JPS6011550B2 - DC motor speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control device for a DC motor that can increase torque during rotational speed control (hereinafter referred to as maximum control torque) and starting torque, and is suitable for semiconductor integrated circuit implementation. .

A small DC motor speed control device called an electronic governor compares the back electromotive force generated in the drive coil in proportion to the rotational speed of the DC motor with a reference voltage, and executes control operations based on the difference in voltage between the two. However, the voltage generated between the terminals of the motor is usually not the back electromotive force itself, but includes a voltage drop due to internal resistance such as winding resistance.

Therefore, in order to extract only the back electromotive force between the terminals of the motor and perform accurate speed control operations, it has been common to configure the speed control device with a resistance bridge configuration. In a speed control device having a resistance bridge configuration, it is extremely important to correctly select the value of the resistance, which is the main component of the bridge, to a predetermined value. By the way, in recent years, various circuit devices are being implemented as semiconductor integrated circuits, and the speed control device for the above-mentioned DC motor is also being implemented as semiconductor integrated circuits.
When attempting to integrate a speed control device with a resistance bridge configuration into a semiconductor integrated circuit, in which it is important to select the resistance value to a predetermined value, it is difficult to form the resistance for the bridge configuration with a diffused resistor with large variations. , the resistor for this bridge configuration is externally attached.

For this reason, the inconvenience of an increase in the number of lines led out to the outside of the semiconductor integrated circuit has been unavoidable. As a configuration of a speed control device that can eliminate such inconveniences, a configuration in which the resistance bridge shown in FIG. 1 is modified may be considered.

In FIG. 1, the circuit parts within the dotted line frame are the parts to be integrated into a semiconductor circuit, including the control circuit section 1, reference voltage generation circuit section 2, current limiting circuit section 3, constant current circuit section 4, and current distribution circuit section. The circuit section 5 will be built into a single semiconductor substrate.

Three terminals, the power supply voltage application terminal 6, the output terminal 7, and the adjustment resistance connection terminal 8, are used as external terminals. Further, a DC motor 9 is connected to the output terminal 7, and an adjustment resistor 10 is connected between the terminal 8 and the ground point. In the speed control device having the above configuration, a reference voltage Vrer proportional to the back electromotive force a of the DC motor is generated between the output terminal 7 and the adjustment resistor connection terminal 8, and this voltage is equal to the back electromotive force Ea. A circuit operation is performed to change the voltage drop across the adjustment resistor 10 so that the voltage drop in the adjustment resistor 10 is changed. For example, when the voltage drop due to the internal resistance Ra of the DC motor 9 fluctuates due to a disturbance, the current flowing into the adjustment resistor 101 is changed by the current distribution circuit 4 to change the voltage drop due to the adjustment resistor 10, thereby changing the reference voltage Vref and the back electromotive voltage. An operation is performed to keep the values of a and a equal to each other, and fluctuations in the rotational speed of the DC motor are suppressed.
However, when controlling the speed of a DC motor using this speed control device, it is difficult to obtain a large starting torque and it takes a considerable amount of time for the motor rotation speed to reach a predetermined value, and the maximum control torque is small. The problem arises. The present invention has been made in view of the inconveniences in the conventional DC motor control devices described above, and has a configuration suitable for semiconductor integrated circuits, and is capable of producing a large starting torque and a large maximum control torque. A speed control device for a DC motor is provided.

The present invention will be described in detail below with reference to FIG. 2, which shows an example of the configuration of the speed control device of the present invention.

