JPS5931084B2 - Auto clear device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an auto-clear device that generates a clear signal to set the control part of a device to its initial state when the power is turned on, and particularly in the case of a momentary power outage or the like during use after the power is turned on. Even if the state of the control section changes due to an instantaneous drop in power supply voltage, a clear signal can be automatically generated to set the control section to its initial state. The purpose of the present invention is to provide an auto-clear device that also includes means for preventing unnecessary signals from being output when the vehicle is descending.

As shown in Figure 1, the conventional auto clear device has a power supply vc.
When C is turned on, the transistor Trl is turned off and the transistor Tr2 is turned on for a time determined by the time constant of the resistor R3 and the capacitor C3, and an auto clear signal ACL is generated from the output terminal A when this terminal is at the LOW level.

However, if the voltage of the power supply Vcc fluctuates due to a momentary power outage, not only when the power is turned on but also when the device is in use, for example, integrated circuits (ICs) are guaranteed to operate within a range of 5V (±5%). However, if this range is exceeded, operation is no longer guaranteed.

In other words, due to momentary power outage, 5
If the V power supply drops to 4.5V and rises again to 5V, the condition of the flip-flops of the IC used in the device cannot be guaranteed.

Therefore, even in such a case, it is necessary to generate an auto-clear signal and set the control section of the device to its initial state, but with the conventional circuit configuration described above, after generating the auto-clear signal once when the power is turned on, It was not possible to generate an auto clear signal under the above conditions.

It converts the charged charge of capacitor C3 into R3, C
This is because it is necessary to discharge with a time constant of 3, and the level of C3 does not drop until the transistor Trl is instantaneously turned off.

As described above, the conventional auto-clear device cannot deal with the case where the drop in the power supply voltage exceeds the guaranteed range of the control part when the device is in use after the power is turned on.

In view of the above points, the present invention detects when the drop in power supply voltage exceeds the guaranteed range of the control part when the device is in use after the power is turned on, and instantly discharges the charge stored in the capacitor. The present invention is an auto-clear device that generates an auto-clear signal by using a 10-minute drive, and is capable of setting a control part to an initial state. The present invention will be explained below with reference to the circuit configuration shown in FIG. In FIG. 2, block 1 is a clear signal generating circuit and has the same configuration as in FIG. 1, and the same parts are designated by the same reference numerals.

The power supply Vcc is set to, for example, a +5V power supply. Vt is another power source higher than the power source Vcc, and is set to, for example, +12V1+24V.

COMP is a comparator that operates on a low voltage power supply, and is connected to this non-inverting terminal (a) from the power supply Vcc via an input protection resistor R2, and is also an inverting terminal ←)
Polyum VR is connected to this comparator C.
Diode D1 from power supply Vt as the power supply voltage of OMP,
A low voltage VREf at which the comparator COMP can operate is created and controlled by the circuit configuration of the resistor R1, the capacitor C1, and the Zener diode ZD. Further, the output terminal of the comparator COMP is connected between the resistor R3 and the capacitor C3 of the clear signal generating circuit 1 via the diode D2. The diode D1 above is the capacitor C
The discharge time constant of the capacitor C1 is approximately determined by C1×VR, and by selecting a large value for both, it is possible to increase the voltage drop time during a power outage or the like.

Diode D2 is for blocking charging current to capacitor C3. The above-mentioned comparator COMP compares the voltage levels of the inverting terminal (G) and the non-inverting terminal (4). It operates so that a similar voltage is output.

Therefore, the polyurethane VR connected to the (to) side of the comparator COMP is set to the minimum guaranteed level (4.75V) of the IC power supply voltage.

To explain the circuit operation of FIG. 2 together with the time chart of FIG. 3, when the power is turned on, the clear signal generating circuit 1
turns off the transistor Trl and turns on the transistor Tr2 for a time determined by the capacitor C3 and the resistor R3 to set the output terminal A to the LOW level, and outputs the auto clear signal AC.
L is generated to set the control unit to the initial state.

When normal power is supplied after the auto clear signal ACL is generated, the (A) side terminal of the comparator COMPf is higher than the (C) side terminal, so this output becomes a voltage close to the power supply voltage VREf of the comparator COMP. ,
The transistor Trl is on and the transistor Tr2 is off, making it impossible to generate an auto-clear signal.

