JP2672886B2 - DC servo motor pulse drive system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Table of Contents] Outline Industrial field of application Conventional technology (FIGS. 4 to 10) Problem to be solved by the invention Means for solving the problem (FIG. 1) Action Example (FIGS. 2 and 3) Effects of the Invention [Overview] With respect to a pulse drive system of a DC servo motor, it is possible to accurately and completely perform pulse width modulation with a constant repetition pulse period, and to accurately measure motor torque. With the aim of enabling control and reducing the ripple of the power supply current, the generated torque is controlled by continuously changing the armature current of the DC servo motor by pulse driving, and controlling the generated DC servo motor. , In the pulse drive method of the DC servo motor that starts, stops, or drives to rotate at a constant speed,
A clock circuit that generates a clock signal of a constant cycle, a frequency division counter circuit that counts the clock signal and obtains a frequency division output, and two clock signals that are converted into analog signals output from the frequency division counter circuit. A DA conversion circuit is provided,
The output signals of all the digits of the frequency division counter circuit are directly input to one DA conversion circuit, and the output signal of the most significant digit of the outputs of the frequency division counter circuit is input to the other DA conversion circuit. By inverting and inputting, and inputting the output signals of the remaining digits as they are, the ramp voltages with phase shifts are generated at the outputs of the two DA conversion circuits,
By using these lamp voltages, two sets of drive pulse signals each having a repetitive pulse phase difference are generated, and the two sets of drive pulse signals are configured to simultaneously drive two sets of DC servo motors.

[Industrial applications]

The present invention relates to a pulse drive system for a DC servo motor,
More specifically, the present invention relates to a pulse drive system of a DC servo motor used for a reel motor of a small magnetic tape device and the like, and particularly capable of controlling output torque with high accuracy over a wide range.

[Conventional technology]

4 to 10 are diagrams showing a conventional example.
Fig. 5 is a block diagram of the motor control unit, Fig. 5 is a block diagram of the PWM conversion circuit, Fig. 6 is an explanatory diagram of the power amplifier circuit (during driving mode), and Fig. 7 is an explanatory diagram of the power amplifier circuit ( (In the regenerative power generation control mode), FIG. 8 is a waveform diagram of each part in the circuit of FIG. 5, FIG. 9 is another circuit example of the PWM conversion circuit,
FIG. 10 is a waveform chart of each part in the circuit of FIG.

In the figure, 1 and 2 are reel motors, 3 is a motor drive control circuit, 4 and 5 are DA conversion circuits, 6 and 7 are addition amplification circuits, 8 and
9 is a PWM conversion circuit, 10 and 11 are switching control circuits, 1
2, 13 is a power amplification circuit, 14 and 15 is a current detection circuit, 16 is a tachometer, 17 is a speed measurement circuit, 18 is a tension sensor, 19 is a tension detection circuit, 20 is an inverting amplification circuit, 21 and 22 are comparators, 23 Is a polarity determination circuit, 24 is a ramp waveform generation circuit, R ₁ ~
R ₃ is a resistor and C ₁ is a capacitor.

Further, Q _{1 to} Q ₄ are drivers (transistors), M is a motor, D _{1 to} D ₄ are diodes, R ₄ is a current detection resistor, 24 is a clock circuit, 25 is an RS flip-flop (FF), and 26 is Constant current circuit, C ₂ is a capacitor, N is an inverter.

The motor control unit used in the conventional small magnetic tape device is configured as shown in FIG. 4, for example.

That is, the motor control section for controlling the reel motors 1 and 2 includes a motor drive control circuit 3, a DA conversion circuit 4,
5, summing amplifier circuits 6 and 7, PWM (pulse width modulation) converter circuits 8 and 9, switching control circuits 10 and 11, power amplifier circuit
12, 13, current detection circuits, 14, 15, tachometer 16, speed measurement circuit 17, tension sensor 18, tension detection circuit 19, and power amplification circuits 12, 13 are provided.

The switching control circuits 10 and 11 select ON / OFF of four drive elements of the power drive circuit based on a PWM drive signal, a drive direction signal, and a drive polarity signal, and control switching of a current flowing through a motor coil. And operates in the drive mode and the regenerative braking mode.

