KR830002150Y1 - Speed control device of small DC motor - Google Patents

Abstract

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Description

Speed control device of small DC motor

1 is a circuit diagram showing a small DC motor control device using a conventional three-terminal speed control IC.

2 is a circuit diagram showing a speed control device for a small direct current motor according to the present invention.

Figure 3 is a signal transmission line showing the flow of control of the speed control device of a small DC motor according to the present invention.

4 is a relationship between the rotational speed and the load torque when the control is applied.

5 is a circuit diagram showing a second embodiment of a speed control device according to the present invention.

6 is a relationship between the rotational speed and the load torque of the second embodiment.

7 to 9 are circuit diagrams showing a third embodiment of a speed control apparatus according to the present invention.

10 to 13 are circuit diagrams showing a fourth embodiment of a speed control apparatus according to the present invention.

The present invention relates to a device for controlling the rotational speed of a small DC motor using a speed control IC.

In general, a DC motor having a field is represented by an equivalent circuit in which the internal resistance (R _o ) and the reverse electromotive force (E _o ) induced by the rotation of the DC motor are connected in series.

Now, when the rotational speed of DC motor is N and Z is the number of windings (ø) of the wire wound around the armature, the magnetic flux (K ₂ ) generated from DC motor is proportional constant. ) And the counter electromotive force (E _o )

E _o = NK ₂ Zø (1)

Further, when the current flowing through the DC motor is the load torque of the I _a DC motor as T _d , the following relational expression is established between the load torque T ₄ and the current I _d .

T _d = K ₁ ZøI _a (2)

If the terminal voltage generated at both ends of the DC motor is set to V _m , the following relation is established between the counter electromotive force E _o , the current I _a , and the terminal voltage V _m .

V _m = E _o + R _o I _a (3)

And when this formula (3) is deformed, the following formula (3 ') is obtained.

E _o = V _m -R _o I _a (3 ')

As is apparent from Eq. (3), the electromotive force E _o depends on the current I _a flowing in the dc motor.

In this way, since the electromotive force E _o fluctuates due to the fluctuation of the current I _a flowing in the direct current motor, the rotational speed N apparently fluctuates in Equation (1).

And apparently in the expression (2), the current I _a is changed by the load torque T _d .

Therefore, in order to keep the rotational speed N constant regardless of the change of the load torque T _d , -R _o I of the formula (3 ') according to the terminal voltage (V _m ) of the above formula (3'). It can be seen that it is good to make _a cancel a.

In other words, if a voltage depleting -R _o I _a is applied to both ends of the DC motor, the DC motor can obtain a constant rotational speed regardless of the load change and can control the rotational speed.

Conventionally, the principle described above is known and the circuit shown in FIG. 1 is an example of the speed control apparatus of the small DC motor which applied this principle.

In Fig. 1, reference numeral 1 denotes speed control I _c , R _t , and R _s , respectively, resistors Q ₁ and Q ₂ are transistors, ① is input terminal pin, ② is output terminal pin, and ③ is reference terminal pin. Mark each.

In addition, I _a, I _t is the current flowing in the portion indicated by the arrow in the middle respectively, R _o is the internal resistance of the equivalent circuit of a DC Motor, R _o is the counter electromotive force of the equivalent circuit, Eref is the voltage reference, Vcc is the power supply voltage , I _a denote the error detection circuit, respectively.

In the speed control device equipped with the three-terminal speed control IC 1, the voltage E _s applied to the DC motor is

_{E s = Eref + (Eref /} R s) · R r + R t · I a / K (4)

Becomes

On the other hand, the terminal voltage (V _m ) generated at both ends of the DC motor is V _m = E _o + R _O I _a in formula (3), so the terminal voltage (V _m ) of the DC motor and the voltage applied to the DC motor The following equation is obtained by (E _s ).

E _o = Eref + (Eref / R _s ) · R _t + (R _t / KR _o ) I _a (4 ')

The following formulas are obtained by the formulas (4 '), (1) and (2).

In the equation (5), since Rt is related to both of the first and second terms, the load characteristic indicated in the second term changes by changing the resistance R _t to the no-load rotational speed indicated in the first term. It becomes hard to perform rotation speed adjustment.

In addition, for example, in the temperature compensation of the load characteristic, since the internal resistance (R _o ) has a negative temperature coefficient of static magnetic flux, if the resistance (R _t ) has a positive temperature coefficient, Since the denominator and the numerator are both small with respect to the rise, the change in the second term becomes a temperature compensation of the load characteristic. However, because the denominator becomes smaller with respect to the temperature rise but the numerator becomes larger, the first term becomes larger and the no-load rotation speed becomes no temperature compensation.

