JPS61258692A - Speed controller of dc motor - Google Patents

Abstract

PURPOSE:To reduce a reactive current by additionally connecting the second resistance element between the first load variation setting resistance element and a reference voltage source, and connecting the third resistance element between input terminals of a differentiator. CONSTITUTION:A speed setting resistor 4 is connected between a load variation setting resistor 2 and a reference voltage source 5, and a resistor 3 is further connected between the connecting point of a reference voltage source 5 and the resistor 4 and one input terminal of a differentiator 6. The differentiator 6 compares a voltage generated at the resistor 4 and the source 5 with the counterelectromotive force of a DC motor 1, and drives output transistors 7, 8 of current mirror structure by the output. With such a construction, a speed controller of the DC motor which can readily regulate with less number of parts with less reactive current and improve the load variation characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speed control device for a DC motor used as a drive source for audio equipment and the like.

2. Description of the Related Art Conventionally, a speed control circuit for a DC motor of this type has a configuration as shown in FIG. In Fig. 3, 1 is a DC motor, 2 is a fixed resistor for setting load fluctuations, 3 is a speed adjustment resistor, 5 is a reference voltage source, 6 is a differential circuit, 7 and 8 are currents connected to the resistor 2 and the DC motor 1. 9 is a DC power supply.

In the speed control circuit for a DC motor as described above, when the rotation speed of the DC motor changes due to changes in the load, the back electromotive force generated in the motor changes, and this change is converted into a reference voltage by the reference voltage source 50 in the differential circuit 6. By comparison, the output transistor 7.8 is controlled by the output to control the rotational speed of the DC motor to be constant. Here, the back electromotive voltage of the DC motor is Ea1, the internal resistance of the motor is Ra%, the voltage value of the reference voltage source is vref, the resistance 2 is
The values of resistor 3 are respectively RT and R1, and ■a,
it.

is, 12. lk is a current flowing through each arrow position. Here, lk is configured so that the negative current of I2 always flows through the current mirror circuit. At this time, the voltage vO applied to the DC motor is RT I
RT = V + - I self
... is given by (2). Here, if the resistance values Rj and RT are given, the first term on the right side of the first equation takes a constant value regardless of changes in the power supply voltage, load torque (motor current 1 m), etc., and the second term on the right side changes in proportion to 1 m of motor current.

On the other hand, considering a DC motor, if the terminal voltage of the DC motor is Vll, then Vm=Ea+Re
Is-(
3), so in Fig. 3, VO−Vm
-(4), RT V + I a= Ea+ Ra Is
”The relationship shown in (5) is obtained. Therefore, the back electromotive force E- of the DC motor is expressed as follows.

From this, by adjusting the resistance RT, RT=KR...a)
If we choose E a = V
...(8), and the DC motor 1 is driven at a rotational speed such that its back electromotive force E is always a constant voltage V. That is, the DC motor 1 maintains a constant rotational speed without being affected by the load torque.

In other words, if the rotational speed of DC motor 1 is N1 and the power generation constant is, then E * = K - N
...(9), and corresponding to the internal resistance Ra of the DC motor 1,
If the resistance value RT is selected as RT=KR-...GD, then the DC motor 1 is not affected by the motor current 1a, that is, the load torque, and has a constant rotation speed.

The above is the operating principle of the DC motor speed control circuit shown in FIG.

Problems to be Solved by the Invention Incidentally, in the speed control circuit for a DC motor as described above, the rotational speed N of the DC motor 1 can be set by changing the resistance value R of the speed adjustment resistor 3 in FIG. It was set. However, as is clear from equation 0, in the speed adjustment method described above, the relationship between the rotation speed N and the resistance R1 is inversely proportional. becomes a hyperbola, making it extremely difficult to adjust the rotation speed. Furthermore, when setting the rotation speed of the DC motor to a high rotation speed that increases the back electromotive force E, the resistance value Rj becomes small, and therefore the resistance Rs
Since the reactive current is flowing through the motor and does not contribute to the torque generated by the motor increases, it has the disadvantage that it cannot be used in a multi-speed motor that needs to be set at a high rotation speed.

In addition, in this type of DC motor speed control device,
Conventionally, as shown in Japanese Patent Application Laid-Open No. 53-142611, a resistance element having a positive temperature coefficient equivalent to that of the motor winding of the DC motor 1 has been used as the load variation setting resistor 2 for the purpose of improving load variation characteristics. However, in conventional speed control devices, if a resistor with a positive temperature gradient is used for resistor RT, as is clear from equation 0 above, the rotational speed N will also be large relative to the ambient temperature. It had the disadvantage of being variable.

The present invention solves the problems of the conventional method.The present invention provides a direct current motor with a low reactive current, a linear relationship between the rotation speed and the resistance value of the speed adjustment variable resistor, and the speed adjustment of which is easy. The object of the present invention is to provide a control device, and also to provide a speed control device for a DC motor that can improve the above-mentioned temperature characteristics of the rotational speed.

Means for Solving the Problem In order to solve this problem, the present invention additionally connects a second resistance element between the first resistance element for load fluctuation setting and the reference voltage source, and A third resistance element is connected between the input terminals of the dynamic circuit, the third resistance element is a fixed resistance, and the second resistance element is connected between the input terminals of the dynamic circuit.
The speed is adjusted by using the resistance element as a variable resistor.

