A power-down detection circuit

Abstract

This application discloses a power failure detection circuit. The power failure detection circuit includes: an AC power supply, a resistor-capacitor circuit, an optocoupler, a filter circuit, and a controller. The first terminal of the resistor-capacitor circuit is connected to the first terminal of the AC power supply, the second terminal of the resistor-capacitor circuit is connected to the first terminal of the optocoupler, and the second terminal of the optocoupler is connected to the second terminal of the AC power supply. In this embodiment, when the AC power supply fails, the DC blocking characteristic of the capacitor is utilized to ensure that the electrical energy stored in the safety capacitor does not affect the power failure detection. The AC power failure can be detected instantly, improving the reliability of the AC power failure detection. Furthermore, this embodiment utilizes the current-limiting effect of the capacitor, resulting in virtually no power consumption during continuous charging and discharging, thus replacing part of the resistor's function and reducing the power consumption of the AC power failure detection circuit.

Description

Technical Field

[0001] This application relates to the field of detection technology, and in particular to a power-off detection circuit. Background Technology

[0002] In modern life, household appliances have become an indispensable part of people's daily lives. From televisions, refrigerators, and air conditioners to various small appliances, they bring convenience and comfort. However, the energy consumption of these appliances in standby mode is becoming increasingly prominent. Currently, many household appliances continue to consume electricity to maintain standby mode even when they are turned off, as long as the power plug is not unplugged.

[0003] New European regulations on standby power consumption limit 0.50 watts for appliances in off and standby modes, with a further reduction to 0.30 watts by 2027. Given these standby power requirements, managing the power consumption of individual circuit modules within appliances presents a significant challenge. However, in the event of an AC power outage, due to the large capacitance of the capacitors, flyback power supplies can continue operating for an extended period. Even after power is restored, the appliance remains in standby mode and cannot be properly woken up.

[0004] Therefore, it is necessary to detect AC power failure in electrical appliances and then control them to exit standby mode.

[0005] However, electrical appliances typically contain large-capacity safety capacitors in their AC circuits. In the event of an AC power failure, the energy stored in these safety capacitors needs to be discharged before AC power failure detection can be performed, which may result in the inability to detect the AC power failure in a timely manner. Utility Model Content

[0006] To address the aforementioned issues, this application provides a power failure detection circuit that can promptly detect AC power failures in electrical appliances.

[0007] The embodiments of this application disclose the following technical solutions:

[0008] This application provides a power failure detection circuit, including: an AC power supply, a resistor-capacitor circuit, an optocoupler, and a filter circuit;

[0009] The first terminal of the resistor-capacitor circuit is connected to the first terminal of the AC power supply, the second terminal of the resistor-capacitor circuit is connected to the first terminal of the optocoupler, and the second terminal of the optocoupler is connected to the second terminal of the AC power supply.

[0010] The filter circuit filters the output level of the optocoupler. When the AC power supply is normal, the DC power supply terminal, optocoupler, filter circuit and ground form a conductive path, the optocoupler is turned on and the output level of the optocoupler is the first level; when the AC power supply is turned off, the optocoupler is turned off and the output level of the optocoupler is the second level.

[0011] Preferably, the output terminal of the optocoupler is the third terminal, and the filter circuit filters the output level of the optocoupler. The filter circuit includes a second resistor and a second capacitor connected in series between the DC power supply terminal and the ground terminal. The intermediate node of the series connection between the second resistor and the second capacitor is connected to the third terminal of the optocoupler, and the fourth terminal of the optocoupler is grounded.

[0012] When the AC power supply is normal, the DC power supply terminal, the second resistor, the third terminal of the optocoupler, the fourth terminal of the optocoupler and ground form a conductive path. The first level output by the third terminal of the optocoupler is low. When the AC power supply is off, the optocoupler is turned off, and the level output by the third terminal of the optocoupler is the second level, which is high.

[0013] Preferably, the output terminal of the optocoupler is the fourth terminal, and the filter circuit filters the output level of the optocoupler. The filter circuit includes a second resistor and a second capacitor connected in parallel. One end of the second resistor and the second capacitor connected in parallel is connected to the fourth terminal of the optocoupler, and the other end of the second resistor and the second capacitor connected in parallel is grounded.

