JPS6258898A - Drive circuit for stepping motor - Google Patents

Abstract

PURPOSE:To remove the vibrations of a rotor on revolution at low speed, and to obtain output torque required on revolution at high speed by supplying driving voltage having magnitude corresponding to the number of revolution. CONSTITUTION:A pulse signal 21 specifying the number of revolution of a stepping motor 5 is transmitted over a driver circuit 4 from a control section 3. A variable voltage command signal 22 having pulse width corresponding to the frequency of the pulse signal 21 is transmitted over a voltage conversion circuit 6 at the same time as the transmission of the pulse signal 21. Currents turned with the pulse width of the variable voltage command 22 flow through a primary-side winding for a transformer 10, and secondary voltage (driving voltage) Vt is generated in a secondary winding through the transformer. Accordingly, secondary voltage (driving voltage) Vt is changed into voltage corresponding to the pulse width of the variable-voltage command signal 22, and fed to the driver circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a stepping motor drive circuit, and more particularly to a stepping motor drive circuit that uses a constant voltage to drive a stepping motor.

2. Description of the Related Art A conventional stepping motor drive circuit that supplies a voltage of a constant magnitude to drive a stepping motor has a configuration as shown in FIG. 2, an example of which is shown in FIG. That is, the pulse signal 21 sent from the control unit 13 to the driver circuit 14 is supplied from the constant voltage power supply 7 in the driver circuit 14, is amplified by the power supply voltage VC, and is supplied to the excitation winding 5a of the stepping motor 5. to drive the rotational movement of. The relationship between the rotational speed of the stepping motor 5 and the output torque at this time exhibits characteristics as shown in FIG.

That is, when the driving voltage is constant and the rotational speed is low, the output torque has a considerable variation, but when the rotational speed exceeds a certain value, the output torque rapidly decreases. Therefore, if the stepping motor is to rotate at high speed and high output torque is required, the driving voltage of the driver circuit must be set to a considerably high voltage.

On the other hand, when a high driving voltage is supplied to a stepping motor to cause it to rotate at a low speed, the stepping motor rotor vibrates as shown in Figure 5, and it takes a considerable amount of time for the stepping motor to stably remain at a given position. Requires. Therefore, if the drive voltage is set to a low voltage in order to avoid such vibration of the rotor, the output torque necessary for high-speed rotation cannot be obtained as described above.

In this way, conventional stepping motor drive voltage control circuits can only supply a constant power supply voltage to the driver circuit, so if the stepping motor needs to be used at two or more rotation speeds, it is necessary to Either it is not possible to obtain output torque, or the rotor of the stepping motor vibrates during low speed rotation, so it takes a considerable amount of time to come to a stable standstill.Both of these needs to be satisfied. The disadvantage is that it cannot be done.

OBJECT OF THE INVENTION The problem to be solved by the present invention is to eliminate the drawbacks of the conventional stepping motor drive circuit as described above.Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and to improve the performance of the stepping motor during high-speed rotation. To provide a stepping motor drive circuit which can obtain sufficient output torque and can quickly and stably stand still without rotor vibration even during low speed rotation.

Structure of the Invention A stepping motor drive circuit according to the present invention includes: a pulse signal generating means for generating a pulse signal of a frequency corresponding to the rotation speed of the stepping motor; a voltage source for generating a power supply voltage for driving the stepping motor; A stepping motor drive circuit including a driver circuit that receives a pulse signal and the power supply voltage as input and generates a drive pulse for driving a stepping motor, and controls the power supply voltage to change in accordance with the rotational speed of the stepping motor. It is characterized by having a voltage conversion circuit.

Example Next, the present invention will be explained in detail with reference to the drawings.

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

As shown in the figure, the voltage i of a constant voltage circuit 7 that supplies a constant power supply voltage VC is input to a variable voltage circuit 6, and the output voltage Vt of this voltage conversion circuit 6 is input to a driver circuit 4. The control section 3 sends out a pulse signal 21 to the driver circuit 4, and also sends out a variable voltage command signal 22 having a pulse width corresponding to the frequency of the pulse signal 21 to the voltage conversion circuit 6. The driver circuit 4 inputs the pulse signal 21 from the control unit 3 and the output voltage (drive voltage) Vt of the conversion circuit 6, and sends a drive pulse signal 23 of a predetermined voltage to the excitation winding 5a of the stepping motor 5 to perform stepping. The motor 5 is driven at a predetermined rotation speed.

