JP7161365B2 - Power failure detection device and half-wave detection circuit - Google Patents

Description

The present invention relates to a power failure detection device and a half wave detection circuit.

2. Description of the Related Art In general, electronic devices such as image forming apparatuses are equipped with storage devices such as memories and hard disks. When a commercial AC power failure occurs, the data stored in the storage device may be lost. Therefore, it is necessary for the electronic device to detect the power failure and save the data. According to Patent Document 1, it is proposed to use a half-wave detection circuit to detect a commercial AC power failure.

JP-A-7-229930

The half-wave detection circuit according to Patent Document 1 cannot immediately detect a power failure that occurs during a period in which no current flows through the light-emitting diode. More specifically, the half-wave detection circuit of Patent Document 1 cannot detect the occurrence of a power failure in a time shorter than the half cycle of alternating current. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power failure detection device capable of detecting the occurrence of a power failure in a shorter time.

The present invention, for example,
A first logic detection signal is output during a period in which the polarity of the alternating current supplied from the alternating current power supply is the first polarity, and the polarity of the alternating current supplied from the alternating current power supply is the second polarity opposite to the first polarity. detection means for outputting a detection signal of the second logic in a certain period;
timer means for measuring the time between the timing at which the logic of the detection signal switches from the first logic to the second logic and the timing at which the logic of the detection signal switches from the second logic to the first logic;
determining means for determining that a power failure has occurred in the AC power supply when the time measured by the time measuring means becomes shorter than the half cycle of the AC power supply;
When the supply of alternating current from the AC power supply is interrupted while the detection signal of the second logic is being output, outputting the detection signal of the first logic,
When the supply of alternating current from the AC power supply is interrupted while the detection signal of the first logic is being output, the detection signal of the second logic is temporarily output, and then the detection of the first logic is performed. A power failure detection device, characterized in that it is configured to restart signal output.

ADVANTAGE OF THE INVENTION According to this invention, the power failure detection apparatus which can detect generation|occurrence|production of a power failure in a short time is provided.

Diagram explaining electronic equipment (blackout detection device) Diagram explaining the control circuit Diagram explaining the half-wave detection circuit Diagram for explaining power failure detection processing Diagram for explaining power failure detection processing Diagram for explaining power failure detection processing

<Example 1>
●Electronic equipment (blackout detector)
FIG. 1 shows an electronic device 10. As shown in FIG. The AC power supply 1 is a commercial AC power supply or the like that supplies alternating current. A rectifying/smoothing circuit 2 rectifies and smoothes alternating current to generate a direct current voltage. The first converter 3 is a DCDC converter that converts a first-level DC voltage output from the rectifying/smoothing circuit 2 into a second-level DC voltage Vo. The second converter 4 is a DCDC converter that converts the second level DC voltage Vo output from the first converter 3 into a third level DC voltage Vcc. The control circuit 5 is a circuit operated by being supplied with a DC voltage Vcc. The half-wave detection circuit 6 is a circuit that generates a pulsed detection signal based on the alternating current supplied from the AC power supply 1 . In FIG. 1, the control circuit 5 and the half-wave detection circuit 6 are surrounded by broken lines, and they function as a power failure detection device.

●Control Circuit FIG. 2 shows the control circuit 5 . The CPU 11 is a central processing unit that implements various functions by executing control programs stored in the ROM area of the HDD 13 or memory 12 . Memory 12 also has a RAM area. HDD 13 is a hard disk drive. The timer 14 is a timer that measures time based on the detection signal output by the half-wave detection circuit 6 . A power failure determination unit 15 determines that a power failure has occurred in the AC power supply 1 when the time measured by the timer 14 becomes shorter than the half cycle of the AC power. The save processing unit 16 executes save processing when the power failure determination unit 15 detects a power failure. The saving process is a process of shutting down the electronic device 10 and saving data stored in the RAM area of the memory 12 to a ROM area (eg, flash memory) or to the HDD 13 .

● Half-wave detection circuit FIG. 3A is a circuit diagram of the half-wave detection circuit 6 . The photocoupler 7 has a light emitting diode D1 and a phototransistor Pt. The collector of the phototransistor Pt functions as a detection signal output section and is pulled up by a resistor R1. The emitter of phototransistor Pt is grounded. Therefore, when a current flows through the light emitting diode D1, a current also flows through the phototransistor Pt, and the level of the detection signal becomes low (L level). If no current flows through the light emitting diode D1, no current flows through the phototransistor Pt, and the level of the detection signal becomes high (H level).

