting the forward voltage Vf of the diode 24 from the voltage Va across the resistor 23 (V1 =
When it becomes lower than (Va-Vf), the charging current of the capacitor 19 flows through the diode 24. Therefore, the charging voltage of the capacitor 19 is kept above the predetermined value V1 regardless of the output of the FV converter 12. The predetermined value V1 is set to a value close to the reference voltage Vr of the reference voltage circuit 27.

An output line 25 of the integrating circuit 16 is connected to one input terminal (non-inverting terminal) of an error amplifier 26 composed of an operational amplifier (operational amplifier). Error amplifier 26
Is connected to the reference voltage circuit 27 via a resistor 27a. The reference voltage circuit 27 includes a voltage dividing circuit including two resistors 29 and 30 connected between the DC power supply terminal 28 and the ground, and the voltage dividing point is connected to the other input terminal. A feedback resistor 31 is connected between the output terminal of the error amplifier 26 and the other input terminal. The error amplifier 26 sends a signal corresponding to the difference between the output voltage of the integrating circuit 16 and the reference voltage of the reference voltage circuit 27, that is, a value obtained by adding the reference voltage to the difference to the output terminal.

The output terminal of the error amplifier 26 is connected to a resistor 32,
It is connected to the amplifier 4 of the motor drive circuit 3 via an output level setting circuit 35 including 33 and 34. The resistor 32 is connected in series with the signal output line, the resistor 33 is connected between the output end of the resistor 32 and the power supply terminal 36, and the resistor 34 is connected between the output end of the resistor 32 and the ground. There is.

[0017]

[Operation] When the power switch (not shown) of the magnetic tape recording / reproducing apparatus of FIG. 1 is turned on, the respective power supply terminals 2, 21, 2
A predetermined voltage is supplied to 8 and 36. Assuming that the capacitor 19 is completely discharged, the charging current of the capacitor 19 flows through the diode 24 of the voltage drop prevention circuit 20, and the voltage Vc becomes the predetermined value V1.
After that, when the start / stop switch 13 is turned on, F-
An output voltage is generated from the V converter 12. Since the motor 1 is initially stopped, the output frequency of the speed detector 11 is as shown in FIG.
, Which is a constant high level voltage VH, which becomes the input of the integrating circuit 16. As shown in FIG. 3, the voltage Vc of the integrating capacitor 19 is V1 before the time t1 at which the start / stop switch 13 is turned on to generate the start command. The voltage Vb of the output line 25 of the integrating circuit 16 before this t1 is a value obtained by subtracting the voltage drop due to the resistor 18 from the voltage Vc of the capacitor 19. This t1
Vb before that is lower than the voltage of the non-inverting input terminal of the error amplifier 26 required for starting the motor 1 (hereinafter, referred to as starting voltage Vs). When the start / stop switch 13 is turned on at time t1, the FV converter 12 naturally generates a voltage VH higher than the start voltage Vs. T in FIG.
When VH is generated at 1, this voltage VH is applied to resistors 17 and 18
The voltage that is the sum of the voltage divided by and the capacitor voltage Vc becomes the integrated output voltage Vb. Since the rotation speed of the motor 1 has not risen to the desired value in the period from t1 to t2, the FV converter 12
Is maintained at VH, and a voltage sufficiently higher than the starting voltage Vs becomes the input of the error amplifier 26. In the period from t1 to t2, the error amplifier 26 has a relatively large integrated output voltage Vb.
And a reference voltage Vr, the motor drive circuit 3 responds to this by supplying a sufficiently large current to the motor 1 to accelerate the motor 1. As a result, the rotation speed of the motor 1 rises rapidly as shown in the section from t1 to t2 in FIG. At t2, the rotation speed of the motor 1 is the FV converter 1
When the controllable range (lock range) of No. 2 is entered, a speed voltage Vv having an inversely proportional relationship to the rotation speed (frequency) is generated, and this becomes the input of the integrating circuit 16. F1 to F in FIG.
Since the value of the speed voltage in the lock range of 2 is lower than the voltage in the acceleration region lower than F1, the output voltage Vb of the integrating circuit 16 decreases when the control loop enters the locked state at time t2. On the other hand, the capacitor 19 is charged on the basis of the high voltage VH in the acceleration section from t1 to t2, and this voltage Vc is shown in FIG.
It gradually increases as shown in. When the output voltage of the FV converter 12 drops from VH to the voltage in the lock range at time t2, the capacitor 19 is discharged through the paths of the resistors 18 and 17, the FV converter 12 and the ground, and at the time t3, Vc And V
b matches, and a stable feedback control state is entered. Assuming that the rotation speed of the motor 1 is lower than a desired value in a stable feedback control state, F
A higher speed voltage Vv is generated from the −V converter 12, the output voltage of the integrating circuit 16 and the error amplifier 26 is also higher, and a larger current than that is supplied to the motor 1 via the drive circuit 3. , The rotation speed returns to the desired value. Conversely, when the rotation speed of the motor 1 becomes higher than the desired value, the operation opposite to the above occurs.

