JPS6329514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention forms one feedback pulse every time a DC motor rotates by a predetermined angle, and the DC The present invention relates to a method for driving a DC motor, which controls the speed of the DC motor by driving the motor.

Conventionally, this type of driving method is known as a driving method using so-called phase-locked loop (PLL) control, in which a phase comparator 1 inputs an input pulse f _IN and a feedback pulse f _FB , as shown in FIG. The CR filter circuit 2 smoothes this output pulse and outputs a DC voltage according to the pulse width, and the transistor 3 supplies a current according to this DC voltage to the DC motor 4. The rotation angle detector 5 outputs a pulse every time the DC motor 4 rotates by a predetermined angle, and the waveform shaping circuit 6 shapes this output pulse and outputs it as the feedback pulse f _FB (θ). It was a composition. Note that the diode D1 absorbs the back electromotive force of the DC motor 4.

However, the above-mentioned conventional type has the disadvantage that a delay occurs due to the time constant of the CR filter circuit 2, resulting in poor start-up and stop characteristics.Also, since the transistor 3 is used in the active region, the transistor 3 generates a large amount of heat. Ta.

The present invention eliminates the above-mentioned drawbacks and will be explained in detail below with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention. In the same figure, when the feedback pulse f _FB is delayed in phase from the input pulse f _IN , a pulse of positive polarity with a width corresponding to the phase difference is outputted, and the feedback pulse f _FB is delayed in phase from the input pulse f _{IN .} A tri-state output Huez comparator that outputs a negative polarity pulse with a width corresponding to the phase difference when the phase is further advanced, and enters a high impedance output state when the positive polarity pulse and negative polarity pulse are not output. (hereinafter referred to as a three-value phase comparator), 8 is a first level determination circuit that is turned on only when the three-value phase comparator 7 outputs a pulse of positive polarity, and 9 is a first level determination circuit when the three-value phase comparator 7 has a negative polarity. 10 is a first transistor that is turned on when the first level determination circuit 8 is turned on and supplies current to the DC motor 4; 11 is the first transistor that is turned on when the first level determination circuit 8 is on; Second transistors R1, R2, R that are turned on due to the on state of the second level determination circuit 9 and absorb the back electromotive force of the DC motor 4;
3 and R4 are resistors, ZD is a Zener diode,
Q1 is a transistor.

The operation in the above configuration will be explained. First, the input pulse f _IN shown in FIG. 3A is input to the three-value phase comparator 7. At this time, the DC motor 4 is stopped and the feedback pulse _fFB is not input to the three-value phase comparator 7. Therefore, the three-level phase comparator 7 outputs the positive pulse shown in FIG. 3C, the first level determination circuit 8 is turned on, and only the first transistor 10 is turned on as shown in FIG. 3D. state, and the DC motor 4 rotates. The rotation angle detector 5 outputs one pulse every time the DC motor 4 rotates by a predetermined angle, and the waveform shaping circuit 6 shapes the output pulse into a feedback pulse f _FB shown in FIG.
It is outputted to the three-value phase comparator 7 as a signal. While the rotation speed of the DC motor 4 is low, the feedback pulse f _FB lags behind the input pulse f _IN by a large amount, so a positive pulse with a large pulse width is output from the three-value phase comparator 7, and the DC motor 4 is accelerated for a long time. Furthermore, while the three-level phase comparator 7 does not output a positive pulse or a negative pulse, both the first transistor 10 and the second transistor 11 are in the OFF state, so that the DC motor 4 rotates due to inertia and causes friction. It is weakly decelerated by the force. In this way, the motor 4 is gradually accelerated, and the input pulse f _IN
When the delay of the feedback pulse _fFB with respect to the feedback pulse fFB decreases to a certain value, the acceleration force by the first transistor 10 and the frictional force are balanced, and the rotational speed of the DC motor 4 becomes constant. After this, when the rotational speed of the DC motor 4 increases a little, the input pulse
The delay of the feedback pulse f _FB with respect to f _IN is reduced, and the pulse width of the positive pulse output from the three-value phase comparator 7 is reduced,
Since the acceleration time of the DC motor 4 becomes shorter, the rotational speed of the DC motor 4 becomes lower. Moreover, when the rotational speed of the DC motor 4 becomes a little low, the input pulse
The delay of the feedback pulse f _FB with respect to f _IN increases, and the pulse width of the positive pulse output from the three-value phase comparator 7 increases,
Since the acceleration time of the DC motor 4 becomes longer, the rotational speed of the DC motor 4 becomes higher. Furthermore, when a large load fluctuation occurs due to mechanical factors and the rotational speed of the DC motor 4 increases greatly, the feedback pulse f _FB is ahead of the input pulse f _IN ;
At this time, the three-level phase comparator 7 outputs a negative pulse as shown in FIG. Turns on. Therefore, all the back electromotive force generated by the rotation of the DC motor 4 is absorbed, and the rotational speed of the DC motor 4 is rapidly reduced. Therefore, the DC motor 4 is maintained at a constant rotational speed depending on the frequency of the input pulse f _IN .

