JP2720631B2 - Short-time pulse signal discrimination 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 short-time pulse signal discriminating circuit for discriminating a short-time pulse signal output from an abnormality detecting circuit of a controlled device by a microcomputer (hereinafter abbreviated as "microcomputer"). .

[0002]

2. Description of the Related Art Conventionally, as a discrimination circuit of this kind, for example, a circuit as shown in FIG. 4 is known. The discriminating circuit includes a microcomputer 11, a low voltage detecting circuit 12 for detecting an abnormally low voltage of an air conditioner (not shown) controlled by the microcomputer 11, and an overcurrent of the air conditioner and abnormal temperature rise of the fins. It is provided between the detection circuit 13 and the overcurrent detection circuit 13 for detecting. In other words, the above-described discriminating 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. While being connected to the second input terminal 11b of the microcomputer 11 via the line 16b,
A first signal line 16a and a second signal line 16b between the diode and the resistor are connected to a NAND gate 19, which is an output terminal of the low voltage detection circuit 12, and an overcurrent detection circuit 13, respectively. Further, a signal is received from between the resistor 15 and the diodes 17a and 17b, and an interrupt input terminal 11c of the microcomputer 11 is received.
Is provided with a latch circuit 20 for outputting an interrupt signal.

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

[0004]

However, in the above-mentioned conventional discriminating circuit, the pulse signals from the respective detecting circuits 12 and 13 are directly inputted to the input terminals 11a and 11b of the microcomputer, and the microcomputer 11 operates at a low level. Since a pulse signal for a certain period of time (for example, 200 μsec) is necessary to determine the voltage, if a very short time low voltage input signal is generated, it cannot be determined, and which input terminal has become low voltage Can not judge. Then, the compressor of the air conditioner is stopped assuming that all overcurrent abnormalities have occurred by the program. For this reason, there is a disadvantage in that appropriate processing cannot be performed in the case of a low voltage abnormality, and a failure or an accident may occur.

Accordingly, an object of the present invention is to prevent a microcomputer from detecting various abnormalities caused in a controlled device by maintaining a low-voltage short-time pulse signal from an abnormality detecting circuit for a long time so that the microcomputer can detect the pulse signal. An object of the present invention is to provide a short-time pulse signal determination circuit that can appropriately deal with the short-time pulse signal determination circuit.

[0006]

In order to achieve the above object, a short-time pulse signal discriminating circuit of the present invention comprises a microcomputer 11 and a device controlled by the microcomputer 11 as shown in FIG. When an abnormal state is detected, the first input terminal 1 of the microcomputer 11
A short-time pulse signal discriminating circuit provided between the first voltage signal line 16a and the abnormality detecting circuit 12 which outputs a short-time pulse signal of a low voltage Vl to a first voltage signal line 16a connected to the first voltage signal line 16a; The diode 1 in which the output terminal 19 of the detection circuit 12 is disposed in a forward direction toward the output terminal 19
And the first voltage signal line 16a side of the diode 1 is grounded via the capacitor 2, while the abnormality detection circuit 12 is a low voltage detection circuit 12 for detecting an abnormal low voltage of the device. , The short-time pulse signal determination circuit detects an overcurrent or abnormal temperature rise of the device,
An overcurrent detection circuit 13 that outputs a short-time pulse signal of a low voltage Vl to a second voltage signal line 16b connected to a second input terminal 11b of the microcomputer 11;
A latch circuit that receives a short-time pulse signal of the low voltage Vl from the low-voltage detection circuit 12 or the overcurrent detection circuit 13 and outputs an interrupt signal to an interrupt input terminal 11c of the microcomputer 11; It is characterized by.

[0007]

Now, if an abnormal low voltage is generated in the device, the low voltage detection circuit 12 detects this and sends a short-time pulse signal of the low voltage Vl to the voltage signal line 16a connected to the first input terminal 11a. On the other hand, if an overcurrent or abnormal temperature rise occurs in the device, the overcurrent detection circuit 13 detects this and outputs a short-time pulse of the low voltage Vl to the voltage signal line 16b connected to the second input terminal 11b. Output a signal. Here, the first input terminal 11a
Is connected to the output terminal 19 of the low-voltage detection circuit 12 through the first voltage signal line 16a and the diode 1 in the forward direction, and the first voltage signal line 16a side of the diode 1 is connected to the capacitor 2
Grounded.

