Capacitor charging and discharging circuit and Internet of Things equipment

Abstract

The utility model relates to the technical field of Internet of Things equipment, and discloses a capacitor charging and discharging circuit and Internet of Things equipment, and the circuit comprises a plurality of super capacitors, a negative temperature coefficient sensing circuit, a conversion circuit, a discharging control circuit, a control signal conversion circuit, and a charging control circuit. Wherein the negative temperature coefficient sensing circuit is used for detecting the ambient temperature around the super capacitor, and the conversion circuit is used for converting an electric signal output by the negative temperature coefficient sensing circuit into a corresponding temperature feedback signal. The input end of the discharge control circuit is connected with the super capacitor, and the output end is connected with a load. The control signal conversion circuit is used for converting the temperature feedback signal output by the conversion circuit into a corresponding control voltage, and the charging control circuit is used for controlling a charging voltage for charging the super capacitor according to the control voltage. According to the capacitor charging and discharging circuit, the temperature self-adaptive control of the charging voltage of the super capacitor can be realized with lower cost, and the service life of the super capacitor is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of Internet of Things devices, and in particular to a capacitor charging and discharging circuit and an Internet of Things device. Background Art

[0002] With the development of communication technology, IoT technologies such as LTE-4G and NB-I oT have also begun to be widely used in various IoT meters, enabling IoT meters to carry out real-time data transmission with data centers and realize remote meter reading and other operations. When a power outage occurs, the IoT meter needs to use its own capacitor energy storage to power the communication unit for a certain period of time, so that after losing the external power supply, the last data frame containing metering data and alarm information can be sent to the master station, so that the master station can obtain the power-off event of the energy meter on site in time, and ensure the integrity and traceability of the master station's energy meter data, that is, the IoT meter needs to have a "Last Gasp" function.

[0003] Through the long-term experience of the operation of the energy meter and the research on related devices accumulated by our company, it is found that the working life of the supercapacitor used for energy storage backup in the "Last Gasp" function is related to its operating temperature. Under the same operating voltage, its life can be doubled for every 10 degrees Celsius decrease in operating temperature, and under the same operating temperature, its life can be doubled for every 0.2V decrease in operating voltage. Therefore, effectively adjusting and controlling the working voltage of the supercapacitor according to the operating temperature of the supercapacitor can greatly improve the working life of the supercapacitor and reduce the failure rate of on-site operation. At present, the temperature measurement method requires the temperature detected by the temperature sensor to be transmitted to the single-chip microcomputer system through the analog-to-digital conversion circuit, and it is also necessary to design a more complex single-chip microcomputer control circuit. The development cost and implementation cost are both high. If it is applied to IoT devices such as IoT energy meters with large investment, it will greatly increase the implementation cost of the IoT system. For this reason, it is necessary to design a capacitor charging and discharging circuit with low implementation and development costs, which can realize the adaptive reduction of the charging voltage of the supercapacitor according to the temperature rise of the supercapacitor and improve the life of the supercapacitor. Utility Model Content

[0004] In order to overcome the shortcomings of the prior art, the purpose of the utility model is to provide a temperature measurement circuit, which is completely composed of analog circuits and can control the charging voltage of the supercapacitor according to the temperature of the supercapacitor without the participation of a programmable controller such as a single-chip microcomputer, thereby improving the service life of the supercapacitor at a lower development and implementation cost.

[0005] In order to solve the above problems, the technical solution adopted by the utility model is as follows: a capacitor charging circuit, comprising: a plurality of supercapacitors; a negative temperature coefficient sensor circuit, arranged on one side of the supercapacitor, for detecting the ambient temperature around the supercapacitor; a conversion circuit, whose input end is connected to the output end of the negative temperature coefficient sensor circuit, for converting the electrical signal output by the negative temperature coefficient sensor circuit into a corresponding temperature feedback signal; a discharge control circuit, whose input end is connected to the supercapacitor and whose output end is connected to a load; a control signal conversion circuit, whose input end is connected to the output end of the conversion circuit, for converting the temperature feedback signal output by the conversion circuit into a corresponding control voltage; a charging control circuit, whose input end is connected to an input power supply, whose output end is connected to the supercapacitor, and whose control end is connected to the output end of the control signal conversion circuit, for controlling the charging voltage charged to the supercapacitor according to the control voltage.

