JP2804204B2 - Stepping motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unipolar drive circuit for driving a stepping motor to rotate.

[0002]

2. Description of the Related Art In FIG. 2, reference numeral 10 denotes a stepping motor, which is a four-phase motor having phase coils φA and φC and phase coils φB and φD which are magnetically coupled. The drive circuit is
An electric circuit 1 for connecting the phase coils φA to φD of the stepping motor 10 to the driving power supply VH;
And a phase switching circuit connected between the ground G. Each of the phase switching switching circuits includes transistors Q1 to Q4 and diodes D1 to D4 connected in parallel. Each of the transistors Q1 to Q4 is turned on and off in a predetermined order by a phase switching signal Aph to Dph from the control circuit 15. Controlled.

[0003] A protection fuse 5 is interposed in the electric circuit 1, and a drive power supply side electric circuit I centered around the fuse 5.
A first smoothing capacitor C1 is provided between the first connection point T11 and the ground G, and a second smoothing capacitor C2 is provided between the connection point T12 of the phase coil side electric circuit 12 and the ground G.

In such a unipolar type driving circuit, the phase switching signals Aph to Dph are switched and output in a predetermined order, so that the stepping motor 10 can be rotationally controlled at a predetermined speed in a predetermined direction. Here, for example, focusing on the magnetically coupled phase coils φA and φC, the transistor Q1
Is ON and the current i1 is flowing through the phase coil φA, turning off the transistor Q1 generates a current i2 in the phase coil φC due to mutual induction. This current i2 depends on the resistance value of the fuse 5, the first and second smoothing capacitors C1,
As divided currents i21 and i22 based on a division ratio determined by the capacitance value and the internal resistance of C2, the current flows into each of the smoothing capacitors C1 and C2 and is charged. The charge thus charged is consumed the next time another phase coil (for example, φB) is excited. Further, a part thereof is discharged through an internal resistance or the like of the driving power supply device.

[0005]

The divided current i21 flowing into the first smoothing capacitor C1 passes through the fuse 5. However, the resistance of the fuse 5, which determines the division ratio, and the capacitance values and the internal resistances of the first and second smoothing capacitors C1 and C2 not only have large variations, but also vary due to temperature changes and the like. That is, each divided current i21, i
22 fluctuates. Therefore, especially the maximum current (i21)
As a result, it is difficult to quantitatively and accurately grasp the fuse 5, and as a result, it is very difficult to select the fuse 5, and if there is a mistake in selection, the intrinsic protection function is impaired or unnecessary drive stoppage is caused.

SUMMARY OF THE INVENTION An object of the present invention is to provide a stepping motor drive circuit which facilitates selection of a fuse, exhibits a necessary and sufficient protection function, and can prevent unnecessary drive stoppage due to selection error.

[0007]

SUMMARY OF THE INVENTION A stepping motor drive circuit according to the present invention comprises a protective fuse interposed in a circuit connecting a drive power supply and a phase coil of the stepper motor, and a drive centered on the fuse. A driving circuit for a stepping motor having a first smoothing capacitor connected between the power supply side electric circuit and the ground and a second smoothing capacitor connected between the phase coil side electric circuit and the ground. One phase coil magnetically coupled to the stepping motor and the other between the first smoothing capacitor connection point and the fuse or between the fuse and the second smoothing capacitor connection point on the phase coil side electric circuit. A diode for preventing a current based on a mutual induction action generated by switching between the phase coils of the first and second phase coils from flowing into the first smoothing capacitor. Characterized in that a de.

[0008]

According to the present invention having the above-described structure, when the one-phase coil magnetically coupled is switched to non-excitation, a current is generated in the other phase coils by mutual induction. Since this current is blocked by the diode connected after the first smoothing capacitor connection point of the electric circuit, it does not flow through the first smoothing capacitor,
It flows only into the second smoothing capacitor. That is, no current flows through the fuse due to the mutual induction action. Therefore, there is no need to estimate the capacitance value and the internal resistance of the first and second smoothing capacitors and their fluctuations, so that the optimum fuse can be selected easily and quickly.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, this drive circuit has the same basic configuration as that of the conventional example (FIG. 2), and has a diode D connected in series with the fuse 5 to prevent a mutual induction effect that occurs when the phase of the stepping motor 10 is switched. The configuration is such that a current i2 based on the current does not flow through the fuse 5. Further, in this embodiment, safety in handling when the drive power supply VH is turned off by connecting the discharge resistor R1 is ensured.

