JPS602877B2 - Small DC motor speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a bridge detection type DC motor speed control device that facilitates the starting of a DC motor with fewer components and provides a starting device with no current loss. be.

Conventionally, this type of device has been used as shown in Figure 1.
It has been proposed to provide a reference potential point between the power supply lines by connecting a resistor and a diode in series, detect the motor voltage using a switching transistor for starting, and then flow a base current for starting outside the power supply control transistor. 0 Here, to explain the outline of the operation with reference to Fig. 1, the rotor of the DC motor whose speed is to be controlled at 1G, 2 and 2' are its brushes, 3 and 3' are stator magnets, and this DC motor Rotor 1 including motor brushes 2 and 2' and resistor 4
, 5, and 6 constitute a bridge circuit with each side as each side.

Now, let Ra be the equivalent internal resistance of this DC motor, and let the resistance values of resistors 4, 5, and 6 be R4, R5, and R6, respectively. When the bridge equilibrium condition Ra, R5=R4・R6 is satisfied, then Bridge detection terminals a-b in the diagram
The voltage between depends only on the rotation speed.

Therefore, the detection transistor 7 detects the voltage difference between the voltage between a and b and the voltage value Es of the reference voltage diodes 8 and 9, and when the rotational speed of the DC motor increases, the bridge circuit and the DC If the internal resistance of the power supply control transistor 10 inserted between the power source 14 increases, and the internal resistance decreases when the rotational speed decreases, the rotational speed of the DC motor can be kept constant by controlling its base current. It will be preserved. In this circuit, when the rotational speed of the DC motor decreases, the potential at point a decreases, so the base current of transistor 7 increases, which also increases the collector current, so the internal resistance of transistor 0 decreases, and the rotation of the DC motor decreases. Works to increase speed.

On the other hand, when the rotational speed of the DC motor increases, the potential at point a increases, so the base current of transistor 7 decreases, and the collector current also decreases, so the internal resistance of transistor 10 increases, and the DC motor Acts in the direction of lowering the rotation speed of.

Now, in the figure, a resistor 11 and diodes 12 and 13 are connected in series between the positive side feed line and the negative side feed line, and the connection between the resistor and the diode is the resistor 1.
The base of the starting transistor 15 is connected via 4.

Further, the emitter of the starting transistor 15 is connected to the emitter of the detection transistor 7, and the collector is connected to the power supply control transistor 3.
They are connected to the bases of the transistors 10, respectively. Next, in order to explain the effects of these elements, consider the case where the power switch 16 is turned on and the voltage value of the DC current 17 is gradually increased from zero.

However, it is assumed that the diodes 2 and 13 and the base G emitters of the transistor 5 all have perfect polygonal characteristics, and current only flows when their respective forward voltages reach VF and VB. 4
Now, the power supply voltage E. is E. When VB is low, the diode is
All transistors are off, and no current flows through the control circuit. Therefore, the voltage across the resistance 3 is also zero. E
When oZVB occurs, a forward current, that is, a base current flows between the base and emitter of the transistor 15, so a collector current also flows, and this becomes the base power supply of the power supply control transistor 0, so a voltage appears at both ends of the DC motor.

In the range of 2VF>EoZV8, diodes 12 and 13 remain off, but when Eo≧WF, diode 1
2 and No. 3 are turned off, and thereafter the potential at point c is maintained at 2VF.

Furthermore, as Eo increases, the voltage across the DC motor increases, and forward current also flows through the diodes 8 and 9, but the voltage across the DC motor increases (4VFm
VB), the base current of transistor 5 stops flowing, and when the voltage across the DC motor becomes even larger, the base and emitter of transistor 15 are reverse biased, and at this point the starting circuit is complete. is disconnected from the control circuit.

However, at this time, only one transistor is in a conductive state, so a current flows in all directions between the base and emitter of the detection transistor T, and the power supply voltage E. Is it possible to use a transistor to control the rotational speed of the DC motor at a constant level when the value exceeds the starting value? And one river works. The resistor 14 inserted into the base side of the transistor 5 is to prevent the junction from being destroyed by avalanche when the reverse bias between the base and emitter of the transistor 5 becomes too deep. The resistor 8 inserted between the side power supply line and the DC motor's brass side power supply terminal is a resistor for correcting voltage characteristics, and the resistor 9 inserted between the emitters is the base of the transistor 10. It is a resistor for current compensation.In the circuit shown in Figure 1, transistor I, resistor I, 14, diode 12, and blade 3 are starting elements. Although it is a completely unnecessary part, it accounts for more than a quarter of the total cost of circuit parts, and the total number of parts (excluding motors, switches, and power supplies).

), accounting for one-third of the total. Also, even after the DC motor starts, the diode 12,? 3, a forward current flows between the emitter and the base of the transistor 15 as a loss current.Furthermore, in order to reduce this reverse current, increasing the value of the resistor 14 increases the amount of power required by the motor. Even if a starting current no longer flows or the value of the resistor 14 is zero, the current flowing to the base of the transistor 10 by the transistor 15 at startup is approximately equal to the voltage across the diode 12 or 13 by the resistance value of the resistor 20. Since the DC motor has a low internal resistance, there are problems such as insufficient starting current flowing.

