JPH01129797A - Step motor driving circuit - Google Patents

Abstract

PURPOSE:To minimize the size and cost of a step motor driving circuit and to simplify the construction by using a ROM for storing amplitude data of sine and cosine waves. CONSTITUTION:In a ROM 11, amplitude data for sine and cosine waves are stored. A counter 10 counts clock pulses, and alternately sine wave and cosine wave data are read out from the ROM 11 by use of the counter output as address data. Signal conversion circuits 12a, 12b comprises latches Ra, Rb and D/A converters DAa, DAb and latches amplitude data of sine and cosine waves alternately read out from the ROM 11 on the basis of the clock pulses to convert them into analog voltages. The exciting currents for each stator coil are controlled on the basis of the output of the signal conversion circuits 12a and 12b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a step motor drive circuit that drives a step motor in microsteps.

[Background Art] Figure 4 shows a schematic diagram of a four-phase step motor. It is formed by two intermediate tapped coils 2 and 3 that rotationally drive a permanent magnet rotor 1, and both coils 2 and 3 form A-phase to D-phase stator coils.

The tJSs diagram is an operating waveform diagram showing the excitation method of the step motor, and in this 4-phase step motor,
The permanent magnet rotor 1 is rotated by energizing each person's cheetah coil in the order of A phase → B phase → C phase → D phase. However, FIG. 5 shows that the stator coil is energized when the drive signal is at H level. The rotation angle of one step of such a standard step motor is usually 1.8°, 3.6°, etc., but according to the principle shown below, this one step can be rotated by n.
(n is an integer of 2 or more) and can be driven. In other words, Fig. 6(a) shows the principle of driving by dividing the basic step angle into n parts, and I^~ID are the vectors of the currents flowing in the A phase~D phase, respectively. It shows. Now, considering the case where the basic step angle between A phase and B phase is divided into n parts, each current I of adjacent A phase and B phase: I sin θ, I
As B = I cos θ (where θ = 90 to 0°),
It can be seen that it is sufficient to divide the value of θ into n equal parts. Figure 6(b)
shows the waveforms of the excitation currents ^~■D when such an excitation method is used. However, the waveforms of the sine wave and cosine wave are actually staircase waves for each division step, as shown in FIG. In such an excitation method, mode DA,
AB.

..., etc. are the D phase, A phase, and A phase, respectively.
This shows that the phase and B phase, etc. are excited at the same time. Further, in FIG. 6(b), the square wave driving waveform is shown for the case where driving is performed for each basic step angle.

Next, Fig. 8 schematically shows the deterioration of a conventional two-phase step motor, in which the A and B phase stator coils are formed by coils 2.3, and each stator coil is excited to have both positive and negative polarities. It has become. FIG. 9 shows the excitation method. First, the A-phase and B-phase stator coils are alternately excited positively, and then alternately excited negatively to rotate the permanent magnet rotor 1. I have to. Here, the basic rotation angle of one step of the permanent magnet rotor 1 is inversely proportional to the number of poles of the permanent magnet rotor 1, and in the case of 100 poles, it is 3.6.
In the case of 200 poles, the angle is 1.8°, but microstep driving is possible in which the basic step angle is divided into n. Fig. 10 shows the principle, and Fig. 10 (a) shows the excitation current machine ^, 1. The vector diagram (b) is a diagram showing changes in the respective excitation currents I^ and I8. As is clear from the vector diagram in FIG. 10 (,), there is a relationship between the A-phase and B-phase currents 6 and 8 as shown in the following equation: 2A2+I, n2=2. That is, I A: I sinθ, I B= r
If cos θ is a value obtained by dividing θ into n, the permanent magnet rotor 1 can be rotationally driven in microsteps that are 1/n of the basic step angle. In addition, Fig. 10 (b
) is a waveform when the permanent magnet rotor 1 is rotated by a square wave at a basic step angle.