The power amplifier circuits 12 and 13 are switching control circuits 10 and 11, respectively.
A drive current is supplied to the motor winding in response to a signal from the motor to drive the motor. The current detection circuits 14 and 15 amplify the signal detected as the voltage drop of the current detection resistors provided in the power amplification circuits 12 and 13 to detect the motor current. The addition amplifier circuits 6 and 7 add the instruction value from the motor drive control circuit 3, the motor current feedback signal (negative polarity), and the tension feedback signal, and in addition to the motor drive circuit section, control the motor current. I do.

The PWM conversion circuits 8 and 9 generate a pulse train for driving a motor pulse, and based on the motor current instruction signal from the addition amplification circuits 6 and 7, the pulse switching cycle is constant and the duty ratio thereof is the input voltage. Is output to the power amplification circuits 12 and 13 through the switching control circuits 10 and 11.

The DA conversion circuits 4 and 5 convert the motor drive instruction value (digital value) processed by the motor drive control circuit 3 into an analog voltage value to generate a motor drive signal.

The motor drive control circuit 3 starts / starts the motor in response to a motor drive instruction signal (tape running / stop instruction) from the upper portion.
The running / stopping operation is executed, and the actual rotation speed of the motor is detected, compared with a reference value, the difference is applied to the motor, and the motor is driven to control the rotation speed of the motor.

As shown in FIG. 5, the PWM conversion circuits 8 and 9 are composed of comparators 21 and 22, an inverting amplifier circuit 20, a polarity discriminating circuit 23, a ramp waveform generating circuit 24, and the like.

The ramp waveform generation circuit 24 generates a ramp voltage by using the charging / discharging voltage of the capacitor C, and the ramp voltage Vp that is the output voltage thereof is the above-mentioned two comparators 2.
While inputting to 1 and 22, the lamp voltage is also supplied to the PWM conversion circuit of other motor drive circuits.

The comparator 21 inputs the ramp voltage Vp and the output voltage of the inverting amplifier circuit 20 for comparison, and makes a comparison when the output voltages of the addition amplifier circuits 6 and 7 are on the negative side.

Further, the comparator 22 inputs the lamp voltage Vp and the output voltage of the addition amplification circuits 6 and 7 and performs comparison, and performs comparison when the output voltages of the addition amplification circuits 6 and 7 are on the positive side. .

Voltage output from the above two comparators 21 and 22
Vd (which is not simultaneously output from the two comparators) is supplied to the switching control circuits 10 and 11 as a PWM pulse drive signal.

The polarity discriminating circuit 23 is a circuit for discriminating the polarities of the output voltages of the summing amplifier circuits 6 and 7, and the output thereof is supplied to the switching control circuits 10 and 11 as a drive polarity signal.

The switching control circuits 10 and 11 select the PWM pulse drive signal using the drive polarity signal (comparator 2
Select the output of 1 or the output of 22), and control the switching of the driver of the power amplifier circuit.

For example, the circuits shown in FIGS. 6 and 7 are used as the power amplifier circuits 12 and 13.

Between source + VM and ground, two source drivers Q ₁ ,
A series circuit of motor M and current detection resistor R ₄ is provided between Q ₃ and two sink drivers Q ₂ and Q ₄ , and between the connection point of Q ₁ and Q _{2 and} the connection point of Q ₃ and Q _4. Connect.

Also, diodes D _{1 to} D ₄ are connected in parallel with the drivers Q _{1 to} Q ₄ , respectively.

In the drive mode, as shown in FIG. 6, Q ₂ , Q ₃ are turned off, Q ₄ is turned on, and Q ₁ is on / off controlled.
This control is performed by the switching control circuit and servo-controls the motor M.

When Q ₁ is on, + VM → Q ₁ → R ₄ →
Current flows in the order of M → Q ₄ → ground, and when Q ₁ is off, the current flows in the order of M → Q ₄ → D ₂ → R ₄ → M due to the electromagnetic energy of the motor.

In the regenerative braking mode, as shown in FIG.
The Q _1, Q _3, Q ₄ is turned off and turned on / off control of the Q _2.

In this case, when Q ₂ is on, as shown by the dotted line in the figure, M
The current flows in the order of → Q ₂ → D ₄ → M, and when Q ₂ is off, the current flows in the order of ground → D ₄ → M → D ₁ → + VM and returns the power to the power supply.

By the way, for example, in a small magnetic tape device,
A DC servo motor is used as a reel motor that runs a magnetic tape that is a recording medium. In order to drive this DC servo motor, a pulse drive method such as pulse width modulation (PWM) drive is adopted to reduce the size of the device and reduce power consumption.

