JPS61128783A - Constant speed controller of dc motor - Google Patents

Abstract

PURPOSE:To remove an unnecessary pulse by processing a rectifying pulse and a sawtooth wave by a threshold value processor. CONSTITUTION:A current pulse is full-wave rectified by a waveform rectifier 15. Unnecessary component is removed from the rectified pulse by the first threshold value processor 12. When the gate signal of a gate circuit 13 is high level, the frequency of the pulse is converted to a voltage through the gate circuit 13, a sawtooth wave generator 4 and a sample-holding circuit 16. The converted voltage is compared with a reference voltage by a speed controller, and the rotating speed of a DC motor 2 is controlled. A gate signal applied to the gate circuit 13 is obtained by processing the output of a sawtooth wave generator 14 by the second threshold value processor 14. Thus, a speed control which is not affected by the influence of a noise can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a DC motor constant speed control device used in an automatic focusing device of a color camera, etc.

BACKGROUND OF THE INVENTION FIG. 3 shows a conventional constant-speed speed control device of the type that detects the rotational speed of a DC motor as the frequency of a pulse train and performs speed control. Below, we will discuss the configuration of this conventional example in the third section.
This will be explained with figures. In Fig. 3, 1 is a pulse detection device that detects pulses generated by the commutator of the DC motor 2, 3 is a waveform shaping device that amplifies the detected pulses and detects both waves, and 4 is the waveform shaping device that detects the pulses generated by the DC motor 2. A sawtooth wave generator generates a sawtooth wave using a pulse as a trigger; 5 is a sample 4-hold circuit that holds the voltage of the sawtooth wave; and 6 is an integrator that integrates the held voltage.

Reference numeral 7 denotes a speed control device that controls the rotational speed of the DC motor 2 by voltage. 8 is a coupling capacitor.

9 is a sawtooth wave generating capacitor, 10 is a holding capacitor, and 11 is an integrating capacitor.

Next, the operation of the above conventional example will be explained. When the DC motor 2 rotates, a current pulse is generated due to its commutator 1, and this pulse is detected by the pulse detection device 1. Here, this pulse is processed by the waveform shaping device 3. Sawtooth wave generator4. Sample/hold circuit5. It is converted into voltage through an integrator 6. Next, the converted voltage is compared with a reference voltage corresponding to the set speed in the speed control device 7,
The rotational speed is controlled depending on the addition or lack thereof.

Problem 1 to be Solved by the Invention: However, in the conventional example described above, pulse detection is easily affected by noise, and pulses generated in the commutator also have variations in the spacing between the electrodes that make up the commutator. Unnecessary pulses were mixed in, making it difficult to obtain stable rotation. In addition, it was necessary to insert an integrator into the control loop to ensure smooth control, and a capacitor was required for coupling, which increased the number of parts and was disadvantageous in terms of implementation.

The present invention eliminates the above drawbacks, eliminates the effects of noise and unnecessary pulses, provides stable rotation, reduces the number of capacitors that pose a bottleneck in mounting, and achieves miniaturization.

Means for Solving the Problem In order to achieve the above object, the present invention provides a device for detecting pulses generated by a commutator of a DC motor, a waveform shaping device for shaping the detected pulses, and a dark value processing of the shaped pulses. The first thing to clip below the noise level? %1@ A value processing device, a gate circuit, a device that generates a sawtooth wave using the gated pulse as a trigger, and a threshold processing for the sawtooth wave,
a second threshold processing device that generates a gate signal for the gate circuit; and a device that samples and holds the sawtooth wave;
It consists of a device that controls the speed of the DC motor by comparing the held voltage with a reference voltage.

Therefore, according to the present invention, the noise component of the detected rectified pulse is removed by the first dark value processing device, and the sawtooth wave is further passed through the second threshold processing device to generate a gate signal.
This gate signal can remove unnecessary pulses, so
Stable speed control can be achieved.

EXAMPLE An example of the present invention will be explained below with reference to FIG. 1.2.4.7.9.10 are the same as in FIG.

12 is a first value processing circuit, 13 is a gate circuit, 14 is a second value processing circuit for generating a gate signal, and 15 is a pulse shaping device whose input can be directly connected to the pulse detection circuit 1 by resistor dividing means.

16 is a sample and hold circuit having an integration function.

Next, the operation of the above configuration will be explained in conjunction with FIG. 2. When the DC motor 2 rotates, the pulse detection device 1 detects the current pulses that expel insects, and the waveform shaping device 15 rectifies both waves as shown in FIG. 2a. The shaped pulse is passed through the first threshold processing circuit 12, where unnecessary noise components are removed as shown in Figure 2, and then passed through the gate circuit 13 as shown in Figure 2C.
When the gate signal of 4. is at a high level, it passes through this gate circuit 13 as shown in FIG. A sample and hold circuit 16 converts the frequency of the pulse into a voltage. The converted voltage is compared with a reference voltage in a speed control device 7, and the rotational speed of the DC motor 2 is controlled. The gate signal applied to the gate circuit 13 is obtained by subjecting the output of the sawtooth wave generator 4 to dark value processing in a second value processing device 14 as shown in FIG. 2e. That is, the sawtooth wave generator 4
The gate circuit 13 is closed while the output voltage is lower than the second threshold level. Therefore, speed control that is not affected by noise can be achieved.

Effects of the Invention According to the present invention, which has been explained by way of examples, noise is removed by the first dark value processing, and unnecessary pulses are suppressed by gate operation of the gate signal created by the second dark value processing. - Capable of voltage conversion and highly stable constant speed control of DC motors.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a DC motor constant speed control device according to an embodiment of the present invention, Fig. 2 is a waveform diagram showing waveforms of various parts in Fig. 1, and Fig. 3 is a conventional FIG. 2 is a block diagram of a DC motor constant speed control device of FIG. 1...Pulse detection device, 2...DC motor, 4.
... Sawtooth wave generator, 7... Speed control device, 12.
...first open value processing device, 13...gate circuit, 14.
...Second open value processing device, 15...Nokurusu shaping device,
16...Sample e-hold circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
figure

Claims (1)

[Claims] A DC motor, a device that detects pulses generated by a commutator of the motor, a waveform shaping device that shapes the detected pulses, and a first threshold processing device that performs threshold processing on the shaped pulses to clip portions below a noise level. a device for generating a sawtooth wave triggered by a gate circuit and a gated pulse; a second threshold processing device for thresholding the sawtooth wave to generate a gate signal for the gate circuit; A DC motor constant speed speed control device consists of a device that samples and holds the voltage, and a device that controls the speed of the DC motor by comparing the held voltage with a reference voltage.