A microcapacitance detection method and device

Abstract

The present invention provides a micro-capacitor detection method and device. The micro-capacitor detection method comprises: generating a pulse signal; using a detection circuit to convert the pulse signal into a detection reference signal; using the detection circuit connected to the micro-capacitor to be measured to convert the pulse signal into a detection signal; obtaining the phase difference between the detection signal and the detection reference signal; and calculating the capacitance value of the micro-capacitor to be measured according to the phase difference. The micro-capacitor detection method is completely implemented by a digital circuit, and has the advantages of fast detection speed, wide detection range, etc.

Description

Technical Field

[0001] The invention belongs to the field of capacitance measurement and relates to a capacitance detection method, in particular to a micro-capacitance detection method and device. Background Art

[0002] In recent years, with the continuous development of semiconductor technology and the continuous advancement of technology, the application of microcapacitors has become more and more extensive. Microcapacitors in a general sense refer to microfarad or picofarad capacitance. Microcapacitor detection is widely used in capacitive biosensors, capacitive sound (vibration) sensors, capacitive light sensors, capacitive proximity sensors, capacitive gravity sensors, capacitive touch buttons, capacitive touch screens, and medium uniformity detection. However, most of the existing microcapacitor detection methods rely on analog circuits to convert capacitance into parameters such as voltage, current, and frequency, and then analyze and process these parameters to obtain the corresponding capacitance value. This method has a low conversion rate. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a micro-capacitance detection method and device to solve the problem of low conversion rate in the prior art.

[0004] To achieve the above-mentioned purpose and other related purposes, the present invention provides a micro-capacitor detection method, which includes: generating a pulse signal; using a detection circuit to convert the pulse signal into a detection reference signal; connecting the micro-capacitor to be measured to the detection circuit; using the detection circuit to convert the pulse signal into a detection signal; obtaining the phase difference between the detection signal and the detection reference signal; and calculating the capacitance value of the micro-capacitor to be measured based on the phase difference.

[0005] In one embodiment of the present invention, the process of generating a pulse signal includes: using a frequency divider to divide a reference clock signal to generate a first square wave signal; the first square wave signal is the pulse signal.

[0006] In one embodiment of the present invention, the implementation process of obtaining the phase difference between the detection signal and the detection reference signal includes: shaping the detection reference signal to obtain a second square wave signal; performing logical exclusive OR processing on the first square wave signal and the second square wave signal to obtain a first phase difference pulse; shaping the detection signal to obtain a third square wave signal; performing logical exclusive OR processing on the first square wave signal and the third square wave signal to obtain a second phase difference pulse; calculating the phase difference between the detection signal and the detection reference signal according to the pulse width of the first phase difference pulse and the pulse width of the second phase difference pulse, and the calculation formula is: Where ΔP 1is the phase difference between the detection signal and the detection reference signal; T represents the time length of one sampling cycle of the first square wave signal; t 1 represents the pulse width of the first phase difference pulse, t 2 represents the pulse width of the second phase difference pulse, t 1 <t 2 <T.

[0007] In an embodiment of the present invention, a method for measuring the pulse width of the phase difference pulse includes: measuring the pulse width of the phase difference pulse using the reference clock signal.

[0008] In one embodiment of the present invention, the detection circuit includes a buffer and a resistor; the pulse signal is converted into the detection reference signal after passing through the buffer and the resistor; after the detection circuit is connected to the microcapacitor to be measured, the pulse signal is converted into the detection signal after passing through the first buffer and the resistor.

[0009] In one embodiment of the present invention, the method for calculating the capacitance value of the micro-capacitor to be measured according to the phase difference includes: shaping the detection reference signal and the detection signal through an input buffer; calculating the conversion coefficient between the phase difference and the capacitance value, and the calculation formula of the conversion coefficient is Where K represents the conversion coefficient between the phase difference and the capacitance value; f is the frequency of the pulse signal; R is the resistance value of the resistor; D is the voltage ratio of the threshold of the input buffer to the first square wave signal, and its value range is 0<D<1; the capacitance value of the microcapacitor to be measured is calculated as C x =K×ΔP; where C x is the capacitance value of the micro-capacitor to be measured; ΔP is the phase difference between the detection signal and the detection reference signal.

[0010] In one embodiment of the present invention, the micro-capacitance detection method further includes: changing the resistance value of the resistor to change the phase resolution of the micro-capacitance detection method; the phase resolution represents the minimum capacitance value that can be detected by the micro-capacitance detection method.

[0011] In one embodiment of the present invention, the micro-capacitance detection method further includes: adjusting the frequency of the reference clock signal to adjust the phase resolution of the micro-capacitance detection method; the relationship between the phase resolution and the frequency of the reference clock signal is: Among them, P LSB is the phase resolution, indicating the minimum capacitance value that can be detected by the micro-capacitance detection method; f is the frequency of the first square wave signal; f CLK is the frequency of the reference clock signal.

[0012] In an embodiment of the present invention, the detection circuit has a parasitic capacitor.

[0013] The present invention also provides a micro-capacitor detection device, which includes: a signal generating module, which is used to generate a pulse signal; a detection circuit, which is connected to the signal generating module and is used to convert the pulse signal into a detection reference signal; after the detection circuit is connected to the micro-capacitor to be measured, it is used to convert the pulse signal into a detection signal; a phase difference acquisition module, which is respectively connected to the output end of the detection circuit and the signal generating module, and is used to obtain the phase difference between the detection signal and the detection reference signal; a calculation module, which is connected to the phase difference acquisition module and is used to calculate the capacitance value of the micro-capacitor to be measured based on the phase difference.

[0014] In one embodiment of the present invention, the signal generating module includes: a clock unit, used to generate a reference clock signal; a divider unit, connected to the clock unit and the detection circuit, used to divide the reference clock signal to generate a first square wave signal; the first square wave signal is the pulse signal.

[0015] In one embodiment of the present invention, the phase difference acquisition module includes: a shaping unit, connected to the output end of the detection circuit, used to shape the detection reference signal to obtain a second square wave signal; after the detection circuit is connected to the micro-capacitor to be measured, the shaping unit is used to shape the detection signal to obtain a third wave signal; an XOR unit, connected to the shaping unit and the signal generating module respectively, used to perform logical XOR processing on the first square wave signal and the second square wave signal to obtain a first phase difference pulse; after the detection circuit is connected to the micro-capacitor to be measured, the XOR unit is used to perform logical XOR processing on the first square wave signal and the third wave signal to obtain a second phase difference pulse; a phase difference calculation unit, connected to the XOR unit, used to calculate the phase difference between the detection signal and the detection reference signal according to the pulse width of the first phase difference pulse and the pulse width of the second phase difference pulse, and the calculation formula is: Where ΔP 1 is the phase difference between the detection signal and the detection reference signal; T represents the time length of one sampling cycle of the first square wave signal; t 1 represents the pulse width of the first phase difference pulse, t 2 represents the pulse width of the second phase difference pulse, t 1 <t 2 <T.

[0016] In one embodiment of the present invention, the phase difference calculation unit includes: a pulse width measurement subunit, connected to the XOR unit, and configured to measure the pulse width of the phase difference pulse using the reference clock signal.

[0017] In one embodiment of the present invention, the detection circuit includes: a first buffer, connected to the signal generating module, for buffering the pulse signal; a resistor; the first end of the resistor is connected to the first buffer, and the second end is connected to the phase difference acquisition module; the pulse signal is converted into the detection reference signal after passing through the first buffer and the resistor; after the detection circuit is connected to the microcapacitor to be measured, the pulse signal is converted into the detection signal after passing through the first buffer and the resistor.

[0018] In one embodiment of the present invention, the shaping unit includes an input buffer; the input buffer is connected to the output end of the detection circuit and is used to shape the detection reference signal and the detection signal; the calculation module includes: a conversion coefficient calculation unit, connected to the phase difference acquisition module, and used to calculate the conversion coefficient between the phase difference and the capacitance value, and the calculation formula of the conversion coefficient is: Wherein K represents the conversion coefficient between the phase difference and the capacitance value; f is the frequency of the pulse signal; R is the resistance value of the resistor; D is the voltage ratio of the threshold of the input buffer to the first square wave signal, and its value range is 0<D<1; the capacitance value calculation unit is connected to the conversion coefficient calculation unit and is used to calculate the capacitance value of the microcapacitor to be measured, and the calculation formula is C x =K×ΔP; where C x is the capacitance value of the micro-capacitor to be measured; ΔP is the phase difference between the detection signal and the detection reference signal.

