JPH02123987A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To enable an economical DC stabilizing power source to be used by detecting line voltage, and by applying it to the adding point of an adder circuit with a constant gain. CONSTITUTION:By a voltage detecting circuit 10, the voltage of a mo tor power source 9 is converted to a signal level and is applied to the adding point of an adder circuit 5 with a constant gain. Even if the voltage of the motor power source 9 is fluctuated due to this composition, a voltage level corresponding with the change component of the characteristic of a motor 7 itself due to a voltage difference is corrected by the change component of the voltage of the power source 9, and so the voltage fluctuation of the motor power source 9 is hardly influenced by a phase output waveform, and as its result, a phase- locked loop lock range can be sufficiently widened, and so by the motor power source 9, the voltage fluctuation is not required to be severely limited. As a result, an economical DC stabilizing power source can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speed control device for a motor used to drive a copying machine or the like.

2. Description of the Related Art In recent years, many small DC motors have been used in office automation equipment such as copying machines, and most of them are phase-locked loop (PLL) motors.
High-precision speed control is applied. A DC stabilized power source is used as a power source for these devices, but its performance is comparable to that of a PLL.

Hereinafter, a conventional electric motor speed control device will be described.

FIG. 5 shows a conventional speed control device for an electric motor. In FIG. 5, 1 is a waveform shaping circuit that shapes the output waveform of frequency power generation n8 added to the motor 7, and 2 is a frequency-voltage conversion circuit (hereinafter referred to as 4 is a phase comparison circuit that compares the phases of the clock signal of the reference clock generation circuit 3 and the output of the waveform shaping circuit 1 and outputs the phase difference.

5 is an adder circuit that adds the outputs of the F/V circuit 2 and the phase comparator circuit 4 at a constant gain ratio, and 6 is an adder circuit that amplifies the output of the adder circuit 5 and controls the motor power supply 9 to adjust the speed of the motor 7. This is a power amplifier circuit to control.

In the power amplifier circuit 6, 6-a is a transistor for power control, and 6-b is a flywheel diode, and only these are directly connected to the motor power supply.

The operation of the speed control of the electric motor configured as described above will be explained below.

In this circuit that constitutes the PLL control circuit, the F/V circuit 2 provides damping to the system, and the output is constant during PLL control, and the output of the phase comparator circuit 4 responds to changes in load, etc. The output level of the adder circuit 5 is changed to control the power control transistor 6a to control the voltage applied to the motor 7, and as a result, the speed of the motor 7 is controlled at a constant speed in synchronization with the reference clock. .

Problems to be Solved by the Invention However, in the conventional configuration described above, when the voltage of the motor power supply 9 has large fluctuations, the unique characteristics of the motor change, so the phase comparison output changes regardless of the load and the PL
There was a gap that narrowed the L lock range, and it was necessary to suppress voltage fluctuations of the motor power supply 9.

The present invention solves the above-mentioned problems of the conventional technology, and uses a relatively wide voltage fluctuation (while using an inexpensive DC stabilized power supply as a motor power supply,
An object of the present invention is to provide a speed control device for an electric motor that can secure a lock range.

Means for Solving the Problems To achieve this object, the motor speed control device of the present invention has a voltage detection circuit that detects the voltage of the motor power supply and applies it to the addition point of the addition circuit with a constant gain. are doing.

Effect With this configuration, even if there is a fluctuation in the voltage of the motor power supply, the voltage level corresponding to the change in the characteristics unique to the motor due to the voltage difference is corrected by the change in the power supply voltage, so the phase output waveform is Voltage fluctuations have almost no effect,
As a result, the PLL lock range is sufficient, so the motor power supply does not have to strictly limit voltage fluctuations (an inexpensive DC stabilized power supply can be used).

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a speed control device for an electric motor in an embodiment of the present invention. Since 1 to 6 in FIG. 1 are the same as those in FIG. 5 of the conventional example, explanations thereof will be omitted.

