A power failure detection and protection circuit

Abstract

The present invention provides a power-off detection and protection circuit, comprising: a 24V switching power supply, a DC / DC conversion circuit, a first linear voltage stabilizing circuit, a CPU, an energy storage circuit, a charging circuit, a switch circuit, a power-off detection circuit, and a second linear voltage stabilizing circuit. The DC / DC conversion circuit is connected to the 24V switching power supply, the 24V switching power supply and the first linear voltage stabilizing circuit are both connected to the DC / DC conversion circuit, the CPU and the charging circuit are both connected to the first linear voltage stabilizing circuit, the charging circuit and the switch circuit are both connected to the energy storage circuit, the switch circuit is connected to the CPU, the power-off detection circuit and the 24V switching power supply are both connected to the CPU, and the second linear voltage stabilizing circuit is connected to the power-off detection circuit. The present invention provides a power-off detection and protection circuit, which can well solve the problem that the single-chip microcomputer or CPU cannot work normally because the circuit does not have the function of power-off detection and cannot notify the single-chip microcomputer or CPU to shut down normally, thereby causing the single-chip microcomputer or CPU to fail to work normally.

Description

Technical Field

[0001] The invention relates to the field of power conversion, and in particular to a power failure detection and protection circuit. Background Art

[0002] At present, the power-off circuit on the market is that the main power supply VCC is divided into two paths, one path supplies power to the microcontroller or CPU, and the other path charges the battery through a current-limiting resistor. When the main power supply VCC is lost, the battery supplies power to the microcontroller or CPU. However, this circuit structure does not include the function of power-off detection. Since the circuit does not include the function of power-off detection, when the battery power is exhausted, it will still face the problem of power failure. For example, power failure will cause the microcontroller or CPU program to "fly away", thereby causing the microcontroller or CPU to not work normally. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a power failure detection and protection circuit, which can effectively solve the problem that the single-chip microcomputer or CPU cannot be notified to shut down normally because the circuit has no power failure detection function, thereby causing the single-chip microcomputer or CPU to fail to work normally.

[0004] A power-off detection and protection circuit according to the present invention includes: a 24V switching power supply, which is used to power the circuit; a DC / DC conversion circuit, which is connected to the 24V switching power supply; a first linear voltage stabilizing circuit, which is connected to the DC / DC conversion circuit; a CPU, which is connected to the first linear voltage stabilizing circuit; a charging circuit, which is connected to the charging circuit for the first linear voltage stabilizing circuit and the energy storage circuit; an energy storage circuit, which is used to power the CPU when the 24V switching power supply stops supplying power, and the energy storage circuit is connected to the charging circuit; a switching circuit, which is connected to the switching circuit for the energy storage circuit and the CPU; a power-off detection circuit, which is connected to the 24V switching power supply and the CPU; and a second linear voltage stabilizing circuit, which is connected to the power-off detection circuit.

[0005] A power-off detection and protection circuit according to the present invention has at least the following beneficial effects: the circuit adds a power-off detection circuit, and the power-off detection circuit has a power-off detection function, which can monitor the input power supply at any time and inform the CPU to avoid the CPU program "flying alone", and ensure that the CPU can work normally after power is restored.

[0006] According to some embodiments of the present invention, the energy storage circuit also includes a fast charging detection circuit and a fast charging indication circuit, and the fast charging detection circuit is connected to the charging circuit; the charging circuit and the fast charging detection circuit are both connected to the fast charging indication circuit.

[0007] According to some embodiments of the present invention, the DC / DC conversion circuit includes: a fuse, a first inductor, a second inductor, a first resistor, a second resistor, a third resistor, a first capacitor, a first diode, and a 7V buck chip. The 24V switching power supply is connected to one end of the fuse, the other end of the fuse is connected to one end of the first inductor, the other end of the first inductor is connected to the input end of the 7V buck chip, the 24V switching power supply is connected to one end of the first resistor, the other end of the first resistor is connected to the enable end of the 7V buck chip, the guide end of the 7V buck chip is connected to one end of the first capacitor, the PH end of the 7V buck chip, the negative electrode of the first diode and one end of the second inductor are all connected to the other end of the first capacitor, the other end of the second inductor is connected to one end of the second resistor, the other end of the second resistor and one end of the third resistor are all connected to the auxiliary voltage monitoring input end of the 7V buck chip, and the positive electrode of the first diode is connected to the other end of the second resistor.

