JPH058796Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is a DC fan motor drive circuit that detects the rotor position with a rotor position sensor and supplies excitation current to a specific excitation winding to drive the fan motor. It is related to.

(Prior Art) For example, a cooling fan for electronic equipment needs to be rotated at a constant rotational speed at all times.

However, the conventional DC fan motor drive circuit has a drawback that the rotational speed fluctuates when there is a fluctuation in the power supply voltage.

Figure 1 shows the relationship between input voltage and fan rotation speed, and the relationship between input voltage and input current. In the figure, N ₂ shows the conventional input voltage vs. fan rotation speed characteristic, and I ₂ It shows the characteristics of input voltage versus input current.

(Purpose of the invention) The object of the invention is to be able to rotate a DC fan at a constant rotation speed regardless of changes in power supply voltage. To provide a DC fan motor drive circuit.

(Structure of the invention) In the present invention, first and second excitation windings of a DC fan motor are connected in parallel between a positive line and a ground line, and the first excitation winding has a first winding. An excitation transistor is connected in series, a second winding excitation transistor is connected in series to the second excitation winding, and a position of the rotor of the DC fan motor is connected between the positive line and the ground line. A rotor position sensor is connected to detect the first and second positions, and the rotor position sensor alternately detects the first and second positions.
In a DC fan motor drive circuit that drives the DC fan motor by applying an excitation signal to a winding excitation transistor, a are each connected to a fan rotation speed control circuit, and each of the fan rotation speed control circuits has a protective resistor connected between the output terminal of the rotor position sensor and the base of the winding excitation transistor;
a control transistor whose collector and emitter are connected between a connection between the protective resistor and the base of the winding excitation transistor and the ground line; and an output terminal of the protective resistor and the rotor position sensor. a series circuit of a charging resistor and a charging capacitor connected between the connecting portion of the charging resistor and the charging capacitor, and a connecting portion of the charging resistor and the charging capacitor and the base of the control transistor; The device is characterized in that each of the devices includes a connected Zener diode, an oscillation prevention resistor connected between a connecting portion between the anode of the Zener diode and the base of the control transistor, and the ground line. It is something to do.

With this configuration, when the power supply voltage increases, the time required for the charging voltage of the charging capacitor to reach the Zener voltage of the Zener diode is shortened, and as a result, the control transistor is turned on quickly and output from the rotor position sensor. The increase in the rotational speed of the DC fan motor is suppressed by shortening the pulse width of the output pulse signal and shortening the conduction period of the winding excitation transistor. Conversely, when the power supply voltage decreases, the operation is reverse to that described above, and the conduction period of the winding excitation transistor is lengthened to suppress a decrease in the rotational speed of the DC fan motor. Therefore, even if the power supply voltage fluctuates, the rotational speed of the DC fan motor can be kept constant.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an embodiment of the present invention. As shown in the figure, the DC fan motor drive circuit of this embodiment has a plus line 2 connected to a plus side power input terminal 1 and a ground line 4 connected to a ground side power input terminal 3. Between the positive line 2 and the earth line 4, first and second excitation windings 5 and 6 of a DC fan motor are connected in parallel. Surge killer diodes 7 and 8 are connected in parallel to these first and second excitation windings 5 and 6, respectively, and first and second winding excitation transistors 9 and 10 are connected in series. A rotor position sensor 11 for detecting the rotor position of the DC fan motor is connected between the positive line 2 and the earth line 4 via a resistor 12. This rotor position sensor 11 includes a position sensor main circuit 13 mainly composed of a Hall element, and a pulse signal mainly supplied from this position sensor main circuit 13 to first and second winding excitation transistors 9 and 10 alternately. It is composed of first and second operational amplifiers 14 and 15 that distribute and output signals. Each operational amplifier 1
4, 15 are connected to operational resistors 16, 17, 18, 19 and feedback resistors 20, 21.

