JPH10201294A - Driving circuit for three-phase step motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive circuit which is inexpensive and little in vibration and noise by detecting the timing of two-phase excitation and three-phase excitation from the drive pulses of external input, and changing the duty of a PWM circuit so as to let a total current flow a little at two-phase excitation and much at three-phase excitation. SOLUTION: A timing logic circuit 2 detects the timing of the two-phase excitation and three-phase excitation of a three-phase excitation winding 5 from the input of a drive pulse generating circuit 1, and outputs a signal, and an electronic switch 12 operates with the output signal of the timing logic circuit 2 and the reference voltage of a reference voltage generating circuit 11d. A PWM circuit 7 varies the total current with the output signal of the electronic switch 12 and the signal of the current detector 6 for detecting the total sum of a drive current, and a current application control means 7a within the PWM circuit 7 changes the pulse width so as to let the total current flow a little at two-phase excitation and much at three-phase excitation. Then, a base drive circuit 3 drives an inverter circuit 4 with the output signal of the PWM circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a three-phase step motor for controlling the drive of a motor having a stator having three-phase excitation windings connected in a star shape and a rotor having permanent magnets. It is.

[0002]

2. Description of the Related Art Conventionally, a permanent magnet type three-phase stator comprising a stator having a star-connected three-phase excitation winding and a rotor including a permanent magnet and facing the stator with a predetermined gap. In the case of controlling the drive current flowing through the excitation winding to a desired current value in the stepping motor, a bridge-connected main circuit is formed so that a bidirectional current can flow in each phase, and the bridge circuit is switched by performing a switching operation. The value of the current flowing through the exciting winding is controlled. The current control method is to detect the total current flowing through the exciting winding using a resistor or the like, compare the detected current with a current command value, and perform pulse width control (hereinafter abbreviated as PWM) using a pulse signal based on the comparison result. Constant current control is being performed. By using the PWM method, the loss of the switch element of the inverter circuit is reduced, and the element is also downsized.
In addition, the constant current control reduces a change in the motor torque with respect to a change in the environmental temperature or a change in the temperature due to self-heating.

FIG. 3 is an example of a drive circuit configuration diagram of a conventional three-phase step motor. As shown in the figure, 5 is U phase, V
A three-phase excitation winding in which the phase and W phase windings are connected in a star shape. The rotor is provided with permanent magnets, and the relationship between the pole teeth of the stator and the pole teeth of the rotor is configured in an optimal manner. The detailed description is given in
-269458.

Further, Vcc is a driving power supply, 1 is a driving pulse generating circuit, 14 is a logic circuit for specifying the order of energizing the U, V, and W phases, and 4 is an inverter composed of a switching element and a circulating element of each phase. Circuit. The inverter circuit 4 energizes the three-phase excitation winding 5 according to the determined logic signal. Reference numeral 6 denotes a current detector including a resistor provided for detecting the sum of drive currents flowing through each phase of the three-phase excitation winding 5, a resistor and a capacitor constituting a filter. The drive current detected by the current detector 6 is converted to a voltage signal and
It is input to the M circuit 7. The PWM circuit 7 includes an error amplification circuit, an oscillation circuit, a sawtooth wave generation circuit, and a comparison circuit. The input drive current voltage signal is matched with the voltage of the reference voltage generator 13. The resulting difference voltage is input to the comparison circuit, and the level is compared with the sawtooth carrier signal to generate a pulse signal having a pulse width corresponding to the level of the difference voltage. The pulse signal outputs a base signal suitable for driving the switch element of each phase upper arm by the base drive circuit 3, and the base signal controls ON / OFF of each phase switch element at the carrier frequency of the PWM circuit 7. Is performed. As a result, a drive current corresponding to the pulse width of the pulse signal is supplied to the U, V, and W phase windings of the three-phase excitation winding 5.

FIG. 4 is a timing chart showing signal waveforms at various parts in FIG. (A) is a drive pulse generation circuit 1
(B) to (g) are outputs of the logic circuit 14 and are energizing logics for the U, V, and W phases. Signals corresponding to the six transistors of the inverter circuit 4 are u and d, respectively. The upper arm and lower arm of the phase are shown.
(H) to (j) are current waveforms applied to the U, V, and W phases, which are bipolar currents flowing in the positive and negative directions. The carrier frequency of the PWM circuit 7 is 40 kHz.
The ripple of the PWM circuit 7 does not appear in the current waveform. The total current, which is the sum of the currents of the U, V, and W phases, is (k)
As shown in the figure, since the current is controlled so as to be constant at (1.0), the current level of each phase is (0.5), (1.0), (0) depending on the energizing section (h). Change. The energized section ~ shows the state of each drive step,
It can be seen that is in a two-phase excitation state and is in a three-phase excitation state. Such an excitation system combining the two-phase excitation and the three-phase excitation is called a 2-3-phase excitation system.