Therefore, the same or common parts as in the conventional example (FIG. 2) are denoted by the same reference numerals, and description thereof will be simplified or omitted.

The diode D is connected in series with the fuse 5 between the connection point T11 for the first smoothing capacitor C1 of the drive power supply VH side electric circuit 11 and the fuse 5. Therefore, for example, when the phase coil φA is turned off, the current i2 generated in the phase coil φC magnetically coupled to the phase coil φA flows only into the second smoothing capacitor C2. That is, since the current i2 is blocked by the diode D, it does not flow into the first smoothing capacitor C1. That is, it does not flow to the fuse 5.

Thus, the value of the current flowing through the fuse 5 is
It is determined by only the permissible load current flowing through the stepping motor 10 without being affected by the resistance value of the fuse 5 itself, the capacitance value and the internal resistance of the first and second smoothing capacitors C1 and C2, and the fluctuation due to the temperature change. I just need. Therefore, the optimum fuse 5 can be selected easily and quickly, and a necessary and sufficient protection action can be exhibited, and unnecessary drive stop due to selection of a small capacity can be prevented.

A connection point T for the second smoothing capacitor C2
In the electric circuit 12 between the motor 12 and the stepping motor 10, a discharge resistor R is provided between the connection point T13 and the ground G.
1 is connected. The resistor R1 discharges the electric charge charged in the second smoothing capacitor C2 to the ground G when the driving power supply VH is turned off. Fuse 5
Can be discharged even if is blown. Therefore, even if the capacity of the second smoothing capacitor C2 is larger than that of the conventional example, it is possible to safely handle the printed wiring board incorporating the present driving circuit (1, Q1 to Q4, etc.).

The diode D is a magnetically coupled one-phase coil (for example, φA) of the stepping motor 10.
Is turned off, the mutual induction current i2 generated in the other phase coil (φC) is prevented from flowing into the first smoothing capacitor C1, so that the connection position of the diode D is not limited to the above case. The present invention can also be implemented by connecting the fuse 5 in series between the fuse 5 in the coil side electric circuit 12 and the connection point T12 for the second smoothing capacitor C2.

[0015]

According to the present invention, the first electric circuit on the driving power supply side can be used.
By switching between one phase coil and the other phase coil of the stepping motor that are magnetically coupled between the connection point for the smoothing capacitor and the fuse or between the fuse on the phase coil side electric circuit and the connection point for the second smoothing capacitor. Since the diode is provided to prevent the current based on the mutual induction effect from flowing into the first smoothing capacitor, the optimum fuse can be selected easily and quickly, and the necessary and sufficient protection function can be guaranteed. Unnecessary drive stop due to mistake selection can be eliminated.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram for explaining a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electric circuit 11 drive electric circuit side electric circuit 12 phase coil side electric circuit T11, T12, T13 connection point 5 fuse 10 stepping motor 15 control circuit φA to φD phase coil Q1 to Q4 phase switching transistor Aph to Dph phase switching signal VH driving power supply G ground C1 First smoothing capacitor C2 Second smoothing capacitor D Diode R Discharge resistance

Claims (1)

(57) [Claims] 1. A protective fuse interposed in an electric circuit connecting a drive power supply and a phase coil of a stepping motor, and a first smoothing connected between an electric circuit on the drive power supply side centered on the fuse and ground. A driving circuit for a stepping motor having a capacitor and a second smoothing capacitor connected between the phase coil side electric circuit and the ground, between the first smoothing capacitor connection point of the driving power supply side electric circuit and the fuse or Between the fuse of the phase coil side circuit and the connection point for the second smoothing capacitor, a current based on a mutual induction action generated by switching between one phase coil and the other phase coil magnetically coupled of the stepping motor is generated. A driving circuit for a stepping motor, further comprising a diode for preventing the current from flowing into the first smoothing capacitor.