Accordingly, the low-voltage detecting circuit 12 detects an abnormal low voltage of the device and outputs the low voltage Vl to the first voltage signal line 16a.
, A current instantaneously flows from the power supply 14 to the low-voltage detection circuit 12 via the first voltage signal line 16a and the diode 1, and accordingly, the first voltage signal line 16a of the diode 1 The electric charge stored in the side capacitor 2 is completely discharged. Next, when the device returns to normal, the output terminal 19 of the low-voltage detection circuit 12 on the other side of the diode 1 becomes higher in voltage than one side connected to the power supply 14, and the voltage of the power supply 14 becomes the first voltage. The signal is applied to the signal line 16a. However, since the voltage signal line 16a is grounded via the non-charged capacitor 2, the first input terminal 11a of the microcomputer 11 does not immediately become the high voltage Vh, but gradually while the capacitor 2 is charged. It approaches the high voltage Vh.
Therefore, the microcomputer 11 determines that the first input terminal 11a is at a low voltage (L level). On the other hand, the second input terminal 11b
Unlike the first input terminal 11a, since there is no diode or capacitor, the overcurrent detection circuit 13 detects an overcurrent of the device and outputs a short-time pulse signal of the low voltage Vl to the second voltage signal line 16b. Even if the overcurrent or the like is eliminated, the voltage becomes the high voltage Vh immediately.
1b is determined to be a high voltage (H level). On the other hand, the latch circuit 20 outputs an interrupt signal to the interrupt input terminal 11c of the microcomputer 11 upon receiving any one of the short-time pulse signals. Then, the microcomputer 11 interrupts the program being executed in response to the interrupt signal, and if the first input terminal 11a is at a low voltage (L level), the input terminal 11a is connected to both input terminals 1a.
If 1a and 11b are high voltages (H level), it is determined that short-time pulse signals of low voltage Vl have been input to the second input terminals 11b, respectively. Accordingly, the microcomputer 11 can surely recognize whether the device has a low voltage or an overcurrent (abnormal temperature rise), and executes appropriate processing for each abnormality.

[0009]

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

FIG. 2 shows how the voltage of the first input terminal 11a of the microcomputer connected to the low voltage detection circuit 12 via the resistor 18a, the diode 1, the NAND gate 19 and the capacitor 2 is changed by the operation of the low voltage detection circuit 12. Change. That is, when the air conditioner is normal, the NAND gate 19 which is the output terminal of the low voltage detection circuit 12 is
Since it always outputs a higher voltage than the other side of the diode 1,
The first input terminal 11a receives the voltage of the constant voltage power supply 14 as shown in the initial stage of FIG. Also,
The capacitor 2 is charged. Next, when an abnormal low voltage is generated in the air conditioner, the low voltage detection circuit 12 detects the abnormal low voltage.
Output a low-voltage short-time pulse signal through the 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 voltage of the first input terminal 11a becomes low as shown in FIG. The voltage drops rapidly to the voltage Vl, and the electric charge stored in the capacitor 2 is completely discharged. Note that the signal output from the NAND gate 19 is a pulse signal having a relatively long duration of 600 μsec in the example of FIG. 2 and does not interfere with the determination of the microcomputer 11. If it is short, the conventional example interferes with the judgment of the microcomputer 11. However, in the present embodiment, such a problem does not occur because the following measures are taken. In the example of FIG.
At time t ₁ after c, the abnormal low voltage of the air conditioner is eliminated, the NAND gate 19 outputs a high voltage again.

Accordingly, the voltage of the constant voltage power supply 14 is applied again 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 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 270 from the end time t _{1 of the} pulse signal.
is 1V it is determined that the low voltage (L level) even μsec elapsed time t _2. The microcomputer 11 receives the interrupt signal from the latch circuit 20 at time t ₀ when a voltage fall, first, second input terminals 11a, 11b fixed time one has either a low voltage (t ₀ From 200 μsec after), even if the time during which the pulse signal is output (time from t ₀ to t ₁ ) is extremely short, it must be a low voltage (L level) from the start time of the pulse signal. The time until the determination (time from t ₀ to t ₂ ) is 270 μsec or more, and the microcomputer 11 can always determine and recognize this low voltage.

