Capacitance measuring method and device and integrated circuit
By using a mirror current source to charge the external capacitor to be measured in the capacitance measurement system, the existing system circuit is complicated, costly, high power consumption and low measurement accuracy are solved, and capacitance detection with low complexity, low power consumption and high precision is achieved.
Patent Information
- Application Number
- CN202311642573.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-01
- Publication Date
- 2025-06-03
AI Technical Summary
The existing capacitance measurement system has complex circuits, high cost, high power consumption and low measurement accuracy, making it difficult to meet the needs of passive, low-cost, and non-contact measurements.
Through a capacitance measurement method and device, the external capacitor to be measured is charged using a mirror current source, and the relationship between the two is determined based on the preset time and the charging time, so as to achieve low complexity, low power consumption and high precision capacitance detection.
Reduces circuit design complexity and cost, reduces power consumption, improves measurement accuracy, is suitable for a variety of application scenarios, and realizes contactless and passive capacitance measurement.
Smart Images
Figure CN120085070A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of capacitance measurement, and particularly to a capacitance measurement method, device and integrated circuit. Background Art
[0002] RFID (Radio Frequency Identification) technology is a non-contact radio frequency identification technology that uses the spatial coupling of radio frequency signals to realize the identification of the identity of objects. RFID technology mainly works in low-frequency bands such as 125KHz, high-frequency bands such as 13.56MHz, ultra-high-frequency bands such as 900MHz, 2.4G bands, etc. In recent years, there has been an increasingly obvious trend for RFID technology to be combined with sensing and measurement. The combination of RFID technology and capacitance measurement has some unique advantages. Compared with traditional capacitance measurement systems, RFID-based capacitance measurement systems have advantages such as non-contact measurement, passive, low cost, and simple solutions. RFID-based capacitance measurement systems have very wide applications, especially in some application scenarios that require passive, low cost, non-contact measurement, such as liquid level measurement in washing machines. However, existing measurement solutions usually have a relatively complex circuit, high cost, are not conducive to power consumption control, and have low measurement accuracy. Summary of the Invention
[0003] Embodiments of the present invention provide a capacitance measurement method, device and integrated circuit, which can achieve low-cost, extremely low-power and higher-precision capacitance detection with a circuit design of relatively low complexity.
[0004] On the one hand, embodiments of the present invention provide a capacitance measurement method, and the method includes:
[0005] When performing measurement, first use a second current source to charge the external capacitance to be measured;
[0006] After reaching a preset time, start a first current source to charge an internal capacitance;
[0007] When the external capacitance to be measured and the internal capacitance reach the same voltage, stop charging and determine the charging time of the internal capacitance;
[0008] Determine the relationship between the external capacitance to be measured and the internal capacitance according to the preset time and the charging time of the internal capacitance.
[0009] Optionally, the first current source and the second current source are mirror current sources.
[0010] Optionally, any one of the first current source and the second current source is a constant current source, and the other is an adjustable current source.
[0011] Optionally, the method further includes: before measurement, performing a calibration operation, where the calibration operation includes any one or more of the following:
[0012] Adjusting the magnitude of the adjustable current source and / or the magnitude of the preset time, such that the difference between the preset time and the charging time of the internal capacitor is less than a set difference, and / or such that the voltage value at which the external capacitor under test and the internal capacitor reach the same voltage is a set value; or
[0013] Setting and adjusting the magnitude of an internal adjustable capacitor connected in parallel with the external capacitor under test, such that the charging slope of the external capacitor under test is less than the charging slope of the internal capacitor.
[0014] Optionally, the method further includes: determining the capacitance value of the external capacitor under test according to the capacitance value of the internal capacitor, the relationship between the first current source and the second current source, the preset time, and the charging time of the internal capacitor.
