JPH0729757Y2 - Cooling fan function deterioration detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a series connection of two current detection resistors provided in a drive circuit of a cooling fan and a transistor composite connection circuit that operates according to their terminal voltages. In combination, the present invention relates to a circuit that detects a drive current of a cooling fan and outputs a signal indicating a decline in fan function when the drive current is out of a normal current range. This circuit can be widely applied to devices using cooling fans such as power supplies and various electronic devices.

[Prior Art] In many cases, a power supply and various electronic devices incorporating the power supply are equipped with a cooling fan for heat dissipation. The reliability of the cooling fan greatly affects the reliability of the device that uses it for heat dissipation. However, the life of the fan generally depends on the bearing that rotatably supports the impeller, and is said to be about 1/2 to 1/4 that of the power supply. Therefore, if a failure occurs in the cooling fan due to some cause and the desired cooling function is no longer achieved, it is necessary to detect it.

Conventionally, the technology to detect the deterioration of the cooling function by the fan is to detect the temperature of parts and radiators by using a temperature detector such as a thermistor, and to judge the deterioration of the function of the fan by using it. There is a method in which a magnet is attached and a magnetic flux sensor is provided on the housing side so that the fan itself has a rotation detection function.

[Problems to be Solved by the Invention] By the way, the function of detecting the deterioration of the fan function is for notifying the life of the fan and the occurrence of a defect, and can be said to be completely unnecessary during normal operation. Therefore, it is important not only to be accurately detected but also to be inexpensive.

In a configuration in which a temperature detector such as a thermistor is used to detect temperature and determine a functional deterioration, various conditions such as a use environment must be taken into consideration, which has a drawback that the design becomes very complicated. In addition, in the configuration in which the rotation detector is provided in the fan itself, the fan manufacturer designs the detection unit itself, so it is not possible to freely change the normal / abnormal setting level of the fan function, and there is a drawback that the cost will generally be high. .

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a circuit capable of detecting a decrease in fan function with a minimum number of parts and at a minimum cost, and freely selecting an operation level thereof. It is in.

[Means for Solving the Problems] In the present invention, which can achieve the above object, a series connection circuit of first and second current detection resistors provided in a drive circuit of a cooling fan, and a first and second circuit. A series connection circuit of current detection resistors, a transistor composite connection circuit in which both emitters of the first and second transistors are made common and the collector of the first transistor is connected to the base of the second transistor, and one end is connected. Detecting the deterioration of the function of a cooling fan, which comprises two base resistors each connected to the bases of both transistors and the other end of which is coupled to both current detection resistors, and is configured to obtain a detection signal from the collector of the second transistor Circuit.

Here, the cooling fan may be for direct current or for alternating current. In the case of alternating current, a rectifier circuit is inserted in the drive circuit of the cooling fan so that detection can be performed by the transistor, whereby rectification is performed so that a unidirectional current flows through the current detection resistor.

[Operation] When the fan malfunctions and the fan function deteriorates, the current flowing through the fan is out of the normal current range. That is, it increases from the upper limit value of the normal current range or decreases from the lower limit value. The present invention utilizes this mode to detect the functional deterioration due to the drive current of the fan. For example, in a brushless DC fan motor, if there is a short circuit accident such as a diode or transistor, the fan current will increase significantly, and if the winding breaks, the current value will decrease extremely.

In the present invention, when the value is equal to or higher than the lower limit value of the set normal current range, the second
The current that allows it to turn on flows through the base of the transistor, and when it exceeds the upper limit of the set normal current range, the first
A current flows through the base of the transistor to enable it. Therefore, the second transistor is turned on when the value exceeds the lower limit of the normal current range, and the first transistor is turned on when the value exceeds the upper limit, so that the base current of the second transistor is extracted and turned off. In this way, it is possible to detect whether or not the fan current value is within an appropriate range based on the collector voltage of the second transistor, and thereby to detect whether or not the fan is defective.

[Embodiment] FIG. 1 is a circuit diagram showing an embodiment of a cooling fan function deterioration detecting circuit according to the present invention. This example is for a DC fan and uses NPN type transistors. The series connection circuit of the first and second current detection resistors R ₁ and R ₂ is inserted into the drive circuit of the DC fan 10 and combined with the transistor composite connection circuit. The transistor composite connection circuit includes first and second transistors Q ₁ and Q ₂ , both emitters are made common, and the collector of the _first transistor Q ₁ is connected to the base of the second transistor Q _2. .
Connect the emitters of both transistors Q ₁ and Q ₂ to the 0V side, and
One end of the current detection resistor R ₁ of is connected to the base of the first transistor Q ₁ through the base resistor R ₃ , and the second current detection resistor R ₁ is connected.
One end of R ₂ is connected to the second transistor Q ₂ via the base resistor R _4.
Connect to the base of.

