JP2577446Y2 - DC fan motor speed controller - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for a DC fan motor used in OA equipment such as a computer and a copying machine.

[0002]

2. Description of the Related Art Recently, noise is a problem in office automation equipment such as computers and copiers that use a DC fan motor because they are used in quiet offices. There is a demand for a temperature variable speed function that raises the air volume and lowers the rotation speed at low temperatures to reduce the noise generated by the fan.

The present inventor has proposed in Japanese Patent Application No. 3-68248 for realizing such a DC fan motor of variable temperature speed. That is, this DC fan motor uses a negative characteristic thermistor to vary the rotation speed of the fan motor in accordance with the ambient temperature.

FIG. 3 shows a drive control circuit diagram of the temperature variable speed DC fan motor. In FIG. 3, the rotor magnet 1 has 2n (n is an integer) magnetic poles,
Around this rotor magnet 1, a motor drive coil 2,
3 are provided. The drive transistors 4 and 5 supply a current to the motor drive coils 2 and 3 to drive the motor. The Hall element 6 detects the magnetic flux of the rotor magnet 1 and detects the rotational position of the rotor. A current distributor 8 to which the Hall element 6 is connected via an amplifier 7 is connected to the bases of the drive transistors 4 and 5 and drives the drive transistor 4 in accordance with an output signal from the amplifier 7 for amplifying a signal from the Hall element 6. , 5 are switched. The driving transistors 4 and 5, the Hall element 6, the amplifier 7 and the current distributor 8 constitute a DC fan motor driving device 9.

A portion surrounded by a broken line is the speed control device 10, and a common connection point of the motor drive coils 2 and 3 is connected to a collector of the power supply transistor 11, and an emitter thereof is grounded. The power supply transistor 11 and a collector of a transistor 12 forming a current mirror circuit are connected to a power supply terminal f via a first resistor (load change setting resistor) 13 and a second resistor (speed setting resistor) 14. Is connected to the collector of the constant current transistor 15 through the gate. The negative input terminal of the second error amplifier 16 is connected to the reference voltage source 17.
And its output terminal is a constant current transistor
The emitter is connected to the positive input terminal of the second error amplifier 16 by negative feedback of the emitter potential. The reference voltage source 17 is fed back by the error amplifier 16, and the emitter potential of the constant current transistor 15 becomes the same as the reference voltage. A negative characteristic thermistor resistor 18 is connected to the emitter of the constant current transistor 15, and supplies a constant current having a positive characteristic to the speed setting resistor 14 to generate a reference voltage for determining a motor speed. This voltage is input to the + input terminal of the first error amplifier 19, the voltage of the collector of the power supply transistor 11 is input to the-input terminal of the first error amplifier 19, and the output terminal of the first error amplifier 19 is Transistor
11 is connected to the base of the transistor 12 and drives the current mirror circuit by the output of the first error amplifier 19.

Here, terminals a and b are connected to the speed control device 10.
And terminals d and e in addition to the grounded terminal c.
Is connected to the power supply terminal f via the load fluctuation setting resistor 13,
The terminal b is connected to a DC fan motor which is a DC brushless motor. The collector of the constant current transistor 15 is connected to the terminal d, and the emitter is connected to the terminal e. The + input terminal of the error amplifier 16 is connected to the terminal e, and the − input terminal is connected to the terminal c via the reference voltage source 17.
Further, the terminal e is grounded via the thermistor resistor 18 and the terminal c, the terminal d is connected to the terminal a via the resistor 14, and a current proportional to the current flowing through the terminal b always flows through the terminal a. It is configured.

The operation of the above configuration will be described below. The Hall element 6 of the driving device 9 of the DC fan motor senses the magnetic flux of the rotor magnet 1 of the motor, amplifies it by the amplifier 7 and inputs the amplified current to the current distributor 8. The current distributor 8 determines a coil to be energized with respect to the output signal of the Hall element 6 and switches the energization of the drive transistors 4 and 5 with the output from the current distributor 8 to rotate the motor. At this time, if the induced voltage generated in the A-phase and B-phase motor drive coils 2 and 3 is Ea, the coil resistance is Rm, and the saturation voltage of the drive transistors 4 and 5 is Vsat, the voltage between the power supply terminal f and the terminal b is The generated voltage Vo is as follows: Vo = Ea + Rm * I + Vsat (1) Here, Vsat is the saturation voltage of the driving transistors 4 and 5 (generally about 0.1 to 0.2 V), which is a value that is negligibly small as compared with the other two terms on the right side.

