JP3394503B2 - Blower rotation speed drop detection 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 blower rotation speed decrease detection circuit, and more particularly, to a blower rotation speed decrease detection circuit using a monostable multivibrator.
The present invention relates to a blower rotation speed decrease detection circuit that can prevent erroneous detection of rotation speed decrease due to temperature fluctuations by using an output signal of a monostable multivibrator as a rotation speed detection clock.

[0002]

2. Description of the Related Art Conventionally, a blower rotation speed lowering detection circuit 31
In FIG. 7 showing a conventional example, a power source is input from a power source terminal 3 and a blower 2 that outputs a digital signal 4 corresponding to the number of revolutions and a digital signal 4 are input to the A terminal of a monostable multivibrator 5, The power source terminal 6 and one end of the resistor 7 are connected to the T2 terminal of the stable multivibrator 5, the other end of the resistor 7 and one end of the capacitor 8 are connected to the T1 terminal of the stable multivibrator 5, and the other end of the capacitor 8 is connected. Connected to GND, B of monostable multivibrator 5
By connecting the CD terminal to the power supply terminal 9, the monostable multivibrator 5 that outputs the digital signal 10 in synchronization with the digital signal 4 and the output terminal 20 that inputs the digital signal 10 are connected directly to the digital signal. The number of rotations was recognized by the signal 10.

FIG. 7 shows a conventional blower rotation speed decrease detection circuit.
Fig. 8 shows the time chart for normal rotation at room temperature.
The operation will be described with reference to the time chart of the normal rotation at low temperature in FIG.

First, normal rotation at normal temperature will be described with reference to FIG.

For example, by inputting power from the power supply terminal 3, the blower 2 rotates at 50 rps (3000 rpm) and outputs a digital signal 4 (generates two pulses in one rotation) with a duty of 50% at a cycle of 10 msec. Further, if the pulse width of the output pulse output from the monostable multivibrator 5 is taken as the latch time, the latch time is determined by the product of the resistor 7 and the capacitor 8, and here it is 11 ms.
ec.

The monostable multivibrator 5 inputs the digital signal 4 to the A terminal, the T2 terminal to one end of the power supply terminal 6 and the resistor 7, the T1 terminal to the other end of the resistor 7 and one end of the capacitor 8. The other end of the condenser 8 to GND,
By connecting the B and CD terminals to the power supply terminal 9, the digital signal 10 [digital signal 4
Rises in synchronism with the rising edge t1 and tries to fall after the latch time (t5: 11 msec from t1), but is latched t4 again in the remaining 1 msec, so always hold "Hi"] , The output terminal 20 for inputting the "Hi" digital signal 10 can detect that the motor is rotating normally.

Next, normal rotation at low temperature will be described with reference to FIG.

For example, by inputting power from the power supply terminal 3, the blower 2 rotates at 50 rps, and 10 mse.
The digital signal 4 having a duty of 50% is output in the cycle of c. However, it is assumed that the latch time is shortened from 11 msec to 6 msec by the resistor 7 having a temperature coefficient, the capacitor 8, and the monostable multivibrator 5.

The monostable multivibrator 5 rises in synchronization with the digital signal 4 [in synchronization with the rising edge t1 of the digital signal 4 and falls after the latch time (t3: t1 to 6 msec) elapses. The signal rises in synchronization with the rising edge t4 of the signal 4, and the latch time (t7: t4 to 6 mse
c)), and outputs "Hi" to "L".
Output terminal 2 for inputting digital signal 10 changed to "o"
With 0, it is erroneously detected that the number of revolutions has decreased.

[0010]

Therefore, in the above prior art, although the latch time output from the monostable multivibrator 5 varies depending on the temperature characteristic and the rotation speed does not decrease, Occasionally, the lowering of the rotation speed was erroneously detected.

In view of the above-mentioned conventional circumstances, the present invention has been made to solve the above-mentioned problems inherent in the prior art. Therefore, an object of the present invention is to provide a monostable multivibrator for reducing the rotational speed of a blower. In the circuit to detect using,
It is an object of the present invention to provide a novel blower rotation speed decrease detection circuit which can prevent erroneous detection of rotation speed decrease due to temperature fluctuation by using an output signal of a monostable multivibrator as a rotation speed detection clock.

