Capacitance detection circuit and capacitance detection method

Abstract

The invention provides a capacitance detection circuit and a capacitance detection method. The capacitance detection circuit comprises a constant voltage measurement module, a fixed time measurement module and a mode selection module. The constant voltage measurement module is used for measuring the charging time of charging the capacitor to be measured from a first preset voltage to a second preset voltage so as to calculate the capacitance value of the capacitor to be measured; and the fixed-time measurement module is used for measuring a voltage difference value of the capacitor to be measured in a preset duration so as to calculate a capacitance value of the capacitor to be measured. And the mode selection module is used for switching one of the constant voltage measurement module and the fixed time measurement module to work. The capacitance detection method works based on the capacitance detection circuit. According to the configuration, different measuring range gears are set, and different measuring modes are set at different gears, so that capacitors with different capacitance values can be coped with, the precision and the response speed are relatively high, and the self-adaptive capability is high; therefore, the problems in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitance detection, and in particular to a capacitance detection circuit and a capacitance detection method. Background Art

[0002] With the rapid development of information technology, the functions of electronic equipment are becoming increasingly diverse and complex. As a key component, the performance parameters of capacitors are crucial to the normal operation of the entire electronic system. Capacitors not only play an important role in power management, signal processing, oscillator design, decoupling and noise suppression, but are also indispensable in touch screen technology, sensor technology, medical equipment and other fields. Therefore, the capacitance measurement of capacitors has become a basic and critical step in the process of electronic manufacturing and maintenance.

[0003] At present, the more common method of multimeter capacitance detection is to first convert the capacitance to be measured into a frequency quantity, then measure the frequency, and then convert the external capacitance into a digital signal, which can be used for other operations and processing. However, this method is limited by the range and accuracy of frequency measurement, and often takes a long time to measure when measuring large capacitance. When measuring capacitance, it is usually necessary to turn the dial to manually adjust the multimeter to switch different ranges.

[0004] In summary, when measuring capacitance values ​​using a multimeter in the prior art, there are problems such as unsatisfactory accuracy, range, response speed and adaptive performance. Summary of the invention

[0005] The object of the present invention is to provide a capacitance detection circuit and a capacitance detection method to solve the problem that the accuracy, range, response speed and adaptive performance of the multimeter in the prior art are not ideal when measuring the capacitance value.

[0006] In order to solve the above technical problems, the present invention provides a capacitance detection circuit, which includes a constant voltage measurement module, a constant time measurement module and a mode selection module; the constant voltage measurement module is used to measure the charging time of a capacitor to be measured from a first preset voltage to a second preset voltage, and the charging time is used to calculate the capacitance value of the capacitor to be measured; the constant time measurement module is used to measure the voltage difference of the capacitor to be measured within a preset time length, and the voltage difference is used to calculate the capacitance value of the capacitor to be measured; the mode selection module is used to switch one of the constant voltage measurement module and the constant time measurement module to work.

[0007] Optionally, the capacitance detection circuit further includes a charging and discharging module, which includes at least two constant current sources, and the charging and discharging module provides at least two different constant charging currents based on switching the connection relationship between the constant current source and the capacitor to be measured.

[0008] Optionally, the constant voltage measurement module includes a window comparison unit and a time digital converter, the window comparison unit is used to drive the time digital converter to count when the voltage of the capacitor to be measured rises from the first preset voltage to the second preset voltage time period, and not drive the time digital converter to count in other cases; the time digital converter is used to convert the total duration of its own counting into a time counting signal output, so as to calculate the capacitance value of the capacitor to be measured.

[0009] Optionally, the time measurement module includes an analog-to-digital converter, which is used to measure the voltage of the capacitor to be measured at a first trigger time point and a second trigger time point and convert it into a first sampling signal and a second sampling signal output to facilitate calculation of the capacitance value of the capacitor to be measured; the interval between the first trigger time point and the second trigger time point is the preset duration.

