A power supply detection circuit

Abstract

The application relates to the technical field of safe power supply, in particular to a power supply detection circuit, which comprises a power-off detection circuit and a hysteresis comparator circuit; wherein the power-off detection circuit is connected with alternating current and is used for detecting whether power-off of the alternating current occurs; in the case of alternating current power supply, a low level is output, and in the case of alternating current power-off, a high level is output; the hysteresis comparator circuit is connected with the power-off detection circuit and is used for detecting whether power-off occurs due to voltage fluctuation when the alternating current is powered. The application can solve the problem of unstable power-off detection.

Description

Technical Field

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

[0002] Currently, dedicated power failure detection modules are commonly used in the market for power failure detection of circuits. However, these modules suffer from instability in power failure detection when the mains voltage is unstable. Therefore, there is an urgent need for a power supply detection circuit. Summary of the Invention

[0003] Therefore, it is necessary to provide a power detection circuit to address the aforementioned technical problems.

[0004] Firstly, a power supply detection circuit is provided, comprising a power-off detection circuit and a hysteresis comparator circuit; wherein...

[0005] The power failure detection circuit is connected to AC power and is used to detect whether the AC power is interrupted. When the AC power is on, it outputs a low level, and when the AC power is interrupted, it outputs a high level.

[0006] The hysteresis comparator circuit is connected to the power failure detection circuit and is used to detect whether a voltage fluctuation occurs and a power failure occurs when the AC power is supplied.

[0007] As an optional implementation, the power failure detection circuit includes a half-wave rectifier circuit and a voltage signal output circuit; wherein,

[0008] The half-wave rectifier circuit is connected to the AC power and is used to convert the AC power into DC power and filter it.

[0009] The voltage signal output circuit is connected to the half-wave rectifier circuit and is used to detect whether the AC power is interrupted. When the AC power is supplied, it outputs a low level, and when the AC power is interrupted, it outputs a high level.

[0010] As an optional implementation, the half-wave rectifier circuit includes a diode and a capacitor; wherein,

[0011] The input terminal of the diode is connected to the live wire of the AC power, and the output terminal is connected to the first terminal of the capacitor and the voltage signal output circuit, respectively.

[0012] The second terminal of the capacitor is connected to the neutral wire of the AC power supply and the voltage signal output circuit, respectively.

[0013] As an optional implementation, the voltage signal output circuit includes a first resistor, a second resistor, a third resistor, an optocoupler, a first transistor, a second transistor, and a first DC power supply; wherein,

[0014] The first end of the first resistor is connected to the half-wave rectifier circuit, and the second end is connected to the first pin of the optocoupler.

[0015] The second pin of the optocoupler is connected to the neutral line of the AC power supply and the half-wave rectifier circuit, respectively.

[0016] The third pin of the optocoupler is connected to the first terminal of the second resistor and the base of the second transistor, respectively.

[0017] The second end of the second resistor is connected to the first DC power supply;

[0018] The emitter of the first transistor is connected to the first DC power supply, and the base is connected to the collector of the second transistor.

[0019] The first end of the third resistor is connected to the collector of the first transistor and the hysteresis comparator circuit, respectively.

[0020] The fourth pin of the optocoupler, the emitter of the second transistor, and the second terminal of the third resistor are all grounded.

[0021] In one optional implementation, the hysteresis comparator circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a hysteresis comparator, and a second DC power supply; wherein,

[0022] The first end of the fourth resistor is connected to the power failure detection circuit, and the second end is connected to the inverting input of the hysteresis comparator.

[0023] The first end of the fifth resistor is connected to the second DC power supply, and the second end is connected to the first end of the sixth resistor and the non-inverting input of the hysteresis comparator.

[0024] The non-inverting input of the hysteresis comparator is grounded;

[0025] The second end of the sixth resistor is connected to the output of the hysteresis comparator.

[0026] As an optional implementation, the first transistor is a PNP transistor and the second transistor is an NPN transistor.

