JP2605979B2 - Fan rotation monitoring circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan rotation monitoring circuit for cooling an electronic device. Recent electronic devices require effective heat radiation to accommodate many functions in a small space due to miniaturization, and fans are used, but fans are short-lived among electronic devices due to mechanical wear. Therefore, effective monitoring is needed.

[0002]

2. Description of the Related Art Conventionally, a rotation monitoring circuit of a cooling fan in an electronic device is a method of counting pulses corresponding to the number of rotations output from the fan by a microprocessor, integrating the pulses and comparing the level with a reference value. There are methods.

FIG. 4 shows a circuit configuration of a conventional fan rotation monitoring circuit for monitoring a plurality of fans, and FIG. 5 shows a flowchart of a rotation monitoring program. In FIG.
12 is a cooling fan provided in the apparatus, 21 is a rotation sensor attached to each fan, P is an output signal of the rotation sensor, 51 is a switching circuit for switching the output signal, and 52 is an output of the rotation sensor. K is a switching signal for the microprocessor to switch the switching circuit 51, 53 is a rotation monitoring program for controlling the microprocessor, S is a rotation reference value to be compared with the fan rotation counting result, and cooling is sufficient. It is a value set within the range to be performed. R is a fan alarm output by the microprocessor.

The operation of the circuit will be described with reference to FIG. When the microprocessor starts operation, in step 71, a switching signal K for selecting the rotation speed pulse P of the first fan 11 is sent to the switching circuit 51, and in step 72, the first fan 11 which is the output of the switching circuit 51 is output. Is counted for a predetermined period of time, and the counting result is compared with a reference value S of the fan rotation speed in step 73. If the counting result is smaller than the reference value S in step 74, the process proceeds to step 75, where the fan Judge that it became abnormal,
Issue a fan alarm R.

On the other hand, if the counting result is larger than the reference value S in step 74, it is determined that the fan is normal.
In order to check the rotation of the next fan, a switching signal K for selecting the output of the rotation sensor of the next fan is sent to the switching circuit 51 to switch the output of the rotation sensor. And step 72
Return to and check the rotation speed of the next fan. This loop continues while the power is on. As described above, conventionally, rotation monitoring by a microprocessor has been performed.

[0006] However, the method using a microprocessor has a problem that the circuit becomes expensive and it is necessary to create a program, and the method using an integration circuit has a problem that the constant calculation of an analog circuit becomes complicated. There was a point.

[0007]

As described above, there has been a problem that monitoring the rotation of the cooling fan of the electronic apparatus is costly or complicated in design.

In view of the foregoing, the present invention provides a means for efficiently and inexpensively monitoring the rotational speed of a cooling fan of an electronic device by configuring the monitor with a very simple circuit. With the goal.

[0009]

The above-mentioned object is achieved by a fan rotation monitoring circuit constructed as follows.
FIG. 1 is a diagram illustrating the principle of the present invention.

An electronic device having a rotation speed sensor 31 for outputting a rotation speed pulse corresponding to the rotation speed of a cooling fan ,
Number of rotations that generates a rotation number monitoring pulse that serves as a reference for the number of rotations
A monitoring pulse generator 32 and two bistable circuits are provided, and the first bistable circuit 33 controls the monitoring state of the rotation speed monitoring pulse.
Set at the rising edge of the times <br/> rotation speed pulses (state when the rotational speed monitoring pulse "H"), the rotational speed monitoring path when shown
When showing a pulse monitoring state ends (the rotational speed monitoring pulse falling
Configured to reset the Chi at edge), a second bistable circuit 34, the rotational speed monitoring pulses indicates the monitoring status termination
At the time (at the fall of the rotation speed monitoring pulse) , if the first bistable circuit 33 is not set, it is reset.
Configure.

[0011]

According to the above configuration, the rotation speed monitoring pulse is monitored.
Indicates the status (when the rotation speed monitoring pulse is "H"
If the rise of the rotation speed pulse does not come within
In this case, the first bistable circuit 33 is not set,
When monitoring by resetting the bistable circuit 34 of
It detects that the rotation speed of the fan has dropped in
Send an alarm .