[0014] When the AC power supply is normal, the DC power supply terminal, the third terminal of the optocoupler, the fourth terminal of the optocoupler, the second resistor and ground form a conductive path, and the first level is output from the fourth terminal of the optocoupler, which is a high level; when the AC power supply is off, the optocoupler is turned off, and the level output from the fourth terminal of the optocoupler is a second level, which is a low level.

[0015] Preferably, the power failure detection circuit further includes: a third resistor; the first end of the third resistor is connected to the second end of the AC power supply, and the second end of the third resistor is connected to the second end of the optocoupler.

[0016] Preferably, the power failure detection circuit further includes a controller, which is connected to the output terminal of the optocoupler and determines whether the AC power supply has failed based on the level status output by the output terminal of the optocoupler.

[0017] Preferably, the power failure detection circuit further includes a controller, which is connected to the third terminal of the optocoupler and determines whether the AC power supply has failed based on the level status output by the third terminal of the optocoupler.

[0018] Preferably, the power failure detection circuit further includes a controller, which is connected to the fourth terminal of the optocoupler and determines whether the AC power supply has failed based on the level status output by the fourth terminal of the optocoupler.

[0019] Preferably, the power failure detection circuit further includes a shaping circuit. The output level of the optocoupler is provided to the shaping circuit, which outputs a shaping signal, which is then provided to the controller.

[0020] Preferably, the power failure detection circuit further includes a shaping circuit. The output level of the optocoupler is filtered by the filter circuit and then provided to the shaping circuit. The shaping circuit outputs a shaping signal, which is then provided to the controller.

[0021] Preferably, the shaping circuit includes: a fourth resistor, a fifth resistor, a sixth resistor, and a metal-oxide-semiconductor field-effect transistor (MOSFET);

[0022] The first end of the fourth resistor is connected to the output of the filter circuit, and the second end of the fourth resistor is connected to the first end of the MOSFET.

[0023] The first end of the fifth resistor is connected to the DC power supply terminal, and the second end of the fifth resistor is connected to the second terminal of the MOSFET and the input terminal of the controller.

[0024] The third terminal of the MOSFET is grounded;

[0025] The first end of the sixth resistor is connected to the first end of the MOSFET, and the second end of the sixth resistor is connected to the third end of the MOSFET.

[0026] Preferably, the optocoupler includes a first light-emitting diode, a second light-emitting diode, and a phototransistor; the first and second light-emitting diodes are connected in reverse parallel between the second terminal of the resistor-capacitor circuit and the second terminal of the AC power supply; the phototransistor receives the photoelectric signals emitted by the first and second light-emitting diodes; the collector of the phototransistor is the third terminal of the optocoupler; and the emitter of the phototransistor is the fourth terminal of the optocoupler.

[0027] Preferably, the power failure detection circuit further includes a safety capacitor, with its two ends connected to the first and second terminals of the AC power supply, respectively. When the AC power supply is in operation, it charges the safety capacitor. When the AC power supply fails, the capacitor in the resistor-capacitor circuit prevents the residual voltage of the safety capacitor from driving the optocoupler.

[0028] Preferably, the resistor-capacitor circuit includes a first resistor and a first capacitor, the first end of the first resistor is connected to the first end of the AC power supply, the second end of the first resistor is connected to the first end of the first capacitor, and the second end of the first capacitor is connected to the first end of the optocoupler.

[0029] Preferably, the resistor-capacitor circuit includes multiple sets of first resistors and first capacitors. The first ends of the multiple sets of first resistors are connected to each other and then connected to the first end of the AC power supply. The second ends of the multiple sets of first resistors are respectively connected to the first ends of the multiple sets of first capacitors. The second ends of the multiple sets of first capacitors are connected to each other and then connected to the first end of the optocoupler.

[0030] Preferably, the resistor-capacitor circuit includes a first equivalent resistor and a first equivalent capacitor. The first end of the first equivalent resistor is connected to the first end of the AC power supply, the second end of the first equivalent resistor is connected to the first end of the first equivalent capacitor, and the second end of the first equivalent capacitor is connected to the first end of the optocoupler.

