JPH06276077A - Reset circuit - Google Patents

Abstract

PURPOSE:To suppress the operation of the reset circuit only for a specific time according to the operation state of equipment by providing a reresetting suppression part which suppresses the resetting operation of a rereset part at necessary time. CONSTITUTION:The reset circuit is equipped with a reset pulse generation part 1 which resets an electronic circuit, the rereset part 4 which detects a drop in the source voltage of the electronic circuit and resets the electronic circuit, and the reresetting suppression part 2 which suppresses the reresetting operation at desired time. In a period wherein reresetting is improper judging from the in-use state and processing state of the electronic circuit, the operation of the rereset part 4 is suppressed through the operation of the reresetting suppression part 2 and even if the source voltage drops, the reresetting operation is not performed. Thus there is not such trouble that the electronic circuit is rereset unconditionally even during operation if the source voltage drops and the reresetting is inhibited only when the reresetting is not preferable or unnecessary, thereby setting a proper inhibition period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reset circuit for electric equipment, and more particularly to a reset circuit applied to an electronic circuit using a microprocessor or the like and having a re-reset function due to a decrease in power supply voltage.

[0002]

2. Description of the Related Art In various electronic devices, a reset circuit for generating a reset signal (initial reset) at the time of starting operation is used to initialize the device. In addition to this initial reset, in electronic devices that require particularly high reliability, the power supply voltage of the device drops during operation (mainly for a short time: momentary power failure) before the electronic circuit becomes abnormal and runs away. A function to reset (re-reset function) may be added.

Each of the block diagrams in FIGS. 2 and 3 shows an example of a conventional reset circuit including such a power supply voltage drop detection circuit (instantaneous power failure detection circuit), and each device uses an AC power supply. Shows the case of equipment using a DC power supply.

In FIG. 2, reference numeral 5 is a step-down rectifier of an AC power supply (for example, a commercial power supply AC100V) supplied to the equipment,
This is a step-down rectifier that produces a direct current of, for example, 5V. DC 5
The output of V is supplied to the power supply voltage drop detection circuit 4A, the reset pulse generator 1, and the electronic circuit described later. The step-down rectifier 5 also outputs an AC 6.3V that has been stepped down, and is also input to the power supply voltage drop detection circuit 4A described later.

The reset pulse generator 1 generates a reset signal when the electronic device is first operated (power-on reset).
At the same time, if the power supply voltage drops even during operation of the device, a reset signal is generated by the output from the power supply voltage drop detection circuit 4A (re-reset). Power supply voltage drop detection circuit 4
A monitors the input AC 6.3V and sends out a detection signal when there is a drop in the power supply voltage due to an instantaneous power failure, etc., whereby the reset pulse generator 1 generates a reset signal and resets the electronic circuit again. . As a result, the runaway or the like due to the instantaneous power failure of the electronic device described above is avoided.

In FIG. 3, the output of 5V DC is supplied to the voltage monitoring IC (power supply voltage drop detection) 4B, the reset pulse generator 1, and other parts of the electronic circuit. Similar to the case of FIG. 2, the voltage monitoring IC 4B monitors the power supply voltage,
When the power supply voltage drops, a detection signal is sent out, whereby the reset pulse generator 1 generates a reset signal and resets the electronic circuit again. In this way, the runaway or the like due to the decrease in the power supply voltage of the electronic device is prevented.

In the conventional reset circuit (with a reset function) as described above, the power supply is always monitored during the operation from power-on to power-off, and if there is a drop, reset is performed again. I will end up.

By the way, it is effective in many cases to monitor a momentary power failure and to perform a reset, but it may cause a problem depending on the situation. For example, this is the case when extremely important processing is performed in the operation process and interruption of the processing leads to runaway of other parts of the device, or the case where valuable data may be lost.

In such a case, continuing the processing can minimize the damage even if the complete result is not obtained, and is a better result than resetting the whole. Needless to say, except for the case described above, it is more useful to prevent the runaway by resetting in response to a momentary power failure during most of the operating time.

In addition to the above-mentioned problems, in addition to the above-mentioned conventional initial reset (power-on reset), a reset circuit configured to appropriately reset again causes a reset operation due to noise or the like. Therefore, it is required to increase the noise margin of the reset circuit section.

[0011]

SUMMARY OF THE INVENTION The present invention, as described above, has a serious problem depending on the operating state of the device in the uniform function of the reset circuit which performs the reset operation in response to the instantaneous power failure as described above. The present invention has been made in order to solve the problem that the above-mentioned problem occurs, and proposes a reset circuit having a function of suppressing the operation of the reset circuit for a predetermined time according to the operating state of the device. At the same time, it is also an object to propose a reset circuit having a particularly high noise margin in the reset operation.

[0012]

In order to solve the above problems, in the first invention of the present application, a reset circuit is provided with a reset pulse generator for resetting an electronic circuit, and an electronic device for detecting a decrease in power supply voltage of the electronic circuit. A configuration is provided that includes a re-reset unit that resets the circuit and a re-reset suppression unit that suppresses the reset operation of the re-reset unit when desired.

Further, in the second invention of the present application, in the reset circuit described above, the power source of the re-reset suppressing unit is a power source different from the power source of the other circuit, and the connection with the other circuit is not based on electrical connection. The configuration.

[0014]

According to the first aspect of the present invention, the operation of the re-reset suppressing unit suppresses the operation of the re-resetting unit during the period in which the re-resetting is not appropriate due to the use state of the electronic circuit or the processing stage, so that the power supply voltage decreases. However, the reset operation is not performed.

Further, in the second invention of the present application, since the reset reset suppressing portion is electrically insulated from other portions, the predetermined operation can be surely performed without being influenced by noise of each portion, and the system reliability can be improved. Is improved.