By the way, when performing microstep driving as described above, I: r sin θ, r B = I
In order to generate an excitation current such as cos θ, for example, a sine wave oscillation circuit and a cosine wave oscillation circuit whose oscillation phases are different by 90 degrees are provided, and the oscillation output is microstepped. This method is not suitable for applications where the step motor is stopped midway through the basic step angle. Therefore, there is a device in which amplitude data of sine waves and cosine waves for microstep driving is stored in a ROM. That is, as shown in FIG. 11, a counter 10 that counts clock pulses CP, a first ROM 11a that stores sine wave amplitude data, a second ROM 11b that stores cosine wave amplitude data, and a counter 10 that counts clock pulses CP. D/A that converts the amplitude data read from each ROM11a+11b into an analog signal with output as 7 dress data
Signal converters 12a and 12b each include a converter, and excitation current control units 13a and 13b each include a power amplifier that controls an excitation current based on the output of the signal converters 12a' and 12b.
The signal converter 12a' sequentially reads amplitude data of sine waves and cosine waves from the first and second ROMs 11a and 1lb according to the clock pulse CP.

12b1 performs D/A conversion, and excitation current control section 13a.

13b amplifies the power and causes a predetermined excitation current to flow through the stator coils 2 and 3.

However, in the above-mentioned conventional example, separate ROMs were provided to store the amplitude data of the sine wave and cosine wave, so the circuit configuration became complicated and there was a problem that miniaturization and cost reduction could not be achieved. there were.

[Object of the Invention] The present invention has been made in view of the above points, and its object is to form a storage means for amplitude data of sine waves and cosine waves using one ROM, Easy to configure;
An object of the present invention is to provide a step motor drive circuit that can be made smaller and lower in cost.

[Disclosure of the Invention] (Structure) The present invention comprises a permanent magnet rotor in which N poles and S poles are alternately magnetized at equal angular intervals in the circumferential direction, and two or more stators that rotationally drive the permanent magnet rotor. In a step motor drive circuit that drives a step motor formed by a coil in microsteps by dividing the basic step angle into n pieces,
A counter that counts black and black pulses, a ROM in which data is read out using the counter output as address data and each amplitude data of a sine wave and a cosine wave is stored alternately in memory addresses, and a ROM that counts clock pulses from the ROM. The first and second latches the amplitude data of the sine wave and cosine wave that are read out alternately and converts them into analog voltages.
The signal conversion section and the excitation current control section that controls the excitation current of each stator coil based on the output of each signal conversion section are 3%
L, sine wave, cosine wave amplitude data storage means is one R.
The present invention provides a step motor drive circuit that can be formed using OM, is simple in construction, and can be made smaller and lower in cost.

(Embodiment) Fig. 1 shows an embodiment of the present invention, in which a permanent magnet a-ta 1 is magnetized with N poles and S poles alternately magnetized at equal angular intervals in the circumferential direction.
and two or more stator coils (in the example, A-phase and B-phase coils) that rotationally drive the permanent magnet rotor 1. A step motor is formed by dividing the basic step angle into n parts. In a step motor drive circuit similar to the conventional example that performs step drive, data is read out using a counter 10 that counts clock pulses CP and outputs a0 to a5 of the counter 10 as address data, and each amplitude data of a sine wave and a cosine wave is stored in a memory. ROM 11 consisting of EPROM etc. which are stored alternately at addresses, and the above ROM
First and second signal converters 12m each latch each amplitude data of a sine wave and a cosine wave alternately read out from II based on a clock pulse CP and convert it into an analog voltage.
, 12b, and excitation current control sections 13a and 13b that control the excitation current of each stator coil based on the output of each signal conversion section 12a and 12b. In the example,
The signal converters 12a and 12b each have a latch Ra.

Rb and D/A:y inverters DAa and DAb, and the data latch signal V r = V r'
is the first stage output signal a0 of the counter 10 and the inverter ■
This is an inverted signal based on 1.