The speed control device for a small DC motor of the present invention solves the above problems.

FIG. 2 shows a circuit connection diagram in one embodiment of the present invention.

In FIG. 2, components having the same configuration and function as those in FIG. 1 are designated by the same reference numbers, and their explanations will be omitted.
In FIG. 2, instead of the basic voltage diode 9, the base-emitter junction of the starting switching transistor 21 is connected in series with the diode 8, and the transistor 2
1 has a second switching transistor 22 at its collector.
The base of the transistor 22 is connected to the base of the transistor 22, and the emitter of the transistor 22 is connected to the emitter of the transistor 22 via a resistor 23. Further, the collector of the transistor 22 is connected to the base of the power supply control transistor 10 together with the collector of the detection transistor 7 .

Further, a voltage characteristic compensation resistor 18 is connected between the collector of the transistor 21 and the positive power supply line.

Now, to explain the outline of the operation, when the switch 16 is closed and the voltage Eo of the DC power supply 17 is gradually increased, since no voltage appears at both ends of the DC motor at first, the transistor 21 is in the off state. A base current flows through the transistor 22 through the resistor 18 .

Since the collector current of the transistor 22 flows through the base of the power supply control transistor 10, the detection transistor 7 also becomes conductive, and a voltage is applied across the DC motor to start the DC motor.

On the other hand, when a voltage is applied to both ends of the DC motor and the DC motor starts, a forward current flows between the diode 8 and the base and emitter of the transistor 21, so the transistor 21' is turned off and the transistor 22 is turned off. Base current no longer flows through.

The operation of the starting circuit is now complete, and from now on the DC motor is constantly controlled by the detection transistor 7 and the power supply control transistor 10.

In Fig. 2, the resistor 18 is a starting resistor for flowing base current to the switching transistor 22 in order to start the DC motor. Similarly, it can be used as a resistor for compensating voltage characteristics.

Therefore, in the device shown in FIG. 2, after the DC motor is started, the only elements that do not contribute to the operation of the control circuit are the transistor 22 and the resistor 23, and there is no current loss in the starting circuit.

In addition, in FIG. 2, the second switching transistor 2
The resistor 23 connected to the emitter 2 is a resistor to ensure that the DC motor shifts to the constant speed control state.If the resistance value of the resistor 23 is too low, the DC motor Even after starting, the potential at point b does not become lower than the potential at point a, and the transistor 22 remains on, making it impossible to perform constant speed control. next,
Figure 3 not only eliminates current loss in the starting circuit, but also
This is an embodiment of the present invention configured to reduce current loss in the control circuit by adding a starting circuit, and the potential between the emitter of the detection transistor 7 and the negative feed line is divided by a resistor 20a and a resistor 20b. The emitter of the second switching transistor 22 is connected to this dividing point via a constant voltage diode 24.

The operation until the DC motor is started is exactly the same as that shown in FIG. 2, but in this circuit, the resistance value of the resistor 20a can be made considerably large, so that the circuit loss current during constant speed control becomes very small.

To explain this in more detail, FIG. 4 shows the torque characteristics of a typical DC motor during constant speed control.

In Figure 4, when the power supply voltage is low, the maximum torque during constant speed control of the DC motor is 2-A, so the current at this time is 20A, and the starting torque is 6A, and at that time This indicates that the starting current is 52 A.

Now, returning to FIG. 1, in order to obtain a starting torque of 6.5 hA, it is necessary that the power supply control transistor 10 has enough margin to allow a current of 52 hA or more to flow through the DC motor.

Suppose that the DC current amplification factor of the transistor 10 at saturation is 4.
If it is set to 0, it is necessary to flow a base current of 13 hA or more. Since the base current of the power supply control transistor 0 flows through the resistor 28, the upper limit of the resistance value of the resistor 20 is determined from the above conditions.

However, during constant speed control, that much base current is not required, so the base current of the power supply control transistor 0 flows only about 1 to 2 hA.
Most of the current flows through diodes 8,9.

During constant speed control, a part of the current flowing through the diode 8 is indispensable as a bias current to obtain a reference voltage by passing a forward current through the diode, but at least 2~ It is about 3 hA ~ more than that becomes a loss current.

Now, in Fig. 3, when the power supply control transistor fin is saturated, the emitter potential of the detection transistor 7 rises and the forward current stops flowing between the diode fin and the base Q emitter of the starting switching transistor umbrella tortoise. ``When a load torque greater than the maximum torque is applied, the switching transistor is empty.
is in the on state, so if the resistance value of the resistor 20b is made sufficiently small, the switching transistor 22 can supply the base current necessary for saturating the power supply control transistor turtle fin.On the other hand, the constant speed Since the switching transistor 22 is in the off state during control, the loss current in the control circuit can be significantly reduced by selecting the resistance value of the light resistor 2 fin a to a value that allows the minimum current required for constant speed control to flow. In Figure 3,
When the constant voltage diode Kumokawa connected to the emitter of the transistor 22 and the starting switching transistor Hokoryu are turned on, the switching transistor 22
This element ensures that the switch is turned off.