In order to correct such a defect, the present invention can set an arbitrary rotational speed only by changing the partial pressure ratio of the voltage dividing circuit without being affected by the resistance (R _t ), and furthermore, the temperature compensation and the change in the rotational speed are simple and reliable. It is to provide a speed control device for a small DC motor that can be performed.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In Fig. 2, the speed control IC 10 of the DC motor has a detection terminal ② output terminal ③ for detecting the equivalent voltage of the reference terminal ① and the counter electromotive force E _o and a terminal ④ grounded.

In the following description, for convenience, terminals ① to ④ will be referred to as first, second, third, and fourth terminals, respectively.

And this is the collector, the emitter of the first of the terminals ① and ④ a fourth terminal of a transistor (Q ₁₎ for classification between are connected through the forward resistance (R _1).

The collector of the plurality of driving transistors Q ₂ to Q _{n is} provided between the third terminal ③ and the fourth terminal ④. The emitter is turned in turn to each resistor R ₂ ... Each is connected via R _n .

And these transistors Q ₁ , Q ₂ . Each base of Q _n is connected to the output terminal of the error detection circuit 10a, respectively.

For example, a differential amplifier is used for the error detection circuit 10a, and a reference voltage source Eref is provided between the input terminal B of the differential amplifier and the first terminal ①.

In addition, the input terminal C of this differential amplifier is connected to the second terminal ②.

Thus, it is comprised by the speed control IC 10 which has four terminals.

Next, the configuration of the external circuit element 20 will be described. A DC motor M is connected between the power supply terminal Vcc and the third terminal ③, while a resistor R _t is connected between the power supply terminal Vcc and the first terminal ①. Again, the first terminal ① and a third terminal ③ is connected to the resistance (R _a) (R _b) series.

Resistance _{(R a), (R b} ) may be a voltage divider circuit, the divided point of the resistor (R _a) and the resistor (R _b) are connected to the terminal ② of the second.

When the speed control device of the small DC motor is constituted in this way, the current I _a flowing in the DC motor M becomes K times the current I _p flowing in the resistor R _t .

_{I a = K · I p (} 6)

In addition, the resistor R _t flows a minute bias current for operating the IC 10 to I _r , _a minute current flowing through the resistors R _t , R _a , and R _b (I _s ). Shall be.

Here, since it is regarded as a short state between the input terminals B and C, the following equation is obtained.

I _s = Eref / R _a (7)

In addition, since the currents I _p , I _s , and I _r flow through the resistor R _t , the voltage V _AB between the power supply terminal Vcc and the input terminal B of the error detection circuit 10a. Is given by

V _AB = Eref + (I _s + I _r + I _p ) · R _t (8)

Since (I _s ) and (I _r ) are finely set compared to (I _t ) in (8), it can be modified in the following manner.

_{V AB = Eref + I p ·} R t (8 ')

On the other hand, the voltage V _AC between the power supply terminal Vcc and the input terminal C of the error detection circuit 10a, that is, the voltage V _AC of the series circuit composed of the DC motor M and the resistor R is a resistance. Since the current I _a flows in (R _o ) and the current I _s flows in the resistor R _b , it is given by the following equation.

_{V AC = E o + I a} · R o -R b I s (9)

Deformation using the formulas (9) and (7),

_{V AC = E o R o ·} I a -R b · Eref / R a (9 ')

You can get the expression.

Since V _AB is the same as V _AC , the following equations can be obtained from equations (8 ') and (9').

_{E o = Eref (1 + R} b .R a) + I p · R t -I a R o (10)

If I _p in the formula (10) is erased using the formula (6), the following formula is obtained.

E _o = Eref (1 + R _b / R _a ) + (R _t / KR _o ) I _a (11)

When (1) and (2) are applied to (11), the following equations can be obtained.

Equation (12) can also be obtained by

That is, formula (1), formula (2), formula (3), formula (6), formula (7), formula (8), formula (9) and motor torque (T _m ) and rotation speed (N). The signal transmission line (figure 3) is drawn by the relation between N = T _m / J _s and I = (V _AB -V _AC ) g _m , whereby the reference voltage Eref (S) is rotated. Relation with speed N (S).

And relationship between load torque T _d (S) and rotational speed N (S)

In these modes, the expression (12) described above can be obtained if the Laplus conversion element S = 0 and the sandwiched g _m → ∞.

Thus, in the present embodiment, as shown in equation (12), the resistance R _t is related only to the second term, so the load characteristic is adjusted to R _t and the no-load rotational speed is the resistance regardless of the resistance R _t . It can be adjusted by the ratio between (R _a ) and (R _b ), so it is easy to adjust the rotation speed. Moreover, the temperature compensation can be done independently.