In the illustrated speed control device of the present invention, NPN transistors 1 1, 12, 13 and 14 for driving a DC motor have the same characteristics, and emitter resistors 15, 16, 17 and 18 of these transistors also have the same characteristics. These circuit elements 11 to 18 constitute a current mirror of the motor current la flowing through the DC motor 9. Further, the collector of the transistor 11 is connected to a diode 2 to which a constant current is supplied by a constant current source 19.
The forward voltage drop in the series connection of 0 and 21 is applied to the base and the emitter of the transistor 25 which is Darlington connected to the transistor 24 whose collector is connected to the terminal 23 via the resistor 22, and the remaining transistor 12. The collectors of 1 to 14 are connected in common to a terminal 26, and the DC motor 9 is connected between this terminal 26 and a power supply terminal 27. Note that the terminal 23 is connected to a voltage dividing point of voltage dividing means consisting of a resistor 28 and a variable resistor 29 connected between the terminal 26 and the power supply terminal 27. In such a circuit component, the transistor 2
The base potential V8 of terminal 26 is 2 higher than the potential V26 of terminal 26.
The forward voltage drop of the diodes 20, 21 is higher by 2Vo, while the collector voltage of the transistor 11 is Vc, . is lower than V824 by the sum of the base-emitter voltages VB824 and VBE25 of transistors 24 and 25. By the way, the values of Vo, VBE, and VBE25 are approximately equal, so that "Vc, which is lower than VB24 by 2 Vo, is approximately equal to the potential V26 of the terminal 26.
That is, the collector voltage of transistor 11 is maintained at approximately the same voltage as the collector voltages of transistors 12 to 14. Transistors 30 and 31 are transistors forming a differential amplifier, and the base of transistor 30 is connected to terminal 26, while the base of transistor 31 is connected to the negative terminal of reference voltage source 32. The collectors of transistors 33 and 34 connected in a calendar mirror are connected to the collectors of transistors 30' and 31'.

Further, a constant current source 35 is connected to the common emitter connection point of the transistors 30 and 31. The collector of the transistor 31 is connected to the base of a PNP transistor 38 whose emitter is connected to the power supply terminal 27 via a constant current source 36 and whose collector is connected to the ground terminal 37.
Further, the collector of the emitter of the transistor 38 is connected to the power supply terminal 27, and the emitter is connected to the ground point via the resistor 39, and the base of the transistor 40, which is also connected to the bases of the transistors 11 to 14, is connected. Note that 41 is a constant current source. According to the speed control device of the present invention having the above configuration, when a fluctuation occurs in the rotational speed of the DC motor, the following circuit operation is executed. This fluctuation is suppressed.

For example, if the rotational speed of the DC motor 9 changes in the direction of increasing, the back electromotive voltage Ea of the DC motor 9 increases, and therefore the voltage at the terminal 26 decreases.

As the voltage V26 at the terminal 26 decreases, the base bias of the transistor 30 forming the differential amplifier becomes deeper, its collector current increases, and the collector current of the transistor 34 forming the current mirror also increases. by the way,
As the collector current of transistor 34 increases, the current drawn into the collector, that is, the base current of PNP transistor 38 increases, and its emitter current also increases. Therefore, the base current of the transistor 40 whose base is connected to the emitter of the PNP transistor 38 decreases, and the base current and collector current of the transistors 11 to 14 whose bases are connected to the emitter of the transistor 40 also decrease. As a result, the DC motor 9
Speed control is performed in such a direction that the motor current la decreases and the rotational speed of the motor decreases. Further, when the rotational speed of the DC motor 9 changes in the direction of decreasing, an operation opposite to the above-described circuit operation is performed to perform speed control in the direction of increasing the rotational speed. By the way, the control maximum torque and starting torque of the DC motor whose speed is controlled by the speed control device of the present invention are extremely large values.

This value becomes maximum when the voltage at terminal 26 is minimum, and if transistors 12 to 14 are saturated, the maximum control torque becomes large. In the speed control device of the present invention, the outside of the collector of the transistor 40 that supplies the base current of the transistors 11 to 14 is connected to the power supply terminal 27. Therefore, the transistor 40 has a base current that can saturate the transistors 12 to 14. It is possible to supply.

The maximum control torque when this base current is supplied is m
The town is expressed by the following formula. . m rudder Kt・VCC-Ea
. -VC8"[11Ra+RE. Here, Kt is the torque constant of the DC motor, Vcc is the power supply voltage applied to the terminal 27, and Ba.

is the back electromotive force at the rated rotational speed, Vc8 is the collector-emitter saturation voltage of transistors 12 to 14, Ra is the internal resistance of the DC motor, and R8o is the emitter resistance 16
The combined resistance value is ~18. In the speed control device of the present invention shown in FIG. 2, as described above, the transistor 40 supplies enough base current to the transistors 12 to 14 to saturate them, so the value of the Vc ear is 0. .5V
The following is true. Therefore, in the speed control device shown in FIG. 2, for example, Kt is 96 T/A and Vcc is 4.5.
V, Ea. is 2.45V, Ra is 6.30, R8a is I
Assuming that Q and VcE are 0.5V, the maximum control torque Omax is calculated by substituting these values into the first equation, ◇mpine=96×4.5-2.45-0-56.3+1 It can be found as ni20,4 (Taga).

