JPS6062893A - Drive circuit for dc fan motor - Google Patents

Abstract

PURPOSE:To eliminate the generation of a noise by conducting a Zener diode when a counterelectromotive voltage becomes the prescribed value or higher, flowing a forward current through a surge killer diode to absorb the counterelectromotive voltage, thereby maintaining the rotating speed of a fan motor constant. CONSTITUTION:A drive signal is generated from a transistor drive circuit 12 by the output of a rotor position sensor 6, and a switching transistor 9 is conducted. When the drive signal is vanished, a switching transistor 10 is conducted by the drive signal from a transistor drive circuit 13. Thus, exciting windings 3, 4 are alternately excited, and a fan motor is rotatably driven. When the exciting currents of the windings 3, 4 are interrupted, Zener diodes 16, 17 are conducted by the surge voltage, and a forward current is flowed to the diodes 14, 15 to absorb the surge voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a DC fan motor drive circuit.

(Prior Art) In general, if the DC fan motor 1 is described as having four poles, for example, as shown in FIG.
, 2B, 2C, and 2D, the first excitation winding 3 is wound around a pair of poles 2A and 2C that are 180 degrees apart, and the second excitation winding is wound around the remaining pair of poles 2B and 2D. A permanent magnet rotor 5 is arranged concentrically around the outer periphery of the stator core 2, and the position of the magnetic pole of the rotor 5 is detected by a rotor position sensor 6.
The switching transistors connected to the corresponding excitation windings 3 or 4 are turned on, and excitation current is alternately supplied to rotate the rotor 5.

However, in such a fan motor 1, when the excitation windings 3 and 4 are alternately energized and then alternately de-energized after the required energization, as shown in FIG. A large surge voltage et is induced in the excitation winding whose current is cut off, and the rotor 5 is instantaneously attracted by the magnetization effect of the current due to the large surge voltage e1, and this attraction occurs when the excitation current is cut off. Since this happens every time, the fan motor 1 has the disadvantage of generating noise.

In order to prevent this, surge killer diodes are connected in parallel to each of the excitation windings 3 and 4, and the surge voltage e+f is absorbed by these diodes. In this way, the noise can be eliminated.

However, when the surge killer diode is connected in this way, the unexcited excitation winding interlinks with the magnetic flux of the permanent magnet of the rotor 5, resulting in a back electromotive force e2.
However, this surge killer diode causes a braking action on the fan motor 1, causing the rotational speed to fall below the rated value.

(Object of the Invention) An object of the present invention is to provide a DC fan motor drive circuit that can solve both the problem of noise and the problem of a decrease in rotational speed.

(Structure of the Invention) A switching transistor is connected in series to an excitation winding of a fan motor, a surge killer diode is connected in parallel to the excitation winding in a direction that can absorb surge voltage, and the transistor is driven by a signal from a transistor drive circuit. In a fan motor drive circuit configured to supply excitation current to the surge killer diode, a Zener diode is connected in series with the surge killer diode in a direction that blocks forward current of the surge killer diode, and the Zener voltage of the Zener diode is is set to a value between the maximum value and the minimum value of the back electromotive voltage induced in the excitation winding.

(Example of Actual Fan) Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. 6. As shown in the figure, in the fan motor drive circuit of this embodiment, the first line of the fan motor is connected between the positive line P connected to the positive power input terminal 7 and the booth line E connected to the negative 1111 power input terminal 8. Second excitation windings 3 and 4 are connected in parallel. These first. The second excitation windings 3 and 4 include the first. The collectors and emitters of the second switching transistors 9 and 10 are connected in series. Further, a rotor position sensor 6 for detecting the position of the magnetic pole of the rotor 5 of the fan motor 1 is connected between the positive lie/P and the earth line E via a resistor 11. The rotor position tti sensor 6 of this embodiment is as follows:
It is mainly composed of a Hall element that detects changes in the magnetic flux of the fan motor 1. A first transistor drive circuit 12 is connected between the output of the rotor position sensor 6 and the first switching transistor 90, and is based on the rotor position signal intermittently output from the rotor position sensor 6. The first switching transistor 9 is configured to output a drive signal intermittently to the first switching transistor 9. A second transistor drive circuit 13 is connected between a connection point A between the first excitation winding 3 and the first switching transistor 9 and the base of the second switching transistor 10. The first switching transistor 1
0 intermittently outputs a drive signal to the 1st. The 20th switching transistors 9 and 10 are driven alternately. 1st. The second excitation winding 3.4 has the first and second excitation windings in parallel, respectively. A second surge killer diode 14,15 is connected in a direction to absorb surge voltage. Torera 1st. These surge killer diodes 1 are oriented to block the forward current of the second surge killer diode 14.15.
4°15 is the first one in series. second zener diode 1
6.17 is connected. These first. The Zener' turtle pressure Ez of the second Zener diode is
It is set to a value between the maximum value and the minimum value of the back electromotive force e2 induced in .

