A super capacitor powered system power down hold circuit

Abstract

This utility model discloses a power-down retention circuit for a supercapacitor power supply system, relating to the field of power supply control technology. It includes a 24V to 5V DC-DC step-down circuit for voltage reduction; a current-limiting resistor for current limiting; a power-down detection circuit for voltage detection and controlling the power transfer of a first switching circuit; a supercapacitor for energy storage and discharge; a voltage detection and control circuit for monitoring the supercapacitor's voltage and controlling the second switching circuit to transfer the released energy from the supercapacitor; and a DC-DC boost circuit for voltage boosting and unidirectional transmission to the current-limiting resistor via an anti-backflow diode. Compared with existing technologies, the advantages of this utility model are: the power-down retention circuit of this supercapacitor power supply system can avoid false triggering of low-voltage protection, suppress switching cycles caused by voltage rebound, and improve the energy utilization efficiency of the supercapacitor.

Description

Technical Field

[0001] This utility model relates to the field of power supply control technology, specifically a power-off retention circuit for a supercapacitor power supply system. Background Technology

[0002] In circuit systems, there are situations where external power supply interruptions require energy storage components (such as supercapacitors) to maintain system operation and ensure that the MCU can complete critical operations such as data storage and external communication synchronization. However, supercapacitors have the characteristic that their output voltage decreases linearly with discharge, requiring voltage monitoring and protection circuits to achieve stable power supply. In existing technologies, in typical supercapacitor power-down retention circuits, the supercapacitor is connected in parallel with the external power supply through an anti-backflow diode. Under normal conditions, the external power supply powers and charges the supercapacitor. A single-channel voltage monitoring chip (such as MAX809) or comparator monitors the supercapacitor voltage. When the voltage is lower than a set threshold (such as 3.6V), the capacitor output is turned off through a MOSFET. This circuit directly uses the supercapacitor's output voltage (without boosting), relying on the capacitor's own voltage to maintain power supply. Protection is achieved through simple voltage threshold control, which has problems such as false triggering of undervoltage protection due to voltage fluctuations and rebound cycling. Therefore, improvements are needed. Utility Model Content

[0003] This utility model provides a power-off retention circuit for a supercapacitor power supply system to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, this utility model provides the following technical solution:

[0005] A power-down retention circuit for a supercapacitor power supply system includes:

[0006] A 24V to 5V DC-DC step-down circuit is used to step down the voltage of the connected 24V external power supply and output a 5V system power supply.

[0007] Current-limiting resistors are used to limit the current of 5V DC power supplied by 5V system power supplies or anti-reverse-current diodes.

[0008] The power failure detection circuit is used to detect the voltage of the 24V external power supply and control the first switching circuit to perform power transmission when the detected signal is greater than the set charging threshold, and control the first switching circuit to stop power transmission when the detected signal is less than the charging threshold.

[0009] The first switching circuit is used to transfer the received current-limited electrical energy to the supercapacitor.

[0010] Supercapacitors are used to store electrical energy transmitted by the first switching circuit and to release the stored electrical energy.

[0011] The voltage detection and control circuit is used to monitor the capacitor voltage of the supercapacitor. When the capacitor voltage reaches the discharge threshold, it controls the second switching circuit to perform power transmission. When the capacitor voltage is lower than the shutdown threshold, it controls the second switching circuit to stop power transmission.

[0012] The second switching circuit is used to transfer the electrical energy released by the supercapacitor to the DC-DC boost circuit.

[0013] The DC-DC boost circuit is used to boost the electrical energy transmitted by the second switching circuit and output 5V DC power.

[0014] Anti-reverse flow diode; used to unidirectionally transfer 5V DC power to the current-limiting resistor;

[0015] The input terminal of the 24V to 5V DC-DC step-down circuit is connected to the input terminal of the power failure detection circuit. The output terminal of the 24V to 5V DC-DC step-down circuit is connected to the input terminal of the current-limiting resistor and the output terminal of the anti-reverse-current diode. The output terminal of the current-limiting resistor is connected to the input terminal of the first switching circuit. The control terminal of the first switching circuit is connected to the output terminal of the power failure detection circuit. The output terminal of the first switching circuit, the input terminal of the voltage monitoring and control circuit, and the input terminal of the second switching circuit are all connected to a supercapacitor. The output terminal of the voltage monitoring and control circuit is connected to the control terminal of the second switching circuit. The output terminal of the second switching circuit is connected to the input terminal of the anti-reverse-current diode.

