JPS6046788A - DC motor speed control device - Google Patents

Abstract

PURPOSE:To obtain a speed controller of a DC motor having less irregular rotation by feeding back a voltage between a DC motor and a resistance element for forming a low resistance side of a bridge circuit to a control transistor. CONSTITUTION:A bridge circuit is composed of a DC motor 1 and resistors 2, 3, 4, a comparator 20 compares a voltage between detecting terminals (a) and (b) with a reference voltage produced by dividing the output voltage of a constant voltage circuit 16 by a voltage divider having resistors 18, 19 are compared by a voltage divider having resistors 18, 19. A transistor 26 is controlled by the output of the comparator 20, thereby controlling a power supply control transistor 7. Further, the base voltage of the transistor 26 is applied to the base of a transistor 29, the voltage between the terminals of the resistor 2 is applied to the emitter of the transistor 29, and the collector of the transistor 29 is connected to the base of the transistor 7, thereby forming a current feedback loop.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speed control device for a DC motor used in audio equipment such as a cassette tape recorder.

Conventional configuration and its problems In recent years, motors used in audio equipment, etc. utilize the fact that the back electromotive force of the motor is proportional to the rotational speed of the motor.
A so-called electronic governor motor is often used.

The electronic governor motor does not require a special speed generator,
The rotation speed can be controlled with an extremely simple configuration, and conventionally, the
A speed control device for bridge detection L1-1 as shown in the figure has been put into practical use.

Hereinafter, a conventional speed control device for a DC motor will be described with reference to the drawings. Fig. 1 is a circuit diagram of a conventional DC motor speed control device.
and resistor 2 constitute the low resistance side of the bridge circuit,
The resistor 3 and the resistor 4 constitute the same high resistance pile.

1. Is the equal-side internal resistance of the DC motor 1 R? Let it be L,
Resistance 2. Resistance 3. The resistance values of resistor 4 are R+ and R2, respectively.
, R3, the equilibrium condition of the bridge circuit R+-R2=R
When 3-Ra is established, the potential difference between the detection terminals a and b of the bridge circuit depends only on the rotational speed and is not related to the load torque, that is, the armature current.

Therefore, the potential difference between the detection terminals a and b is compared with the reference voltage by a comparator, the output of the comparator is amplified by the transistor 5, and the output of the transistor 6 is inserted between the power supply 6 and the Brinnon circuit. Power supply control transistor 7
When the rotational speed of the DC motor 1 increases, the current I supplied to the bridge circuit is reduced, and conversely,
By increasing the current when the rotational speed decreases, the rotational speed of the DC motor 1 can be kept constant. By the way, the diode 8 is connected to the power supply 6.
The forward voltage of the diode 8 is divided by a voltage dividing circuit consisting of a resistor 10 and a resistor 11, and the voltage dividing point C is connected to one input terminal of the comparator. That is, it is connected to the base of transistor 12.

Here, the reference voltage is given as the voltage across the resistor 11.

There is still a connection point between resistor 3 and resistor 4.

The detection terminal of the circuit is connected to the other input terminal of the comparator, that is, to the base of the transistor 13. self i
A current is supplied to the J comparator from the power source 6 through the resistor 14. Note that the capacitor 15 is an oscillation prevention capacitor.

By the way, normally, the armature current of the DC motor 1 is a current (with no current ripples caused by winding irregularities in papier-mâché windings, etc.). i 1li 1.: The potential of the terminal also includes ripples.One input terminal of the terminal 19, that is, the base of the transistor 120, point C, is connected to the potential of the reference voltage 11 at the point a.
(Zunawa 0 ↓ 1 (Since the potential is the superposition of the voltage across resistor 11 (this is a DC' voltage -), that potential mist includes lilinople. However -) hand,
A voltage including a ripple is input to one input terminal C of the ratio axis converter, and the output of the comparator (+'i is connected to the transistor 5 and the power supply control transistor terminal, 1
: Since the current l is amplified, the current l has a large current ripple.

Unfortunately, the DC motor 1 is driven with a large current ripple, and lacks stability in rotational speed, which causes uneven rotation.

OBJECTS OF THE INVENTION The object of the present invention has been made in view of the above-mentioned problems in conventional speed control devices for DC motors. An object of the present invention is to provide an excellent speed control device for a DC motor.