[0019] In one embodiment of the present invention, the resistance value of the resistor can be changed; by changing the resistance value of the resistor, the phase resolution of the micro-capacitance detection method can be changed; the phase resolution represents the minimum capacitance value that can be detected by the micro-capacitance detection method.

[0020] In one embodiment of the present invention, the frequency of the reference clock signal generated by the clock unit can be adjusted; the phase resolution of the micro-capacitance detection method can be adjusted by adjusting the frequency of the reference clock signal; the relationship between the phase resolution and the frequency of the reference clock signal is: Among them, P LSB is the phase resolution, indicating the minimum capacitance value that can be detected by the micro-capacitance detection method; f is the frequency of the first square wave signal; f CLK is the frequency of the reference clock signal.

[0021] In an embodiment of the present invention, the detection circuit has a parasitic capacitor.

[0022] As described above, the micro-capacitor detection method and device of the present invention have the following beneficial effects: the micro-capacitor detection method is completely implemented by a digital circuit, and the external interface also uses a common IO port. The capacitance value of the micro-capacitor is converted into the phase difference of the detection signal, and the capacitance is detected by detecting the phase difference. Traditional solutions generally realize the detection of tiny capacitance with the participation of analog circuit devices such as high-precision operational amplifiers, analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). Compared with the two, the micro-capacitor detection method of the present invention has the advantages of fast detection speed and wide detection range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a flow chart of the micro-capacitance detection method of the present invention in a specific embodiment.

[0024] Figure 2A Shown is a waveform example diagram of the micro-capacitance detection method / device described in the present invention in a specific embodiment.

[0025] Figure 2B Shown is a waveform example diagram of the micro-capacitance detection method / device described in the present invention in a specific embodiment.

[0026] Figure 3 The flowchart of step S4 of the micro-capacitance detection method of the present invention in a specific embodiment is shown.

[0027] Figure 4 Shown is a flow chart of measuring the pulse width of a phase difference pulse signal in a specific embodiment of the micro-capacitance detection method of the present invention.

[0028] Figure 5A Shown is an example diagram of a detection reference signal in a specific embodiment of the micro-capacitance detection method / device of the present invention.

[0029] Figure 5B Shown is an example diagram of a second square wave signal in a specific embodiment of the micro-capacitance detection method / device of the present invention.

[0030] Figure 6 Shown is a schematic structural diagram of the micro-capacitance detection device of the present invention in a specific embodiment.

[0031] Fig. 7A Shown is a circuit diagram of the micro-capacitance detection device of the present invention in a specific embodiment.

[0032] Figure 7B Shown is a circuit diagram of the micro-capacitance detection device of the present invention in a specific embodiment.

[0033] Fig. 8A Shown is a circuit diagram of the micro-capacitance detection device of the present invention in a specific embodiment.

[0034] Figure 8B Shown is a circuit diagram of the micro-capacitance detection device of the present invention in a specific embodiment.

[0035] Component number description

[0036] 600 Microcapacitance Detection Device

[0037] 610 Signal Generation Module

[0038] 611 Clock Unit

[0039] 612 Crossover Unit

[0040] 620 Detection Circuit

[0041] 621 First Buffer

[0042] 622 Resistors

[0043] 630 Phase difference acquisition module

[0044] 631 Shaping Unit

[0045] 632 XOR unit

[0046] 633 Phase difference calculation unit

[0047] 640 Computing Module

[0048] 641 Conversion coefficient calculation unit

[0049] 642 Capacitance calculation unit

[0050] 710 Crossover

[0051] 720 Buffer

[0052] 730 Resistor

[0053] 740 Microcapacitor to be measured

[0054] 750 Capacitor

[0055] 760 Schmitt trigger

[0056] 770 XOR Gate

[0057] 780 AND Gate

[0058] 810 Crossover

[0059] 820 Buffer

[0060] 830 Resistor

[0061] 840 Microcapacitor to be measured

[0062] 860 Schmitt Trigger

[0063] 870 XOR Gate

[0064] 880 AND Gate

[0065] Steps S1 to S5

[0066] Steps S41 to S45

[0067] Steps S451 to S453 DETAILED DESCRIPTION

[0068] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0069] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0070] Microcapacitance detection is widely used in capacitive biosensors, capacitive sound (vibration) sensors, capacitive light sensors, capacitive proximity sensors, capacitive gravity sensors, capacitive touch buttons, capacitive touch screens, and medium uniformity detection. However, the existing microcapacitance detection method relies on analog circuits to convert capacitance into parameters such as voltage, current, and frequency, and then analyzes and processes these parameters to obtain corresponding capacitance values. This method has a low conversion rate. In response to this problem, the present invention provides a microcapacitance detection method, which includes: generating a pulse signal; using a detection circuit to convert the pulse signal into a detection reference signal; connecting the microcapacitor to be measured with the detection circuit; using the detection circuit to convert the pulse signal into a detection signal; obtaining the phase difference between the detection signal and the detection reference signal; and calculating the capacitance value of the microcapacitor to be measured based on the phase difference. The microcapacitance detection method is completely implemented by a digital circuit, which converts the capacitance value of the microcapacitor into the phase difference of the detection signal, and realizes the detection of the capacitance by detecting the phase difference. Compared with the traditional detection scheme, the detection speed is faster and the detection range is wider.

[0071] See also Figure 1 , which is a schematic diagram of a flow chart of a micro-capacitance detection method according to the present invention in a specific embodiment. In this embodiment, the micro-capacitance detection method includes:

[0072] S1, generates a pulse signal. Pulse signal is a discrete signal with various shapes. Compared with ordinary analog signals (such as sine waves), the waveforms are discontinuous on the vertical axis (there is a clear interval between waveforms), but have a certain periodicity. Common pulse signals include rectangular pulses, sawtooth pulses, triangular pulses, spike pulses, step pulses, etc.

[0073] S2, using a detection circuit to convert the pulse signal into a detection reference signal. When the detection circuit includes a capacitor or is connected to a capacitor, the pulse signal will produce a phase change after flowing through the detection circuit, that is, the pulse signal will produce a phase shift. The magnitude of the phase change depends on the capacitance value of the capacitor inside the detection circuit and the capacitance value of the capacitor connected to the detection circuit. In step S2, the pulse signal forms the detection reference signal after flowing through the detection circuit. In particular, when the detection circuit does not include a capacitor and is not connected to a capacitor, the detection reference signal has the same phase as the pulse signal, that is, the phase difference is 0.

[0074] S3, converting the pulse signal into a detection signal using the detection circuit connected to the micro-capacitor to be measured. The detection signal is a signal at the connection between the detection circuit and the micro-capacitor to be measured. Due to the access of the micro-capacitor to be measured, the phase shift generated when the pulse signal flows through the detection circuit will change, so there is a phase difference between the detection signal and the detection reference signal, and the size of the phase difference is related to the capacitance value of the micro-capacitor to be measured.

[0075] S4, obtaining a phase difference between the detection signal and the detection reference signal. The phase difference can be obtained by using a specific digital circuit or instrument.

[0076] S5, calculating the capacitance value of the micro capacitor to be measured according to the phase difference. The magnitude of the phase difference is related to the capacitance value of the micro capacitor to be measured, so the capacitance value of the micro capacitor to be measured can be calculated according to the phase difference.

[0077] In one embodiment of the present invention, the process of generating a pulse signal includes: using a frequency divider to divide a reference clock signal to generate a first square wave signal; the first square wave signal is the pulse signal.

[0078] The reference clock signal is the basis of sequential logic. It is used to determine when the state in the logic unit is updated. It is a signal with a fixed period and is independent of the circuit operation status. The reference clock is usually used in synchronous circuits, plays the role of a timer, and constitutes the electronic components of the circuit. A common reference clock signal is a square wave signal with a 50% duty cycle.

[0079] A frequency divider is a device that divides the input signal and outputs a specific frequency component in the input signal. The frequency of the signal output by the frequency divider can be changed by setting the frequency division coefficient.