The anode of the light emitting diode D1 is connected to the AC power supply 1 through the resistor R2. A cathode of the light emitting diode D1 is connected to the AC power supply 1 through a resistor R4. The base of the PNP type transistor Tr1 is connected through the time constant circuit 8 to the cathode of the light emitting diode D1 and one end of the resistor R4. A collector of the transistor Tr1 is connected to one end of the resistor R2 and the anode of the light emitting diode D1 through the resistor R3. The emitter of the transistor Tr1 is connected to one end of the capacitor C2, the cathode of the diode D2 and the time constant circuit 8. The other end of the capacitor C2 is connected to the AC power supply 1 and the other end of the resistor R4. A resistor R5 of the time constant circuit 8 is connected to the base of the transistor Tr1, the capacitor C1, the cathode of the light emitting diode D1, the anode of the diode D2 and the resistor R4. A current flows through the diode D3 via the resistor R4 when the polarity of the AC power supply 1 becomes negative.

● Period during which current flows through the light emitting diode D1 When the polarity of the alternating current supplied from the alternating current power supply 1 is positive, current flows through the light emitting diode D1. Light from the light emitting diode D1 is incident on the phototransistor Pt, and current flows through the phototransistor Pt. As a result, the logic of the detection signal becomes L level. A voltage proportional to the current flowing through the light emitting diode D1 is generated across the resistor R4. A current flows into the capacitor C2 through the light emitting diode D1 and the diode D2, and the capacitor C2 is charged. The voltage across capacitor C2 (charging voltage) is equal to the voltage across resistor R4. Since the voltage Veb in the opposite direction (the potential of the emitter is lower than the potential of the base) is applied across the emitter and base of the transistor Tr1, the transistor Tr1 is turned off.

●Period in which no current flows through the light emitting diode D1 When the polarity of the alternating current supplied from the alternating current power supply 1 is negative, no current flows through the light emitting diode D1. In this case, light from the light-emitting diode D1 is no longer incident on the phototransistor Pt, and no current flows through the phototransistor Pt. As a result, the logic of the detection signal becomes H level.

When the AC voltage of AC power supply 1 becomes negative, current flows through resistor R4, diode D3 and resistor R2. Therefore, a voltage is generated across the resistor R4 in the opposite direction to the voltage during the period when the current is flowing through the light emitting diode D1. The capacitor C2 remains charged during the period in which the current is flowing through the light emitting diode D1. Therefore, a forward voltage Veb (the potential of the emitter is higher than the potential of the base) is applied between the emitter and the base of the transistor Tr1, and the transistor Tr1 is turned on. Since the transistor Tr1 is on, the electric charge stored in the capacitor C2 is slowly discharged through the path through the transistor Tr1, the resistor R3, and the resistor R2.

●Detection of Power Failure FIG. 4A shows the voltage of the AC power supply 1, the detection signal, the collector current Ic, and the voltage Veb when a power failure occurs while no current is flowing through the light emitting diode D1. When a power failure occurs in the AC power supply 1 at time t7, the voltage across the AC power supply 1 becomes 0V. As a result, the charge discharged from the capacitor C2 via the transistor Tr1 also flows through the path via the transistor Tr1, the resistor R3, the light emitting diode D1, and the resistor R4. Due to the current flowing through the light emitting diode D1, the detection signal transitions from the H level to the L level. The timer 14 counts the time Ta between the timing (transition edge) at which the H level transitions to the L level and the timing at which the L level transitions to the H level. Normally, the time Ta is equal to the alternating half-period Tp. At time t7, the timer 14 detects a transition edge and stops timing. As shown in FIG. 4A, the time Ta is shorter than the AC half-cycle Tp, so the power failure determination unit 15 determines that a power failure has occurred.