Next, if the input pulse f _IN is not input to the three-value phase comparator 7, the input pulse f _IN
This is similar to the case where the feedback pulse f _FB is extremely advanced, the three-value phase comparator 7 becomes negative polarity, the second level determination circuit 9 is turned on, and the second transistor 11 is turned on. only turns on. For this reason, the DC motor 4 is rapidly decelerated as described above and comes to a stop within a short period of time.

Note that in the above embodiment, the first transistor 1
Since the transistor 0 and the second transistor 11 operate only in the on state and the off state, that is, in the saturation region or the cutoff region, the amount of heat generated by themselves is extremely low. Further, as shown in FIG. 2, the first determination circuit 8 includes resistors R1 and R2, transistors Tr,
It can be constructed from a Zener diode ZD, and the second determination circuit 9 can use a commercially available TTL/IC inverter circuit.

As mentioned above, the embodiment shown in FIG. 2 brakes the DC motor 4 as soon as it becomes higher than the desired speed, and accelerates it as soon as the DC motor 4 becomes lower than the desired speed. Vibration is likely to occur for loads with large time constants. Therefore, it is suitable for applications where unevenness in rotational speed does not have much effect. On the other hand, when it is desired to minimize the rotational speed unevenness as much as possible, such as in the carriage control of a dot printer that prints while continuously moving the carriage, the above embodiment is insufficient, so it is necessary to change it as shown in Figure 4. desirable.

FIG. 4 shows another embodiment of the present invention, in which the circuit controls the on-state and off-state of the first transistor 10 and the second transistor 11 based on the output of the three-value phase comparator 7. It includes a first control circuit and a second control circuit that performs control based on the input pulse f _IN and also performs control with priority over the first control circuit. Here, this first control circuit consists of a first level determination circuit 8 and a second level determination circuit 9, and
In the embodiment shown in the figure, the on-state and off-state of the first transistor 10 and the second transistor 11 are controlled only by this first control circuit. The second control circuit is newly provided in this embodiment, and while the input pulse f _IN is being input,
A third transistor 12 is turned on and turns on the first transistor 10 regardless of the output state of the first level determination circuit 8; and when this third transistor 12 is turned on, the output of the second level determination circuit 9 is Second transistor 1 regardless of state
1 and a diode 13 that turns OFF. In other words, this second control circuit
The control circuit is configured to control the first transistor 10 and the second transistor 11 with priority over the control circuit, and while the input pulse f _IN is input,
The first transistor 10 is turned on and the second transistor 11 is turned off.

