JPH04355377A - Short time pulse signal discriminating circuit - Google Patents

Abstract

PURPOSE:To obtain the title circuit continuing short time pulse signal of low voltage inputted to the input terminal of a microcomputer for a long time sufficient to be capable of detecting said signal by the microcomputer to allow the microcomputer to properly deal with the various abnormal states generated in device to be controlled. CONSTITUTION:The NAND gate 19 of a low voltage detecting circuit 12 detecting the abnormal low voltage of an air conditioner to output the short time pulse signal of low voltage V1 and the first signal wire 16a connected to the first input terminal 11a of a microcomputer 11 are connected by a diode 1 arranged in the forward direction toward the NAND gate 19. The first signal wire 16a of the diode is earthed through a condenser 2.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a short-time pulse signal discrimination circuit that allows a microcomputer (hereinafter abbreviated as "microcomputer") to discriminate short-time pulse signals output from an abnormality detection circuit of a controlled device. .

0002

2. Description of the Related Art Hitherto, as this type of discrimination circuit, one shown in FIG. 4, for example, has been known. This discrimination circuit includes a microcomputer 11, a low voltage detection circuit 12 that detects an abnormally low voltage of an air conditioner (not shown) controlled by the microcomputer 11, and a low voltage detection circuit 12 that detects overcurrent of the air conditioner and abnormal temperature rise of the fins. It is provided between the overcurrent detection circuit 13 and the overcurrent detection circuit 13 for detection. That is, the discrimination circuit connects the resistor 15 connected to the constant voltage power supply 14 to the first input terminal 11a of the microcomputer 11 via the first signal line 16a having the diode 17a and the resistor 18a, and the second signal having the diode 17b and the resistor 18b. The lines 16b are connected to the second input terminals 11b of the microcomputer 11, and the first signal line 16a and the second signal line 16b between the diode and the resistor are respectively connected to the NAND gate 19 which is the output terminal of the low voltage detection circuit 12. , are connected to the overcurrent detection circuit 13. In addition, the resistor 15 and diodes 17a, 17
A latch circuit 20 is provided which receives a signal from between 1 and 2b and outputs an interrupt signal to the interrupt input terminal 11c of the microcomputer 11.

When the low voltage detection circuit 12 or the overcurrent detection circuit 13 detects an abnormality, a pulse signal of approximately 0V is output to the first signal line 16a or the second signal line 16b, which causes the diode 17a or 17b to The latch circuit 20 detects the current flowing to the detection circuit side via the latch circuit 20, and outputs an interrupt signal to the interrupt input terminal 11c of the microcomputer. Upon receiving the interrupt signal, the microcomputer 11 temporarily suspends the program being executed, determines which of the first and second input terminals 11a and 11b the low voltage (0V) short-time pulse signal is input to, and If the former, low voltage abnormality processing is executed, and if the latter, overcurrent or fin temperature rise abnormality processing is executed.

0004

However, in the conventional discrimination circuit described above, the pulse signals from the detection circuits 12 and 13 are directly input to the input terminals 11a and 11b of the microcomputer, and the microcomputer 11 is Since a pulse signal of a certain period of time (e.g. 200 μsec) is required to determine the voltage, if a low voltage input signal of an extremely short period of time occurs, it cannot be determined and it is difficult to determine which input terminal has the low voltage. cannot judge. The program then assumes that an overcurrent abnormality has occurred and stops the compressor of the air conditioner. Therefore, there is a drawback that appropriate processing cannot be performed in the event of a low voltage abnormality, which may lead to breakdowns or accidents.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to allow a microcomputer to detect various abnormalities occurring in controlled equipment by sustaining a low-voltage, short-time pulse signal from an abnormality detection circuit for a long enough time that the microcomputer can detect it. It is an object of the present invention to provide a short-time pulse signal judgment circuit that allows appropriate handling.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the short-time pulse signal discriminating circuit of the present invention, as illustrated in FIG. The voltage signal line 16a is connected to an abnormality detection circuit 12 that detects the voltage and outputs a short-time pulse signal of low voltage Vl to the voltage signal line 16a connected to the input terminal 11a of the microcomputer 11. and the output terminal 19 of the abnormality detection circuit 12 are connected by a diode 1 placed in the forward direction toward the output terminal 19, and the voltage signal line 16a side of the diode 1 is grounded via a capacitor 2. shall be. Further, the abnormality detection circuit 12 is configured to be a low voltage detection circuit 12 that detects an abnormally low voltage of the device, and the discrimination circuit is configured to detect an overcurrent or an abnormal temperature rise of the device and detect an abnormally low voltage of the device. 11
The overcurrent detection circuit 1 outputs a short-time pulse signal of low voltage Vl to the voltage signal line 16b connected to the other input terminal 11b of the overcurrent detection circuit 1.
3, receiving the short-time pulse signal of the low voltage Vl from the low voltage detection circuit 12 and the overcurrent detection circuit 13,
A latch circuit 20 may be provided to output an interrupt signal to the interrupt input terminal 11c of the microcomputer 11.