[0010] In order to solve the above technical problems, the present invention further provides a capacitance detection method, which is applied to a capacitance detection circuit, wherein the capacitance detection circuit includes a constant voltage measurement module and a constant time measurement module; the capacitance detection method includes:

[0011] Determining a capacitance gear, wherein the capacitance gear includes a low capacitance gear and a high capacitance gear;

[0012] If the capacitance gear is the low capacitance gear, outputting a control signal to drive the constant voltage measurement module to measure the charging time of the capacitor to be measured from the first preset voltage to the second preset voltage, and calculating the capacitance value of the capacitor to be measured based on the charging time; and

[0013] If the capacitance position is the high capacitance position, the output control signal drives the time measurement module to measure the voltage difference of the capacitor to be measured within a preset time period, and calculate the capacitance value of the capacitor to be measured based on the voltage difference.

[0014] Optionally, the capacitance detection circuit further includes a charge and discharge module, and the charge and discharge module includes at least two constant current sources; and the capacitance detection method includes:

[0015] The connection relationship between the constant current source and the capacitor to be measured is switched based on the capacitor gear output control signal, so that the charging current of the capacitor is different in at least two different capacitor gears.

[0016] Optionally, the constant voltage measurement module includes a window comparison unit and a time-to-digital converter.

[0017] The capacitance detection method comprises:

[0018] When the capacitance gear is the low capacitance gear, when the voltage of the capacitor to be measured rises from the first preset voltage to the second preset voltage, the window comparison unit drives the time-to-digital converter to count, and does not drive the time-to-digital converter to count in other cases.

[0019] The time-to-digital converter converts the total duration of its own counting into a time counting signal.

[0020] Calculate the capacitance value of the capacitor to be measured based on the following formula:

[0021]

[0022] Wherein, C represents the capacitance value of the capacitor to be measured, I represents the charging current, counter represents the time counting signal, F represents the counting frequency of the time-to-digital converter, VH_th represents the second preset voltage, and VL_th represents the first preset voltage.

[0023] Optionally, the timing measurement module includes an analog-to-digital converter.

[0024] The capacitance detection method comprises:

[0025] When the capacitance gear is the high capacitance gear, the analog-to-digital converter is used to measure the voltage of the capacitor to be measured at a first trigger time point and a second trigger time point and convert it into a first sampling signal and a second sampling signal; the interval between the first trigger time point and the second trigger time point is the preset duration.

[0026] Calculate the capacitance value of the capacitor to be measured based on the following formula:

[0027]

[0028] Wherein, C represents the capacitance value of the capacitor to be measured, I represents the charging current, T represents the preset time, adc2 represents the second sampling signal, adc1 represents the first sampling signal, N represents the number of bits of the analog-to-digital converter, V REF Represents the reference voltage of the analog-to-digital converter.

[0029] Optionally, the step of determining the capacitor gear includes: starting from the lowest gear among the capacitor gears, and if the gears do not match, switching the gear upward once, wherein if the highest gear among the capacitor gears does not match, switching to the lowest gear among the capacitor gears.

[0030] The logic for determining whether the gears match includes:

[0031] When the capacitance gear is the low capacitance gear, if the voltage of the capacitor to be measured is not charged from the first preset voltage to the second preset voltage within the cut-off time, or the calculated final capacitance value exceeds the range of the current gear, it is judged that there is no match.

[0032] When the capacitance gear is the high capacitance gear, the calculated final capacitance value exceeds the range of the current gear, and it is determined that there is no match.

[0033] Optionally, the constant voltage measurement module includes a window comparison unit and a time digital converter, wherein the window comparison unit is used to drive the time digital converter to count when the voltage of the capacitor to be measured rises from the first preset voltage to the second preset voltage time period, and does not drive the time digital converter to count in other cases; the time digital converter is used to convert the total duration of its own counting into a time counting signal output, so as to calculate the capacitance value of the capacitor to be measured;

[0034] When the capacitance gear is the low capacitance gear, if the voltage of the capacitor to be tested is not charged from the first preset voltage to the second preset voltage within the cut-off time, it is determined that the gear does not match;

[0035] The preset parameters of the capacitor gear include: charging current, the first preset voltage, the second preset voltage, the preset duration, the cut-off duration and the counting frequency of the time-to-digital converter; in different capacitor gears, at least one of the preset parameters is different.