As is apparent from FIGS. 3 and 5, the time length of the period t1 to t2 is extremely short in this embodiment. This is because the capacitor 19 is charged to a predetermined value by the charging circuit 20 at the same time when the power is turned on. If Figure 1
If the charging circuit 20 is omitted from the above circuit and the circuit is made the same as the conventional circuit, the operation shown in FIGS. That is, since the capacitor 19 is not charged in advance, the capacitor 19 is charged from zero volt in synchronization with the start command at time t1 as shown in FIG. 4, and the integrated output voltage Vb is also significantly lower than the start voltage Vs. Start increasing from the value. The integrated output voltage Vb reaches the starting voltage Vs at t1 'after t1, the rotation of the motor 1 starts only at this point, and the rotation speed enters the lock range at t2. Therefore, the period (rise time) from the start command time t1 to the time t2 when the motor 1 reaches the desired rotation speed (locked state) becomes long, and the rotation of the motor 1 cannot be started quickly.

According to the circuit of this embodiment, the rotation speed of the motor 1 can be quickly switched. FIG. 7, FIG. 8, FIG. 9, and FIG. 10 are for explaining this. Before the time t1 in FIGS. 7 and 9, the high speed (second speed N2) control state is in response to the turning off of the speed changeover switch 14 in FIG. When the switch 14 is turned on at the time t1 to give a low speed (first speed N1) control command, the desired first speed N1 is reached at the subsequent time t2. According to FIG. 7, this t1 to t
Explaining in detail the operation for two periods, by giving a switching command from high speed to low speed at t1, the FV converter 12 generates the low level VL (zero volt) shown in FIG. 2 for deceleration control. As a result, the integrated output voltage Vb decreases at time t1. Further, the capacitor 19 enters the discharge mode, and the charging voltage Vc also drops. When the voltage Vc of the capacitor 19 becomes lower than the voltage V1 of the charging circuit 20,
Since the diode 24 is turned on and the charging current flows from the charging circuit 20 to the capacitor 19, the drop of the voltage Vc of the capacitor 19 is limited by V1. At time t2, the rotation speed of the motor 1 reaches the desired speed N1, and the desired speed N1
When the lock range (speed controllable range) for obtaining is obtained, a speed voltage higher than the low level VL is generated from the FV converter 12, and the integrated output voltage Vb immediately causes the start voltage Vs.
And the feedback control is started, t3
From the time point, a stable low speed (first speed N1) control state is entered. In this control, as shown in FIG.
The speed N1 is stabilized with almost no overshoot, and the period from the speed switching command time t1 to the time t2 when the speed is stabilized to the first speed N1 is extremely short.