[0012]

In order to achieve the above object, in the blower rotation speed lowering detection circuit according to the present invention, a digital signal corresponding to the rotation speed of the blower is input to the first input terminal. The first time constant circuit is connected between the output pulse width setting terminal and the second output pulse width setting terminal, the second and third input terminals are connected to the first power supply, and the digital signal is output from the non-inverting output terminal. A first monostable multivibrator that generates a first digital signal synchronized with the signal; a first input terminal is grounded; and a second input terminal receives a digital signal corresponding to the rotation speed of the blower, And a second time constant circuit is connected between the second output pulse width setting terminals, the third input terminal is connected to the second power supply, and the second digital signal synchronized with the digital signal is generated from the inverting output terminal. Second monostable circle A vibrator and the first digital signal output from the first monostable multivibrator are input to an input terminal, and the second digital signal output from the second monostable multivibrator is input to a clock terminal. And a rotation speed detection circuit for generating a digital signal for detecting the rotation speed of the blower.

A series circuit composed of a delay circuit and an inverting circuit is inserted between the output of the blower and the second input terminal of the second monostable multivibrator.

The first time constant circuit includes a first resistor and a first resistor.
The second time constant circuit is composed of a second resistor and a second capacitor.

The rotation speed detection circuit is composed of a flip-flop.

The flip-flop is, for example, a D-type flip-flop.

[0017]

In FIG. 1, the pulse width (hereinafter referred to as the latch time) of each output pulse output from the two monostable multivibrators varies depending on the ambient temperature, but the output of the monostable multivibrator connected in parallel is changed. By using the signal as the rotation speed detection clock, the fluctuation of the latch time of the monostable multivibrator can be temperature-compensated. Therefore, the blower rotation speed decrease detection circuit can prevent erroneous detection of rotation speed decrease due to temperature fluctuation.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the drawings for each preferred embodiment thereof.

[First Embodiment] FIG. 1 is a circuit block diagram showing a first embodiment of the present invention.

[Structure of First Embodiment] Referring to FIG. 1, a blower rotation speed decrease detection circuit 1 according to the present invention receives power from a power supply terminal 3 and outputs a digital signal 4 corresponding to the rotation speed. And the digital signal 4 are input to the A terminal (input terminal) of the monostable multivibrator 5, and the T2 terminal (latch time setting terminal) of the monostable multivibrator 5 includes a power supply terminal 6 and a resistor 7. One end of the monostable multivibrator 5 is connected to the T1 terminal (latch time setting terminal) of the other end of the resistor 7 and one end of the capacitor 8,
The other end of the capacitor 8 is connected to GND, and the B and CD terminals (input terminals) of the monostable multivibrator 5 are connected to the power supply terminal 9 to output the digital signal 10 in synchronization with the digital signal 4. Multivibrator 5
And the digital signal 4 is input to the B terminal (input terminal) of the monostable multivibrator 11, and the T2 terminal (latch time setting terminal) of the monostable multivibrator 11 is connected to the power supply terminal 12 and one end of the resistor 13. , The other end of the resistor 13 and one end of the capacitor 14 are connected to the T1 terminal (latch time setting terminal) of the monostable multivibrator 11, and the other end of the capacitor 14 is connected to GND, and the A terminal of the monostable multivibrator 11 ( Input terminal) is GND
To the digital signal 4 by connecting the CD terminal (input terminal) of the monostable multivibrator 11 to the power supply terminal 15.
The monostable multivibrator 11 that outputs the digital signal 16 in synchronization with the digital signal 16 is input to the D terminal of the flip-flop 17, and the digital signal 16 is input to the CLK terminal of the flip-flop 17, A flip-flop 1 that outputs a digital signal 19 by connecting the R and PR terminals to the power supply terminal 18.
7 and an output terminal 20 for inputting the digital signal 19.

The T of the monostable multivibrator 5 is
A resistor 7 and a capacitor 8 connected to terminals 1 and T2, and a resistor 13 and a capacitor 14 connected to terminals T1 and T2 of the monostable multivibrator 11 respectively form a time constant circuit.

[Operation of the First Embodiment] Hereinafter, a blower rotation speed decrease detection circuit is shown in FIG. 1, a time chart during normal rotation at room temperature is shown in FIG. 2, and a time chart during low speed rotation at room temperature is shown in FIG. The operation will be described with reference to FIG. 4 showing a time chart during normal rotation at low temperature and FIG. 5 showing a time chart during low speed rotation at low temperature.

The monostable multivibrator is HD74HC4538 (Hitachi) and the flip-flop is μPD74HC74 (NEC).