[0006] Compared with the prior art, the beneficial effect of the utility model is that: by setting a sensor circuit with a negative temperature coefficient next to the supercapacitor, the output of the sensor circuit is directly converted into a control voltage through a conversion circuit and a control signal conversion circuit and transmitted to the charging control circuit. Since the output electrical signal of the sensor circuit with a negative temperature coefficient will decrease as the temperature of the supercapacitor increases, the converted control voltage will also decrease as the temperature of the supercapacitor increases, so that the charging control circuit can adaptively reduce the charging voltage of the supercapacitor according to the increase in the temperature of the supercapacitor to extend the life of the supercapacitor. The entire control circuit is completely composed of analog circuits, does not require the participation of controllers such as digital-to-analog conversion circuits and single-chip microcomputers, and has low implementation and development costs.

[0007] The above-mentioned capacitor charging and discharging circuit, the negative temperature coefficient sensing circuit includes: a temperature measuring transistor, the emitter is grounded, the base is connected to its working voltage, is arranged on one side of the supercapacitor, and the collector is connected to the input end of the conversion circuit; a constant current source, the output end is connected to the collector of the temperature measuring transistor, and is used to provide a specific current to the collector of the temperature measuring transistor, so that the base-emitter conduction voltage of the temperature measuring transistor has temperature dependence.

[0008] The above-mentioned capacitor charging and discharging circuit, the conversion circuit includes a follower circuit and an amplifier circuit, the input end of the follower circuit is connected to the collector of the temperature measuring transistor, the output end of the follower circuit is connected to the input end of the amplifier circuit, and the output end of the amplifier circuit is connected to the input end of the control signal conversion circuit as the output end of the conversion circuit.

[0009] In the above-mentioned capacitor charging and discharging circuit, the constant current source includes a voltage stabilizing chip U2, a transistor Q1 and a plurality of resistors. The input pin of the voltage stabilizing chip U2 is connected to the working voltage through the resistor R5, the output end of the voltage stabilizing chip U2 is connected to the base and collector of the temperature measuring transistor Q3, the reference end of the voltage stabilizing chip U2 is connected to the emitter of the transistor Q1, the collector of the transistor Q1 is connected to the working voltage, the base of the transistor Q1 is connected to the working voltage through the resistor R5, and the emitter of the transistor Q1 is connected to the collector of the temperature measuring transistor Q3 through the resistor R10.

[0010] In the above-mentioned capacitor charging and discharging circuit, the amplifier circuit of the conversion circuit is a reverse offset amplifier circuit.

[0011] The above-mentioned capacitor charging and discharging circuit, the amplifier circuit includes a voltage stabilizing chip U3, a transistor Q2, an operational amplifier U1B, a number of resistors and capacitors, the input end of the voltage stabilizing chip U3 is connected to the working voltage through a resistor R6, the output end of the voltage stabilizing chip U3 is connected to the non-inverting input end of the operational amplifier U1 B, the reference end of the voltage stabilizing chip U3 is connected to the emitter of the transistor Q1, the emitter of the transistor Q2 is connected to the non-inverting input end of the operational amplifier U1 B through a resistor R11, the collector of the transistor Q2 is connected to the working voltage, the base of the transistor Q2 is connected to the input end of the voltage stabilizing chip U3, the inverting input end of the operational amplifier U1 B is connected to the output end of the follower circuit through a resistor R2, the inverting input end of the operational amplifier U1 B is connected to its output end through a resistor R1, the non-inverting input end of the operational amplifier U1 B is grounded through a resistor R3, the non-inverting input end of the operational amplifier U1 B is grounded through a resistor R4, and the output end of the operational amplifier U1 B is connected to the control end of the charging control circuit as the output end of the amplifier circuit.

[0012] The above-mentioned capacitor charging and discharging circuit, the charging control circuit includes a transistor Q4, an operational amplifier U5B and a plurality of resistors, the non-inverting input terminal of the operational amplifier U5B is connected to the output terminal of the control signal conversion circuit through a resistor R16, the non-inverting input terminal of the operational amplifier U5B is grounded through a resistor R19, the inverting input terminal of the operational amplifier U5B is grounded through a resistor R24, the inverting input terminal of the operational amplifier U5B is connected to the super capacitor through a resistor R21, the output terminal of the operational amplifier U5B is connected to the base of the transistor Q4 through a resistor R17, the collector of the transistor Q4 is connected to the working voltage, the emitter of the transistor Q4 is grounded through a resistor R25, the emitter of the transistor Q4 is connected to the super capacitor through a resistor R20, and a resistor R23 is connected in parallel at both ends of the resistor R20.