[0031] Preferably, the first equivalent resistance is a first resistor connected in series, and the first equivalent capacitance is a first capacitor connected in series.

[0032] Preferably, the first equivalent resistance is a first resistor connected in parallel, and the first equivalent capacitance is a first capacitor connected in parallel.

[0033] Because the energy stored in the safety capacitor needs to be discharged before AC power failure detection, the AC power failure may not be detected in time. Therefore, this application provides a power failure detection circuit that connects a resistor-capacitor circuit to the input of an optocoupler. When AC power fails, the DC blocking characteristic of the capacitor in the resistor-capacitor circuit ensures that the energy stored in the safety capacitor does not affect the power failure detection. This eliminates the need to perform power failure detection after the safety capacitor has fully discharged, allowing for instantaneous detection of the AC power failure and improving its reliability. Furthermore, this application embodiment utilizes the current-limiting function of the first capacitor in the resistor-capacitor circuit to replace part of the resistor's function. In this embodiment, the first capacitor in the series-connected resistor-capacitor circuit continuously charges and discharges, consuming virtually no power, thus reducing the power consumption of the power failure detection circuit. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 A schematic diagram of a power-down detection circuit provided in an embodiment of this application;

[0036] Figure 2 A schematic diagram of another power-down detection circuit provided in an embodiment of this application;

[0037] Figure 3A schematic diagram of yet another power-down detection circuit provided in an embodiment of this application;

[0038] Figure 4 A schematic diagram of another power-down detection circuit provided in an embodiment of this application;

[0039] Figure 5 A waveform diagram of a power-down detection circuit provided in an embodiment of this application;

[0040] Figure 6 A schematic diagram of a shaping circuit provided in an embodiment of this application;

[0041] Figure 7 A schematic diagram of yet another power-down detection circuit provided in an embodiment of this application;

[0042] Figure 8 Waveform diagram of another power-down detection circuit provided in the embodiments of this application;

[0043] Figure 9 A resistor-capacitor circuit diagram of a power-down detection circuit provided in an embodiment of this application;

[0044] Figure 10 A resistor-capacitor circuit diagram for another power-down detection circuit provided in this application embodiment;

[0045] Figure 11 A resistor-capacitor circuit diagram for another power-down detection circuit provided in the embodiments of this application;

[0046] Figure 12 A resistor-capacitor circuit diagram for another power-down detection circuit provided in an embodiment of this application. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0048] The terms "first" and "second," etc., used in the specification and claims of this application are used to distinguish different objects, not to describe a specific order of objects. For example, "first switched capacitor" and "second switched capacitor," etc., are used to distinguish different switched capacitors, not to describe a specific order of capacitors.

[0049] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0050] This application does not specifically limit the application scenarios of the power failure detection circuit, such as refrigerators, televisions, and washing machines. For ease of understanding, the application scenarios of this application will be described below using a television as an example.

[0051] In the event of an AC power outage, the flyback power supply can continue operating for an extended period due to the large capacitance of the internal capacitors. Even after power is restored, the TV remains in standby mode and cannot be woken up normally. Therefore, it is necessary to detect AC power outages and control the TV to exit standby mode in such cases. A large-capacity safety capacitor is typically connected to the TV's power input. In related technologies, the stored energy in this safety capacitor needs to be discharged before detecting AC power outages, which may prevent timely detection of the AC power outage.

[0052] Therefore, in this embodiment, a resistor-capacitor circuit is connected in series at the input of the optocoupler. In the event of an AC power failure, the DC blocking characteristic of the capacitor in the resistor-capacitor circuit ensures that the energy stored in the safety capacitor does not affect the power failure detection. This eliminates the need to perform power failure detection only after the safety capacitor has fully discharged, allowing for instantaneous detection of the AC power failure and improving its reliability. Furthermore, this embodiment utilizes the current-limiting effect of the capacitor to replace part of the resistor's function. The series-connected capacitor in this embodiment continuously charges and discharges, consuming virtually no power, thus reducing the power consumption of the AC power failure detection circuit.

[0053] To enable those skilled in the art to understand and implement the technical solutions provided in the embodiments of this application, the structure of the AC power failure detection circuit will be described below in conjunction with the accompanying drawings.

