JPH04355698A - Stepping motor drive circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor drive circuit, and, for example, to a drive system for a step motor used for positioning a magnetic disk or the like.

0002

2. Description of the Related Art FIGS. 6 and 8 are diagrams showing the windings and drive circuit of a conventional step motor, as shown in, for example, "All About Floppy Disk Devices" by Shoji Takahashi, published by CQ Publishing, page 82. FIG. 6 schematically depicts monofilar winding and bipolar drive system, and FIG. 8 schematically depicts bifilar winding and unipolar drive system. Figure 7 shows one phase of the excitation coil of the bipolar drive system in Figure 6.
Figure 9 shows one phase of the excitation coil of the unipolar drive system in Figure 8. In the figure, 1 is the excitation coil, 2 and 3 are switch elements connected to the ground side, and 4 and 5 are connected to the positive power supply side. are connected switch elements.

Next, the operation will be explained. In the bipolar drive shown in FIG. 7, the switch element 4 connected to the positive power supply side and the switch element 3 connected to the ground side are turned on simultaneously, and at this time, the switch element 5 connected to the positive power supply side and the switch element 3 connected to the ground side are turned on. When the switch element 2 is off, current flows from the X side to the Y side of the exciting coil 1. This time is temporarily called a positive current, and a magnetic field is generated so that the X side becomes the S pole and the Y side becomes the N pole. Conversely, the switch element 4 connected to the positive power supply side and the switch element 3 connected to the ground side
When the switch element 5 connected to the positive power supply side and the switch element 2 connected to the ground side are turned on at this time, current flows from the Y side to the X side of the exciting coil 1. At this time, a negative current flows through the exciting coil 1, and a magnetic field is generated such that the X side becomes the north pole and the Y side becomes the south pole. Two sets of these drive circuits are arranged and connected as shown in Figure 7, and the currents flowing through the excitation coils A and B are first positive and then positive. Next, positive and negative. Then negative, negative. Furthermore, negative and positive. The step motor moves and rotates by switching sequentially. This combination of monofilar winding and bipolar drive system has high excitation coil utilization efficiency and is applied to small, high-output motors.

Next, the unipolar drive system will be explained using FIG. 9. In the figure, when switch element 3 is turned on and switch element 2 is turned off, the current flows through the exciting coil 1
flows through b. At this time, the N pole is on the Y side of the excitation coil 1,
X of excitation coil 1 wound around the same magnetic core (not shown)
A magnetic field is generated on the side so that it becomes the south pole. Conversely, when the switch element 3 is turned off and the switch element 2 is turned on, the current flows through the exciting coil 1a. At this time, a magnetic field is generated such that the N pole is on the X side of the exciting coil 1 and the S pole is on the Y side of the exciting coil 1 wound around the same magnetic core (not shown). The step motor can be moved and rotated by arranging two sets of these drive circuits and connecting them as shown in FIG. 8, and sequentially switching the currents flowing through the excitation coils A1, A2 and B1, B2. This combination of bifilar winding and unipolar drive system has a simple drive circuit and can be expected to reduce costs.

[0005]

[Problems to be Solved by the Invention] Since the conventional stitch motor drive circuit is configured as described above, for example, when attempting to move or rotate at high speed in bipolar drive, the current switching of the excitation coil must be done at high speed. must be switched to. However, due to the inductance component of the excitation coil, the current cannot be switched quickly. FIG. 10 is a diagram showing measurements of current changes during current switching when using a certain step motor. In the figure, (a) shows when the power supply voltage is in the normal operating state, and the current changes slowly. In order to solve this problem, the power supply voltage is doubled to the normal value (b), and the current changes quickly. However, it is not preferable to use twice the voltage for the device due to specifications. On the other hand, since the combination of monofilar winding and unipolar drive method uses half of the excitation coils, the inductance is about one-fourth of that when all the coils are used, so the current changes quickly. Therefore, it is advantageous for high-speed movement and rotation. but,
Since the coils used to drive the motor are divided into halves, the output cannot be obtained considering the coil space. For this reason, there was a problem in that the damping performance of vibrations when stopping after driving was also somewhat poor.

[0006] This invention was made to solve the above-mentioned problems.
The object of the present invention is to provide a motor that can rotate, and that can suppress vibration damping properties and power supply voltage within normal ranges when stopped after driving.