[0015] On the other hand, an embodiment of the present invention further provides a capacitance measurement device, the device including: an internal capacitor, a control module, a charging module, a voltage comparator, and a timing module respectively connected to the control module, and a first connection end and a second connection end for connecting the two ends of the external capacitor under test; the charging module includes: a first current source and a second current source; the control module is configured to, when performing measurement, trigger the second current source to charge the external capacitor under test, and at the same time trigger the timing module to start timing; after the timing reaches the preset time, trigger the first current source to charge the internal capacitor, and trigger the timing module to start timing again;
[0016] The timing module is configured to start or stop timing according to the trigger of the control module, and transmit the timing time to the control module;
[0017] The voltage comparator is configured to detect the charging voltage of the external capacitor under test and the charging voltage of the internal capacitor, and when the two are the same, send an indication signal to the control module;
[0018] The control module is further configured to determine the charging time of the internal capacitor according to the indication signal; and determine the relationship between the external capacitor under test and the internal capacitor according to the preset time and the charging time of the internal capacitor.
[0019] Optionally, the first current source and the second current source are mirror current sources.
[0020] Optionally, any one of the first current source and the second current source is a constant current source, and the other is an adjustable current source.
[0021] Optionally, the device further includes:
[0022] A first discharge switch, controlled by the control module to discharge the internal capacitor after the measurement ends;
[0023] A second discharge switch, controlled by the control module to discharge the external capacitor to be measured after the measurement ends.
[0024] Optionally, the control module is further configured to, before performing the measurement, adjust the magnitude of the adjustable current source and / or the value of the preset time, so that the difference between the preset time and the charging time of the internal capacitor is less than a set difference, and / or so that the voltage values of the external capacitor to be measured and the internal capacitor reach a set value.
[0025] Optionally, the device further includes: an internal adjustable capacitor disposed between the first connection end and the second connection end;
[0026] The control module is further configured to, before performing the measurement, adjust the magnitude of the internal adjustable capacitor, so that the charging slope of the external capacitor to be measured is less than the charging slope of the internal capacitor.
[0027] Optionally, the control module is further configured to determine the capacitance value of the external capacitor to be measured according to the capacitance value of the internal capacitor, the relationship between the first current source and the second current source, the preset time, and the charging time of the internal capacitor.
[0028] On the other hand, an embodiment of the present invention further provides an integrated circuit, which includes: an RFID communication module, an energy acquisition module, a clock module, and a capacitance measurement device according to any one of claims 6 to 12;
[0029] The RFID communication module is configured to perform data transmission, including receiving measurement indication information, triggering the capacitance measurement device to measure the external capacitor to be measured, and receiving and uploading the measurement result information output by the capacitance measurement device;
[0030] The energy acquisition module is configured to obtain energy from the RFID communication module to supply power to the capacitance measurement device;
[0031] The clock module is configured to provide a working clock for the capacitance measurement device;
[0032] The capacitance measurement device is configured to measure the external capacitor to be measured after the RFID communication module receives the measurement indication information, and send the measured value of the external capacitor to be measured as the measurement result information to the RFID communication module.
[0033] Optionally, the clock module includes: a clock recovery unit configured to recover an external clock signal from the data signal received by the RFID communication module and use the external clock as the operating clock.
[0034] Optionally, the clock module includes: an internal clock generation unit configured to generate an internal clock as the operating clock.
[0035] In the capacitance measurement method, device, and integrated circuit provided by the embodiments of the present invention, when measuring an external content to be measured, first charge the external capacitance to be measured; after reaching a preset time, start charging the internal capacitance; when the external capacitance to be measured and the internal capacitance reach the same voltage, stop charging, and determine the charging time of the internal capacitance; determine the relationship between the external capacitance to be measured and the internal capacitance according to the preset time and the charging time of the internal capacitance. Further, the capacitance value of the external capacitance to be measured can also be determined according to the capacitance value of the internal capacitance, the relationship between the first current source and the second current source, the preset time, and the charging time of the internal capacitance, so as to meet the measurement requirements in different application scenarios.