The voltage conversion circuit 6 includes an amplifier circuit 8 that inputs a variable voltage command signal 22 sent from the control unit 3, amplifies it, and outputs it, and a power supply voltage Vc from a constant voltage power supply 7 through a transistor 9. A transformer 10 connected to the side winding and rectifying the output from the secondary winding with a capacitor C and a diode D and outputting it as an output voltage Vt, and a transformer 10 connected to the base with the output of the amplifier circuit 8 and regulated by the collector and emitter. The transistor 9 is configured to connect one terminal of the voltage power source 7 and one terminal of the primary winding of the transformer 10.

In the stepping motor drive circuit configured as described above, when the pulse signal 21 specifying the rotation speed of the stepping motor is sent from the control unit 3 to the driver circuit 4, the frequency of the pulse signal 21 is simultaneously changed. Since the variable voltage command signal 22 with the corresponding pulse width is sent to the voltage conversion circuit 6, the amplifier circuit 8 of the voltage conversion circuit 6 amplifies it and sends it to the base of the transistor 9. Therefore, a current that is synchronized with the pulse width of the variable voltage command 22 flows through the primary winding of the transformer 10 and generates a secondary voltage (drive voltage) Vt in the secondary winding through the transformer.

Therefore, the secondary voltage (drive voltage) Vt becomes a voltage corresponding to the pulse width of the variable voltage command signal 22 and is supplied to the driver circuit 4.

In order to specify the rotation speed of the stepping motor 5, the control section 3 sends a pulse signal 21 with a frequency corresponding to the specified rotation speed to the driver circuit 4. At this time, the frequency of the pulse signal 21, that is, the rotation of the stepping motor 5 is A variable voltage command signal 22 with a predetermined pulse width is sent to the voltage conversion circuit 6 so that a drive voltage Vt determined in accordance with the number is obtained. The relationship between the frequency of the pulse signal 21 and the variable voltage command signal, that is, the relationship between the rotation speed of the stepping motor and the drive 1 FIJ voltage, is set by the conditions of the device that uses this stepping motor,
It is assumed that the information is stored in a read-only memory or the like and is built into the control unit.

Figure 3 shows the rotational speed and drive of the stepping motor when driven according to the embodiment shown in Figure 1. 171 is a graph showing an example of the relationship with voltage, drive voltages V1 to V5 are set for rotation speeds r1 to r5, and when the rotation speed is low, the voltage is set to be low so that vibration of the stepping motor rotor does not occur. , so that sufficient output torque can be obtained at high rotations.
voltage.

FIG. 4 is a chart showing the relationship between the rotation speed and output torque of the stepping motor using the drive voltage set as shown in FIG. 3 as a parameter. As shown in the figure, when the drive voltage is constant, the output torque decreases as the rotation increases.
It is accepted that the rotational speed tends to drop rapidly when it exceeds a certain value, but as the drive voltage increases, the overall output torque increases and the rotational speed at which it starts to drop rapidly also increases. Therefore, when the rotational speed of the stepping motor is set to r1 to r5, the output torque can have a value of T1 to T5 by setting the driving voltage at that time to 1 to V5. Therefore, it becomes possible to use the stepping motor with desired characteristics.

Effects of the Invention As described in detail above, the stepping motor drive circuit of the present invention can supply a driving voltage of an optimal magnitude corresponding to the rotational speed of the stepping motor. By using a motor drive circuit, in devices that require the stepping motor to be driven at multiple rotational speeds, there is no rotor vibration during low-speed rotation, and the necessary output torque can be obtained during high-speed rotation. There is.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a conventional stepping motor drive circuit, and FIG. 3 is a circuit diagram of a stepping motor when driven by the embodiment shown in FIG. Graph showing the relationship between rotation speed and drive voltage,
FIG. 4 is a graph showing the relationship between the rotation speed and output torque of the stepping motor using the drive voltage as a parameter, and FIG. 5 is a graph showing the movement of the rotor of the stepping motor. Explanation of symbols of main parts 3... Control section 4... Driver circuit 5... Stepping motor 6... Voltage conversion circuit 7... Constant voltage source Figure 1 Figure 2

Claims (1)

[Claims] a pulse signal generating means for generating a pulse signal with a frequency corresponding to the rotational speed of the stepping motor; a voltage source for generating a power supply voltage for driving the stepping motor;
A stepping motor drive circuit including a driver circuit that receives the pulse signal and the power supply voltage as input and generates a drive pulse for driving the stepping motor, the stepper motor drive circuit changing the power supply voltage in accordance with the rotational speed of the stepping motor. A stepping motor drive circuit characterized by having a voltage conversion circuit for controlling.