That is, under the above circuit constants, the maximum control torque Cm
An extremely large value of 20.4 ta arc is obtained for ax. By the way, in the speed control device of the present invention shown in FIG.
The collector voltages Vc, . It is important to keep the collector voltages of transistors 12 to 14 at the same value.

That is, if, for example, the collector of transistor 1 is directly connected to terminal 23 instead of the circuit configuration shown in the figure, the collector voltage of transistor 11 will be lower than that of transistor 1.
The voltage V of the reference voltage source 32 is higher than the collector voltages of 2 to 14.
The price will be higher by ref. Therefore, even if transistors 2 to 14 are saturated at the maximum control torque, transistor 1
1 is not saturated, transistor 11 and transistor 12~
The collector current characteristics of transistor 14 become different, and the current ratio between transistor 11 and transistors 2 to 14 changes. Therefore, there is a problem that the motor rotation speed is not kept constant and becomes unstable. In the speed control device of the present invention, as already explained, the transistor 11 and the transistor 1
The collector voltages of Tortoises 2 to 4 are equal, so the above-mentioned problems do not occur, and the motor rotational speed is kept stable even at the maximum control torque.

Further, according to the speed control device of the present invention, the starting torque is also increased.

That is, when the DC motor 9 is locked, the back electromotive force Ea. becomes zero, so the voltage at terminal 26 increases. Due to this voltage increase, the transistor 3 forming a differential amplifier
The base bias of transistor 30 becomes shallower, which causes a decrease in the collector current of transistor 30,
Based on the decrease in the collector current of transistor 4 and the decrease in the collector current of transistor 34, the base current of transistor 38 decreases, and the base current of transistor 40 connected to the emitter base of transistor 38 increases; A circuit operation is performed that results in an increase in the base current of , and the collector currents of transistors 11-14 increase. Therefore, a large motor current flows through the DC motor 9. By the way, if a large motor current flows as described above when the DC motor 9 is locked, and the base voltage of the transistor 31 forming the differential amplifier drops too much,
The collector-base junction of transistor 31 is biased in the forward direction, and base current flows through PNP transistor 38, making PNP transistor 38 conductive, decreasing the base current of transistor 40, and reducing transistors 11 to 11.
14 base current reduction and transistors 11-1
4, resulting in a circuit condition that causes a decrease in the collector current of DC motor 3, resulting in a disadvantage that the torque of DC motor 3 decreases.

For example, the base-emitter voltage of transistor 40 is VBE, the base-emitter voltage of transistors 11 to 14 is VB8, and the voltage drop due to resistors 15 to 18 is VR.
Then, the base voltage VB4o of the transistor 40 in the above circuit state is tVR+VBE+VB8
4.

It is. Therefore, in order to keep the PNP transistor 38 in a damped state, the base voltage VB38 of the PNP transistor 38 when the motor is locked is set to VB4. It is necessary to maintain the voltage at a value equal to or higher than the value obtained by subtracting the base emitter voltage VB838 of the transistor 38 from the voltage (V side - VBE38). Similarly, in order to prevent the collector-base junction of the transistor 31 from being forward biased, the base voltage VB3 of the transistor 31 should be changed to the base-emitter voltage VB3.
Value obtained by subtracting E milk from VB38 (VB spot - VBE$)
It is necessary to maintain it above. In the speed control device shown in FIG. 2, if the ratio of the emitter area of transistor 11 to the sum of the emitter areas of transistors 12 to 14 is 1:K (integer), then 1'K of motor current la is connected to terminal 23. Current flows.