If the charging circuit 20 shown in FIG. 1 is not provided, the operation at the time of speed switching is as shown in FIGS. In this case, a speed switching command is generated at t1 and F-V
When the output of the converter 12 goes to a low level VL (zero volt), the discharge of the capacitor 19 becomes much larger than in the case of FIG. That is, in FIG. 10, the discharge of the capacitor 19 progresses until the time ta when the rotation speed of the motor 1 reaches the first speed N1, and the integrated output voltage Vb also decreases following the capacitor voltage Vc. In the conventional circuit without the charging circuit 20, ta
Therefore, even if the rotation speed of the motor 1 reaches the first rotation speed N1 and once enters the lock range, and the voltage for obtaining the first rotation speed N1 is generated from the FV converter 12, the integrated output voltage Vb Does not reach the starting voltage Vs, the lock is not established. Therefore, the rotation speed of the motor 1 becomes equal to or lower than the first rotation speed N1 as shown in FIG. 10 due to inertia. As a result, after ta, the FV converter 12 produces an output indicated by VH in FIG. 2, charging of the capacitor 19 starts, and the integrated output voltage Vb also rises. When the integrated output voltage Vb crosses the starting voltage Vs at tb, the driving of the motor 1 is started, and at t2, the first rotation speed N1 is reached again and the lock state is established. Therefore, the period from t1 to t2 in FIGS. 8 and 10 is shown in FIGS.
Is longer than the t1 to t2 period.

[0021]

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG.
A feedback control circuit according to the embodiment of the present invention will be described.
However, in FIG. 13 and FIGS. 15, 16 and 17, which will be described later, portions common to FIG. 1 are denoted by the same reference numerals, description thereof will be omitted, and most of the common portions will be omitted. The feedback control circuit of the second embodiment is a modification of the integrating circuit 25 of FIG. The inverting input terminal of the operational amplifier 26a is connected to the FV converter 1 via the first resistor 40.
2a. The non-inverting input terminal of the operational amplifier 26a is connected to the reference voltage circuit 27. A capacitor 19 is connected between the inverting input terminal and the output terminal of the operational amplifier 26a via the second resistor 18, and a feedback resistor 41 is connected. The charging circuit 20a has a power supply terminal 4
2 and a non-polar capacitor 19. Operational amplifier 26a
1 has the same function as the error amplifier 26 of FIG. 1, so that this output terminal is connected to the same one as the output level setting circuit 35 of FIG. Although the FV converter 12a is substantially the same as the FV converter 12 of FIG. 1, the first amplifier as shown in FIG.
Between the frequency F1 and the second frequency F2, the velocity voltage increases substantially in proportion to the frequency. Other configurations in FIG. 13 are the same as those in FIG.

In the circuit of FIG. 13, when the charging voltage of the capacitor 19 becomes lower than a predetermined value, the diode 24 conducts, and the capacitor 19 is charged by the voltage of the power supply terminal 42. Thus, the same operation and effect as those of the first embodiment can be obtained.

[0023]

Third Embodiment FIG. 15 shows a part of a feedback control circuit according to a third embodiment. Here, since the FV converter 12 outputs a speed voltage that changes in inverse proportion to the input frequency, as in FIG. 1, the two operational amplifiers 26a and 50 connected in series both operate as inverting amplifiers. That is, the operational amplifier 26a, the capacitor 19, and the resistor 1
The integration circuit composed of 8, 40 and 41 is configured in the same manner as in FIG. 13, and an inverting amplification circuit composed of an operational amplifier 51 and resistors 52 and 53 is connected to this. In FIG. 15, the direction of the diode 24 connected between the nonpolar capacitor 19 and the power supply terminal 50 for providing a holding voltage is opposite to that in FIG. The feedback control circuit according to FIG. 15 is the same as FIG. 1 except that the parts of the integration circuit 16 and the error amplifier 26 in FIG. 1 are changed as shown in FIG. it can.

