Power-off protection circuit and electronic device

Abstract

The utility model relates to a kind of power failure protection circuit and electronic equipment.The circuit includes: power failure detection unit, first and second power conversion unit, charge-discharge unit and controller;Power failure detection unit connects external power input and controller, generates detection level when external power input power failure and inputs to controller;First power conversion unit connects external power input, for generating first conversion voltage;Charge-discharge unit connects first power conversion unit, charges when receiving first conversion voltage, generates discharge voltage when external power input power failure;Second power conversion unit connects first power conversion unit, charge-discharge unit, power failure detection unit and controller, generates second conversion voltage according to first conversion voltage or discharge voltage to power supply controller and power failure detection unit.Embodiment of the utility model can maintain controller for power-on state to carry out power failure processing in the period of equipment power failure, realize the power failure protection of circuit.

Description

Technical Field

[0001] This utility model relates to the field of circuit protection technology, and more specifically, to a power-off protection circuit and electronic device. Background Technology

[0002] The operation of electrical equipment relies on the stability of the underlying circuitry. In particular, the equipment requires a controller for circuit control. If the controller suddenly loses power, crucial communication data between the controller and the controlled circuit will be lost, causing the entire circuit to malfunction and become uncontrollable. Therefore, configuring the controller to provide power-loss protection for the entire device is of paramount importance. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a power-off protection circuit and electronic device that addresses the aforementioned deficiencies of the prior art.

[0004] The technical solution adopted by this utility model to solve its technical problem is: to construct a power failure protection circuit, including: a power failure detection unit, a first power conversion unit, a second power conversion unit, a charging and discharging unit, and a controller;

[0005] The power failure detection unit is used to connect to an external power input and to the controller, and is used to generate a detection level when the external power input fails and input it to the controller so that the controller can perform a power failure preparation action;

[0006] The first power conversion unit is connected to the external power input and is used to generate a first conversion voltage based on the external power input;

[0007] The charging and discharging unit is connected to the first power conversion unit and is used to charge when receiving the first conversion voltage and generate a discharge voltage when the external power input is de-energized.

[0008] The second power conversion unit is connected to the first power conversion unit, the charging and discharging unit, the power failure detection unit, and the controller, and is used to generate a second conversion voltage based on the first conversion voltage or the discharging voltage to supply power to the controller and the power failure detection unit.

[0009] In one embodiment of the power-down protection circuit of this utility model, the power-down detection unit includes: a Zener diode, a first resistor, a first diode, and an optocoupler circuit;

[0010] The first end of the Zener diode is connected to the positive terminal of the external power input, the second end of the Zener diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the cathode of the first diode and the first end of the optocoupler circuit, the anode of the first diode is connected to the negative terminal of the external power input and the second end of the optocoupler circuit, the third end of the optocoupler circuit is connected to the output terminal of the second power conversion unit, and the fourth end of the optocoupler circuit is connected to the signal input pin of the controller.

[0011] In one embodiment of the power-down protection circuit of this utility model, the optocoupler circuit includes an optocoupler chip, a second resistor, a third resistor, and a first capacitor;

[0012] The first pin of the optocoupler chip is the first terminal of the optocoupler circuit, the second pin of the optocoupler chip is the second terminal of the optocoupler circuit, the third pin of the optocoupler chip is the third terminal of the optocoupler circuit, the fourth terminal of the optocoupler chip is connected to the first terminal of the second resistor and the first terminal of the third resistor, the second terminal of the second resistor is connected to the first terminal of the first capacitor, and the second terminal of the second resistor is the fourth terminal of the optocoupler circuit, and the second terminal of the third resistor and the second terminal of the first capacitor are grounded.

[0013] In one embodiment of the power-off protection circuit of this utility model, the charging and discharging unit includes: a fourth resistor, a second diode, a first sub-charging circuit, and a second sub-charging circuit;

[0014] The first end of the fourth resistor and the cathode of the second diode are connected to the output end of the first power conversion unit and the input end of the second power conversion unit.

[0015] The first terminal of the first sub-charging circuit is connected to the second terminal of the fourth resistor and the anode of the second diode, the second terminal of the first sub-charging circuit is connected to the first terminal of the second sub-charging circuit, and the second terminal of the second sub-charging circuit is grounded.

