JP2697964B2 - Motor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing a malfunction of a motor driving device for driving a DC motor at a constant speed.

[0002]

2. Description of the Related Art A motor drive for driving a DC motor at a constant speed is used in, for example, an electric curtain drive for automatically opening and closing a curtain. In this electric curtain driving device, as shown in FIG.
The control of the M control unit 3 outputs a pulse train signal having an appropriate pulse width.
And supplies it to the DC motor 7. Then, the motor current Im is detected by the detection unit 5 and the output of the detection unit 5 is fed back to the comparison unit 2 via the FV conversion unit 6 to control the curtain opening / closing speed to be constant. More specifically, the speed setting unit 1 outputs a voltage signal V corresponding to the set speed.
r is output, the detection unit 5 composed of a current transformer or the like outputs a detection signal Vp corresponding to the periodic change of the current Im flowing to the DC motor 7, and the FV conversion unit 6 converts the detection signal Vp into a voltage signal Vs. The voltage signal Vs is converted to a voltage signal (Vr−
Vs) to the PWM control unit 3, and the voltage signal (Vr)
−Vs), the motor current Im is appropriately adjusted to control the motor speed to a constant value corresponding to the set value.

[0003] By the way, the FV of this type of motor driving device is used.
In the converter 6, the comparator 8 and the timer 9 create a pulse signal corresponding to the excitation phase switching cycle of the DC motor 7 from the detection signal Vp indicating the periodic change of the motor current Im of the detector 5, and then generate the pulse signal. Is used to convert to a voltage signal. That is, by comparing the reference voltage V _C with the detection signal Vp shown in FIG.
The rectangular wave output Vo shown in FIG. 3C is obtained, and the timer 9 is operated with the change of the rectangular wave output Vo as a trigger to generate a pulse signal having a constant pulse width T shown in FIG. I have.

Conventionally, an edge-triggered monostable multivibrator that triggers on the falling edge of the rectangular wave output Vo is used as the timer 9, or the state of the input is monitored at regular intervals, and the input is set to a low level. , A program timer constituted by a microcomputer that outputs a pulse having a constant width T is used.

[0005]

However, in the case where the above-mentioned edge-triggered monostable multivibrator is used, if external noise is mixed into the rectangular wave output Vo,
This extraneous noise cannot be distinguished from the rectangular wave output Vo. On the other hand, in the case of a program timer, a signal having a narrow pulse width such as external noise is not taken in as data, which is advantageous for external noise.

However, in the case of this program timer, the state of the input is monitored at a constant period, and when the input is at a low level, a pulse having a constant width T is output. When the motor current Im changes gently as shown at the right end of the graph, the time width during which the rectangular wave output Vo becomes low level becomes sufficiently longer than the input monitoring period of the program as shown in FIG. Despite the desire to obtain the pulse signal Vt shown in FIG.
A plurality of pulse signals Vt ′ are output from the timer 9 as shown in FIG. In other words, the same pulse signal Vt is output as when the motor speed is rapidly increasing, causing a malfunction. Therefore, if the motor current Im changes gradually, it is necessary to take some measures. There was a disadvantage that there is. Note that such a problem can also occur when starting the motor.

The present invention has been made in view of the above points, and an object of the present invention is to provide a motor drive device which does not cause a malfunction due to external noise or an instantaneous power failure.

[0008]

According to the present invention, in order to achieve the above object, a trigger is activated only when there is a binary combination state of a high level and a low level immediately before and immediately after an edge of an input signal. A program timer is used as a timer.

[0009]

According to the present invention, by using a program timer as a timer as described above, a signal having a narrow pulse width such as external noise is not taken in as data, becomes strong against external noise, and is used for a signal immediately before an edge of an input signal. Immediately after the trigger is activated when there is a binary combination of high level and low level, it is not affected by the waveform of the input signal and an accurate pulse signal can be generated even when the motor current changes slowly. It is designed to be able to output.