[0024]

Fourth Embodiment FIG. 16 shows a part of a circuit obtained by adding an overcharge prevention circuit 60 to the feedback control circuit of FIG.
The overcharge blocking circuit 60 includes voltage dividing resistors 62 and 63 connected between a DC power supply terminal 61 and a ground, and a diode 64 as a backflow blocking element. Resistance 62, 6
3 divides the voltage of the power supply terminal 61 and supplies the voltage V to the voltage dividing point P2.
to get d. One end of the capacitor 19 is connected to the voltage dividing point P2 via the diode 64. The voltage Vc of the capacitor 19 is changed to the voltage Vd at the voltage dividing point by the diode 64.
When it becomes higher than the second predetermined value V2 obtained by adding the forward voltage Vf, the diode 64 becomes conductive and the discharge circuit of the capacitor 19 is formed. This prevents the capacitor 19 from being charged above the second predetermined value V2. In the circuit of FIG. 16, of course, V2> V1 and Vd> V
It is set to a. In FIG. 16, the overcharge prevention circuit 6
Other than 0, the configuration is the same as that of FIG. Therefore, FIG.
According to this circuit, the same effect as that of the first embodiment can be obtained and also the effect of preventing the capacitor 19 from being overcharged can be obtained. If overcharging is prevented in this way, the upper limit of Vo is kept within the servo lock range even if the load is transiently heavy (large), so the load suddenly decreases from the heavy load state. It is possible to prevent the motor from running out of control.

[0025]

[Fifth Embodiment] The feedback control circuit shown in FIG. 17 is obtained by changing a part of the feedback control circuit shown in FIG. In this circuit, a frequency comparator 70 is provided, in which the output frequency of the speed detector 11 made of FG is compared with the reference frequency of the reference frequency source 71, and this output is smoothed by the low-pass filter 72 and the integration circuit 16 outputs the same. It becomes an input, and this output is input to the motor drive circuit 3. FIG.
The voltage drop of the capacitor 19 of No. 7 is also prevented by the charging circuit 20, so that the same effect as that of the first embodiment can be obtained.

[0026]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) In FIG. 1, the charging voltage Va of the charging circuit 20 can be adjusted by the variable resistor 23. Alternatively, a plurality of types of voltage sources may be provided and selectively connected to the diode 24 via the selection switch. The overcharge prevention circuit 60 of FIG.
Also in the above, instead of adjusting the voltage Vd by the variable resistor 63, a plurality of power supplies can be provided and connected to the cathode of the diode 64 via the selection switch. (2) A circuit for controlling the phase so that the phase of the frequency signal corresponding to the rotation of the motor 1 coincides with the phase of the reference frequency signal is provided, and this output is combined with the output of the FV converter 12 to integrate the output. 16 can be input. (3) The configurations of the feedback control circuit and the integration circuit can be variously modified.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a speed control circuit of a capstan motor of a magnetic tape recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an input frequency and an output speed voltage of the FV converter of FIG.

FIG. 3 is a diagram showing a voltage change of each part of the integration circuit when the circuit of FIG. 1 is started.

FIG. 4 is a diagram showing a voltage change of each part of the integrating circuit at the time of startup when a capacitor charging circuit is omitted from the circuit of FIG. 1;

FIG. 5 is a diagram showing a change in the rotation speed of the motor at the time of startup in the circuit of FIG. 1;

FIG. 6 is a diagram showing a change in the rotation speed of the motor at the time of startup when the capacitor charging circuit is omitted from the circuit of FIG. 1;

FIG. 7 is a graph showing the rotation speed of the motor is changed from a second speed to a first speed in FIG.
FIG. 6 is a diagram showing voltage changes at various parts of the integration circuit when switching to the speed of FIG.

FIG. 8 is a diagram showing voltage changes of respective parts of the integration circuit when switching from the second speed to the first speed when the charging circuit is omitted from the circuit of FIG. 1;

9 is a diagram showing a change in the rotation speed of the motor at the time of speed switching in the circuit of FIG. 1;

FIG. 10 is a diagram showing a change in the rotation speed of the motor when the speed is changed when the charging circuit is omitted from the circuit of FIG. 1;

FIG. 11 is a circuit diagram showing a conventional integration circuit.