[0016] In one embodiment of the power-off protection circuit of this utility model, the first sub-charging circuit includes a first charging capacitor, a first voltage regulator chip, a fifth resistor, a sixth resistor, and a seventh resistor; the first end of the first charging capacitor, the first end of the fifth resistor, and the first end of the sixth resistor are all connected to the second end of the fourth resistor; the second end of the fifth resistor is connected to the second end of the first voltage regulator chip; the first end of the first voltage regulator chip is connected to the second end of the sixth resistor and the first end of the seventh resistor; the second end of the first charging capacitor, the third end of the first voltage regulator chip, and the second end of the seventh resistor constitute the second end of the first sub-charging circuit; and / or

[0017] The second sub-charging circuit includes a second charging capacitor, a second voltage regulator chip, an eighth resistor, a ninth resistor, and a tenth resistor; the first end of the second charging capacitor, the first end of the eighth resistor, and the first end of the ninth resistor are all connected to the second end of the first sub-charging circuit; the second end of the eighth resistor is connected to the second end of the second voltage regulator chip; the first end of the second voltage regulator chip is connected to the second end of the ninth resistor and the first end of the tenth resistor; and the second end of the second charging capacitor, the third end of the second voltage regulator chip, and the second end of the tenth resistor are all grounded.

[0018] In one embodiment of the power-off protection circuit of this utility model, the first power conversion unit includes: a switching power supply circuit and a DC-DC conversion circuit;

[0019] The switching power supply circuit is used to connect to the external power input, to receive the input voltage of the external power input and to output the circuit operating voltage;

[0020] The DC-DC conversion circuit is connected to the switching power supply circuit and is used to receive the circuit's operating voltage to output the first conversion voltage.

[0021] In one embodiment of the power-down protection circuit of this utility model, the DC-DC conversion circuit includes a first power chip, a second capacitor, a third capacitor, a fourth capacitor, an inductor, an eleventh resistor, and a twelfth resistor.

[0022] The VIN and EN pins of the first power chip are connected to the output terminal of the switching power supply circuit, the first terminal of the second capacitor, and the first terminal of the third capacitor. The OUT pin of the first power chip is connected to the first terminal of the fourth capacitor and the first terminal of the inductor. The second terminal of the fourth capacitor is connected to the BST pin of the first power chip. The FB pin of the first power chip is connected to the first terminal of the eleventh resistor and the first terminal of the twelfth resistor. The GND pin of the first power chip, the second terminal of the second capacitor, the second terminal of the third capacitor, and the first terminal of the twelfth resistor are grounded.

[0023] The second end of the inductor is connected to the first end of the eleventh resistor and serves as the output terminal of the first power conversion unit.

[0024] In one embodiment of the power-down protection circuit of this utility model, the second power conversion unit includes a second power chip, a fifth capacitor, and a sixth capacitor;

[0025] The VIN pin of the second power chip is connected to the first terminal of the fifth capacitor and the output terminal of the first power conversion unit, and the VOUT pin of the second power chip is connected to the first terminal of the sixth capacitor and serves as the output terminal of the second power conversion unit.

[0026] The GND pin of the second power chip, the second terminal of the fifth capacitor, and the second terminal of the sixth capacitor are grounded.

[0027] In one embodiment of the power-off protection circuit of this utility model, the first voltage regulator chip in the first sub-charging circuit is model TL431; and the second voltage regulator chip in the second sub-charging circuit is model TL431.

[0028] This utility model also provides an electronic device, including the power-off protection circuit as described above.

[0029] The power-off protection circuit and electronic device of this utility model have the following beneficial effects: they can keep the controller in a powered-on state for a period of time when the device is powered off in order to perform power-off processing, thereby realizing power-off protection of the circuit. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0031] Figure 1 This is a logic block diagram of an embodiment of a power-off protection circuit according to the present invention;

[0032] Figure 2 This is a partial circuit diagram of an embodiment of a power-off protection circuit according to this utility model;

[0033] Figure 3 This is a partial circuit diagram of an embodiment of a power-off protection circuit according to this utility model;

[0034] Figure 4 This is a partial circuit diagram of an embodiment of a power-off protection circuit according to this utility model;

[0035] Figure 5 This is a partial circuit diagram of an embodiment of a power-off protection circuit according to this utility model. Detailed Implementation