[0007]

[Operation] Now, when the abnormality detection circuit 12 detects an abnormal state of the equipment controlled by the microcomputer 11, a low voltage Vl is applied to the voltage signal line 16a connected to the input terminal 11a of the microcomputer 11.
outputs a short-time pulse signal. Then, a current instantaneously flows from the power supply 14 to the abnormality detection circuit 12 via the voltage signal line 16a and the diode 1, and as a result, the electric charge stored in the capacitor 2 on the voltage signal line 16a side of the diode 1 is completely removed. Discharged. Next, when the above equipment returns to normal, the output terminal 1 of the abnormality detection circuit 12 on the other side of the diode 1
9 has a higher voltage than the one side connected to the power source 14,
The voltage of the power supply 14 is applied to the voltage signal line 16a. However, since the voltage signal line 16a is grounded via the uncharged capacitor 2, the input terminal 11 of the microcomputer 11
a does not immediately become the high voltage Vh, but gradually approaches the high voltage Vh while the capacitor 2 is being charged. In other words, the upper limit voltage (
For example, it takes a predetermined time (for example, 270 V) to rise above 1 V.
microcontroller 11 has finished determining whether any of the input terminals has become low voltage (L level).
Execute appropriate processing for this abnormality.

The operation of the short-time pulse signal discriminating circuit in which the abnormality detecting circuit 12 is replaced by a low voltage detecting circuit 12 and an overcurrent detecting circuit 13 and a latch circuit 20 are added is as follows. If an abnormally low voltage occurs in the device, the low voltage detection circuit 12 detects this, and if an overcurrent or abnormal temperature rise occurs in the device, an overcurrent is detected on the voltage signal line 16a connected to the first input terminal 11a. The detection circuit 13 detects this and outputs short-time pulse signals of the low voltage Vl to the voltage signal lines 16b connected to the other input terminals 11b, respectively. When both short-time pulse signals are output, for the microcomputer 11, one input terminal 1
1a has a low voltage Vl for the same reason as mentioned above, and the other input terminal 11b has no diode or capacitor, so it remains at a high voltage Vh. On the other hand, when the latch circuit 20 receives any of the above short-time pulse signals, it outputs an interrupt signal to the interrupt input terminal 11c of the microcomputer 11. Therefore, the microcomputer 11 interrupts the program being executed in response to the interrupt signal, and if one input terminal 11a is low voltage (L level), it will be connected to this input terminal 11a, and both input terminals 11a and 11b will be connected to high voltage (H level). level), the other input terminals 11b each have a low voltage V
It is determined that a short-time pulse signal of 1 has been input. Therefore, the microcomputer 11 can reliably recognize whether an abnormality has occurred in the device, such as low voltage or overcurrent (abnormal temperature rise), and executes appropriate processing for each abnormality.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to illustrated embodiments. FIG. 1 is a circuit diagram showing an example of a short-time pulse signal discrimination circuit of the present invention. This discrimination circuit has a diode 1 provided in the forward direction toward the NAND gate 19 on the third signal line 16c connecting the first signal line 16a and the NAND gate 19 in the conventional circuit described in FIG. The third signal line 16c on the side of the first signal line 16a is grounded via a capacitor 2, and the same members as in FIG. 4 are given the same numbers. As the diode 1, a Schottky diode with a forward voltage drop smaller than that of a normal diode is used in order to maintain the first input terminal 11a of the microcomputer 11 at a low voltage when conductive.