Structure of the Invention In the speed control device for a DC motor of the present invention, a series circuit of a wave-controlled DC motor and a first resistance element constitutes a low paper feed, and a series circuit of a second resistance element and a third resistance element constitutes a low paper feed. a bridge circuit configuring a high/low voltage; a comparator that compares a potential difference between detection terminals of the bridge circuit with a reference voltage; a first transistor that amplifies the output of the comparator; a second transistor to which a base voltage is applied and a voltage responsive to the terminal voltage of the first resistance element is fed back to the emitter; and a combination of the first and second transistors inserted between the power supply and the bridge circuit. It is equipped with a power supply control transistor that controls the amount of power supplied based on the output, thereby driving the limb control DC motor with a current with small ripple.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows the speed 1 of a DC motor in an embodiment of the present invention.
It is a circuit connection diagram of the dust '1till all device. Second
In the figure, the components similar to those shown in the circuit wiring diagram of the conventional DC motor speed control device shown in Fig. 1 are 1.
It is expressed with a circular diagram.

- In Fig. 2, the split m DC motor 1 and the first resistor 4i'
+: Element 2 constitutes the low paper input of the bridge circuit, and the second resistance element 3 and the third resistance element 4 constitute the same height 1.
1 (Payment is configured.

One terminal of the constant 71L voltage circuit 16 is connected to the detection terminal a of the low paper supply (11!L) of the above-mentioned IJ and J circuits, and the other terminal is connected to the positive side of the power supply 6 via the constant current circuit 17. The output voltage of the constant voltage circuit 16 is divided by a voltage dividing circuit consisting of a resistor 18 and a resistor 19, and the voltage across the resistor 19 is applied to obtain the base voltage. The connection point C between the resistor 1 and the resistor 19 is connected to one input terminal of the comparator 20, that is, the base of the transistor 210, and the detection terminal of the high/low input 1111 of the bridge circuit is the other input of the comparator 20. The terminal A is connected to the base of the transistor 22.
1.22, the emitters are coplanarly connected, and their common connection point is connected to the positive terminal of the power source 6 via the constant current circuit 23.

Further, the collectors of the transistors 21 and 22 are respectively connected to the collectors of transistors 24 and 25 constituting an active load, and the base of the transistor top block 24 is connected to the collector as well as to the base of the transistor 25. 24.26
The emitter of is connected to the negative terminal of the power source 6. Furthermore, the base of the first transistor 26 is connected to the collector of the transistor 22, and the emitter of the first transistor 26 is connected to the negative terminal of the power supply 6 via a resistor 27, and the collector is connected to the base of the power supply transistor 22. It is connected. A second transistor 29i1 whose base is connected to the base of the first transistor 28 via a resistor 2B, and whose emitter is connected to the detection terminal B on the low resistance side of the bridge circuit via a resistor 30. is connected to the base of the feeding transistor, where:, 31
(d constitutes a feedback circuit that feeds back a voltage responsive to the voltage across the terminals of the first resistive element 2 to the emitter of the second transistor 29. The positive side end A is connected to one power supply terminal of the glitch circuit of the same collector It;I: nil.It should be noted that the first transistor 2
A +r'' oscillation prevention capacitor 32 is connected between the base of the power source 6 and the negative terminal of the power source 6.

The operation of the DC motor speed control device according to an embodiment of the present invention constructed as described above will be described below.

1. As in the conventional DC motor speed control device shown in FIG.
The potential difference between b depends only on the rotational speed and has no relation to the load l or the armature current.

Therefore, the comparator 20 compares the potential difference between the detection terminals &b and the reference voltage obtained by dividing the output voltage of the constant voltage circuit 16 by the resistor 18 and the resistor 19 and using the voltage between the terminals of the resistor 19. , the output of the comparator 20 is amplified by the first transistor 26, and
- The power supply control transistor 7 is controlled by the output of the Ransisk 26, so that the rotational speed of the DC motor 1 increases (if this occurs, the current I supplied to the bridge circuit is reduced, and the rotational speed gradually decreases/ In this case, by increasing the current I, the rotational speed of the DC motor 1 can be kept constant.