[0036] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, the specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0037] like Figure 1 The diagram illustrates an embodiment of a power-off protection circuit according to the present invention. Figure 1In an embodiment of the power-down protection circuit of the present invention shown, the power-down protection circuit includes a power-down detection unit 110, a first power conversion unit 120, a second power conversion unit 130, a charging / discharging unit 140, and a controller 150. The power-down detection unit 110 is connected to an external power input and to the controller 150, and generates a detection level when the external power input fails and inputs it to the controller 150 so that the controller 150 performs a power-down preparation action. The first power conversion unit 120 is connected to the external power input and generates a first conversion voltage according to the external power input. The charging / discharging unit 140 is connected to the first power conversion unit 120 and charges when receiving the first conversion voltage and generates a discharge voltage when the external power input fails. The second power conversion unit 130 is connected to the first power conversion unit 120, the charging / discharging unit 140, the power-down detection unit 110, and the controller 150, and generates a second conversion voltage according to the first conversion voltage or the discharge voltage to supply power to the controller 150 and the power-down detection unit 110.

[0038] Specifically, in this power-down protection circuit, the power-down detection unit 110 detects the power input status of the external power source to determine whether the external power input is supplying power normally. When the external power input experiences a power outage or power failure, a corresponding detection level is generated. Upon receiving this detection level, the controller 150 determines that the external power input has been powered down and executes corresponding power-down preparation actions according to a preset processing procedure. The controller 150 may include an MCU chip and its peripheral circuits to implement the internal operating settings or control functions of the electronic device. The operating procedure of the controller 150 may differ for different electronic devices, and this embodiment does not limit it. Furthermore, the power-down preparation actions executed by the controller 150 will also be set differently for different electronic devices. For example, common power-down preparation actions may include, but are not limited to, shutting down some circuits or backing up critical data; this process is also not limited in this embodiment.

[0039] When the external power input is normal, the first power conversion unit 120 converts the input voltage of the external power input to obtain a first converted voltage. The charging / discharging unit 140 charges using the first converted voltage. Simultaneously, the second power conversion unit 130 performs a second conversion on the first converted voltage to obtain the power supply voltage required by the controller 150, i.e., the second converted voltage, ensuring that the controller 150 is in a normal power-on operating state. When the external power input is de-energized, the first power conversion unit 120 stops outputting the first converted voltage because there is no input. The charging / discharging unit 140 then enters a discharging state and outputs a discharging voltage. The second power conversion unit 130 then converts the discharging voltage of the charging / discharging unit 140 to obtain the second converted voltage, maintaining the power supply state of the controller 150. Considering that the discharging process of the charging / discharging unit 140 has a certain duration, the discharging voltage of the charging / discharging unit 140 will gradually decrease until it is less than the operating voltage threshold of the controller 150. In other words, the controller 150 will remain powered on for a period of time, but it can determine that the external power input is powered off. Therefore, the controller 150 can perform preset power-off preparation actions within a preset time period, such as shutting down critical circuits and storing the working state, so that the device will be in a safe state when the power supply to the controller 150 is completely cut off.

[0040] Through the above process, electronic devices can take necessary measures after power-off to protect their internal circuitry.

[0041] like Figure 2 As shown, in one embodiment, the power failure detection unit 110 includes: a Zener diode, a first resistor, a first diode, and an optocoupler circuit 111; the first end of the Zener diode is connected to the positive terminal of the external power input, the second end of the Zener diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the cathode of the first diode and the first end of the optocoupler circuit 111, the anode of the first diode is connected to the negative terminal of the external power input and the second end of the optocoupler circuit 111, the third end of the optocoupler circuit 111 is connected to the output terminal of the second power conversion unit 130, and the fourth end of the optocoupler circuit 111 is connected to the signal input pin of the controller 150.

[0042] Specifically, in the power-down detection unit 110, a Zener diode is used to set the detection threshold for the power-down voltage. That is, the Zener diode will only be turned off when the voltage input from the external power source is lower than its regulated voltage value, at which point the external power input can be considered to be in a power-down state. This process avoids misinterpreting reasonable changes in the external power input as a power-down state, reducing false alarms. In one embodiment, the Zener diode can be a Zener diode D1 with a regulated voltage of 6.2V, resulting in a forward voltage of 6.9V. The power-down detection unit 110 will only generate a corresponding detection level when the external power input voltage drops below 6.9V. It can be understood that the power-down detection unit 110 will also generate a corresponding level, such as a high level, when the external power input is normal. When the external power input fails, the power failure detection unit 110 generates another level, such as a low level. In this embodiment, the obtained low level is used as the detection level generated by the power failure detection unit 110, which can also be understood as the power failure detection level, and specific operations are performed accordingly.