[0012] The short-time pulse signal discriminating circuit having the above-described configuration includes:
It works as follows. If an abnormal low voltage is generated in the air conditioner, the low voltage detection circuit 12 detects this, and the first signal line 16a extending from the NAND gate 19 to the first input terminal 11a.
To output a low-voltage short-time pulse signal. If an overcurrent or abnormal temperature rise occurs in the air conditioner, an overcurrent detection circuit 1
3 detects this, and the second input terminal 11b is connected to the second input terminal 11b.
A low-voltage short-time pulse signal is output to the signal line 16b.
If these short pulse signal is output, taking into the microcomputer 11, during the above at least 270μsec from time t ₀ to the first input terminal 11a is described in FIG low voltage
(L level), the second input terminal 11b is again a high voltage from the time t ₁ since there is no diode or capacitor within 200 .mu.sec (H level). On the other hand, the latch circuit 20
Upon receiving any one of the short-time pulse signals from the signal lines 16a and 16b, the microcomputer 11 outputs an interrupt signal to the interrupt input terminal 11c of the microcomputer 11.

When the microcomputer 11 receives the interrupt signal in step S1 of FIG. 3, the microcomputer 11 interrupts the program being executed,
The process proceeds to a subroutine for abnormality processing. Then, 200 μsec after the reception of the interrupt signal, it is determined in step S2 whether or not the first input terminal 11a is at the low voltage Vl. If yes, the program for the low voltage abnormality processing is executed in step S3. Or because the fin temperature is abnormally high, step S
Proceed to 4. In step S4, it is determined whether or not the fin temperature is abnormally rising based on a detection signal from a fin temperature sensor (not shown).
If not, a program for overcurrent abnormality processing is executed in step S6. Thus, when the execution of any of the abnormality processing programs is completed, the process returns to the main routine.

Thus, unlike the conventional example, the microcomputer 11 can surely recognize whether the air conditioner has a low voltage, an overcurrent, or a fin temperature rise, and can perform appropriate processing for the low voltage abnormality. Can be performed, and a failure or accident of the air conditioner due to excessive processing can be eliminated. In the above embodiment, the overcurrent detection circuit 13 is added to the low voltage detection circuit 12 including the diode 1 and the capacitor 2, and the microcomputer 11 receives the short-time pulse signal from these detection circuits and sends the abnormality processing routine to the microcomputer 11. Is output, so that a plurality of abnormal states of the controlled device can be appropriately dealt with with a simple circuit configuration.

[0015]

As is apparent from the above description, the short-time pulse signal discriminating circuit of the present invention detects an abnormally low voltage of a controlled device and outputs a low-voltage short-time pulse signal. An output terminal of the circuit and a first voltage signal line connected to a first input terminal of the microcomputer are connected by a diode arranged in a forward direction toward the output terminal, and a first voltage signal line side of the diode is connected to a capacitor. Grounded through
An overcurrent detection circuit that detects an overcurrent or abnormal temperature rise of the controlled device and outputs a low-voltage short-time pulse signal is connected to the second input terminal of the microcomputer. Since the interrupt signal is output to the interrupt input terminal of the microcomputer by the latch circuit that receives the signal, the low-voltage short-time pulse signal input to the input terminal must be maintained for a long time so that the microcomputer can detect it. With a simple configuration, the microcomputer can appropriately cope with various abnormal states occurring in the controlled device.

[Brief description of the 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 a change in voltage at a first input terminal of the microcomputer of 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 determination circuit.

[Explanation of symbols]

DESCRIPTION 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, 16b ... Second signal line, 19: NAND gate.

Claims (1)

(57) [Claims] 1. A microcomputer (11) for detecting an abnormal state of a device controlled by the microcomputer (11), and detecting a first voltage connected to a first input terminal (11a) of the microcomputer (11). Low voltage on signal line (16a)
(Vl) abnormality detection circuit (1
A short-time pulse signal discriminating circuit provided between the first voltage signal line (16a) and the output terminal (19) of the abnormality detection circuit (12). And the first voltage signal line (16a) side of the diode (1) is connected to a capacitor.
While being grounded via (2), the abnormality detection circuit (12)
Is a low voltage detection circuit that detects abnormal low voltage of the above devices
(12), wherein the short-time pulse signal discrimination circuit detects an overcurrent or an abnormal temperature rise of the device, and a second pulse signal discrimination circuit connected to a second input terminal (11b) of the microcomputer (11).
An overcurrent detection circuit (13) for outputting a short-time pulse signal of a low voltage (Vl) to the voltage signal line (16b) is provided, and the low-voltage detection circuit (12) or the low-current detection circuit (13) outputs a low-voltage signal. A short-time pulse having a latch circuit (20) for receiving a short-time pulse signal of a voltage (Vl) and outputting an interrupt signal to an interrupt input terminal (11c) of the microcomputer (11); Signal discrimination circuit.