First, the normal rotation at room temperature will be described in detail with reference to FIGS.

For example, by inputting power from the power supply terminal 3, the blower 2 rotates at 50 rps (3000 rpm) and outputs a digital signal 4 (2 pulses are generated in one rotation) with a duty of 50% at a cycle of 10 msec. In addition, the latch time output from the monostable multivibrators 5 and 11 is determined by the product of the resistors 7 and 13 and the capacitors 8 and 14, and here is 11 msec, that is, the threshold value for abnormal rotation speed is about 24 rps (about 1400 rpm).

The monostable multivibrator 5 inputs the digital signal 4 to the A terminal, and the T2 terminal has the power terminal 6 on one side.
The other one is to one end of the resistor 7, the T1 terminal is one to the other end of the resistor 7 and the other to one end of the capacitor 8, the capacitor 8
By connecting the other end to GND and the B and CD terminals to the power supply terminal 9, the digital signal 1 is synchronized with the digital signal 4.
0 [rises in synchronization with the rising edge t1 of the digital signal 4 and latches (t5: from t1 to 11 mse
c) After a lapse of time, it tries to fall, but in order to re-latch t4 in the remaining 1 msec, "Hi" is always held] is output.

The monostable multivibrator 11 inputs the digital signal 4 to the B terminal, one of the T2 terminals to the power supply terminal 12 and the other to one end of the resistor 13, and one T1 terminal to the other end of the resistor 13 and the other end. One end of the condenser 14, the other end of the condenser 14 to GND, the A terminal to GND, C
By connecting the D terminal to the power supply terminal 15, the digital signal 16 is synchronized with the digital signal 4 [falls in synchronization with the falling edge t2 of the digital signal 4, and after the latch time (t7: t2 to 11 msec) elapses. , Keeps "Lo" at all times in order to latch t6 again in the remaining 1 msec.

The flip-flop 17 outputs the "Hi" digital signal 10 to the D terminal and the "Lo" digital signal 1
6 is input to the CLK terminal, and the R and PR terminals are the power supply terminal 1
By connecting to 8, the digital signal 19 of “Hi” is output, and the normal rotation can be detected by the output terminal 20 to which the digital signal 19 of “Hi” is input.

Therefore, the blower rotation speed decrease detection circuit 1 is
It can be detected that the rotation speed of the blower 2 is normal.

Next, a low speed rotation at room temperature will be described with reference to FIGS.

For example, power is input from the power supply terminal 3, but the blower 2 is set to 20 rps (1200
The digital signal 4 with a duty of 50% is output at a cycle of 25 msec.

The monostable multivibrator 5 rises in synchronization with the digital signal 4 [in synchronization with the rising edge t8 of the digital signal 4 and falls after the latch time (t9: t8 to 11 msec) elapses. It rises in synchronization with the rising edge t12 of the digital signal 4 and falls after the latch time (t13: 11 msec from t12)].

The monostable multivibrator 11 synchronizes with the digital signal 4 and outputs the digital signal 16 [digital signal 4
Falling edge in synchronization with the falling edge t10, and rising after the lapse of the latch time (t11: 11 msec from t10)] is output.

The flip-flop 17 receives the digital signal 1 at the timing of the rising edge t11 of the digital signal 16.
In order to read the data “Lo” of 0, a low speed rotation can be detected by the output terminal 20 which outputs the “Lo” digital signal 19 and inputs the “Lo” digital signal 19.

Therefore, the blower rotation speed decrease detection circuit 1 is
It can be detected that the rotation speed of the blower 2 has dropped to the threshold value.

On the other hand, the normal rotation at low temperature will be described in detail with reference to FIGS.

For example, by inputting power from the power supply terminal 3, the blower 2 rotates at 50 rps, and also 10 ms.
The digital signal 4 having a duty of 50% is output in a cycle of ec.

Here, each of the resistors 7 and 13 having a positive temperature coefficient (temperature-resistance value) and a positive temperature coefficient (temperature-resistance value).
Capacitors 8 and 14 each having a capacitance) and monostable multivibrators 5 and 11 each having a positive temperature coefficient (temperature-latch time) have a latch time of 11 ms.
It is shortened from ec to 6 msec, that is, the threshold value of the rotation speed abnormality changes to about 31 rps (about 1800 rps).