Now, when a power outage occurs, the power supplies Cc and REf drop, but due to the charging of the capacitor C1, the comparator COMP (
Since the voltage drop on the side) is set to be slow, the power supply Vcc
falls more quickly, and thus becomes a higher level than the (-l-) terminal of the comparator COMP, and the output of the comparator COMP approaches the ground level.

Then, the charge charged in the capacitor C3 is directly discharged through the diode D2, which turns off the transistor Trl, turns on the transistor Tr2, and sets the output terminal A to the LOW level, outputting an auto-clear signal. Ru. After that, the power supply is immediately restored and the power supply Vc
When c returns to the normal power supply voltage, the output of comparator COMP becomes a voltage close to this power supply voltage VREf, and after a delay of the time constant of capacitor C3 and resistor R3, transistor Tr
, turns on, transistor Tr2 turns off, and the auto clear signal stops.

Therefore, when an instantaneous power outage or the like occurs, the control section is set to the initial state by generation of the auto clear signal.

FIG. 4 shows an embodiment in which the above-mentioned auto-clear device is implemented in, for example, external input/output equipment (terminals), etc., in which φ to N terminal equipments are provided and these equipments are connected to a common bus line 41. Indicates a connected state.

Then, a bus line 41 provided for each terminal device φ to N
The input side of the output gate 42 . . . and circuit elements installed in the device, such as flip-flops 43 . . .・An auto clear device 4 with the configuration shown in Fig. 2 is installed on each glue set side.
4 output signals are introduced. Therefore, when a momentary power outage occurs in one of these terminal devices φ to N, or when the power supply is cut off, the power supply Vcc voltage falls, and during this falling transition, various logic elements used in the device fail. Since a stable state, that is, the state of the logic element cannot be guaranteed, the auto clear device 44 turns the auto clear signal ACL to LOW when the IC power supply voltage reaches the minimum guaranteed level and outputs the output gate. 42,...
. . . is immediately closed, thereby preventing the signal outputted when the logic element is in an unstable state from being sent to the bus line 41.

That is, it is possible to prevent unreliable and unnecessary signals from being output to the bus line 41. In addition, the auto clear device 44
Inverts the output signal from the flip-flop 43...
Since the input is made to the glue set side, these flip-flops 43...
..... is reset and set to the initial state. As described above, the auto-clear device of the present invention detects this and generates an auto-clear signal even when the power supply voltage drops instantaneously due to a momentary power outage and exceeds the guaranteed range of the control section. between the device and the bus line to which the device is connected by opening/closing means that can set the control part to the initial state by causing the device to open and close the device in response to an auto-clear signal generated from the auto-clear signal generating circuit. Since the bus line is cut off, it is possible to prevent unnecessary signals from being generated on the bus line when the power supply voltage drops, and also to reliably prevent any negative effects on other devices connected to the bus line. It has the characteristics of

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram showing a conventional auto clear device, Fig. 2 is an electric circuit diagram showing an auto clear device of the present invention, Fig. 3 is a time chart of the configuration shown in Fig. 2, and Fig. 4 is an electric circuit diagram showing the auto clear device of the present invention. FIG. 2 is a block diagram showing an embodiment in which the invention auto-clearing device is used in a device. 1: Clear signal generation circuit, Cc: power supply, Vt: power supply higher than Vcc, C1 and C3: capacitors, R,, R2,
R3: Resistor, COMP: Comparator, Dl, D2: Diode, ZD: Zener diode, Trl, Tr2
: Transistor, A: Output terminal.

Claims (1)

[Claims] 1. An auto-clear signal generation circuit that generates an auto-clear signal to the control section of the device for a time determined by the time constant of a capacitor and a resistor when the device is powered on, and a predetermined signal that detects fluctuations in the power supply voltage to the auto-clear generation circuit. means for discharging the charge charged in the capacitor of the auto-clear generating circuit when the voltage drops below the voltage; and a bus to which the device is connected in response to the auto-clear signal generated from the auto-clear signal generating circuit. An auto-clear device equipped with an opening/closing means to cut off the line.