Further, speed control and tension control are performed in order to record / reproduce data by causing the recording medium to travel bidirectionally at a constant speed while maintaining a predetermined tension. Therefore, the motor drive uses a current drive method that is easy to change the motor output torque accurately and directly.

The running control method of the magnetic tape is as follows. The take-up reel side motor drives in the forward direction to wind up the tape, and the pay-out reel side motor drives in the reverse direction to apply tension to the tape and change both motor torques to control the running speed and tension. To do.

If the rotating motor is controlled by pulse drive here, it will be in the normal switching drive mode during forward drive, but it will be necessary to control the current due to the motor electromotive force during reverse drive as well. To the regenerative power generation control mode.

On the other hand, the motor current drive control method is as follows.
To detect the motor drive current, a low resistance for current detection (resistance R _{4 in} FIGS. 6 and 7) is always provided in the path that flows in one direction.
Is inserted, and the voltage drop that occurs when the motor drive current flows is amplified by the current detection circuit (see FIGS. 6 and 7),
The method using the motor current signal is used.

Also, since the drive current instruction value is applied to the input of the drive circuit, the motor current signal is fed back to this and the motor is driven by the difference between them, so that the motor current becomes a value according to the input instruction value. Control.

Next, the operation of the PWM conversion circuit shown in FIG. 5 will be described in detail with reference to the waveform chart of FIG.

The output of the summing amplifier circuit is a voltage that changes to positive or negative, and the ramp voltage Vp is a positive voltage. Now, for example, the output voltage of the summing amplifier circuit is + V as shown in FIG.
_The lamp voltage Vp changes to 0 [V] and + V ₃ [V]
It is assumed that the voltage changes from [V] to + V ₄ [V] (provided that V ₂ <
V ₃ <V ₄ ).

At this time, the PWM drive pulse signal Vd is Vp> V ₂ or V
It becomes 0 [V] when p> V ₂ and becomes + V ₁ [V] when Vp <V ₂ or Vp <V ₃ .

Therefore, Vd becomes a pulse as shown, and Vd = +
The driver is controlled so that it is turned on at V ₁ and turned off at Vd = 0.

In this case, if the frequency of the lamp voltage Vp is kept constant, the frequency of Vd is also kept constant.

In addition, when the output of the summing amplifier circuit is + V ₂ [V],
The pulse width of Vd becomes wider when it becomes V ₃ [V] (W ₁ <W ₂ <W ₃ ).

That is, if the output voltage of the summing amplifier is lowered, the PWM
The pulse width of the drive pulse signal becomes narrower, and the higher it becomes, the wider the pulse width becomes.

In the case of the PWM conversion circuit as described above, the PWM drive pulse signal is generated by inputting the ramp voltage using the charge / discharge voltage of the capacitor to the comparator and comparing it with the output voltage of the addition amplification circuit. For this reason, the accuracy of comparison by the comparator is poor, and an accurate PWM drive pulse signal cannot be obtained (frequency is also incorrect). As a modification of this point, a PWM conversion circuit as shown in FIG. 9 has been conventionally considered.

The PWM conversion circuit shown in FIG. 9 includes an inverting amplifier circuit 20, comparators 21 and 22, a clock circuit 24, an RS flip-flop (FF) 25, a constant current circuit 26, and a capacitor C ₂ .

In this circuit, the clock output from the clock circuit 24 is input to the set terminal S of the RS flip-flop 25, and the outputs of the comparators 21 and 22 are input to the reset terminal R of the RS flip-flop 25.

Also, one output of the RS flip-flop 25 (*
Q) is the lamp voltage Vp, and the inverted signal of the other output (Q) is the PWM drive pulse signal.

The operation of FIG. 9 will be described below with reference to the waveform chart of FIG.

When the clock P ₁ is input to the set terminal S of the RS flip-flop 25 at time t ₁ , the * Q output becomes high level and the constant current circuit 26 charges the capacitor C ₂ . Therefore, Vp gradually rises according to the charging voltage of the capacitor C ₂ . At time t ₂ , the output voltage Va of the summing amplifier circuit
And the lamp voltage Vp are equal, the comparator 21,
Or the output of 22 is inverted and RS flip-flop 25
Reset. With this reset, the * Q output becomes low level and the capacitor C ₂ is discharged. Therefore, from t ₂
Vp falls.