[0008] According to some embodiments of the present invention, the first linear voltage stabilization circuit includes: a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, and a 5V step-down chip, one end of the second capacitor, one end of the third capacitor, one end of the fourth capacitor, and one end of the fifth capacitor are all connected to the 5V step-down chip, and the other end of the second capacitor, the other end of the third capacitor, and the other end of the fourth capacitor are all connected to the other end of the fifth capacitor.

[0009] According to some embodiments of the present invention, the power-off detection circuit includes: a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a second diode, an input buffer, and a comparator, one end of the fourth resistor is connected to the 24V switching power supply, one end of the fifth resistor and the other end of the fourth resistor are both connected to the positive input of the comparator, one end of the sixth resistor is connected to the first linear voltage regulator circuit, the other end of the sixth resistor and the cathode of the second diode are both connected to the negative input of the comparator, the anode of the second diode is grounded, the output of the comparator, one end of the seventh resistor and the A input of the output buffer are all connected to the B input of the output buffer, the other end of the seventh resistor is connected to the second linear voltage regulator circuit, and the output of the output buffer is connected to the CPU.

[0010] According to some embodiments of the present invention, the second linear voltage stabilization circuit includes: an eighth resistor, a sixth capacitor, a seventh capacitor, an eighth capacitor, and a 3.3V step-down chip, one end of the eighth resistor, one end of the sixth capacitor, and one end of the seventh capacitor are all connected to the input end of the 3.3V step-down chip, the other end of the eighth resistor, the other end of the sixth capacitor, the other end of the seventh capacitor, and the ground end of the 3.3V step-down chip are all grounded, the output end of the 3.3V step-down chip and one end of the eighth capacitor are both connected to the power-off detection circuit, and the other end of the eighth capacitor is grounded.

[0011] According to some embodiments of the present invention, the energy storage circuit includes: a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a supercapacitor, a first relay, a second relay, a third relay, a third diode, a fourth diode, a fifth diode, and a field effect transistor. One end of the ninth resistor, the normally open point of the first relay, the negative electrode of the third diode, the normally open point of the second relay, the negative electrode of the fourth diode and the normally open point of the third relay are all connected to the first linear voltage stabilization circuit, the other end of the ninth resistor, one end of the supercapacitor and one end of the tenth resistor are all connected to the moving contact of the first relay, the other end of the supercapacitor is grounded, the other end of the tenth resistor, the eleventh resistor and the positive electrode of the third diode are all connected to the gate of the field effect transistor, the moving contact of the second relay, the positive electrode of the fourth diode and the negative electrode of the fifth diode are all connected to the drain of the field effect transistor, the source of the field effect transistor is grounded, the moving contact of the third relay is connected to one end of the twelfth resistor, and the other end of the twelfth resistor is connected to the positive electrode of the fifth diode.

[0012] According to some embodiments of the present invention, the second linear voltage regulator circuit provides an operating voltage to the input buffer in the power-off detection circuit and provides a pull-up voltage to the comparator U4 in the power-off detection circuit.

[0013] According to some embodiments of the present invention, when the 24V switching power supply operates normally, the comparator outputs a high level, and the output buffer outputs a high level to the CPU; when the 24V switching power supply is powered off, the comparator outputs a low level, and the output buffer outputs a low level to the CPU.

[0014] According to some embodiments of the present invention, the model of the field effect tube is 2N7002, and the model of the super capacitor is CHP5R5L255R-DA.

[0015] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 A principle block diagram of a power failure detection and protection circuit according to an embodiment of the present invention;

[0018] Figure 2 A circuit schematic diagram of a DC / DC conversion circuit of a power failure detection and protection circuit according to an embodiment of the present invention;

[0019] Figure 3 A circuit schematic diagram of a first linear voltage stabilizing circuit of a power failure detection and protection circuit according to an embodiment of the present invention;

[0020] Figure 4 A circuit schematic diagram of a power-off detection circuit of a power-off detection and protection circuit according to an embodiment of the present invention;

[0021] Figure 5 A circuit schematic diagram of a second linear voltage stabilizing circuit of a power-off detection and protection circuit according to an embodiment of the present invention;

[0022] Figure 6 The present invention is a schematic circuit diagram of an energy storage circuit of a power failure detection and protection circuit according to an embodiment of the present invention.