[0027] As an optional implementation, the first DC power supply is a 5V DC power supply.

[0028] As an optional implementation, the second DC power supply is a 3V DC power supply.

[0029] This application provides a power supply detection circuit, which includes a power outage detection circuit and a hysteresis comparator circuit. The power outage detection circuit is connected to AC power and is used to detect whether the AC power is interrupted. When the AC power is supplied, it outputs a low level; when the AC power is interrupted, it outputs a high level. The hysteresis comparator circuit is connected to the power outage detection circuit and is used to detect whether voltage fluctuations cause a power outage when the AC power is supplied. The technical solution provided by the embodiments of this application has at least the following beneficial effects: when the AC power is interrupted, the power outage detection circuit outputs a high-level voltage signal; when the AC power is supplied normally, the power outage detection circuit outputs a low-level voltage signal. When the voltage fluctuates, the voltage signal output by the power outage detection circuit may be either high or low, leading to inaccurate power outage detection. Therefore, the power supply detection circuit of this application includes a hysteresis comparator circuit. The voltage signal output from the power-off detection circuit is input to the hysteresis comparator circuit. When the voltage signal is higher than the preset upper threshold voltage of the hysteresis comparator, the hysteresis comparator outputs a low level, indicating power failure. When the voltage signal drops to between the preset upper and lower threshold voltages, the hysteresis comparator still outputs a low level, indicating power failure. When the voltage signal drops below the preset lower threshold voltage, the hysteresis comparator flips and outputs a high level, indicating normal power supply. When the voltage signal rises to between the preset upper and lower threshold voltages, the hysteresis comparator still outputs a high level, indicating normal power supply, until the voltage signal rises above the upper threshold voltage, at which point it outputs a low level again, indicating power failure. This solution solves the problem of the detection circuit repeatedly switching between power failure and power supply when the voltage is unstable, providing a buffer area for the voltage signal output by the power failure detection circuit and a margin for judging the normal range of the mains voltage supply.

[0030] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A structural diagram of a power detection circuit provided in an embodiment of this application;

[0033] Figure 2 This is a schematic diagram of a power failure detection circuit provided in an embodiment of this application;

[0034] Figure 3A schematic diagram of a half-wave rectifier circuit provided in an embodiment of this application;

[0035] Figure 4 This is a schematic diagram of a voltage signal output circuit provided in an embodiment of this application;

[0036] Figure 5 A schematic diagram of a hysteresis comparator circuit provided in an embodiment of this application;

[0037] Figure 6 This is a graph illustrating a power outage detection method provided in an embodiment of this application. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0039] The following will describe in detail a power detection circuit provided in the embodiments of this application, with reference to specific implementation methods. Figure 1 A structural diagram of a power detection circuit provided in an embodiment of this application is shown below. Figure 1 As shown, the power supply detection circuit includes a power failure detection circuit 110 and a hysteresis comparator circuit 120; wherein,

[0040] The power failure detection circuit 110 is connected to AC power and is used to detect whether AC power has been interrupted. When AC power is supplied, it outputs a low level, and when AC power is interrupted, it outputs a high level.

[0041] The hysteresis comparator circuit 120 is connected to the power failure detection circuit 110 and is used to detect whether a voltage fluctuation occurs and a power failure occurs when AC power is supplied.

[0042] In implementation, the power supply detection circuit includes a power outage detection circuit 110 and a hysteresis comparator circuit 120, used to detect whether AC power has been interrupted. When AC power is supplied, it outputs a low level; when AC power is interrupted, it outputs a high level. Since AC power fluctuates, it is not stable. The hysteresis comparator circuit 120 provides a margin for judging AC power fluctuations. See details... Figure 5 .

[0043] Optional, Figure 2 This is a schematic diagram of a power failure detection circuit provided in an embodiment of this application, as shown below. Figure 2 As shown, the power failure detection circuit 110 includes a half-wave rectifier circuit 1101 and a voltage signal output circuit 1102; wherein,

[0044] The half-wave rectifier circuit 1101 is connected to AC power and is used to convert AC power to DC power and filter it;

[0045] The voltage signal output circuit 1102 is connected to the half-wave rectifier circuit 1101 and is used to detect whether the AC power is interrupted. When the AC power is on, it outputs a low level, and when the AC power is interrupted, it outputs a high level.