Function: In the speed control circuit for a DC motor having this configuration, the voltages at both input terminals of the differential circuit are controlled at the same potential during control operation. Therefore, the voltage value ' of the reference voltage source is applied to the third resistance element.
Fixed current is, which is J ref divided by its resistance value Rs t
flows, and the current is also flows through the second resistive element, thereby generating a reference voltage across the second resistive element and increasing the rotational speed of the DC motor 1 to a rotational speed corresponding to the generated reference voltage. Control. Therefore, the rotation speed of the DC motor is proportional to the reference voltage generated in the second resistance element, and by using a variable resistor as the second resistance element, the relationship with the rotation speed N becomes linear, making it easy to adjust the rotation speed. Become.

Embodiment FIG. 1 is an electrical circuit diagram of a speed control device for a DC motor according to an embodiment of the present invention. In FIG.
A DC motor 1 having a back electromotive voltage Ea is connected, and a speed setting resistor 4 is connected between the load fluctuation setting resistor 2 and a reference voltage source 5, and a speed setting resistor 4 is connected to the connection point between the reference voltage source 5 and the resistor 4. A resistor 3 is provided, one end of which is connected, and the other end of which is connected to one input terminal of the differential circuit. A differential circuit 6 connects a voltage generated in a resistor 4 and a reference voltage source 5 to a DC motor 1.
The back electromotive voltages of the two are compared, and the output transistors 7 and 8 of the current mirror configuration are driven by the output.

In the above circuit, the resistance values of resistors 3 and 4 are set to R3, respectively.
I, Rj2, and further I"+ 1"+ I2+
Assuming that IK is a current flowing at each arrow position, and that IK is configured so that - current of (2) flows as in the conventional example in Fig. 3, the current flowing through resistor 3 is l s = V r @ f / RS I...■
Therefore, ■s also flows to the resistor 4, so the reference voltage V generated across the resistor 4 is Vsi= vref @R82/Rsl
...QIQ, and the rotation speed N of the DC motor is +Ia(-Re)] ...■. Here, corresponding to the internal resistance R11 of the DC motor, if the resistance value RT is selected as RT=KRa... (to), then the DC motor 1 is not affected by the motor current I3, that is, the load torque, and is constant. rotation speed.

In the present invention, as is clear from Equation 0, by setting the rotation speed by using a variable resistor as the resistor 4, the relationship between the resistance Rj2 and the rotation speed N is directly proportional and linear, so that the rotation speed can be adjusted. Adjustment work becomes easier. Furthermore, when setting the rotational speed to a high rotational speed, it is sufficient to simply increase the resistance Rj2, so that the reactive current does not increase. Furthermore, compared to the conventional example [F] formula, the 0 formula has a smaller ratio of R in the term on the right side that determines the rotational speed N, so the resistance RT is adjusted to improve the load fluctuation characteristics. Even when using a resistive element with a positive temperature gradient, the temperature change in rotational speed can be small.

In addition, in order to correct the temperature change that occurs in the power generation constant due to the temperature change of the magnetic flux of the motor magnet as a temperature change in the motor rotation speed N, in the conventional example, the resistor 3 is replaced with a resistance element having a positive temperature coefficient. , or by connecting a temperature compensation diode in series with resistor 2 to correct the temperature of the rotation speed, but in the present invention, similarly, by using a resistance element with a positive temperature coefficient for resistor 3, Furthermore, as shown in the embodiment of FIG. 2, it is clear that by connecting a temperature correction diode 10 in series with the reference voltage source 5, temperature correction of the rotational speed becomes possible.

Effects of the Invention As described above, according to the present invention, a second resistance element (resistance 4 in the embodiment) is added between the first resistance element (resistance 2 in the embodiment) and the reference voltage source, and By using a variable resistor as the second resistance element to adjust the speed of the DC motor, the adjustment work is easy with a small number of parts, there is little reactive current, and the rotational speed is improved with improved load fluctuation characteristics. This type of speed control device can achieve extremely excellent effects by minimizing temperature changes.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit wiring diagram of a speed control device for a DC motor according to an embodiment of the present invention, and FIG. 2 is an electrical circuit diagram of a speed control device for a DC motor according to another embodiment of the invention.
FIG. 3 is an electrical circuit diagram of a conventional speed control device for a DC motor. 1...DC motor, 2...Load fluctuation setting resistor, 3...Resistor (third resistance element), 4...
...Resistor (second resistance element) 5...Reference voltage source, 6...Differential circuit, 7, 8...
Output transistor, 9...DC power supply. Name of agent: Patent attorney Toshio Nakao and 1 other person 5 Standard 4
T, x field!・・i Video path 7.1・ Output transistor Fig. 2

Claims (5)

[Claims] (1) A DC motor connected between the collector of a first transistor and a power supply terminal, and the collector and power supply terminal of a second transistor whose bases are commonly connected to the first transistor to form a current mirror circuit. one input terminal is connected to one end of the reference voltage source and the other input terminal is connected to a common connection point between the DC motor and the collector of the first transistor; a differential circuit that compares and amplifies the voltage difference between both inputs and outputs a comparison output to the first and second transistors that supply current to the first resistance element and the DC motor; A second resistance element is connected between the other terminal of the voltage source and the first resistance element, and a third resistance element is further connected between the other input terminal of the differential circuit. DC motor speed control device. (2) A speed control device for a DC motor according to claim 1, wherein a resistance element having a positive temperature coefficient is used as the first resistance element. (3) A speed control device for a DC motor according to claim 1, wherein a variable resistor for speed adjustment is used as the second resistance element. (4) A speed control device for a DC motor according to claim 1, wherein a resistance element having a positive temperature coefficient is used as the third resistance element. (5) A speed control device for a DC motor according to claim 1, wherein a constant voltage element having a negative temperature coefficient is connected between the second resistance element and the reference voltage source.