FIG. 4B shows the detection voltage levels and the like of the invention described in Patent Document 1. FIG. In the invention described in Patent Document 1, since the detection signal remains at H level after time t7, the time Ta becomes longer than the half cycle Tp. Therefore, the invention described in Patent Document 1 cannot detect a power failure in a time shorter than the half cycle Tp. On the other hand, in Example 1, when a power failure occurs during a period in which no current flows through the light emitting diode D1, current flows through the light emitting diode D1 due to the discharge of the capacitor C2, so the level of the detection signal becomes L level. Therefore, the timer 14 can measure a time Ta shorter than the half cycle Tp.

FIG. 5 shows the voltage of the AC power supply 1, the detection signal, the collector current Ic and the voltage Veb when a power failure occurs while current is flowing through the light emitting diode D1. When a power failure occurs in the AC power supply 1 at time t8, there is no current supply source for the light emitting diode D1. Therefore, no current flows through the light emitting diode D1, and the logic of the detection signal changes from L level to H level. When the current stops flowing through the light emitting diode D1, the voltage across the resistor R4 becomes 0V. Therefore, the emitter-base voltage Veb of the transistor Tr1 changes from the reverse direction to the forward direction, and the transistor Tr1 transitions from the off state to the on state. However, it takes time (time from t8 to t9) due to the time constant of the resistor R5 and the capacitor C1 for the transistor Tr1 to transition from the off state to the on state. Therefore, when a power failure occurs, the detection signal is at H level for a certain period of time. Then, the detection signal becomes L level. Therefore, the timer 14 can measure a time Ta shorter than the half cycle Tp.

<Example 2>
FIG. 3B shows the half-wave detection circuit 6 of the second embodiment. An FET (Field Effect Transistor), which is a switching element, is connected in series with the light emitting diode D1. Therefore, when the FET is turned off, no current flows through the light emitting diode D1. That is, by turning off the FET when a power failure occurs, it is possible to forcibly change the level of the detection signal to the H level.

The anode of light emitting diode D1 is connected to AC power supply 1 via resistor R16, diode D17 and resistor R18. One end of the resistor R16 is connected to the AC power supply 1, and the other end of the resistor R16 is connected to the anode of the diode D17. The cathode of diode D17 is connected to one end of resistor R18. The other end of resistor R18 is connected to the anode of light emitting diode D1. The drain of the FET is connected to the cathode of the light emitting diode D1. A gate of the FET is connected to one end of the AC power supply 1 via a resistor R26. A source of the FET is connected to the other end of the AC power supply 1 . A resistor R25 is connected between the gate and source of the FET. A time constant circuit 8 is connected to the base of the NPN type transistor Tr2. The collector of transistor Tr2 is connected to the cathode of diode D17 and one end of resistor R18. The emitter of transistor Tr2 is connected to the gate of FET, one end of resistor R25, and one end of resistor R26. One end of capacitor C20 is connected to the cathode of diode D17, the collector of transistor Tr2, and one end of resistor R18. The other end of the capacitor C20 is connected to the other end of the AC power supply 1, the source of the FET and the other end of the resistor R25. The anode of diode D19 is connected to the other end of AC power supply 1 . The cathode of diode D19 is connected to the anode of diode D17.

When the voltage of the AC power supply 1 rises, a current flows through the resistor R25 and the voltage between the gate and source of the FET rises. The FET turns on when the gate-to-source voltage of the FET exceeds the on-threshold. As a result, a current flows through the light emitting diode D1, and the detection signal becomes L level. On the other hand, when the voltage of the AC power supply 1 drops and the voltage between the gate and source of the FET falls below the ON threshold, the FET is turned off. As a result, no current flows through the light emitting diode D1, and the detection signal becomes H level.

●Difference between Example 1 and Example 2 In Example 1, the timing at which the logic of the detection signal is inverted is affected by the forward voltage of the light emitting diode D1 and the CTR (conversion efficiency) of the photocoupler 7 . CTR is the ratio of the current flowing through the light emitting diode D1 and the current flowing through the phototransistor Pt. CTR may have an error range of about 100% to 400%. In other words, the variation in CTR is large. On the other hand, the second embodiment employs a circuit configuration in which the gate threshold voltage of the FET is dominant as a parameter that causes timing errors. Therefore, in the second embodiment, the timing at which the voltage of the AC power supply 1 becomes 0 V can be detected with high accuracy as compared with the first embodiment.

