JPH033476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speed control device for an electric motor that performs pulse width modulation driving.

Conventional configurations and their problems In recent years, there has been remarkable progress in speed control devices that drive motors using pulse width modulation, detect the motor's rotational speed and flowing current, and control the speed of the motor. .

A conventional speed control device will be explained below. Fig. 1 is a configuration diagram of a conventional speed control device, in which 1 is an oscillator that oscillates at a constant frequency, 2 is a counter that counts a set count value in the direction of decreasing by the output of the oscillator 1, and the counter output During counting, a "1" output is output, and after the counting is completed, a "0" output is output. Reference numeral 3 denotes a drive device composed of transistors and the like that performs power conversion based on the output of the counter 2 and drives the motor. 4 is a motor; 5 is a current detection device that detects the current flowing through the motor; 6 is a speed detection device that detects the rotational speed of the motor; the current detection device 5 and the speed detection device 6;
The output of is input to the control logic unit 7. The control logic device 7 includes a current detection device 5 and a speed detection device 6.
Pulse width data to be set in the counter 2 is determined by calculation from the output of the counter 2, and the speed of the motor is controlled by setting the pulse width data in the counter 2. 8 is an oscillator that generates a constant frequency, and is input to the control logic device 7. 9 is a speed command device, which gives a speed command to the control logic device 7.

The operation of the speed control device configured as described above will be explained below with reference to FIGS. 1 and 2. Figure 2 is a timing chart of the waveforms of each part in Figure 1, and the QSC1 signal is the output of oscillator 1,
The QSC2 signal is the output of the oscillator 8, the CQUT signal is the output of the counter 2, and the IQUT signal is the output of the current detection device. It is now assumed that a speed command is given to the control logic device 7 by the speed command device 9, and the electric motor 4 is rotating at a constant speed. The control logic unit 7 is
In synchronization with the rising edge of the QSC2 signal, the speed command value,
The electric power to be supplied to the electric motor 4 is calculated from the speed detection value and the speed detection value, and pulse width data is set in the counter 2. When the pulse width data is set
The CQUT signal becomes “1” and from this point on, the count value of counter 2, that is, the pulse width data is QSC1
The CQUT signal is counted in a decreasing direction depending on the signal, and the CQUT signal is held at "1" until the counted value reaches "0". If the count value of counter 2 becomes “0”
The CQUT signal becomes "0". The drive device 3 is
Power conversion is performed using the CQUT signal, power is supplied to the electric motor 4, and the electric motor 4 rotates according to the applied electric power. In other words, if the pulse width data set in the counter 2 is increased, the pulse width of the CQUT signal becomes wider, and the rotation speed of the motor 4 increases.If the pulse width data is reduced, the pulse width of the CQUT signal becomes narrower, and the rotation speed of the motor 4 increases. The number of rotations decreases. Second
As shown in the figure, if the IQUT signal rises for some reason, the control logic device 7 reduces the pulse width data set in the counter 2, reduces the power given to the motor 4, and maintains constant speed rotation. If the IQUT signal falls in the opposite case, the pulse width data will be widened to maintain constant rotation speed. Although not shown here, the pulse width is controlled to be narrower when the output of the current detection device exceeds the set rotation speed, and to be widened when the output falls below the set rotation speed. It will maintain constant speed rotation.

As explained above, in the speed control device shown in FIG. rotates according to the speed command value.

However, in the above conventional configuration, the current flowing through the motor 4 is detected by the current detection device 5 and inputted to the control logic device 7, and then the control logic device 7 sends pulse width data to the counter 2 according to the detected value. As a result, the detection speed of the control logic device 7 is delayed by the time required for the calculation of the control logic device 7 (delayed by the time T in Fig. 2), and the responsiveness of the system is significantly deteriorated. It had In addition, the control logic unit 7 is connected to the microprocessor and peripherals.
When configured with an LSI (large-scale integrated circuit; the same applies hereinafter) and perform digital processing, the current detection device 5 requires an analog-to-digital conversion circuit, which increases complexity and costs, and also requires a microprocessor. Since a considerable portion of the microprocessor's operation is spent on the above processing, there is also the problem that other processing by the microprocessor is restricted.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
A simple configuration speeds up the response of the speed control system, and provides a more stable and efficient speed control device.

Structure of the Invention In order to achieve the above object, the present invention includes a first oscillator whose oscillation frequency can be varied;
A counter that can count the output of an oscillator and generate an arbitrary pulse width signal, a drive device that drives a motor using a pulse width modulation signal generated from the counter output, and a current detection device that detects the current of the motor. , a speed detection device for detecting the rotational speed of the electric motor, a control logic device for setting pulse width data in the counter based on the detected current value and the detected speed value, and a control logic device for providing timing for setting the pulse width data to the control logic device. A second generator that generates a constant frequency
oscillator, and by varying the frequency of the first oscillator with the feedback value of the current detection device, the response of the speed control system is significantly increased, the configuration is simple, the cost is low, and the speed control device is This makes it possible to improve processing efficiency.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 3 and subsequent drawings. FIG. 3 is a configuration diagram of a speed control device in an embodiment of the present invention. In FIG. 3, 11 is a counter, 12 is a drive device, and 13 is a counter.
15 is an electric motor, 15 is a speed detection device, 16 is a control logic device, 17 is an oscillator, and 18 is a speed command device, which are the same as those of the conventional example shown in FIG. 14 is a current detection device, 10 is an oscillator, and the output of the current detection device 14 is connected to the oscillator 10. If the current detection value is large, the oscillation frequency of the oscillator 10 becomes high, and if the current detection value is small, the oscillation frequency is low. Become. The output of the oscillator 10 is also connected to a counter 11, whereby the pulse width data set in the counter 2 is subtracted.