[0012]

FIG. 2 shows the configuration of an embodiment of the present invention. In the figure, reference numeral 31 denotes a rotation speed sensor provided at each required portion of a fan (not shown) of an electronic device, and 32 denotes a rotation speed monitoring pulse serving as a reference of the rotation speed of the fan. rotational speed monitoring pulse generator for generating, 33 the rotational speed superintendent
When the visual pulse is in the “H” state (the rotation speed monitoring pulse is
State), it is set at the rising edge of the rotation speed pulse and reset at the falling edge of the rotation speed monitoring pulse .
Cormorants configuration the first monitoring circuit consisting of bistable circuit 34 before
At the falling edge of the rotation speed monitoring pulse ( rotation speed monitoring pulse
Is configured to reset when the monitoring circuit 33 is not set, and to determine that the monitoring circuit 33 has become abnormal within the monitoring time by being reset. A determination circuit 35 for inverting the rotation number monitoring pulse; and a latch circuit 36 for holding the output of the determination circuit 34. This circuit is composed of a normal TTL circuit.

The operation of the circuit of FIG. 2 will be described with reference to the time chart of FIG. (A) in the figure shows the normal operation. The fan rotation number pulse P (hereinafter, abbreviated as pulse P) is supplied to the clock of the monitoring circuit 33. Since the D input of the monitoring circuit 33 always contains "1", the rotation number monitoring pulse is generated.
In the state of “H”, when the clock is input, the monitor circuit 33 is set at the rising edge (at the time of “a”). The rotation speed monitoring pulse Q (hereinafter abbreviated as pulse Q) is the fan rotation speed
The period is selected to be equal to or less than half of the pulse P. Pulse Q
Since is inverted by the inverting circuit 35 and supplied to the clear terminal of the monitoring circuit 33, the monitoring circuit 33 is reset at the falling edge (at the point b) and reset while the pulse Q falls. When the pulse Q rises, the monitoring circuit 33 is set again at the time when the pulse P rises (time c). Then, it is reset when the next pulse Q falls (time point d). The monitoring circuit 33 is set at a constant interval when the pulse P always rises during the pulse Q, that is, when the frequency of the pulse P is twice or more the frequency of the pulse Q. This means that the rotation speed of the fan is higher than the reference.

The judgment circuit 34 outputs the output of the rotation speed monitoring pulse generator.
Since the force pulse Q is a clock, the falling of the pulse Q
Monitoring circuit 33 when the lower is Tsu is set if set. Therefore, it is set at the time point b, and thereafter, the monitoring circuit 33
If the pulse Q falls when the signal is not set, it is reset.
Never reset . Since the judgment circuit 34 is not reset, the latch circuit 36 does not invert. Therefore, the fan alarm R keeps the level of "1". (The H level in the figure means "1").

FIG. 1B shows a situation when the number of revolutions has decreased. When the rotation speed of the fan decreases, the pulse P rises during the pulse Q, the monitoring circuit 33 is set (time e), and the monitoring circuit 33 is reset at the fall of the pulse Q (time f). There is a case where the pulse P does not rise between the pulses Q, and thus the falling of the pulse Q occurs without the monitoring circuit 33 being set (time point g). At this time, the judging circuit 34 is reset, the latch circuit 36 is inverted, and the fan alarm R becomes "0" to notify the alarm. The alarm is notified to the CPU, and the 1CPU displays a message indicating that a decrease in the number of rotations of the fan has been detected, and performs a system stop process. After the maintenance is performed by the fan, the processing is restarted.

By providing a monitoring function with only one bistable circuit in this way, a monitoring circuit can be easily and economically and advantageously configured, and a small-scale and low-cost device can be realized.

[0017]

As is apparent from the above description, according to the present invention, the monitoring of the rotational speed of the cooling fan of the electronic device is realized by a very simple circuit, thereby realizing the inexpensive and efficient rotational speed monitor. Has a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a time chart of the embodiment of the present invention.

FIG. 4 shows a configuration of a conventional fan rotation monitoring circuit.

FIG. 5 is a flowchart of a rotation monitoring program.

[Explanation of symbols]

Reference Signs List 11 first fan 12 second fan 21 first rotation speed sensor 31 rotation speed sensor 32 rotation speed monitoring pulse generator 33 first bistable circuit or monitoring circuit 34 second bistable circuit or determination circuit 51 switching Circuit 52 Microprocessor 53 Rotation monitoring program 71-76 Operation steps

Claims (1)

(57) [Claims] A rotation speed pulse corresponding to a rotation speed of a fan is generated.
An electronic apparatus having a rotational speed sensor which outputs, times for generating a rotational speed monitoring pulse as a reference for the rotational speed
A rotation number monitoring pulse generator, and the rotation number when the rotation number monitoring pulse indicates a monitoring state;
Set at the rising edge of the pulse, the rotation speed monitoring pulse
Bistable reset when the signal indicates end of monitoring state
Circuit, and when the rotation speed monitoring pulse indicates the end of the monitoring state,
If one bistable circuit is not set, fan abnormal
Fan monitoring circuitry, characterized in that it comprises a second bistable circuit which outputs a signal indicating the state, a.