The monostable multivibrator 5 rises in synchronization with the digital signal 4 [in synchronization with the rising edge t1 of the digital signal 4 and falls after the latch time (t3: 6 msec from t1) elapses]. It rises in synchronization with the rising edge t4 of the digital signal 4, and the latch time (t7: t4 to 6 mse
c) It will fall after a lapse of time] is output.

The monostable multivibrator 11 synchronizes with the digital signal 4 and outputs the digital signal 16 [digital signal 4
Falling edge in synchronization with the falling edge t2, and rises after the lapse of the latch time (t5: 6 msec from t2)] is output.

The flip-flop 17 receives the digital signal 10 at the timing of rising t5 of the digital signal 16.
The normal rotation can be detected by the output terminal 20 that outputs the "Hi" digital signal 19 and inputs the "Hi" digital signal 19 to read the data "Hi".

Therefore, even if the cycle temperature changes, the blower rotation speed decrease detection circuit 1 can detect that the rotation speed of the blower 2 is a normal value, so that it is possible to avoid erroneous detection of a decrease in rotation speed. .

Next, a low speed rotation at a low temperature will be described with reference to FIGS.

For example, power is input from the power supply terminal 3, but the blower 2 is set to 20 rps (1200
The digital signal 4 with a duty of 50% is output at a cycle of 25 msec.

Here, each of the resistors 7 and 13 having a positive temperature coefficient (temperature-resistance value) and a positive temperature coefficient (temperature-resistance value).
Capacitors 8 and 14 each having a capacitance) and monostable multivibrators 5 and 11 each having a positive temperature coefficient (temperature-latch time) have a latch time of 11 ms.
It is assumed that the time is shortened from ec to 6 msec.

The monostable multivibrator 5 rises in synchronization with the digital signal 4 [in synchronization with the rising edge t8 of the digital signal 4 and falls after the lapse of the latch time (t14: t8 to 6 msec), and again. It rises in synchronization with the rising edge t12 of the digital signal 4 and falls after a lapse of the latch time (t16: 6 msec from t12)].

The monostable multivibrator 11 synchronizes with the digital signal 4 and outputs the digital signal 16 [digital signal 4
Falling edge in synchronization with the falling edge t10 and rising after the lapse of the latch time (t15: 6 msec from t10)] is output.

The flip-flop 17 receives the digital signal 1 at the timing of the rising edge t15 of the digital signal 16.
In order to read the data “Lo” of 0, a low speed rotation can be detected by the output terminal 20 which outputs the “Lo” digital signal 19 and inputs the “Lo” digital signal 19.

Therefore, the blower rotation speed decrease detection circuit 1 is
It can be detected that the number of revolutions of the blower 2 has dropped below the threshold value.

[Second Embodiment] Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 6 is a circuit block diagram showing a second embodiment according to the present invention.

Referring to FIG. 6, the blower rotation speed lowering detection circuit 1 receives the power from the power supply terminal 3 and outputs a digital signal 4 corresponding to the rotation speed to the blower 2 and the digital signal 4 as a monostable multi-wave. Input to the A terminal of the vibrator 5, and the T2 terminal of the monostable multivibrator 5 has one end of the power supply terminal 6 and the resistor 7 connected to the T1 terminal of the monostable multivibrator 5.
The other end of the resistor 7 and one end of the capacitor 8 are connected to the terminals, and the other end of the capacitor 8 is connected to the GND. The B and CD terminals of the monostable multivibrator 5 are connected to the power supply terminal 9
Connection to the monostable multivibrator 5 that outputs the digital signal 10 in synchronization with the digital signal 4, and the delay circuit 21 that inputs the digital signal 4 and outputs the digital signal 22 after a certain period of time has passed, Digital signal 22
And an inverting circuit 23 that outputs a digital signal 24 that is the inverted signal of the digital signal 22, and the digital signal 24 are input to the B terminal of the monostable multivibrator 11, and the power supply terminal is connected to the T2 terminal of the monostable multivibrator 11. 12 and one end of the resistor 13, the T1 terminal of the monostable multivibrator 11 is connected to the other end of the resistor 13 and one end of the capacitor 14, and the other end of the capacitor 14 is connected to GND, respectively, and the A terminal of the monostable multivibrator 11 is connected. Is GND
By connecting the CD terminal of the monostable multivibrator 11 to the power supply terminal 15, the monostable multivibrator 11 that outputs the digital signal 16 in synchronization with the digital signal 24 and the digital signal 10 to the D terminal and the digital signal 1
By inputting 6 to the CLK terminal and connecting the R and PR terminals to the power supply terminal 18, the flip-flop 17 outputs the digital signal 19, and the output terminal 20 inputs the digital signal 19.

