JPS62194169A - Controller of fan for cooling - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a cooling fan control device that saves power.

[Conventional technology]

BACKGROUND ART In control equipment that houses electronic components, etc., a cooling fan is generally used because if the internal temperature becomes high, the electronic components may malfunction and reduce reliability. FIG. 2 is a circuit diagram showing a conventional cooling fan control device of this type, which includes a position detection circuit 1 for detecting the rotational position of the fan motor, and an overcurrent detection circuit 2 for detecting overcurrent.
and a driver circuit 3. Then, from the input terminals 4a and 4b, a DC (direct current) power source, for example, DC12
When V is supplied, the above circuit operates, current flows through the coil 5 of the fan motor which is the load, and the cooling fan rotates. At that time, the position detection circuit 1 detects the rotational position of the fan motor and switches the direction of the current flowing through the coil 5, and the overcurrent detection circuit 2 detects the rotational position of the fan motor and switches the direction of the current flowing through the coil 5. If an overcurrent flows during a certain period of time, the system detects this and stops the fan motor to protect the circuit components. Further, the driver circuit 3 performs an operation of causing current to flow through the coil 5 as described above based on a signal from the position detection circuit 1.

Next, the operation of each circuit described above will be explained in detail. First of all,
The position detection circuit 1 is provided with an integrated circuit (hereinafter referred to as a Hall IC) 6 using a Hall element, and when the fan motor rotates, a permanent magnet (not shown) provided in the rotating part of the fan motor is connected to the Hall IC 6. approach. This permanent magnet is configured with alternating N and S poles, so the N and S poles approach the Hall IC 6 alternately, and a digital signal (logical signal) "1" or O is output from the Hall IC 6. Output.

When the output of this hole [C6 is 1'', the inverter transistor TR is turned on, and when it is 0, it is turned off.As the transistor TR is turned on and off, the switching transistors TR2 and TR are also alternately turned on and off. It turns ON. Note that R1 to R4 are current limiting resistors.

Switching transistor TR2 of the position detection circuit 1
, TR3 turns ON and OFF alternately, the driver circuit 3
Then, a current is applied to the coil 5 in response to the ON/OFF signal. That is, when transistor TR3 turns on, base current flows to transistor TR4 through resistor R5,
At the same time, the base current of the transistor TRs flows, turning on the transistors TR4 and TRs, and the base current of the transistor TR6 also flows through the resistor R6, turning it on. As a result, a current flows through the coil 5 of the fan motor in the direction of arrow A through the path of transistor TR6-coil 5-transistor TR5, and the rotor of the fan motor rotates. Due to this rotation, the polarity approaching the Hall IC 6 is reversed, and the transistor TR, becomes 0FFL/to the transistor T.
R2 turns ON. Then, transistor TR2 is turned on.
Then, through the resistor R7, the transistor TR? , T
A base current flows through Ra, turning these TR, , TR, ON. At the same time, base current flows through the resistor R8 in the transistor TR, turning it on. As a result, current flows through the coil 5 in the direction of arrow B through the path of transistor TR9 - coil 5 - transistor TR, and the rotor of the fan motor further rotates. Thereafter, the polarity approaching the hole C6 is changed in the same manner, and currents in the six directions and the B direction alternately flow through the coil 5, and the fan motor continues to rotate.

In addition, TR,. , TR, are protection transistors to be described later, and R9 and RIO are current limiting resistors thereof.

The overcurrent detection circuit 2 also includes a comparator 7, which compares the detected value of the current flowing through the coil 5 with a reference value to detect an overcurrent.

A voltage obtained by dividing the input power supply voltage by resistors R11 and RI2 is applied to the converter tough's inverting input terminal (-) as a reference voltage, and a voltage corresponding to the voltage drop due to resistor R13 is detected to the non-inverting input terminal (+). Applied as a voltage. Then, the comparator 7 compares the reference voltage value with the detected voltage value, and outputs a signal to stop the energization of the coil 5 when the detected voltage value exceeds the reference voltage value. During normal rotation of the fan motor, the voltage drop across resistor R13 is small, so the comparator tough output is "0"; however, when an overcurrent condition occurs and the voltage across resistor R13 becomes higher than the reference voltage, the comparator 7 outputs becomes 1", and the aforementioned protective transistors TR+o, TR, are operated to stop energizing the coil 5. That is, when the output of the comparator 7 becomes "1", the transistors TR, ., TR, , are both turned on, and the output stage transistors "rRs, TR
a has a base voltage of each transistor T R+o
, TR can be suppressed by the Rth collector voltage, so both OF
(Generally, the collector saturation voltage of a transistor is
lower than the base current drive voltage). Therefore, no current flows through the coil 5, and circuit components and the like are protected.