The reference voltage source Eref may be connected between the second terminal 2 and the input terminal C of the error detection circuit 10a. Here, when the temperature coefficient of the resistance (R _a ) and the resistance (R _b ) is different from each other, the following effects are important. That is, the resistance (R _a) the temperature coefficient resistance (R _b) If you set to be larger than the temperature coefficient of the magnetic flux (12), even if (ø) was reduced by temperature increase of the R _b / R _a included in the denominator can be reduced by increasing the temperature, so the fluctuation of the magnetic flux (ø) included in the denominator and the resistance ratio R _b / R _a contained in the numerator are canceled each other, so that no load is applied. If not, the rotation speed N can be made constant with respect to the temperature rise.

Referring to the case where the temperature coefficient of the resistor R _b is set to be larger than the temperature coefficient of the resistor R _a , the solid line in FIG. 4 shows that R _t / K is smaller than R _o at the temperature t but is very close to the value. The graph of the rotational speed (N) and the load torque (T _d ) at the time of setting is displayed.

Theoretically, R _t / K = R _o can be set to R _o such that, but in practice R _t / K = because approximately the R _t is set such that R _o rotation speed (N) is a little according to the change in load torque Is affected.

Here, when the temperature t rises to the temperature t + α, the rotational speed N when temperature compensation is not performed is represented by a graph indicated by a dotted line.

For example, the 'case of using a DC Motor with _(a load torque (T load torque T), the rotational speed of the case which does not perform the temperature compensation according to _d) is an (N, _o).

When the temperature compensation is performed, the first term of formula (12), Since the resistance R _b / R _a contained in increases with temperature rise Increases further.

The rotational speed N in this case is a graph of a single pointed wire.

Therefore, the load torque (T _'d) Even in the rose at a temperature (t) to (t + α) load torque (T' the rotational speed (N) of the temperature (t + α) in the _d) the load torque (T _'d) can be ever closer to the rotational speed (N) of the temperature (t) in the.

That is, the rotation speed N when a load is applied can be made constant with respect to temperature rise.

5 is an embodiment of the temperature compensation of the present invention.

This embodiment is an example in which at least one constant voltage element having a temperature coefficient is disposed in at least one of the connection paths of the external circuit element 20. Will mainly be described among properties in the case have installed the junction diode (D ₁₎ for the (E) and a first temperature compensation with a negative temperature coefficient between the terminals of the.

If the forward voltage of the temperature compensation diode (D ₁ ) is V _F , the equation representing the relationship between the load torque (T _d ) and the rotational speed (N) is

N = (Eref + V _F ) (1 + R _b / R _a ) / K ₂ Zø-T _d (R _o -R _t / K) / K ₁ ZøK ₂ Zø (13)

Is displayed.

In this example, when the magnetic flux (ø) decreases due to temperature rise, the forward voltage (V _F ) of the diode (D ₁ ) with negative temperature coefficient also decreases and no load is applied to the load torque. Since the denominator and the numerator of the variable term (Ere + V _F ) (1 + R _b / R _a ) / K ₂ Zø are reduced to the same size, the rotational speed (N) is maintained safely without temperature rise.

If it is set, with reference to Figure 6 are not installing a diode (D ₁₎ having a temperature coefficient portion between the first terminal ① and a connection point (E), the temperature (t), the temperature (t + α) When rising to, the no-load fluctuation term (Eref + V _F ) (1 + R _b / R _a ) / K ₂ Z ø decreases V _F = 0 and ø →→ so that the internal resistance (R _o ) increases with positive temperature. For example, even if the temperature t is increased to the temperature t + α even if the temperature t is set such that R _o -R _t / K ≒ 0, the load becomes R _o -R _t / K ≠ 0 to load The value containing the torque T _d , that is, the value of (R _o -R _t / K) K ₁ Z ø K ₂ Z ø increases.

That is, when the temperature t rises from t to t + α, the relationship between the load torque T _d and the revolving speed N becomes a straight line indicated by a single-dot line from a straight line indicated by a solid line.

In the case of using the DC motor M as the load torque T ' _d , the rotational speed N is the temperature from the rotational speed N _o to the temperature t. It changes from (t + α) to rotation speed N ' _o .

However, when a negative temperature coefficient is applied to the diode D ₁ , the denominator of the no-load rotational speed, that is, the denominator of the first term in the equation (12) is reduced with temperature rise, so the straight line indicated by the dashed-dotted line is immediately before the broken line. It can be moved in parallel until the rotation speed (N ' _o ) can be approached to the rotation speed (N _o ).

That is, in the DC motor M used as the load torque T " _d , the rotation speed can be controlled constantly.

Therefore, the same effect can be obtained even if the diode D ₂ is connected between the resistor R _t and the connection point E and the diode D ₄ is connected between the connection point G and the connection point F. FIG.

Furthermore, diode D ₃ between the connection point E and the connection point G, between the power supply terminal V _cc and the small DC motor M, or between the connection point F and the third terminal ③, respectively. The temperature compensation of the rotation speed can also be performed by connecting, (D ₅ ) (D ₆ ) and so on.