●Circuit operation during the period when the FET is ON During the period when the FET is ON, the level of the detection signal becomes L level. Capacitor C20 is charged through resistor R16 and diode D17. Since a reverse voltage (base potential is lower than emitter potential) is applied between the base and emitter of the transistor Tr2, the transistor Tr2 is in an off state.

●Circuit operation during the period when the FET is off On the other hand, during the period when the FET is off, the H level is output as the detection signal voltage. A forward voltage (the potential of the base is higher than the potential of the emitter) is applied across the base and emitter of the transistor Tr2. Therefore, the transistor Tr2 is turned on. Since the transistor Tr2 is on, the electric charge stored in the capacitor C20 is slowly discharged via the transistor Tr2 and the resistor R26.

●Detection of Power Failure FIG. 6A shows the voltage of the AC power supply 1, the detection signal, the collector current Ic, and the voltage Veb when a power failure occurs while the FET is off. When a power failure occurs at time t10, the voltage across the AC power supply 1 becomes 0V. Therefore, the charge discharged from the capacitor C20 also flows through the path via the transistor Tr2 and the resistor R25. Current flow through resistor R25 causes the gate-source voltage of the FET to exceed the on-threshold voltage. Therefore, the FET transitions to the ON state, current flows through the light emitting diode D1, and the detection signal transitions to the L level. A charge is supplied from the capacitor C20 to the light emitting diode D1 through the resistor R18. The timer 14 stops timing in response to the transition of the level of the detection signal from the H level to the L level. Thereby, the timer 14 can detect the time Ta shorter than the half-cycle Tp of the alternating current. Further, the power failure determination unit 15 determines that the power failure has occurred because the time Ta is shorter than the half-cycle Tp of the alternating current.

FIG. 6B shows the voltage of the AC power supply 1, the detection signal, the collector current Ic and the voltage Veb when a power failure occurs while the FET is on. When a power failure occurs at time t11, the voltage of AC power supply 1 becomes 0V. This causes the gate-source voltage of the FET to fall below the on-threshold voltage. As a result, the FET is turned off and no current flows through the light emitting diode D1. The level of the detection signal transitions from L level to H level. When the FET is turned off, the cathode voltage of the light emitting diode D1 rises, so the voltage across the base and emitter of the transistor Tr2 changes from the reverse direction to the forward direction. As a result, the transistor Tr2 transitions from the off state to the on state. However, in order for the transistor Tr2 to transition from the off state to the on state, a time (time from time t11 to time t12) due to the time constant of the resistor R5 and the capacitor C1 is required. Therefore, as shown in FIG. 6B, the detection signal is at H level for a certain period of time when power failure occurs, and then transitions to L level.

The timer 14 stops timing in response to the transition of the level of the detection signal from the L level to the H level. Thereby, the timer 14 can detect the time Ta shorter than the half-cycle Tp of the alternating current. Further, the power failure determination unit 15 determines that the power failure has occurred because the time Ta is shorter than the half-cycle Tp of the alternating current.

<Summary>
The half-wave detection circuit 6 is an example of detection means for outputting a detection signal (eg, L) of the first logic during a period in which the polarity of the AC supplied from the AC power supply 1 is the first polarity (eg, positive). The half-wave detection circuit 6 outputs a second logic detection signal (eg, H) during a period in which the polarity of the AC supplied from the AC power supply 1 is the second polarity (eg, negative) opposite to the first polarity. It is an example of detection means. The timer 14 is an example of a timer that measures the time between the timing when the logic of the detection signal switches from the first logic to the second logic and the timing when the logic of the detection signal switches from the second logic to the first logic. The power failure determination unit 15 is an example of determination means for determining that a power failure has occurred in the AC power supply 1 when the time Ta measured by the timer means becomes shorter than the half-cycle Tp of the AC.

As shown in FIGS. 4(A) and 6(A), the half-wave detection circuit 6, when the supply of alternating current from the AC power supply 1 is interrupted while the detection signal of the second logic is being output, Output the detection signal of the first logic. As shown in FIGS. 5 and 6B, the half-wave detection circuit 6 is temporarily It is configured to output a detection signal of the second logic and then resume outputting the detection signal of the first logic. This makes it possible to detect the occurrence of a power failure in a shorter period of time.

