JP2002209393A - Fan motor drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly and surely start a fan motor and rotate it at a low speed in a steady operating state using a simple constitution. SOLUTION: A fan motor drive circuit is provided with a regulator circuit 11 connected to a direct-current power supply 20; a resistance-type voltage division circuit 12 that divides an output voltage Vout of the regulator circuit 11 by resistance and feeds it back to the reference voltage terminal Vref of the regulator circuit 11; a time constant circuit 13 connected with the reference voltage terminal Vref; and a series circuit 14 comprising a resistor 14A and a switching element 14B connected in series with the time constant circuit 13. The output voltage Vout of the regulator circuit 11 is increased at start, only for a certain time interval according to the time constant by the time constant circuit 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan motor drive circuit.

[0002]

2. Description of the Related Art When an electric circuit component or the like generating a large amount of heat is accommodated in a small-capacity housing, a cooling fan is used to suppress a rise in temperature of the electric circuit component or the like.

Conventionally, a DC fan used in a DC motor as a fan motor has been driven by, for example, a fan motor drive circuit having a configuration as shown in FIG.

The fan motor drive circuit 10 shown in FIG.
0 is a regulator circuit 1 connected to the DC power supply 110
01 and the output voltage Vout of the regulator circuit 101.
And a resistance dividing circuit 102 that divides the resistance by a resistor and feeds back to the reference voltage terminal Vref of the regulator circuit 101.
As shown in FIG. 4, the DC fan 130 is driven by the output voltage Vout stabilized by the regulator circuit 101 from the input voltage Vin provided by the DC power supply 110.

[0005]

By the way, in order to suppress the generation of noise due to the rotation of the cooling fan, the drive voltage is reduced within a range where the required cooling capacity can be ensured, and the cooling fan is operated at a low speed and silently. In such a case, in the conventional fan motor drive circuit 100, a large rotational torque is increased when the DC fan 130 is started, and a voltage higher than the drive voltage during the stable operation is required.
There is a problem that a start failure of 0 easily occurs. In addition,
If the drive voltage at the time of stable operation is increased in order to reliably start the DC fan 130, noise increases with an increase in rotation speed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fan motor drive that can start a fan motor smoothly and reliably with a simple configuration and can rotate at a low speed in a steady operation state in view of the above-mentioned conventional problems. It is to provide a circuit.

[0007]

SUMMARY OF THE INVENTION A fan motor drive circuit according to the present invention has a regulator circuit connected to a DC power supply, and divides an output voltage of the regulator circuit by resistance and feeds it back to a reference voltage terminal of the regulator circuit. A resistor dividing circuit; and a time constant circuit connected to the reference voltage terminal, wherein the output voltage of the regulator circuit is increased at the time of startup for a fixed time according to a time constant of the time constant circuit. .

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

A fan motor drive circuit according to the present invention is configured, for example, as shown in FIG. A fan motor drive circuit 10 shown in FIG. 1 includes a regulator circuit 11 connected to a DC power supply 20 and an output voltage Vout of the regulator circuit 11 which is divided by a resistor.
A resistance dividing circuit 12 that feeds back to the reference voltage terminal Vref of
The time constant circuit 13 connected to the reference voltage terminal Vref
And a resistor 14A, a switching element 14B, and a series circuit 14 connected in parallel to the time constant circuit 13.

The resistor dividing circuit 12 is composed of two resistors 12A and 12B connected in series between the output terminal OUT of the regulator circuit 11 and the ground, and a connection point between the two resistors 12A and 12B is connected to the regulator 12A. Circuit 11
Is connected to the reference voltage terminal Vref. This resistance dividing circuit 12 is connected to the output voltage Vou of the regulator circuit 11.
The resistance t is divided by the resistance ratio R1: R2 of the resistors 12A and 12B, and a voltage proportional to the output voltage Vout is fed back to the reference voltage terminal Vref of the regulator circuit 11.

The time constant circuit 13 includes a resistor 13A and a capacitor 13B connected in series between the reference voltage terminal Vref of the regulator circuit 11 and ground.
The time constant circuit 13 is composed of the combined resistance of the resistance values R1 and R2 of the resistors 12A and 12B and the resistance value R3 of the resistor 13A and the capacitor 13
A time constant by the capacitance C of B is applied to the reference voltage terminal Vref of the regulator circuit 11.

The fan motor drive circuit 10 is for driving a cooling fan of a component in a unit in a device such as a liquid crystal projector.
The DC fan 30 is driven by the stabilized output voltage Vout obtained by the regulator circuit 11 from the input voltage Vin given by

The output terminal OU of the regulator circuit 11
The output voltage Vout obtained at T is determined by the voltage applied to the reference voltage terminal Vref.