[0036] Compared with the prior art, the present invention provides a capacitance detection circuit and a capacitance detection method, wherein the capacitance detection circuit includes a constant voltage measurement module, a constant time measurement module and a mode selection module; the constant voltage measurement module is used to measure the charging time of the capacitor to be measured from a first preset voltage to a second preset voltage, and the charging time is used to calculate the capacitance value of the capacitor to be measured; the constant time measurement module is used to measure the voltage difference of the capacitor to be measured within a preset time length, and the voltage difference is used to calculate the capacitance value of the capacitor to be measured. The mode selection module is used to switch one of the constant voltage measurement module and the constant time measurement module to work. The capacitance detection method works based on the above-mentioned capacitance detection circuit. With such a configuration, by setting different range gears and setting different measurement methods at different gears, it can cope with capacitors with different capacitance values, and has high accuracy and response speed, and strong adaptability; thereby solving the problems existing in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0038] Figure 1 4 is a connection block diagram of a capacitance detection circuit according to an embodiment of the present invention.

[0039] Figure 2 is a circuit diagram of a capacitance detection circuit according to an embodiment of the present invention.

[0040] Figure 3 It is a flow chart of a method for automatic gear switching according to an embodiment of the present invention.

[0041] in:

[0042] 100-capacitance detection circuit; 200-capacitance to be measured; 1-constant voltage measurement module; 11-window comparison unit; time digital converter; 2-constant time measurement module; 21-analog-to-digital converter; 3-mode selection module; 4-charge and discharge module; 41-constant current source; 42-charge and discharge network; 5-processor. DETAILED DESCRIPTION

[0043] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0044] As used in the present invention, the singular forms "one", "an" and "the" include plural objects, the term "or" is generally used to include the meaning of "and / or", the term "several" is generally used to include the meaning of "at least one", and the term "at least two" is generally used to include the meaning of "two or more". In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "the proximal end" and "the distal end" generally refer to two corresponding parts, which include not only the endpoints, and the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. In addition, as used in the present invention, an element disposed on another element generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements may be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element may be in any orientation such as inside, outside, above, below or on one side of another element, unless otherwise clearly indicated in the content. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] The core idea of ​​the present invention is to provide a capacitance detection circuit and a capacitance detection method to solve the problem that the accuracy, range, response speed and adaptive performance of the multimeter in the prior art are not ideal when measuring the capacitance value.

[0046] The following description is given with reference to the accompanying drawings.

[0047] Please refer to Figure 1 This embodiment provides a fast, wide-range, and adaptive capacitance detection circuit 100. The capacitance detection circuit 100 includes a constant voltage measurement module 1, a constant time measurement module 2, a mode selection module 3, a charge and discharge module 4, and a processor 5.

[0048] The constant-voltage measurement module 1 is used to measure the charging time of the capacitor under test 200 from the first preset voltage to the second preset voltage. The charging time is used to calculate the capacitance value of the capacitor under test, and the specific calculation process will be introduced later. The constant-time measurement module 2 is used to measure the voltage difference of the capacitor under test 200 within a preset time period. The voltage difference is used to calculate the capacitance value of the capacitor under test, and the specific calculation process will be introduced later. The mode selection module 3 is used to switch the operation of one of the constant-voltage measurement module and the constant-time measurement module.

[0049] The capacitance detection circuit is configured to operate at multiple different capacitance ranges, and the measurement ranges of each capacitance range are different. Based on the above circuit structure, it can provide a hardware basis for the multi-range and multi-gear measurement method and can solve the problems existing in the prior art.

[0050] Specifically, the charge and discharge module 4 includes at least two constant current sources 41. The charge and discharge module provides at least two different constant charging currents by switching the connection relationship between the constant current source 41 and the capacitor under test 200.