FIG. 2 shows a resistor 18a, the diode 1,
It shows how the voltage at the first input terminal 11a of the microcomputer connected to the low voltage detection circuit 12 via the NAND gate 19 and the capacitor 2 changes due to the operation of the low voltage detection circuit 12. In other words, if the air conditioner is normal,
Since the NAND gate 19, which is the output terminal of the low voltage detection circuit 12, always outputs a higher voltage than the other side of the diode 1, the voltage of the constant voltage power supply 14 is applied to the first input terminal 11a, as shown in the initial stage of FIG. and becomes high voltage Vh. Also, the capacitor 2 is charged. Next, when an abnormal low voltage occurs in the air conditioner, the low voltage detection circuit 1 detects this.
2 outputs a low voltage short-time pulse signal via a NAND gate 19. Then, a current instantaneously flows from the constant voltage power supply 14 to the low voltage detection circuit 12 via the first signal line 16a, the third signal line 16c, and the diode 1, and the first input terminal 1
The voltage 1a suddenly decreases to a low voltage Vl as shown in FIG. 2, and the charge stored in the capacitor 2 is also completely discharged. In addition,
The signal output from the NAND gate 19 is a relatively long pulse signal with a duration of 600 μsec in the example of FIG.
This shows a case where there is no problem in determining the microcomputer 11.
If this duration is extremely short, such as 200 μsec, in the conventional example, it will interfere with the judgment of the microcomputer 11. However, in this embodiment, such a problem does not occur because the following measures are taken. In the example of Figure 2,
After 600 μsec, at time t1, when the abnormally low voltage of the air conditioner is resolved, the NAND gate 19 outputs high voltage again.

Therefore, the voltage of the constant voltage power supply 14 is again applied to the first signal line 16a, but since the first signal line 16a is grounded via the capacitor 2 of the third signal line 16c, the microcomputer 11 The first input terminal 11a does not immediately become the high voltage Vh. That is, as shown in FIG. 2, since the capacitor 2 is charged, it gradually increases in a logarithmic curve toward Vh, and from the end time t1 of the pulse signal to 27
Even at time t2 after 0 μsec has elapsed, the voltage is 1V, which is determined to be a low voltage (L level). In addition, the microcomputer 11
Upon receiving an interrupt signal from the latch circuit 20 at time t0 when the voltage falls, the first and second input terminals 11a, 11
b is the low voltage for a certain period of time (from t0 to 20
However, even if the time during which the pulse signal is output (the time from t0 to t1) is extremely short, the low voltage (
The time it takes (from t0 to t
2) is 270 μsec or more, and the microcomputer 11 can always discriminate and recognize this low voltage.

[0012] The short-time pulse signal discriminating circuit having the above configuration has the following features:
It works like this: If an abnormal low voltage occurs in the air conditioner, the low voltage detection circuit 12 detects this and connects the first signal line 16 from the NAND gate 19 to the first input terminal 11a.
A low-voltage short-time pulse signal is output to a. Additionally, if an overcurrent or abnormal temperature rise occurs in the air conditioner, the overcurrent detection circuit 13 detects this and sends a low voltage short-time pulse signal to the second signal line 16b connected to the second input terminal 11b. Output. When these short-time pulse signals are output, for the microcomputer 11, the first input terminal 11a becomes a low voltage (L level) for at least 270 μsec or more from time t0, as described in FIG. 11b has no diode or capacitor, so it takes 200 μs from time t1.
The voltage becomes high again (H level) within c. On the other hand, the latch circuit 20 outputs an interrupt signal to the interrupt input terminal 11c of the microcomputer 11 when it receives one of the above-mentioned short-time pulse signals from the signal lines 16a and 16b.