Next, when a positive temperature coefficient is given to the resistor R _{6, as} shown in Equation (12), the second term representing the load characteristic with respect to the temperature rises becomes smaller than the denominator and the numerator. Can be done.

Of course, the resistance R _t is not nourished at no load speed.

7 to 9 show an embodiment relating to the rotational speed adjustment of the present invention, in which at least one variable resistor is installed in the voltage divider circuit to provide a linear relationship between the rotational speed of the small DC motor and the variable resistance ratio. One relationship can be obtained to easily adjust the rotation speed.

That is, if a voltage dividing circuit configured as a fixed resistor (R _a) and the variable resistor (VR _b) (see also Fig. 7) is the expression that shows the relationship between the load torque (T _d) and the rotational speed (N),

Becomes

Here, with respect to the control equation of the rotational speed, the first term of equation (14) The variable resistor VR _b included in and the rotational speed N have a proportional relationship.

Therefore, by changing the resistance value of the variable resistor (VR _b ) it is possible to change the rotational speed (N) proportionally.

In this case, since the variable resistor VR _b and the rotation speed N have a proportional relationship, there is an effect of facilitating adjustment of the rotation speed.

Again fixed resistance (R _a) in place of the variable resistance (VR _a) the first term of the case have installed between the first terminal ① and with the second terminal ② of (see Fig. 8), the formula (12) Since the rotational speed N is inversely proportional to the variable resistor VR _a , it is possible to make a compact operation of the rotational speed.

If the voltage divider circuit is configured as a variable resistor VR _a , a variable resistor VR _b1 , a fixed resistor R _b1 , and a variable resistor VR _b2 (see FIG. 9), the variable resistor ( VR _b1 ) is set to an appropriate value, and the variable resistors VR ₂ and VR _b2 are adjusted to predetermined rotational speeds. For example, after the motor is assembled with a tape recorder, the user selects the variable resistor VR. _It is also possible to set the desired speed speed by adjusting _b1 ).

10 to 13 show an embodiment of the rotational speed conversion of the present invention and by installing a plurality of voltage dividing circuits so that the rotational speed (N) can be converted in stages.

In this case, the control formula of the rotation speed N is

Becomes

Therefore, when resistors with different resistance values are used for the negative voltage resistances (R _a1 ), (R _a2 ), and (R _a3 ), the divided voltage ratios of the voltage divider circuits are different and the rotational speeds (N), (N '), (N Since the value of ") is different from each other, the rotation speed N can be adjusted step by step by switching the switch S ₁ .

Further, in changing the speed of the rotational speed (N) standing by conversion of the switch (S ₁₎ the voltage-dividing resistor _{(R a1), (R a2} ), the voltage-dividing resistor (R _b) and the connection is cut off in the (R _a3) Even though the internal detection of the error detection circuit 10a is high, and the second terminal ② is connected to the voltage dividing resistor R _b , the error detection circuit 2a is connected to the error detection circuit 2a when the contact of the switch S ₁ is shorted. Noise fluctuations can be prevented from occurring.

11 and 12 will change the wiring method of the switch (S ₁ ), the effect of which is substantially the same as the embodiment shown in FIG.

In the case where noise fluctuations generated during the conversion of the switch S ₁ are not taken into consideration, wiring may be performed as shown in FIG.

Thus, according to the present invention, the rotational speed can be adjusted by the partial pressure ratio of the voltage divider circuit, so that even if there is a change in the surrounding temperature, the partial pressure ratio can be kept constant at all times. I can keep it.

Claims (1)

A third reference terminal Eref is provided between a line between the first and second terminals ①② and the two input terminals B and C of the error detection circuit 10a corresponding to each terminal, and the third terminal The driving transistor Q ₂ is connected between the third terminal and the fourth terminal ④ that is grounded, and the classification transistor Q ₁ is provided between the first terminal and the fourth terminal, and the third terminal is provided. The current proportional to the load current flowing in ③ flows to the first terminal ①, and a voltage corresponding to the voltage generated between the first and third terminals ① ③ is applied to the second terminal ②, and the voltage and the reference are applied. The voltage of the DC motor is detected by the error detecting circuit 10a and the output signal of the error detecting circuit 10a is applied to the control input terminal of the sorting and driving transistor Q ₁ (Q ₂ _n). A speed control IC 10 is provided, and a DC motor M is connected between the power supply terminal Vcc and the third terminal ③. Connect a resistor (R _t ) between the power supply terminal (Vcc) and the first terminal (1), and between the first terminal (1) and the third terminal (3), resistors (R _a ) and (R _b ) are A speed control device for a small direct current motor, wherein a voltage divider circuit is connected and a voltage divider point of the voltage divider circuit is connected to a second terminal ②.