[0016] As a further embodiment of this utility model: the power-down detection circuit includes diode D1, resistor R3, resistor R6, capacitor C3, resistor R10, transistor Q11, resistor R11, resistor R4 and a 3.3V regulated power supply;

[0017] Preferably, the cathode of diode D1 is connected to a 24V external power supply, the anode of diode D1 is connected to one end of resistor R6 and grounded through resistor R3, the other end of resistor R6 is connected to one end of capacitor C3 and connected through resistor R10 to one end of resistor R4 and the base terminal of transistor Q11, the other end of capacitor C3, the other end of resistor R4 and the emitter terminal of transistor Q11 are all grounded, and the collector terminal of transistor Q11 is connected to a 3.3V regulated power supply through resistor R11.

[0018] As a further embodiment of this utility model: the current limiting resistor includes resistors R194, R201, R213 and R214; the first switching circuit includes resistors R5 and R7 and transistor Q1; the supercapacitor includes capacitors C243, C247, C227 and C228 and diode D2.

[0019] Preferably, one end of resistor R194 is connected to one end of resistor R201, one end of resistor R213 and the 5V system power supply, and is connected to one end of resistor R5 and the emitter of transistor Q1 through resistor R214. The other end of resistor R5 is connected to the base of transistor Q1 and is connected to the collector of transistor Q11 through resistor R7. The collector of transistor Q1 is connected to the positive terminal of capacitor C243, the positive terminal of capacitor C227 and the cathode of diode D2. The negative terminal of capacitor C243 is connected to the negative terminal of capacitor C227, the positive terminal of capacitor C247 and the positive terminal of capacitor C228. The negative terminal of capacitor C247 is connected to the negative terminal of capacitor C228, the anode of diode D2 and ground.

[0020] As a further embodiment of this utility model: the voltage detection and control circuit includes resistors R12, R13, R16, voltage monitoring chip U3, resistors R17 and R19;

[0021] Preferably, the fourth terminal of the voltage monitoring chip U3 is connected to the cathode of diode D2, one end of resistor R17 and one end of resistor R19, and is connected to the fifth terminal of the voltage monitoring chip U3 and one end of resistor R13 through resistor R12. The other end of resistor R13 is connected to the sixth terminal of the voltage monitoring chip U3 and is grounded through resistor R16. The other end of resistor R17 is connected to the third terminal of the voltage monitoring chip U3. The other end of resistor R19 is connected to the first terminal of the voltage monitoring chip U3. The second terminal of the voltage monitoring chip U3 is grounded.

[0022] As a further embodiment of this utility model: the second switching circuit includes resistor R18, resistor R21, MOSFET Q13, resistor R24, resistor R8, capacitor C140, MOSFET U1, resistor R25, resistor R27, resistor R14, capacitor C141, resistor R23 and diode D6.

[0023] Preferably, the gate (G) terminal of MOSFET Q13 is connected to one end of resistor R21 and then to the first terminal of voltage monitoring chip U3 via resistor R18. The source (S) terminal of MOSFET Q13 is connected to the other end of resistor R21 and ground. The drain (D) terminal of MOSFET Q13 is connected to the gate of MOSFET U1 via resistor R24, and is connected to one end of resistor R8 and one end of capacitor C140. The other end of resistor R8 is connected to the cathode of diode D2, the other end of capacitor C140, the source of MOSFET U1, and one end of resistor R25. It is also connected to the other end of resistor R25, the drain of MOSFET U1, one end of capacitor C141, and one end of resistor R14 via resistor R23. The other end of resistor R14, the other end of capacitor C141, and the first terminal of diode D6 are all grounded.