[0010]

1 and 2 show an embodiment of the present invention. As shown in FIG. 2, the motor drive device of the present embodiment includes a detection unit 5 as speed detection means for detecting a periodic current change occurring when the excitation phase of the DC motor 7 is switched to detect the motor speed. An FV converter 6 as a frequency / voltage converter for converting a speed signal indicated by a change in current detected by the detector 5 into a voltage signal, and a speed setting unit 1 as a speed setting unit for setting the speed of the DC motor 7. And a comparing unit 2 as comparing means for comparing the output of the FV conversion unit 6 with a speed setting signal composed of a voltage signal provided from the speed setting unit 1. The DC motor 6 is operated in accordance with the comparison result of the comparing unit 2. It comprises a PWM control section 3 and a power amplification section 4 as motor current supply means for supplying a current having a constant motor speed. The FV conversion unit 6 compares the detection signal Vp output from the detection unit 5 with a reference voltage Vc to output a rectangular wave signal whose waveform is shaped, and a DC motor which is triggered by the output of the comparator 8. And a timer 9 for outputting a pulse signal Vt in accordance with the excitation phase switching period of No. 7. That is, in the case of the motor driving device of the present embodiment, the configuration is no different from the conventional one.
However, in the case of this embodiment, a program timer configured on a microcomputer program is used as the timer 9,
It is characterized in that timer processing is performed according to a program described later.

The operation of this embodiment will be described below. However,
The operation of the speed control system, which is the basic configuration of the present embodiment, is the same as the operation described in the section of the related art, so that the description thereof will be omitted, and only the timer processing operation characteristic of the present embodiment will be described. In this embodiment, as shown in the flowchart of FIG. 1, if the rectangular wave output Vo (hereinafter, referred to as an input signal) of the comparator 8 is at a high level, 1 is stored in the memory M built in the microcomputer, and then The value does not change unless the input signal Vo goes low. At this stage, no trigger is applied as a timer. After that, when the input signal Vo becomes low level, the pulse signal Vt having a constant width T is output. When the pulse signal Vt is output, the memory M is set to 0, and the monitoring state of the input signal Vo is continued.

In this way, even when the low level period of the input signal Vo is long as in the case of the conventional program timer, a plurality of pulse signals (Vt 'shown in FIG. 3E) are not output. . That is, even if the high-level input signal Vo goes low as described above and this state continues, the pulse signal Vt of the constant width T is output again because the memory M is in the state of 0. There is no input signal V
According to the present embodiment, one accurate pulse signal Vt can be output regardless of the signal waveform (the magnitude of the pulse width) of the input signal Vo. Therefore,
There is no malfunction at instantaneous power failure or startup. In addition, in this embodiment, since the external noise is not taken in as data by using the program timer, a malfunction due to the external noise is less likely to occur.

[0013]

According to the present invention, as described above, a program timer that triggers only when there is a binary combination of a high level and a low level immediately before and immediately after an edge of an input signal is used as a timer. By using a program timer as a timer, a signal with a narrow pulse width such as external noise is not taken in as data, and becomes strong against external noise.Moreover, a high level and a low level occur immediately before and immediately after an edge of an input signal. The trigger is activated only when there is a combination of the two values, so the waveform of the input signal is not affected, and accurate pulse signals can be output even when the motor current changes slowly. There is no malfunction.

[Brief description of the drawings]

FIG. 1 is a flowchart of a timer processing operation according to an embodiment of the present invention.

FIG. 2A is a block diagram illustrating an entire configuration. (B) is a circuit diagram showing a main part configuration of the FV converter of the above.

FIG. 3 is an operation explanatory view showing the above operation and a conventional problem.

[Explanation of symbols]

 Reference Signs List 1 speed setting unit 2 comparison unit 3 PWM control unit 4 power amplification unit 5 detection unit 6 FV conversion unit 7 DC motor 8 comparator 9 timer

Claims (1)

(57) [Claims] 1. A speed detecting means for detecting a motor speed by detecting a periodic current change occurring when an excitation phase of a DC motor is switched, and a voltage signal represented by the current change detected by the speed detecting means. Frequency / voltage converting means for converting the output of the DC / DC converter, speed setting means for setting the speed of the DC motor, and comparing means for comparing the output of the frequency / voltage converting means with a speed setting signal consisting of a voltage signal provided from the speed setting means. Motor current supply means for supplying a current for causing the DC motor to have a constant motor speed in accordance with the comparison result of the comparison means. The output of the speed detection means is waveform-shaped to change the excitation phase of the DC motor. In the motor drive device provided with a timer for generating a pulse signal according to a cycle in the frequency / voltage conversion means, a high level signal is output immediately before and after an edge of the input signal. A motor drive device comprising a program timer that triggers only when there is a binary combination state of a low level and a low level as the timer.