[0036] Compared with the traditional measurement scheme, the solution of the present invention saves complex devices such as analog-to-digital conversion devices and integrators, can reduce the complexity of circuit design, reduce circuit design costs and power consumption, and is more suitable for various application scenarios. Correspondingly, the integrated circuit provided by the embodiments of the present invention combines capacitance measurement with RFID technology, can realize non-contact capacitance measurement and passive capacitance measurement, and compared with other capacitance measurement systems, can be powered without an external power supply, has a simpler structure, better sealing performance, and lower cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Figure 1 is a flowchart of a capacitance measurement method provided by an embodiment of the present invention;
[0038] Figure 2 is a schematic diagram of the relationship between voltage and time of an internal capacitance and an external capacitance to be measured under current charging;
[0039] Figure 3 is a schematic structural diagram of a capacitance measurement device provided by an embodiment of the present invention;
[0040] Figure 4 is a schematic structural diagram of an integrated circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0041] The principles and spirit of the present invention will be described below with reference to the exemplary embodiments shown in the drawings. It should be understood that these embodiments are described only to enable those skilled in the art to better understand and implement the present invention, and do not limit the scope of the present invention in any way.
[0042] As Figure 1 shown, it is a flowchart of a capacitance measurement method provided by an embodiment of the present invention. The method includes the following steps:
[0043] Step 101, when performing measurement, first charge the external capacitance to be measured by using a second current source.
[0044] Step 102, after reaching the preset time T PRE , start charging the internal capacitance by using a first current source.
[0045] Step 103, when the external capacitance to be measured and the internal capacitance reach the same voltage U X , stop charging and determine the charging time T DET of the internal capacitance.
[0046] Step 104, determine the relationship between the external capacitance to be measured and the internal capacitance according to the preset time T PRE and the charging time T DET of the internal capacitance.
[0047] Furthermore, the capacitance value of the external capacitance to be measured can also be determined according to the capacitance value of the internal capacitance, the relationship between the first current source and the second current source, the preset time, and the charging time of the internal capacitance.
[0048] Next, the measurement principle will be described in detail in conjunction with Figure 2 .
[0049] Referring to Figure 2 , Figure 2 shows the relationship between voltage and time of the internal capacitance and the external capacitance to be measured under current charging.
[0050] The static and dynamic calculation formulas of capacitance are as follows:
[0051]
[0052]
[0053] Among them, C is the capacitance, Q is the electric charge stored in the capacitance, U is the voltage across the capacitance, and I is the charging current of the capacitance.
[0054] According to the above formulas and in conjunction with Figure 2 the shown relationship, it can be obtained that:
[0055] I EXT ×(T PRE +T DET ) = Q EXT = U X ×C EXT (3)
[0056] I INT ×T DET =Q INT =U X ×C INT (4)
[0057] Among them, Q EXT represents the electric quantity stored in the external capacitor to be measured, I EXT represents the charging current of the external capacitor to be measured, C EXT represents the capacitance of the external capacitor to be measured; Q INT represents the electric quantity stored in the internal capacitor, I INT represents the charging current of the internal capacitor, C INT represents the capacitance of the internal capacitor; U X represents the same voltage reached by the external capacitor to be measured and the internal capacitor.
[0058] According to the above formulas (3) and (4), it can be obtained that: C INT
[0059]
[0060]
[0061] As can be seen from the above formula (6), when the capacitance C of the internal capacitor INT , the charging current I of the external capacitor to be measured EXT , and the charging current I of the internal capacitor INT are determined, according to the above preset time T PRE and the current charging time T of the internal capacitor DET , the measured value of the external capacitor to be measured can be calculated.
[0062] Moreover, by precisely calibrating the value of C INT , the accuracy of the measured value of the external capacitor to be measured can be improved.
[0063] In the embodiments of the present invention, different current sources are used to charge the external capacitor to be measured and the internal capacitor respectively.
[0064] Furthermore, for the convenience of calculation, the design of a mirror current source can also be adopted, that is, the first current source and the second current source are mirror current sources, so that I EXT and I INT are in a certain multiple relationship, and this multiple is relatively accurate.
[0065] Moreover, as can be seen from the above formula (5), in applications where it is not necessary to precisely know the exact capacitance value of the external capacitor to be measured, such as when only the change situation of the external capacitor to be measured relative to the internal capacitor needs to be known, directly through TPRE and T DET The value can reflect the relationship between the external capacitance to be measured and the internal capacitance, such as the ratio of the external capacitance to be measured to the internal capacitance.