[0046] In implementation, the power failure detection circuit 110 includes a half-wave rectifier circuit 1101 and a voltage signal output circuit 1102. Since this application uses isolated drive, it is necessary to convert AC power to DC power and then filter it. The voltage signal output circuit 1102 is connected to the half-wave rectifier circuit 1101 and is used to detect whether AC power has failed. When AC power is supplied, it outputs a low level; when AC power is failed, it outputs a high level. For details, see [link to detailed process description]. Figure 4 .

[0047] Optional, Figure 3 This application provides a schematic diagram of the structure of a half-wave rectifier circuit, as shown in the embodiment. Figure 3 As shown, the half-wave rectifier circuit 1101 includes a diode D1 and a capacitor C1; wherein,

[0048] The input terminal of diode D1 is connected to the live wire L of AC power, and the output terminal is connected to the first terminal of capacitor C1 and the voltage signal output circuit 1102 respectively.

[0049] The second end of capacitor C1 is connected to the neutral line N of the AC power supply and the voltage signal output circuit 1102.

[0050] In implementation, diode D1 and capacitor C1 form a half-wave rectifier circuit 1101. Diode D1 has unidirectional conductivity, meaning current can only flow into and out of its input terminal, converting alternating current into pulsating direct current. The voltage across capacitor C1 cannot change abruptly, allowing it to store energy and act as a filter.

[0051] Optional, Figure 4 This is a schematic diagram of a voltage signal output circuit provided in an embodiment of this application, as shown below. Figure 4 As shown, the voltage signal output circuit 1102 includes a first resistor R1, a second resistor R2, a third resistor R3, an optocoupler U1, a first transistor Q1, a second transistor Q2, and a first DC power supply DC1; wherein,

[0052] The first end of the first resistor R1 is connected to the half-wave rectifier circuit 1101, and the second end is connected to the first pin W1 of the optocoupler U1.

[0053] The second pin W2 of optocoupler U1 is connected to the neutral line N of AC power and the half-wave rectifier circuit 1101, respectively;

[0054] In implementation, the first resistor R1 acts as a current-limiting resistor, limiting the current in its branch to prevent excessive current from burning out the optocoupler U1 connected in series. When AC power is supplied normally, the AC power is filtered and converted to DC power by a half-wave rectifier circuit. The current flows from the first pin W1 of optocoupler U1 into the LED inside the primary side of optocoupler U1 and flows out from the second pin W2, causing the LED to emit light. When the AC power is off, no current flows through the LED inside the primary side of optocoupler U1, and the LED does not emit light.

[0055] The third pin W3 of the optocoupler is connected to the first terminal of the second resistor R2 and the base b2 of the second transistor Q2, respectively.

[0056] The second end of the second resistor R2 is connected to the first DC power supply DC1.

[0057] The emitter e1 of the first transistor Q1 is connected to the first DC power supply DC1, and the base b1 is connected to the collector c2 of the second transistor Q2.

[0058] The first end of the third resistor R3 is connected to the collector C1 of the first transistor Q1 and the hysteresis comparator circuit 120, respectively.

[0059] The fourth pin W4 of optocoupler U1, the emitter e2 of second transistor Q2, and the second terminal of third resistor R3 are all grounded.