In the embodiment shown in FIG. 4, the third transistor 12 is in the on state while the input pulse f _IN is input to the three-value phase comparator 7, so the first transistor 10 is in the on state, and The second transistor 11 is turned off through the diode 13. Therefore, each time the input pulse f _IN is input to the three-value phase comparator 7, the DC motor 4 is accelerated by at least the pulse width of the input pulse f _IN . Figure 5 I
E is a time chart showing this, and FIG. 5A is the input pulse _IN , FIG. 5B is the feedback pulse _fFB , FIG. The output of one transistor 10,
FIG. 5E shows the output of the second transistor 11, respectively. Other operations are the same as the embodiment shown in FIG. Therefore, this embodiment is the same as the embodiment shown in FIG. 2 at startup and stop, but after the motor 4 reaches a steady speed, the phase of the feedback pulse _fFB changes to that of the input pulse _fIN. It will lead or be equal to the phase and will not lag unless there is a large load change. Therefore, the rotational speed of the DC motor 4 is controlled by the amount of time the second transistor 11 is in the ON state, and this point differs from the embodiment shown in FIG. 2 above. In other words, in the embodiment shown in FIG. 4, a constant driving force is intermittently and repeatedly applied to the DC motor 4 using an open-loop control system, and when an excess or deficiency occurs in this constant driving force, a closed-loop control system is applied. This also provides the necessary driving force or braking force to the motor 4, thereby canceling out the excess or deficiency of the driving force. Therefore, the constant driving force is applied to the DC motor 4.
If it is set appropriately according to the rotational speed of the DC motor 4, there will be almost no unevenness in the rotational speed of the DC motor 4.

As described in detail above, according to the present invention, at least when the phase of the feedback pulse lags behind the phase of the input pulse, the first transistor is switched from the off state, which is the damping region, to the on state, which is the saturation region. When the phase of the feedback pulse advances with respect to the phase of the input pulse, the second transistor is switched from the OFF state, which is the damping region, to the ON state, which is the saturation region, and the DC motor is turned on. Since the back electromotive force is absorbed, the heat generated in the first and second transistors is extremely low, and the motor can be started and stopped in a short time. Furthermore, by intermittently and repeatedly applying a constant driving force to the DC motor by keeping the first transistor in the on state and the second transistor in the off state while input pulses are being input, it is possible to almost eliminate irregularities in rotational speed. be.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional example, Fig. 2 is a block diagram showing an embodiment according to the present invention, Fig. 3 A to E are time charts thereof, and Fig. 4 is another embodiment according to the present invention. The block diagram of FIG. 4...DC motor, 5...rotation angle detector, 6...waveform shaping circuit, 7...three-value phase comparator, 8...
first level determination circuit, 9... second level determination circuit,
10...First transistor, 11...Second transistor, 12...Third transistor, 13...Diode.

Claims (1)

[Claims] 1. The position between the input pulse that drives the DC motor and the feedback pulse from a feedback pulse generating means that generates one feedback pulse every time the DC motor rotates by a certain angle. In the DC motor drive method, the DC motor drive method detects a phase difference using a phase comparison means to control a DC motor drive transistor, and drives the DC motor for a time corresponding to the phase difference to rotate the DC motor at a desired rotation speed. transistor, one is DC
It is composed of a first transistor that supplies current to the motor and a second transistor that absorbs the back electromotive force of the DC motor, and the on state and off state of the first transistor and the second transistor. A first control circuit that performs control based on the output of the phase comparison means; and a second control circuit that performs control based on the input pulse and gives priority to the first control circuit. and a control circuit, wherein the first control circuit detects that the phase of the feedback pulse lags behind the phase of the input pulse and a phase difference based on the output of the phase comparison means. , whereby the first transistor is turned on and the second transistor is turned off for a time corresponding to the phase difference, and the first control circuit adjusts the input pulse based on the output of the phase comparison means. detects that the phase of the feedback pulse is ahead of the phase of the feedback pulse and detects a phase difference, and thereby turns off the first transistor and turns on the second transistor for a time corresponding to the phase difference. and the second control circuit turns on the first transistor and turns off the second transistor while the input pulse is input. .