When the clock P ₂ is output again at time t ₃ , the * Q output becomes high level and the capacitor C ₂ is charged, and then at time t ₄ , * Q becomes low level and the capacitor C ₂ is discharged. Thereafter, the capacitor C ₂ is repeatedly charged and discharged in the same manner, and as a result, the ramp voltage Vp as shown is generated.

Further, in synchronization with the setting and resetting of the RS flip-flop 25, the PWM drive pulse signal Vd changes as shown in the figure. Then, since the pulse width of Vd changes according to the change of Va, if the driver is driven by this pulse,
The servo motor can be controlled.

[Problems to be solved by the invention]

The prior art as described above has the following disadvantages.

(1) When the PWM conversion circuit as shown in FIG. 5 is used, ON / OFF of the PWM drive pulse signal Vd is determined by the ramp waveform using charge / discharge of the capacitor.

Therefore, the precision of the pulse is poor and accurate control cannot be performed.

(2) With the improved PWM conversion circuit shown in Fig. 9, the above points can be improved (especially the frequency becomes accurate), but in this case as well, the ramp waveform must charge and discharge the charge of the capacitor. Is caused by.

Therefore, it is necessary to discharge the charge before starting the charge. This discharge period is a PWM conversion pause period, so the duty ratio of the conversion pulse does not reach 100% with respect to the maximum input voltage, and the power amplifier circuit cannot drive at maximum capacity (saturation), resulting in reduced efficiency. To do.

That is, it is desirable to perform pulse width control by keeping the frequency constant and changing the duty ratio (on / off pulse ratio) between 0 and 100%. There is no control.

(3) When two sets of motors are driven at the same time, the same ramp waveform is used for each pulse width conversion, so the on / off of the drive pulse is completely synchronized (pulse The centers match). As a result, the drive phases of the two motors match and the drive current flows at the same time,
The ripple of the motor drive power supply current increases.

Therefore, the scale of the smoothing circuit of the power source becomes large (a large capacitor is required), and it becomes difficult to downsize the device. In addition, the power supply system induced noise due to the current ripple increases, causing malfunction of other minute signal circuits.

(4) In the pulse drive as described above, the drive element, the motor winding, and the core vibrate due to the intermittent drive current,
Since noise is generated, this frequency is usually set outside the audible range (about 20 KHz or more) to reduce noise.

However, since the repetition frequency of the ramp waveform depends on the time constant of the oscillation circuit, the frequency may change due to the deviation of the circuit elements, and the frequency shifts within the audible range, causing unpleasant high-frequency noise.

The present invention eliminates the above-mentioned conventional drawbacks, enables accurate and complete pulse width modulation with a constant repetitive pulse period, and enables accurate control of the motor torque to prevent ripples in the power supply current. The purpose is also to reduce.

[Means for solving the problem]

FIG. 1 shows the principle of the present invention. In the figure, 30 is a clock circuit, 31 is a frequency division counter circuit, 32 and 33 are DA conversion circuits (digital and analog conversion circuits), 34 is an inverter, COMP.
Indicates a comparator.

The present invention is configured as follows to achieve the above object.

Pulse driving of a DC servo motor that continuously changes the armature current of the DC servo motor by pulse driving, controls the generated torque, and drives the DC servo motor to start, stop, or rotate at a constant speed. In the scheme,
A clock circuit 30 for generating a clock signal of a constant cycle,
A frequency division counter circuit 31 for counting the clock signal and obtaining a frequency division output, and the frequency division counter circuit
Two DA conversion circuits that convert the output of 31 to an analog signal 3
2 and 33 are provided, and the output signals of all the digits of the frequency division counter circuit 31 are directly input to one DA conversion circuit 32, and the other DA conversion circuit 32 is input.
Of the outputs of the frequency division counter circuit 31, the output signal of the most significant digit is inverted and input to the DA conversion circuit 33, and the output signals of the remaining digits are input as they are.
At the outputs of the DA conversion circuits 32 and 33, ramp voltages having a phase shift are generated respectively, and using these ramp voltages, two sets of drive pulse signals Vp1 and Vp2 having a phase shift of a repetitive pulse are generated, By the two sets of drive pulse signals,
It is configured to drive two sets of DC servo motors at the same time.

[Action]

Since the present invention is configured as described above, the following operation is provided.