[0054] See Figure 1 The figure is a schematic diagram of a power-down detection circuit provided in an embodiment of this application.

[0055] This application provides a power failure detection circuit, which includes: an AC power supply AC, a resistor-capacitor circuit 100, an optocoupler 200, a filter circuit 300, and a controller 400; the first end of the resistor-capacitor circuit 100 is connected to the first end of the AC power supply AC, the second end of the resistor-capacitor circuit 100 is connected to the first end of the optocoupler 200, and the second end of the optocoupler 200 is connected to the second end of the AC power supply AC.

[0056] At least one output terminal of the optocoupler 200 is electrically connected to the controller 400, and the filter circuit 300 filters the output level of the optocoupler 200. When the AC power supply is normal, the DC power supply terminal VCC, the optocoupler 200, the filter circuit 300, and ground form a conductive path. When the optocoupler 200 is on, the output level of the optocoupler 200 is the first level, which is supplied to the controller 400. When the AC power supply is off, the optocoupler 200 is off, and the output level of the optocoupler 200 is the second level. The controller 400 determines whether the AC power supply is off by checking the output level of the optocoupler 200.

[0057] For example, such as Figure 1 As shown, when the output terminal of the optocoupler 200 is the third terminal, the third terminal of the optocoupler 200 is electrically connected to the controller 400. The filter circuit 300 filters the output level of the optocoupler 200. The filter circuit 300 includes a second resistor R2 and a second capacitor C2 connected in series between the DC power supply terminal VCC and the ground terminal. The intermediate node of the series connection between the second resistor R2 and the second capacitor C2 is connected to the third terminal of the optocoupler 200. The fourth terminal of the optocoupler 200 is grounded.

[0058] When the AC power supply is normal, the DC power supply terminal VCC, the second resistor R2, the third terminal of the optocoupler 200, the fourth terminal of the optocoupler 200, and ground form a conductive path. The first level output by the third terminal of the optocoupler 200 is sent to the controller 400. At this time, the first level is low. When the AC power supply is de-energized, the optocoupler 200 is turned off, and the level output by the third terminal of the optocoupler 200 is the second level. At this time, the second level is high. The controller 400 determines whether the AC power supply is de-energized based on the level status output by the third terminal of the optocoupler 200.

[0059] If the level signal received by the controller 400 is the second level, i.e., high level, it indicates that the AC power supply is off; if the level signal received by the controller 400 is the first level, i.e. low level, it indicates that the AC power supply is working normally.

[0060] For example, such as Figure 2As shown, the output terminal of the optocoupler 200 is the fourth terminal. The fourth terminal of the optocoupler 200 is electrically connected to the controller 400. The filter circuit 300 filters the output level of the optocoupler 200. The filter circuit 300 includes a second resistor R2 and a second capacitor C2 connected in parallel. One end of the second resistor R2 and the second capacitor C2 connected in parallel is connected to the fourth terminal of the optocoupler 200, and the other end of the second resistor R2 and the second capacitor C2 connected in parallel is grounded.

[0061] When the AC power supply is normal, the DC power supply terminal VCC, the third terminal of optocoupler 200, the fourth terminal of optocoupler 200, the second resistor R2 and ground form a conductive path. The first level output by the fourth terminal of optocoupler 200 is sent to the controller 400. At this time, the first level is high. When the AC power supply is de-energized, optocoupler 200 is turned off, and the level output by the fourth terminal of optocoupler 200 is the second level. At this time, the second level is low. The controller 400 determines whether the AC power supply is de-energized based on the level status output by the fourth terminal of optocoupler 200.

[0062] If the level signal received by the controller 400 is the second level, i.e. low level, it indicates that the AC power supply is off; if the level signal received by the controller 400 is the first level, i.e. high level, it indicates that the AC power supply is working normally.

[0063] In addition, such as Figure 3 As shown, the power failure detection circuit described in this embodiment may further include a third resistor R3, the first end of which is connected to the second end of the AC power supply AC, and the second end of which is connected to the second end of the optocoupler 200.

[0064] In this embodiment, the third resistor R3 can limit the spike current generated by residual voltage spikes during power-on / off or lightning surges, protecting the optocoupler from damage while meeting safety requirements. In practical applications, a smaller resistor value can be selected to reduce the power consumption of the AC power-down detection circuit.

