JPH01202673A - Momentary interruption detecting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The purpose of this invention is to distinguish between a long-term power outage and a momentary power outage, regarding a momentary power outage detection circuit, and to turn on the power by detecting that the power supply voltage has fallen below a predetermined level. A power supply voltage drop detection means for outputting a reset signal, a timer means for counting the elapse of a predetermined time since the voltage drop, and a power cutoff determination means for determining that the power supply has been cut off when the drop continues for the predetermined time. Configure so that you are prepared.

[Industrial application field]

The present invention relates to a momentary power outage detection circuit, and more particularly to a momentary power outage detection circuit that distinguishes between a long-term power outage and a short-term power outage, that is, a momentary power outage.

In mobile communications, such as car phones, the energy stored in the alternator's rotating coil is momentarily cut off due to negative surges caused by turning on and off the ignition key or air conditioner, causing a sudden drop in the middle of a call. Power may be cut off for a short period of time. In such a case, if the line remains connected, the call can be continued after the short power-off without repeating the line connection procedure again. Therefore, long-term power outages and very short power outages,
In other words, there has been a need for a technology that can distinguish between instantaneous interruptions.

[Prior art and problems to be solved by the invention]

Conventionally, in car phones, etc., when the power is cut off for a very short time in the middle of a call, the instantaneous power outage is short, and after the instantaneous power outage,
There is a problem in that even if there is no problem with the call even if the call is resumed, the call is disconnected and it is necessary to perform the line connection operation again.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a momentary power failure detection circuit that distinguishes between a long-term power failure and a momentary power failure.

[Means to solve the problem]

Figure 1 is a basic configuration diagram of the present invention. In this figure, 1
2 is a power supply voltage drop detection means, 2 is a timer means, and 3 is a power-off determination means.

The power supply voltage drop detection means 1 detects that the power supply voltage has fallen below a predetermined level and outputs a power-on reset signal. The timer means 2 measures the elapse of a predetermined period of time from the time of the drop. Then, the power-off determination means 3
When the decrease continues for the predetermined period of time, it is determined that the power is turned off.

[For production]

When it is detected that the power supply voltage has decreased below a predetermined level by the power-on reset signal by the power supply voltage drop detection means 1, if the decrease does not continue for a predetermined period of time, it is determined that a momentary interruption has occurred, and the power supply voltage drops below the predetermined level. If the decrease continues for a certain period of time, it is determined that the power has been cut off.

〔Example〕

FIG. 2 shows the configuration of the first embodiment of the present invention. In FIG. 2, 4 is a microcomputer, 10 is an operational amplifier, and 15 is an automatic voltage regulator.
c voltage regulator (hereinafter also referred to as AVR), 20 is a timer IC, and 30 is a D flip-flop circuit. The AVR 15 outputs a constant voltage based on a variable power source that is not affected by fluctuations in the battery power source voltage or load. The timer IC 20 starts timing when the trigger input signal falls, and measures a predetermined period of time that serves as a reference for distinguishing between a momentary power outage and a power outage lasting longer than that.The operational amplifier 10 has an inverting input terminal. The output voltage of the AVR 15 is applied as a reference voltage, and the battery power supply voltage is applied to the non-inverting input terminal of the resistor 12.
and 13 and are applied as partial pressures. The output terminal of the operational amplifier 10 is connected to the non-inverting input terminal via a resistor 11, and is connected to the AVR1 via a resistor 14.
It is also connected to the output terminal of 5. In this way, a comparator circuit (hereinafter referred to as a power supply voltage threshold) having a threshold value (hereinafter referred to as a power supply voltage threshold value) determined by the ratio of the resistance values of the resistors 12 and 13 and the output voltage value of the AVR 15 A comparison circuit (referred to as a comparison circuit) is constructed.

The output of the power supply voltage comparison circuit is "H" level while the battery voltage is above the threshold value, and L level while the battery voltage is below the threshold value.The configuration of this power supply voltage comparison circuit is the first one. This corresponds to the power supply voltage drop detection means 1 shown in the figure.

The output of the power supply voltage comparison circuit is applied to the negative edge trigger terminal and clear terminal of the timer IC 20, and is further applied to the D flip-flop circuit 3 via the inverter 31.
0 data input terminal, and the output of the inverter 31 is input to the microcomputer 4 as a power-on reset signal.

The output of the timer IC 20 rises in synchronization with the fall of the input signal from the power supply voltage comparison circuit, and similarly falls in synchronization with the rise of the clear signal CLH output from the power supply voltage comparison circuit, or falls in synchronization with the fall of the input signal from the power supply voltage comparison circuit. It is assumed that the input signal falls after the predetermined time has elapsed from the point at which the input signal falls. This timer IC20
The output of is applied to the negative edge trigger input terminal of D flip-flop circuit 30. Also, this timer ■C20
corresponds to the timer means 2 in FIG.