FIG. 8 is a diagram showing the torque generated in each energizing section as a vector. As shown in the figure, the bold arrows indicate the 120 generated in the U, V, and W phases in the energized section of.
It is the sum of the torque vectors that are out of phase by degrees, and the numbers (0.5), (1.0), (1.5), and (1.73) in the figure indicate the magnitude of the torque vector. . For example, 3
In the case of the phase excitation conduction section, the sum of the torque vectors is U phase (0.5, ∠0) and V phase (1.
0, ∠2π / 3) and (1.5, ∠5π / 3) from the W phase (0.5, ∠4π / 3). Similarly, in the energizing section of the two-phase excitation, the U phase (1.0, $ 0) and the V phase (1.
0, ∠2π / 3), W phase (0) to (1.73, ∠11
π / 6). This shows that the torque vector is larger during two-phase excitation than during three-phase excitation. In the configuration of the constant current control circuit as described above, the magnitude of the torque vector varies depending on the energizing section, and the rotational torque becomes non-uniform.

[0007]

However, such a 3
In a drive circuit of a phase step motor, vibration and noise increase due to non-uniformity of rotation torque. In order to solve this problem, a circuit such as a micro step drive has been proposed. However, the circuit configuration is often complicated and expensive, and a simple and inexpensive circuit configuration is used to realize a PWM drive circuit with reduced vibration and noise. Is desired.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide a drive circuit for a three-phase step motor which is inexpensive and has little vibration and noise.

[0009]

According to the present invention, there is provided a timing logic circuit for detecting two-phase excitation and three-phase excitation timing from a driving pulse of an external input, and an output of the timing logic circuit. PWM for variably controlling the total current to the three-phase excitation winding by a signal
A circuit and energization control means for changing the pulse width of the PWM circuit so as to reduce the total current during two-phase excitation and increase the total current during three-phase excitation are provided.

The pulse width of the driving pulse is 5 to 2
A reduction pulse generating circuit is provided for reducing the total current to the exciting winding to about の み only in the initial section every time the drive pulse arrives in the initial section of 0%.

[0011]

FIG. 2 is a diagram showing an embodiment of a drive circuit for a three-phase step motor according to the present invention. As shown in the figure, a timing logic circuit 2 for detecting the timing of two-phase excitation and three-phase excitation of a three-phase excitation winding 5 from an input of a drive pulse generation circuit 1 and outputting a signal, and an output of the timing logic circuit 2 A PWM circuit that variably controls the total current based on a signal and a signal from an electronic switch 12 that operates with a reference voltage from a reference voltage generator 11 and a signal from an output signal of the electronic switch 12 and a current detector 6 that detects the sum of driving currents. 7
And an energization control means 7a provided in the PWM circuit 7 for changing the pulse width so as to reduce the total current during two-phase excitation and increase the total current during three-phase excitation, and the output signal of the PWM circuit 7 And a base drive circuit 3 for driving the inverter circuit 4. The electronic switch 12 switches the voltage value, which is the total current value command of the three-phase excitation winding 5, and
Input to the WM circuit 7. In other words, the current ratios (0.5) and (1.0) in the energizing section of the three-phase excitation are the same as in the past.
, And the current is applied at a current ratio of (0.87) in the energizing section of the two-phase excitation.

FIG. 5 is a timing chart showing the above operation. As shown in the figure, a current value command signal (b) is generated for each drive pulse (a), and the total current is a current ratio (0.87) at the time of two-phase excitation, and a current ratio (1.
0), the current control means 7a determines the current ratio of each phase of the three-phase excitation winding 5 to (0.5), (0.87), (1.0). The current is controlled (c), (d), and (e). The total current in each energizing section (g) is shown in (f).

FIG. 9 is a torque vector diagram when driven by the drive circuit of FIG. As shown in the figure, the vectors of each phase in the energization section are U-phase (0.5, ∠0) and V-phase (1.0,
∠2π / 3), the sum of the torque vectors in the W phase (0.5, ∠4π / 3) is (1.5, ∠5π / 3), and the vector of each phase is U phase (0.87 , ∠0), V phase (0.87, ∠2π / 3), and W phase (0), the sum of the torque vectors is (1.5, ∠11π / 6). Compared with FIG. 8 of the related art, it can be seen that the magnitudes of the generated torques of the two-phase excitation and the three-phase excitation match.

As described above, by controlling the total current of each phase to a set value by the PWM method, the torque vector generated for each drive pulse is controlled to a constant magnitude, and the motor operates at a high drive frequency. It operates stably until now, and vibration and noise are reduced.

Further, the configuration of the drive circuit of the present invention is extremely simplified, and can be manufactured at a small size and at a low cost.

FIG. 1 is a diagram showing another embodiment of a drive circuit for a three-phase step motor according to the present invention, which is a further improvement of FIG. As shown in the figure, reference numeral 10 denotes a reduction pulse generation circuit that generates a reduction pulse having a constant pulse width at the frequency of each drive pulse period. By turning it off, the reference voltage from the reference voltage generator 9, which is the total current command, is reduced to １ ／ and input to the PWM circuit 7.

