JPH01318569A - Speed control circuit - Google Patents

Abstract

PURPOSE:To secure a torque at low speed by setting characteristics of a speed feedback circuit to broken line-shaped characteristics. CONSTITUTION:A speed signal 1 is converted into a voltage by an F/V converter 2 to obtain a revolution signal Va. An offset circuit 3 outputs a signal when the revolution signal Va reaches a given voltage. An inverting amplifier circuit 4 inverts the output of the offset circuit 3 into Vb on the basis of the revolution signal Va and amplifies Vd to output a voltage Vc. A differential amplifier circuit 5 outputs a deviation signal Vd between the output Vc of inverting amplifier circuit 4 and a speed control voltage Vref determined by a speed regulating variable resistor 6. Further, a comparison PWM circuit 8 compares a reference triangular wave outputted from a reference triangular wave generator circuit 7 with the deviation signal Vd to output PWM pulse to a control circuit 9. In this manner, it is possible to secure a torque at low speed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a speed control circuit that feeds back the speed of an electric potter's wheel, an electric winch, etc., such as speed reduction due to load fluctuation, to a control circuit.

[Conventional technology]

Conventionally, speed control circuits include those that control the speed using a voltage that determines the speed, that is, those that do not perform feedback control, and those that perform feedback control, and when the speed decreases due to the load, feedback is applied to increase the speed. The output voltage of the F/V converter was proportional to the rotational speed as shown in FIG. 8, and the amount of feedback was the same over the entire speed range.

[Problem to be solved by the invention]

Conventional speed control circuits that do not have feedback control have the problem that the speed decreases when a load is applied, and even in those that perform feedback control, the amount of feedback is the same over the entire speed range, so it is difficult to operate at low speeds. The problem was that it would not rotate under the load, resulting in a sagging condition. The present invention has been made in view of this point, and its purpose is to make the amount of feedback variable to ensure torque in a low speed range.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an F/V converter that converts a speed signal into a voltage, an offset circuit that does not output until the output of the F/V converter reaches a certain voltage, and an output of the F/V converter. and an inverting amplifier circuit that inverts the output of the offset circuit with reference to , and the linear signal of the inverting amplifier circuit is fed back to change the amount of feedback.

[Effect]

The speed control circuit configured as described above can secure a large amount of feedback in the low-to-medium speed range, and can secure torque at low speeds without becoming locked against load fluctuations.

【Example】

Examples will be explained with reference to the drawings. In Figure 1,
A speed signal 1 (frequency) is converted into a voltage by an F/V converter 2 to obtain an output voltage Va with respect to the rotational speed as shown in FIG. Offset circuit 3 is a constant voltage determined by the circuit.
Therefore, the output of the offset circuit 3 becomes the voltage vb shown in FIG. 2. The inverting amplifier circuit 4 connects the output of the F/V converter 2 and the offset circuit 3.
The output of the offset circuit 3 is inverted with respect to the output of the F/V converter 2 to obtain vb', which is amplified to output the voltage Vc shown in FIG. The differential amplifier circuit 5 compares the output Vc of the inverting amplifier circuit 4 with the speed control voltage V ref determined by the speed adjustment variable resistor 6, and outputs it based on the formula V rJ - V ref + (V ref - Vc). Output Vd. If a load is applied while it is rotating, the rotational speed will decrease and the output Vc of the inverting amplifier circuit 4 will decrease.
decreases, and the output Vd of the differential amplifier circuit 5 increases. The reference triangular wave generation circuit 7 generates a reference triangular wave V as shown in FIG. 3(a).
This reference triangular wave Ve and the output d of the differential amplifier circuit 5 are manually inputted to the comparison PWM generation circuit 8. Vd>V
e, the output Vf of the comparison PWM generation circuit 8 is as shown in FIG.
As shown in b), when the output Vf is turned on and Vd<Ve, the output Vf is turned off and a PWM pulse is generated, which is input to the control circuit 9 having a switching control element. When a load is applied, the output Vcl of the differential amplifier circuit 5 rises, and the ON time of the comparison PWM generation circuit 8 becomes longer, thereby performing a feedback function. Here, if the output of the inverting amplifier circuit 4 is made into a polygonal line, it will have a steep slope in the low and medium speed range, and a large output Vd of the differential amplifier circuit 5 can be secured, increasing the amount of feedback to ensure low speed torque. can. Next, since the output Vc of the inverting amplifier circuit 4 input to the differential amplifier circuit 5 is linear, the relationship between the speed control voltage V ref and the rotation speed has the characteristics shown in FIG. 4. A wide range of low and medium speeds can also be secured. That is, the speed control voltage V ref is in a proportional relationship with the slide stroke of the speed adjustment variable resistor 6 as shown in FIG.
f is differentially amplified so that Vref-Vc=Vd, and the output Vd becomes as shown by the broken line in FIG. 6, and the relationship between the speed control voltage Vref and the rotational speed becomes as shown in FIG. 4. Furthermore, when the output Vcl of the inverting amplifier circuit 4 is in the state shown in FIG. 7, the offset voltage 3 and the circuit voltage of the inverting amplifier circuit 4 are switched higher by the switch 10 to increase the gradient of the linear voltage as shown in FIG. 7 Vc2. By doing so, the amount of feedback by the differential amplifier circuit 5 can be increased.

【Effect of the invention】

Since the present invention is configured as described above, the feedback amount can be made variable, the feedback amount can be increased in the low and medium speed range, the torque at low speed can be secured, and the low and medium speed range can be widened. It is something that plays.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, FIG. 2 is a characteristic diagram of the same as above, FIG. 3 is an operation time chart of the same as above, FIGS. 4 to 7 are characteristic diagrams of same as above, and FIG. is a characteristic diagram of a conventional example. 1 is a speed signal, 2 is an F/V converter, 3 is an offset circuit, 4 is an inverting amplifier circuit, and 9 is a control circuit. Agent Patent Attorney Ishi 1) Ai Seven 1g Hato 1ml QoA”-wGhada 5-day

Claims (1)

[Claims] (1) In a speed control circuit configured to feed back speed signals such as speed reduction due to load fluctuations to the control circuit for control, an F/V converter that converts the speed signal into voltage;
an offset circuit that does not output an output until the output of the F/V converter reaches a certain voltage; and an inverting amplifier circuit that inverts the output of the offset circuit based on the output of the F/V converter, A speed control circuit characterized in that it is configured to feed back a polygonal output and change the amount of feedback.