[0013] The above-mentioned capacitor charging and discharging circuit, the discharge control circuit includes an operational amplifier U5A, a transistor Q5 and a plurality of resistors, the non-inverting input terminal of the operational amplifier U5A is connected to the working voltage through the resistor R15, the inverting input terminal of the operational amplifier U5A is connected to the super capacitor, the output terminal of the operational amplifier U5A is connected to the super capacitor through the resistor R18 and the resistor R22, the output terminal of the operational amplifier U5A is connected to the gate of the transistor Q5, the source of the transistor Q5 is connected to the super capacitor, and the drain of the transistor Q5 is connected to the load.

[0014] The above-mentioned capacitor charging and discharging circuit, the control signal conversion circuit includes an operational amplifier U4A, a plurality of resistors and capacitors, the output end of the operational amplifier U4A is connected to the control end of the charging control circuit as the output end of the control signal conversion circuit, the output end of the operational amplifier U4A is connected to its inverting input end through a resistor R7, the inverting input end of the operational amplifier U4A is connected to the output end of the conversion circuit through a resistor R8, the non-inverting input end of the operational amplifier U4A is grounded through a resistor R14, the non-inverting input end of the operational amplifier U4A is grounded through resistors R12 and R13, the two ends of the resistor R13 are connected in parallel with a capacitor C7, and the connection node between the resistor R12 and the resistor R13 is connected to the working voltage through a resistor R9.

[0015] An Internet of Things device comprises the above-mentioned capacitor charging and discharging circuit.

[0016] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a principle block diagram of a capacitor charging and discharging circuit according to an embodiment of the utility model;

[0018] Figure 2 It is a schematic diagram of a negative temperature coefficient sensor circuit according to an embodiment of the utility model;

[0019] Figure 3 The schematic diagram of the conversion circuit of the embodiment of the utility model;

[0020] Figure 4 This is a schematic diagram of a control signal conversion circuit according to an embodiment of the present utility model;

[0021] Figure 5 The figure is a schematic diagram of a charging control circuit and a discharging control circuit according to an embodiment of the utility model. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below. Figure 1The capacitor charging and discharging circuit of the embodiment of the utility model includes a plurality of supercapacitors, a negative temperature coefficient sensor circuit, a conversion circuit, a discharge control circuit, a control signal conversion circuit and a charging control circuit. Among them, a plurality of supercapacitors are connected in series or in parallel to form a supercapacitor group. The negative temperature coefficient sensor circuit is arranged on one side of the supercapacitor, and is used to detect the ambient temperature around the supercapacitor. The input end of the conversion circuit is connected to the output end of the negative temperature coefficient sensor circuit, and is used to convert the electrical signal output by the negative temperature coefficient sensor circuit into a corresponding temperature feedback signal. The input end of the discharge control circuit is connected to the supercapacitor, and the output end is connected to the load. The input end of the control signal conversion circuit is connected to the output end of the conversion circuit, and is used to convert the temperature feedback signal output by the conversion circuit into a corresponding control voltage. The input end of the charging control circuit is connected to the output power supply, the output end is connected to the supercapacitor, and the control end is connected to the output end of the control signal conversion circuit, and is used to control the charging voltage charged to the supercapacitor according to the control voltage.

[0023] In the capacitor charging and discharging circuit of the utility model embodiment, the negative temperature coefficient sensing circuit is arranged near the super capacitor, and the temperature change of the super capacitor can be detected. Since it has a negative temperature coefficient, the output of the negative temperature coefficient sensing circuit will decrease as the temperature of the super capacitor rises. Correspondingly, the control voltage converted by the conversion circuit and the control signal conversion circuit according to the output of the negative temperature coefficient sensing circuit will also decrease as the temperature of the super capacitor rises, so that the charging voltage output by the control charging control circuit to the super capacitor can also decrease as the temperature of the super capacitor rises, thereby extending the service life of the super capacitor. Since the conversion circuit and the control signal conversion circuit only involve the conversion of voltage or current, which can be realized by an analog circuit, the control process of the entire capacitor charging and discharging circuit does not require the participation of a programmable controller such as a single-chip microcomputer, nor does it involve the conversion of digital and analog quantities. The implementation and development costs are both low, and the temperature adaptive control of the charging voltage of the super capacitor can be realized at a low cost, and the life of the super capacitor can be improved at a low cost.