That is, the second embodiment is the same as the first embodiment.
In this embodiment, a delay circuit 21 and an inverting circuit 23 are added between the blower 2 and the monostable multivibrator 11.

In the second embodiment, the digital signal 4
Even when the duty of is 50% or less, by setting the delay time of the digital signal 4, the rising edge of the digital signal 22 can be raised at the duty of 50% in the cycle of the digital signal 4. The effect of widening the allowable range of the duty of the digital signal 4 is obtained.

[0055]

The present invention is constructed and operates as described above, and according to the present invention, the following effects can be obtained.

The first effect is that the latch time output from the monostable multivibrator can be temperature-compensated, so that an accurate rotation speed can be detected even if temperature fluctuations occur.

The reason is that by using the output signal of the monostable multivibrator connected in parallel to the output of the blower as the rotation speed detection clock, the latch generated from the rising edge of the digital signal according to the rotation speed. This is because the increase / decrease in time can be compensated by the increase / decrease in the latch time generated from the fall of the digital signal according to the rotation speed.

[Brief description of drawings]

FIG. 1 is a first diagram of a blower rotation speed lowering detection circuit according to the present invention.
FIG. 3 is a block diagram showing the embodiment of FIG.

FIG. 2 is a time chart when the detection circuit shown in FIG. 1 normally rotates at room temperature.

3 is a time chart when the detection circuit shown in FIG. 1 rotates at low speed at room temperature.

FIG. 4 is a time chart when the detection circuit shown in FIG. 1 normally rotates at a low temperature.

5 is a time chart when the detection circuit shown in FIG. 1 rotates at a low speed at a low temperature.

FIG. 6 is a second circuit of the blower rotation speed lowering detection circuit according to the present invention.
FIG. 3 is a block diagram showing the embodiment of FIG.

FIG. 7 is a block diagram of a conventional blower rotation speed decrease detection circuit.

FIG. 8 is a time chart of the detection circuit shown in FIG. 6 during normal rotation at room temperature.

9 is a time chart of the detection circuit shown in FIG. 6 during normal rotation at low temperature.

[Explanation of symbols]

1, 31 ... Blower rotation speed decrease detection circuit 2 ... Blower 3 ... Power supply terminal 4, 16 ... Digital signal 5, 11 ... Monostable multivibrator 6, 9, 12, 15, 18 ... Power supply terminals 7, 13 ... Resistance 8, 14 ... Capacitor 10, 19, 22, 24 ... Digital signal 17 ... Flip flop 20 ... Output terminal 21 ... Delay circuit 23 ... Inversion circuit

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F04D 27/00 G01D 5/245 G01P 3/489

Claims (5)

(57) [Claims] 1. A first time constant circuit between a first output pulse width setting terminal and a second output pulse width setting terminal in which a digital signal corresponding to the number of revolutions of a blower is input to a first input terminal. A first monostable multivibrator for generating a first digital signal synchronized with the digital signal from a non-inverting output terminal, the second and third input terminals being connected to a first power supply, The input terminal is grounded, a digital signal corresponding to the rotation speed of the blower is input to the second input terminal, a second time constant circuit is connected between the first and second output pulse width setting terminals, and a third input is provided. A second monostable multivibrator having a terminal connected to a second power supply and generating a second digital signal synchronized with the digital signal from an inverting output terminal; and the first monostable multivibrator output from the first monostable multivibrator. Digit of 1 The second signal output from the second monostable multivibrator to the second input terminal.
And a rotation speed detection circuit for generating a digital signal for detecting the rotation speed of the blower by inputting the digital signal to the clock terminal. 2. A serial circuit including a delay circuit and an inverting circuit is inserted between the output of the blower and the second input terminal of the second monostable multivibrator. The blower rotation speed lowering detection circuit according to 1. 3. The first time constant circuit includes a first resistor and a first capacitor, and the second time constant circuit includes a second resistor.
3. The blower rotation speed lowering detection circuit according to claim 1, further comprising a resistor and a second capacitor. 4. The blower rotation speed decrease detection circuit according to claim 1, wherein the rotation speed detection circuit is composed of a flip-flop. 5. The blower rotation speed lowering detection circuit according to claim 4, wherein the flip-flop is a D-type flip-flop.