[0024] As a further embodiment of this utility model: the DC-DC boost circuit includes a fuse F1, capacitors C166 and C167, resistor R186, inductor L9, boost chip U30, diode D3, resistors R217 and R224, capacitors C152, C168 and C170.

[0025] Preferably, one end of fuse F1 is connected to the drain of MOSFET U1, and the other end of fuse F1 is connected to one end of capacitor C166, one end of capacitor C167, one end of resistor R186, and the fifth terminal of boost chip U30. It is also connected to the A terminal of diode D3 and the first terminal of boost chip U30 through inductor L9. The other end of resistor R186 is connected to the fourth terminal of boost chip U30. The other ends of capacitors C166 and C167 are both connected to the second terminal of boost chip U30. The C terminal of diode D3 is connected to one end of capacitor C152, one end of capacitor C168, and one end of capacitor C170. It is also connected to one end of resistor R224, the other end of capacitor C152, and the third terminal of boost chip U30 through resistor R217. The other ends of capacitors C168, C170, and R224 are all grounded.

[0026] Compared with the prior art, the beneficial effects of this utility model are as follows: The power-off retention circuit of the supercapacitor power supply system of this utility model can stabilize the voltage boost through the DC-DC boost circuit, isolate the impact of capacitor voltage fluctuations on the system and avoid false triggering of low voltage protection. The opening discharge threshold and the closing threshold of the voltage detection and control circuit form a 1.7V hysteresis, which is greater than the voltage rebound amplitude. Even if the capacitor voltage rebounds to 3.3V, the voltage detection and control circuit is still in the off state, suppressing the switching cycle caused by voltage rebound. The voltage detection and control circuit controls the charging and discharging of the supercapacitor, ensuring that the capacitor can maintain the boost output even when it is discharged to the limit, maximizing capacity utilization and improving the energy utilization efficiency of the supercapacitor. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic block diagram of the principle of a power-off retention circuit for a supercapacitor power supply system provided as an example of this utility model.

[0029] Figure 2 The circuit diagram of the power failure detection module provided for this utility model embodiment.

[0030] Figure 3 A connection circuit diagram of the current-limiting resistor, the first switching circuit, and the supercapacitor provided for this utility model embodiment.

[0031] Figure 4 The connection circuit diagram of the voltage monitoring and control circuit and the second switching circuit provided for this utility model embodiment.

[0032] Figure 5 Connection circuit diagram of the DC-DC boost circuit provided in this utility model embodiment Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0034] Please see Figure 1 A power-down retention circuit for a supercapacitor power supply system, comprising:

[0035] A 24V to 5V DC-DC step-down circuit is used to step down the voltage of the connected 24V external power supply and output a 5V system power supply.

[0036] Current-limiting resistors are used to limit the current of 5V DC power supplied by 5V system power supplies or anti-reverse-current diodes.

[0037] The power failure detection circuit is used to detect the voltage of the 24V external power supply and control the first switching circuit to perform power transmission when the detected signal is greater than the set charging threshold, and control the first switching circuit to stop power transmission when the detected signal is less than the charging threshold.

[0038] The first switching circuit is used to transfer the received current-limited electrical energy to the supercapacitor.

[0039] Supercapacitors are used to store electrical energy transmitted by the first switching circuit and to release the stored electrical energy.

[0040] The voltage detection and control circuit is used to monitor the capacitor voltage of the supercapacitor. When the capacitor voltage reaches the discharge threshold, it controls the second switching circuit to perform power transmission. When the capacitor voltage is lower than the shutdown threshold, it controls the second switching circuit to stop power transmission.

[0041] The second switching circuit is used to transfer the electrical energy released by the supercapacitor to the DC-DC boost circuit.

[0042] The DC-DC boost circuit is used to boost the electrical energy transmitted by the second switching circuit and output 5V DC power.