Next, the operation of the speed control device 10 indicated by the broken line will be described. When the rotation speed of the DC fan motor changes due to load fluctuations, etc., the induced voltage Ea generated in the motor changes,
Accordingly, the voltage Vo also changes according to the above equation (1).
The change is compared with a reference voltage by the error amplifier 19, and the output is transmitted to the output transistor 11 to control the output current Im.

Further, the resistance value of the thermistor resistor 18 is set to Rs
If it is set to 1, Rs1 can be expressed by Rs1 = ReexpB (1 / To-1 / T) (2) Here, R is a resistance value at an ambient temperature of 25 ° C., B is a temperature coefficient, To is an ambient temperature (absolute temperature), and T is 25 ° C. (298 K absolute temperature).

It is assumed that the resistance value of the resistor 14 is Rs2, and the current values Is, Im, and Ik flow in the directions of the arrows, respectively. Since this current value Ik is constituted by a current distribution circuit connected by a current mirror so that a current of 1 / k of Im always flows, Ik = Im / k.

The current value Is flowing through the constant current transistor 15 has the same potential as the emitter potential of the constant current transistor 15 and the reference voltage of the reference voltage source 17 due to the voltage negative feedback effect of the error amplifier 16, so that Is = Vref / Rs1 (3) Here, the voltage Vin (+) from the power supply terminal f to the + input terminal of the error amplifier 19 is Vin (+) = Rs2 * Is + (Ik + Is) * Rt (4).

On the other hand, the voltage Vo from the power supply terminal f to the negative input terminal of the error amplifier 19 is as follows: Vo = Ea + Rm * Im (5) Since both input terminals of 19 are subjected to negative feedback and operate to have the same voltage, Vo = Vin (+) (6), and the rotation speed N of the DC fan motor is N = Vref (Rt / Rs1 + Rs2). / Rs1) / Ka (7), and the motor speed N is inversely proportional to the resistance value Rs1 of the negative characteristic thermistor resistor 18, and the negative characteristic thermistor resistance is used as the resistance.
The use of 18 has realized a temperature-controlled DC fan motor in which the number of revolutions N of the fan motor is reduced at low temperatures to perform a silent operation and increased at high temperatures to increase the air volume.

[0013]

However, in the above-described conventional speed control device for a temperature-variable speed fan motor, it is necessary to rapidly change the rotation speed in a narrow temperature range in order to eliminate a sense of incongruity. The temperature gradient is increased. In this case, in the above specification, as shown in FIG. 4, the motor rotation speed is too low at a low temperature, so that there is a possibility that the required air volume as a fan motor becomes insufficient or the starting torque of the motor becomes insufficient.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a DC fan motor speed control device capable of preventing the motor speed from excessively decreasing at low temperatures.

[0015]

In order to solve the above problems, a DC fan motor speed controller according to the present invention comprises a first DC fan motor having a collector connected to a coil of the DC fan motor supplied with power from a power supply terminal. A transistor, a second transistor having a base connected in common with the first transistor to form a current mirror circuit, a first resistor connected between a collector of the second transistor and a power supply terminal, A first error amplifier having one input terminal connected to the collector of the first transistor and an output terminal connected to the bases of the first and second transistors, and an output terminal of the second error amplifier connected to the base; Is connected, a third transistor having a negative temperature coefficient thermistor connected between the emitter and the ground terminal, and a reference voltage source connected to a negative input terminal of the second error amplifier. An input terminal connected to an emitter of a third transistor, comprising: a series circuit including a constant voltage element and a second resistor interposed between the first resistor and a collector of the third transistor; By generating a reference voltage having a positive temperature characteristic at both ends of the first error amplifier, and connecting a connection point between the collector of the third transistor and the constant voltage element to the other input terminal of the first error amplifier. The motor speed of the DC fan motor is controlled in accordance with the temperature characteristics of the reference voltage.