The photocoupler 7 is an example of a signal generation circuit that outputs a detection signal by half-wave rectifying an alternating current. A portion of the half-wave detection circuit 6 excluding the photocoupler 7 and the resistor R1 functions as a control circuit for controlling the signal generation circuit. The supply of alternating current from the alternating current power supply 1 may be interrupted while the signal generation circuit is outputting the detection signal of the second logic. In this case, the control circuit may cause the signal generation circuit to output the detection signal of the first logic. The supply of alternating current from the alternating current power supply 1 may be interrupted while the signal generation circuit is outputting the detection signal of the first logic. In this case, the control circuit may cause the signal generation circuit to temporarily output the detection signal of the second logic, and then restart the output of the detection signal of the first logic.

As shown in FIG. 3A, the light-emitting diode D1 is an example of a rectifying element that allows a current to flow when a voltage of a first polarity is applied and does not flow when a current of a second polarity is applied. The phototransistor Pt and the resistor R1 form an output circuit that outputs a detection signal of the first logic while current flows through the rectifying element and outputs a detection signal of the second logic while current does not flow through the rectifying element. there is The transistor Tr1 has a current outflow terminal, a control terminal, and a current inflow terminal connected to the output side of the rectifier. The transistor Tr<b>1 functions as a current control element that is turned on during a period when the alternating current of the first polarity is supplied from the alternating current power supply 1 and turned off during the period when the alternating current of the second polarity is supplied from the alternating current power supply 1 . The resistor R3 is connected between the input side of the rectifying element and the current outflow terminal of the current control element, and functions as a limiting resistor that limits the current flowing through the current control element. Capacitor C2 is an example of a storage circuit connected to the current input terminal of the current control element, charged during the period when current flows through the rectifying element, and discharged during the period when current does not flow through the rectifying element. The time constant circuit 8 is an example of a time constant circuit connected to the control terminal of the current control element. When the supply of alternating current from the AC power supply 1 is interrupted during the period in which the AC of the second polarity is being supplied from the AC power supply 1, the current due to the discharge of the storage circuit flows through the rectifying element via the current control element and the limiting resistor. . As a result, the output circuit changes the logic of the detection signal from the second logic to the first logic. If the supply of alternating current from the alternating current power supply 1 is interrupted while the alternating current of the first polarity is being supplied from the alternating current power supply 1, the current stops flowing through the rectifying element. As a result, the output circuit changes the logic of the detection signal from the first logic to the second logic. The time constant circuit 8 delays the rise of the voltage applied to the control terminal, so that the current control element is turned on with a delay from the timing when the supply of alternating current from the alternating current power supply 1 is interrupted. As a result, the current due to the discharge of the storage circuit flows through the current control element and the limiting resistor to the rectifying element, and the output circuit changes the logic of the detection signal from the second logic to the first logic.

The phototransistor Pt is an example of a light-receiving element that allows current to flow when the light-emitting diode is lit and does not flow when the light-emitting diode is extinguished. A resistor R1 is an example of a pull-up resistor connected to the output side of the light receiving element.

As shown in FIG. 3B, the signal generation circuit may be composed of a light emitting diode D1, a phototransistor Pt and a resistor R1. Light emitting diode D1 is an example of a first rectifying element. The control circuit can be composed of the following circuit elements. The FET is an example of a switch element arranged so as to be turned on when an alternating current of the first polarity is supplied from the alternating current power supply 1 and turned off when the alternating current of the first polarity is no longer supplied. Capacitor C20 is an example of a storage circuit that is charged during a period in which current flows through the first rectifying element and is discharged during a period in which current does not flow through the first rectifying element. The NPN type transistor Tr2 and the resistor R25 are an example of a resistor and current control element for controlling the control voltage applied to the switch element. The time constant circuit 8 is an example of a time constant circuit connected to the control terminal of the current control element. The supply of alternating current from the alternating current power supply may be interrupted while the alternating current of the first polarity is being supplied from the alternating current power supply. In this case, the output circuit changes the logic of the detection signal from the first logic to the second logic because the current stops flowing through the first rectifying element. The time constant circuit 8 delays the rise of the voltage applied to the control terminal, so that the current control element is turned on with a delay from the timing when the supply of alternating current from the alternating current power supply 1 is interrupted. The switch element is turned on when the current due to the discharge of the storage circuit flows through the resistor R25 via the current control element. As a result, the current generated by the discharge of the storage circuit can flow through the first rectifying element, and the output circuit changes the logic of the detection signal from the second logic to the first logic. Further, the supply of alternating current from the alternating current power supply 1 may be interrupted while the alternating current of the second polarity is being supplied from the alternating current power supply 1 . In this case, the switch element is turned on by the current flowing through the resistor R25 through the current control element due to the discharge of the storage circuit. As a result, a current due to the discharge of the storage circuit flows through the first rectifying element, and the output circuit changes the logic of the detection signal from the second logic to the first logic.