[0043] Anti-reverse flow diode; used to unidirectionally transfer 5V DC power to the current-limiting resistor;

[0044] The input terminal of the 24V to 5V DC-DC step-down circuit is connected to the input terminal of the power failure detection circuit. The output terminal of the 24V to 5V DC-DC step-down circuit is connected to the input terminal of the current-limiting resistor and the output terminal of the anti-reverse-current diode. The output terminal of the current-limiting resistor is connected to the input terminal of the first switching circuit. The control terminal of the first switching circuit is connected to the output terminal of the power failure detection circuit. The output terminal of the first switching circuit, the input terminal of the voltage monitoring and control circuit, and the input terminal of the second switching circuit are all connected to a supercapacitor. The output terminal of the voltage monitoring and control circuit is connected to the control terminal of the second switching circuit. The output terminal of the second switching circuit is connected to the input terminal of the anti-reverse-current diode.

[0045] In a specific embodiment, the aforementioned 24V to 5V DC-DC step-down circuit can be a Buck circuit composed of a step-down DC / DC controller, an inductor, a resistor, a filter capacitor, and a freewheeling diode. This circuit performs DC-DC step-down regulation on the connected 24V external power supply and outputs a 5V system power supply. The aforementioned anti-reverse current diode can be an SS54B, specifically connected in series with the output terminal of the DC-DC boost circuit to enable unidirectional transmission and prevent power reverse current.

[0046] In this embodiment, please refer to Figure 2 The power-down detection circuit includes diode D1, resistor R3, resistor R6, capacitor C3, resistor R10, transistor Q11, resistor R11, resistor R4 and a 3.3V regulated power supply.

[0047] Specifically, the cathode of diode D1 is connected to a 24V external power supply, the anode of diode D1 is connected to one end of resistor R6 and grounded through resistor R3, the other end of resistor R6 is connected to one end of capacitor C3 and connected through resistor R10 to one end of resistor R4 and the base terminal of transistor Q11, the other end of capacitor C3, the other end of resistor R4 and the emitter terminal of transistor Q11 are all grounded, and the collector terminal of transistor Q11 is connected to a 3.3V regulated power supply through resistor R11.

[0048] In a specific embodiment, the diode D1 is an 8V Zener diode. When the external 24V power supply is stepped down to 11V, it cannot trigger the B terminal of the transistor Q11 to conduct. This causes the POWDET power-down signal to flip to 3.3V. When it is greater than 11V, the B terminal of the transistor Q11 is triggered to conduct, and the POWDET power-down signal is at a low level.

[0049] In this embodiment, please refer to Figure 3The current-limiting resistors include resistors R194, R201, R213, and R214; the first switching circuit includes resistors R5 and R7 and transistor Q1; the supercapacitor includes capacitors C243, C247, C227, C228, and diode D2.

[0050] Specifically, one end of resistor R194 is connected to one end of resistor R201, one end of resistor R213, and the 5V system power supply, and is connected to one end of resistor R5 and the emitter of transistor Q1 through resistor R214. The other end of resistor R5 is connected to the base of transistor Q1 and is connected to the collector of transistor Q11 through resistor R7. The collector of transistor Q1 is connected to the positive terminal of capacitor C243, the positive terminal of capacitor C227, and the cathode of diode D2. The negative terminal of capacitor C243 is connected to the negative terminal of capacitor C227, the positive terminal of capacitor C247, and the positive terminal of capacitor C228. The negative terminal of capacitor C247 is connected to the negative terminal of capacitor C228, the anode of diode D2, and ground.

[0051] In a specific embodiment, the base voltage of the transistor Q1 is controlled by the POWDET power-down signal.

[0052] In this embodiment, please refer to Figure 4 The voltage detection and control circuit includes resistors R12, R13, R16, voltage monitoring chip U3, resistors R17 and R19;

[0053] Specifically, the fourth terminal of the voltage monitoring chip U3 is connected to the cathode of diode D2, one end of resistor R17 and one end of resistor R19, and is connected to the fifth terminal of the voltage monitoring chip U3 and one end of resistor R13 through resistor R12. The other end of resistor R13 is connected to the sixth terminal of the voltage monitoring chip U3 and is grounded through resistor R16. The other end of resistor R17 is connected to the third terminal of the voltage monitoring chip U3. The other end of resistor R19 is connected to the first terminal of the voltage monitoring chip U3. The second terminal of the voltage monitoring chip U3 is grounded.

