JPS6233837B2 - - 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 driven by switching.

Prior Art First, FIG. 1 shows a specific example of a speed control device for an electric motor constructed according to the prior art, and an outline of its operation will be explained.

In FIG. 1, the output of an alternator C connected to a motor M is applied to a waveform shaping circuit (a), shaped into a rectangular wave, and applied to a trigger pulse generation circuit (b). This rectangular wave signal is here converted into an impulse-like trigger pulse to drive the next-stage monostable circuit C. The output single waveform of the monostable circuit C has a constant time width, and its repetition frequency is the same as the output frequency of the alternator, and depends on the rotational speed of the motor M, so it is passed through the next stage integration circuit D. Therefore, a DC voltage that changes depending on the rotational speed of the electric motor M is obtained. In FIG. 1, blocks I to D, including the alternator G, serve as a rotational speed detector. Therefore, a DC voltage that depends on the rotational speed of the DC motor M is obtained as the output of the integrating circuit 2, and is compared with the reference voltage obtained from the blocking circuit by the first comparison circuit, but the comparison gain is sufficient. If it is assumed that be. The output transistor to the first comparison circuit is in the cutoff region when the output voltage of the integrating circuit 2 becomes larger than the reference voltage, that is, when the rotational speed of the DC motor M rises higher than the preset rotational speed. However, at this time, since no current flows through the output transistor of the second comparator circuit M, the drive transistor is also cut off, and the rotational speed of the DC motor M is reduced.

On the other hand, the output transistor to the first comparator circuit is in the saturation region when the output voltage of the integrating circuit N becomes smaller than the reference voltage, that is, when the rotational speed of the DC motor M is lower than the preset rotational speed. In this case, the output transistor of the second comparator circuit also becomes saturated, and
The drive transistor also becomes saturated and the rotational speed of the DC motor M is accelerated.

Now, in an intermediate state between these, that is, when the rotational speed of the DC motor M is almost maintained at a preset value, in other words, when constant speed control is being performed, the The output transistor is in the active region, and its output current increases or decreases depending on the magnitude of the load on the DC motor M.

Therefore, the base side potential of the output transistor of the second comparator circuit changes depending on the increase or decrease of the output current of the output transistor to the first comparator circuit, and
Depending on the change in the base side potential of the output transistor of the comparison circuit (E), the conduction period of the output transistor of the second comparison circuit (E) becomes longer or shorter during the repetitive cycle of the output signal of the sawtooth wave generating circuit (E). do. For example, when the load on the DC motor M increases, the base side potential of the output transistor of the second comparison circuit N increases, and the conduction period becomes longer.

Therefore, the period during which power is supplied to the DC motor M by the drive transistor becomes longer, and more power is applied to the DC motor.

Problems to be Solved by the Invention As described above, the motor speed control device shown in FIG. There was a problem in that the output torque at the time of starting the motor was impaired by the DC resistance of the connected chiyoke coil.

Means for Solving the Problems In order to solve the above problems, the motor speed control device of the present invention generates an error signal by comparing the output signal of a detector that detects the rotational speed of the motor with a reference voltage. a first drive circuit that drives the electric motor using the output signal thereof;
a signal generation circuit that generates a sawtooth wave with an appropriate repetition frequency; a second comparison circuit that generates a switching signal by comparing the error signal and the sawtooth wave; and a drive current that is smoothed by the output signal thereof. a second drive circuit that drives the electric motor through a choke coil for the purpose of increasing the speed of the electric motor; The electric motor is configured to be driven mainly by a first drive system including the first drive circuit during startup or overload.

Effects According to the present invention, with the above-described configuration, it is possible to realize a device with high efficiency at the time of starting the electric motor.

Embodiment FIG. 2 shows a circuit diagram of the main parts of a motor speed control device in an embodiment of the present invention. Terminal 1 to which the base of transistor 1 is connected
is supplied with the output to the first comparison circuit shown in FIG. In this case, the configuration of the blocks for generating the reference voltage, including the first comparison circuit, waveform shaping circuit A, trigger pulse generation circuit B, monostable circuit C, and integration circuit D, is the same as in Figure 1. shall be.

In Figure 2, the first comparison circuit (shown in Figure 1)
A drive circuit including transistor 1, resistor 2, transistor 3, resistor 4, and transistor 5 (first drive transistor) is connected to output terminal 1 of The base and emitter of a transistor 10 (first-stage transistor constituting the second drive system) are connected via a resistor 9, and the collector of the transistor 10 is connected via a resistor 11 to a positive power supply line. Further, between the positive side power supply line and the negative side power supply line, transistors 12 and 13, resistors 14, 15, 16,
17, a well-known unstable multivibrator is constituted by capacitors 18 and 19, and a circuit is connected between the collector of the transistor 12 and the positive feed line for converting the output rectangular wave of the astable multivibrator into a sawtooth wave. , resistor 20 and capacitor 21
An integrating circuit configured by is inserted.
The base of a transistor 22 is connected to the output side of the integration circuit, the emitter of the transistor 22 is connected to the collector of the transistor 10, and the collector is connected via a resistor 23 to the positive power supply line. Further, the transistor 2
The base of a transistor 24 (second driving transistor) is connected to the collector of the transistor 2, the emitter of the transistor 24 is connected to the positive power supply line via a resistor 25, and the collector is connected to the base of a transistor 26. There is. Further, the emitter of the transistor 26 is connected to a negative power supply line, and is also connected to one power supply terminal of the DC motor 6 through a choke coil 27 for smoothing the drive current. The other power supply terminal of the DC motor 6 is connected to a positive power supply line, and a capacitor 7 is connected in parallel with the DC motor 6. Further, a diode 28 is connected between the collector of the transistor 26 and the positive power supply line.