[0043] The first resistor acts as a current-limiting resistor to prevent excessive current from entering the optocoupler circuit 111. The first resistor can be a single resistor or a combination of multiple resistors. In one embodiment, the first resistor may include resistor R1. The first diode may include diode D2 to prevent reverse voltage damage to the optocoupler circuit 111 when the external power input is reversed. When there is an external power input, the voltage difference between the first and second terminals of the optocoupler circuit 111 causes it to conduct, driving the third and fourth terminals of the optocoupler circuit 111 to conduct. The fourth terminal of the optocoupler circuit 111 generates a high level based on the output of the second power conversion unit 130. When there is no external power input (a voltage as low as a certain value can also be considered as no power input), the first and second terminals of the optocoupler circuit 111 are disconnected, the third and fourth terminals of the optocoupler circuit 111 are disconnected, and the fourth terminal of the optocoupler circuit 111 outputs a low level to the controller 150, i.e., the controller 150 receives the corresponding power-down detection level.

[0044] In one embodiment, the optocoupler circuit 111 includes an optocoupler chip, a second resistor, a third resistor, and a first capacitor; the first pin of the optocoupler chip is the first terminal of the optocoupler circuit 111, the second pin of the optocoupler chip is the second terminal of the optocoupler circuit 111, the third pin of the optocoupler chip is the third terminal of the optocoupler circuit 111, the fourth terminal of the optocoupler chip is connected to the first terminal of the second resistor and the first terminal of the third resistor, the second terminal of the second resistor is connected to the first terminal of the first capacitor, and the second terminal of the second resistor is the fourth terminal of the optocoupler circuit 111, and the second terminal of the third resistor and the second terminal of the first capacitor are grounded.

[0045] Specifically, the optocoupler circuit 111 includes an optocoupler chip U1, and a second resistor serves as a current-limiting resistor to limit the current entering the controller 150. In one embodiment, the second resistor includes resistor R2. The third resistor is a pull-down resistor, used to pull down the level of the fourth pin of the optocoupler chip U1 when it is turned off, ultimately causing the optocoupler circuit 111 to output a low level to the controller 150. In one embodiment, the third resistor includes resistor R3.

[0046] like Figure 3 As shown, the charging and discharging unit 140 includes: a fourth resistor, a second diode, a first sub-charging circuit 141, and a second sub-charging circuit 142; the first end of the fourth resistor and the cathode of the second diode are connected to the output terminal of the first power conversion unit 120 and the input terminal of the second power conversion unit 130; the first end of the first sub-charging circuit 141 is connected to the second end of the fourth resistor and the anode of the second diode, the second end of the first sub-charging circuit 141 is connected to the first end of the second sub-charging circuit 142, and the second end of the second sub-charging circuit 142 is grounded.

[0047] Specifically, the fourth resistor serves as a current-limiting resistor to limit the charging current. In one embodiment, the fourth resistor may include resistor R4. The second diode is used to realize the discharge output of the charge / discharge unit 140, wherein the second diode includes diode D3. Two-stage charging is formed through the first sub-charging circuit 141 and the second sub-charging circuit 142, so that the obtained discharge voltage meets the input requirements of the second power conversion unit 130.

[0048] Optionally, the first sub-charging circuit 141 includes a first charging capacitor, a first voltage regulator chip, a fifth resistor, a sixth resistor, and a seventh resistor; the first end of the first charging capacitor, the first end of the fifth resistor, and the first end of the sixth resistor are all connected to the second end of the fourth resistor, the second end of the fifth resistor is connected to the second end of the first voltage regulator chip, the first end of the first voltage regulator chip is connected to the second end of the sixth resistor and the first end of the seventh resistor, and the second end of the first charging capacitor, the third end of the first voltage regulator chip, and the second end of the seventh resistor are the second ends of the first sub-charging circuit 141.