The clock signal output from the clock circuit 30 is counted by the frequency division counter circuit 31, and its output is converted into an analog signal by the DA conversion circuit 32.

This analog signal becomes a large voltage as the count value of the clock signal becomes large, and becomes the maximum value when all the digits of the frequency division counter circuit 31 become "1". After that, all the digits become “0”, and the ramp voltage increases again according to the magnitude of the count value of the clock signal.

This lamp voltage is compared with the motor drive instruction signal from the upper circuit by the comparator COMP, and a drive pulse signal (PWM drive pulse signal) having a pulse width proportional to the magnitude of this motor drive instruction signal is output.

The drive pulse signal is used when performing pulse drive of the DC servo motor.

Further, in the DA conversion circuit 33, of the outputs of the frequency division counter circuit 31, while inverting and inputting the output signal of the most significant digit,
Since the output signals of the remaining digits are directly input, the output of the DA conversion circuit 33 generates a ramp voltage Vp2 having a phase difference from the ramp voltage Vp1. The ramp voltage Vp2 is compared with the motor drive instruction signal from the upper circuit by another comparator, and a drive pulse signal (PWM drive pulse signal) having a pulse width proportional to the magnitude of the motor drive instruction signal is output.

As described above, the ramp voltages Vp1 and Vp2, which are out of phase with each other, are generated at the outputs of the two DA conversion circuits 32 and 33, and using these ramp voltages, two sets of pulses with repetitive pulse out of phase are set. A drive pulse signal is generated, and the two sets of drive pulse signals drive two sets of DC servo motors at the same time.

By doing so, the ramp voltage is generated based on the count value of the clock signal, so that the linearity is good, and the repetition cycle thereof is constant, and the discharge time of the conventional capacitor is not required. Therefore, if this ramp voltage is used, the conversion pulse width is almost completely 0-100.
It can be continuously changed in the range of%.

When two DA conversion circuits 32 and 33 are provided to drive two motors, the highest digit of the frequency division counter circuit 31 input to the DA conversion circuit 33 is inverted by the inverter 34 and input. At the outputs of the two DA converters 32 and 33, ramp voltages Vp1 and Vp2 with a half-cycle phase shift are generated. A drive pulse signal (PWM drive pulse signal) is obtained by introducing the ramp voltages Vp1 and Vp2 to separate motor circuits and comparing them with a motor drive instruction signal by a comparator.

The drive pulse signals are two sets of drive pulse signals having a constant repetition cycle (constant frequency) and a phase shift of a half cycle. Therefore, if the two DC servomotors are driven by this signal, the superposition of the drive power supply currents is reduced.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram of a PWM conversion circuit in one embodiment of the present invention, and FIG. 3 is a waveform diagram of each part of FIG.

 In the figure, the same reference numerals as those in FIG. 1 indicate the same elements.

 Reference numeral 35 indicates an inverter (NOT circuit).

This embodiment is an example in which two servo motors are simultaneously driven by a circuit having the same configuration as the motor control unit shown in FIG. 4, and at that time, the PWM conversion circuit 8 is configured as shown in FIG. is there.

The PWM conversion circuit in this embodiment is a clock circuit 3
0, a frequency division counter circuit 31, DA conversion circuits 32 and 33, inverters 34 and 35, an inverting amplifier circuit 20, and comparators 21 and 22.

The clock circuit 30 outputs a clock signal at a constant cycle, and this clock signal is a frequency dividing counter circuit.
Enter 31.

The frequency divider / counter circuit 31 counts clock signals and also performs frequency division. In this example, the 8-bit configuration of B0 to B7 is used, and the output of B7, which is the most significant digit, is directly input to the DA conversion circuit 32, and the output of B7 is input to the DA converter 33 via the inverter 34.

The outputs of the remaining digits B0 to B6 are directly input to the DA conversion circuits 32 and 33. A ramp voltage Vp1 is generated at the output of the DA converter 32, and this ramp voltage Vp1 is a comparator voltage.
Enter in 21 and 22.

The lamp voltage Vp2 generated at the output of the DA conversion circuit 33 is sent to another motor circuit and input to the comparator.

If the above is done, for example, when the count value of the frequency division counter circuit 31 is 0, “B7, B6 ... B0” becomes “00000000”.
However, “00000000” is input to the DA conversion circuit 32 and “10000000” is input to the DA conversion circuit 33. After that, when the clock signal is counted, the count value of the frequency division counter circuit 31 is "00000001", "00000010", "00".
000011 ”…… changes like this.