[0051] Please refer to Figure 2 , in a specific embodiment, the charge and discharge module 4 includes the constant current source 41 and the charge and discharge network 42. The constant current source 41 is mirrored from the same current source by a mirror current source. In other embodiments, it can also be a constant current source generated based on other principles. In this embodiment, it specifically includes six mirror current sources, and the output currents are I1, I2, I3, I4, I5, and I6 respectively. I1 < I2 < I3 < I4 < I5 < I6, and there is a fixed proportional relationship between them. After calibrating a certain mirror current source, the current values of other mirror current sources can be known. Select the mirror current source I3 with the calibrated current value in the middle, and the current values of other current sources can all be represented by I3. The mirror current source generates the charging current of the capacitor under test.

[0052] The charge and discharge network 42 includes a discharge control switch K0 and charge control switches K1 to K6. When one of the charge control switches is closed and the others are open, the charging current of the capacitor under test can be controlled. It can be understood that the charging network can also be in other structural forms. The number of the constant current source and the charge control switches is not limited to 6 either.

[0053] The constant voltage measurement module 1 includes a window comparison unit 11 and a time digital converter 12. The window comparison unit 11 is used to drive the time digital converter 12 to count when the voltage of the capacitor 200 to be measured rises from the first preset voltage to the second preset voltage time period, and does not drive the time digital converter 12 to count in other cases; the time digital converter 12 is used to convert the total duration of its own counting into a time counting signal output, so as to facilitate the capacitance value of the capacitor to be measured.

[0054] Please continue to refer to Figure 2 In a specific embodiment, the window comparison unit 11 includes a first comparator CMP1, a second comparator CMP2, an XOR gate XOR, a first preset voltage multiplexer MUX1 and a second preset voltage multiplexer MUX2. MUX1 and MUX2 are used to change the specific values ​​of the first preset voltage VL_th and the second preset voltage VH_th at different capacitor positions. In this embodiment, both are 2-to-1 multiplexers. In other embodiments, they can also be other models such as 3-to-1 or 4-to-1, or any other electrical components or combinations that change the output voltage by changing their internal structures or electrical parameters. CMP1 and CMP2 compare the voltage of the capacitor 200 to be tested with the first preset voltage and the second preset voltage, respectively, and the comparison results are CMPLO and CMPHO, respectively. The output CMPO of the XOR gate is high when CMPLO and CMPHO are at different levels, and low when CMPLO and CMPHO are at the same level. The XOR gate XOR converts the charging time of the capacitor voltage to be tested between the low threshold and high threshold windows into a high-level output time. When K8 is closed, the time-to-digital converter (TDC) 12 starts timing when the output level of XOR is high, and stops timing when the output level of XOR switches to low.

[0055] It is understandable that in this embodiment, other logic is also provided to handle the problem of the time-to-digital converter 12 being erroneously started during the discharge of the capacitor 200 to be tested, but it is not closely related to the core content of this case and will not be described in detail here.

[0056] The time measurement module 2 includes an analog-to-digital converter 21, which is used to measure the voltage of the capacitor to be measured at a first trigger time point and a second trigger time point and convert it into a first sampling signal and a second sampling signal output, so as to calculate the capacitance value of the capacitor to be measured; the interval between the first trigger time point and the second trigger time point is the preset duration. The first trigger time point and the second trigger time point can be specifically set according to actual conditions, for example, the time when the voltage of the capacitor to be measured 200 just rises to the first preset voltage VL_th is set as the first trigger time point, and the second trigger time point can be reversely calculated from the preset duration.

[0057] One input terminal of the analog-to-digital converter (ADC) 21 is connected to the COM port, and the other input terminal is connected to the capacitor to be tested 200. The COM port is the common terminal of the multimeter chip and the capacitor to be tested, and the preset fixed level is Vcom. This configuration facilitates the measurement of the voltage of the capacitor to be tested 200.