[0066] In a specific application, any one of the first current source and the second current source can be a constant current source, and correspondingly, the other is an adjustable current source. In this way, it is convenient to adjust the multiple relationship.
[0067] Furthermore, to ensure that the charging curves of the internal capacitance and the external capacitance to be measured must intersect, it is necessary to ensure that the slope of the charging curve of the internal capacitance is greater than the slope of the charging curve of the external capacitance to be measured. For this purpose, in another non-limiting embodiment, a calibration operation can also be performed before measurement.
[0068] The calibration operation can include any one or more of the following:
[0069] (1) Adjust the magnitude of the adjustable current source so that the preset time T PRE and the current charging time T DET of the internal capacitance have a difference less than a set difference, and / or make the values U X of the external capacitance to be measured and the internal capacitance reach the same voltage, for example, near the midpoint of the operating voltage of the voltage comparator 303.
[0070] (2) Set and adjust the magnitude of the internal adjustable capacitance connected in parallel with the external capacitance to be measured so that the charging slope of the external capacitance to be measured is less than the charging slope of the internal capacitance.
[0071] Of course, in some specific application scenarios, for example, when the capacitance value of the external capacitance to be measured is within a small range, in this case, the multiple relationship of the two charging currents can be set according to empirical values, and there is no need for a calibration process before measurement.
[0072] Correspondingly, an embodiment of the present invention further provides a capacitance measurement device, as Figure 3 shown, which is a schematic structural diagram of the device.
[0073] Referring to Figure 3 , the capacitance measurement device 300 includes: an internal capacitance C INT , a control module 301, a charging module 302, a voltage comparator 303, a timing module 304 respectively connected to the control module 301, and a first connection end A and a second connection end B for connecting the two ends of the external capacitance to be measured. Among them, the charging module 302 includes: a first current source and a second current source. In this embodiment:
[0074] The control module 301 is used to trigger the second current source in the charging module 302 to charge the external capacitor C to be measured, and at the same time trigger the timing module 304 to start timing; when the timing reaches the preset time T, trigger the first current source in the charging module 302 to charge the internal capacitor C, and trigger the timing module 304 to start timing again; EXT After that, trigger the first current source in the charging module 302 to charge the internal capacitor C, and trigger the timing module 304 to start timing again; PRE After that, trigger the first current source in the charging module 302 to charge the internal capacitor C INT And trigger the timing module 304 to start timing again;
[0075] The timing module 304 is used to start or stop timing according to the trigger of the control module 301, and transmit the timing time to the control module 301;
[0076] The voltage comparator 303 is used to detect the charging voltage of the external capacitor C to be measured and the charging voltage of the internal capacitor C. When the two are the same, send an indication signal to the control module 301. EXT The charging voltage of the external capacitor C to be measured and the charging voltage of the internal capacitor C INT When the two are the same, send an indication signal to the control module 301.
[0077] Correspondingly, the control module 301 is further used to determine the charging time T of the internal capacitor C according to the indication signal; determine the relationship between the external capacitor to be measured and the internal capacitor C according to the preset time T and the charging time T of the internal capacitor C. INT The charging time T of the internal capacitor C DET According to the preset time T PRE And the internal capacitor C INT The charging time T of the internal capacitor C DET Determine the relationship between the external capacitor to be measured and the internal capacitor C INT Relationship.
[0078] The above timing module 304 can time according to the internal clock of the control module 301.