[0049] Specifically, the first charging capacitor may include a charging capacitor C2, which can be a supercapacitor with a capacitance of 5 farads and a rated voltage of 2.7V. A first voltage regulator chip stabilizes the charging voltage of the supercapacitor C2 at 2.7V, ensuring a voltage difference of 2.7V across C2 and reducing charging losses. This first voltage regulator chip can be a three-terminal precision voltage regulator chip U2. The fifth resistor includes resistor R5, used to limit the current of chip U2. The sixth resistor includes resistor R6, and the seventh resistor includes resistor R7. Resistors R6 and R7 form a voltage divider circuit to provide a reference voltage for chip U2. When the voltage difference across capacitor C2 is too large, chip U2 conducts to reduce the voltage difference across C2. The first terminal of chip U2 is the reference pin, the second terminal is the cathode, and the third terminal is the anode.

[0050] Optionally, the first voltage regulator chip in the first sub-charging circuit 141 is a TL431. That is, the chip U2 can be a TL431.

[0051] Optionally, the second sub-charging circuit 142 includes a second charging capacitor, a second voltage regulator chip, an eighth resistor, a ninth resistor, and a tenth resistor; the first end of the second charging capacitor, the first end of the eighth resistor, and the first end of the ninth resistor are all connected to the second end of the first sub-charging circuit 141, the second end of the eighth resistor is connected to the second end of the second voltage regulator chip, the first end of the second voltage regulator chip is connected to the second end of the ninth resistor and the first end of the tenth resistor, and the second end of the second charging capacitor, the third end of the second voltage regulator chip, and the second end of the tenth resistor are all grounded.

[0052] Specifically, the second charging capacitor may include a charging capacitor C3, which can be a supercapacitor with a capacitance of 5 farads and a rated voltage of 2.7V. A second voltage regulator chip stabilizes the charging voltage of supercapacitor C3 at 2.7V, ensuring a voltage difference of 2.7V across C3 and reducing charging losses. This second voltage regulator chip can be a three-terminal precision voltage regulator chip U3. The eighth resistor includes resistor R8, used to limit the current of chip U3. The ninth resistor includes resistor R9, and the tenth resistor includes resistor R10. Resistors R9 and R10 form a voltage divider circuit to provide a reference voltage for chip U3. When the voltage difference across capacitor C3 is too large, chip U3 conducts to reduce the voltage difference across C3. The first terminal of chip U3 is the reference pin, the second terminal is the cathode, and the third terminal is the anode.

[0053] Optionally, the second voltage regulator chip in the second sub-charging circuit 142 is a TL431. That is, the chip U3 can be a TL431.

[0054] It can be further understood that the series connection of capacitors C2 and C3 increases the voltage at the first end of the voltage resistor R4, that is, the overall discharge voltage after series connection can reach about 5V, so as to meet the input voltage requirements of the second power conversion unit 130.

[0055] like Figure 4 As shown, the first power conversion unit 120 includes a switching power supply circuit 121 and a DC-DC converter circuit 122. The switching power supply circuit 121 is connected to an external power input, receives the input voltage from the external power input, and outputs the circuit operating voltage. The DC-DC converter circuit 122 is connected to the switching power supply circuit 121 and receives the circuit operating voltage to output a first converted voltage. Specifically, in the first power conversion unit 120, the switching power supply circuit 121 can perform preliminary voltage conversion to obtain the circuit operating voltage, which can provide the required operating voltage for the power-down protection circuit or for other operating circuits. The DC-DC converter circuit 122 converts the circuit operating voltage to obtain the required first converted voltage.

[0056] In one specific embodiment, the switching power supply circuit 121 converts the 12V voltage provided by the external power input to output a stable 12V circuit operating voltage. The DC-DC conversion circuit 122 converts the 12V circuit operating voltage to output a first converted voltage of 5V. This 5V voltage is used to charge the charge / discharge unit 140. Simultaneously, this 5V voltage can also be used as the input to the second power conversion unit 130.