Each output end 11A, 1 of the rotor position sensor 11
1B and the first and second winding excitation transistors 9,
Fan rotation speed control circuits 23 and 24, which form the main part of the present invention, are connected to the base of 10, respectively. Each fan rotation speed control circuit 23, 24
is the output end 11A, 1 of the rotor position sensor 11
1B and the first and second winding excitation transistors 9,
Protective resistors 25 and 26 are connected between the base of the transistor 10 and the base of the transistor 10. These protective resistors 2
5, 26 and the bases of the first and second winding excitation transistors 9, 10 and the ground line 4, control transistors 27, 28 are connected, respectively, and the corresponding transistors 9, 10 conduction periods are controlled. Each protective resistor 25, 26 is connected to each operational amplifier 14, 1 when these control transistors 27, 28 are conductive.
This is to prevent the output terminal of No. 5 from becoming low impedance. A charging resistor 29,
30 and a series circuit of charging capacitors 31 and 32 are connected. These charging resistors 29, 30
Zener diodes 33 and 34 are connected between the connecting portions of the charging capacitors 31 and 32 and the bases of the control transistors 27 and 28, with their anodes facing the bases of the control transistors 27 and 28. ing. Zener diode 33,
34 anode and control transistors 27, 28
Anti-oscillation resistors 35 and 36 are connected between the connection point with the base and the ground line 4, and prevent the control transistors 27 and 28 from oscillating when the Zener diodes 33 and 34 are conductive. It's becoming like that.

A rectifying capacitor 37 is connected between the positive power input terminal 1 and the earth power input terminal 3, and a rectifying capacitor 37 is connected to the positive power line 2 at the connection between the positive power input terminal 1 and the rectifying capacitor 37. A rectifier diode 38 is connected in series.

Next, the operation of such a DC fan motor drive circuit will be explained. FIG. 3 shows operating waveforms when the fan rotation speed control circuits 23 and 24 are not provided. Ein is the input voltage, V ₁₄ , V ₁₅
is the output waveform of each rotor position sensor 11, V ₉ ,
_V10 is the output waveform of each winding excitation transistor 9, 10. Rotor position sensor 1 as shown
Output pulses are alternately outputted from 1 and applied to the bases of the respective winding excitation transistors 9 and 10,
Each transistor 9, 10 is made conductive only during the application period of the input pulse, alternately exciting the first and second excitation windings 5, 6, and the DC fan motor is rotationally driven. However, when the fan rotation speed control circuits 23 and 24 do not control the speed,
When the power supply voltage fluctuates and the input voltage Ein changes, each output voltage V ₁₄ , V ₁₅ , V ₉ , V ₁₀ also changes,
The fan rotation speed will change.

FIG. 4 shows operating waveforms when controlled by the fan rotation speed control circuits 23 and 24. When controlled in this way, the input voltage Ein becomes, for example, the third
When the pulse voltage of the output pulse of the rotor position sensor 11 increases compared to the case shown in the figure, the pulse voltage of the output pulse of the rotor position sensor 11 also increases.
reaches the Zener voltage of the Zener diodes 33, 34 more quickly, and when the Zener diodes 33, 34 conduct with that Zener voltage, the control transistors 27, 28 conduct, and the output pulse of the rotor position sensor 11 excites each winding. This prevents the voltage from being applied to the transistors 9 and 10. Therefore, as shown in the figure as V ₉ and V ₁₀ , the conduction period of each winding excitation transistor 9 and 10 is shortened in accordance with the input voltage Ein, thereby suppressing an increase in the fan rotation speed. Similarly, when the power supply voltage decreases, the reverse operation described above is performed, and each winding excitation transistor 9,
The conduction period of 10 becomes longer as the input voltage Ein decreases, thereby suppressing a decrease in the fan rotation speed. Therefore, the fan rotation speed can be kept constant regardless of fluctuations in the power supply voltage.