[0060] In implementation, when AC power is supplied normally, the LED inside the primary side of optocoupler U1 emits light, and the secondary side of optocoupler U1 saturates and conducts after sensing the light signal. The first DC power supply DC1 is grounded through the second resistor R2 and the secondary side of optocoupler U1, and both the first transistor Q1 and the second transistor Q2 are cut off. If the voltage at V0 in the diagram is detected, the voltage at V0 is 0V because V0 is grounded through the third resistor R3. When AC power is cut off, the LED inside the primary side of optocoupler U1 does not emit light, and the secondary side of optocoupler U1 is not conducting (cut off). The voltage of the first DC power supply DC1 passes through the second resistor R2 and the base b1 of the second transistor Q2, and the second transistor Q2 saturates and conducts. The voltage drop Vcesat_Q2 between the collector c2 and emitter e2 of the second transistor Q2 is 0V. The voltage of the first DC power supply DC1 passes through the emitter e1 of the first transistor Q1 and the collector c2 of the second transistor Q2. The first transistor Q1 is saturated and conducting, and the voltage drop Vcesat_Q1 between its collector (c1) and emitter (e1) is 0V. If the voltage at point V0 in the diagram is measured, since V0 is connected to the first DC power supply DC1 via the collector (c1) and emitter (e1) of the first transistor Q1, the voltage at V0 is the voltage of the first DC power supply DC1. For example, if the voltage of the first DC power supply DC1 is 5V, then V0 = 5V. Besides normal AC power supply and power outage conditions, AC power also fluctuates. When AC power fluctuates, the secondary side of optocoupler U1 is not saturated and conducting, equivalent to a resistor whose resistance decreases as the current increases. That is, when the AC voltage increases, the resistance of the secondary side of optocoupler U1 decreases, and vice versa. Because the resistance of the secondary side of optocoupler U1 changes when AC power fluctuates, the voltage at V0 jumps between 0V and the voltage of the first DC power supply DC1. In this case, it is impossible to determine whether the AC power is interrupted based on the voltage at V0.

[0061] Optional, Figure 5 A schematic diagram of a hysteresis comparator circuit provided in an embodiment of this application is shown below. Figure 5 As shown, the hysteresis comparator circuit 120 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a hysteresis comparator IC1B, and a second DC power supply DC2; wherein,

[0062] The first terminal of the fourth resistor R4 is connected to the power-off detection circuit 110, and the second terminal is connected to the inverting input V of the hysteresis comparator IC1B. - ;

[0063] The first terminal of the fifth resistor R5 is connected to the second DC power supply DC2, and the second terminal is connected to the first terminal of the sixth resistor R6 and the non-inverting input V of the hysteresis comparator IC1B. + ;

[0064] The non-inverting input V of the hysteresis comparator IC1B + Grounding;

[0065] The second terminal of the sixth resistor R6 is connected to the output terminal V of the hysteresis comparator IC1B. out .

[0066] In implementation, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, and the hysteresis comparator IC1B form a hysteresis comparator circuit to determine the hysteresis abnormality of the voltage at V0. Specifically:

[0067] When AC power is supplied normally, the voltage at V0 is 0V, and the upper threshold voltage V of the hysteresis comparator IC1B is... + _IC1B is:

[0068] V + _IC1B=(V out +DC2)*R5 / (R5+R6)(Formula 1);

[0069] For example: the first DC power supply DC1 has a voltage of 5V, the second DC power supply DC2 has a voltage of 3V, meaning the comparison voltage of the hysteresis comparator IC1B is 3V, and the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 are all 1KΩ. When the voltage at V0 is 0V, that is, when the voltage at the inverting input V of the hysteresis comparator IC1B is V... - The voltage is 0V, which is less than the comparison voltage of the hysteresis comparator IC1B. Therefore, the output voltage V of the hysteresis comparator IC1B is... out The signal transitions from low to high, i.e., V out =5V. V out Substituting 5V into Formula 1, we get V + IC1B = (5+3)*1000 / (1000+1000) = 4V. That is, the upper threshold voltage of the hysteresis comparator IC1B is 4V.