The operation of the speed control device of this embodiment configured as described above will be described below. FIG. 4 is a timing chart of waveforms of various parts in FIG. 3. QSC3 signal is the output of oscillator 10, QSC4 signal is the output of oscillator 17, CQUT1 signal is the output of counter 1
1, the IQUT1 signal is the output of the current detection device 14. It is now assumed that a speed command is given to the control logic device 16 by the speed command device 18 and the electric motor 13 is rotating at a constant speed. Next, if the IQUT1 signal rises for some reason, IQUT1
Since the signal is input to the oscillator 10, the oscillation frequency (QSC3 signal) of the oscillator 10 becomes high.
(In the conventional configuration (Fig. 1), when the IQUT signal rises, the control logic device 7 inputs the IQUT in synchronization with the rising edge of the output of the oscillator 8, and inputs the IQUT in the direction of decreasing the current, that is, the counter 2. However, in the present invention, the pulse width data value to be set was reduced.
The frequency of the QSC3 signal increases, producing the same effect as reducing the pulse width data value. In other words, in the conventional example, in order to shorten (lengthen) the output pulse width data of the counter, the frequency of the oscillator connected to the counter is kept constant, and the control logic device shortens (lengthens) the pulse width data value according to the current detection value. In contrast, in the configuration according to the embodiment, in order to shorten (lengthen) the output pulse width data of the counter, the frequency of the oscillator connected to the counter increases (lowers) in accordance with the detected current value.
It works to produce exactly the same effect. In the case of this embodiment, the control logic device 16 calculates the power to be supplied to the motor 13 from the speed command value and speed detection value in synchronization with the rise of the output of the oscillator 17 (QSC4 signal), and sends pulse width data to the counter 11. Set. The motor 13 operates similarly to the conventional example except that the current detection operation does not go through the control logic device 16.
will maintain constant speed rotation according to the command value of speed command value 18.

As described above, according to this embodiment, the control logic device 16 is not concerned with current detection at all, and the oscillation frequency of the oscillator 10 is increased or decreased according to the detected current value.
Since it is added to the pulse width, the load on the control logic is reduced and the response of the speed control system is significantly improved (T in FIG. 2 becomes T' in FIG. 4).

Hereinafter, a speed control device using the invention described above will be explained using FIG. 5. 19 is an oscillator, 2
0 is a counter, 21 is a drive device, 22 is an electric motor,
23 is a current detection device, 25 is a speed detection device, 26
27 is a control logic device, 27 is an oscillator, and 28 is a speed command device, which have the same structure as in FIG. 24 is a phase shift device that advances the phase, and if the phase is not advanced when feeding back the output of the current detection device 14, the control system may become unstable depending on the type of motor 13 or the load condition. This is to prevent By making the amount of phase shift variable, a stable speed control system can be achieved no matter what motor is connected or even when the load changes.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, the current flowing through the motor is detected by a current detection device, and the oscillation frequency is varied without inputting the detected value to the control logic device. Since the output of the oscillator is used as the oscillation source of the counter that generates the pulse width signal, the pulse width is increased or decreased directly by the counter. In other words, the control logic device that conventionally had to monitor both speed detection and current detection can now concentrate solely on speed detection, greatly improving the responsiveness of the speed control system. and processing efficiency will be improved. Conventionally, when the control logic device was configured with a microprocessor and peripheral LSI, the current detection device required an analog-to-digital conversion circuit, but with the present invention, only an analog signal is required, simplifying the circuit. Accordingly, it is possible to realize a speed control device that can obtain a number of excellent effects, such as reducing costs accordingly.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional speed control device, FIG. 2 is a timing chart of waveforms of each part in FIG. 1, FIG. 3 is a configuration diagram of a speed control device in an embodiment of the present invention, and FIG. FIG. 5 is a timing chart of waveforms of various parts, and FIG. 5 is a configuration diagram of a speed control device in another embodiment of the present invention. 1, 10, 19...oscillator, 2, 11, 20...
... Counter, 3, 12, 21 ... Drive device, 4,
13, 22... Electric motor, 5, 14, 23... Current detection device, 6, 15, 25... Speed detection device,
7, 16, 26...control logic device, 8, 17, 2
7... Oscillator, 9, 18, 28... Speed command device, 24... Phase shift device.

Claims (1)

[Claims] 1. A first oscillator whose oscillation frequency can be varied, a counter that counts the output of the first oscillator and generates an arbitrary pulse width signal, and a pulse width modulated signal based on the output of this counter. a current detection device that detects the current of the motor; a speed detection device that detects the rotational speed of the motor; and a current detection value and speed obtained from the current detection device and the speed detection device. a control logic device that sets pulse width data in the counter based on the detected value; and a second oscillator that generates a constant frequency for giving timing for setting the pulse width data to the control logic device; A speed control device, characterized in that speed control is performed by changing the frequency of the first oscillator based on a feedback value. 2. A first oscillator whose oscillation frequency can be varied, a counter which can count the output of the first oscillator and generate an arbitrary pulse width signal, and a motor using a pulse width modulation signal from the output of this counter. a current detection device that detects the current of the motor; a phase shift device that advances the phase of the output of the current detection device; a speed detection device that detects the rotational speed of the motor; A control logic device that sets pulse width data in the counter based on the current detection value and speed detection value obtained from the detection device; and a second oscillator that generates a constant frequency for giving the control logic device timing for setting the pulse width data. a feedback value of the current detection device is input to the phase shift device to advance the phase, and the frequency of the first oscillator is changed by the output of the phase shift device to perform speed control. Control device.