A voltage detection circuit 10 converts the voltage of the motor power source into a signal level and applies it to the addition point of the addition circuit 5 with a constant gain. FIG. 2 is a detailed diagram of the voltage detection circuit 10 and the addition circuit 5. In FIG. 2, 5-a indicates a reference voltage. Figure 3 shows the speed-torque (n-T) characteristics of the electric motor.
Voltages V+, vo, v-c at constant load torque TO: rotation wheel n + .

It represents no, n-. nI is the rotation speed of PLL control. Figure 4 shows the phase comparison output, (a),
(b), (c) Lt each voltage V of motor power supply 9
It represents the waveform at O, V+V-.

The operation will be explained below.

As shown in Fig. 3, for the same load torque TO, if the voltage of the motor power supply 9 varies from 10 to V- with respect to the rated vO, then the unique characteristics of the motor 7 which is not controlled are n to no. It changes from ÷ to n-. Therefore, in order to maintain a constant speed with respect to the load TO, the voltage applied to the motor does not change, so the power transistor 6-a must have the voltage difference. This means that the gain of the power amplifier circuit 6 increases as the voltage of the motor power source 9 increases, and decreases as the voltage decreases. Therefore, the output level of the adder circuit 5 changes. It is now assumed that the output voltage level of the output of the adder circuit 5 increases as the load increases. Motor power supply voltage 9 is ΔV (
=V+-VO), the output voltage level of the adder circuit will fall by ΔV/G. However, G indicates the gain of the power amplifier circuit.

If the voltage detection circuit 10 is not provided, the output of the F/V circuit 2 is constant at constant speed, so the output of the phase comparison circuit changes to correspond to the change in the output voltage level of the adder circuit.

At this time, the output change amount Δup of the phase comparison circuit 4 is ΔUp=
It is given by R5/R7X ΔV/G, and the phase output width increases as shown in FIG. 4(b).

If the motor power supply 9 decreases as V-, the phase output will conversely decrease as shown in FIG. 4(C).

When the voltage detection circuit 10 is provided, when the voltage of the motor power supply 9 increases by ΔV, the output of the voltage detection circuit 10 decreases by R2/(R1+R2>XR4/R3XΔV. This voltage becomes the output increase numerator Δup of the phase comparator circuit 4. That is, R2/(RI+R2)XR4
By selecting a constant given by /R3XR7/R6=1/G, the output width of the phase comparison output can be made independent of fluctuations in the motor power supply.

As described above, according to this embodiment, by providing the voltage detection circuit, the PLL lock range can be maintained regardless of fluctuations in the motor power supply.

Effects of the Invention As described above, the present invention, by providing a voltage detection circuit for the motor power supply, can extremely suppress the reduction in the PLL lock range due to fluctuations in the motor power supply, making it easy to use an inexpensive DC stabilized power supply. Can be used.

■ Since fluctuations in the motor power supply can be almost ignored, adjustments and inspections in the manufacturing process become easier.

This makes it possible to realize an excellent motor speed control device such as the following.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a motor speed control device in an embodiment of the present invention, Fig. 2 is a circuit diagram of the voltage detection circuit and addition circuit of Fig. 1, Fig. 3 is a motor characteristic diagram, and Fig. 4 is a phase diagram. The output waveform diagram of the comparator circuit is shown in FIG. 5, which is a block diagram of a conventional motor speed control device. 1... Waveform shaping circuit, 2... Frequency -
Voltage conversion circuit, 3...Reference clock generation circuit,
4...Phase comparison circuit, 5...Addition circuit, 6...Power amplifier circuit, 7...Motor, 8...Frequency power generation machine, 9...motor power supply, 10...voltage detection circuit. Diagram No. 1

Claims (1)

[Claims] A waveform shaping circuit that shapes the output waveform of a frequency generator attached to the motor, a frequency-voltage conversion circuit that converts the output of the waveform shaping circuit into voltage, and a phase that compares the output of the waveform shaping circuit with a reference clock. a comparison circuit, an addition circuit that adds the outputs of the frequency-voltage conversion circuit and the phase comparison circuit, and a power amplifier circuit that amplifies the output of the addition circuit, controls the motor power supply, and supplies power according to the speed; A speed control device for a motor, comprising a voltage detection circuit that detects the voltage of the motor power source, and adding an output of the voltage detection circuit to the addition circuit.