[0054] Furthermore, the second switching circuit includes resistors R18 and R21, MOSFET Q13, R24 and R8, capacitor C140, MOSFET U1, R25 and R27, R14, capacitor C141, R23 and diode D6.

[0055] Specifically, the gate (G) terminal of MOSFET Q13 is connected to one end of resistor R21 and then to the first terminal of voltage monitoring chip U3 via resistor R18. The source (S) terminal of MOSFET Q13 is connected to the other end of resistor R21 and ground. The drain (D) terminal of MOSFET Q13 is connected to the gate of MOSFET U1 via resistor R24, and is connected to one end of resistor R8 and one end of capacitor C140. The other end of resistor R8 is connected to the cathode of diode D2, the other end of capacitor C140, the source of MOSFET U1, and one end of resistor R25. Through resistor R27, it is connected to the other end of resistor R25, the drain of MOSFET U1, one end of capacitor C141, and one end of resistor R14. Through resistor R23, it is connected to the second terminal of diode D6. The other end of resistor R14, the other end of capacitor C141, and the first terminal of diode D6 are all grounded.

[0056] In a specific embodiment, the voltage monitoring chip U3 can be a TPS3806. It collects the capacitor voltage of the supercapacitor through resistors R12, R13, and R16, sets the discharge threshold (3.6V) and the shutdown threshold (2.3V) to form a hysteresis window and suppress the cycle caused by voltage rebound. When the voltage is greater than 3.6V, the first terminal of the TPS3806 outputs a "discharge allowed" signal, triggering the MOSFET Q13 to turn on. When the voltage is less than or equal to 2.3V, the first terminal of the TPS3806 outputs a "discharge off" signal, and the MOSFET Q13 turns off.

[0057] In this embodiment, please refer to Figure 5 The DC-DC boost circuit includes fuse F1, capacitor C166, capacitor C167, resistor R186, inductor L9, boost chip U30, diode D3, resistor R217, resistor R224, capacitor C152, capacitor C168 and capacitor C170.

[0058] Specifically, one end of fuse F1 is connected to the drain of MOSFET U1, and the other end of fuse F1 is connected to one end of capacitor C166, one end of capacitor C167, one end of resistor R186, and the fifth terminal of boost chip U30. Through inductor L9, it is connected to the A terminal of diode D3 and the first terminal of boost chip U30. The other end of resistor R186 is connected to the fourth terminal of boost chip U30. The other ends of capacitors C166 and C167 are both connected to the second terminal of boost chip U30. The C terminal of diode D3 is connected to one end of capacitor C152, one end of capacitor C168, and one end of capacitor C170. Through resistor R217, it is connected to one end of resistor R224, the other end of capacitor C152, and the third terminal of boost chip U30. The other ends of capacitors C168, C170, and R224 are all grounded.

[0059] In a specific embodiment, the aforementioned boost chip U30 can be an MT36291, which, together with capacitors C166, C167, R186, L9, diode D3, R217, R224, C152, C168, and C170, forms a boost circuit. The minimum operating voltage of the boost chip U30 is 2.2V, which is lower than the turn-off threshold, to ensure that the boost output can still be maintained even when the capacitor is discharged to its limit, maximizing capacity utilization.

