JPH01152985A - Drive/control circuit for dc motor - Google Patents

Abstract

PURPOSE:To ensure accurate follow-up performance and response, by a method wherein an output from a D/A converter for D/A conversion of an output from an up/down counter which receives a reference pulse and a rotary pulse is converted into a rectangular wave having an amplitude similar to that of the output from the D/A converter and a pulse width corresponding to phases of both pulses. CONSTITUTION:An up/down counter 14 receives a reference pulse P1 and a rotary pulse P2 and performs counting operation corresponding to the frequency difference between both pulses. Output from the up/down counter 14 is fed through a D/A converter 16 to a motor drive circuit 4. A rectangular wave train circuit 18 converts outputs from D/A converter 16 into rectangular wave train having amplitude equal to that of an output from D/A converter 16 and pulse width corresponding to phase difference between the reference pulse P1 and the rotary pulse P2.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a drive control circuit for a DC motor using a feedback control method.

<Prior art and its problems> For example, DC motors used in acoustic sounding devices such as fish finders can change their rotational speed over a wide range to comply with IMO standards, and are capable of accurate tracking when changing speed. They are required to have responsiveness and responsiveness.

By the way, in order to satisfy the requirement for constant speed stability of a DC motor, a feedback control method is usually adopted. Conventional circuits of this type include, for example, a combination of an up/down counter and a D/A converter, and a reference pulse for setting the rotational speed of a DC motor and a detection pulse obtained by detecting the rotational speed of the DC motor. There is a system in which both pulses are input to an up/down counter, a count output corresponding to the frequency difference between the two pulses is converted into an analog signal by a D/A converter, and this output is directly provided to a motor drive circuit.

This conventional circuit has the advantage of having a relatively simple configuration and being able to control the rotational speed over a wide range by changing the frequency of the reference pulse, but because it is not phase synchronized control, it cannot respond to slight load fluctuations. Therefore, it is not possible to accurately perform constant speed control.

On the other hand, some feedback control methods employ a so-called phase synchronization control method in which a DC motor is controlled at a constant speed according to the phase difference between a reference pulse and a detection pulse. For example, this type of circuit counts the phase difference between a reference pulse and a detection pulse using a counter, gives the counted value as an address to a ROM, and controls a DC motor based on the phase difference data stored in advance in the ROM. Control the rotation speed. (For example, see Japanese Unexamined Patent Publication No. 141988/1988).

In this conventional circuit, highly stable constant speed control can be performed within a predetermined phase difference range, but when the phase difference exceeds one cycle, the counter overflows.
It becomes difficult to arbitrarily set the rotational speed within a wide range and to obtain accurate followability.

The present invention has been made in view of the above circumstances, and provides a DC motor that can be set arbitrarily over a wide rotational speed range and ensures accurate followability and responsiveness to speed changes. At the same time, the purpose is to ensure high constant speed stability.

Means for Solving Problems> In order to achieve the above object, the present invention provides a reference pulse for setting the rotational speed of a DC motor, a detection pulse obtained by detecting the rotational speed of the DC motor, and a detection pulse obtained by detecting the rotational speed of the DC motor. an up/down counter that inputs both pulses and performs a counting operation according to the frequency difference between both pulses, and a D/down counter that converts the count output of this up/down counter into analog and outputs it to the motor drive circuit.
A drive control circuit for a feedback control DC motor equipped with an A converter has the following configuration.

That is, in the present invention, the output of the D/A converter is a rectangular wave train having an amplitude equal to the output of the D/A converter and a pulse width corresponding to the phase difference between the two pulses. It is characterized by having a built-in circuit.

<Function> When changing the rotation speed, if the frequency of the reference pulse is changed, the count value of the up/down counter will change, and the output level of the D/A converter will also change accordingly, so that the rotation speed of the DC motor can be adjusted to the desired rotation speed. is set to the value of Therefore, the rotational speed of the DC motor can be changed over a wide range in accordance with the frequency of the reference pulse.