[0080] In this embodiment, the reference clock signal is input into the frequency divider, and the frequency divider extracts the specific frequency component in the reference clock signal and outputs a square wave signal of a specific frequency, which is recorded as the first square wave signal. The square wave signal can be used as the pulse signal in step S1.

[0081] See also Figure 2A and Figure 2B , the clk signal is a reference clock signal, and the reference clock signal can obtain the corresponding first square wave signal drv after being divided by a frequency divider. Figure 2A and Figure 2B This is an example diagram. In actual applications, the frequency of the reference clock signal is higher, and the number of pulses of the reference clock signal included in one cycle of the first square wave signal is greater.

[0082] See also Figure 3 In one embodiment of the present invention, the process of obtaining the phase difference between the detection signal and the detection reference signal includes:

[0083] S41, shaping the detection reference signal to obtain a second square wave signal. The shaping can be achieved by using a shaping circuit. The shaping circuit is mainly used to shape slowly changing or irregular signals into signals with steep edges. It can also be used to remove interference signals in input signals and to transform one waveform into another. The Schmitt trigger is a common shaping circuit in practical applications. In addition, the shaping can also be achieved by using a comparator. After shaping, the detection reference signal is shaped into a square wave signal, which is the second square wave signal. Please refer to Figure 2A , the first square wave signal becomes a detection reference signal in1 after passing through the detection circuit, and the detection reference signal in1 becomes the second square wave signal fb1 after being shaped.

[0084] S42, performing a logical exclusive OR process on the first square wave signal and the second square wave signal to obtain a first phase difference pulse. Figure 2A , the first square wave signal drv and the second square wave signal fb1 are subjected to XOR processing, and the parts that are both high level or both low level are subjected to XOR and output low level; the parts that are one high level and the other low level are subjected to XOR and output high level, so the first square wave signal drv and the second square wave signal fb1 are subjected to XOR processing to obtain the first phase difference pulse gat1. There is a time difference between the rising edge of the second square wave signal fb1 and the rising edge of the first square wave signal drv, and the time difference is the width of the first phase difference pulse gat1. Therefore, the phase difference between the second square wave signal and the first square wave signal can be calculated based on the width of the first phase difference pulse gat1. The corresponding phase change of the first square wave signal within one sampling period is 2π, so the phase difference calculation formula between the second square wave signal and the first square wave signal is: Wherein T represents the time length of one sampling period of the first square wave signal; t 1 represents the pulse width of the first phase difference pulse, t 1 <T.

[0085] S43, shaping the detection signal to obtain a third wave signal. The shaping can be implemented by a shaping circuit or a comparison circuit. After shaping, the detection signal is shaped into a square wave signal, which is the third wave signal. Figure 2BAfter the detection circuit is connected to the micro-capacitor to be measured, the first square wave signal drv flows through the detection circuit to form a detection signal in2, and the detection signal in2 is transformed into the third square wave signal fb2 after shaping.

[0086] S44, performing a logical exclusive OR process on the first square wave signal and the third square wave signal to obtain a second phase difference pulse. Figure 2B , the first square wave signal drv and the third square wave signal fb2 are XORed, and the parts that are both high level or both low level are XORed to output low level; the parts that are one high level and the other low level are XORed to output high level, so the gat2 signal is the second phase difference pulse obtained after the first square wave signal drv and the third square wave signal fb2 are XORed. In addition, there is a time difference between the rising edge of the third square wave signal fb2 and the rising edge of the first square wave signal drv, and the time difference is the width of the second phase pulse gat2. Therefore, the phase difference between the third square wave signal and the first square wave signal can be calculated based on the width of the second phase difference pulse gat2. The corresponding phase change of the first square wave signal within one sampling period is 2π, so the calculation formula of the phase difference between the third square wave signal and the first square wave signal is Wherein T represents the time length of one sampling period of the first square wave signal; t 2 represents the pulse width of the second phase difference pulse, t 2 <T.

[0087] S45, calculating the phase difference between the detection signal and the detection reference signal according to the pulse width of the first phase difference pulse and the pulse width of the second phase difference pulse, and the calculation formula is: Where ΔP 1 is the phase difference between the detection signal and the detection reference signal; T represents the time length of one sampling cycle of the first square wave signal; t 1 represents the pulse width of the first phase difference pulse, t 2 represents the pulse width of the second phase difference pulse, t 1 <t 2 <T.

[0088] In one embodiment of the present invention, a method for measuring the pulse width of the phase difference pulse includes: measuring the pulse width of the phase difference pulse using the reference clock signal. Figure 4 , the method for measuring the pulse width of the phase difference pulse includes:

[0089] S451, performing a logical AND operation on the reference clock signal and the phase difference pulse signal to obtain a corresponding phase signal; see Figure 2A , the reference clock signal clk and the first phase difference pulse signal gat1 are logically ANDed to obtain a first phase signal phase1; see Figure 2B The reference clock signal clk and the second phase difference pulse signal gat2 are logically ANDed to obtain the second phase signal phase2. In one sampling period of the first square wave signal, the number of pulses of the first phase signal phase1 is proportional to the pulse width of the first phase difference pulse gat1, and the number of pulses of the second phase signal phase2 is proportional to the pulse width of the second phase difference pulse gat2.

[0090] S452, obtaining the number of pulses contained in one cycle of the phase signal. The number of pulses can be obtained using a frequency meter. Specifically, the number of pulses contained in one cycle of the first phase signal phase1 and the number of pulses contained in one cycle of the second phase signal phase2 are measured using a frequency meter.

[0091] S453, calculating the pulse width of the phase difference pulse according to the number of pulses. The duration of each pulse in the phase signal is the same as the duration of each pulse in the reference clock signal, and the pulse width of the phase difference pulse can be obtained by multiplying the number of pulses by the duration of each pulse in the reference clock signal. Specifically, the pulse width of the first phase difference pulse gat1 is calculated according to the number of pulses contained in one cycle of the first phase signal phase1, and the pulse width of the second phase difference pulse gat2 is calculated according to the number of pulses contained in one cycle of the second phase signal phase2.

[0092] In one embodiment of the present invention, the detection circuit includes a buffer and a resistor; the pulse signal is converted into the detection reference signal after passing through the buffer and the resistor; after the detection circuit is connected to the microcapacitor to be measured, the pulse signal is converted into the detection signal after passing through the first buffer and the resistor. In an actual circuit, the pulse signal first flows through the buffer and then flows through the resistor.

[0093] When the detection circuit is not connected to the microcapacitor to be measured, the resistor is connected in series with the capacitor in the detection circuit to form an RC circuit. In particular, if the pulse signal is a square wave, then within one cycle of the pulse signal:

[0094] When the pulse signal is converted from a low level to a high level, the capacitor in the detection circuit starts to charge. At this time, the voltage value at the connection point between the capacitor and the resistor in the RC circuit is the detection reference signal, and its change relationship with time is: Where t represents time; U s represents the voltage value corresponding to the high level of the pulse signal; R is the resistance value of the resistor, and C is the capacitance value of the capacitor in the detection circuit. c (t) is the voltage of the detection reference signal, and its image changing with time is as follows: Figure 5A As shown in paragraph ①. When the time is long enough, the voltage of the detection reference signal is U s .

[0095] When the pulse signal is converted from high level to low level, the capacitor in the detection circuit begins to discharge. At this time, the relationship between the voltage of the detection reference signal and time is: u c (t) is the voltage of the detection reference signal, and its image changing with time is as follows: Figure 5A As shown in paragraph ②, when the time is long enough, the voltage of the detection reference signal is 0.

[0096] In summary, Figure 5A It is shown as the voltage of the detection reference signal within one cycle of the pulse signal.

[0097] When the detection circuit is connected to the micro-capacitor to be measured, the micro-capacitor to be measured is connected in parallel with the capacitor in the detection circuit and then forms an RC circuit with the resistor. In particular, if the pulse signal is a square wave, then within one cycle of the pulse signal:

[0098] When the pulse signal is converted from a low level to a high level, the capacitor in the detection circuit starts to charge. At this time, the voltage value at the connection point between the capacitor and the resistor in the RC circuit is the detection signal, and its change relationship with time is: Among them C x is the capacitance value of the microcapacitor to be measured; u' c (t) represents the voltage of the detection signal. When the time is long enough, the voltage of the detection signal is U s Compared with the detection reference signal, the detection signal increases more slowly.