As shown in FIG. 3B, the diode D19 is an example of a second rectifying element that turns on the transistor Tr2 that supplies the current generated by rectifying the alternating current of the second polarity to the collector and base of the transistor Tr2. . In the event of a power failure, current is supplied from the capacitor C20 to turn on the transistor Tr2. One end of the resistor R25 is connected to the current outflow terminal of the current control element and the control terminal of the switch element. When the current control element is turned on, a current flows from the current outflow terminal of the current control element to one end of the resistor R25. As a result, the control voltage applied to the control terminal of the switch element exceeds the threshold voltage, turning on the switch element.

Thus, according to the present invention, the half-wave detection circuit 6 and power failure detection device that can be mounted on the electronic device 10 are provided. A power failure detection device is composed of a control circuit 5 and a half-wave detection circuit 6 . It would also be advantageous if the half-wave detection circuit 6 could be formed from relatively inexpensive circuit elements. In the above embodiment, a low level detection signal is output when the AC voltage is positive, and a high level detection signal is output when the AC voltage is negative. However, the relationship between the polarity of the AC voltage and the logic of the detection signal may be reversed.

DESCRIPTION OF SYMBOLS 1...AC power supply, 5...Control circuit, 6...Half-wave detection circuit, 10...Electronic device, 7...Photocoupler

Claims (12)