[0016]

With the above arrangement, a constant current having a positive temperature characteristic is supplied to a series circuit composed of a constant voltage element and a second resistor, and a reference voltage for determining a motor speed is generated at both ends of the series circuit. Since the motor speed of the DC fan motor is controlled according to the temperature characteristics of the reference voltage, the speed of the DC fan motor is low when the temperature is low, and the speed of the DC fan motor is high when the temperature is high. As a result, the minimum motor rotation speed at low temperature is set, and the motor rotation speed at low temperature does not excessively decrease unlike the related art.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It is to be noted that components having the same functions and effects as those of the conventional example are denoted by the same reference numerals and description thereof is omitted.

FIG. 1 is a drive control circuit diagram of a temperature variable speed DC fan motor showing one embodiment of the present invention. In FIG. 1, a power supply transistor 11 having a collector connected to motor drive coils 2 and 3 of a DC fan motor which is supplied with power from a power supply terminal f, which is a power supply terminal, via drive transistors 4 and 5; And a transistor 12 having a base commonly connected to form a current mirror circuit. A second error amplifier 16 is connected to the base, and a negative characteristic thermistor resistor is connected between the emitter and the ground terminal g.
A series circuit comprising a constant voltage element 21 and a speed setting resistor 14 is provided between the collector of the constant current transistor 15 to which the resistor 18 is connected and the load fluctuation setting resistor 13, and a positive temperature characteristic is provided at both ends of the series circuit. Is generated. Further, the error amplifier 19 has a negative input terminal connected to the collector of the power supply transistor 11, a positive input terminal connected to a connection point between the collector of the constant current transistor 15 and the constant voltage element 21, and an output terminal connected to the power supply transistor.
It is connected to the base of the transistor 11 and the transistor 12, whereby the motor speed of the DC fan motor is controlled in accordance with the temperature characteristics of the reference voltage generated at both ends of the series circuit. Thus, the DC fan motor speed controller 22 is configured.

That is, a negative characteristic thermistor resistor 18 is connected to the emitter of the constant current transistor 15, and the constant voltage element
A constant current having a positive characteristic is supplied to a series circuit consisting of 21 and the speed setting resistor 14 to generate a reference voltage for determining the motor speed, and this reference voltage is input to the error amplifier 19 and compared with the voltage at the terminal b. In this configuration, the current mirror image circuit is driven by the output of the error amplifier 19.

The operation of the above configuration will be described below. First, the reference voltage source 17 is fed back by the second error amplifier 16, and the emitter potential of the constant current transistor 15 becomes equal to this reference voltage. Further, a thermistor resistor 18 is connected to the emitter of the constant current transistor 15, and the collector is connected to the + input terminal of the error amplifier 19. If the resistance value of the thermistor resistor 18 is Rs1, the resistance value Rs1 is Rs1 = ReexpB (1 / To-1 / T) (8) Here, R is a resistance value at an ambient temperature of 25 ° C., B is a temperature coefficient, T0 is an ambient temperature (absolute temperature), and T is 25 ° C. (absolute temperature 298 K).

The resistance value of the speed setting resistor 14 is Rs2, and the current values Is, Im, and Ik are current values flowing in the directions of the arrows. Here, the current value Ik is always 1 / the current value Im by the current distribution circuit connected by the current mirror.
1k = I
m / k.

The current value Is flowing through the constant current transistor 15 has the same potential as the emitter potential of the constant current transistor 15 and the reference voltage Vref of the reference voltage source 17 due to the voltage negative feedback action of the error amplifier 16, so that Is = Vref / Rs1 (9) Here, the voltage Vin (+) from the power supply terminal f to the + input terminal of the error amplifier 19 is Vin (+) = Vz + Rs2 * Is + (Ik + Is) *, where Vz is the voltage of the constant voltage element 21. Rt (10).