FIG. 6 is a timing chart showing the above operation. As shown in the figure, a reduction pulse (c) having a constant width T is generated in synchronization with the drive pulse (a). This reduction pulse (c) has a frequency of 5 to 5
Since the pulse width is set to 20%, the driving pulse (a)
Automatically changes when the frequency changes, the pulse width ratio always becomes the same. In this way, the current of each phase is controlled by the current control means so that the current of each phase becomes で in the power supply section of 5 to 20% of the frequency for each drive pulse. The total current for each energizing section (h) is shown in (g).

FIG. 10 is a torque vector diagram when driven by the drive circuit of FIG. As shown in the figure, a thick broken arrow indicates a torque vector when the reduction pulse is generated. For example, at the time T of the energizing section, the sum of the torque vectors when the reduction pulse is generated is (0.25, ∠0) + (0.5, ∠2).
π / 3) + (0.25, {4π / 3) = (0.75, ∠
5π / 3), and after the time T, the sum of the torque vectors becomes twice (1.5, ∠5π / 3).

FIG. 7 shows the measured values of the U-phase current change and the motor vibration by the acceleration sensor during the energizing section.
(A) is based on the conventional energizing method shown in FIG. 4, and (b) is based on the energizing method using the present invention.
Occurrence of vibration overshoot,
It can be seen that undershoot and settling time have been greatly improved. Further, it is understood from experimental values that the width of the reduction pulse is 5 to 20% of the driving pulse period and the amount of reduction of the current value is 最 も which is most effective for vibration and noise.

As described above, in the drive circuit to which the reduction pulse is added, even if the drive pulse frequency greatly changes, the ratio of the reduction pulse width does not change, and vibration and noise are further reduced in a wide frequency range. It became possible to reduce.

[0021]

As described above, in the drive circuit of the three-phase step motor according to the present invention, the total current of each phase is controlled by the PWM method at a constant current, so that the torque vector generated for each drive pulse is obtained. Is controlled to a constant magnitude, so that the three-phase step motor operates stably up to a high driving frequency, and vibration and noise are reduced. In addition, the configuration of the driving circuit is very simplified, and it can be manufactured small and inexpensively.
It is also easy to implement and significant cost reduction is possible.

The driving pulse has a pulse width of 5 to 20%.
In the initial section, when a reduction pulse generation circuit is provided that reduces the total current to the exciting winding to about の み only in the initial section every time a drive pulse arrives, vibration and noise are further reduced over a wide frequency range. It became possible to do.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing another embodiment of a drive circuit for a three-phase step motor according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a drive circuit for a three-phase step motor according to the present invention.

FIG. 3 is a drive circuit configuration diagram of a conventional three-phase step motor.

FIG. 4 is an operation timing chart when driven by a conventional drive circuit of a three-phase step motor.

FIG. 5 is an operation timing chart of the drive circuit of FIG. 2;

FIG. 6 is an operation timing chart of the drive circuit of FIG. 1;

FIG. 7 is a diagram showing a change in phase current and a motor vibration characteristic in a certain energizing section.

FIG. 8 is a torque vector diagram when driven by a conventional three-phase step motor drive circuit.

FIG. 9 is a torque vector diagram when driven by the drive circuit of FIG. 2;

FIG. 10 is a torque vector diagram when driven by the drive circuit of FIG. 1;

[Explanation of symbols]

 1: drive pulse generation circuit 2: timing logic circuit 3: base drive circuit 4: inverter circuit 5: three-phase excitation winding 6: current detector 7: PWM circuit 7a: conduction control means 8: electronic switch 9: reference voltage generation Apparatus 10: Reduction pulse generation circuit 11: Reference voltage generation apparatus 12: Electronic switch 13: Reference voltage generation apparatus 14: Logic circuit

Claims (2)

[Claims] 1. A permanent magnet type three-phase stepping motor comprising a stator having a star-connected three-phase excitation winding and a rotor including a permanent magnet and facing the stator with a predetermined gap. Timing logic for detecting the timing of two-phase excitation and three-phase excitation from a driving pulse of an external input in a drive circuit of a three-phase step motor that drives and controls the three-phase excitation winding by bipolar conduction in a 2-3-phase excitation method Circuit and
A PWM circuit that variably controls the total current to the three-phase excitation winding based on an output signal of the timing logic circuit; and a PWM circuit that reduces the total current during two-phase excitation and increases the total current during three-phase excitation. A drive circuit for a three-phase step motor, comprising: an energization control unit that changes a duty of the motor. 2. A reduced pulse for reducing the total current to the exciting winding to about 1/2 only in the initial section every time the drive pulse arrives in an initial section in which the pulse width of the drive pulse is 5 to 20%. The drive circuit for a three-phase step motor according to claim 1, further comprising a generation circuit.