JPH0998598A - Drive circuit for stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need of high rate clock for designating the r.p.m. by detecting only the rising of clock for designating the r.p.m. based on an auxiliary mode setting signal and determining the r.p.m. of a stepping motor based on the detection results thereof and a mode setting signal thereby controlling the stepping motor. SOLUTION: Only the rising of a clock 'Clock' for designating r.p.m. or both the rising and falling thereof are detected, based on an auxiliary mode setting signal DBS and the r.p.m. of a stepping motor is determined at an exciting mode setting section 21 based on the detection results thereof and a plurality of mode setting signals Mode A, Mode B. Driving control of a stepping motor M is performed under control of exciting mode setting section 21. According to the drive circuit, high rate clock for designating the r.p.m. can be eliminated even when a high speed exciting mode is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor drive circuit, and more specifically, it is an object of the present invention to improve a drive circuit for microstep driving a three-phase excitation stepping motor used in a printer or a copying machine. In recent years, the demand for a three-phase excitation stepping motor has been increasing in the market because the drive circuit can be simplified compared to the five-phase excitation stepping motor and a drive with lower vibration than that of the two-phase excitation stepping motor can be realized. The improvement of the drive circuit is required.

[0002]

2. Description of the Related Art A drive circuit of a conventional three-phase excitation stepping motor will be described below with reference to the drawings. As shown in FIG. 10, the drive circuit includes a drive signal generation unit (1), a drive unit (2) and a CPU (3), and a control command (KS) output from the CPU (3),
It is a circuit that drives a microstepping stepping motor (M) of three-phase excitation based on a rotation speed designation clock (CK).

According to the above circuit, as shown in FIG. 10, a control command (KS) is input to the drive signal generator (1),
Any one of the two-phase, 2-3 phase, W2-3 phase, and 2W2-3 phase excitation modes is fixed. At the same time, in the drive signal generator (1), the interval between the rising edges is the rotation angle of the stepping motor (M) (in this case, 3.75).
The rotation speed designation clock (CK) corresponding to the (degree) is input.

The drive signal generation unit (1) detects only the rising time of the rotation speed designation clock (CK) corresponding to the selected excitation mode, and the drive unit (2) outputs the detected signal at each time.
A drive signal (DS) is generated to "rotate the motor (M) so as to engrave a microstep when the rising time is detected". The drive unit (2) rotates the stepping motor (M) based on the drive signal (DS) output from the drive signal generation unit (1) to drive the stepping motor (M).

[0005]

However, as shown in FIG.
According to the conventional drive circuit as shown in FIG. 2, the drive signal generation unit (1) drives the stepping motor (M) so that the microstep is always performed when the rising time of the rotation speed designation clock (CK) is detected. Is instructed to the drive unit (2), the number of rotations of the motor (M) is set to 4 by only a fixed excitation mode such as W2-3 phase.
To double the speed, specify a four times faster rotation speed designation clock (C
K) will be required.

Then, the CPU (3) which must generate the high-speed rotation speed designation clock (CK) in this way
There was a problem that it would be overloaded. Further, if the rotation speed designation clock (CK) is not set to an excessively high speed in order to avoid an excessive load on the CPU (3), there is a problem that the motor (M) cannot be driven at a high speed.

[0007]

The present invention has been made in view of the above-mentioned drawbacks of the prior art. As shown in FIG. 1, a mode setting signal for defining an excitation mode of a three-phase excitation stepping motor, and A rotation speed designation clock that regulates the rotation speed of the stepping motor, and a mode setting auxiliary signal that selects one of detection of only the rising edge of the rotation speed designation clock or detection of both rising and falling edges of the rotation speed designation clock. A circuit for controlling the drive of the stepping motor based on the above, based on the mode setting auxiliary signal, detects only the rising edge of the rotation speed designation clock or both the rising and falling edges of the rotation speed designation clock, An excitation motor that regulates the rotation speed of the stepping motor based on the detection result and the mode setting signal. A drive circuit for a stepping motor, which has a setting unit and a drive unit for controlling the drive of the stepping motor under the control of the excitation mode setting unit, and the excitation mode setting unit, When detecting both the rising edge and the falling edge, the stepping motor is rotated at twice the rotation speed as compared with the case where only the rising edge of the rotation speed designation clock is detected in the same mode. The stepping motor drive circuit and the excitation mode setting unit according to the present invention detect only the rising edge of the rotation speed designation clock when detecting both the rising edge and the falling edge of the rotation speed designation clock. It is characterized in that the stepping motor is driven at twice the number of rotations as compared with the case and an excitation mode in which the step is doubled is selected. By the stepping motor drive circuit according to the present invention, it is possible to provide a stepping motor drive circuit that enables high-speed micro-step drive while reducing an excessive load on the CPU without generating a high-speed clock in the CPU. To do.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A drive circuit for a stepping motor according to an embodiment of the present invention will be described below. As shown in FIG. 1, this drive circuit includes a time chart generator (2
1), the first and second PWM control units (22A, 22B),
First and second current detectors (23A, 23B), Vcc level shift circuit (24A), GND level shift circuit (24B), reference voltage generator (25), CR oscillator (26), reference clock generator A stepping motor (M) for three-phase excitation based on each signal output from a CPU (not shown).
This is a circuit for driving.