When the microcomputer 11 receives the above-mentioned interrupt signal in step S1 of FIG. 3, it interrupts the program being executed, and
Move to the abnormality processing subroutine. Then, 200 μsec after receiving the interrupt signal, it is determined in step S2 whether or not the first input terminal 11a is at the low voltage Vl, and if yes, a low voltage abnormality processing program is executed in step S3.
If not, there is an overcurrent or an abnormal rise in fin temperature, so the process advances to step S4. Then, in step S4, it is determined whether or not the temperature of the fin has increased abnormally based on a detection signal from a fin temperature sensor (not shown). If yes, step S4 is performed.
In step S5, a program for processing a fin temperature rise abnormality is executed, and if not, a program for processing an overcurrent abnormality is executed in step S6. In this way, when the execution of any one of the abnormality processing programs is completed, the process returns to the main routine.

In this way, unlike the conventional example, the microcomputer 11 can reliably recognize which abnormality has occurred in the air conditioner, such as low voltage, overcurrent, or fin temperature rise, and can take appropriate measures even for low voltage abnormalities. This eliminates air conditioner failures and accidents caused by over-processing. In the above embodiment, an overcurrent detection circuit 13 is added to a low voltage detection circuit 12 that includes a diode 1 and a capacitor 2, and a latch circuit 20 that receives short-time pulse signals from these detection circuits causes the microcomputer 11 to perform an abnormality processing routine. Since the interrupt signal for starting the control is output, it is possible to appropriately deal with a plurality of abnormal states of the controlled device with a simple circuit configuration. Note that the latch circuit in the above embodiment is omitted,
It is also possible to provide three or more abnormality detection circuits each equipped with a diode and a capacitor, and cause the microcomputer to execute an abnormality processing routine corresponding to the detection circuit connected to the low voltage input terminal.

[0015]

Effects of the Invention As is clear from the above description, the short-time pulse signal discrimination circuit of the present invention has an output of an abnormality detection circuit that detects an abnormal state of a controlled device and outputs a low-voltage short-time pulse signal. The terminal and the voltage signal line connected to the input terminal of the microcontroller are connected by a diode placed in the forward direction toward the output terminal, and the voltage signal line side of this diode is grounded via a capacitor. The low-voltage, short-time pulse signal input to the input terminal can be sustained for a long time enough for the microcontroller to detect it, and with its simple configuration, the microcontroller can be used to respond appropriately to various abnormal conditions that occur in controlled equipment. You can make them deal with it.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a short-time pulse signal discrimination circuit of the present invention.

FIG. 2 is a diagram showing changes in voltage at a first input terminal of the microcomputer in FIG. 1;

FIG. 3 is a flowchart showing an abnormality processing subroutine of the microcomputer.

FIG. 4 is a circuit diagram showing a conventional short-time pulse discrimination circuit.

[Explanation of symbols]

1...Diode, 2...Capacitor, 11...Microcomputer, 1
1a...first input terminal, 11b...second input terminal, 11c...
Interrupt input terminal, 12... Low voltage detection circuit, 13... Overcurrent detection circuit, 14... Constant voltage power supply, 16a... First signal line, 16
b...Second signal line, 19...NAND gate.

Claims (2)

[Claims] Claim 1: The microcomputer (11) detects an abnormal state of a microcomputer (11) and a device controlled by the microcomputer (11), and
A short-time pulse signal discrimination circuit provided between an abnormality detection circuit (12) that outputs a short-time pulse signal of low voltage (Vl) to a voltage signal line (16a) connected to an input terminal (11a) of the The voltage signal line (16a) and the output terminal (19) of the abnormality detection circuit (12) are connected to this output terminal (19).
), and the voltage signal line (16) of this diode (1).
A short-time pulse signal discrimination circuit characterized in that the a) side is grounded via a capacitor (2). 2. The abnormality detection circuit (12) is a low voltage detection circuit (12) that detects abnormal low voltage of the equipment, and also detects overcurrent or abnormal temperature rise of the equipment. The microcomputer (11) is equipped with an overcurrent detection circuit (13) that outputs a short-time pulse signal of low voltage (Vl) to a voltage signal line (16b) connected to another input terminal (11b) of the microcomputer (11). In response to the low voltage (Vl) short-time pulse signal from the voltage detection circuit (12) and overcurrent detection circuit (13), the microcomputer (11)
2. The short-time pulse signal discriminating circuit according to claim 1, further comprising a latch circuit (20) for outputting an interrupt signal to the interrupt input terminal (11c) of the circuit.