[0070] When the AC power is off, the voltage at V0 is 5V, and the lower threshold voltage V of the hysteresis comparator IC1B is... + _IC1B is:

[0071] V + _IC1B=(DC2-V out )*R5 / (R5+R6)(Formula 2);

[0072] For example: the first DC power supply DC1 has a voltage of 5V, the second DC power supply DC2 has a voltage of 3V, meaning the comparison voltage of the hysteresis comparator IC1B is 3V, and the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 are all 1KΩ. When the voltage at V0 is 5V, that is, when the voltage at the inverting input V0 of the hysteresis comparator IC1B is V0... - The voltage is 5V, which is greater than the comparison voltage of the hysteresis comparator IC1B. Therefore, the output voltage V of the hysteresis comparator IC1B is...out The voltage level changes from high to low, i.e., V out =0V. V out Substituting 0V into Formula 2, we get V+_IC1B = (3-0)*1000 / (1000+1000) = 1.5V. That is, the lower threshold voltage of the hysteresis comparator IC1B is 1.5V. When AC power fluctuates under normal supply conditions, if the voltage at V0 is detected to be between the upper and lower threshold voltages of the hysteresis comparator IC1B, then the AC power supply is considered normal. If the voltage at V0 is detected to be lower than the threshold voltage, then the AC power supply is considered to be interrupted. If, after the AC power supply is interrupted, fluctuations occur again, and the voltage at V0 is detected to be between the upper and lower threshold voltages of the hysteresis comparator IC1B, then the AC power supply is still considered interrupted. If the voltage at V0 is detected to be higher than the upper threshold voltage of the hysteresis comparator IC1B, then the AC power supply is considered to be normal. Figure 6 A power failure detection curve is provided for an embodiment of this application, such as... Figure 6 As shown, for example, the AC mains voltage fluctuates normally between 180V and 230V, with an upper threshold voltage of 4V and a lower threshold voltage of 1.5V. When the AC voltage is below 180V, the voltage detected at V0 is 5V. In curve 1, the output voltage V of the hysteresis comparator IC1B can be determined. out =0V indicates power failure. When the AC point voltage fluctuates to 200V, if the voltage at V0 is 2V, the output voltage V of the hysteresis comparator IC1B can be determined in curve 1. out =0V indicates that the AC power is still off. When the AC point voltage fluctuates to 230V, the voltage at V0 is 0V. In curve 2, the output voltage V of the hysteresis comparator IC1B can be determined. out =5V indicates normal power supply. When the AC point voltage fluctuates to 200V, the voltage at V0 is 2V. In curve 2, the output voltage V of the hysteresis comparator IC1B can be determined. out =5V indicates that the power supply is still normal. When the AC voltage fluctuates below 180V, the voltage at V0 is detected to be 5V. In curve 1, the output voltage V of the hysteresis comparator IC1B can be determined. out =0V indicates that the AC power is off.

[0073] As an optional implementation, the first transistor is a PNP transistor and the second transistor is an NPN transistor.

[0074] In implementation, the first transistor is a PNP transistor, specifically the SS8550, and the second transistor is an NPN transistor, specifically the SS8050.

[0075] As an optional implementation, the first DC power supply is a 5V DC power supply.

[0076] As an optional implementation, the second DC power supply is a 3V DC power supply.

[0077] This application provides a power supply detection circuit, which includes a power outage detection circuit and a hysteresis comparator circuit. The power outage detection circuit is connected to AC power and is used to detect whether AC power is interrupted. It outputs a low level when AC power is supplied and a high level when AC power is interrupted. The hysteresis comparator circuit is connected to the power outage detection circuit and is used to detect whether voltage fluctuations cause a power outage during AC power supply. The technical solution provided by this application provides at least the following advantages: when AC power is interrupted, the power outage detection circuit outputs a high-level voltage signal; when AC power is supplied normally, the power outage detection circuit outputs a low-level voltage signal. When voltage fluctuates, the voltage signal output by the power outage detection circuit may be either high or low, leading to inaccurate power outage detection. Therefore, the power supply detection circuit of this application includes a hysteresis comparator circuit. The voltage signal output from the power-off detection circuit is input to the hysteresis comparator circuit. When the voltage signal is higher than the preset upper threshold voltage of the hysteresis comparator, the hysteresis comparator outputs a low level, indicating power failure. When the voltage signal drops to between the preset upper and lower threshold voltages, the hysteresis comparator still outputs a low level, indicating power failure. When the voltage signal drops below the preset lower threshold voltage, the hysteresis comparator flips and outputs a high level, indicating normal power supply. When the voltage signal rises to between the preset upper and lower threshold voltages, the hysteresis comparator still outputs a high level, indicating normal power supply, until the voltage signal rises above the upper threshold voltage, at which point it outputs a low level again, indicating power failure. This solution solves the problem of the detection circuit repeatedly switching between power failure and power supply when the voltage is unstable, providing a buffer area for the voltage signal output by the power failure detection circuit and a margin for judging the normal range of the mains voltage supply.