Now, the back diagram shows another embodiment of the present invention, and even if the connection positions of the diode flea, the second switching transistor, and the switching transistor 22 are changed compared to the one shown in FIG. 2, the operation will be the same. This is exactly the same as in Figure 2.

6 also shows another embodiment of the present invention, in which a diode 25 is connected between the collector of the starting switching transistor 2 and the base of the detection transistor 7. In this circuit, the starting switching transistor 21 is in an OFF state until the DC motor is started, so the base current flows through the resistor 8 and the diode 25 to the detection transistor 7.

After the DC motor starts, switching transistor 2
Since the diode 25 is turned on and its collector potential becomes approximately equal to the emitter potential of the detection transistor 7, the diode 25 is turned off and the operation of the starting circuit is completed. Furthermore, after starting the DC motor, the base-emitter junction of the switching transistor 21 is connected to the reference voltage diode.
By appropriately selecting its resistance value, the resistor 18 can be used as a resistor for compensating voltage characteristics.In the figure, the diode 26 is the only element that contributes only to startup. becomes.

Furthermore, ``Figure 7 also shows an embodiment of the present invention.''
Since this circuit uses two differentially connected detection transistors 7 and 26, this is the base of two starting switching transistors.

The reference voltage for constant speed control is obtained only by the emitter-to-emitter junction. As shown above, in the speed control device for a small DC motor of the present invention, the DC motor is included on one side and the bridge circuit is constructed with one side of the DC motor connected directly to the power supply line. A detection transistor 7 whose base is tangent to the detection terminal a on the side not including the DC motor, and whose emitter is connected to the power source through a resistor.
A base current is supplied from the collector of the detection transistor inserted between the other power supply line (in the embodiment, the positive side power supply line) and the other power supply terminal of the bridge circuit, and the base current is supplied to the bridge. A power supply control transistor that supplies power to the circuit is connected to the base in the current path from the other detection terminal of the bridge circuit to the emitter of the detection transistor.

When the emitter is connected, the collector is connected to the other power supply line through the starting resistor. A starting switching transistor 21 that can generate a part or all of a reference voltage for control; and a starting switching transistor 21 that detects the collector potential of the starting switching transistor and detects the collector potential of the starting switching transistor so that when the starting switching transistor is in an OFF state, the power feeding control transistor is activated. Starting circuit means for supplying starting fin flow to the base (Figs. 2 and 3, 5)
In the embodiment shown, the start-up circuit means is constituted by a second switching transistor 22, and in the embodiment shown in FIGS.
In the illustrated embodiment, the diode 25 and the detection transistor 7 constitute the starting circuit means. ), which has great effects such as minimizing the number of parts required for startup and reducing power loss current.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing a conventional example, FIGS. 2 and 3 are circuit connection diagrams of a speed control device for a 4-type DC motor in an embodiment of the present invention, and FIG. 3 is a diagram showing typical characteristics of a DC motor to explain the effects of the device shown in FIG. 3, and FIGS. It is a circuit connection diagram. 1... Rotor of DC motor, 4, 5, 6...
・Resistor "7...detection transistor, 10...
・Power supply control transistor, 18... Starting resistor, 2
0...Resistance, 20a, 20b...Resistance, 2
1... Switching transistor for starting, 22
...Second switching transistor, 25...diode. Figure 3 Figure 1 Figure 2 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A base is connected to a detection terminal on a side not including the DC motor of a bridge circuit configured to include a DC motor on one side and directly connected to one power supply terminal or a power supply line, The emitter is inserted between a detection transistor connected to the power supply line through a resistor, the other power supply line and the other power supply terminal of the bridge circuit, and a base current is supplied from the collector of the detection transistor to the bridge circuit. A power supply control transistor that supplies power to the circuit is connected between its base and emitter in a current path from the other detection terminal of the bridge circuit to the emitter of the detection transistor, and the collector is connected to the other terminal of the bridge circuit through a starting resistor. a starting switching transistor that is connected to a power supply line, and after the DC motor is started, part or all of a reference voltage for controlling the rotational speed is generated between the base and emitter of the DC motor; A speed control device for a small DC motor, comprising a starting circuit means for supplying a starting current to the base of the power supply control transistor when the starting switching transistor whose collector potential has been detected is in an off state. 2 A second transistor is connected to the collector of the starting switching transistor.
The starting circuit means is constructed by connecting the bases of the switching transistors, the collectors of the second switching transistors to the bases of the power supply control transistors, and the emitters connected to the power supply line on one power supply terminal side of the bridge circuit. A speed control device for a small direct current motor according to claim 1, comprising: 3. The speed of the small DC motor according to claim 1, wherein a diode is connected between the collector of the starting switching transistor and the base of the detection transistor, and the starting circuit means is constituted by the diode and the detection transistor. Control device.