The time chart generation unit (21) is an example of an excitation mode setting unit, and an excitation mode setting signal (ModeA), an excitation mode setting signal (ModeB) and a double speed signal (DBS) input from a CPU (not shown). , Excitation mode based on various signals such as motor pause signal (Hold), rotation direction switching signal (CW / CCW), forced OFF signal (Enable), rotation speed designation clock (Clock), system reset signal (Reset) Is set, and a drive clock (PP) in which information such as the rotation speed and the rotation direction based on the excitation mode is fetched is generated and output to the PWM control units (22A, 22B). The details of these signals will be described later.

First and second PWM control units (22A, 22)
B), first and second current detectors (23A, 23B), V
The cc level shift circuit (24A), the GND level shift circuit (24B), the reference voltage generation unit (25), the CR oscillator (26), the reference clock generation unit (27), and the charge pump (28) are examples of drive units. Which controls the drive of the motor (M) based on the drive clock (PP) from the time chart generator (21).

The first PWM control section (22A) is a circuit for performing PWM (Pulse Width Modulation) modulation of the drive clock (PP) and outputting it to the switching transistors (F1, F2, F3) to drive them. Second PWM
The control unit (22B) is a circuit that PWM-modulates the drive clock (PP) and outputs it to the switching transistors (F4, F5, F6) to drive them.

The first current detection section (23A) is a circuit for detecting the current flowing through the switching transistors (F1, F2, F3) and outputting it to the PWM control section (22A). 23B) detects the current flowing through the switching transistors (F4, F5, F6) and detects P
This is a circuit for outputting to the WM control unit (22B). The reference voltage generator (25) is a circuit that generates a sinusoidal reference voltage required for the above current detection.

The Vcc level shift circuit (24A) is a circuit for converting the level of the reference voltage on the power supply voltage side generated by the reference voltage generation section (25) and outputting it to the first current detection section (23A). Level shift circuit for GND (24B)
Is a circuit that level-converts the reference voltage on the ground potential side generated by the reference voltage generation unit (25) and outputs the level-converted reference voltage to the second current detection unit (23B).

The CR oscillator (26) is an oscillator for generating a clock having a constant frequency, and includes a reference clock generating unit (2
7) is a circuit for generating a reference clock for the entire drive circuit from the clock generated by the CR oscillator (26).
The operation of the drive circuit will be described below. Here, driving when the excitation mode is the W2-3 phase will be described.

First, an excitation mode setting signal (ModeA, ModeB), a double speed signal (DBS), which is an example of a mode setting signal,
Motor pause signal (Hold), rotation direction switching signal (CW / C
CW), forced OFF signal (Enable), rotation speed designation clock (Clock), system reset signal (Reset), etc.
A drive clock (PP) is generated by a time chart generation unit (21) based on various signals input from a CPU (not shown).

This drive clock (PP) is PWM-modulated by the PWM control section (22A, 22B), and switching transistors (F1 to F) are generated according to the modulation pulse.
6) performs an ON / OFF operation, and a phase current as shown in the timing chart of FIG. 2 flows to the stepping motor (M), and the stepping motor (M) rotates at a predetermined rotation speed and rotation direction.