[0099] When the pulse signal is converted from high level to low level, the capacitor in the detection circuit begins to discharge. At this time, the relationship between the voltage of the detection reference signal and time is: When the time is long enough, the voltage of the detection signal is 0. Compared with the detection reference signal, the detection signal decreases more slowly.

[0100] In one embodiment of the present invention, the shaping unit includes an input buffer; the input buffer is connected to the output end of the detection circuit and is used to shape the detection reference signal and the detection signal; in particular, the input buffer is a Schmitt trigger. The Schmitt trigger has two stable states, but unlike a general trigger, the Schmitt trigger adopts a potential triggering mode, and its state is maintained by the input signal potential; for input signals with two different change directions of negative decreasing and positive increasing, the Schmitt trigger has different threshold voltages.

[0101] See also Figure 5A ,Will Figure 5A The detection reference signal shown is used as the input signal of the input buffer: c (t) is greater than the threshold of the input buffer, the input buffer outputs a high level; when u c When (t) is less than or equal to the threshold of the input buffer, the input buffer outputs a low level. Figure 5B Displayed as Figure 5A The second square wave signal corresponding to the detection reference signal.

[0102] Similarly, when the detection circuit is connected to the micro-capacitor to be measured, the detection signal is used as the input signal of the input buffer: when the detection signal is greater than the threshold of the input buffer, the input buffer outputs a high level; when the detection signal is less than or equal to the threshold of the input buffer, the input buffer outputs a low level. Therefore, the detection signal can obtain a corresponding third wave signal after being shaped by the input buffer.

[0103] The calculation module includes: a conversion coefficient calculation subunit, connected to the phase difference acquisition module, for calculating the conversion coefficient between the phase difference and the capacitance value, and the calculation formula of the conversion coefficient is: Wherein K represents the conversion coefficient between the phase difference and the capacitance value; f is the frequency of the pulse signal; R is the resistance value of the resistor; D is the voltage ratio of the threshold of the input buffer to the first square wave signal, and its value range is 0<D<1; preferably, The capacitance value calculation subunit is connected to the conversion coefficient calculation subunit and is used to calculate the capacitance value of the microcapacitor to be measured. The calculation formula is C x =K×ΔP 1 ; where C x is the capacitance value of the microcapacitor to be measured; ΔP 1 is the phase difference between the detection signal and the detection reference signal.

[0104] In this embodiment, when the detection circuit is not connected to the micro-capacitor to be measured, within one cycle of the pulse signal, when the voltage of the detection reference signal changes from low to high, the ratio of the voltage of the detection reference signal to the voltage of the first square wave signal is equal to D at time tt1, where tt1 = -RC ln(1-D); therefore, when the detection circuit is not connected to the micro-capacitor to be measured, the phase shift of the detection signal relative to the pulse signal is P 3 =-2πRCf ln(1-D).

[0105] When the detection circuit is connected to the microcapacitor to be measured, within one cycle of the pulse signal, when the voltage of the detection signal changes from low to high, the ratio of the voltage of the detection signal to the voltage of the first square wave signal is equal to D at time tt2, where tt2 = -R(C+C x )ln(1-D); Therefore, when the detection circuit is connected to the microcapacitor to be measured, the phase shift of the detection signal relative to the pulse signal is P 4 =-2πR(C+C x )f ln(1-D).

[0106] In summary, the phase difference between the detection signal and the detection reference signal ΔP=P 4 -P 3 =-2πRC x f ln(1-D). Where ΔP is the theoretical value of the phase difference. Therefore, if the phase difference ΔP is known, it can be calculated according to The capacitance value of the microcapacitor to be measured is obtained, therefore, That is, it is the conversion coefficient between the phase difference and the capacitance value.

[0107] In this embodiment, the measured phase difference ΔP 1 According to the formula C x =K×ΔP 1 The capacitance value of the microcapacitor to be measured is obtained by calculation.

[0108] In one embodiment of the present invention, the resistance value R=500Kohm, the frequency of the pulse signal f=1kHZ, the voltage ratio of the threshold of the input buffer to the first square wave signal Then the conversion coefficient K≈3.183×10 -10 At this time, the phase difference caused by introducing 1pF of the micro-capacitor to be measured is 0.124°.

[0109] In one embodiment of the present invention, the resistor is an internal resistance of a related element in the detection circuit, such as an internal resistance of a buffer.

[0110] In one embodiment of the present invention, the micro-capacitance detection method further comprises: changing the resistance value of the resistor to change the phase resolution of the micro-capacitance detection method; the phase resolution represents the minimum capacitance value that can be detected by the micro-capacitance detection method. The magnitude of the phase difference depends on the frequency f of the pulse signal, the resistance value R, the threshold of the input buffer and the capacitance value C of the microcapacitor to be measured. x The phase difference is an angle, and the measurement of the phase difference depends on the accuracy of the angle measurement method; when the phase difference is too small, the measurement error of the angle is large. Therefore, in order to ensure the accuracy of the measurement, the phase difference introduced by the micro-capacitor to be measured should be within an appropriate value range.

[0111] In this embodiment, the phase resolution of the micro-capacitance detection method is changed by changing the resistance value of the resistor. Assuming that the minimum phase difference that can be accurately detected by the phase difference measurement method is 0.124°: when the resistance value R = 500Kohm, the frequency of the pulse signal f = 1kHZ, the voltage ratio of the threshold of the input buffer to the first square wave signal At this time, the minimum capacitance that can be accurately detected by the micro-capacitance detection method is 1pF; when the resistance value R=5000Kohm, the frequency of the pulse signal f=1kHZ, the voltage ratio of the threshold of the input buffer to the first square wave signal At this time, the minimum capacitance value that can be accurately detected by the micro-capacitance detection method is 0.1pF, and the corresponding phase resolution capability is improved by 10 times. The resistance value of the resistor can be changed by using an adjustable resistor in the circuit, or by adding a new resistor in series or in parallel with the original resistor, or by replacing the original resistor with a resistor of a suitable resistance value.

[0112] In one embodiment of the present invention, the micro-capacitance detection method further includes: adjusting the frequency of the reference clock signal to adjust the phase resolution of the micro-capacitance detection method; the relationship between the phase resolution and the frequency of the reference clock signal is: Among them, P LSB is the phase resolution, indicating the minimum capacitance value that can be detected by the micro-capacitance detection method; f is the frequency of the first square wave signal; f CLK is the frequency of the reference clock signal. In this embodiment, the phase difference is measured by the reference clock signal, so the minimum phase difference that can be accurately measured is related to the frequency of the reference clock signal. For example, when the frequency of the reference clock signal is f CLK =24MHz, the frequency of the pulse signal f =1KHZ, then the phase resolution P LSB≈0.015°, the minimum capacitance value that can be distinguished is 0.02pF. When the frequency of the reference clock signal f CLK =240MHz, the frequency of the pulse signal f =1KHZ, then the phase resolution P LSB ≈0.0015°, and the minimum capacitance value that can be distinguished at this time is 0.002pF. Therefore, the phase resolution capability of the micro-capacitance detection method is improved by 10 times.

[0113] In one embodiment of the present invention, the phase resolution of the micro-capacitance detection method is changed by simultaneously changing the resistance value of the resistor and adjusting the frequency of the reference clock signal. For example, the resistance value of the resistor R = 10 Mohm, the reference clock frequency f CLK =600MHz, at this time the micro-capacitance detection method can distinguish a capacitance value of 0.00004pF.

[0114] In one embodiment of the present invention, the detection circuit has parasitic capacitance. Parasitic capacitance generally refers to the capacitance characteristics of inductors, resistors, chip pins, etc. under high frequency conditions. In fact, a resistor is equivalent to a capacitor, an inductor, and a resistor in series. The performance is not very obvious under low frequency conditions, but under high frequency conditions, the equivalent value will increase and cannot be ignored. In this embodiment, the parasitic capacitance can be regarded as being connected in parallel with the capacitive element in the detection circuit.