Therefore, the value of the resistor 28 is determined by the internal resistance R of the DC motor 9.
If K times a is selected, the voltage drops due to the resistor 28 and the internal resistor Ra will be equal, and the voltages at the terminals 23 and 26 will be equal. Therefore, when the motor is locked, transistor 1
2 to 14 are saturated and the voltage at the terminal 26 drops to a predetermined value, the voltage at the terminal 23 also drops to a value equal to this voltage, and the base voltage VB of the transistor 31
3 is a voltage lower than the voltage at the terminal 23 by the reference voltage Vrd. At this time, if the reference voltage Vref is approximately equal to the voltage at the terminal 26, the base voltage VB of the transistor 31 becomes approximately OV, causing the above-mentioned problem.
In order to eliminate this inconvenience, it is necessary to keep the voltage at terminal 23 higher than the voltage at terminal 26 by limiting the current flowing to the collector of transistor 11 when the motor is locked. This objective is achieved. That is, when a large collector current flows through the collector of the transistor 11, the base current of the transistor 25 increases, the voltage drop across the resistor 22 increases, the transistor 24 becomes saturated, and the base current and emitter current of the transistor 25 are limited.

It goes without saying that the value of the resistor 22 is selected so that the transistor 24 will not become saturated under normal operating conditions other than when the motor is locked. By the way, the voltage y at the terminal 23 is the collector voltage of the transistor 1, which is Vc, . , the base-emitter voltage of the transistor 25 is VBE25, and the saturation voltage of the transistor 24 is Vc824.
, the collector current of transistor 11 is lc, . , the current amplification factor of the transistor 25 is hFE25, and the resistor 22 is
If the value of is R22, then V23=Vc, . 10V8825
10 Vc824 10 pieces/R22. ．．・．． ．．・It is expressed as '2).

For example, in the speed control device shown in FIG. 2, VCII 20.6V, VB825 20. 7V, VCE Shigeru 〇. IV
, ICII=1 Duke, hFE25=100, and R2
Assuming that 2 is the mother KQ, V23 can be found to be 2.0V by substituting these values into Equation 21.

At this time, the base voltage VB31 of the transistor 31 is V
8 Breasts 2 V23-Vref ……[
31, and if Vref is set to 1.2V, for example, VB3, becomes 0.8V.

That is, if the value of VB3, is maintained above the base-emitter voltage VB83, (approximately 0.6V) of the transistor 31, the PNP transistor 38 will not conduct, and the current of the constant current source 36 will all be the base current of the transistor 40. Therefore, the collector current becomes a very large value. As a result, a large collector current flows also in the transistors 12 to 14, and a large starting torque is obtained. By the way, the starting torque of the DC motor 9 is expressed as S = Kt:V Atsushi Ichigo...'31.

Therefore, if the circuit constant is the constant exemplified for the limit maximum torque Omax, the starting torque ◇s is oS
: 96 x basket stagnation = 526 (Tahada).

Note that if the resistor 22 is not provided, the voltages at the terminals 23 and 26 will be equal when the motor is locked.

Furthermore, the base voltage VB3 of the transistor 31 does not exceed its base-emitter voltage VBE3 (approximately 0.6V). Therefore, if the reference voltage Vref is 1.2V, the voltage V23 at the terminal 23 is V23=VB3, +Vr
ef=0.6V+1.2V=1.8V.

The voltage V26 at terminal 26 is equal to the voltage V23 above, so the VcB of transistors 12-14 is 1.8V.
Then, by substituting this value into the first conditioning equation, the starting torque of 0s is found.

S = 96 x Atsushiki = 355 (Taga).

In this way, depending on the presence or absence of the resistor 22, the starting torque mass
There is a noticeable difference in the size of the chopsticks.

FIG. 3 is a diagram showing changes in torque with respect to changes in motor rotation speed when speed control is performed by a conventional speed control device and a speed control device of the present invention, and A is a diagram showing changes in torque with respect to changes in motor rotation speed when speed control is performed by a conventional speed control device and a speed control device of the present invention. B shows the change caused by the speed control device of the present invention. As is clear from the diagram, according to the speed control device of the present invention, the load torque that deviates from the rated rotational speed Rr, that is, the maximum control torque, is much larger than in the case of the subordinate speed control device. - The torque when the motor speed reaches zero, that is, the starting torque, is also much greater than with conventional speed control devices. As is clear from the above description, when the DC motor speed control device of the present invention is fabricated into a semiconductor integrated circuit, the circuit portion surrounded by the dotted line is built into a single semiconductor substrate.