FIG. 12 is a frequency characteristic diagram of the integration circuit of FIG. 11;

FIG. 13 is a circuit diagram showing a part of a feedback control circuit according to a second embodiment.

14 is a diagram showing a relationship between an input frequency and an output voltage of the FV converter in FIG.

FIG. 15 is a circuit diagram showing a part of a feedback control circuit according to a third embodiment.

FIG. 16 is a circuit diagram showing a part of a feedback control circuit according to a fourth embodiment.

FIG. 17 is a circuit diagram showing a part of the feedback control circuit of the fifth embodiment.

[Explanation of symbols]

 Reference Signs List 16 integration circuit 17, 18 resistor 19 integration capacitor 20 charging circuit 24 diode

Claims (4)

[Claims] 1. A frequency signal generator for generating a frequency signal corresponding to a rotation speed of a motor, and a device for converting an output frequency signal of the frequency signal generator into a voltage signal, wherein the output frequency signal is A constant high level voltage (VH) is generated when it is in a region lower than the first predetermined frequency (F1), and the output frequency signal is a second predetermined frequency (VH) higher than the first predetermined frequency (F1). When it is in a region higher than F2), a constant low level voltage (VL) lower than the high level voltage (VH) is generated, and the output frequency signal is the first predetermined frequency (F1).
) And the second predetermined frequency (F2) between the high level voltage (VH) and the low level voltage (VL) which are inversely proportional to the change of the output frequency signal. Frequency configured to occur between −
A voltage converter and a speed changeover switch for changing over the speed of the motor, and the speed changeover switch for changing over the motor from a high rotation speed state to a lower rotation speed state. The low level voltage (VL) is generated from the frequency-voltage converter in response to the operation of the motor, and is inversely proportional to the output frequency signal when the rotation speed of the motor is in the speed controllable range. Speed switching control means for generating a speed voltage that changes from the frequency-voltage converter, an integrating capacitor and a resistor, and the frequency-voltage converter to integrate the speed voltage obtained from the frequency-voltage converter. Corresponding to an integrating circuit connected to the voltage converter, a reference voltage generating circuit, and a difference between the integrated output voltage obtained from the integrating circuit and the reference voltage obtained from the reference voltage generating circuit. A differential signal forming circuit for generating a voltage, a motor driving circuit that drives the motor in response to the output of the differential signal forming circuit, and a voltage for preventing the integration capacitor from falling below a predetermined value. And a motor speed control circuit including a charging circuit for operating the motor. 2. The difference signal forming circuit is an error amplifier having first and second input terminals, the reference voltage generating circuit is connected to the first input terminal, and the integrating circuit is the second input terminal. The integrating circuit is connected to an input terminal, and the integrating circuit is provided between a first resistor connected between the frequency-voltage converter and the second input terminal and between the second input terminal and the ground. 2. A series circuit of a second resistor and an integrating capacitor connected to the charging circuit, wherein the charging circuit is a voltage source connected to the integrating capacitor via a diode. Motor speed control circuit. 3. An operational amplifier having first and second input terminals and an output terminal instead of the integrating circuit and the difference signal forming circuit, the frequency-voltage converter, and the first of the operational amplifiers. A first resistor connected between the first input terminal and the output terminal of the operational amplifier, and an integration capacitor connected in parallel via the second resistor between the first input terminal and the output terminal of the operational amplifier. The motor speed control circuit according to claim 1, wherein the reference voltage generation circuit is provided and the reference voltage generation circuit is connected to the second input terminal of the operational amplifier. 4. A frequency signal generator for generating a frequency signal corresponding to the rotation speed of a motor, a reference frequency source for generating a reference frequency, an output frequency signal of the frequency signal generator and the reference frequency. A comparator for comparing, an integrating circuit for integrating the output of the comparator, the integrating circuit having an integrating capacitor and a resistor; and a voltage of the integrating capacitor lower than a predetermined value. A motor speed control circuit comprising a capacitor charging circuit for preventing this and a motor driving circuit for driving the motor in response to the output signal of the integrating circuit.