On the other hand, during steady operation, etc., when the phase difference of the detection pulse with respect to the reference pulse is within a predetermined range,
The count output of the down counter does not change, and therefore the output level of the D/A converter also does not change, but the rectangular wave array circuit makes the output of the D/A converter equal to the output amplitude of the A/D converter. , and is shaped into a rectangular wave train according to the phase difference between the reference pulse and the detection pulse, so the DC motor is controlled in phase synchronization. As a result, constant speed control can be performed accurately even with slight load fluctuations.

<Example> Figure 1 is a block diagram of a drive control circuit for a DC motor, and Figure 2 is a block diagram of a drive control circuit for a DC motor.
The figure shows the A/D for the up/down counter in the same circuit.
FIG. 2 is a configuration diagram showing a connection state of a converter and a rectangular wave array forming circuit. In these figures, the symbol l indicates the entire drive control circuit of the DC motor, 2 is the DC motor, 4 is the motor drive circuit, 6 is a rotation speed detector that detects the rotation speed of the DC motor 2, and 8 is the rotation speed. A detection pulse P having a frequency corresponding to the rotational speed of the DC motor 2 output from the detector 6
, IO is a reference pulse waveform shaper that shapes the waveform of the reference pulse P for setting the rotational speed of the DC motor, and 12 is a detection pulse waveform shaper that shapes the waveform of the detection pulse P from the amplifier 8. be.

Reference numeral 14 denotes an up/down counter which receives both the reference pulse P1 and the detection pulse P and performs a counting operation according to the frequency difference between the two pulses P3 and P2. In this example, the up/down counter 14 is constructed by connecting four stages of flip-flops FF and -PF4 in series, and has 4-bit output terminals Q1 to Q4.

In addition, 16 is a D/A converter that converts the count output of the up/down counter into analog and outputs it to the motor drive circuit 4. 18 is a D/A converter that converts the output of the D/A converter 16 into an analog signal, and 18 converts the output of the D/A converter 16 into an analog signal. This is a rectangular wave train forming circuit that shapes the wave train into a rectangular wave train that is equal in width and has a pulse width that corresponds to the phase difference between the reference pulse P and the detection pulse P. This rectangular wave array circuit 18 is
In this example, the output section of the D/A converter 16 is connected to the diode 20.
The up/down counter 14 is connected to the positive phase output terminal Q of the first stage flip-flop FF through the up/down counter 14.

Next, the operation of the DC motor drive control circuit having the above configuration will be explained.

The rotational speed of the DC motor 2 is detected by a rotational speed detector 6, and the rotational speed detector 6 outputs a detection pulse P having a frequency corresponding to the rotational speed.

This detection pulse P is amplified by an amplifier 8, then waveform-shaped by a detection pulse waveform shaper 12, and then applied to a down terminal DOWN of an up/down counter 14. Further, the reference pulse P1 for setting the rotational speed of the DC motor 4 is
After being waveform-shaped by the reference pulse waveform shaper IO, it is applied to the up terminal UP of the up/down counter 14.

Now, during steady operation, if the phase difference between the detection pulse P and the reference pulse P1 is within the summer cycle, the count output of the up/down counter 14 does not change. Therefore, the output level of the D/A converter 16 does not change, but the reference pulse PI and the detection pulse P of the first stage flip-flop FF of the up/down counter 14
, and the output of the positive phase output terminal Q repeats the level inversion every time. Furthermore, when the phase difference between the detection pulse P and the reference pulse P is small (in the case of the solid line in FIG. 3(b)), the pulse width W of the output from the positive phase output terminal Q also changes as shown in the figure ( Although it is small as shown in Fig. C), when the phase difference between the detection pulses P and increases due to load fluctuations etc. (in the case of the broken line in Fig. 3(b)), the pulse width W of the output of the positive phase output terminal Q also changes to Fig. 3(d). ). Each time the positive phase output terminal Q of the flip-flop FF1 becomes low level, the diode 20 of the rectangular wave array circuit 18 becomes conductive, and the output of the D/A converter 16 is forcibly pulled down to the same low level. Therefore, the output of the D/A converter 16 is as shown in FIG.
As shown in a), while maintaining the level h corresponding to the count value of the up/down counter 14, the pulse width W is adjusted according to the phase difference between the reference pulse P1 and the detection pulse P.
, SW, becomes a rectangular wave train. Since this rectangular wave train signal is given to the motor drive circuit 4, the DC motor 2 is reliably controlled in phase synchronization, and as a result, accurate constant speed control is achieved even with slight load fluctuations. Ru.