[0060] The working principle of this invention is as follows: A 24V to 5V DC-DC step-down circuit steps down the input 24V external power supply and outputs a 5V system power supply. This 5V system power supply is current-limited by a current-limiting resistor consisting of resistors R194, R201, R213, and R214. When the voltage supplied by the 24V external power supply connected to diode D1 is greater than 11V, it triggers the base (B) of transistor Q11 to conduct, and the output POWDET power-down signal becomes low, triggering transistor Q11 to conduct. The supercapacitor consisting of capacitors C243, C247, C227, and C228 stores energy. When the voltage supplied by the 24V external power supply drops to 11V, it cannot trigger the base (B) of transistor Q11 to conduct, causing the output POWDET power-down signal to flip to 3.3V. Transistor Q1 turns off, the supercapacitor stops storing energy, and the voltage is then transferred through resistors R12, R13, and R16, and the voltage monitoring chip U3. Resistors R17 and R19 monitor the supercapacitor's voltage. When the capacitor voltage reaches the 3.6V discharge threshold set by the voltage monitoring chip U3, MOSFET Q13 is triggered to conduct, pulling down the gate voltage of MOSFET U1. MOSFET U1 then conducts, allowing the energy (2.3V~5V) released by the supercapacitor transmitted through MOSFET U1 to be boosted to 5V by fuse F1, capacitors C166 and C167, resistor R186, inductor L9, boost chip U30, diode D3, resistors R217 and R224, capacitors C152, C168, and C170. This energy is then unidirectionally transmitted to the current-limiting resistor via the anti-reverse-current diode. When the capacitor voltage is less than or equal to 2.3V, the voltage monitoring chip U3 controls MOSFET Q13 to turn off, MOSFET U1 to turn off, and the supercapacitor stops discharging. The power-down detection circuit continuously monitors the 24V external power supply to restart charging after the 24V external power supply is restored.

[0061] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0062] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A power-down retention circuit for a supercapacitor power supply system, characterized in that, The circuit includes: A 24V to 5V DC-DC step-down circuit is used to step down the voltage of the connected 24V external power supply and output a 5V system power supply. Current-limiting resistors are used to limit the current of 5V DC power supplied by 5V system power supplies or anti-reverse-current diodes. The power failure detection circuit is used to detect the voltage of the 24V external power supply and control the first switching circuit to perform power transmission when the detected signal is greater than the set charging threshold, and control the first switching circuit to stop power transmission when the detected signal is less than the charging threshold. The first switching circuit is used to transfer the received current-limited electrical energy to the supercapacitor. Supercapacitors are used to store electrical energy transmitted by the first switching circuit and to release the stored electrical energy. The voltage detection and control circuit is used to monitor the capacitor voltage of the supercapacitor. When the capacitor voltage reaches the discharge threshold, it controls the second switching circuit to perform power transmission. When the capacitor voltage is lower than the shutdown threshold, it controls the second switching circuit to stop power transmission. The second switching circuit is used to transfer the electrical energy released by the supercapacitor to the DC-DC boost circuit. The DC-DC boost circuit is used to boost the electrical energy transmitted by the second switching circuit and output 5V DC power. Anti-reverse flow diode; used to unidirectionally transfer 5V DC power to the current-limiting resistor; The input terminal of the 24V to 5V DC-DC step-down circuit is connected to the input terminal of the power failure detection circuit. The output terminal of the 24V to 5V DC-DC step-down circuit is connected to the input terminal of the current-limiting resistor and the output terminal of the anti-reverse-current diode. The output terminal of the current-limiting resistor is connected to the input terminal of the first switching circuit. The control terminal of the first switching circuit is connected to the output terminal of the power failure detection circuit. The output terminal of the first switching circuit, the input terminal of the voltage monitoring and control circuit, and the input terminal of the second switching circuit are all connected to a supercapacitor. The output terminal of the voltage monitoring and control circuit is connected to the control terminal of the second switching circuit. The output terminal of the second switching circuit is connected to the input terminal of the anti-reverse-current diode.

2. The power-off retention circuit of a supercapacitor power supply system according to claim 1, characterized in that, The power failure detection circuit includes diode D1, resistor R3, resistor R6, capacitor C3, resistor R10, transistor Q11, resistor R11, resistor R4, and a 3.3V regulated power supply. The cathode of diode D1 is connected to a 24V external power supply. The anode of diode D1 is connected to one end of resistor R6 and grounded through resistor R3. The other end of resistor R6 is connected to one end of capacitor C3 and then connected through resistor R10 to one end of resistor R4 and the base (B) terminal of transistor Q11. The other ends of capacitor C3, resistor R4, and transistor Q11 are all grounded. The collector (C) terminal of transistor Q11 is connected to a 3.3V regulated power supply through resistor R11.