[0024] It is understood that the negative temperature coefficient sensing circuit can use a thermistor with a negative temperature coefficient, or use a transistor, and use the PN junction temperature dependence characteristics of the transistor Ebers-Moll equation to provide a specific collector operating current to the transistor, so that the base-emitter conduction voltage V BE It has a relatively stable temperature dependence. Figure 2 In this embodiment, the negative temperature coefficient sensing circuit includes a temperature measuring transistor Q1 and a constant current source, the constant current source is used to provide a stable current of a specific value to the collector of the temperature measuring transistor Q1, so that the conduction voltage V BEIt has a relatively stable temperature dependence. The constant current source includes a voltage stabilizing chip U2, a transistor Q1 and several resistors. The input pin of the voltage stabilizing chip U2 is connected to the working voltage through a resistor R5, the output end is connected to the base and collector of the temperature measuring transistor Q3, and the reference end is connected to the emitter of the transistor Q1. The collector of the transistor Q1 is connected to the working voltage, the base of the transistor Q1 is connected to the working voltage through a resistor R5, and the emitter of the transistor Q1 is connected to the collector of the temperature measuring transistor Q3 through a resistor R10. In this embodiment, the temperature measuring transistor Q1 uses a transistor of model BC846. When the transistor is in a saturated state, the conduction voltage V BE It has a negative temperature coefficient of -2mV / ℃. In the temperature range of -40°C to +100°C, the VBE output voltage is 708mV to 430mV. The constant current source needs to provide a constant current of 1mA to the collector of the temperature measuring transistor Q3 to stabilize the temperature measuring transistor Q3 in a saturated state. The voltage regulator chip U2 is a TL431 voltage regulator chip. A constant voltage of 2.5V can be provided between its output terminal 1 pin and reference terminal 2 pin. When the current formed on the resistor R10 is too large, the input current of the input terminal 3 pin of the voltage regulator chip will increase, thereby reducing the base current of the transistor Q1, forcing the transistor Q1 to reduce the current supplied to the resistor R10; vice versa, so that the resistance flowing through the resistor R10 is always stable at the required 1mA, ensuring that the temperature measuring transistor Q3 will not be pushed out of the saturated state due to power supply fluctuations, and providing an accurate on-voltage V corresponding to the temperature. BE R5 is used to provide bias operating current to ensure that the voltage regulator chip U2 and transistor Q1 have appropriate operating current.

[0025] It can be understood that the conversion circuit and the control signal conversion circuit can both be composed of operational amplifier circuits, and the amplification factor and whether an offset is required are determined according to the parameters of the selected negative temperature coefficient temperature sensor and the mapping relationship between the temperature and the charging voltage of the supercapacitor. In this embodiment, when the ambient temperature around the supercapacitor is in the range of -40℃ to +25℃, the charging voltage of the supercapacitor is limited to 2.1V; when the ambient temperature around the supercapacitor is in the range of +25℃ to +100℃, the charging voltage of the supercapacitor is linearly decreased within 2.1 to 0.5V as the ambient temperature increases, so as to maximize the life of the supercapacitor.