At this time, the number of terminals that need to be led out to the outside is only four, which is suitable for semiconductor integrated circuits. Furthermore, the maximum control torque and starting torque can be increased, and therefore the motor rotation speed can be maintained at a constant rotation speed even when a load heavier than that of the subordinate speed control device is applied.
A high-performance DC motor with a long rise in rotational speed can be realized, and effects such as scales can be achieved. Incidentally, if a DC motor whose speed is controlled by the speed control device of the present invention is used to drive the turntable of a record player, it will be possible to drive a high-performance record player with a short rise time until the rated rotational speed is reached.
Doprayer is realized.

Furthermore, if used as a tape drive for a tape recorder, even if the friction of the tape increases and the load on the DC motor increases, this will prevent the DC motor from locking up. You can also do that.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a secondary DC motor speed control device, FIG. 2 is a circuit diagram showing a specific circuit configuration of the DC motor speed control device of the present invention, and FIG. FIG. 2 is a diagram showing the relationship between the rotational speed and torque of a DC motor whose speed is controlled by a conventional speed control device and a speed control device of the present invention. 9...DC motor, 11-14...NPN transistor, 15-18, 39...Emitter resistor, 19
, 35, 36, 41... Constant current source, 20, 21... Diode, 22... Collector resistor, 23, 26, 27, 3
7... External lead-out terminal, 24, 25...
Darlington connection transistor, 28... Fixed resistance, 29... Variable resistor, 30, 31...
...Transistor for forming differential amplifier, 32...
Reference voltage source, 33, 34...current mirror connected transistors, 38...PNP transistor, 40...NPN transistor for base current supply. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A Darlington-connected transistor including a resistor in the collector circuit of the front-stage transistor, to which the forward voltage drop of the diode is supplied as a base bias voltage, and a collector connected to the power supply terminal via the first resistor, Emitsuta is the second
a first transistor grounded through a resistor, the base of which is commonly connected to the base of the first transistor;
The collector is connected to the power supply terminal via a DC motor, and the emitter is grounded via a third resistor, and the emitter area is selected to be an integral multiple of the emitter area of the first transistor. A second transistor having the same polarity as the transistor has its emitter connected in common and is connected to a constant current source, one base is connected to the collector of the second transistor, and the other base is connected to the Darlington connected transistor and the first transistor. a differential amplifier consisting of two transistors connected to the other terminal of a reference voltage source, one terminal of which is connected to the connection point with the resistor;
A third transistor whose base current changes according to the current flowing through the collector of one of the transistors of the differential amplifier to control current supply to the bases of the first and second transistors.
and a variable resistor for speed adjustment connected between the connection point between the Darlington connected transistor and the first resistor and the collector of the second transistor. Motor speed control device. 2. The second transistor is characterized in that it is constituted by a parallel connection of transistors whose collectors are connected in common, resistors of equal value are connected to their emitters, and the other ends of the resistors are connected in common. A speed control device for a DC motor according to claim 1. 3. The speed control device for a DC motor according to claim 1, wherein the base bias supply diode is a series connection of the same number of diodes as the number of transistors constituting the Darlington connection transistor. 4. The DC motor speed control device according to claim 1, wherein the base bias supply diode is connected between the base of the Darlington connected transistor and the collector of the second transistor. . 5
2. The speed control device for a DC motor according to claim 1, wherein collector circuits of two transistors constituting the differential amplifier are connected to collectors of transistors connected in a current mirror manner. 6. A patent claim characterized in that a PNP transistor is arranged between the collector of the differential amplifier forming transistor on the side whose base is connected to the other end of the reference voltage source and the base of the third transistor. A speed control device for a DC motor according to item 1. 7. Circuit elements other than the first resistor and the speed adjustment resistor are integrated into semiconductors, and the first resistor is integrated into the semiconductor integrated circuit.
2. The speed control device for a DC motor according to claim 1, wherein the resistor and the speed adjusting variable resistor are externally connected.