3. The power-down retention circuit of a supercapacitor power supply system according to claim 2, characterized in that, The current-limiting resistors include resistors R194, R201, R213, and R214; the first switching circuit includes resistors R5 and R7 and transistor Q1; the supercapacitor includes capacitors C243, C247, C227, C228, and diode D2. One end of resistor R194 is connected to one end of resistor R201, one end of resistor R213 and the 5V system power supply, and is connected to one end of resistor R5 and the emitter of transistor Q1 through resistor R214. The other end of resistor R5 is connected to the base of transistor Q1 and is connected to the collector of transistor Q11 through resistor R7. The collector of transistor Q1 is connected to the positive terminal of capacitor C243, the positive terminal of capacitor C227 and the cathode of diode D2. The negative terminal of capacitor C243 is connected to the negative terminal of capacitor C227, the positive terminal of capacitor C247 and the positive terminal of capacitor C228. The negative terminal of capacitor C247 is connected to the negative terminal of capacitor C228, the anode of diode D2 and ground.

4. The power-off retention circuit of a supercapacitor power supply system according to claim 3, characterized in that, The voltage detection and control circuit includes resistors R12, R13, R16, voltage monitoring chip U3, resistors R17 and R19; The fourth terminal of the voltage monitoring chip U3 is connected to the cathode of diode D2, one end of resistor R17 and one end of resistor R19, and is connected to the fifth terminal of voltage monitoring chip U3 and one end of resistor R13 through resistor R12. The other end of resistor R13 is connected to the sixth terminal of voltage monitoring chip U3 and is grounded through resistor R16. The other end of resistor R17 is connected to the third terminal of voltage monitoring chip U3. The other end of resistor R19 is connected to the first terminal of voltage monitoring chip U3. The second terminal of voltage monitoring chip U3 is grounded.

5. The power-down retention circuit of a supercapacitor power supply system according to claim 4, characterized in that, The second switching circuit includes resistor R18, resistor R21, MOSFET Q13, resistor R24, resistor R8, capacitor C140, MOSFET U1, resistor R25, resistor R27, resistor R14, capacitor C141, resistor R23 and diode D6. The gate (G) terminal of the MOSFET Q13 is connected to one end of resistor R21 and then to the first terminal of the voltage monitoring chip U3 via resistor R18. The source (S) terminal of the MOSFET Q13 is connected to the other end of resistor R21 and ground. The drain (D) terminal of the MOSFET Q13 is connected to the gate of the MOSFET U1 via resistor R24, and is connected to one end of resistor R8 and one end of capacitor C140. The other end of resistor R8 is connected to the cathode of diode D2, the other end of capacitor C140, the source of MOSFET U1, and one end of resistor R25. It is also connected to the other end of resistor R25, the drain of MOSFET U1, one end of capacitor C141, and one end of resistor R14 via resistor R27. Finally, it is connected to the second terminal of diode D6 via resistor R23. The other end of resistor R14, the other end of capacitor C141, and the first terminal of diode D6 are all grounded.

6. The power-down retention circuit of a supercapacitor power supply system according to claim 5, characterized in that, The DC-DC boost circuit includes a fuse F1, capacitors C166 and C167, a resistor R186, an inductor L9, a boost chip U30, a diode D3, a resistor R217, a resistor R224, a capacitor C152, a capacitor C168, and a capacitor C170. One end of the fuse F1 is connected to the drain of the MOSFET U1. The other end of the fuse F1 is connected to one end of capacitor C166, one end of capacitor C167, one end of resistor R186, and the fifth terminal of the boost chip U30. It is also connected to the A terminal of diode D3 and the first terminal of boost chip U30 through inductor L9. The other end of resistor R186 is connected to the fourth terminal of boost chip U30. The other ends of capacitors C166 and C167 are both connected to the second terminal of boost chip U30. The C terminal of diode D3 is connected to one end of capacitor C152, one end of capacitor C168, and one end of capacitor C170. It is also connected to one end of resistor R224, the other end of capacitor C152, and the third terminal of boost chip U30 through resistor R217. The other ends of capacitors C168, C170, and R224 are all grounded.

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