On the other hand, the voltage Vo from the power supply terminal f to the negative input terminal of the error amplifier 19 is as follows: Vo = Ea + Rm * Im (11) Since both input terminals of the amplifier 19 are subjected to negative feedback and operate so as to have the same voltage, Vo = Vin (+) (12), and the induced voltage Ea of the DC fan motor is Ea = Vz + Vref. (Rt / Rs1 + Rs2 / Rs1)-(Rm-Rt / k) * Im (13) From this, if the resistance value Rt of the load fluctuation setting resistor 13 is adjusted to be Rt = K * Rm (14), the third term on the right side of the equation (13) disappears, and Ea = Vz + Vref ( Rt / Rs1 + Rs2 / Rs1) (15), and the DC fan motor is driven such that the induced voltage Ea is always a constant voltage. In other words, assuming that the rotation speed of the motor is N and the power generation constant is Ka, Ea = Ka * N (16). Therefore, the rotation speed N of the DC fan motor is N = {Vz + Vref (Rt / Rs1 + Rs2 / Rs1)}. / Ka (17), and the DC fan motor has a constant rotational speed without being affected by the load torque.

Here, the resistance value Rs1 of the thermistor resistor 18
Has a negative temperature characteristic from the equation (8), but according to the equation (17), the rotation speed N of the motor is
Even when the motor operates so as to increase at low temperature and decrease the rotation speed, the motor rotation speed N is constant as shown by the solid line in FIG. 2 due to the effect of the constant voltage element 21, and N = VZ / Ka (18) Become.

Accordingly, as shown by the dotted line in FIG. 2, the motor rotation speed N does not decrease, and the problem that the required air volume as the fan motor is insufficient or the motor does not have sufficient starting torque does not occur. In addition to increasing the air flow of the fan motor to increase the cooling effect, the fan speed is reduced at normal temperature to reduce the noise generated by the fan motor, but the motor speed is abnormally reduced too much at low temperature. Can be prevented.

[0026]

As described above, according to the present invention, in the speed control of a DC fan motor, a reference voltage is constituted by a series circuit of a constant voltage element and a second resistor, and a positive temperature characteristic is given to this series circuit. By controlling the drive voltage of the DC fan motor using a speed controller as a configuration with a connected constant current source, it is possible to reduce the noise of the DC fan motor and increase the air volume at high temperatures and at low temperatures. An object of the present invention is to provide a temperature-variable-speed DC fan motor having a simple configuration capable of preventing an excessive decrease in the motor rotation speed and improving the performance.

[Brief description of the drawings]

FIG. 1 is a drive control circuit diagram of a temperature variable speed DC fan motor showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a motor speed and an ambient temperature of the temperature variable speed DC fan motor of FIG. 1;

FIG. 3 is a drive control circuit diagram of a conventional temperature variable speed DC fan motor.

FIG. 4 is a diagram illustrating a relationship between a motor speed and an ambient temperature of the temperature variable speed DC fan motor of FIG. 3;

[Explanation of symbols]

 2, 3 Motor drive coil 11 Power supply transistor 12 Transistor 13 Load change setting resistor 14 Speed setting resistor 15 Constant current transistor 16, 19 Error amplifier 17 Reference voltage source 18 Thermistor resistor 21 Constant voltage element 22 Speed controller

Claims (1)

(57) [Scope of request for utility model registration] 1. A first transistor having a collector connected to a coil of a DC fan motor supplied with power from a power supply terminal, and a second transistor having a base connected in common with the first transistor to form a current mirror circuit. Transistors and
A first resistor connected between the collector of the second transistor and a power supply terminal, one input terminal connected to the collector of the first transistor, and an output terminal connected to the first and second transistors First connected to the base of
An error amplifier, a third transistor having an output terminal of the second error amplifier connected to the base, a negative temperature coefficient thermistor connected between the emitter and the ground terminal, and a reference voltage applied to a negative input terminal of the second error amplifier. A positive input terminal is connected to the emitter of the third transistor, and a series circuit including a constant voltage element and a second resistor interposed between the first resistor and the collector of the third transistor. Wherein a reference voltage having a positive temperature characteristic is generated at both ends of the series circuit, and a connection point between the collector of the third transistor and the constant voltage element is connected to the other input of the first error amplifier. A speed control device for a DC fan motor configured to control a motor rotation speed of the DC fan motor according to a temperature characteristic of the reference voltage by being connected to a terminal.