[0079] The first current source and the second current source can be mirror current sources. As shown in, they can be mirror current sources from the same power supply; moreover, any one of the first current source and the second current source is a constant current source, and the other is an adjustable current source. In this way, the measurement value can be made more accurate. In addition, since the mirror current sources can be set to a certain multiple relationship, in applications where it is not necessary to accurately know the exact capacitance value of the external capacitor to be measured, the ratio of the external capacitor to be measured and the internal capacitor can also be directly reflected by the values of T and T, making the measurement simpler and more efficient. Figure 3 As shown in, they can be mirror current sources from the same power supply; moreover, any one of the first current source and the second current source is a constant current source, and the other is an adjustable current source. In this way, the measurement value can be made more accurate. In addition, since the mirror current sources can be set to a certain multiple relationship, in applications where it is not necessary to accurately know the exact capacitance value of the external capacitor to be measured, the ratio of the external capacitor to be measured and the internal capacitor can also be directly reflected by the values of T and T, making the measurement simpler and more efficient. PRE And T DET Values can reflect the ratio of the external capacitor to be measured and the internal capacitor, making the measurement simpler and more efficient.
[0080] Furthermore, as shown in, the capacitance measuring device 300 may further include: a first discharge switch K1 and a second discharge switch K2. Among them, the first discharge switch K1 is controlled by the control module 301 to discharge the internal capacitor C after the measurement; the second discharge switch K2 is controlled by the control module 301 to discharge the external capacitor C to be measured after the measurement Figure 3 As shown in, the capacitance measuring device 300 may further include: a first discharge switch K1 and a second discharge switch K2. Among them, the first discharge switch K1 is controlled by the control module 301 to discharge the internal capacitor C after the measurement; the second discharge switch K2 is controlled by the control module 301 to discharge the external capacitor C to be measured after the measurement INT Discharge; the second discharge switch K2 is controlled by the control module 301 to discharge the external capacitor C to be measured after the measurementEXT Discharge. Specifically, after the measurement is completed, the control module 301 controls the first discharge switch to close, short-circuiting both ends of the internal capacitor C INT to be connected to the ground, thereby realizing the discharge of the internal capacitor C INT .
[0081] Furthermore, in order to ensure that the charging curves of the internal capacitor and the external capacitor to be measured must intersect, it is necessary to ensure that the slope of the charging curve of the internal capacitor is greater than the slope of the charging curve of the external capacitor to be measured. For this purpose, in another non-limiting embodiment, a calibration operation can also be performed before the measurement.
[0082] Correspondingly, in a non-limiting embodiment, the control module 301 can adjust the magnitude of the adjustable current source and / or the value of the preset time before the measurement, so that the preset time T PRE and the charging time T of the internal capacitor DET have a difference less than a set difference, and / or make the external capacitor to be measured and the internal capacitor reach the same voltage value U X as a set value.
[0083] In another non-limiting embodiment, as Figure 3 shown, an internal adjustable capacitor C1 can also be provided between the first connection end A and the second connection end B. Before the measurement, the control module 301 adjusts the magnitude of the internal adjustable capacitor C1 so that the charging slope of the external capacitor C to be measured EXT is less than the charging slope of the internal capacitor C INT .
[0084] Correspondingly, after the measurement is completed, the second discharge switch K2 can discharge the internal adjustable capacitor C1 and the external capacitor C to be measured EXT simultaneously.
[0085] When measuring the external content to be measured, the capacitance measurement method, device, and integrated circuit provided by the embodiments of the present invention first charge the external capacitor to be measured; after reaching the preset time, start charging the internal capacitor; when the external capacitor to be measured and the internal capacitor reach the same voltage, stop charging, and determine the charging time of the internal capacitor; determine the relationship between the external capacitor to be measured and the internal capacitor according to the preset time and the charging time of the internal capacitor.
[0086] Compared with the traditional measurement scheme, the solution of the present invention saves complex devices such as analog-to-digital conversion devices and integrators, can reduce the complexity of circuit design, reduce circuit design costs and power consumption, and can be better and more suitable for various application scenarios.
[0087] Accordingly, an embodiment of the present invention further provides an integrated circuit, which combines capacitance measurement with RFID technology, can achieve non-contact capacitance measurement and passive capacitance measurement. Compared with other capacitance measurement systems, it can be powered without external power supply, has a simpler structure, better sealing performance, and lower cost.
[0088] As Figure 4 shown, it is a schematic structural diagram of an integrated circuit provided by an embodiment of the present invention.