[0026] Accordingly, refer to Figure 3 The conversion circuit includes a follower circuit and a reverse offset amplifier circuit to adjust the conduction voltage V of the temperature measuring transistor Q3. BEAmplification, offset and "filtering" processing are performed. The follower circuit includes an operational amplifier U1A, the non-inverting input terminal of the operational amplifier U1A is connected to the collector of the temperature measuring transistor Q3, and the inverting input terminal is connected to its output terminal, which is used to increase the input impedance of the conversion circuit to improve the anti-interference performance of the conversion circuit. The reverse offset amplifier circuit includes a voltage regulator chip U3, a transistor Q2, an operational amplifier U1 B, a number of resistors and capacitors. The input terminal of the voltage regulator chip U3 is connected to the working voltage through a resistor R6, the output terminal of the voltage regulator chip U3 is connected to the non-inverting input terminal of the operational amplifier U1B, and the reference terminal of the voltage regulator chip U3 is connected to the emitter of the transistor Q1. The emitter of the transistor Q2 is connected to the non-inverting input terminal of the operational amplifier U1B through a resistor R11, the collector of the transistor Q2 is connected to the working voltage, and the base of the transistor Q2 is connected to the input terminal of the voltage regulator chip U3. The inverting input terminal of the operational amplifier U1 B is connected to the output terminal of the follower circuit through a resistor R2, and is connected to its output terminal through a resistor R1, and the non-inverting input terminal is grounded through a resistor R3, and is grounded through a resistor R4. The output end of the operational amplifier U1B is connected to the control end of the charging control circuit as the output end of the reverse offset amplifier circuit. The reverse offset amplifier circuit converts the conduction voltage V BE After being reverse biased to 0.5V, it is amplified ten times and transmitted to the control signal conversion circuit, which converts it into a control voltage. The voltage regulator chip U3 and transistor Q2 form another constant current source, providing a 100uA reference current to the non-inverting input of the operational amplifier U1B, and forming a 0.5V bias reference voltage in conjunction with resistors R3 and R4.

[0027] Reference Figure 4 In this embodiment, the control signal conversion circuit is a subtraction differential amplifier circuit, including an operational amplifier U4A, a plurality of resistors and capacitors. The output end of the operational amplifier U4A is connected to the control end of the charging control circuit as the output end of the control signal conversion circuit, and its output end is also connected to its inverting input end through a resistor R7. The inverting input end of the operational amplifier U4A is connected to the output end of the operational amplifier U1B through a resistor R8, and the in-phase input end is grounded through a resistor R14. The in-phase input end is also grounded through resistors R12 and R13. Capacitor C7 is connected in parallel at both ends of the resistor R13, and the connection node between the resistor R12 and the resistor R13 is connected to the working voltage through a resistor R9. The input 3.9V working voltage is biased into a minuend voltage of 2.1V by resistors R9 and R13 and output to the non-inverting input terminal of the operational amplifier U4A, and after subtracting the output temperature feedback signal VTEM input from the inverting input terminal, it is input to the differential amplifier circuit composed of the operational amplifier U4A, resistors R8, R12, R14 and R7 for amplification to improve the common-mode anti-interference capability, and finally a control voltage of 2.1 to 0.5V is formed and output to the charging control circuit.

[0028] It can be understood that the charging control circuit is a voltage stabilizing circuit, which stabilizes the charging voltage output to the supercapacitor at the value of the control voltage. The discharge control circuit is used to control the on-off between the supercapacitor and the load. When the external power supply is disconnected, the supercapacitor and the load are connected to continue to supply power to the load for a period of time.

[0029] Reference Figure 5 , the charging control circuit includes a transistor Q4, an operational amplifier U5B and a plurality of resistors. The non-inverting input of the operational amplifier U5B is connected to the output of the operational amplifier U4A through a resistor R16, the non-inverting input is grounded through a resistor R19, the inverting input is grounded through a resistor R24, and the inverting input is also connected to supercapacitors C10 and C11 through a resistor R21. The output of the operational amplifier U5B is connected to the base of the transistor Q4 through a resistor R17, the collector of the transistor Q4 is connected to the working voltage, the emitter of the transistor Q4 is grounded through a resistor R25, the emitter of the transistor Q4 is connected to supercapacitors C10 and C11 through a resistor R20, and a resistor R23 is connected in parallel at both ends of the resistor R20. The input 3.9V working voltage charges the supercapacitors C10 and C11 through the transistor Q4, and the resistors R24 and R21 perform voltage-dividing sampling on the voltage of the supercapacitor. When the charging voltage of the supercapacitor is greater than the control voltage, the operational amplifier U5B outputs a low level, forcing the transistor Q4 to turn off, thereby stopping the charging of the supercapacitor; otherwise, the transistor Q4 is driven to turn on, charging the supercapacitor, and the charging voltage of the supercapacitor is stabilized at the control voltage VREF by controlling the on and off of the transistor Q4. Resistors R17, R23 and R25 are used for current limiting and voltage stabilization.