[0115] The present invention also provides a micro-capacitance detection device. Figure 6 , the micro-capacitance detection device 600 comprises:

[0116] The signal generating module 610 is used to generate a pulse signal. A pulse signal is a discrete signal with various shapes. Compared with a common analog signal (such as a sine wave), the waveforms are discontinuous on the vertical axis (there is a clear interval between the waveforms), but have a certain periodicity. Common pulse signals include rectangular pulses, sawtooth pulses, triangular pulses, spike pulses, step pulses, etc.

[0117] The detection circuit 620 is connected to the signal generating module 610 and is used to convert the pulse signal into a detection reference signal; after the detection circuit is connected to the micro-capacitor to be measured, it is used to convert the pulse signal into a detection signal. When the detection circuit 620 includes a capacitive element or is connected to a capacitive element, the pulse signal will produce a phase change after flowing through the detection circuit, that is, the pulse signal will produce a phase shift. The magnitude of the phase change depends on the capacitance value of the capacitive element included in the detection circuit and the capacitance value of the capacitive element connected to the detection circuit.

[0118] When the detection circuit 620 is not connected to the microcapacitor to be measured, the pulse signal flows through the detection circuit to form the detection reference signal. In particular, the detection circuit does not include a capacitive element and the detection circuit does not have a parasitic capacitor. At this time, the detection reference signal has the same phase as the pulse signal, that is, the phase difference is 0.

[0119] When the detection circuit 620 is connected to the micro-capacitor to be measured, the pulse signal flows through the detection circuit to form the detection signal.

[0120] The phase difference acquisition module 630 is connected to the output end of the detection circuit 620 and the signal generation module respectively, and is used to obtain the phase difference between the detection signal and the detection reference signal. The magnitude of the phase difference is related to the capacitance value of the micro-capacitor to be measured, so the capacitance value of the micro-capacitor to be measured can be calculated by the phase difference.

[0121] The calculation module 640 is connected to the phase difference acquisition module 630 and is used to calculate and obtain the capacitance value of the micro-capacitor to be measured according to the phase difference.

[0122] In one embodiment of the present invention, the signal generating module 610 includes: a clock unit 611, used to generate a reference clock signal; a divider unit 612, connected to the clock unit and the detection circuit, used to divide the reference clock signal to generate a first square wave signal; the first square wave signal is the pulse signal.

[0123] The reference clock signal is the basis of sequential logic. It is used to determine when the state in the logic unit is updated. It is a signal with a fixed period and is independent of the circuit operation status. The reference clock signal is usually used in synchronous circuits, plays the role of a timer, and constitutes the electronic components of the circuit. A common reference clock signal is a square wave signal with a 50% duty cycle.

[0124] The frequency division unit is implemented by a frequency divider. A frequency divider is a device that performs frequency division processing on an input signal and outputs a specific frequency component in the input signal. The frequency of the signal output by the frequency divider can be changed by setting the frequency division coefficient.

[0125] 2, the reference clock signal is input into the frequency divider 710, and the frequency divider 710 extracts the specific frequency component in the reference clock signal and outputs it to obtain a square wave signal of a specific frequency, which is marked as the first square wave signal drv. The first square wave signal is the pulse signal.

[0126] In one embodiment of the present invention, the phase difference acquisition module includes:

[0127] The shaping unit 631 is connected to the output end of the detection circuit 620, and is used to shape the detection reference signal to obtain a second square wave signal; after the detection circuit 620 is connected to the micro-capacitor to be measured, the shaping unit 631 is used to shape the detection signal to obtain a third square wave signal. The shaping unit 631 is used to shape the slowly changing or irregular signal into a signal with a steep edge, and can also be used to remove interference signals in the input signal, and can also realize the conversion of one waveform into another waveform. The shaping unit 631 can be a Schmitt trigger or a comparator. After shaping, the detection reference signal is shaped into a square wave signal, which is the second square wave signal.

[0128] The XOR unit 632 is connected to the shaping unit 631 and the signal generating module 610 respectively, and is used to perform a logical XOR process on the first square wave signal and the second square wave signal to obtain a first phase difference pulse; see Figure 2A , the first square wave signal drv and the second square wave signal fb1 are XORed, and both are high level or both are low level, and the corresponding low level is obtained after the XOR of the parts; one of the two is high level and the other is low level, and the corresponding high level is obtained after the XOR of the parts. Therefore, the gat1 signal is the first phase difference pulse obtained after the first square wave signal drv and the second square wave signal fb1 are XORed. In addition, there is a time difference between the rising edge of the second square wave signal fb1 and the rising edge of the first square wave signal drv, and the time difference is the width of the first phase difference pulse gat1. Therefore, the phase difference between the second square wave signal and the first square wave signal can be calculated according to the width of the first phase difference pulse gat1. The corresponding phase change of the first square wave signal within one sampling period is 2π, so the phase difference calculation formula between the second square wave signal and the first square wave signal is Wherein T represents the time length of one sampling period of the first square wave signal; t 1 represents the pulse width of the first phase difference pulse, t 1 <T.

[0129] After the detection circuit 620 is connected to the micro-capacitor to be measured, the XOR unit 632 is used to perform a logical XOR process on the first square wave signal and the third square wave signal to obtain a second phase difference pulse. Figure 2B, the first square wave signal drv and the third square wave signal fb2 are XORed, and both are high level or low level, and the corresponding low level is obtained after the XOR of part; one of them is high level and the other is low level, and the corresponding high level is obtained after the XOR of part. Therefore, the gat2 signal is the second phase difference pulse obtained after the first square wave signal drv and the third square wave signal fb2 are XORed. In addition, there is a time difference between the rising edge of the third square wave signal fb2 and the rising edge of the first square wave signal drv, and the time difference is the width of the second phase pulse gat2. Therefore, the phase difference between the third square wave signal and the first square wave signal can be calculated based on the width of the second phase difference pulse gat2. The corresponding phase change of the first square wave signal within one sampling period is 2π, so the calculation formula of the phase difference between the third square wave signal and the first square wave signal is Wherein T represents the time length of one sampling period of the first square wave signal; t 2 represents the pulse width of the second phase difference pulse, t 2 <T.

[0130] The phase difference calculation unit 633 is connected to the XOR unit 632 and is used to calculate the phase difference between the detection signal and the detection reference signal according to the pulse width of the first phase difference pulse and the pulse width of the second phase difference pulse. The calculation formula is: Where ΔP 1 is the phase difference between the detection signal and the detection reference signal; T represents the time length of one sampling cycle of the first square wave signal; t 1 represents the pulse width of the first phase difference pulse, t 2 represents the pulse width of the second phase difference pulse, t 1 <t 2 <T.

[0131] In one embodiment of the present invention, the phase difference calculation unit includes: a pulse width measurement subunit, connected to the XOR unit, for measuring the pulse width of the phase difference pulse using the reference clock signal. In this embodiment, the pulse width measurement subunit includes a logic AND circuit, and the logic AND circuit is used to perform a logic AND operation on the reference clock signal and the phase difference pulse signal to obtain a corresponding phase signal. The pulse width measurement subunit cooperates with a frequency meter to calculate the pulse width of the phase difference pulse according to the number of pulses contained in one cycle of the phase signal.

[0132] In one embodiment of the present invention, the detection circuit 620 includes: a first buffer 621, connected to the signal generating module, for buffering the pulse signal; a resistor 622; the first end of the resistor 622 is connected to the first buffer 621, and the second end is connected to the phase difference acquisition module 630; the pulse signal flows through the first buffer 621 and the resistor 622 and is converted into the detection reference signal; after the detection circuit 620 is connected to the microcapacitor to be measured, the pulse signal flows through the first buffer 621 and the resistor 622 and is converted into the detection signal.

[0133] When the detection circuit 620 is not connected to the micro-capacitor to be measured, the resistor 622 is connected in series with the capacitor in the detection circuit 620 to form an RC circuit. In particular, if the pulse signal is a square wave, then within one cycle of the pulse signal:

[0134] When the pulse signal is converted from a low level to a high level, the capacitor in the detection circuit 620 starts to charge. At this time, the voltage value at the connection point between the capacitor and the resistor 622 in the RC circuit is the detection reference signal, and its change relationship with time is: Where t represents time; U s represents the voltage value corresponding to the high level of the pulse signal; R is the resistance value of the resistor, and C is the capacitance value of the capacitor in the detection circuit. c (t) is the voltage of the detection reference signal, and its image changing with time is as follows: Figure 5A As shown in paragraph ①. When the time is long enough, the voltage of the detection reference signal is U s .