[0065] Furthermore, to improve the detection speed of the power failure detection circuit, in the embodiments of this application, such as Figure 4 As shown, a shaping circuit 500 is connected to the output of the filter circuit 300. The output level of the optocoupler 200 is provided to the shaping circuit. The shaping circuit 500 outputs a shaping signal to the controller 400 so that the controller 400 can determine whether the AC power supply has failed based on the shaping signal.

[0066] In one possible implementation, such as Figure 4 As shown, the input terminal of the shaping circuit 500 is connected to the second terminal of the second resistor R2, and the output terminal of the shaping circuit 500 is connected to the input terminal of the controller 400.

[0067] For example, such as Figure 6 As shown, the shaping circuit 500 includes: a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a metal-oxide-semiconductor field-effect transistor Q1; the first end of the fourth resistor R4 is connected to the output terminal of the filter circuit 300, and the second end of the fourth resistor R4 is connected to the first end of the metal-oxide-semiconductor field-effect transistor Q1; the first end of the fifth resistor R5 is connected to the DC power supply terminal VCC, and the second end of the fifth resistor R5 is connected to the second end of the metal-oxide-semiconductor field-effect transistor Q1 and the input terminal of the controller 400; the third end of the metal-oxide-semiconductor field-effect transistor Q1 is grounded; the first end of the sixth resistor R6 is connected to the first end of the metal-oxide-semiconductor field-effect transistor Q1, and the second end of the sixth resistor R6 is connected to the third end of the metal-oxide-semiconductor field-effect transistor Q1.

[0068] To facilitate a better understanding of this solution, embodiments of this application provide, as follows: Figure 5 The signal waveform diagram is shown below. Figure 5 In this diagram, Signal1 represents the output signal of the optocoupler, Signal2 represents the output signal of the shaping circuit, and Signal3 represents the AC signal. It should be understood that when the AC power supply is operating normally (before time t0), the optocoupler is on, Signal1 is low, and Signal2 is low after passing through... Figure 6 The shaping circuit shown becomes high level; after the AC power is lost (at time t0), without the shaping circuit, because the DC power supply terminal VCC charges the second capacitor C2 through the second resistor R2, the level of Signal1 only becomes a high level signal after charging is completed at time t2. That is, the AC power loss can only be detected at time t2, which is much later than the AC power loss at time t0. In this embodiment, the shaping circuit is connected to the back end of the filter circuit. After the AC power is lost (at time t0), under the action of the filter circuit, the level of Signal1 output by the filter circuit rises slowly and triggers the metal-oxide-semiconductor field-effect transistor Q1 to conduct during the rise (for example, at time t1), so that the Signal2 received at the input terminal of the controller is low level, thereby detecting the AC power loss and further improving the speed of power loss detection.

[0069] In this embodiment, the sixth resistor R6 provides a bias voltage for the metal-oxide-semiconductor field-effect transistor Q1, and acts as a discharge resistor to protect the metal-oxide-semiconductor field-effect transistor Q1; the fifth resistor R5 is used to prevent oscillation, reduce the peak gate charging current, and protect the metal-oxide-semiconductor field-effect transistor Q1 from being broken down.

[0070] It should be understood that Figure 6The shaping circuit shown is merely exemplary. In addition, the embodiments of this application can also achieve the shaping of the first signal through comparators and logic chips, which will not be described in detail here.

[0071] In another possible implementation, such as Figure 7 As shown, the input terminal of the shaping circuit 500 is connected to the first terminal of the second resistor R2, the second terminal of the second resistor R2 is grounded, the second capacitor C2 is connected in parallel between the first and second terminals of the second resistor R2, and the output terminal of the shaping circuit 500 is connected to the input terminal of the controller 400.