With the above configuration, the D flip-flop circuit 3
The Q output of 0 is such that the output of the power supply voltage comparison circuit is "L" for the predetermined time measured by the timer IC 20.
By having a certain level, you can stand up. This Q output is applied to the microcomputer 4 as a power-off signal.

When the microcomputer 4 receives the power-on reset signal, it holds the previous information in an internal register and waits for the power supply voltage to recover, and after the predetermined time elapses,
When receiving an "H" level output from the D flip-flop circuit 30, that is, a power-off signal, it is determined that the power is off, and the processing operation that continues until the power-on reset signal is received, such as a car phone The call will be disconnected. Further, upon receiving the power-off signal, the microcomputer 4 outputs a reset signal to the D flip-flop circuit 30 in order to detect the next power-off. The reset signal is applied to the negative logic clear input terminal of the D flip-flop circuit 30 through a driver circuit consisting of resistors 32, 34, 35 and the transistor 33, and resets the D flip-flop circuit 30.

If the power-off signal is not received within the predetermined time, the microcomputer 4 determines that there is a momentary power-off and processes the internal information held in the register immediately before receiving the power-on reset signal as an initial value. Resume operation.

Figure 3 shows the timing of the configuration in Figure 2.
At time t, when the battery voltage drops below the power supply voltage threshold shown by the broken line in FIG. 3, the output of the operational amplifier 10 goes to "L" level, causing a power-on reset shown by the FOR signal in FIG. A signal is applied to the microcomputer 4. and timer IC20
is the predetermined time (3rd
Time 11 before the elapsed time (indicated by T in the figure)
When the battery voltage recovers to above the threshold value of the power supply voltage, the output of the operational amplifier 10 becomes "H" level, and the timer IC 20 is also reset.

At time t3, the battery voltage again falls below the threshold of the power supply voltage, but this time, even at time t, when the predetermined time T has elapsed, the battery voltage does not recover above the threshold, and the operational amplifier Since the output of FF10 is still at the "L" level at the time t#, the output of FF10 in FIG.
The Q output of the D flip-flop circuit 30 indicated by 30 rises and is applied to the microcomputer 4 as a power-off signal. When the microcomputer 4 receives the power-off signal, it outputs a reset signal to the 39D flip-flop circuit 30, and at time ts), the D flip-flop circuit 30 is reset.

FIG. 4 shows the configuration of a second embodiment of the present invention. The configuration of FIG. 4 is the same as the configuration of FIG. 2 described above except for the timer circuit 21.

The timer circuit 21 also corresponds to the timer means 2 of FIG. 1, and has a configuration as shown in FIG. 5, for example.

The configuration shown in FIG. 5 measures the above-mentioned predetermined time based on the discharge time of an RC circuit consisting of a capacitor 208 and a resistor 209. The capacitor 208 has one end grounded and the other end connected to the AVR1 via the transistor 207.
Connected to 5.

The output of the power supply voltage comparison circuit, that is, the operational amplifier 1
The output of 0 is connected to resistors 201, 204, 206°, diode 202, transistor 205, and capacitor 20.
The voltage is applied to the base terminal of the transistor 207 with a slight delay by a driver circuit consisting of 3.

When the battery voltage is above the power supply voltage threshold, transistor 207 is turned on and capacitor 2
08 is charged by the current from the AVR 15, and while the battery voltage is below the threshold of the power supply voltage, the transistor 207 is discharged with the time constant of the RC circuit. The terminal voltage of the capacitor 208 is the voltage at the terminal of the operational amplifier 2.
12, feedback resistor 213, voltage dividing resistor 2 that determines the reference voltage
10.211, and a resistor 21 that determines the output level.
4 (hereinafter referred to as a terminal voltage comparison circuit). Normally, while the battery voltage is above the threshold of the power supply voltage, the output of the terminal current comparison circuit is held at the voltage of the AVR 15 (“H” level) by the resistor 214; is below the threshold of the power supply voltage, the capacitor 20
8 begins to discharge and the terminal voltage of the capacitor 208 falls below the terminal voltage threshold in the terminal voltage comparison circuit, the output of the terminal voltage comparison circuit, that is, the output of the operational amplifier 212 becomes "L" level. . The time constant of the RC circuit is such that the time from when the capacitor 208 starts discharging to when the output of the operational amplifier 212 becomes "L" level is determined by the above-mentioned instantaneous power interruption and a power interruption for a longer period of time. It is determined to match the time that serves as the standard for differentiation.

FIG. 6 shows the timing of the configuration represented by FIGS. 4 and 5.