In addition, 18 is a reverse current blocking diode connected to the positive line P on the input terminal 7 side, and 19 is a diode 18.
Positive line P and earth line E on the cathode side of
This is a smoothing capacitor connected between the

Next, the operation of the Hiko fan motor body circuit will be explained with reference to FIGS. 1 to 4. In this fan motor drive circuit, each time a pulse-like signal is output from the rotor position sensor 6, a pulse-like drive signal is output from the first transistor drive circuit 12, and the first switching transistor 9 becomes conductive. An excitation current flows through the excitation winding 3 of 1,
Magnetic pole 2A.

2C is magnetized. When the drive signal disappears, the first switching transistor 9 is cut off and a voltage signal appears on its collector side. This is given to the second transistor drive circuit 13, and a drive signal is outputted from the second transistor drive circuit 13 in a pulse form, the second switching transistor 10 becomes conductive, and an excitation current flows through the second excitation winding 4. , the magnetic poles 2B and 2D are magnetized. In this way, the seven motor 1 is rotationally driven.

By the way, No. 1. When the excitation current of the second excitation windings 3 and 4 is cut off, a large surge voltage el is generated as shown in FIG. 2 (5) (I3), but this surge voltage el is Since the Zener voltage Ez is exceeded, the Zener diodes 16 and 17 are made conductive, and a forward current flows through the surge killer diodes 14 and 1.5, absorbing the surge pressure e1 and applying a brake to the fan motor 1. Suppresses the increase in rotational speed N. Next, the excitation winding 3 in which the surge voltage el was induced,
4, a back electromotive force e2 is induced by interlinkage with the magnetic flux of the permanent magnet of the rotor 5. If this back electromotive voltage e2 exceeds the Zener voltage Ez, the Zener diode 16.17
is made conductive, a forward current flows through the surge killer diode 14, 15, the back electromotive force e2 is absorbed, and a braking action is applied to the fan motor 1 to suppress the increase in rotational speed N. If the back electromotive force e2 is lower than the Zener voltage Ez,
The Zener die and T-dodes 16 and 17 are not conductive, no forward current flows to the surge killer diode 14 and 15, the brake action does not work, the rotation speed N indicates the rotation speed according to the input voltage Ein, and the back electromotive voltage A decrease in the rotational speed N due to this will not occur. Even if the input voltage Ein changes due to load fluctuations, the back electromotive force e2 is generated according to the input voltage Ein, and in the same way, the rotation speed is self-controlled by the Zener diode 16.1.
7 and surge killer diodes 14 and 15, the rotational speed is maintained at a substantially constant value.

FIG. 4 shows an example of the input voltage/rotation speed characteristic I of the DC fan motor drive circuit of the present invention in which the rotation speed N is automatically controlled near the rated value Eo of the input voltage Ein and maintained at the rated rotation speed No. Shown below. Note that characteristic ■ is a conventional characteristic.

(Effects of the Invention) As explained above, in the DC fubun motor drive circuit according to the present invention, the Zener diode is connected in series with the surge killer diode connected in parallel to the excitation winding in a direction that blocks the forward current. is connected, and the Zener voltage of this Zener diode is set to a value between the maximum and minimum values of the back electromotive force induced in the excitation winding, so when the back electromotive voltage exceeds the Zener voltage, the Zener diode When conduction occurs, a forward current flows through the surge killer diode, the back electromotive force is absorbed, and a braking action is applied to the fan motor to suppress the increase in rotational speed.If the back electromotive force is lower than that of the Zener diode, the Zener diode will not conduct. , the forward current does not flow through the surge killer diode, the brake action does not work, the rotation speed shows the rotation speed according to the input voltage, the rotation speed does not decrease due to back electromotive force, and the rotation speed is always maintained constant. This means that self-control is performed so that a constant air flow rate can be easily maintained. ! In addition, the surge voltage when the excitation current is cut off exceeds the Zener voltage, so the Zener diode becomes conductive, forward current flows through the surge killer diode, the surge voltage is absorbed, and the rotor is activated by electromagnetic action based on the large surge voltage. It can also prevent noise from being sucked in.