[0089] The integrated circuit 400 includes: an RFID communication module 401, an energy acquisition module 402, a clock module 403, and the capacitance measurement device described above. Among them:
[0090] The RFID communication module 401 is used for data transmission, including receiving measurement instruction information, triggering the capacitance measurement device to measure the external capacitance C to be measured EXT and receiving and uploading the measurement result information output by the capacitance measurement device;
[0091] The energy acquisition module 402 is used to obtain energy from the RFID communication module 401 to power the capacitance measurement device;
[0092] The clock module 403 is used to provide a working clock for the capacitance measurement device.
[0093] The capacitance measurement device is configured to measure the external capacitance to be measured after the RFID communication module 401 receives the measurement instruction information, and use the measurement value of the external capacitance C to be measured EXT as the measurement result information and send it to the RFID communication module 401.
[0094] In a non-limiting embodiment, the clock module 403 may include: a clock recovery unit, which is used to recover an external clock signal from the data signal received by the RFID communication module and use the external clock as the working clock.
[0095] In another non-limiting embodiment, the clock module 403 may include: an internal clock unit, which is used to generate an internal clock as the working clock. In this case, the internal clock unit may be set in the control module 301 or may be independent of the control module 301, and the present invention does not make any limitations in this regard.
[0096] As Figure 4 shown, in a specific application, the above integrated circuit 400 may further include an RFID antenna, which is connected to the RFID communication module 401 to perform signal transmission between the RFID communication module 401 and the measurement system.
[0097] Transmit the signal between the RFID tag and the reader:
[0098] The integrated circuit provided by the embodiment of the present invention combines capacitance measurement with RFID technology, and can realize non-contact capacitance measurement and passive capacitance measurement. For example, for a capacitance set in a pipeline or a complex environment, the above integrated circuit is used as the RFID tag of the capacitance, and the capacitance can be measured by reading the RFID tag through a measurement system with an RFID reader.
[0099] In specific implementation, for each device and product described in the above embodiments, each module / unit included therein can be a software module / unit, a hardware module / unit, or can be partially a software module / unit and partially a hardware module / unit.
[0100] For example, for each device and product applied to or integrated into a chip, each module / unit included therein can be implemented in the form of hardware such as circuits. Or at least some of the modules / units can be implemented in the form of software programs, and the software programs run on the processor integrated inside the chip. The remaining (if any) part of the modules / units can be implemented in the form of hardware such as circuits; for each device and product applied to or integrated into a chip module, each module / unit included therein can be implemented in the form of hardware such as circuits. Different modules / units can be located in the same component (such as a chip, a circuit module, etc.) or different components of the chip module. Or at least some of the modules / units can be implemented in the form of software programs, and the software programs run on the processor integrated inside the chip module. The remaining (if any) part of the modules / units can be implemented in the form of hardware such as circuits; for each device and product applied to or integrated into a terminal, each module / unit included therein can be implemented in the form of hardware such as circuits. Different modules / units can be located in the same component (such as a chip, a circuit module, etc.) or different components inside the terminal. Or at least some of the modules / units can be implemented in the form of software programs, and the software programs run on the processor integrated inside the terminal. The remaining (if any) part of the modules / units can be implemented in the form of hardware such as circuits.
[0101] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.
Claims
1. A capacitance measurement method, characterized in that, the method comprises: when measuring, first use a second current source to charge the external capacitance to be measured; after reaching a preset time, start a first current source to charge the internal capacitance; when the external capacitance to be measured and the internal capacitance reach the same voltage, stop charging and determine the charging time of the internal capacitance; determine the relationship between the external capacitance to be measured and the internal capacitance according to the preset time and the charging time of the internal capacitance.
2. The capacitance measurement method according to claim 1, characterized in that, the first current source and the second current source are mirror current sources.
3. The capacitance measurement method according to claim 2, characterized in that, any one of the first current source and the second current source is a constant current source, and the other is an adjustable current source.