[0016]

The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram of a reset circuit showing an embodiment of both inventions of the present application. The reset circuit having the power supply voltage drop detection function (instantaneous power failure detection function) includes a reset pulse generation unit 1, a re-reset unit 4, a re-reset suppression unit, and a control unit 3.

Also in the embodiment, the reset pulse generator 1 generates a reset signal at the time of initial operation of an electronic device (power-on reset), as in the above-described conventional circuit, and when the power supply voltage drops even during device operation. In principle, a reset signal is generated by the output from the power supply voltage drop detection circuit 4 via the re-reset suppression unit 2 (re-reset).

The resetting section 4 (voltage drop detection circuit) is
The power supply voltage drop detection circuit 4A (FIG. 2) and the voltage monitoring IC: 4B (FIG. 3) described above are substantially the same as the power supply voltage (DC 5V) supplied to the electronic circuit and monitor for an instantaneous interruption. When there is a decrease in the power supply voltage due to the above, a detection signal is sent out. However,
This detection signal is input to the re-reset suppressing unit 2 in the embodiment. The DC power supply may be one that is converted from AC.

The re-reset suppressing unit 2 is connected to the output of the re-resetting unit 4 and transmits the output signal from the re-resetting unit 4 to the reset pulse generating unit 1 in response to the input from the control unit 3. It is appropriately configured so as not to transmit. The control unit 3 is provided to limit the period (state) in which the reset signal is valid.

The input end and output end of the re-reset suppressing unit 2 are electrically connected to each other by the photocouplers 2A and 2B. That is, on the input side, the output of the re-reset unit 4 drives the light emitting diode D21 of the photocoupler 2A, and on the output side, the terminal of the phototransistor TR29 of the photocoupler 2B is connected to the reset pulse generation unit 1, so-called current. It is composed of a loop interface and transmits signals with low current. The power source of the control unit 3 connected for control is a power source different from the power source of the electronic circuit or the like. In this way, the power supply of the re-reset suppression unit is different from the power supply of other circuits, and the connection with other circuits does not rely on electrical connection. Highly prevents malfunction.

In the embodiment, by applying the DC voltage from the control unit 3, the phototransistor TR2 of the photocoupler 2A.
2 and the TR 27 for driving the light emitting diode D28 of the photocoupler 2B and the respective circuit parts are operated, and accordingly, the voltage stamp from the control part 3 (suppression signal OFF).
At times, if the reset signal generator 4 generates a signal, this signal is input (transmitted) to the reset pulse generator 1 via the reset reset suppressor 2, and as a result, the reset pulse generator 1 is reset.
Generates a reset signal and resets the electronic circuit again to avoid runaway of electronic equipment due to momentary power failure.

On the other hand, if there is no direct voltage imprint from the control unit 3 (suppression signal ON), each part of the re-reset suppression unit will be in an inoperative state. Is not transmitted to the reset pulse generator 1, and therefore even if there is an instantaneous blackout, the reset pulse generator 1 is prevented from resetting the electronic circuit again, the processing of the electronic circuit is continued, and valuable data is saved. It is possible to avoid inconveniences such as loss of information etc.

The reset inhibition period determined by the control unit 3 is controlled by the program of the electronic device. For example, when an important calculation is started, the reset is suppressed until the calculation is completed, or important data is imported. In such a case, it is possible to prevent re-reset until necessary processing is completed, or to prevent re-reset due to a power failure that is performed under the control when a momentary power failure is expected. Only for a predetermined period, the reset is suppressed, the reset is permitted in the other period, and the runaway such as the original power supply voltage drop described at the beginning is reset by the reset.

In the embodiment, various well-known circuits can be used to suppress the signal, and the point is that the circuit network can suppress the transmission of the reset pulse by the control input from the outside. Further, although the signal path is electrically insulated using the photo coupler, the electrical insulation may be achieved by an appropriate method such as using a relay. Since the control unit 3 supplies electric power as a control signal, the control unit 3 may be connected to a power source via a controllable contact as appropriate.

[0025]

As described above, the reset circuit of the present invention detects the drop of the power supply voltage of the electronic circuit and resets the electronic circuit. The reset circuit suppresses the reset operation of the reset circuit. Therefore, if there is a drop in the power supply voltage even during operation, there is no inconvenience of resetting uniformly, and it is possible to suppress resetting only when resetting is not desirable or when resetting is unnecessary. By setting an appropriate deterrent period, for example, the system is performing important processing, and interruption of processing will avoid runaway of other parts of the device and avoid inconvenience such as loss of valuable data. It becomes possible. Of course, the re-reset function can be effectively utilized during the other period.

Further, according to the second invention of the present application, the power supply of the re-reset suppressing unit of the above invention is a power supply different from the power supply of the other circuit section, and the connection with other circuits is not based on electrical connection. Therefore, in addition to the above-mentioned effects, the noise margin of the re-reset suppressing unit is high, and therefore it is possible to prevent the inconvenience of performing the re-reset operation due to noise or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a reset circuit of the present invention.

FIG. 2 is a block diagram showing an example of a conventional reset circuit.

FIG. 3 is a block diagram showing another example of a conventional reset circuit.

[Explanation of symbols]

 (1) ... Reset pulse generating section, (2) ... Re-reset suppressing section, (3) ... Control section, (4) ... Re-resetting section.

Claims (2)

[Claims] 1. A reset pulse generator (1) for resetting an electronic circuit, a re-reset unit (4) for detecting a drop in the power supply voltage of the electronic circuit and resetting the electronic circuit, and a re-reset unit (4). A reset circuit having a reset reset suppressing section (2) for suppressing the reset operation of the device when desired. 2. The power supply of the re-reset suppressing unit (2) is different from the power supply of other circuits, and the connection with other circuits is not electrically connected. The reset circuit described.