[0023] Reference numerals:

[0024] 24V switching power supply 100, DC / DC conversion circuit 101, first linear voltage regulator circuit 102, CPU 104, energy storage circuit 109, charging circuit 105, switch circuit 108, power failure detection circuit 103, second linear voltage regulator circuit 107, fast charging detection circuit 110, fast charging indication circuit 106,

[0025] Fuse FU1, first inductor L1, second inductor L2, first resistor R1, second resistor R4, third resistor R5, first capacitor C7, first diode D1, 7V step-down chip U1, second capacitor C10, third capacitor C11, fourth capacitor C12, fifth capacitor C13, 5V step-down chip U2, fourth resistor R6, fifth resistor R7, sixth resistor R8, seventh resistor R9, second diode D2, input buffer U3, comparator U4, eighth resistor C10, sixth capacitor C15, seventh capacitor C16, eighth capacitor C17, 3.3V step-down chip U6, ninth resistor R11, tenth resistor R12, eleventh resistor R13, twelfth resistor R14, super capacitor C18, first relay K1, second relay K2, third relay K3, third diode D3, fourth diode D4, fifth diode D5, field effect transistor Q1. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0027] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0028] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0029] Reference Figure 1 , a power-off detection and protection circuit according to the present invention comprises:

[0030] A 24V switching power supply 100 is used to supply power to the circuit; a DC / DC conversion circuit 101 is used to convert a 24V voltage into a 7V voltage, and the DC / DC conversion circuit 101 is connected to the 24V switching power supply 100; a first linear voltage regulator circuit 102 is used to convert a 7V voltage into a 5V voltage, and the first linear voltage regulator circuit 102 is connected to the DC / DC conversion circuit 101; a CPU 104 is connected to the first linear voltage regulator circuit 102; an energy storage circuit 109 is used to supply power to the CPU 104 when the 24V switching power supply 100 stops supplying power; a charging circuit 105 is used to charge the energy storage circuit 109, and the charging circuit 105 has two charging modes, namely positive and negative charging. In the normal charging mode and the fast charging mode, the charging circuit 105 is connected to the first linear voltage regulator circuit 102, and the charging circuit 105 is connected to the energy storage circuit 109; the switch circuit 108 is used to control whether the energy storage circuit 109 supplies power to the CPU 104, the switch circuit 108 is connected to the energy storage circuit 109, and the switch circuit 108 is connected to the CPU 104; the power-off detection circuit 103 is used to detect whether the 24V switching power supply 100 is powered off, the power-off detection circuit 103 is connected to the 24V switching power supply 100, and the power-off detection circuit 103 is connected to the CPU 104; the second linear voltage regulator circuit 107, the second linear voltage regulator circuit 107 is connected to the power-off detection circuit 103.

[0031] In this embodiment, the power-off detection circuit 103 is connected to the CPU 104. The power-off detection circuit 103 has the function of detecting whether the 24V switching power supply 100 is powered off. When the power-off detection circuit detects that the 24V switching power supply is powered off, it will issue a power-off command to the CPU, so that the CPU can shut down normally before the power in the energy storage circuit is exhausted, avoiding the CPU program "flying alone" and ensuring that the CPU can work normally after power is restored.

[0032] Furthermore, the energy storage circuit 109 also includes a fast charging detection circuit 110 and a fast charging indication circuit 106. The fast charging detection circuit 110 is used to detect whether the energy storage circuit 109 meets the conditions for starting the fast charging mode, and the fast charging detection circuit 110 is connected to the charging circuit 105; the fast charging indication circuit 106 is used to display whether the energy storage circuit 109 is in the fast charging mode, and the charging circuit 105 and the fast charging detection circuit 110 are both connected to the fast charging indication circuit 106.