In the normal operation state, the regulator circuit 11 feeds back a voltage proportional to the output voltage Vout obtained at the output terminal OUT to the reference voltage terminal Vref via the resistance dividing circuit 12, thereby providing the DC power supply. 20 is the output voltage V stabilized from the input voltage Vin given by
out, and the DC fan 30 is driven by this stabilized output voltage Vout.

In this fan motor drive circuit 10,
At start-up, the voltage fed back to the reference voltage terminal Vref of the regulator circuit 11 forms the time constant circuit 13 with the resistance values R1 and R2 of the resistors 12A and 12B constituting the resistance dividing circuit 12. Resistance value R of resistor 13A
3 and the capacitance C of the capacitor 13B.
Then, the output voltage Vout obtained at the output terminal OUT of the regulator circuit 11 increases by the time (Hx) for charging the capacitor 13B as shown in FIG. In this way, by increasing the output voltage Vout of the regulator circuit 11 for a fixed time according to the time constant of the time constant circuit 13 at the time of startup, the DC fan 30 can be started smoothly and reliably.

When the capacitor 13B is charged, the impedance of the time constant circuit 13 increases and becomes negligible. The output voltage Vout obtained at the output terminal OUT of the regulator circuit 11 is as shown in FIG. The resistance 12 constituting the resistance division circuit 12
The voltage drops to the voltage Vstb determined by the resistance ratio R1: R2 of A, 12B.

This operation state is a standby operation state in which a temperature rise in a unit in a device such as a liquid crystal projector is small, and the fan motor drive circuit 10 uses the voltage Vstb stabilized by the regulator circuit 11 to operate the DC fan 30. To operate the DC fan 30, that is, the cooling fan, at a low speed to operate silently.

In the fan motor drive circuit 10, the reference voltage terminal Vref of the regulator circuit 11 is used.
When the switching element 14B of the series circuit 14 connected in parallel to the time constant circuit 13 is closed, the resistance value R1 of the resistances 12A and 12B constituting the resistance dividing circuit 12 is adjusted. , R2 and the series circuit 1
4 is determined by the combined resistance value of the resistance value R4 of the four resistors 14A. Thus, when the switching element 14B is closed, the output terminal O of the regulator circuit 11 is closed.
The output voltage Vout obtained in the UT is, as shown in FIG.
It rises to Von.

The switching element 14B is closed by an operation state in which a temperature rise in the unit of the apparatus such as the liquid crystal projector is large, for example, a fan control signal indicating that the projector light source is turned on. In this operation state, the DC fan 30 is rotated at high speed by the voltage Von stabilized by the regulator circuit 11, and the cooling capacity can be increased.

[0020]

In the fan motor drive circuit according to the present invention, the start-up is performed smoothly and reliably by increasing the output voltage of the regulator circuit for a fixed time according to the time constant of the time constant circuit at the time of start-up. In this state, the drive voltage can be reduced within a range where the required cooling capacity can be ensured, and the cooling fan can be operated at low speed and silent.

Further, the fan motor drive circuit closes a switching element of a series circuit of a resistor and a switching element connected in parallel to the time constant circuit,
The cooling capacity can be increased by rotating the cooling fan at a high speed.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a configuration of a fan motor drive circuit according to the present invention.

FIG. 2 is an explanatory diagram of an operation of the fan motor drive circuit.

FIG. 3 is a block circuit diagram showing a configuration of a conventional fan motor drive circuit.

FIG. 4 is an explanatory diagram of an operation of the conventional fan motor drive circuit.

[Explanation of symbols]

Reference Signs List 10 fan motor drive circuit, 11 regulator circuit, 12 resistance division circuit, 12A, 12B resistance, 13
Time constant circuit, 13A resistor, 13B capacitor, 1
4 Series circuit, 14A resistor, 14B switching element, 20 DC power supply, 30 DC motor

Claims (2)

[Claims] 1. A regulator circuit connected to a DC power supply, a resistance dividing circuit that divides an output voltage of the regulator circuit by resistance and feeds back to a reference voltage terminal of the regulator circuit, and when connected to the reference voltage terminal. A fan motor drive circuit, comprising: a constant circuit, wherein the output voltage of the regulator circuit is increased at the time of startup for a fixed time according to the time constant of the time constant circuit. 2. The fan motor drive circuit according to claim 1, further comprising a series circuit of a resistor and a switching element connected in parallel to said time constant circuit.