[0057] In one embodiment, the DC-DC conversion circuit 122 includes a first power chip, a second capacitor, a third capacitor, a fourth capacitor, an inductor, an eleventh resistor, and a twelfth resistor. The VIN and EN pins of the first power chip are connected to the output terminal of the switching power supply circuit 121, the first terminal of the second capacitor, and the first terminal of the third capacitor. The OUT pin of the first power chip is connected to the first terminal of the fourth capacitor and the first terminal of the inductor. The second terminal of the fourth capacitor is connected to the BST pin of the first power chip. The FB pin of the first power chip is connected to the first terminal of the eleventh resistor and the first terminal of the twelfth resistor. The GND pin of the first power chip, the second terminal of the second capacitor, the second terminal of the third capacitor, and the first terminal of the twelfth resistor are grounded. The second terminal of the inductor is connected to the first terminal of the eleventh resistor and serves as the output terminal of the first power conversion unit 120.

[0058] Specifically, the first power supply chip includes chip U8, which is part of the DC-DC conversion circuit 122. Chip U8 and its peripheral circuits achieve a 12V to 5V voltage conversion. In the peripheral circuit, the second capacitor includes capacitor C34, the third capacitor includes capacitor C35, the fourth capacitor includes capacitor C33, the inductor includes inductor L4, the eleventh resistor includes resistor R31, and the twelfth resistor includes resistor R32. In one embodiment, the output of inductor L4 can be further filtered by a filter circuit composed of capacitors C36 and C37.

[0059] In one embodiment, such as Figure 5 As shown, the second power conversion unit 130 includes a second power chip, a fifth capacitor, and a sixth capacitor; the VIN pin of the second power chip is connected to the first end of the fifth capacitor and the output terminal of the first power conversion unit 120, the VOUT pin of the second power chip is connected to the first end of the sixth capacitor and serves as the output terminal of the second power conversion unit 130, and the GND pin of the second power chip, the second end of the fifth capacitor, and the second end of the sixth capacitor are grounded.

[0060] Specifically, the second power supply chip includes chip U4, which, within the second power conversion unit 130, enables voltage conversion from 5V to 3.3V through chip U4 and its peripheral circuitry. Within this peripheral circuitry, the fifth capacitor includes capacitor C4, and the sixth capacitor includes capacitor C5.

[0061] On the other hand, in the electronic device provided by this utility model, the electronic device is powered by an external power input and the external power input is monitored by a power failure protection circuit to protect the internal working circuit.

[0062] It is understood that the above embodiments only illustrate preferred embodiments of the present utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present utility model patent. It should be noted that for those skilled in the art, the above technical features can be freely combined, and several modifications and improvements can be made without departing from the concept of the present utility model, all of which fall within the protection scope of the present utility model. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present utility model should fall within the coverage of the claims of the present utility model.

Claims

1. A power-off protection circuit, characterized in that, include: Power failure detection unit, first power conversion unit, second power conversion unit, charging and discharging unit and controller; The power failure detection unit is used to connect to an external power input and to the controller, and is used to generate a detection level when the external power input fails and input it to the controller so that the controller can perform a power failure preparation action; The first power conversion unit is connected to the external power input and is used to generate a first conversion voltage based on the external power input; The charging and discharging unit is connected to the first power conversion unit and is used to charge when receiving the first conversion voltage and generate a discharge voltage when the external power input is de-energized. The second power conversion unit is connected to the first power conversion unit, the charging and discharging unit, the power failure detection unit, and the controller, and is used to generate a second conversion voltage based on the first conversion voltage or the discharging voltage to supply power to the controller and the power failure detection unit.

2. The power-off protection circuit according to claim 1, characterized in that, The power failure detection unit includes: a Zener diode, a first resistor, a first diode, and an optocoupler circuit; The first end of the Zener diode is connected to the positive terminal of the external power input, the second end of the Zener diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the cathode of the first diode and the first end of the optocoupler circuit, the anode of the first diode is connected to the negative terminal of the external power input and the second end of the optocoupler circuit, the third end of the optocoupler circuit is connected to the output terminal of the second power conversion unit, and the fourth end of the optocoupler circuit is connected to the signal input pin of the controller.

3. The power-off protection circuit according to claim 2, characterized in that, The optocoupler circuit includes an optocoupler chip, a second resistor, a third resistor, and a first capacitor; The first pin of the optocoupler chip is the first terminal of the optocoupler circuit, the second pin of the optocoupler chip is the second terminal of the optocoupler circuit, the third pin of the optocoupler chip is the third terminal of the optocoupler circuit, the fourth terminal of the optocoupler chip is connected to the first terminal of the second resistor and the first terminal of the third resistor, the second terminal of the second resistor is connected to the first terminal of the first capacitor, and the second terminal of the second resistor is the fourth terminal of the optocoupler circuit, and the second terminal of the third resistor and the second terminal of the first capacitor are grounded.