Now, in the present invention, as shown in FIG. 2, the amplitude data of the sine wave is stored in the even numbered addresses 0 to 2 (n-1) in the memory address of the ROMII that stores the amplitude data of the sine wave and the cosine wave. Data Dso to Dsn-1 are stored at odd addresses 1-2n-
1 stores cosine wave amplitude data Dco-Dcn+, and as shown in FIG.
s2, ...... and cosine wave amplitude data D cos
De+sr)62%... are read out alternately, and this read data Dr is the data latch signal Vr.
.

Latch R when Vr' rises or falls
a, held in Rh. The data D rag D rb held in the latches Ra and Rb are sine wave amplitude data Dso, D s 1, ..., cosine wave amplitude data D eQ, De+, ...・It is,
By D/A converting this data by D/A converters DAa and DAb, respectively, analog sine wave signals and cosine wave signals are output from signal converters 12a and 12b.

As described above, in the present invention, one ROM 11 forms the storage means for amplitude data of sine waves and cosine waves, and the storage means is formed independently by two ROMs 11a and 11b. This makes it possible to realize a step motor drive circuit that can be simplified in configuration, smaller in size, and lower in cost than the conventional example. In the embodiment, the latches Ra and Rh and the D/A:7 inverters DAa and DAb are shown as separate parts, but D/A converters with built-in latches are commercially available, so if you use them, The number of parts does not increase, and costs can be reduced. Further, it goes without saying that if a converter IC in which two D/A converters are integrated into one chip is used, the structure can be further simplified and miniaturized.

[Effects of the Invention] As described above, the present invention provides N poles and S poles at equal angular intervals in the circumferential direction.
A step motor formed of a permanent magnet rotor whose poles are alternately magnetized and two or more stator coils that rotationally drive the permanent magnet rotor is driven in microsteps by dividing the basic step angle into n pieces. In the step motor drive circuit, a counter that counts clock pulses, a ROM in which data is read out using the counter output as 7 dress data and each amplitude data of a sine wave and a cosine wave are stored alternately in memory addresses; A first and a second signal converter each latch each amplitude data of a sine wave and a cosine wave alternately read out based on a clock pulse from a clock pulse and convert it into an analog voltage, and It is equipped with an excitation current control section that controls the excitation current of the cheetah coil, and the storage means for the amplitude data of the sine wave and cosine wave can be formed using one ROM, and the configuration is simple, compact, and low-cost. This has the effect of reducing costs.

[Brief explanation of the drawing]

j! Figure l'k1 is a block circuit diagram of one embodiment of the present invention, Figures 2 and 3 are explanatory diagrams of the same operation as above, Figure 4 is a schematic diagram of a four-phase step motor, and Figures 5 to 7. 8 is a schematic diagram of the two-phase step motor, FIGS. 9 and 10 are diagrams explaining the operation, and FIG. 11 is a block circuit diagram of a conventional example. 1 is a permanent magnet rotor, 2.3 is a coil, 10 is a kafunta, 11 is a ROM, 12a, 12bli-signal conversion section, and 13a, 13b are excitation current control sections. Agent Patent Attorney Ishi 1) Ai 7 Figure 4 Figure 5 Figure 10 Figure 11 Figure 1 it)

Claims (1)

[Claims] (1) A step motor formed of a permanent magnet rotor having N and S poles alternately magnetized at equal angular intervals in the circumferential direction, and two or more stator coils that rotationally drive the permanent magnet rotor, In a step motor drive circuit that divides the basic step angle into n parts and drives in microsteps, the data is read out using a counter that counts clock pulses and the counter output as address data, and each amplitude data of sine wave and cosine wave is stored in memory. First and second signal conversions that respectively latch the amplitude data of the sine wave and cosine wave alternately stored in the ROM at addresses and the amplitude data of the sine wave and cosine wave that are read out alternately from the ROM based on clock pulses and convert them into analog voltages. What is claimed is: 1. A step motor drive circuit comprising: an excitation current control section that controls an excitation current of each stator coil based on the output of each signal conversion section.