[0030] The discharge control circuit includes an operational amplifier U5A, a transistor Q5 and several resistors. The in-phase input terminal of the operational amplifier U5A is connected to the working voltage through the resistor R15, the inverting input terminal is connected to the supercapacitors C10 and C11, the output terminal is connected to the supercapacitors C10 and C11 through the resistors R18 and R22, and the output terminal is connected to the gate of the transistor Q5. The source of the transistor Q5 is connected to the supercapacitors C10 and C11, and the drain is connected to the load that needs to be powered. When the input working voltage drops to 0 or lower than the voltage of the supercapacitor, the operational amplifier U5A outputs a high level, the transistor Q5 driven as PMOS is turned on, and the supercapacitor outputs voltage to the outside; otherwise, the transistor Q5 is turned off, and the supercapacitor will not discharge to the outside.

[0031] The Internet of Things device of the embodiment of the utility model includes the above-mentioned capacitor charging and discharging circuit, which can realize temperature adaptive control of the capacitor charging voltage at a relatively low cost, and can extend the service life of the supercapacitor. The Internet of Things device can be an Internet of Things electric energy meter, and also includes a buck circuit and a boost circuit. The buck circuit is used to convert the external power supply into a 3.9V working voltage and provide it to the capacitor charging and discharging circuit to maintain the operation of the capacitor charging and discharging circuit and the charging of the supercapacitor. The output end of the capacitor charging and discharging circuit is connected to a load such as an NB-IOT unit that needs to be powered for a period of time after power failure through a boost circuit. After the external power supply is powered off, the electric energy discharged by the supercapacitor is converted into the voltage required by the load, the load is supplied to continue working for a period of time, and the last data frame containing metering data and alarm information is sent to the main station.

[0032] It should be noted that in the description of the present invention, if there are any orientation descriptions, such as up, down, front, back, left, right, etc., the orientations or positional relationships indicated are all based on the orientations or positional relationships shown in the drawings. They 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 or operated in a specific orientation, and cannot be understood as a limitation on the present invention.

[0033] In the description of the present utility model, "several" means one or more, "more" means two or more, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0034] 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.

[0035] The above-mentioned implementation modes are only preferred implementation modes of the present invention, and cannot be used to limit the protection scope of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A capacitor charging and discharging circuit, characterized in that: include: Several supercapacitors; A negative temperature coefficient sensing circuit is provided on one side of the supercapacitor and is used to detect the ambient temperature around the supercapacitor; A conversion circuit, whose input end is connected to the output end of the negative temperature coefficient sensor circuit, and is used to convert the electrical signal output by the negative temperature coefficient sensor circuit into a corresponding temperature feedback signal; A discharge control circuit, wherein the input end is connected to the supercapacitor and the output end is connected to the load; A control signal conversion circuit, whose input end is connected to the output end of the conversion circuit, and is used to convert the temperature feedback signal output by the conversion circuit into a corresponding control voltage; A charging control circuit, wherein the input end is connected to the input power supply, the output end is connected to the super capacitor, and the control end is connected to the output end of the control signal conversion circuit, and is used to control the charging voltage charged to the super capacitor according to the control voltage.

2. The capacitor charging and discharging circuit according to claim 1, characterized in that: The negative temperature coefficient sensing circuit comprises: A temperature measuring transistor, with an emitter grounded and a base connected to a working voltage, is arranged on one side of the supercapacitor, and a collector connected to an input end of the conversion circuit; A constant current source, whose output end is connected to the collector of the temperature measuring transistor, is used to provide a specific current to the collector of the temperature measuring transistor so that the base-emitter conduction voltage of the temperature measuring transistor has temperature dependence.

3. The capacitor charging and discharging circuit according to claim 2, characterized in that: The conversion circuit includes a follower circuit and an amplifier circuit. The input end of the follower circuit is connected to the collector of the temperature measuring transistor, the output end of the follower circuit is connected to the input end of the amplifier circuit, and the output end of the amplifier circuit is connected to the input end of the control signal conversion circuit as the output end of the conversion circuit.