N ₁ and I ₁ in Fig. 1 are the characteristics of input voltage Ein versus fan rotation speed N when performing control according to the present invention.
N ₁ and the characteristic I ₁ of input voltage Ein versus input current Iin. As is clear from the figure, the rotation speed _N1 of the fan gradually rises from the application of the input voltage and is maintained at a substantially constant rotation speed.

In this DC fan motor drive circuit, if the rotation of the fan is forcibly stopped for some reason, the rotor position sensor 11 either continues to output an output or stops outputting an output. If the output continues, the Zener diode 33,
34 conducts to conduct the control transistors 27 and 28 and cut off the respective winding excitation transistors 9 and 10, thereby preventing the excitation windings 5 and 6 from burning out.

(Effects of the invention) As explained above, the DC fan motor drive circuit according to the invention connects the fan rotation speed control circuit to the electric path from the rotor position sensor to the base of each winding excitation transistor, and eliminates fluctuations in the power supply voltage. When such fluctuation occurs, the operating point of the Zener diode in the circuit is changed to control the pulse width of the output pulse given from the rotor position sensor to each winding excitation transistor, so the rotation of the DC fan motor is The number can be controlled so that it is maintained constant regardless of fluctuations in the power supply voltage. Therefore, the DC fan can be controlled to rotate at a constant rotation speed regardless of changes in the power supply voltage. In particular, this DC fan motor drive circuit has the advantage that it has a very simple circuit configuration and can be implemented at low cost. Furthermore, the fan rotation speed control circuit used in this invention also has a function to automatically stop excitation to each winding excitation transistor when the fan is forcibly stopped, which is very useful in practice. be.

[Brief explanation of the drawing]

Fig. 1 is a comparison diagram of input voltage vs. fan rotation speed characteristics and input voltage vs. input current characteristics between the conventional and the present invention, and Fig. 2 is a circuit diagram of an embodiment of the DC fan motor drive circuit according to the present invention. 3 and 4 are respective operation waveform diagrams for the conventional case and the present invention. 1... Positive side power input terminal, 2... Positive line, 3... Earth side power input terminal, 4... Earth line, 5, 6... First and second excitation windings,
9, 10...Transistor for winding excitation, 11...
Rotor position sensor, 13...position sensor main circuit, 14, 15...first and second operational amplifiers, 2
3, 24...Fan rotation speed control circuit, 25, 26
...Protection resistor, 27, 28...Control transistor, 29,30...Charging resistor, 31,32...
... Charging capacitor, 33, 34... Zener diode, 35, 36... Resistor for preventing oscillation.

Claims (1)

[Scope of utility model registration request] First and second excitation windings of the DC fan motor are connected in parallel between the positive line and the earth line, a first winding excitation transistor is connected in series to the first excitation winding, and the first excitation winding is connected in series to the first excitation winding. A second winding excitation transistor is connected in series to the second excitation winding, and a rotor position sensor for detecting the position of the rotor of the DC fan motor is connected between the positive line and the ground line. , in a DC fan motor drive circuit in which an excitation signal is alternately applied from the rotor position sensor to the first and second winding excitation transistors to drive the DC fan motor, the rotor position sensor and the first, A fan rotation speed control circuit is connected between the base of the second winding excitation transistor, and
Each of the fan rotation speed control circuits includes a protective resistor connected between the output end of the rotor position sensor and the base of the winding excitation transistor, and a connection between the protective resistor and the base of the winding excitation transistor. a control transistor whose collector and emitter are connected between the terminal and the ground line, and a charging resistor whose collector and emitter are connected between the protective resistor and the output terminal of the rotor position sensor and the ground line. and a charging capacitor; a Zener diode connected between the connection between the charging resistor and the charging capacitor and the base of the control transistor; an anode of the Zener diode and the control transistor; 1. A DC fan motor drive circuit comprising a resistor for preventing oscillation connected between a connection portion to a base of a transistor and the ground line.