[0007]

[Means for Solving the Problems] A step motor drive circuit according to a first aspect of the invention has the following elements. (a) An excitation coil that generates a magnetic field with current to drive a step motor; (b) a bipolar drive circuit that causes current to flow from one side of the excitation coil to the other, or from the other side to the other; (c) the above. A unipolar drive circuit that has a part that is shared with a bipolar drive circuit and that allows current to flow from the middle part of the excitation coil to one side of the excitation coil or to the other side of the excitation coil. (d) A control circuit that switches between the bipolar drive circuit and the unipolar drive circuit.

The step motor drive circuit according to the second invention has the following elements. (a) An excitation coil that generates a magnetic field to drive a step motor, (b
) The first step is to apply current to the excitation coil to generate a magnetic field.
(c) the first power source from both sides of the excitation coil;
and (d) a switch element connected from the intermediate portion of the excitation coil to the first or second power source.

[0009]

[Operation] The step motor drive circuit according to the first invention has both a bipolar drive circuit and a unipolar drive circuit, and the control circuit is used when the step motor is stopped or driven at low speed and a large output is required. When the step motor is driven at high speed and the current changes quickly, the control selects the bipolar drive circuit, and selects the unipolar drive circuit when the step motor is driven at high speed and the current changes quickly. It is possible to obtain vibration damping properties and voltage within normal ranges.

Further, the step motor drive circuit according to the second invention connects two sets of four switch elements each connected to both ends of the excitation coil and two power supplies, and further connects the intermediate tap of the excitation coil to one of the switch elements. The power supply is connected with another switch element, and by switching these switch elements, current flows through the entire excitation coil or through parts, so it is useful when the current changes quickly or when a large output is desired. , can respond flexibly to operating conditions.

[0011]

[Example] Example 1. FIG. 1 is a diagram showing an embodiment in which the present invention is applied to a two-phase step motor.
7(c) is a diagram showing the control operation of the control circuit 10. FIG. A detailed explanation will be given below with reference to this figure.

In the figure, an exciting coil 1 is a switch element 2.
, 3 is grounded (an example of a second power source) 12, and connected to a positive power source (an example of a first power source) 11 through switch elements 4 and 5, and is further connected to the intermediate tap of the excitation coil 1. CT is connected to a positive power source 11 through a switch element 6.

First, when the step motor is driven at a low speed or when it is stopped, a large output is generally required of the step motor. In this case, the control circuit 10 turns off the switch element 6, thereby enabling operation similar to conventional bipolar drive.

That is, as shown in (c), the switch element 4 connected to the positive power supply side and the switch element 3 connected to the ground side are turned on at the same time, and at this time, the switch element 4 connected to the positive power supply side turns on. When the switch element 2 connected to the excitation coil 5 and the ground side is off, current flows from the X side to the Y side of the exciting coil 1. This time is temporarily called a positive current, and the X side is S
Assume that a magnetic field is generated so that the Y side becomes the north pole.

Conversely, the switch element 4 connected to the positive power supply side and the switch element 3 connected to the ground side are turned off, and at this time, the switch element 5 connected to the positive power supply side and the switch element 3 connected to the ground side are turned off. When the switch element 2 is turned on, current flows from the Y side to the X side of the exciting coil 1. At this time, a negative current flows through the exciting coil 1, and a magnetic field is generated such that the X side becomes the north pole and the Y side becomes the south pole.

Two sets of these drive circuits are arranged and connected as shown in FIG. 1(a), and the currents that the control circuit 10 sends to the excitation coils 1 and 7 are first set as positive and positive. Next, positive and negative. Then negative, negative. Furthermore, negative and positive. The step motor moves and rotates by switching sequentially.

Next, move the step motor at high speed,
When you want to rotate a step motor, you generally need a force that is smaller than when it is stopped, but can change at high speed. In this case, the control circuit 10 turns on the switch element 6 and turns off the switch elements 4 and 5, thereby making it possible to perform the same operation as the conventional unipolar drive.