[0058] The mode selection module 3 includes two switches K7 and K8. K7 corresponds to the constant voltage mode, and K8 corresponds to the constant time mode. When the corresponding switches are closed, the corresponding modules can work.

[0059] Based on the above circuit structure, this embodiment further provides a capacitance detection method, and the processor 5 is used to execute the capacitance detection method, or to execute a part of the capacitance detection method.

[0060] The capacitance detection method comprises:

[0061] Determine the capacitance gear, the capacitance gear includes a low capacitance gear and a high capacitance gear. For example, the capacitance gear is from the first capacitance gear to the ninth capacitance gear, and the range of each capacitance gear is different. The first capacitance gear to the seventh capacitance gear are low capacitance gears, and the eighth capacitance gear and the ninth capacitance gear are high capacitance gears. In other embodiments, the number of capacitance gears and the classification results may be different.

[0062] In one embodiment, the capacitor gear is determined according to the following logic: start from the lowest gear among the capacitor gears, and if the gears do not match, switch the gear upward once, wherein if the highest gear among the capacitor gears does not match, switch to the lowest gear among the capacitor gears.

[0063] The logic for determining whether the gears match includes:

[0064] When the capacitance gear is the low capacitance gear, if the voltage of the capacitor to be measured is not charged from the first preset voltage to the second preset voltage within the cut-off time, or the calculated final capacitance value exceeds the range of the current gear, it is judged that there is no match.

[0065] When the capacitance gear is the high capacitance gear and the calculated final capacitance value exceeds the range of the current gear, it is determined that they do not match.

[0066] The above logic can be referred to Figure 3 for understanding.

[0067] In this embodiment, the best measurement gear can be adaptively selected without manual intervention.

[0068] Please refer to Table 1. In one embodiment, the relevant parameter settings of each capacitance gear are as follows.

[0069] Table 1 Parameter Setting Table of Capacitance Gears

[0070]

[0071] Among them, VL1 and VL2 represent alternative values of VL_th, and VH1 and VH2 represent alternative values of VH_th. In this embodiment, VL2 < VL1 = VH2 < VH1. Tstop1 to 7 represent the cut-off time, that is, the parameter for judging whether the capacitance gear matches. In this embodiment, Tstop1 < Tstop2 < Tstop3 < Tstop4 < Tstop5 < Tstop6 < Tstop7. F1 to F6 represent the counting frequencies of the TDC. In this embodiment, F1 > F2 > F3 > F4 > F5 > F6, and F1 is the standard frequency, and F2, F3, F4, F5, F6 are obtained by dividing F1. T1 and T2 are the preset times. In this embodiment, T1 < T2.

[0072] The capacitance detection method further includes:

[0073] Based on the capacitance gear, output a control signal to switch the connection relationship between the constant current source and the capacitance to be measured, so that the charging current of the capacitance is different in at least two different capacitance gears. For example, the embodiment shown in Table 1.

[0074] If the capacitance gear is the low capacitance gear, output a control signal to drive the constant voltage measurement module to measure the charging time of the capacitance to be measured from the first preset voltage to the second preset voltage, and calculate the capacitance value of the capacitance to be measured based on the charging time.

[0075] Calculate the capacitance value of the capacitance to be measured based on the following formula:

[0076]

[0077] Wherein, C represents the capacitance value of the capacitor to be measured, I represents the charging current, counter represents the time counting signal, F represents the counting frequency of the time-to-digital converter, VH_th represents the second preset voltage, and VL_th represents the first preset voltage.

[0078] And, if the capacitance gear is the high capacitance gear, the output control signal drives the time measurement module to measure the voltage difference of the capacitor to be measured within a preset time period, and calculate the capacitance value of the capacitor to be measured based on the voltage difference.

[0079] Calculate the capacitance value of the capacitor to be measured based on the following formula:

[0080]

[0081] Wherein, C represents the capacitance value of the capacitor to be measured, I represents the charging current, T represents the preset time, adc2 represents the second sampling signal, adc1 represents the first sampling signal, N represents the number of bits of the analog-to-digital converter, V REF Represents the reference voltage of the analog-to-digital converter.