4. The power-off protection circuit according to claim 1, characterized in that, The charging and discharging unit includes: a fourth resistor, a second diode, a first sub-charging circuit, and a second sub-charging circuit; The first end of the fourth resistor and the cathode of the second diode are connected to the output end of the first power conversion unit and the input end of the second power conversion unit. The first terminal of the first sub-charging circuit is connected to the second terminal of the fourth resistor and the anode of the second diode, the second terminal of the first sub-charging circuit is connected to the first terminal of the second sub-charging circuit, and the second terminal of the second sub-charging circuit is grounded.

5. The power-off protection circuit according to claim 4, characterized in that, The first sub-charging circuit includes a first charging capacitor, a first voltage regulator chip, a fifth resistor, a sixth resistor, and a seventh resistor; the first terminal of the first charging capacitor, the first terminal of the fifth resistor, and the first terminal of the sixth resistor are all connected to the second terminal of the fourth resistor; the second terminal of the fifth resistor is connected to the second terminal of the first voltage regulator chip; the first terminal of the first voltage regulator chip is connected to the second terminal of the sixth resistor and the first terminal of the seventh resistor; the second terminal of the first charging capacitor, the third terminal of the first voltage regulator chip, and the second terminal of the seventh resistor constitute the second terminal of the first sub-charging circuit; and / or The second sub-charging circuit includes a second charging capacitor, a second voltage regulator chip, an eighth resistor, a ninth resistor, and a tenth resistor; the first end of the second charging capacitor, the first end of the eighth resistor, and the first end of the ninth resistor are all connected to the second end of the first sub-charging circuit; the second end of the eighth resistor is connected to the second end of the second voltage regulator chip; the first end of the second voltage regulator chip is connected to the second end of the ninth resistor and the first end of the tenth resistor; and the second end of the second charging capacitor, the third end of the second voltage regulator chip, and the second end of the tenth resistor are all grounded.

6. The power-off protection circuit according to claim 1, characterized in that, The first power conversion unit includes: a switching power supply circuit and a DC-DC conversion circuit; The switching power supply circuit is used to connect to the external power input, to receive the input voltage of the external power input and to output the circuit operating voltage; The DC-DC conversion circuit is connected to the switching power supply circuit and is used to receive the circuit's operating voltage to output the first conversion voltage.

7. The power-off protection circuit according to claim 6, characterized in that, The DC-DC conversion circuit includes a first power chip, a second capacitor, a third capacitor, a fourth capacitor, an inductor, an eleventh resistor, and a twelfth resistor. The VIN and EN pins of the first power chip are connected to the output terminal of the switching power supply circuit, the first terminal of the second capacitor, and the first terminal of the third capacitor. The OUT pin of the first power chip is connected to the first terminal of the fourth capacitor and the first terminal of the inductor. The second terminal of the fourth capacitor is connected to the BST pin of the first power chip. The FB pin of the first power chip is connected to the first terminal of the eleventh resistor and the first terminal of the twelfth resistor. The GND pin of the first power chip, the second terminal of the second capacitor, the second terminal of the third capacitor, and the first terminal of the twelfth resistor are grounded. The second end of the inductor is connected to the first end of the eleventh resistor and serves as the output terminal of the first power conversion unit.

8. The power-off protection circuit according to claim 1, characterized in that, The second power conversion unit includes a second power chip, a fifth capacitor, and a sixth capacitor; The VIN pin of the second power chip is connected to the first terminal of the fifth capacitor and the output terminal of the first power conversion unit, and the VOUT pin of the second power chip is connected to the first terminal of the sixth capacitor and serves as the output terminal of the second power conversion unit. The GND pin of the second power chip, the second terminal of the fifth capacitor, and the second terminal of the sixth capacitor are grounded.

9. The power-off protection circuit according to claim 5, characterized in that, In the first sub-charging circuit, the first voltage regulator chip is model TL431; in the second sub-charging circuit, the second voltage regulator chip is model TL431.

10. An electronic device, characterized in that, Includes the power failure protection circuit as described in any one of claims 1 to 9.

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