4. The capacitance measurement method according to claim 3, characterized in that, the method further comprises: before measuring, performing a calibration operation, and the calibration operation includes any one or more of the following: adjust the magnitude of the adjustable current source and / or the magnitude of the preset time, so that the difference between the preset time and the charging time of the internal capacitance is less than a set difference, and / or the value of the voltage when the external capacitance to be measured and the internal capacitance reach the same voltage is a set value; or set and adjust the magnitude of the internal adjustable capacitance connected in parallel with the external capacitance to be measured, so that the charging slope of the external capacitance to be measured is less than the charging slope of the internal capacitance.
5. The capacitance measurement method according to any one of claims 1 to 4, characterized in that, the method further comprises: determine the capacitance value of the external capacitance to be measured according to the capacitance value of the internal capacitance, the relationship between the first current source and the second current source, the preset time and the charging time of the internal capacitance.
6. A capacitance measurement device, characterized in that, the device comprises: an internal capacitance, a control module, a charging module, a voltage comparator, a timing module respectively connected to the control module, and a first connection end and a second connection end for connecting both ends of the external capacitance to be measured; the charging module comprises: a first current source and a second current source; the control module is used for, when measuring, triggering the second current source to charge the external capacitance to be measured, and simultaneously triggering the timing module to start timing; after the timing reaches the preset time, triggering the first current source to charge the internal capacitance, and triggering the timing module to start timing again; the timing module is used for starting or stopping timing according to the trigger of the control module, and transmitting the timing time to the control module; the voltage comparator is used for detecting the charging voltage of the external capacitance to be measured and the charging voltage of the internal capacitance, and when the two are the same, sending an indication signal to the control module; the control module is further used for determining the charging time of the internal capacitance according to the indication signal; and determining the relationship between the external capacitance to be measured and the internal capacitance according to the preset time and the charging time of the internal capacitance.
7. The device according to claim 6, characterized in that, The first current source and the second current source are mirror current sources.
8. The device according to claim 7, wherein, either the first current source or the second current source is a constant current source, and the other is an adjustable current source.
9. The device according to claim 6, wherein, the device further comprises: a first discharge switch, controlled by the control module to discharge the internal capacitor after the measurement ends; a second discharge switch, controlled by the control module to discharge the external capacitor to be measured after the measurement ends.
10. The device according to claim 8, wherein, the control module is further configured to, before the measurement, adjust the magnitude of the adjustable current source and / or the value of the preset time, so that the difference between the preset time and the charging time of the internal capacitor is less than a set difference, and / or so that the voltage values of the external capacitor to be measured and the internal capacitor reach the same set value.
11. The device according to claim 8, wherein, the device further comprises: an internal adjustable capacitor disposed between the first connection end and the second connection end; the control module is further configured to, before the measurement, adjust the magnitude of the internal adjustable capacitor, so that the charging slope of the external capacitor to be measured is less than the charging slope of the internal capacitor.
12. The device according to any one of claims 6 to 11, wherein, the control module is further configured to determine the capacitance value of the external capacitor to be measured according to the capacitance value of the internal capacitor, the relationship between the first current source and the second current source, the preset time, and the charging time of the internal capacitor.
13. An integrated circuit, wherein, the integrated circuit comprises: an RFID communication module, an energy acquisition module, a clock module, and the capacitance measurement device according to any one of claims 6 to 12; the RFID communication module is configured to perform data transmission, including receiving measurement indication information, triggering the capacitance measurement device to measure the external capacitor to be measured, and receiving and uploading the measurement result information output by the capacitance measurement device; the energy acquisition module is configured to obtain energy from the RFID communication module to supply power to the capacitance measurement device; the clock module is configured to provide a working clock for the capacitance measurement device; the capacitance measurement device is configured to measure the external capacitor to be measured after the RFID communication module receives the measurement indication information, and send the measurement value of the external capacitor to be measured as the measurement result information to the RFID communication module.
14. The integrated circuit according to claim 13, wherein, the clock module comprises: a clock recovery unit, configured to recover an external clock signal from the data signal received by the RFID communication module, and use the external clock as the working clock.
15. The integrated circuit according to claim 13, wherein, the clock module comprises: an internal clock generation unit, configured to generate an internal clock as the working clock.