A first logic detection signal is output during a period in which the polarity of the alternating current supplied from the alternating current power supply is the first polarity, and the polarity of the alternating current supplied from the alternating current power supply is the second polarity opposite to the first polarity. detection means for outputting a detection signal of the second logic in a certain period;
timer means for measuring the time between the timing at which the logic of the detection signal switches from the first logic to the second logic and the timing at which the logic of the detection signal switches from the second logic to the first logic;
determining means for determining that a power failure has occurred in the AC power supply when the time measured by the time measuring means becomes shorter than the half cycle of the AC power supply;
When the supply of alternating current from the AC power supply is interrupted while the detection signal of the second logic is being output, outputting the detection signal of the first logic,
When the supply of alternating current from the AC power supply is interrupted while the detection signal of the first logic is being output, the detection signal of the second logic is temporarily output, and then the detection of the first logic is performed. A power failure detection device, characterized in that it is configured to restart signal output. The detection means is
a signal generation circuit that outputs the detection signal by half-wave rectifying the alternating current;
When the supply of alternating current from the AC power supply is interrupted while the signal generation circuit is outputting the detection signal of the second logic, causing the signal generation circuit to output the detection signal of the first logic, When the supply of alternating current from the AC power supply is interrupted while the signal generation circuit is outputting the detection signal of the first logic, the signal generation circuit is temporarily caused to output the detection signal of the second logic. 2. A power failure detection device according to claim 1, further comprising a control circuit for restarting output of the detection signal of the first logic. The signal generation circuit is
a rectifying element that causes a current to flow when the voltage of the first polarity is applied and does not flow a current when the current of the second polarity is applied;
an output circuit that outputs the detection signal of the first logic during a period in which a current flows through the rectifying element and outputs the detection signal of the second logic during a period in which the current does not flow through the rectifying element;
The control circuit is
It has a current outflow terminal, a control terminal, and a current inflow terminal connected to the output side of the rectifying element, and is turned on during a period in which the alternating current of the first polarity is supplied from the alternating current power supply. a current control element that is turned off during a period in which the bipolar alternating current is supplied from the alternating current power supply;
a limiting resistor connected between the input side of the rectifying element and the current outflow terminal of the current control element for limiting the current flowing through the current control element;
a storage circuit connected to the current input terminal of the current control element, charged during a period in which current flows through the rectifying element, and discharged during a period in which current does not flow through the rectifying element;
a time constant circuit connected to the control terminal of the current control element;
When the supply of alternating current from the alternating current power supply is cut off during the period in which the alternating current of the second polarity is supplied from the alternating current power supply, the current due to the discharge of the storage circuit flows through the current control element and the limiting resistor. by flowing into the rectifying element, the output circuit changes the logic of the detection signal from the second logic to the first logic,
When the supply of alternating current from the alternating current power supply is cut off during the period in which the alternating current of the first polarity is supplied from the alternating current power supply, current stops flowing through the rectifying element, and the output circuit outputs the detection signal is changed from the first logic to the second logic, and the time constant circuit delays the rise of the voltage applied to the control terminal, thereby interrupting the supply of alternating current from the alternating current power supply. The current control element is turned on with a delay from the timing, and the current due to the discharge of the storage circuit flows through the rectifying element via the current control element and the limiting resistor, so that the output circuit changes the logic of the detection signal. 3. A power failure detecting device according to claim 2, wherein said second logic is changed to said first logic. The rectifying element is a light emitting diode,
The output circuit is
a light-receiving element that conducts current when the light-emitting diode is lit and does not pass current when the light-emitting diode is extinguished;
4. A power failure detecting device according to claim 3, further comprising a pull-up resistor connected to the output side of said light receiving element. 5. A power failure detection device according to claim 3, wherein said current control element is a PNP type transistor. The signal generation circuit is
a first rectifying element that causes a current to flow when the voltage of the first polarity is applied and does not flow a current when the voltage of the second polarity is applied;
an output circuit that outputs the detection signal of the first logic during a period in which a current flows through the first rectifying element and outputs the detection signal of the second logic during a period in which the current does not flow through the first rectifying element. death,
The control circuit is
a switch element arranged to be turned on when the alternating current of the first polarity is supplied from the alternating current power supply and turned off when the alternating current of the first polarity is no longer supplied;
a power storage circuit that is charged during a period in which current flows through the first rectifying element and is discharged during a period in which current does not flow through the first rectifying element;
a resistor and a current control element for controlling the control voltage applied to the switch element;
a time constant circuit connected to a control terminal of the current control element;
When the supply of alternating current from the alternating current power supply is cut off during the period in which the alternating current of the first polarity is supplied from the alternating current power supply, the current stops flowing through the first rectifying element, and the output circuit The logic of the detection signal is changed from the first logic to the second logic, and the time constant circuit delays the rise of the voltage applied to the control terminal, thereby cutting off the supply of alternating current from the alternating current power supply. The current control element is turned on with a delay from the timing at which the storage circuit is discharged, and the current due to the discharge of the storage circuit flows through the resistor through the current control element, thereby turning on the switch element and causing the current due to the discharge of the storage circuit. By passing through the first rectifying element, the output circuit changes the logic of the detection signal from the second logic to the first logic,