[0078] It is understood that the same / similar parts between the various embodiments of the methods described above in this specification can be referred to each other. Each embodiment focuses on the differences from other embodiments, and relevant parts can be referred to the description of other method embodiments.

[0079] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0080] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0081] It should also be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for display, data used for analysis, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0082] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A power supply detection circuit, characterized by comprising: The power supply detection circuit comprises a power-off detection circuit and a hysteresis comparator circuit; wherein, The power-off detection circuit is connected with the alternating current, and is configured to detect whether the alternating current is powered off, output a low level when the alternating current is powered on, and output a high level when the alternating current is powered off; The hysteresis comparator circuit is connected with the power-off detection circuit, and is configured to detect whether the alternating current is powered off when the alternating current is powered on; The hysteresis comparator circuit comprises a fourth resistor, a fifth resistor, a sixth resistor, a hysteresis comparator, and a second direct current power supply; wherein, The first end of the fourth resistor is connected with the power-off detection circuit, and the second end is connected with the inverting input end of the hysteresis comparator; The first end of the fifth resistor is connected with the second direct current power supply, and the second end is connected with the first end of the sixth resistor and the non-inverting input end of the hysteresis comparator respectively; The non-inverting input end of the hysteresis comparator is grounded; The second end of the sixth resistor is connected with the output end of the hysteresis comparator.

2. The circuit of claim 1, wherein, The power-off detection circuit comprises a half-wave rectification circuit and a voltage signal output circuit; wherein, The half-wave rectification circuit is connected with the alternating current, and is configured to convert the alternating current into direct current and filter; The voltage signal output circuit is connected with the half-wave rectification circuit, and is configured to detect whether the alternating current is powered off, output a low level when the alternating current is powered on, and output a high level when the alternating current is powered off.

3. The circuit of claim 2, wherein, The half-wave rectification circuit comprises a diode and a capacitor; wherein, The input end of the diode is connected with the live wire of the alternating current, and the output end is connected with the first end of the capacitor and the voltage signal output circuit respectively; The second end of the capacitor is connected with the neutral wire of the alternating current and the voltage signal output circuit respectively.

4. The circuit of claim 2, wherein, The voltage signal output circuit comprises a first resistor, a second resistor, a third resistor, an optocoupler, a first triode, a second triode, and a first direct current power supply; wherein, The first end of the first resistor is connected with the half-wave rectification circuit, and the second end is connected with the first pin of the optocoupler; The second pin of the optocoupler is connected with the neutral wire of the alternating current and the half-wave rectification circuit respectively; The third pin of the optocoupler is connected with the first end of the second resistor and the base of the second triode respectively; The second end of the second resistor is connected with the first direct current power supply; The emitter of the first triode is connected with the first direct current power supply, and the base is connected with the collector of the second triode; The first end of the third resistor is connected with the collector of the first triode and the hysteresis comparator circuit respectively; The fourth pin of the optocoupler, the emitter of the second triode, and the second end of the third resistor are grounded.

5. The circuit of claim 4, wherein, The first triode is a PNP type triode, and the second triode is an NPN type triode.

6. The circuit of claim 4, wherein, The first direct current power supply is a 5V direct current power supply.

7. The circuit of claim 1, wherein, The second direct current power supply is a 3V direct current power supply.

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