The U-phase, V-phase, and W-phase currents draw a rectangular wave or a pseudo sine wave, and the rotation speed of the motor changes depending on the cycle of these phase currents. When the cycle is halved, the number of rotations is doubled, and when the cycle is doubled, the number of rotations is ½.
Double. At this time, switching transistors (F1 to
The current flowing through F6), that is, the phase current flowing through the stepping motor (M) is the current detection circuit (23A, 23A).
It is always detected by B).

The reference voltage required for this current detection is generated by the reference voltage generator (25), and the stepwise reference voltage generated by the reference voltage generator (25) is the Vcc level shift circuit ( 24A), the level is converted by the GND level shift circuit (24B) and output to the current detection circuits (23A, 23B). The current detection result detected based on the reference voltage generated in this way is transferred from the current detection circuit (23A, 23B) to the PWM control unit (2).
2A, 22B) and P based on the detection result.
PWM modulation is performed by the WM control unit (22A, 22B), and the stepping motor (M) is driven.

Functions of signals such as the above-mentioned motor temporary stop signal (Hold), rotation direction switching signal (CW / CCW) and forced OFF signal (Enable) will be described below with reference to timing charts of FIGS. 3 to 5. To do. Forced OFF in Figure 3
The function of the signal (Enable) is shown. The forced OFF signal (Enable) is “1” during normal operation, but when switched to “0” as shown in FIG. 3, all the phase currents of the U, V, and W phases are forced to 0, and the switching transistor (F1
~ F6) are all turned off and the motor (M) is forcibly stopped.

FIG. 4 shows the function of the motor temporary stop signal (Hold). The motor temporary stop signal (Hold) is "1" during normal operation, but when this is switched to "0", the phase currents of the U, V, and W phases are at the time of switching as shown in FIG. Since the current value is kept constant,
The motor (M) is switched to the stopped state while the current is still flowing in the coil of the motor (M), and this is maintained.

FIG. 5 shows the function of the rotation direction switching signal (CW / CCW). When this signal is switched, the phases of the phase currents of the U, V, and W phases are all inverted at the time of switching, and the rotation direction of the motor (M) is reversed.
In the conventional drive circuit, the rotation speed of the motor depends on the rotation speed designation clock (Clock). Therefore, when driving in the excitation mode where a high rotation speed is required, the rotation speed designation clock (Clock) operates at high speed. However, in the drive circuit according to the present embodiment, the time chart generation unit (2) is generated by the excitation mode setting signals (ModeA, ModeB).
1) stipulates a total of four types of excitation modes of 2 phase to 2W2-3 phase. This point will be described below with reference to the timing charts of FIGS.

In FIG. 6, the excitation mode setting signals (ModeA, Mod
eB) are "0" and "0", respectively, and the excitation mode in this case is two-phase excitation. At this time, the phase currents of the U, V, and W phases are almost rectangular waves as shown in FIG. A, and the motor rotates at high speed. In FIG. 7, the excitation mode setting signals (ModeA, ModeB) are "0" and "1", respectively, and the excitation mode in this case is 2-3 phase excitation.
At this time, the phase currents of the U, V, and W phases have a stepwise waveform as shown in FIG. B, and the cycle thereof is twice that in the case of the two phases in FIG. The number is 1/2 times that of the two phases.

Similarly, in FIG. 2 described above, when the excitation mode setting signals (ModeA, ModeB) are "1" and "0", respectively, the excitation mode is W2-3 phase excitation. In FIG. 8, the excitation mode setting signal (ModeA) is set. , ModeB) are "1" and "1" respectively
Then, the excitation mode becomes 2W2-3 phase excitation. The cycle of the phase current of each phase of U, V, W is W2-3 phase, which is twice that of 2-3 phase, and is 2W.
It can be seen that the 2-3 phase is four times as large as the 2-3 phase, and the waveform of the phase current gradually approaches the sine waveform. The number of revolutions also slows down by 1/2 as the phase progresses, and becomes 2W2-3.
In the phase, it is reduced to ⅛ times of the two phases.

As described above, according to the drive circuit of this embodiment, the excitation mode can be set by the excitation mode setting signals (ModeA, ModeB), and the rotation speed designation clock ( Clock) does not have to have a high frequency, so compared to the conventional system that requires a high-speed rotation speed designation clock (CK) during high-speed operation, CP
It is possible to reduce the burden on U.