[0033] In this embodiment, the fast charging detection circuit 110 is used to detect whether the energy storage circuit 109 meets the conditions for starting the fast charging mode. When the energy storage circuit 109 meets the conditions, the energy storage circuit 109 will start the fast charging mode. The fast charging mode will greatly improve the energy storage efficiency of the energy storage circuit 109, so that the charging circuit 105 can fully charge the power storage device of the energy storage circuit 109 in a short time, and the fast charging indication circuit 106 is used to display whether the energy storage circuit 109 is in the fast charging mode. When the energy storage circuit 109 is in the fast charging mode, the fast charging indication circuit 106 will prompt the user that the energy storage circuit 109 is in the fast charging mode, so that the user can clearly understand that the circuit has taken effect.

[0034] Reference Figure 2 According to a power-off detection and protection circuit of the present invention, the DC / DC conversion circuit 101 includes:

[0035] The fuse FU1, the first inductor L1, the second inductor L2, the first resistor R1, the second resistor R4, the third resistor R5, the first capacitor C7, the first diode D1, the 7V buck chip U1, and the 24V switching power supply are connected to one end of the fuse FU1, the other end of the fuse FU1 is connected to one end of the first inductor L1, the other end of the first inductor L1 is connected to the input end of the 7V buck chip U1, the 24V switching power supply is connected to one end of the first resistor L1, and the other end of the first resistor L1 is connected to the 7V buck chip The enable end of U1 is connected, the guide end of the 7V buck chip U1 is connected to one end of the first capacitor C7, the PH end of the 7V buck chip, the cathode of the first diode D1 and one end of the second inductor L2 are all connected to the other end of the first capacitor C7, the other end of the second inductor L2 is connected to one end of the second resistor R4, the other end of the second resistor R4 and one end of the third resistor R5 are all connected to the auxiliary voltage monitoring input end of the 7V buck chip U1, and the anode of the first diode D1 is connected to the other end of the second resistor R5.

[0036] In this embodiment, the 24V voltage is converted into a 7V voltage through the 7V step-down chip U1, preparing for the subsequent reduction from 7V to 5V. In the step-down circuit, if the voltage reduction is too large, the power loss will increase. Stepping down the voltage in multiple times can reduce the power loss.

[0037] Furthermore, the model of the 7V step-down chip U1 is TPS54232.

[0038] In this embodiment, the 7V step-down chip U1 of this model has overheating and overvoltage transient protection, and adopts easy-to-use 8-pin small outline integrated circuit (SOIC) PowerPAD and 10-pin small outline no-lead (SON) packages, which can ensure the safety of the circuit and reduce the installation volume of the circuit.

[0039] Reference Figure 3 According to a power-off detection and protection circuit of the present invention, the first linear voltage regulator circuit 102 includes:

[0040] The second capacitor C10, the third capacitor C11, the fourth capacitor C12, the fifth capacitor C13, the 5V step-down chip U2, one end of the second capacitor C10, one end of the third capacitor C11, one end of the fourth capacitor C12 and one end of the fifth capacitor C13 are all connected to the 5V step-down chip U2, and the other end of the second capacitor C10, the other end of the third capacitor C11 and the other end of the fourth capacitor C12 are all connected to the other end of the fifth capacitor C13.

[0041] In this embodiment, the first linear voltage regulator circuit 102 steps down the voltage of 7V to a working voltage of 5V, which is just enough for use by other modules in the circuit. Moreover, the voltage is stepped down from 7V, and the voltage reduction is not large, which can reduce power loss during the conversion process.

[0042] Reference Figure 4 According to a power failure detection and protection circuit of the present invention, the power failure detection circuit 103 includes:

[0043] The fourth resistor R6, the fifth resistor R7, the sixth resistor R8, the seventh resistor R9, the second diode D2, the input buffer U3, and the comparator U4, one end of the fourth resistor R6 is connected to the 24V switching power supply, one end of the fifth resistor R7 and the other end of the fourth resistor R6 are both connected to the positive input end of the comparator U4, one end of the sixth resistor R8 is connected to the first linear voltage stabilization circuit, the other end of the sixth resistor R8 and the cathode of the second diode D2 are both connected to the negative input end of the comparator U4, the anode of the second diode D2 is grounded, the output end of the comparator U4, one end of the seventh resistor R9 and the A input end of the output buffer U3 are all connected to the B input end of the output buffer U3, the other end of the seventh resistor R9 is connected to the second linear voltage stabilization circuit, and the output end of the output buffer U3 is connected to the CPU.