4. The capacitor charging and discharging circuit according to claim 2, characterized in that: The constant current source includes a voltage stabilizing chip U2, a transistor Q1 and a plurality of resistors. The input pin of the voltage stabilizing chip U2 is connected to the working voltage through the resistor R5, the output end of the voltage stabilizing chip U2 is connected to the base and collector of the temperature measuring transistor Q3, the reference end of the voltage stabilizing chip U2 is connected to the emitter of the transistor Q1, the collector of the transistor Q1 is connected to the working voltage, the base of the transistor Q1 is connected to the working voltage through the resistor R5, and the emitter of the transistor Q1 is connected to the collector of the temperature measuring transistor Q3 through the resistor R10.

5. The capacitor charging and discharging circuit according to claim 3, characterized in that: The amplifier circuit of the conversion circuit is a reverse offset amplifier circuit.

6. The capacitor charging and discharging circuit according to claim 3, characterized in that: The amplifying circuit includes a voltage stabilizing chip U3, a transistor Q2, an operational amplifier U1 B, a plurality of resistors and capacitors, the input end of the voltage stabilizing chip U3 is connected to the working voltage through a resistor R6, the output end of the voltage stabilizing chip U3 is connected to the non-inverting input end of the operational amplifier U1 B, the reference end of the voltage stabilizing chip U3 is connected to the emitter of the transistor Q1, the emitter of the transistor Q2 is connected to the non-inverting input end of the operational amplifier U1 B through a resistor R11, the collector of the transistor Q2 is connected to the working voltage, the base of the transistor Q2 is connected to the input end of the voltage stabilizing chip U3, the inverting input end of the operational amplifier U1 B is connected to the output end of the follower circuit through a resistor R2, the inverting input end of the operational amplifier U1 B is connected to its output end through a resistor R1, the non-inverting input end of the operational amplifier U1 B is grounded through a resistor R3, the non-inverting input end of the operational amplifier U1 B is grounded through a resistor R4, and the output end of the operational amplifier U1 B is connected to the control end of the charging control circuit as the output end of the amplifying circuit.

7. The capacitor charging and discharging circuit according to claim 1, characterized in that: The charging control circuit includes a transistor Q4, an operational amplifier U5B and a plurality of resistors. The non-inverting input terminal of the operational amplifier U5B is connected to the output terminal of the control signal conversion circuit through a resistor R16, the non-inverting input terminal of the operational amplifier U5B is grounded through a resistor R19, the inverting input terminal of the operational amplifier U5B is grounded through a resistor R24, the inverting input terminal of the operational amplifier U5B is connected to the super capacitor through a resistor R21, the output terminal of the operational amplifier U5B is connected to the base of the transistor Q4 through a resistor R17, the collector of the transistor Q4 is connected to the working voltage, the emitter of the transistor Q4 is grounded through a resistor R25, the emitter of the transistor Q4 is connected to the super capacitor through a resistor R20, and a resistor R23 is connected in parallel at both ends of the resistor R20.

8. The capacitor charging and discharging circuit according to claim 1, characterized in that: The discharge control circuit includes an operational amplifier U5A, a transistor Q5 and several resistors. The non-inverting input terminal of the operational amplifier U5A is connected to the working voltage through the resistor R15, the inverting input terminal of the operational amplifier U5A is connected to the super capacitor, the output terminal of the operational amplifier U5A is connected to the super capacitor through the resistor R18 and the resistor R22, the output terminal of the operational amplifier U5A is connected to the gate of the transistor Q5, the source of the transistor Q5 is connected to the super capacitor, and the drain of the transistor Q5 is connected to the load.

9. The capacitor charging and discharging circuit according to claim 1, characterized in that: The control signal conversion circuit includes an operational amplifier U4A, a plurality of resistors and capacitors. The output end of the operational amplifier U4A is connected to the control end of the charging control circuit as the output end of the control signal conversion circuit. The output end of the operational amplifier U4A is connected to its inverting input end through a resistor R7. The inverting input end of the operational amplifier U4A is connected to the output end of the conversion circuit through a resistor R8. The non-inverting input end of the operational amplifier U4A is grounded through a resistor R14. The non-inverting input end of the operational amplifier U4A is grounded through resistors R12 and R13. Capacitor C7 is connected in parallel at both ends of the resistor R13. The connection node between the resistor R12 and the resistor R13 is connected to the working voltage through a resistor R9.

10. An Internet of Things device, characterized in that: The invention comprises a capacitor charging and discharging circuit according to any one of claims 1 to 8.

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