[0135] When the pulse signal is converted from a high level to a low level, the capacitor in the detection circuit 620 begins to discharge. At this time, the relationship between the voltage of the detection reference signal and time is: u c (t) is the voltage of the detection reference signal, and its image changing with time is as follows: Figure 5A As shown in paragraph ②, when the time is long enough, the voltage of the detection reference signal is 0.

[0136] In summary, Figure 5A It is shown as the voltage of the detection reference signal within one cycle of the pulse signal.

[0137] When the detection circuit is connected to the microcapacitor to be measured, the microcapacitor to be measured is connected in parallel with the capacitor in the detection circuit 620 and the resistor to form an RC circuit. In particular, if the pulse signal is a square wave, then within one cycle of the pulse signal:

[0138] When the pulse signal is converted from a low level to a high level, the capacitor in the detection circuit 620 starts to charge. At this time, the voltage value at the connection point between the capacitor and the resistor 622 in the RC circuit is the detection signal, and its change relationship with time is: Among them C x is the capacitance value of the microcapacitor to be measured; u' c (t) represents the voltage of the detection signal. When the time is long enough, the voltage of the detection signal is U s Compared with the detection reference signal, the detection signal increases more slowly.

[0139] When the pulse signal is converted from a high level to a low level, the capacitor in the detection circuit 620 begins to discharge. At this time, the relationship between the voltage of the detection reference signal and time is: When the time is long enough, the voltage of the detection signal is 0. Compared with the detection reference signal, the detection signal decreases more slowly.

[0140] In one embodiment of the present invention, the shaping unit 631 includes an input buffer; the input buffer is connected to the output end of the detection circuit, and is used to shape the detection reference signal and the detection signal. In particular, the input buffer is a Schmitt trigger. The Schmitt trigger has two stable states, but unlike a general trigger, the Schmitt trigger adopts a potential triggering method, and its state is maintained by the input signal potential; for input signals with two different change directions of negative decreasing and positive increasing, the Schmitt trigger has different threshold voltages.

[0141] See also Figure 5A ,Will Figure 5A The detection reference signal shown is used as the input signal of the input buffer: c (t) is greater than the threshold of the input buffer, the input buffer outputs a high level; when u c When (t) is less than or equal to the threshold of the input buffer, the input buffer outputs a low level. Figure 5B Displayed as Figure 5A The second square wave signal corresponding to the detection reference signal.

[0142] Similarly, when the detection circuit is connected to the micro-capacitor to be measured, the detection signal is used as the input signal of the input buffer: when the detection signal is greater than the threshold of the input buffer, the input buffer outputs a high level; when the detection signal is less than or equal to the threshold of the input buffer, the input buffer outputs a low level. Therefore, the detection signal can obtain a corresponding third wave signal after being shaped by the input buffer.

[0143] The calculation module 640 includes:

[0144] The conversion coefficient calculation unit 641 is connected to the phase difference acquisition module and is used to calculate the conversion coefficient between the phase difference and the capacitance value. The calculation formula of the conversion coefficient is: Wherein K represents the conversion coefficient between the phase difference and the capacitance value; f is the frequency of the pulse signal; R is the resistance value of the resistor; D is the voltage ratio of the threshold of the input buffer to the first square wave signal, and its value range is 0<D<1;

[0145] The capacitance value calculation unit 642 is connected to the conversion coefficient calculation unit and is used to calculate the capacitance value of the micro-capacitor to be measured. The calculation formula is C x =K×ΔP; where C x is the capacitance value of the micro-capacitor to be measured; ΔP is the phase difference between the detection signal and the detection reference signal.

[0146] In this embodiment, when the detection circuit 620 is not connected to the micro-capacitor to be measured, within one cycle of the pulse signal, when the voltage of the detection reference signal changes from low to high, the ratio of the voltage of the detection reference signal to the voltage of the first square wave signal is equal to D at time tt1, where tt1=-RC ln(1-D); therefore, when the detection circuit 620 is not connected to the micro-capacitor to be measured, the phase shift of the detection signal relative to the pulse signal is P 3 =-2πRCf ln(1-D).

[0147] When the detection circuit 620 is connected to the microcapacitor to be measured, within one cycle of the pulse signal, when the voltage of the detection signal changes from low to high, the ratio of the voltage of the detection signal to the voltage of the first square wave signal is equal to D at time tt2, where tt2=-R(C+C x )ln(1-D); Therefore, when the detection circuit 620 is connected to the micro-capacitor to be measured, the phase shift of the detection signal relative to the pulse signal is P 4 =-2πR(C+C x )f ln(1-D).

[0148] In summary, the phase difference between the detection signal and the detection reference signal ΔP=P 4 -P 3 =-2πRC x f ln(1-D). Where ΔP is the theoretical value of the phase difference. Therefore, if the phase difference ΔP is known, it can be calculated according to The capacitance value of the microcapacitor to be measured is obtained, therefore, That is, it is the conversion coefficient between the phase difference and the capacitance value.

[0149] In this embodiment, the measured phase difference ΔP 1 According to the formula C x =K×ΔP 1 The capacitance value of the microcapacitor to be measured is obtained by calculation.

[0150] In one embodiment of the present invention, the resistance value R=500Kohm, the frequency of the pulse signal f=1kHZ, the voltage ratio of the threshold of the input buffer to the first square wave signal Then the conversion coefficient K≈3.183×10 -10 At this time, the phase difference caused by introducing 1pF of the micro-capacitor to be measured is 0.124°.

[0151] In one embodiment of the present invention, the resistor is an internal resistance of a related element in the detection circuit, such as an internal resistance of a buffer.

[0152] In one embodiment of the present invention, the resistance value of the resistor can be changed; by changing the resistance value of the resistor, the phase resolution of the micro-capacitance detection method can be changed; the phase resolution represents the minimum capacitance value that can be detected by the micro-capacitance detection method.

[0153] Due to the phase difference introduced by the micro-capacitor to be measured, the magnitude of the phase difference depends on the frequency of the pulse signal, the resistance value, the threshold of the input buffer, and the capacitance value of the micro-capacitor to be measured. The phase difference is an angle, and the measurement of the phase difference depends on the accuracy of the specific measurement method; when the phase difference value is too small, the measurement error of the phase difference is large. Therefore, in order to ensure the accuracy of the measurement, the phase difference introduced by the micro-capacitor to be measured should be within an appropriate value range.

[0154] In this embodiment, the phase resolution of the micro-capacitance detection method is changed by changing the resistance value of the resistor. Assuming that the minimum phase difference that can be accurately detected by the phase difference measurement method is 0.124°: when the resistance value R = 500Kohm, the frequency of the pulse signal f = 1kHZ, the voltage ratio of the threshold of the input buffer to the first square wave signal At this time, the minimum capacitance that can be accurately detected by the micro-capacitance detection method is 1pF; when the resistance value R=5000Kohm, the frequency of the pulse signal f=1kHZ, the voltage ratio of the threshold of the input buffer to the first square wave signal At this time, the minimum capacitance value that can be accurately detected by the micro-capacitance detection method is 0.1pF, and the corresponding phase resolution capability is improved by 10 times. The resistance value of the resistor can be changed by using an adjustable resistor in the circuit, or by adding a new resistor in series or in parallel with the original resistor, or by replacing the original resistor with a resistor of a suitable resistance value.

[0155] In one embodiment of the present invention, the frequency of the reference clock signal generated by the clock unit can be adjusted; the phase resolution of the micro-capacitance detection method can be adjusted by adjusting the frequency of the reference clock signal; the relationship between the phase resolution and the frequency of the reference clock signal is: Among them, P LSB is the phase resolution, indicating the minimum capacitance value that can be detected by the micro-capacitance detection method; f is the frequency of the first square wave signal; f CLK is the frequency of the reference clock signal.