[Problem that the invention seeks to solve]

The conventional fan motor control device is configured as described above, and detects overcurrent by comparing the detected value of the current flowing through the fan motor coil 5 with a predetermined reference value. There is a problem that unnecessary cooling may be performed at low temperatures, such as when used in a cold place, resulting in large power consumption.

The present invention has been made in view of these problems, and an object of the present invention is to provide a cooling fan control device that drives a fan motor in response to temperature changes and saves power.

(Means for solving the problem) Compare the detected value of the current flowing through the fan motor with the reference value,
In a cooling fan control device equipped with an overcurrent detection circuit that limits the drive of the fan motor when the detected value exceeds the reference value and an overcurrent is detected, the above reference value is effectively set when the temperature drops. Reference value changing means is provided for lowering the overcurrent detection level by lowering the overcurrent detection level.

[Effect]

The over7Et current detection circuit compares the detected value of the current flowing through the fan motor with a reference value, detects an overcurrent, and limits the drive of the fan motor. At this time, cooling may become unnecessary at low temperatures, or at this time, the reference value changing means substantially lowers the reference value as the temperature decreases and lowers the overcurrent detection level. Therefore, when the temperature is low, it is determined that there is an overcurrent state, and the drive of the fan motor is restricted.

(Example〕 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a cooling fan control device according to the present invention, in which 1 is a fan motor position detection circuit, 2 is an overcurrent detection circuit, and 3 is a driver circuit for the coil 5. has the same circuit configuration as the conventional one shown in FIG. A thermistor 8 is connected in series to the resistors R and □ of the current detection circuit 2, and the voltage value divided by the thermistor 8 and the resistor R32 is input to one side (- side) of the comparator 7 as a reference voltage value. be done. This thermistor 8 is provided as a reference value changing means for lowering the reference voltage value to lower the overcurrent detection level when the temperature decreases.

In the cooling fan control device configured in this manner, as the temperature rises, the reference voltage value manually input to the comparator 7 increases, and the overcurrent detection level increases. Therefore, the fan motor rotates normally and the rated rotation is maintained. Next, as the temperature decreases, the resistance value of the thermistor 8 increases, so the reference voltage value decreases, and the overcurrent detection level decreases. Therefore, when a small amount of current begins to flow through the coil 5 at low temperatures, it is determined that an overcurrent has occurred, and the output of the comparator 7 becomes 1, and no current flows through the coil 5 as described above. Therefore, unnecessary cooling at low temperatures is prevented, making it possible to save power, and if the fan motor is stopped at low temperatures, wind noise is eliminated, resulting in quiet operation. In addition, when used as a ventilation fan, the fan can be automated in a normal room or a greenhouse, making it useful.

In addition, in the above embodiment, the rotation of the fan motor can be controlled from high speed rotation to low speed rotation by utilizing the fact that the overcurrent detection level changes depending on the resistance value of the thermistor 8, but this thermistor can be used in place of the resistor RI3. It's okay. Even with such a configuration, the reference voltage value can be substantially lowered at low temperatures to lower the overcurrent detection level, and the same effect can be achieved.

Further, the reference value changing means may be replaced with a thermistor and may be a POSISTOR whose resistance value increases as the temperature rises. That is, even if a POSISTOR is connected in place of the resistor R12, the reference voltage value can be lowered at low temperatures. Furthermore, a variable resistor may be used in place of the resistor R12, and in this case, the temperature detection level can be set to an arbitrary level, so it is also possible to freely set the fan rotation speed in response to temperature changes. .

(Effects of the Invention) As explained above, according to the present invention, the reference value for comparison with the detected value of the current flowing through the fan motor is substantially lowered at low temperatures, and the overcurrent detection level at low temperatures is reduced. , it is possible to prevent unnecessary cooling at low temperatures, and it is possible to achieve the effects of power saving and noise suppression.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional control device. 1...Position detection circuit 2...Overcurrent detection circuit 3...Driver circuit

Claims (3)

[Claims] (1) A cooling system equipped with an overcurrent detection circuit that compares the detected value of the current flowing through the fan motor with a reference value, and limits the drive of the fan motor if the detected value exceeds the reference value and an overcurrent is detected. 1. A control device for a cooling fan, characterized in that the control device for a cooling fan is provided with a reference value changing means for substantially lowering the reference value to lower an overcurrent detection level when the temperature decreases. (2) The cooling fan control device according to claim 1, wherein the overcurrent detection circuit stops driving the fan motor when the detected current value exceeds a reference value. (3) The cooling fan control device according to claim 1 or 2, wherein the reference value changing means is a thermistor.