Therefore, according to the present invention, by simply connecting a Zener diode to a surge killer diode, it is possible to self-control the fan motor to maintain a constant rotational speed and to eliminate noise without reducing the rotational speed. This is very suitable for implementation.

[Brief explanation of the drawing]

Figure 1 is a schematic sectional view of a fan motor, Figure 2 is a waveform diagram showing surge voltage and back electromotive force induced in the excitation winding of a conventional fan motor, and Figure 83 is a DC fan motor drive circuit according to the invention. FIG. 4 is a circuit diagram showing an example of the above, and is a comparison diagram of input voltage/rotation speed characteristics of the present invention and a conventional DC fan motor drive circuit. 1...Fan motor, 2...Stator, 3, 4...
- Excitation winding, 5... Rotor, 6... Rotor position sensor, 9.10... Switching transistor, 12
゜13...Transistor drive circuit, 14.15...
Surge killer diode, 16.17... Zener diode. input? , /I1. E-1 Procedure? 1] Main gate (spontaneous) October 17, 1980 Manabu Shiga, Commissioner of the Japan Patent Office 1, Indication of the incident Patent Application No. 1986-160/186 2, Name of the invention DC fan motor drive circuit 3, Correction 1° Relationship with the case of the person who is involved in the special case [Applicant: Toyo Denki Co., Ltd. 4, Agent: Bunzan Building 6, 4-31-6 Shinbashi, Minato-ku, Tokyo! It! i Ming I
The "Scope of Claims" and "Detailed Description of the Invention" columns in Book IIA of Book II are corrected as follows. (1) The scope of the claims is set forth in the appendix. (2) Delete "Zener voltage" in the 8th line of the 4th page. (3) In page 4, line 10, ``to the value'' is corrected to ``to make it conductive at r1lfi''. (4) Correct "1st" to "2nd" on page 5, line 19. (5) 1° Zener voltage E z, J on page 6, line 10
Delete. (6) On page 6, line 12, ``to l-Mi'' is corrected to ``as if it were guided by clay.'' (7) The 1- Zener voltage EZJ of page 7, line 17 to line 181i is increased by π■ to the voltage EzJ at which [ becomes conductive. (8) Page 8, line 5 to line 6111, line 11, “Zener voltage 1.zJ [Zener diode conduction voltage EzJ
Correct each. (9) On page 9, lines 12 to 113, "Zener voltage of the Zener diode" is corrected to "voltage at which the Zener diode conducts." (10) Increase the "Zener voltage" on page 9, line 15 to [Zener diode conduction voltage]. (11) [From Zener diode] on page 9, line 19
Correct it to "Zener diode conduction voltage J:su". (12) Correct "Zener voltage" in line 7 of page 10 to "conduction voltage of Zener diode". 2. Claims A switching transistor is connected in series to an excitation winding of a fan motor, a surge killer diode is connected in parallel to the excitation winding in a direction that absorbs surge voltage, and 1-
In a fan motor drive circuit in which the transistor is driven by a signal from the transistor drive circuit and an excitation current is supplied, the transistor is connected in a direction to block forward current of the first transistor killer diode. A zeno die A-de is connected in series to the killer tie A-de,
The Zener diode FG, L is set to conduct at a value between the maximum value and the minimum value of the back electromotive force induced in the excitation winding. drive circuit.

Claims (1)

[Claims] A switching transistor is connected in series to the excitation winding of the fan motor, a surge killer diode is connected in parallel to the excitation winding in a direction that can absorb surge voltage, and the transistor is driven by a signal from the transistor drive circuit to reduce the excitation current. In the motor drive circuit in which the power is supplied, a Zener diode is connected in series with the surge killer diode in a direction that blocks forward current of the surge killer diode, and the Zener voltage of the Zener diode is applied to the excitation winding. A direct current motor drive circuit characterized in that the induced back electromotive voltage is set to a value between a maximum value and a minimum value.