On the other hand, when changing the rotational speed, etc., the frequency of the reference pulse P1 changes significantly, so that the phase difference with the detection pulse P2 becomes one cycle or more, causing a temporary deviation from phase synchronization control. In this case, since the frequencies of the reference pulse P and the detection pulse P2 do not match, the up/down counter 14 performs a count-up operation or a count-down operation, and the count output Q1-Q- changes, and accordingly, the D /A
converter! 6's output level also changes. For example, when the frequency of the reference pulse P is set to be thicker than that of the detection pulse P, the up/down counter 14 performs a count-up operation, so that the rectangle given from the D/A converter 16 to the motor drive circuit 4 The output level h of the wave signal is determined by the up/down counter 14 as shown in FIG. 4(b).
It increases in accordance with the count value of . As a result, the rotational speed of the DC motor 2 is increased to follow the frequency of the reference pulse P.

When the rotational speed of the DC motor 2 approaches the set value and the phase difference between the detection pulse P and the reference pulse P falls within one cycle, the output level h of the D/A converter 16,
becomes constant and shifts to the above-mentioned phase synchronization control.

In this way, the rotation speed of the DC motor can be varied over a wide range in accordance with the frequency of the reference pulse, and high constant speed stability can be maintained.

In this embodiment, the up/down counter 14 is constructed by connecting four stages of flip-flops FF and -FF in cascade; however, the present invention is not limited to this, and a structure in which flip-flops are connected in multiple stages may also be used. good. Further, the rectangular wave array forming circuit 18 can be connected not to the first-stage flip-flop FF, but to the output terminal Q of a subsequent-stage flip-flop, if necessary. Further, the rectangular wave array forming circuit 18 is not limited to this embodiment, and for example, the positive phase output terminal Q of a flip-flop FFl is connected to the base of a common emitter switching transistor, and the collector of the transistor is connected to the base of a common emitter switching transistor. D/A converter! 6
It is also possible to configure the output section by connecting the output section.

<Effects of the Invention> According to the present invention, when changing the rotation speed, if the frequency of the reference pulse is changed, the count value of the up/down counter changes, and the output level of the D/A converter changes accordingly. The rotational speed of the DC motor can be varied over a wide range. On the other hand, when the phase difference between the detection pulse and the reference pulse is within a predetermined range during steady operation, etc., phase synchronization control is performed, so the rotation speed can be kept constant even with slight load fluctuations.

In this way, the rotational speed of the DC motor can be arbitrarily set within a wide range, and the excellent effect of ensuring accurate followability and responsiveness when changing the speed is achieved.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. Fig. 1 is a block diagram of a DC motor drive control circuit, and Fig. 2 shows an A/D converter and a rectangular wave array circuit for an up/down counter in the same circuit. A configuration diagram showing the connection status of , Figure 3 is up/
Down counter person, output signal time chart, 4th
The figure is a waveform diagram of a signal shaped into a rectangular wave train by a rectangular wave train forming circuit. l...DC motor drive control circuit, 2...DC motor, 14...up/down counter, 16...D
/A converter, 18... rectangular wave train conversion circuit.

Claims (1)

[Claims] (1) The reference pulse for setting the rotational speed of the DC motor and the detection pulse obtained by detecting the rotational speed of the DC motor are both input, and up/down is performed according to the frequency difference between the two pulses. In a feedback control DC motor drive control circuit comprising a counter and a D/A converter that converts the count output of the up/down counter into analog and outputs it to the motor drive circuit, the output of the D/A converter is provided. Driving a DC motor, characterized in that a rectangular wave train converting circuit is provided to convert the signal into a rectangular wave train having an amplitude equal to the output of the D/A converter and a pulse width corresponding to the phase difference between the two pulses. control circuit.