That is, when the switch element 3 is turned on and the switch element 2 is turned off in FIG. 1(b), current flows through the exciting coil 1b. At this time, a magnetic field is generated such that the N pole is on the Y side of the exciting coil 1 and the S pole is on the X side of the exciting coil 1 wound around the same magnetic core (not shown). Conversely, when the switch element 3 is turned off and the switch element 2 is turned on, the current flows through the exciting coil 1a. At this time, a magnetic field is generated such that the N pole is on the X side of the exciting coil 1 and the S pole is on the Y side of the exciting coil 1 wound around the same magnetic core (not shown).

As described above, in the present invention, the drive system is switched between bipolar drive at low speed drive and unipolar drive at high speed drive depending on the drive speed of the step motor.The reason for this is explained below using FIG. explain. FIG. 5 is a graph showing the current flowing through the drive coil and the magnetic field generated in the drive coil when the drive coil is driven from time t=0 using a current source with voltage control. The solid line corresponds to bipolar drive when all the drive coils are used, and the broken line corresponds to unipolar drive when half of the drive coils are used. The inductance L of the coil is proportional to the square of the number of turns N, and the generated magnetic field Φ is proportional to the product of the number of turns N and the current I. Also, the current I is the resistance R of the coil
The time constant given by the ratio of L and inductance L, L/
Using R, it is proportional to the base e of the natural logarithm raised to the power -Lt/R. From these relationships, the relationship between time and the generated magnetic field was determined and illustrated in FIG. 5. As is clear from the figure, the current rises faster when half the coil is used.
The magnetic field also rises quickly. This shows that in a region where time t is small, the generated magnetic field is stronger when half of the drive coils are used than when all of the drive coils are used. On the other hand, as time t elapses, the generated magnetic field becomes stronger when all the drive coils are used. Therefore, when driving at low speeds, i.e., when the current changes slowly, bipolar driving, which uses all the drive coils, is advantageous, and when driving at high speeds, i.e.,
It can be seen that unipolar drive, which uses half of the drive coils, is suitable when the current changes quickly.

Example 2. In the above embodiment, the intermediate tap CT of the excitation coil 1 is connected to the positive power supply using the switch element 6, but it may be grounded using the switch element 6 as shown in FIG. 2. In this case, the switch element 6 As mentioned above, bipolar drive can be achieved by turning off the . In the case of unipolar drive, in this embodiment, the switch element 6 can be turned on and the switch elements 2 and 3 turned off, and the switch elements 4 and 5 can be turned on and off.

Example 3. Furthermore, in the first embodiment, the switch elements 2, 3 and 4
, 5, and 6 are connected to the ground and the positive power source, but each is connected to a current source (an example of a second power source) as shown in Figures 3(a) and (b).
It may be connected to the power supply via 8 or resistor 9.

Example 4. Further, in the first embodiment, a case is shown in which there is one intermediate tap CT, but as shown in FIG. 4, a plurality of intermediate taps may be provided. In the figure, CT1 and CT2 are excitation coil 1
It is an intermediate tap located at a position that divides the
and 6b are switch elements that connect the respective intermediate taps CT1 and CT2 to the power supply 11. Switch element 6a
If switch elements 2, 4, 5, and 6b are turned off, bipolar drive is possible as described in Example 1, and switching elements 2, 4, 5, and 6b are turned off.
When the switch elements 3 and 6a are turned off and the switch elements 3 and 6a are turned on, the right two-thirds portions 1b and 1c of the excitation coil are used. Furthermore, when the switch elements 3, 4, 5, and 6a are turned off and the switch elements 2 and 6b are turned on, the left two-thirds portions 1a and 1b of the excitation coil are used. Alternatively, although not described in detail, depending on the settings of the switch elements, it is also possible to use only the left-hand third portion 1a of the excitation coil, and it is also possible to use only the right-hand third portion 1c.

Example 5. Further, although only a two-phase motor was described in the above embodiment, the step motor may be a three-phase motor.

Example 6. Further, in the above embodiments, a transistor is used as an example of a switching element, but a semiconductor switching element such as a thyristor or a triac may also be used.

As described above, in the above embodiment, in a step motor having a plurality of excitation coils, each of the excitation coils is provided with one or more intermediate taps, and both ends of the excitation coil are connected to a first power source, a first power source, and a second power source. The step motor drive method is characterized in that two sets of four switch elements connected to two power sources are connected, and the switch element connected to the first or second power source is connected to the intermediate tap. explained. Note that the first or second power source may be any type of power source as long as it is connected to the whole or a part of the excitation coil and allows current to flow through the whole or a part of the excitation coil.