Note that terminals c and b are positive and negative power supply terminals, respectively.

In FIG. 2, a first comparator circuit is configured by a block (not shown), a transistor 1, and a resistor 2, and a first drive circuit is configured by a transistor 3, a resistor 4, and a transistor 5. A second comparator circuit is composed of a resistor 9, a transistor 10, a resistor 11, a transistor 22, and a resistor 23, and further includes a transistor 24, a resistor 25, a transistor 26, a choke coil 27,
The diode 28 constitutes a second drive circuit T'.

In the device shown in Figure 2, if the comparison gain of the first comparison circuit is made sufficiently large, the collector current of transistor 1 will be a fairly small value when normal closed-loop speed control is performed. , by selecting the value of resistor 9 such that the voltage drop across it does not exceed the base-emitter voltage of transistor 3, so that all of the collector current becomes the base current of transistor 10. I can do it.

At this time, the first drive system is in a cutoff state, and the second drive system including the second comparison circuit (consisting of the second drive circuit T', the sawtooth wave generation circuit H, and the second comparison circuit N) ), the DC motor 6 is switched under control.

On the other hand, when the load on the DC motor 6 becomes overloaded or at startup, the voltage drop caused by the choke coil 27 cannot be ignored, but in this case, the rotational speed of the DC motor 6 becomes lower than the preset value. Therefore, transistor 1 is saturated and its collector current increases rapidly. When the collector current of the transistor 1 increases significantly and the voltage drop caused by the resistor 9 exceeds the forward voltage between the base and emitter of the transistor, the first drive system is activated, and the DC motor 6 is supplied mainly with the transistor 5. Therefore, even if the DC resistance of the chiyoke coil 27 is large, there will be no problem.

Further, even if the second comparison circuit, the second drive circuit, the sawtooth wave generation circuit, etc. fail and the power supply by the second drive transistor 26 is stopped, the first drive transistor 5 maintains the continuous control mode. Since the power is supplied, the rotational speed of the DC motor 6 is kept almost constant.

In FIG. 2, the base of the first drive transistor 5 is connected to the collector of the transistor 1 via the base and emitter of the transistor 3, but instead of the base and emitter of the transistor 3, a diode or the like is connected to the collector of the transistor 1. Exactly the same effect can be obtained by connecting a voltage drop element.

Effects of the Invention As is clear from the above description, the motor speed control device of the present invention includes a first comparison circuit that generates an error signal by comparing the output signal of a detector that detects the rotational speed of the motor with a reference voltage. a first drive circuit that drives the electric motor with its output signal; a signal generation circuit that generates a sawtooth wave with an appropriate repetition frequency; and a switching signal that compares the error signal and the sawtooth wave. a second comparator circuit that generates the second signal, and a second drive circuit that uses the output signal of the second comparison circuit to drive the electric motor via a chiyoke coil connected in series to the electric motor. The electric motor is driven by a second drive system including a circuit, and when the electric motor is started or overloaded, the electric motor is mainly generated by the first drive system including the first drive circuit. Therefore, when the electric motor is started or overloaded, power is mainly supplied to the electric motor by the first drive system that directly drives the electric motor without passing through the electric motor coil, and the electric power is supplied to the electric motor by the first drive system that directly drives the electric motor without using the electric motor through the electric motor. It is possible to prevent a decrease in the maximum power supplied to the motor due to DC resistance, and on the other hand, if the comparison gain of the first comparison circuit is made sufficiently large, switching drive can be performed only by the second drive system during normal operation. , it is possible to realize an extremely efficient device with great effects.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional motor speed control device, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. M...Electric motor, G...Alternator, A...Waveform shaping circuit, B...Trigger pulse generation circuit, C...
Monostable circuit, D... Integrating circuit, E... Sawtooth wave generation circuit, F... First comparison circuit, G... Drive circuit, G'... Second drive circuit, R... Reference voltage generation Circuit, N... Second comparison circuit, L... First drive circuit, 5... First drive transistor, 9...
...Resistor, 10...First-stage transistor constituting the second drive system.

Claims (1)

[Claims] 1. A detector for detecting the rotational speed of an electric motor, a first comparison circuit for generating an error signal by comparing the output signal of the detector with a reference voltage, and a sawtooth-shaped circuit having an appropriate repetition frequency. a signal generation circuit that generates a wave; a second comparison circuit that generates a switching signal by comparing the error signal and the sawtooth wave; and an output signal of the first comparison circuit to drive the electric motor. a first drive circuit; and a second drive circuit that drives the motor via a chiyoak coil connected in series to the motor according to the output signal of the second comparison circuit; The electric motor is driven by a second drive system including two drive circuits, and when the electric motor is started or overloaded, the electric motor is mainly driven by a first drive system including the first drive circuit. A speed control device for an electric motor, characterized in that it is configured as follows. 2 Connect the output side of the first comparison circuit between the base and emitter of a transistor or the base and emitter of the first driving transistor via a voltage drop element such as a diode, and connect the base and emitter of the first driving transistor via a resistor. A second comparator circuit connects the base and emitter of the first stage transistor constituting the drive system, compares the output signal of the first stage transistor with a sawtooth wave, and connects a second drive circuit to the output side of the second comparator circuit. 2. A speed control device for an electric motor according to claim 1, further comprising a transistor connected thereto.