[0072] To facilitate a better understanding of this solution, embodiments of this application provide, as follows: Figure 8 The signal waveform diagram is shown below. Figure 8 In this diagram, Signal1 represents the output signal of the optocoupler, Signal2 represents the output signal of the shaping circuit, and Signal3 represents the AC signal. It should be understood that after the AC power supply fails, the second capacitor C2 discharges through the second resistor R2. After the discharge is complete at time t2, the level at the first terminal of the second capacitor C2 is a low-level signal. In this embodiment, a shaping circuit is connected to the back end of the filter circuit. After the AC power supply fails (at time t0), under the action of the filter circuit, the level of Signal1 output by the filter circuit slowly decreases and, during the decrease (e.g., at time t1), triggers the metal-oxide-semiconductor field-effect transistor Q1 to turn off, causing Signal2 received at the input terminal of the controller to be at a high level, thereby detecting the AC power failure and further improving the speed of power failure detection.

[0073] It should be understood that the structure and function of the shaping circuit are the same as those in the aforementioned embodiments, and will not be repeated here.

[0074] In addition, the power-down detection circuit described in this application embodiment also includes an optocoupler 200, which includes a first light-emitting diode, a second light-emitting diode, and a phototransistor; the first light-emitting diode and the second light-emitting diode are connected in reverse parallel to the second terminal of the resistor-capacitor circuit 100 and the second terminal of the AC power supply; the phototransistor receives the photoelectric signals emitted by the first light-emitting diode and the second light-emitting diode; the collector of the phototransistor is the third terminal of the optocoupler; and the emitter of the phototransistor is the fourth terminal of the optocoupler.

[0075] In addition, the power-down detection circuit described in this application embodiment also includes a safety capacitor. See again Figure 1 , 23, 4, 7. The two ends of the safety capacitor Cx are connected to the first and second ends of the AC power supply AC. When the AC power supply AC is powered, the AC power supply AC charges the safety capacitor Cx. When the AC power supply AC is powered off, the capacitor in the resistor-capacitor circuit prevents the residual voltage of the safety capacitor from driving the optocoupler 200.

[0076] The resistor-capacitor circuit 100 will be described below.

[0077] In one possible implementation, such as Figure 9 As shown, the resistor-capacitor circuit 100 includes a first resistor R1 and a first capacitor C1 connected in series.

[0078] In one possible implementation, such as Figure 10 As shown, the resistor-capacitor circuit 100 includes n sets of first resistors and first capacitors; for any set of first resistors and first capacitors, for example, the first terminal of the first resistor R11 is connected to the first terminal of the AC power supply AC, the second terminal of the first resistor R11 is connected to the first terminal of the first capacitor C11, and the second terminal of the first capacitor C11 is connected to the first terminal of the optocoupler 200. It should be understood that... Figure 10 In R1n, n is an integer greater than 1, and in C1n, n is an integer greater than 1.

[0079] In one possible implementation, such as Figure 11 and Figure 12 As shown, the resistor-capacitor circuit 100 includes a first equivalent resistor R1x and a first equivalent capacitor C1x. The first end of the first equivalent resistor R1x is connected to the first end of the AC power supply AC, the second end of the first equivalent resistor R1x is connected to the first end of the first equivalent capacitor C1x, and the second end of the first equivalent capacitor C1x is connected to the first end of the optocoupler 200.

[0080] Furthermore, such as Figure 11 As shown, the first equivalent resistance R1x includes multiple resistors connected in series, such as R1_1, R1_2, ..., and R1_n, and the first equivalent capacitance C1x includes multiple capacitors connected in series, such as C1_1, C1_2, ..., and C1_n. It should be understood that the first equivalent resistance R1x can be any one of R11, R12, ..., R1n, and the first equivalent capacitance C1x can be any one of C11, C12, ..., C1n.

[0081] Furthermore, such as Figure 12As shown, the first equivalent resistance R1x includes multiple resistors connected in parallel, and the first equivalent capacitance C1x includes multiple capacitors connected in parallel, such as C1_1, C1_2, ..., and C1_n. It should be understood that the first equivalent resistance R1x can be any one of R11, R12, ..., R1n, and the first equivalent capacitance C1x can be any one of C11, C12, ..., C1n.

[0082] In this embodiment, the first resistor R1 and the first equivalent resistor R1x can limit the peak current generated by residual voltage spikes during power-on / off or lightning surges, protecting the optocoupler 200 from damage while meeting safety requirements. In practical applications, smaller resistance values ​​can be reasonably selected to reduce power consumption, further reducing the power consumption of the AC power-down detection circuit.