[0156] For example, when the frequency of the reference clock signal is f CLK =24MHz, the frequency of the pulse signal f =1KHZ, then the phase resolution P LSB ≈0.015°, the minimum capacitance value that can be distinguished is 0.02pF. When the frequency of the reference clock signal f CLK =240MHz, the frequency of the pulse signal f =1KHZ, then the phase resolution P LSB ≈0.0015°, and the minimum capacitance value that can be distinguished is 0.002pF. In comparison, the phase resolution capability of the microcapacitance detection method is improved by 10 times.

[0157] In one embodiment of the present invention, the phase resolution of the micro-capacitance detection method is changed by simultaneously changing the resistance value of the resistor and adjusting the frequency of the reference clock signal. For example, the resistance value of the resistor R = 10 Mohm, the reference clock frequency f CLK =600MHz, at this time the micro-capacitance detection method can distinguish a capacitance value of 0.00004pF.

[0158] In one embodiment of the present invention, the detection circuit has parasitic capacitance. Parasitic capacitance generally refers to the capacitance characteristics of inductors, resistors, chip pins, etc. under high frequency conditions. In fact, a resistor is equivalent to a capacitor, an inductor, and a resistor in series. This equivalence is not very obvious under low frequency conditions, but under high frequency conditions, the equivalent value will increase, and the parasitic capacitance at this time cannot be ignored. In this embodiment, the parasitic capacitance can be regarded as being connected in parallel with the capacitive element in the detection circuit.

[0159] In one embodiment of the present invention, the detection circuit includes a capacitive element, and the capacitive element may be a parasitic capacitor of the detection circuit, a capacitive element inside the detection circuit, or a capacitive element outside the detection circuit.

[0160] Fig. 7A The circuit diagram of the micro-capacitor detection device when the detection circuit described in this embodiment is not connected to the micro-capacitor to be measured is shown. The signal generating module is composed of a reference clock (not shown in the figure) and a frequency divider 710. The reference clock signal is a square wave, and the first square wave signal drv is obtained after frequency division. The resistor 730 and the capacitor 750 form an RC circuit, and the capacitor element can be a parasitic capacitor of the detection circuit, or a capacitor element inside the detection circuit, or a capacitor element outside the detection circuit. The first square wave signal drv flows through the first buffer 720 and the resistor 730 to form a detection reference signal in1. Thereafter, a Schmitt trigger 760 is used to obtain the detection reference signal in1 and shape it to obtain a second square wave signal fb1, and the second square wave signal fb1 and the first square wave signal drv are XORed by an XOR gate 770 to obtain a first phase difference pulse signal gat1; the first phase difference pulse signal gat1 and the reference clock signal clk are logically ANDed by an AND gate 770 to obtain a first phase signal phase1. Thereafter, a frequency meter is used to quantify the phase difference between the second square wave signal fb1 and the first square wave signal drv in each sampling period, that is, the frequency meter is used to obtain the number of pulses in the first phase signal phase1 in each sampling period, and then the phase difference is calculated.

[0161] Figure 7BThe diagram shows the connection relationship when the detection circuit described in this embodiment is connected to the micro-capacitor to be measured. The signal generating module is composed of a reference clock (not shown in the figure) and a frequency divider 710. The reference clock signal is a square wave, and the first square wave signal drv is obtained after frequency division. The resistor 730, the capacitor 750, and the micro-capacitor to be measured 740 form an RC circuit, and the capacitor 750 is a capacitive element in the detection circuit or a parasitic capacitor of the detection circuit. The first square wave signal drv flows through the first buffer 720 and the resistor 730 to form a detection signal in2. Thereafter, a Schmitt trigger 760 is used to obtain the detection signal in2 and perform shaping processing on it to obtain a third square wave signal fb2, and the third square wave signal fb2 and the first square wave signal drv are XORed by an XOR gate 770 to obtain a second phase difference pulse signal gat2; the second phase difference pulse signal gat2 and the reference clock signal clk are logically ANDed by an AND gate 770 to obtain a second phase signal phase2. The number of pulses in the second phase signal phase2 is proportional to the pulse width of the second phase difference pulse signal gat2. Afterwards, the phase difference between the third square wave signal fb2 and the first square wave signal drv is quantified in each sampling period using a frequency meter, that is, the number of pulses in the second phase signal phase2 in each sampling period is obtained using a frequency meter, and then the phase difference is calculated.

[0162] In one embodiment of the present invention, the detection circuit does not include any capacitive element and does not have any parasitic capacitance, and no capacitive element other than the micro-capacitor to be measured is connected to the detection circuit.

[0163] Fig. 8AThe circuit diagram of the micro-capacitor detection device when the detection circuit described in this embodiment is not connected to the micro-capacitor to be measured is shown. The signal generating module is composed of a reference clock (not shown in the figure) and a frequency divider 810. The reference clock signal is a square wave, and the first square wave signal drv is obtained after frequency division. The first square wave signal drv flows through the first buffer 820 and the resistor 830 to form a detection reference signal in1, and the detection reference signal in1 and the first square wave signal drv are both square waves. Subsequently, a Schmitt trigger 860 is used to obtain the detection reference signal in1 and perform shaping processing on it to obtain a second square wave signal fb1, and the second square wave signal fb1 and the first square wave signal drv are obtained after the XOR operation is performed by the XOR circuit 870 to obtain the first phase difference pulse signal gat1, and the phase pulse gat1 is 0 level in each cycle; the first phase difference pulse signal gat1 and the reference clock signal clk are obtained after the logic and operation is performed by the AND circuit 870 to obtain the first phase signal phase1, and the first phase signal phase1 is also 0 level in each cycle. At this time, the number of pulses in one cycle of the first phase signal phase1 obtained by using the frequency meter is 0, and the phase difference calculated is also 0.

[0164] Figure 7B The diagram shows the connection relationship when the detection circuit described in this embodiment is connected to the micro-capacitor to be measured. The signal generating module is composed of a reference clock (not shown in the figure) and a frequency divider 810. The reference clock signal is a square wave, and the first square wave signal drv is obtained after frequency division. The resistor 830 and the micro-capacitor to be measured 840 form an RC circuit, and the first square wave signal drv flows through the first buffer 820 and the resistor 830 to form a detection signal in2. Thereafter, a Schmitt trigger 860 is used to obtain the detection signal in2 and perform shaping processing on it to obtain a third wave signal fb2, and the third wave signal fb2 and the first square wave signal drv are subjected to an XOR operation through an XOR circuit 870 to obtain a second phase difference pulse signal gat2; the second phase difference pulse signal gat2 and the reference clock signal clk are subjected to a logic AND operation through an AND circuit 870 to obtain a second phase signal phase2. The number of pulses in the second phase signal phase2 is proportional to the pulse width of the second phase difference pulse signal gat2. Thereafter, a frequency meter is used to quantify the phase difference between the third square wave signal fb2 and the first square wave signal drv in each sampling period, that is, the frequency meter is used to obtain the number of pulses in the second phase signal phase2 in each sampling period, and then the phase difference is calculated.

[0165] The protection scope of the micro-capacitance detection method described in the present invention is not limited to the execution order of the steps listed in this embodiment. All solutions implemented by adding, reducing or replacing steps in the prior art based on the principles of the present invention are included in the protection scope of the present invention.

[0166] The present invention also provides a micro-capacitance detection device, which can implement the micro-capacitance detection method described in the present invention. However, the implementation device of the micro-capacitance detection method described in the present invention includes but is not limited to the structure of the micro-capacitance detection device listed in this embodiment. All structural deformations and replacements of the prior art made according to the principles of the present invention are included in the protection scope of the present invention.