This is the operation of the speed control loop that controls the DC motor 1 at a constant speed jl+l+, but in the DC motor speed control device of the present invention, the first transistor 2
60 base voltage is applied to the base of the second transistor 29, the armature current of the DC motor is detected as the voltage between the terminals of the first resistive element 2 connected in series with the DC motor 1, and the detected voltage is A current feedback loop is configured by applying a current to the emitter of the second transistor 29 through a resistor 30 and connecting it to the base of the power supply transistor 7. There is.

The power supply to the power supply transistor 7, Qj, is controlled by the combined output of the speed control loop and the current feedback loop.

Mekoda 1-1 If the action of the current feedback loop slips too much, the necessary torque will no longer be produced, so the speed/lf
It is preferable that sufficient control be applied to the +I predetermined 1j roof so that the current feedback loop acts auxiliary.

The feedback of the precurrent feedback loop can be adjusted (by the resistor 30).

Here, the operation of the feedback circuit 31 constituting the rj'J N12 current feedback loop will be further explained.

Now, due to some factor, the DC motor
Assuming that the armature current of the transistor 1 increases, the voltage between the terminals of the first resistive element 2 also instantaneously increases, and as a result, the base-emitter voltage of the second transistor 29 instantaneously decreases. Therefore, the collector current becomes smaller. Therefore, the base current of the power supply transistor γ decreases by that amount, and the current 1 supplied to the bridge circuit momentarily decreases. On the other hand, when the armature current momentarily decreases, the current I momentarily increases due to the exact opposite circuit operation.

Therefore, even if there is winding unevenness in the armature winding, the ripple of the current I supplied to the bridge circuit is suppressed, and the DC motor 1 is driven by the armature current with small ripples, so the rotation speed is reduced. The stability is extremely good, and the rotation is controlled with little unevenness.

1. To detect the armature current flowing through the DC motor 1, instead of adding a special resistance element or circuit for detection, we use a bridge circuit for detecting the back electromotive force required for speed control. Since the 10th resistance element 2 on one side is also used as a node and the voltage between its terminals is utilized, it can be constructed in two years at a very low cost.

Theory 1 of “Effects of Invention” 2! J] However, as is clear, the present invention
ljIJ1i111 ilfMe ``'::-ri is included on one side, /this bridge circuit and 'IJiJ +f
J bridge circuit detection IJ” terminal 1? A comparator that makes the ratio of the potential difference of j] and the reference voltage by 1, and the blade of the comparator on page 79
The base voltage of the 281 transistor is applied to the base of the first transistor having a width of
jl: a second transistor whose speed is measured by the weight S in response to the voltage across the terminals of the first resistive element;・Since it is equipped with a power supply control transistor that controls the power supply 1j4 based on the combined output of the Lancisors, ntJ
Description 11jlJ It is possible to drive a ffQI direct 6fn motor with a current with small ripples, and it is possible to realize a direct current motor device with extremely good rotational speed stability and little rotational unevenness. This method uses the current feedback loop's long signal and the voltage between the terminals of the first resistive element, which is one side of the bridge circuit, and does not require any special elements or circuits for current detection. Another great advantage is that it can be constructed easily and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram of a conventional DC motor speed fl control device, and FIG. 2 is a circuit connection diagram of a DC motor speed allocation 11 device according to an embodiment of the present invention. 1... Wave control DC motor, 2... First resistor element r
-13...-Second resistance element, 4...Third resistance element r-16-...Electro-hydraulic; 1.7...Power supply control transistor, 16...- Constant voltage circuit , 20... Comparator, 26... First transistor, 29. Second transistor, 30... IJ (anti.

Claims (1)

[Claims] a bridge circuit in which a series circuit of a controlled DC motor and a first resistance element constitutes a low resistance side, and a series circuit of a second resistance element and a third resistance element constitutes a high and low pile; a comparator that compares a potential difference between detection terminals with a reference voltage; a first transistor that amplifies the output of the comparator; a base voltage of the first transistor is applied to the base; and a first resistor that has an emitter. a second transistor to which a voltage responsive to the voltage between the terminals of the element is fed back; and a power supply control reserve inserted between the power supply and the Zorinoji circuit to control the power supply source based on the combined output of the first and second transistors. 11. A speed control device for a DC motor characterized by comprising a transistor.