[0083] In this application embodiment, the types of the first capacitor C1 and the first equivalent capacitor C1x are not specifically limited. For example, the first capacitor and the first equivalent capacitor C1x can be multilayer ceramic capacitors (MLCCs) to reduce the power consumption of the AC power failure detection circuit.

[0084] In this application embodiment, the type of controller 400 is not specifically limited. For example, the controller can be a microcontroller, a digital signal processor (DSP), or a field-programmable gate array (FPGA) and other control devices.

[0085] When electrical equipment is running, if the AC power supply fails, the equipment will remain in standby mode for a relatively long period of time. During this period, even if the power is restored, the equipment will still remain in standby mode, making it impossible to wake up normally.

[0086] Therefore, based on the aforementioned embodiments, the electrical equipment is equipped with the AC power failure detection circuit described in the aforementioned embodiments. If an AC power failure occurs, the electrical equipment can be controlled to exit standby mode during the power failure, thus ensuring that the electrical equipment is normally woken up the next time it is powered on. Furthermore, in the event of an AC power failure, the power failure detection circuit utilizes the DC blocking characteristic of the capacitor in the resistor-capacitor circuit, ensuring that the electrical energy stored in the safety capacitor does not affect the power failure detection. This eliminates the need to perform power failure detection after the safety capacitor has completely discharged, allowing for instantaneous detection of the AC power failure and improving the reliability of AC power failure detection.

[0087] In addition, in this embodiment, the current limiting effect of the capacitor is used to replace part of the function of the resistor, and the capacitor connected in series in this embodiment is continuously charged and discharged, thereby reducing the power consumption of the AC power failure detection circuit.

[0088] The above description is merely one specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A power down detection circuit, characterized by, include: AC power supply, resistor-capacitor circuit, optocoupler, filter circuit; The first end of the resistor-capacitor circuit is connected to the first end of the AC power supply, the second end of the resistor-capacitor circuit is connected to the first end of the optocoupler, and the second end of the optocoupler is connected to the second end of the AC power supply. The filtering circuit filters the output level of the optocoupler. When the AC power supply is normal, a conductive path is formed between the DC power supply terminal, the optocoupler, the filtering circuit, and ground, and the optocoupler is turned on, with the output level of the optocoupler being the first level. When the AC power supply is turned off, the optocoupler is turned off, with the output level of the optocoupler being the second level.

2. The power failure detection circuit according to claim 1, characterized in that: The output terminal of the optocoupler is the third terminal. The filter circuit filters the output level of the optocoupler. The filter circuit includes a second resistor and a second capacitor connected in series between the DC power supply terminal and the ground terminal. The intermediate node of the series connection between the second resistor and the second capacitor is connected to the third terminal of the optocoupler. The fourth terminal of the optocoupler is grounded. When the AC power supply is in normal operation, the DC power supply terminal, the second resistor, the third terminal of the optocoupler, the fourth terminal of the optocoupler and ground form a conductive path, and the third terminal of the optocoupler outputs a first level, which is a low level; when the AC power supply is de-energized, the optocoupler is turned off, and the third terminal of the optocoupler outputs a second level, which is a high level.

3. The power failure detection circuit according to claim 1, characterized in that: The output terminal of the optocoupler is the fourth terminal. The filter circuit filters the output level of the optocoupler. The filter circuit includes a second resistor and a second capacitor connected in parallel. One end of the second resistor and the second capacitor connected in parallel is connected to the fourth terminal of the optocoupler, and the other end of the second resistor and the second capacitor connected in parallel is grounded. When the AC power supply is in normal operation, the DC power supply terminal, the third terminal of the optocoupler, the fourth terminal of the optocoupler, the second resistor, and ground form a conductive path, and the fourth terminal of the optocoupler outputs a first level, which is a high level; when the AC power supply is de-energized, the optocoupler is turned off, and the fourth terminal of the optocoupler outputs a second level, which is a low level.

4. The power failure detection circuit according to claim 1, characterized in that, Also includes: Third resistor; The first end of the third resistor is connected to the second end of the AC power supply, and the second end of the third resistor is connected to the second end of the optocoupler.