[0082] In addition, the embodiment shown in Table 1 can be summarized as follows: the preset parameters of the capacitor gear include: charging current, the first preset voltage, the second preset voltage, the preset duration, the cut-off duration, and the counting frequency of the time-to-digital converter; in different capacitor gears, at least one of the preset parameters is different. By reasonably configuring the parameters of each gear, each gear has a reasonable range and a wide coverage range, and can handle capacitors of different capacitance values.

[0083] The fast, wide-range, adaptive multimeter capacitance detection circuit and method proposed in this embodiment can realize fast and accurate measurement of capacitors of different capacities, simplify the operation process, reduce production costs, and provide strong technical support for the development of the electronics manufacturing industry. Through this embodiment, the capacitance value can be measured with high accuracy, without the need to use the dial to switch gears, and the internal automatic range is determined for measurement. The circuit has high integration, is stable and reliable, and has a fast measurement time. It can be widely used in the test equipment industry for consumer electronic products.

[0084] In summary, this embodiment provides a capacitance detection circuit and a capacitance detection method. The capacitance detection circuit includes a constant voltage measurement module, a constant time measurement module and a mode selection module; the constant voltage measurement module is used to measure the charging time of the capacitor to be measured from a first preset voltage to a second preset voltage, and the charging time is used to calculate the capacitance value of the capacitor to be measured; the constant time measurement module is used to measure the voltage difference of the capacitor to be measured within a preset time length, and the voltage difference is used to calculate the capacitance value of the capacitor to be measured. The mode selection module is used to switch one of the constant voltage measurement module and the constant time measurement module to work. The capacitance detection method works based on the above-mentioned capacitance detection circuit. With such a configuration, by setting different range gears and setting different measurement methods at different gears, it can cope with capacitors with different capacitance values, and has high accuracy and response speed, and strong adaptability; thereby solving the problems existing in the prior art.

[0085] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A capacitance detection circuit, characterized in that: The capacitance detection circuit includes a constant voltage measurement module, a constant time measurement module and a mode selection module; the constant voltage measurement module is used to measure the charging time of the capacitor to be tested from a first preset voltage to a second preset voltage, and the charging time is used to calculate the capacitance value of the capacitor to be tested; The time measurement module is used to measure the voltage difference of the capacitor to be measured within a preset time period, and the voltage difference is used to calculate the capacitance value of the capacitor to be measured; The mode selection module is used to switch one of the constant voltage measurement module and the constant time measurement module to operate.

2. The capacitance detection circuit according to claim 1, characterized in that: The capacitance detection circuit also includes a charging and discharging module, which includes at least two constant current sources. The charging and discharging module provides at least two different constant charging currents based on switching the connection relationship between the constant current source and the capacitor to be measured.

3. The capacitance detection circuit according to claim 1, characterized in that: The constant voltage measurement module includes a window comparison unit and a time digital converter. The window comparison unit is used to drive the time digital converter to count when the voltage of the capacitor to be measured rises from the first preset voltage to the second preset voltage time period, and does not drive the time digital converter to count in other cases; the time digital converter is used to convert the total duration of its own counting into a time counting signal output, so as to calculate the capacitance value of the capacitor to be measured.

4. The capacitance detection circuit according to claim 1, characterized in that: The timing measurement module includes an analog-to-digital converter, which is used to measure the voltage of the capacitor to be measured at a first trigger time point and a second trigger time point and convert it into a first sampling signal and a second sampling signal output, so as to calculate the capacitance value of the capacitor to be measured; The interval between the first trigger time point and the second trigger time point is the preset duration.