In the drive circuit of this embodiment, not only the excitation mode setting signals (ModeA, ModeB) are switched to select the excitation mode corresponding to various rotation speeds, but also the double speed signal (DBS) is switched. , It is possible to drive at double speed even in the same excitation mode. This point will be described below. FIG. 9 shows the operation at the time of switching the double speed signal (DBS). This is "1" in normal operation
When switching from "0" to "0", only the rising edge was detected when it was "1".
) Not only the rising edge but also the falling edge is detected, and the time of detection is doubled, so the number of microsteps carved at the same time interval is also doubled, and the rotation speed is doubled even in the same excitation mode. Will be possible.

Although driving in the W2-3 phase is shown in FIG. 9, the double speed signal (DBS) is switched from "1" to "0" on the way and the U, V, W phases are switched at this switching time. The cycle of the phase current is halved, and the rotation speed at this time is doubled. Of course, the rotation speed designation clock (Cloc
Since the frequency of k) does not change, there is no burden on the CPU.

As described above, according to the stepping motor drive circuit of this embodiment, the excitation mode setting signal (Mode) input to the time chart generation unit (21) is input.
A, ModeB) can be switched to select a total of four excitation modes from 2 phase to 2W2-3 phase, and double speed signal (DBS)
By switching, it becomes possible to obtain a double speed rotation speed even in the same excitation mode. For simplicity, Table 1 below shows excitation mode setting signals (ModeA, ModeB), double speed signal (DBS),
The relationship between the excitation mode and the rotation speed of the motor is shown below. In Table 1, No indicates the normal rotation speed of the 2W2-3 phase.

[0028]

[Table 1]

As shown in Table 1, even if the frequency of the rotation number designating clock (Clock) is not changed, two phases to 2W2-3.
2W2 which is the lowest speed drive when double speed drive in 2 phases (double speed signal (DBS) is "0") that can support a total of 4 types of excitation modes and is the highest speed drive including double speed operation.
It becomes possible to drive at 16 times the number of rotations during the normal driving in the -3 phase (double speed signal (DBS) is "1").

Conventionally, when such driving is performed, a rotation frequency designating clock having a frequency of 16 times is required, which causes an excessive load on the CPU, and in reality, such a high speed operation is impossible. However, the drive circuit according to the present embodiment does not require a high-speed rotation number designation clock (Clock), and thus high-speed drive can be performed without imposing a heavy burden on the CPU.

Although the stepping motor drive circuit according to the present embodiment uses the double speed signal (DBS) as a signal for increasing the speed in the same excitation mode, the present invention is not limited to this and, for example, It is also possible to use it for the purpose of switching to the excitation mode one level higher and not changing the rotation speed. For the purpose of reducing vibration in actual driving, the number of steps to be engraved is doubled, for example, transition from W2-3 phase to 2W2-3 phase. In some cases, the driving is performed without changing the rotation speed and changing the rotation speed.

As shown in Table 1 above, the rotational speed and W2- when the double speed signal (DBS) is "0" in the 2W2-3 phase.
In the three phases, the number of rotations of the motor when the double speed signal is "1" is the same as 2No. Therefore, set the excitation mode setting signals (ModeA, ModeB) to "1" and "0", respectively.
After the double speed signal (DBS) is set to "1" and driven in the W2-3 phase, the excitation mode setting signals (ModeA, ModeB) are switched to "1" and "1" respectively, and the double speed signal (DBS) is set to "1". If it is switched to 0 ", the rotation speed can be switched to 2W2-3 phase without changing and remains 2No, so that it is possible to realize smooth driving with less vibration.

As described above, according to the drive circuit of the present embodiment, the excitation mode can be switched without changing the rotation speed by appropriately selecting the excitation mode setting signals (ModeA, ModeB) and the double speed signal (DBS). Thus, it becomes possible to drive a motor with low vibration.

[0034]

As described above, according to the driving circuit of the stepping motor for three-phase excitation of the present invention, only the rising edge of the rotation speed designation clock is detected, so that high speed rotation is required when high speed rotation is required. Unlike the conventional method in which a number designation clock was required, the excitation mode setting unit regulates the rotation speed of the stepping motor based on the detection result of the mode setting auxiliary signal and the mode setting signal. A high-speed rotation speed designation clock is not required when selecting.