5. The power failure detection circuit according to claim 1, characterized in that, The power failure detection circuit also includes a controller, which is connected to the output terminal of the optocoupler and determines whether the AC power supply has failed based on the level status output by the output terminal of the optocoupler.

6. The power failure detection circuit according to claim 2, characterized in that, The power failure detection circuit also includes a controller, which is connected to the third terminal of the optocoupler and determines whether the AC power supply has failed based on the level output of the third terminal of the optocoupler.

7. The power failure detection circuit according to claim 3, characterized in that, The power failure detection circuit also includes a controller, which is connected to the fourth terminal of the optocoupler and determines whether the AC power supply has failed based on the level output of the fourth terminal of the optocoupler.

8. The power-down detection circuit according to any one of claims 5-7, characterized in that, It also includes a shaping circuit, the level output from the output terminal of the optocoupler is provided to the shaping circuit, the shaping circuit outputs a shaping signal, and the shaping signal is provided to the controller.

9. The power-down detection circuit according to any one of claims 5-7, characterized in that, It also includes a shaping circuit. The level output by the output terminal of the optocoupler is filtered by the filtering circuit and then provided to the shaping circuit. The shaping circuit outputs a shaping signal, which is provided to the controller.

10. The power failure detection circuit according to claim 9, characterized in that, The shaping circuit includes: a fourth resistor, a fifth resistor, a sixth resistor, and a metal-oxide-semiconductor field-effect transistor (MOSFET); The first end of the fourth resistor is connected to the output end of the filter circuit, and the second end of the fourth resistor is connected to the first end of the MOSFET. The first end of the fifth resistor is connected to the DC power supply terminal, and the second end of the fifth resistor is connected to the second terminal of the MOSFET and the input terminal of the controller; The third terminal of the MOSFET is grounded; The first end of the sixth resistor is connected to the first end of the MOSFET, and the second end of the sixth resistor is connected to the third end of the MOSFET.

11. The power failure detection circuit according to claim 1, characterized in that, The optocoupler includes a first light-emitting diode, a second light-emitting diode, and a phototransistor; the first and second light-emitting diodes are connected in reverse parallel between the second terminal of the resistor-capacitor circuit and the second terminal of the AC power supply; the phototransistor receives photoelectric signals emitted by the first and second light-emitting diodes; the collector of the phototransistor is the third terminal of the optocoupler; and the emitter of the phototransistor is the fourth terminal of the optocoupler.

12. The power failure detection circuit according to claim 1, characterized in that, It also includes a safety capacitor, the two ends of which are respectively connected to the first and second ends of the AC power supply. When the AC power supply is powered, it charges the safety capacitor. When the AC power supply is powered off, the capacitor in the resistor-capacitor circuit prevents the residual voltage of the safety capacitor from driving the optocoupler.

13. The power failure detection circuit according to claim 1, characterized in that, The resistor-capacitor circuit includes a first resistor and a first capacitor. The first end of the first resistor is connected to the first end of the AC power supply, the second end of the first resistor is connected to the first end of the first capacitor, and the second end of the first capacitor is connected to the first end of the optocoupler.

14. The power failure detection circuit according to claim 1, characterized in that, The resistor-capacitor circuit includes multiple sets of first resistors and first capacitors. The first ends of the multiple sets of first resistors are connected to each other and then connected to the first end of the AC power supply. The second ends of the multiple sets of first resistors are respectively connected to the first ends of the multiple sets of first capacitors. The second ends of the multiple sets of first capacitors are connected to each other and then connected to the first end of the optocoupler.

15. The power failure detection circuit according to claim 1, characterized in that, The resistor-capacitor circuit includes a first equivalent resistor and a first equivalent capacitor. The first end of the first equivalent resistor is connected to the first end of the AC power supply, the second end of the first equivalent resistor is connected to the first end of the first equivalent capacitor, and the second end of the first equivalent capacitor is connected to the first end of the optocoupler.

16. The power failure detection circuit according to claim 15, characterized in that, The first equivalent resistance is a first resistor connected in series, and the first equivalent capacitance is a first capacitor connected in series.

17. The power failure detection circuit according to claim 15, characterized in that, The first equivalent resistance is a first resistor connected in parallel, and the first equivalent capacitance is a first capacitor connected in parallel.

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