The above count value is directly input to the DA converter 32, but the values input to the DA converter 33 are "10000001" and "10".
It changes like “000010”, “10000011” ....

Therefore, if the above input value is converted into an analog signal,
Lamp voltages Vp1 and Vp2 as shown in FIG. 3 are generated.
The ramp voltages Vp1 and Vp2 have different values input to the DA converter, and thus are signals with a phase shift (half-cycle phase shift in this example).

When these ramp voltages Vp1 and Vp2 are input to the comparator and a PWM drive signal is generated in the same manner as in the conventional example, PWM drive pulse signals P1 and P2 having waveforms as shown in FIG. 3 are obtained.

Using these signals P1 and P2, pulse driving of two DC servo motors is performed. To perform this pulse drive, the sixth
Driving is performed using the power amplifier circuit as shown in FIGS.

Although the embodiments have been described above, the present invention can be implemented as follows.

(1) The frequency division counter is not limited to the 8-bit configuration described above, but may be any frequency division counter.

 Further, it is not necessary to use all digits (all bits).

(2) The DC servo motor can be applied not only to the reel motor of the small magnetic tape device but also to the DC servo motor of other devices.

(3) An example in which the phase difference between the PWM drive pulse signals is set to a half cycle when driving the two DC servo motors has been described, but the phase difference may not be a half cycle.

However, when there is a half-cycle phase difference, it is most efficient, and therefore it is normally used in a state with this phase difference.

〔The invention's effect〕

As described above, the present invention has the following effects.

(1) The lamp voltage used when performing pulse width modulation is
Since the value obtained by counting the clock signal is converted into an analog signal, it has excellent linearity, and its repetition cycle (frequency) is always constant. Therefore, the PWM drive pulse signal converted using the ramp voltage becomes a pulse signal with extremely high accuracy.

(2) Since the capacitor is not used when generating the lamp voltage unlike the conventional example, there is no discharge time of the capacitor.

Therefore, the conversion pulse width of the PWM drive pulse signal is
It becomes possible to change almost continuously from 0% to 100% almost completely.

(3) When driving the two motors, if the driving pulse signals are driven by shifting the phase (for example, shifting by half a cycle),
The motor torque can be controlled with high accuracy, and the ripple of the power supply current can be reduced.

(4) If the ripple is reduced, the scale of the smoothing circuit is also reduced, and the device can be downsized.

Further, the power supply system induced noise due to the current ripple is also reduced, and malfunctions of other circuits are reduced.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a block diagram of a PWM conversion circuit in one embodiment of the present invention, FIG. 3 is a waveform diagram of each part of FIG. 2, and FIGS. FIG. 4 is a diagram showing a conventional example, FIG. 4 is a block diagram of a motor control unit, FIG. 5 is a block diagram of a PWM conversion circuit, and FIGS. 6 and 7 are explanatory diagrams of a power amplification circuit. FIG. 8 is a waveform diagram of each part of FIG. 5, FIG. 9 is another circuit example of the PWM conversion circuit, and FIG. 10 is a waveform diagram of each part of FIG. 30 …… Clock circuit 31 …… Division counter circuit 32, 33 …… DA conversion circuit 34 …… Inverter COMP …… Comparator

Claims (1)

(57) [Claims] 1. A pulse drive is used to continuously change the armature current of a DC servo motor to control the generated torque,
In a pulse driving method of a DC servo motor that drives the DC servo motor so as to start, stop, or rotate at a constant speed, a clock circuit that generates a clock signal of a constant cycle, counts the clock signal, and divides the frequency. A frequency division counter circuit that is configured to obtain an output and two DA conversion circuits that convert the output of the frequency division counter circuit into an analog signal are provided. One DA conversion circuit includes all the frequency division counter circuits. The output signal of the digit is input as it is, and the output signal of the most significant digit of the output of the frequency division counter circuit is inverted and input to the other DA conversion circuit, and the output signals of the remaining digits are input as they are. By doing so, a ramp voltage with a phase shift is generated at the outputs of the two DA conversion circuits, and by using these ramp voltages,
A pulse drive system for a DC servo motor, characterized in that two sets of drive pulse signals each having a repetitive pulse phase difference are generated, and two sets of the DC servo motors are simultaneously driven by the two sets of drive pulse signals.