The circuit used in this method turns on the switch element connected to the intermediate tap of the excitation coil depending on the operating conditions of the step motor, and turns on the switch element connected to the intermediate tap of the excitation coil. Turn off two switch elements connected to the power supply connected to the switch element connected to the intermediate tap, and turn off the switch element connected to the intermediate tap among the switch elements connected to both ends of the excitation coil. The first operation mode (bipolar drive) alternately turns on and off two switch elements connected to a power supply different from the power supply connected to the power supply, and the first operation mode (bipolar drive) turns off the switch element connected to the intermediate tap of the excitation coil. , a first switch element connected to one end of the excitation coil and a first power supply, and a second switch element connected to the other end of the excitation coil and a second power supply as a first pair; A third switch element connected to one end of the excitation coil and a second power supply, and a fourth switch element connected to the other end of the excitation coil and the first power supply as a second pair, This step motor drive circuit is characterized in that it switches between a second operation mode (unipolar drive) in which the pair of switch elements and the second pair of switch elements are alternately turned on and off.

As described above, in the step motor, the excitation coil 1 is provided with the intermediate tap CT, the intermediate tap CT and the power source are connected through the switch element 6, and the switch element 6 is turned off when stopping or driving at low speed. Driving similar to bipolar driving can be performed in this manner, and when high-speed driving is desired, driving similar to unipolar driving can be performed by turning on the switch element 6. As a result, the output is large in the stopped or low speed region, and higher speed driving is also possible.

[0028]

[Effects of the Invention] As described above, according to the present invention, a drive circuit that is powerful at low speeds and capable of moving and rotating at high speeds can be realized using the power supply voltage that has been conventionally used. .

[Brief explanation of drawings]

FIG. 1 is a diagram of a step motor drive system according to an embodiment of the present invention, a circuit connection diagram of an excitation coil, and an operation diagram of a control circuit.

FIG. 2 is a circuit connection diagram for one phase of an exciting coil driven by a step motor according to another embodiment of the present invention.

FIG. 3 is a circuit connection diagram for one phase of an exciting coil driven by a step motor according to another embodiment of the present invention.

FIG. 4 is a circuit connection diagram for one phase of an exciting coil driven by a step motor according to another embodiment of the present invention.

FIG. 5 is a diagram showing a conventional step motor drive method (bipolar drive).

FIG. 6 is a diagram for explaining the principle of the invention.

FIG. 7 is a circuit connection diagram for one phase of an excitation coil in a conventional step motor drive method (bipolar drive).

FIG. 8 is a diagram showing a conventional step motor drive method (unipolar drive).

FIG. 9 is a circuit connection diagram for one phase of an excitation coil in a conventional step motor drive method (unipolar drive).

FIG. 10 is a diagram showing current changes in an excitation coil in a conventional step motor drive method (bipolar drive).

[Explanation of symbols]

1 Excitation coil 2 Switch element 3 Switch element 4 Switch element 5 Switch element 6 Switch element 7 Excitation coil 8 Current source (an example of a second power supply) 9 Resistance 10 Control circuit 11 Positive power supply (an example of the first power supply) 12 Grounding (an example of second power supply)

Claims (2)

[Claims] Claim 1. A stepper motor drive circuit having the following elements: (a) an excitation coil that generates a magnetic field to drive the stepper motor; (b) from one side of the excitation coil to the other, or from the other side to the other side; (c) a unipolar drive circuit that has a part shared with the bipolar drive circuit described above and that causes current to flow from the middle part of the excitation coil to either side of the excitation coil; (d) A control circuit that switches between the bipolar drive circuit and the unipolar drive circuit. 2. A step motor drive circuit having the following elements: (a) an excitation coil that generates a magnetic field to drive the step motor; (b) a first power source that supplies current to the excitation coil to generate the magnetic field; second power source, (c)
(d) two pairs of switch elements connected to the first and second power sources from both sides of the excitation coil; (d) a switch element connected to the first or second power source from the intermediate portion of the excitation coil;