[0044] In this embodiment, the switching power supply 24V passes through the fourth resistor R6 and the fifth resistor R7 to provide a 3.6V bias voltage to the positive input terminal of the comparator U4, the voltage of the first linear voltage regulator circuit passes through the sixth resistor R8 and the second diode D2 to provide a 3.3V bias voltage to the negative input terminal of the comparator U4, the voltage of the second linear voltage regulator circuit passes through the seventh resistor R9 to provide a pull-up voltage to the output terminal of the comparator U4, the second linear voltage regulator circuit is connected to the VCC terminal of the output buffer U3, and provides a working voltage to the output buffer U3, so that the output high level of the input buffer is 3.3V.

[0045] Furthermore, the power-off detection circuit 103 has a power-off detection function.

[0046] In this embodiment, when the 24V switching power supply is working normally, the comparator U4 outputs a high level and the output buffer U3 also outputs a high level. When the 24V switching power supply is powered off, the 3.6V bias voltage provided by the switching power supply 24V to the positive input terminal of the comparator U4 through the fourth resistor R6 and the fifth resistor R7 will become 0, and the comparator U4 will output a low level, thereby causing the output buffer U3 to output a low level, thereby giving the CPU a low level, reminding the CPU that the power is currently off, thereby protecting the CPU.

[0047] Further, the model of the input buffer U3 is 74HCIG08DFT1G.

[0048] In this embodiment, this type of input buffer can meet the voltage required by the CPU, and its delay time is shorter than that of an input buffer with the same requirements, and the noise of the external signal can be filtered out.

[0049] Reference Figure 5 According to a power-off detection and protection circuit of the present invention, the second linear voltage stabilization circuit 107 includes:

[0050] The eighth resistor C10, the sixth capacitor C15, the seventh capacitor C16, the eighth capacitor C17, and the 3.3V step-down chip, one end of the eighth resistor C10, one end of the sixth capacitor C15, and one end of the seventh capacitor C16 are all connected to the input end of the 3.3V step-down chip, the other end of the eighth resistor C10, the other end of the sixth capacitor C15, the other end of the seventh capacitor C16, and the ground end of the 3.3V step-down chip are all grounded, the output end of the 3.3V step-down chip and one end of the eighth capacitor C17 are all connected to the power-off detection circuit, and the other end of the eighth capacitor C17 is grounded.

[0051] In this embodiment, the second linear voltage regulator circuit 107 steps down the voltage of 5V to 3.3V, provides an operating voltage to the input buffer U3 in the power failure detection circuit and provides a pull-up voltage to the comparator U4 in the power failure detection circuit.

[0052] Reference Figure 6 According to a power-off detection and protection circuit of the present invention, the energy storage circuit 109 includes:

[0053] The ninth resistor R11, the tenth resistor R12, the eleventh resistor R13, the twelfth resistor R14, the super capacitor C18, the first relay K1, the second relay K2, the third relay K3, the third diode D3, the fourth diode D4, the fifth diode D5, the field effect transistor Q1, one end of the ninth resistor R11, the normally open point of the first relay K1, the cathode of the third diode D3, the normally open point of the second relay K2, the cathode of the fourth diode D4 and the normally open point of the third relay K3 are all connected to the first linear voltage stabilizing circuit, and the other end of the ninth resistor R11 and one end of the super capacitor C18 are connected to the first linear voltage stabilizing circuit. and one end of the tenth resistor R12 are connected to the moving contact of the first relay K1, the other end of the supercapacitor C18 is grounded, the other end of the tenth resistor R12, the eleventh resistor R13 and the positive electrode of the third diode D3 are connected to the gate of the field effect tube Q1, the moving contact of the second relay K2, the positive electrode of the fourth diode D4 and the negative electrode of the fifth diode D5 are connected to the drain of the field effect tube Q1, the source of the field effect tube Q1 is grounded, the moving contact of the third relay K3 is connected to one end of the twelfth resistor R14, and the other end of the twelfth resistor R14 is connected to the positive electrode of the fifth diode D5.