Therefore, it becomes possible to reduce the burden on the CPU, which has been overloaded by generating the high-speed rotation number designating clock. In the present invention, when the excitation mode setting unit detects both the rising edge and the falling edge of the rotation speed designating clock, the excitation mode setting unit detects only the rising edge of the rotation speed designating clock in the same mode.
The stepping motor is rotated at twice the number of rotations.

Therefore, the double speed drive can be achieved by detecting the rising edge and the falling edge of the rotation speed designating clock even if the double speed drive is not performed by doubling the rotation speed designating clock as in the prior art. It is possible to reduce the burden on the CPU, which has been overloaded by generating a different rotation speed designation clock. Further, in the present invention, the excitation mode setting unit detects the rising and falling edges of the rotation speed designating clock and doubles the rotation speed as compared with the case where only the rising edge of the rotation speed designating clock is detected. The stepping motor is driven by and the excitation mode in which the step is doubled is selected.

Therefore, by appropriately selecting the excitation mode setting signal and the double speed signal, it becomes possible to rotate the motor with low vibration by switching the excitation mode without changing the rotation speed.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a drive circuit for a stepping motor according to the present invention.

FIG. 2 is a first timing chart explaining the operation of the drive circuit of the stepping motor according to the embodiment of the present invention.

FIG. 3 is a second timing chart explaining the operation of the drive circuit of the stepping motor according to the embodiment of the present invention.

FIG. 4 is a third timing chart explaining the operation of the drive circuit for the stepping motor according to the embodiment of the present invention.

FIG. 5 is a fourth timing chart explaining the operation of the stepping motor drive circuit according to the embodiment of the present invention.

FIG. 6 is a first timing chart illustrating an operation effect of the stepping motor drive circuit according to the embodiment of the present invention.

FIG. 7 is a second timing chart illustrating the operation and effect of the stepping motor drive circuit according to the embodiment of the present invention.

FIG. 8 is a third timing chart illustrating the operation and effect of the stepping motor drive circuit according to the embodiment of the present invention.

FIG. 9 is a fourth timing chart illustrating the operation and effect of the stepping motor drive circuit according to the embodiment of the present invention.

FIG. 10 is a configuration diagram of a drive circuit of a stepping motor according to a conventional example.

[Explanation of symbols]

(21) Time chart generation unit (excitation mode setting unit) (22A) First PWM control unit (22B) Second PWM control unit (23A) First current detection unit (23B) Second current detection unit ( 24A) Vcc level shift circuit (24B) GND level shift circuit (25) Reference voltage generation unit (26) CR oscillator (27) Reference clock generation unit (28) Charge pump (M) Stepping motor (ModeA, ModeB) mode Setting signal (DBS) Double speed signal (Mode setting auxiliary signal) (Hold) Motor temporary stop signal (CW / CCW) Rotation direction switching signal (Enable) Forced OFF signal (Clock) Rotation speed designation clock (Reset) System reset signal

Claims (3)

[Claims] 1. A mode setting signal that defines an excitation mode of a three-phase excitation stepping motor, a rotation speed designation clock that defines the rotation speed of the stepping motor, and detection or rising of only the rising edge of the rotation speed designation clock. A circuit for controlling driving of a stepping motor based on a mode setting auxiliary signal that selects one of detection of rising and falling of the number designation clock, and the rotation speed based on the mode setting auxiliary signal. An excitation mode setting unit that detects only the rising edge of the specified clock or both the rising edge and the falling edge of the rotation speed specified clock, and defines the rotation speed of the stepping motor based on the detection result and the mode setting signal, Drive control of the stepping motor under the control of the excitation mode setting section Driving circuit of a stepping motor and having a part. 2. The excitation mode setting unit, when detecting both the rising and falling edges of the rotation speed designation clock, is more than the case where only the rising edge of the rotation speed designation clock is detected in the same mode. The stepping motor drive circuit according to claim 1, wherein the stepping motor is rotated at twice the number of rotations. 3. The excitation mode setting section, when detecting both the rising edge and the falling edge of the rotation speed designating clock, is twice as much as the case where only the rising edge of the rotation speed designating clock is detected. 2. The stepping motor drive circuit according to claim 1, wherein the stepping motor is driven at a rotational speed of 1, and an excitation mode in which the step is doubled is selected.