5. A capacitance detection method, characterized in that: The capacitance detection method is applied to a capacitance detection circuit, the capacitance detection circuit includes a constant voltage measurement module and a constant time measurement module; the capacitance detection method includes: Determining a capacitance gear, wherein the capacitance gear includes a low capacitance gear and a high capacitance gear; If the capacitance gear is the low capacitance gear, outputting a control signal to drive the constant voltage measurement module to measure the charging time of the capacitor to be measured from the first preset voltage to the second preset voltage, and calculating the capacitance value of the capacitor to be measured based on the charging time; and If the capacitance position is the high capacitance position, the output control signal drives the time measurement module to measure the voltage difference of the capacitor to be measured within a preset time period, and calculate the capacitance value of the capacitor to be measured based on the voltage difference.

6. The capacitance detection method according to claim 5, characterized in that: The capacitance detection circuit further includes a charge and discharge module, and the charge and discharge module includes at least two constant current sources; the capacitance detection method includes: The connection relationship between the constant current source and the capacitor to be measured is switched based on the capacitor gear output control signal, so that the charging current of the capacitor is different in at least two different capacitor gears.

7. The capacitance detection method according to claim 5, characterized in that: The constant voltage measurement module includes a window comparison unit and a time-to-digital converter; The capacitance detection method comprises: When the capacitance gear is the low capacitance gear, when the voltage of the capacitor to be measured rises from the first preset voltage to the second preset voltage within a time period, the window comparison unit drives the time-to-digital converter to count, and does not drive the time-to-digital converter to count in other cases; The time-to-digital converter converts the total duration of its own counting into a time counting signal; Calculate the capacitance value of the capacitor to be measured based on the following formula: Wherein, C represents the capacitance value of the capacitor to be measured, I represents the charging current, counter represents the time counting signal, F represents the counting frequency of the time-to-digital converter, VH_th represents the second preset voltage, and VL_th represents the first preset voltage.

8. The capacitance detection method according to claim 5, characterized in that: The timing measurement module includes an analog-to-digital converter; The capacitance detection method comprises: When the capacitance gear is the high capacitance gear, the analog-to-digital converter is used to measure the voltage of the capacitor to be measured at a first trigger time point and a second trigger time point and convert it into a first sampling signal and a second sampling signal; the interval between the first trigger time point and the second trigger time point is the preset time length; Calculate the capacitance value of the capacitor to be measured based on the following formula: Wherein, C represents the capacitance value of the capacitor to be measured, I represents the charging current, T represents the preset time, adc2 represents the second sampling signal, adc1 represents the first sampling signal, N represents the number of bits of the analog-to-digital converter, V REF Represents the reference voltage of the analog-to-digital converter.

9. The capacitance detection method according to claim 5, characterized in that: The step of determining the capacitance gear comprises: starting from the lowest gear of the capacitance gear, if the gear does not match, switching the gear upward once, wherein if the highest gear of the capacitance gear does not match, switching to the lowest gear of the capacitance gear; The logic for determining whether the gears match includes: When the capacitance gear is the low capacitance gear, if the voltage of the capacitor to be measured is not charged from the first preset voltage to the second preset voltage within the cut-off time, or the calculated final capacitance value exceeds the range of the current gear, it is judged that there is no match; When the capacitance gear is the high capacitance gear, the calculated final capacitance value exceeds the range of the current gear, and it is determined that there is no match.

10. The capacitance detection method according to claim 5, characterized in that: The constant voltage measurement module includes a window comparison unit and a time digital converter, wherein the window comparison unit is used to drive the time digital converter to count when the voltage of the capacitor to be measured rises from the first preset voltage to the second preset voltage, and does not drive the time digital converter to count in other cases; the time digital converter is used to convert the total duration of its own counting into a time counting signal output, so as to calculate the capacitance value of the capacitor to be measured; When the capacitance gear is the low capacitance gear, if the voltage of the capacitor to be tested is not charged from the first preset voltage to the second preset voltage within the cut-off time, it is determined that the gear does not match; The preset parameters of the capacitor gear include: charging current, the first preset voltage, the second preset voltage, the preset duration, the cut-off duration, and the counting frequency of the time-to-digital converter; In different capacitance gears, at least one of the preset parameters is different.

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