[0054] In this embodiment, the 5V power provided by the first linear voltage regulator circuit 102 charges the super capacitor C18 through the ninth resistor R11.

[0055] Further, the tenth resistor R12 , the eleventh resistor R13 , the field effect transistor Q1 , the first relay K1 , the second relay K2 and the third relay K3 form a fast charging detection circuit 110 .

[0056] The bias circuit composed of the tenth resistor R12 and the eleventh resistor R13 monitors the voltage of the supercapacitor C18. When the voltage of the supercapacitor C18 reaches a specified value, the field effect transistor Q1 is turned on, the normally open point of the first relay K1 is closed, the normally open point of the second relay K2 is closed, and the normally open point of the third relay K3 is closed, and the energy storage circuit enters the fast charging mode, and the supercapacitor C18 will be fully charged within a few seconds.

[0057] Furthermore, the fifth diode D5 and the twelfth resistor R14 form a fast charging indication circuit 106 .

[0058] In this embodiment, the fifth diode D5 is a light emitting diode. When the normally open point of the third relay K3 is closed, the current will pass through the twelfth resistor R14 to reach the fifth diode D5, and the fifth diode D5 will light up. Since the supercapacitor C18 will be fully charged within a few seconds, the time is relatively short. The lighting of the fifth diode D5 can simultaneously indicate that the supercapacitor C18 is fully charged and the fast charging mode is operating normally.

[0059] Furthermore, the model of the field effect transistor Q1 is 2N7002, and the model of the super capacitor C18 is CHP5R5L255R-DA.

[0060] In this embodiment, this type of supercapacitor can meet the power required by the CPU to complete the shutdown action after power failure, and can adapt to the fast charging mode. The field effect tube model 2N7002 has a short response time, which helps to improve the working efficiency of the circuit.

[0061] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0062] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above-mentioned implementation mode. Technical personnel familiar with the field can also make various equivalent deformations or substitutions without violating the spirit of the present invention. These equivalent deformations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A power failure detection and protection circuit, characterized in that: include: 24V switching power supply, used to power the circuit; A DC / DC conversion circuit, the DC / DC conversion circuit is connected to the 24V switching power supply; A first linear voltage stabilizing circuit, the first linear voltage stabilizing circuit is connected to the DC / DC conversion circuit, the first linear voltage stabilizing circuit comprises: a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, and a 5V step-down chip, one end of the second capacitor, one end of the third capacitor, one end of the fourth capacitor, and one end of the fifth capacitor are all connected to the 5V step-down chip, and the other end of the second capacitor, the other end of the third capacitor, and the other end of the fourth capacitor are all connected to the other end of the fifth capacitor; A CPU, wherein the CPU is connected to the first linear voltage stabilization circuit; A charging circuit, wherein the first linear voltage stabilizing circuit is connected to the charging circuit; An energy storage circuit, used to supply power to the CPU when the 24V switching power supply stops supplying power, the energy storage circuit being connected to the charging circuit; A switch circuit, the energy storage circuit and the CPU are both connected to the switch circuit; A power-off detection circuit, wherein the 24V switching power supply and the CPU are both connected to the power-off detection circuit, and the power-off detection circuit comprises: a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a second diode, an output buffer, and a comparator, wherein one end of the fourth resistor is connected to the 24V switching power supply, one end of the fifth resistor and the other end of the fourth resistor are both connected to the positive input end of the comparator, one end of the sixth resistor is connected to the first linear voltage stabilization circuit, the other end of the sixth resistor and the cathode of the second diode are both connected to the negative input end of the comparator, the anode of the second diode is grounded, the output end of the comparator, one end of the seventh resistor and the A input end of the output buffer are all connected to the B input end of the output buffer, the other end of the seventh resistor is connected to the second linear voltage stabilization circuit, and the output end of the output buffer is connected to the CPU; wherein, when the 24V switching power supply is working normally, the comparator outputs a high level, and the output buffer outputs a high level to the CPU, and when the 24V switching power supply is powered off, the comparator outputs a low level, and the output buffer outputs a low level to the CPU; A second linear voltage stabilization circuit, the second linear voltage stabilization circuit is connected to the power-off detection circuit, the second linear voltage stabilization circuit includes: an eighth resistor, a sixth capacitor, a seventh capacitor, an eighth capacitor, and a 3.3V step-down chip, one end of the eighth resistor, one end of the sixth capacitor, and one end of the seventh capacitor are all connected to the input end of the 3.3V step-down chip, the other end of the eighth resistor, the other end of the sixth capacitor, the other end of the seventh capacitor, and the ground end of the 3.3V step-down chip are all grounded, the output end of the 3.3V step-down chip and one end of the eighth capacitor are all connected to the power-off detection circuit, and the other end of the eighth capacitor is grounded; the second linear voltage stabilization circuit is used to provide an operating voltage to the output buffer and a pull-up voltage to the comparator.