When the supply of alternating current from the alternating current power supply is interrupted during the period in which the alternating current of the second polarity is supplied from the alternating current power supply, the current due to the discharge of the storage circuit flows into the resistor via the current control element. The switch element is turned on by the flow, and the current generated by the discharge of the storage circuit flows through the first rectifying element, so that the output circuit changes the logic of the detection signal from the second logic to the first logic. The power failure detection device according to claim 2, characterized in that: 7. The power failure detection device according to claim 6, further comprising a second rectifying element that supplies a current generated by rectifying the alternating current of the second polarity to the current control element. one end of the resistor is connected to a current outflow terminal of the current control element and a control terminal of the switch element;
When the current control element is turned on, a current flows from the current outflow terminal of the current control element to one end of the resistor, so that the control voltage applied to the control terminal of the switch element exceeds a threshold voltage, 8. A power failure detection device according to claim 6, wherein said switch element is turned on. A first logic detection signal is output during a period in which the polarity of the alternating current supplied from the alternating current power supply is the first polarity, and the polarity of the alternating current supplied from the alternating current power supply is the second polarity opposite to the first polarity. A half-wave detection circuit that outputs a detection signal of the second logic in a certain period,
When the supply of alternating current from the AC power supply is interrupted while the detection signal of the second logic is being output, outputting the detection signal of the first logic,
When the supply of alternating current from the AC power supply is interrupted while the detection signal of the first logic is being output, the detection signal of the second logic is temporarily output, and then the detection of the first logic is performed. A half-wave detection circuit characterized by resuming signal output. a signal generation circuit that outputs the detection signal by half-wave rectifying the alternating current;
When the supply of alternating current from the AC power supply is interrupted while the signal generation circuit is outputting the detection signal of the second logic, causing the signal generation circuit to output the detection signal of the first logic, When the supply of alternating current from the AC power supply is interrupted while the signal generation circuit is outputting the detection signal of the first logic, the signal generation circuit is temporarily caused to output the detection signal of the second logic. 10. A half-wave detection circuit according to claim 9, further comprising a control circuit for restarting the output of said first logic detection signal. The signal generation circuit is
a rectifying element that causes a current to flow when the voltage of the first polarity is applied and does not flow a current when the current of the second polarity is applied;
an output circuit that outputs the detection signal of the first logic during a period in which a current flows through the rectifying element and outputs the detection signal of the second logic during a period in which the current does not flow through the rectifying element;
The control circuit is
It has a current outflow terminal, a control terminal, and a current inflow terminal connected to the output side of the rectifying element, and is turned on during a period in which the alternating current of the first polarity is supplied from the alternating current power supply. a current control element that is turned off during a period in which the bipolar alternating current is supplied from the alternating current power supply;
a limiting resistor connected between the input side of the rectifying element and the current outflow terminal of the current control element for limiting the current flowing through the current control element;
a storage circuit connected to the current input terminal of the current control element, charged during a period in which current flows through the rectifying element, and discharged during a period in which current does not flow through the rectifying element;
a time constant circuit connected to the control terminal of the current control element;
When the supply of alternating current from the alternating current power supply is cut off during the period in which the alternating current of the second polarity is supplied from the alternating current power supply, the current due to the discharge of the storage circuit flows through the current control element and the limiting resistor. by flowing into the rectifying element, the output circuit changes the logic of the detection signal from the second logic to the first logic,
When the supply of alternating current from the alternating current power supply is cut off during the period in which the alternating current of the first polarity is supplied from the alternating current power supply, current stops flowing through the rectifying element, and the output circuit outputs the detection signal is changed from the first logic to the second logic, and the time constant circuit delays the rise of the voltage applied to the control terminal, thereby interrupting the supply of alternating current from the alternating current power supply. The current control element is turned on with a delay from the timing, and the current due to the discharge of the storage circuit flows through the rectifying element via the current control element and the limiting resistor, so that the output circuit changes the logic of the detection signal. 11. The half-wave detector circuit of claim 10, wherein said second logic changes to said first logic. The signal generation circuit is
a first rectifying element that causes a current to flow when the voltage of the first polarity is applied and does not flow a current when the voltage of the second polarity is applied;
an output circuit that outputs the detection signal of the first logic during a period in which a current flows through the first rectifying element and outputs the detection signal of the second logic during a period in which the current does not flow through the first rectifying element. death,
The control circuit is
a switch element arranged to be turned on when the alternating current of the first polarity is supplied from the alternating current power supply and turned off when the alternating current of the first polarity is no longer supplied;
a power storage circuit that is charged during a period in which current flows through the first rectifying element and is discharged during a period in which current does not flow through the first rectifying element;
a resistor and a current control element for controlling the control voltage applied to the switch element;
a time constant circuit connected to a control terminal of the current control element;
When the supply of alternating current from the alternating current power supply is cut off during the period in which the alternating current of the first polarity is supplied from the alternating current power supply, the current stops flowing through the first rectifying element, and the output circuit The logic of the detection signal is changed from the first logic to the second logic, and the time constant circuit delays the rise of the voltage applied to the control terminal, thereby cutting off the supply of alternating current from the alternating current power supply. The current control element is turned on with a delay from the timing, and the current due to the discharge of the storage circuit flows through the resistor through the current control element, so that the switch element is turned on and the alternating current of the second polarity is generated. 11. The half-wave detection circuit according to claim 10, wherein the output circuit changes the logic of the detection signal from the second logic to the first logic by causing the current based on the current to flow through the first rectifying element. .

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