[0167] In summary, the micro-capacitor detection method and device described in the present invention have the following beneficial effects: the micro-capacitor detection method is completely implemented by a digital circuit, and the external interface also uses a common IO port. The capacitance value of the micro-capacitor is converted into the phase difference of the detection signal, and the detection of the capacitance is achieved by detecting the phase difference. Traditional solutions generally realize the detection of tiny capacitance with the participation of analog circuit devices such as high-precision operational amplifiers, analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). Compared with the two, the micro-capacitor detection method described in the present invention has the advantages of fast detection speed and wide detection range. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0168] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A microcapacitance detection method, characterized in that: The micro-capacitance detection method comprises: generating a pulse signal; When the detection circuit is not connected to the micro-capacitor to be measured, the pulse signal is converted into a detection reference signal by using the detection circuit; When the detection circuit is connected to the micro-capacitor to be measured, the pulse signal is converted into a detection signal by using the detection circuit connected to the micro-capacitor to be measured; Obtaining a phase difference between the detection signal and the detection reference signal, wherein the magnitude of the phase difference is related to the capacitance value of the micro-capacitor to be measured; Obtaining the capacitance value of the micro-capacitor to be measured by calculation according to the phase difference includes: Implementing shaping of the detection reference signal and the detection signal through an input buffer; Calculate the conversion coefficient between the phase difference and the capacitance value, the calculation formula of the conversion coefficient is: Wherein K represents the conversion coefficient between the phase difference and the capacitance value, f is the frequency of the pulse signal, R is the resistance value of the resistor, and D is the voltage ratio of the threshold of the input buffer to the first square wave signal, and its value range is 0<D<1; and Calculate the capacitance value of the microcapacitor to be measured, the calculation formula is C x =K×ΔP, where C x is the capacitance value of the micro-capacitor to be measured, and ΔP is the phase difference between the detection signal and the detection reference signal.

2. The micro-capacitance detection method according to claim 1, characterized in that: The implementation process of generating a pulse signal includes: A frequency divider is used to perform frequency division processing on a reference clock signal to generate a first square wave signal; the first square wave signal is the pulse signal.

3. The micro-capacitance detection method according to claim 2, characterized in that: The implementation process of obtaining the phase difference between the detection signal and the detection reference signal includes: Reshaping the detection reference signal to obtain a second square wave signal; Performing a logical exclusive OR process on the first square wave signal and the second square wave signal to obtain a first phase difference pulse; Reshaping the detection signal to obtain a third wave signal; Performing a logical exclusive OR process on the first square wave signal and the third square wave signal to obtain a second phase difference pulse; The phase difference between the detection signal and the detection reference signal is calculated according to the pulse width of the first phase difference pulse and the pulse width of the second phase difference pulse, and the calculation formula is: Wherein ΔP1 is the phase difference between the detection signal and the detection reference signal; T represents the time length of one sampling cycle of the first square wave signal; t1 represents the pulse width of the first phase difference pulse, and t2 represents the pulse width of the second phase difference pulse. t1<t2<T.

4. The micro-capacitance detection method according to claim 3, characterized in that: A method for measuring the pulse width of the phase difference pulse includes: The pulse width of the phase difference pulse is measured using the reference clock signal.

5. The micro-capacitance detection method according to claim 2, characterized in that: The detection circuit includes a buffer and a resistor; the pulse signal is converted into the detection reference signal after passing through the buffer and the resistor; After the detection circuit is connected to the micro-capacitor to be measured, the pulse signal flows through the buffer and the resistor and is converted into the detection signal.

6. The micro-capacitance detection method according to claim 5, characterized in that: The micro-capacitance detection method further comprises: The resistance value of the resistor is changed to change the phase resolution of the micro-capacitance detection method; the phase resolution represents the minimum capacitance value that can be detected by the micro-capacitance detection method.

7. The micro-capacitance detection method according to claim 2, characterized in that: The micro-capacitance detection method further comprises: The frequency of the reference clock signal is adjusted to adjust the phase resolution of the micro-capacitance detection method; the relationship between the phase resolution and the frequency of the reference clock signal is: Among them, P LSB is the phase resolution, indicating the minimum capacitance value that can be detected by the micro-capacitance detection method; f is the frequency of the first square wave signal; f CLK is the frequency of the reference clock signal.

8. The micro-capacitance detection method according to claim 1, characterized in that: The detection circuit has parasitic capacitance.

9. A micro-capacitance detection device, characterized in that: The micro-capacitance detection device comprises: A signal generating module, used for generating a pulse signal; A detection circuit is connected to the signal generating module, and when the detection circuit is not connected to the micro-capacitor to be measured, the detection circuit is used to convert the pulse signal into a detection reference signal; after the detection circuit is connected to the micro-capacitor to be measured, the detection circuit is used to convert the pulse signal into a detection signal; A phase difference acquisition module, connected to the output end of the detection circuit and the signal generation module respectively, for acquiring a phase difference between the detection signal and the detection reference signal, wherein the magnitude of the phase difference is related to the capacitance value of the micro-capacitor to be measured; A calculation module is connected to the phase difference acquisition module and is used to calculate the capacitance value of the micro-capacitor to be measured according to the phase difference, wherein the calculation module is configured as follows: Implementing shaping of the detection reference signal and the detection signal through an input buffer; Calculate the conversion coefficient between the phase difference and the capacitance value, the calculation formula of the conversion coefficient is: Wherein K represents the conversion coefficient between the phase difference and the capacitance value, f is the frequency of the pulse signal, R is the resistance value of the resistor, and D is the voltage ratio of the threshold of the input buffer to the first square wave signal, and its value range is 0<D<1; and Calculate the capacitance value of the microcapacitor to be measured, the calculation formula is C x =K×ΔP, where C x is the capacitance value of the micro-capacitor to be measured, and ΔP is the phase difference between the detection signal and the detection reference signal.

10. The micro-capacitance detection device according to claim 9, characterized in that: The signal generating module comprises: A clock unit, used for generating a reference clock signal; The frequency divider unit is connected to the clock unit and the detection circuit, and is used to perform frequency division processing on the reference clock signal to generate a first square wave signal; the first square wave signal is the pulse signal.

11. The micro-capacitance detection device according to claim 10, characterized in that: The phase difference acquisition module comprises: A shaping unit is connected to the output end of the detection circuit and is used to shape the detection reference signal to obtain a second square wave signal; after the detection circuit is connected to the micro-capacitor to be measured, the shaping unit is used to shape the detection signal to obtain a third square wave signal; An XOR unit is connected to the shaping unit and the signal generating module respectively, and is used to perform a logical XOR process on the first square wave signal and the second square wave signal to obtain a first phase difference pulse; after the detection circuit is connected to the microcapacitor to be measured, the XOR unit is used to perform a logical XOR process on the first square wave signal and the third square wave signal to obtain a second phase difference pulse; A phase difference calculation unit is connected to the XOR unit and is used to calculate the phase difference between the detection signal and the detection reference signal according to the pulse width of the first phase difference pulse and the pulse width of the second phase difference pulse. The calculation formula is: Wherein ΔP1 is the phase difference between the detection signal and the detection reference signal; T represents the time length of a sampling cycle of the first square wave signal; t1 represents the pulse width of the first phase difference pulse, t2 represents the pulse width of the second phase difference pulse, and t1<t2<T.

12. The micro-capacitance detection device according to claim 11, characterized in that: The phase difference calculation unit comprises: The pulse width measurement subunit is connected to the XOR unit and is used to measure the pulse width of the phase difference pulse using the reference clock signal.

13. The micro-capacitance detection device according to claim 11, characterized in that: The detection circuit comprises: A first buffer, connected to the signal generating module, and used for buffering the pulse signal; resistor; the first end of the resistor is connected to the first buffer, and the second end is connected to the phase difference acquisition module; the pulse signal flows through the first buffer and the resistor and is converted into the detection reference signal; after the detection circuit is connected to the microcapacitor to be measured, the pulse signal flows through the first buffer and the resistor and is converted into the detection signal.

14. The micro-capacitance detection device according to claim 13, characterized in that: The resistance value of the resistor can be changed; the phase resolution of the micro-capacitance detection device can be changed by changing the resistance value of the resistor; the phase resolution represents the minimum capacitance value that can be detected by the micro-capacitance detection device.

15. The micro-capacitance detection device according to claim 10, characterized in that: The frequency of the reference clock signal generated by the clock unit can be adjusted; the phase resolution of the micro-capacitance detection device can be adjusted by adjusting the frequency of the reference clock signal; the relationship between the phase resolution and the frequency of the reference clock signal is: Among them, P LSB is the phase resolution, indicating the minimum capacitance value that can be detected by the micro-capacitance detection device; f is the frequency of the first square wave signal; f CLK is the frequency of the reference clock signal.

16. The micro-capacitance detection device according to claim 9, characterized in that: The detection circuit has parasitic capacitance.

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