2. A power failure detection and protection circuit according to claim 1, characterized in that: The energy storage circuit also includes: A fast charging detection circuit, the fast charging detection circuit is connected to the charging circuit; A fast charging indication circuit, wherein the charging circuit and the fast charging detection circuit are both connected to the fast charging indication circuit.

3. A power failure detection and protection circuit according to claim 1, characterized in that: The DC / DC conversion circuit includes: a fuse, a first inductor, a second inductor, a first resistor, a second resistor, a third resistor, a first capacitor, a first diode, and a 7V buck chip. The 24V switching power supply is connected to one end of the fuse, the other end of the fuse is connected to one end of the first inductor, the other end of the first inductor is connected to the input end of the 7V buck chip, the 24V switching power supply is connected to one end of the first resistor, the other end of the first resistor is connected to the enable end of the 7V buck chip, the guide end of the 7V buck chip is connected to one end of the first capacitor, the PH end of the 7V buck chip, the negative electrode of the first diode and one end of the second inductor are all connected to the other end of the first capacitor, the other end of the second inductor is connected to one end of the second resistor, the other end of the second resistor and one end of the third resistor are all connected to the auxiliary voltage monitoring input end of the 7V buck chip, and the positive electrode of the first diode is connected to the other end of the second resistor.

4. A power failure detection and protection circuit according to claim 1, characterized in that: The second linear voltage stabilization circuit includes: an eighth resistor, a sixth capacitor, a seventh capacitor, an eighth capacitor, and a 3.3V step-down chip. One end of the eighth resistor, one end of the sixth capacitor, and one end of the seventh capacitor are all connected to the input end of the 3.3V step-down chip, the other end of the eighth resistor, the other end of the sixth capacitor, the other end of the seventh capacitor, and the ground end of the 3.3V step-down chip are all grounded, the output end of the 3.3V step-down chip and one end of the eighth capacitor are all connected to the power-off detection circuit, and the other end of the eighth capacitor is grounded.

5. A power failure detection and protection circuit according to claim 1, characterized in that: The energy storage circuit comprises: A ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a supercapacitor, a first relay, a second relay, a third relay, a third diode, a fourth diode, a fifth diode, a field effect transistor, one end of the ninth resistor, a normally open point of the first relay, a negative electrode of the third diode, a normally open point of the second relay, a negative electrode of the fourth diode and a normally open point of the third relay are all connected to the first linear voltage stabilizing circuit, the other end of the ninth resistor, one end of the supercapacitor and one end of the tenth resistor are all connected to the moving contact of the first relay, the other end of the supercapacitor is grounded, the other end of the tenth resistor, the eleventh resistor and the positive electrode of the third diode are all connected to the gate of the field effect transistor, the moving contact of the second relay, the positive electrode of the fourth diode and the negative electrode of the fifth diode are all connected to the drain of the field effect transistor, the source of the field effect transistor is grounded, the moving contact of the third relay is connected to one end of the twelfth resistor, and the other end of the twelfth resistor is connected to the positive electrode of the fifth diode.

6. A power failure detection and protection circuit according to claim 5, characterized in that: The model of the field effect tube is 2N7002, and the model of the super capacitor is CHP5R5L255R-DA.

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