At time t1, when the battery voltage drops below the power supply voltage threshold indicated by the broken line in FIG. 6, the output of the operational amplifier 10 becomes "L" level, and the power-on reset signal indicated by the FOR signal in FIG. 6 is activated. is applied to the microcomputer 4. The capacitor 208 in FIG. 5 then begins discharging. When the battery voltage recovers to the power supply voltage threshold or higher at time t2, which is before the aforementioned predetermined time (indicated by T in FIG. 6) has elapsed from time t1, the output of the operational amplifier 10 becomes "H". ″
5, capacitor 208 of FIG. 5 begins to charge before the terminal voltage falls below the terminal voltage threshold described above.

At time t3, the battery voltage falls below the power supply voltage threshold again, but this time, even at time t#, when the predetermined time T has elapsed, the battery voltage does not recover above the threshold, and the operational amplifier The output of No. 10 is still at the "L" level at the time t9. Therefore, the capacitor 208 in FIG. 5 continues to discharge even if the terminal voltage becomes below the threshold voltage of the terminal, and the output of the timer circuit 21 in FIG. 4, that is, the output of the operational amplifier 212 in FIG. At time t4, the level becomes 6L''. This timer circuit 21
4, the Q output of the D flip-flop circuit 30 in FIG. - A reset signal is output to the flop circuit 30. At time ts), the D flip-flop circuit 30 is reset.

FIG. 7 shows a second configuration example of the timer circuit 21 shown in FIG. 4. The difference from the first configuration example shown in FIG.
The point is that a CMO8 type inverter 215 is used instead of 05. Even with the timer circuit of FIG. 7, the operation and timing of the configuration of FIG. 4 are similar to those of the configuration of FIG. 5 described above.

In this way, according to the configurations of FIGS. 2 and 4,
Unless the power supply voltage remains below a predetermined threshold for a predetermined period of time, it will not be judged as a power outage, but will simply be a momentary power outage, and after the power supply voltage is restored, the internal Processing operations can be restarted based on the information.

〔Effect of the invention〕

According to the present invention, it is possible to distinguish between a long-term power outage and a momentary power outage, so if the information immediately before the momentary power outage is retained, the new information can be updated after the power is restored. It becomes possible to continue the processing operation without repeating the initialization operation.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram of the present invention, Figure 2 is a configuration diagram of the first embodiment of the present invention, and Figure 3 is a diagram of the second embodiment.
FIG. 4 is a timing diagram of the configuration shown in FIG. 4, and FIG. 4 is a configuration diagram of a second embodiment of the present invention. 5 is a diagram showing a first configuration example of the timer circuit 21 in FIG. 4, FIG. 6 is a timing diagram of the configurations in FIGS. 4 and 5, and FIG. 7 is a diagram showing the timer circuit 21 in FIG. 4. It is a figure showing the 2nd example of composition. [Explanation of symbols] 1...Power supply voltage drop detection means, 2...Timer means, 3...Power cutoff determination means,
4... Microcomputer, 10.212... Operational amplifier, 15... Automatic voltage regulator (AVR), 20... Timer IC, 21... Timer circuit, 30... D flip-flop circuit. Basic configuration diagram of the present invention Figure 1 Figure 2 Timing diagram of the configuration shown in Figure 2 Figure 3 Configuration diagram of the second embodiment of the invention Figure 4 First configuration example of the timer circuit 21 shown in Figure 4 FIG. 5 t6 A timing diagram for the configuration shown in FIG. 4 FIG. 7 A diagram showing a second configuration example of the timer circuit 21 in FIG. 4

Claims (1)

[Claims] 1. A power supply voltage drop detection means (1) that detects that the power supply voltage has fallen below a predetermined level and outputs a power-on reset signal; A momentary power outage detection circuit comprising: timer means (2) for counting time; and power outage determining means (3) for determining a power outage when the drop continues for the predetermined time. 2. The power supply voltage drop detection means (1) compares an automatic voltage regulator (15) that outputs a predetermined reference voltage with a voltage obtained by dividing the power supply voltage at a predetermined voltage division ratio and the reference voltage. The instantaneous interruption detection circuit according to claim 1, further comprising a comparison circuit (10, 11, 12, 13, 14). 3. The instantaneous power failure detection circuit according to claim 1, wherein the power interruption determination means (3) includes a latch circuit (30) that latches the output of the power supply voltage drop detection means (1) at the timing of the elapse of the predetermined time. . 4. The timer means (2) includes a capacitor (208) that is charged when the power supply voltage is above the predetermined level and discharged when it is below the predetermined level, and a terminal voltage of the capacitor (208) that is 2. The momentary interruption detection circuit according to claim 1, further comprising a comparison circuit (210, 211, 212, 213, 214) for comparison with a reference voltage.