When the fan current I flows through the DC fan 10, the fan rotates. As described above, when the DC fan 10 malfunctions, the fan current I greatly increases or decreases. When I · (R ₁ + R ₂ )> 0.7V, a base current that can turn on the second transistor Q ₂ flows. When I · R ₂ > 0.7V, the first transistor
There is a base current that can turn on Q ₁ . For this reason, as shown in FIG. 2, both the first and second transistors Q ₁ and Q ₂ are turned off when the set normal current range is less than the lower limit value I ₁ . When the fan current I reaches the lower limit value I ₁ or more, only the second transistor Q ₂ is turned on. When the upper limit value I ₂ is further exceeded, the first transistor Q ₁ is turned on.
The base current of the transistor Q ₂ of the _second transistor Q ₂ is extracted and the second transistor Q ₂ is turned off. Therefore, the second transistor Q ₂ is turned on only within the set current range (hatched portion), and it is possible to detect whether or not the fan function is deteriorated by its collector voltage.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the AC fan 12 is used as a cooling fan.
In the case of the AC fan 12, the rectifier circuit 14 is inserted in the drive circuit. A diode bridge is used here. The drive current rectified by the rectifier circuit 14 is the first and second drive currents.
The current detection resistances R ₁ and R ₂ are to flow. The connection relation of the transistor composite connection circuit and its base resistance is
It may be similar to the embodiment shown in the figure. By inserting the rectifier circuit 14 in this way, current can be made to flow in the current detection resistors R ₁ and R ₂ from only one direction, and the normal / abnormal detection of the fan current by the transistors Q ₁ and Q ₂ can thereby be detected. It will be possible.

FIG. 4 shows still another embodiment of the present invention. Here, between the base-emitter of the first transistor Q ₁ and the second
Capacitors C ₁ and C ₂ are incorporated between the base and emitter of the transistor Q ₂ of, respectively. In the case of the DC fan 10, a pulsed current actually flows. By inserting capacitors C ₁ and C ₂ , noise due to pulses can be absorbed and malfunction can be prevented. Although a surge current flows when the power is turned on, it is better to set the magnitude relationship of both capacitors to C ₁ > C ₂ in order to prevent the detection signal from being generated at this time. Figure 4
When using the DC fan 10, as shown in FIG.
Similarly, when using an AC fan, it is desirable to insert capacitors C ₁ and C ₂ .

FIG. 5 shows still another embodiment of the present invention. This is an example of using a PNP type transistor. The basic idea is the same as when using the NPN type described above. R _5, R ₆ is a current sensing resistor, R _7, R ₈ is the base resistance, Q _3, Q ₄ is a transistor. From the collector of the transistor Q _4, a fan deterioration detection signal is obtained.

[Advantage of the Invention] Since the present invention is a combination of the current detection resistor, the base resistor and the transistor as described above, it is possible to detect the deterioration (abnormality) of the fan function with the minimum number of parts,
And it can be assembled at low cost. Although the set level indicating whether the fan cooling function is normal or abnormal differs depending on the fan, it can be freely set by selecting the current detection resistor, and normal / abnormal can be detected accurately and quickly.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a cooling fan function deterioration detecting circuit according to the present invention, and FIG. 2 is an explanatory diagram showing its operating range. FIG. 3, FIG. 4 and FIG. 5 are circuit diagrams showing other embodiments of the present invention. 10 ... DC fan, 12 ... AC fan, 14 ... rectifier circuit, R ₁ , R ₂ ...
Current detection resistor, R ₃ , R ₄ ... Base resistor, Q ₁ , Q ₂ ... Transistor.

Claims (1)

[Scope of utility model registration request] 1. A series connection circuit of first and second current detection resistors inserted in a drive circuit of a cooling fan, and both emitters of the first and second transistors are made common, and a collector of the first transistor is made second. Transistor composite connection circuit combined to connect to the base of the transistor, and a first base having one end connected to the base of the first transistor and the other end connected to the connection point of the first and second current detection resistors A second base resistor having one end connected to the base of the second transistor and the other end connected to the other end of the second current detection resistor, and the other end of the first current detection resistor A cooling fan function deterioration detection circuit connected to the emitter of the first transistor and obtaining a detection signal from the collector of the second transistor.