A Capacitance Measurement Integrated Circuit and Measurement Method Based on Time Parameters

Abstract

The present invention provides a capacitance measurement integrated circuit and a measurement method based on time parameters. According to the time characteristics of capacitance, through a simple analog-to-digital circuit module, the function of measuring the capacitance value by setting simple parameters is realized. The present invention provides a method and a circuit for simply measuring the capacitance value, which greatly reduces the test cost. The circuit module of the present invention is simple and concise, with clear logic and convenient implementation.

Description

Technical Field

[0001] The present invention belongs to the technical field of component measurement, and particularly relates to a capacitance measurement integrated circuit and a measurement method based on time parameters. Background Art

[0002] Existing measurement systems for measuring capacitors with time-dependent parameters include a waveform function generator module, a capacitor under test module, an oscilloscope module, an integrator module, a data processing module, a single-chip microcomputer MCU module, and a display module. The output end of the waveform function generator module is signal-connected to the input end of the capacitor under test module, the output end of the capacitor under test module is electrically connected to the input end of the oscilloscope module, the output end of the oscilloscope module is signal-connected to the input end of the integrator module, the output end of the integrator module is signal-connected to the input end of the data processing module, the output end of the data processing module is signal-connected to the input end of the single-chip microcomputer MCU module, and the output end of the single-chip microcomputer MCU module is signal-connected to the input end of the display module. This system realizes the measurement of the capacitance-time characteristics of capacitors with time-dependent parameters, but the defect is that the measurement logic is complex and the circuit modules used are numerous. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a capacitance measurement integrated circuit and a measurement method based on time parameters for measuring the capacitance value of a capacitor by setting simple parameters.

[0004] The technical solution adopted by the present invention to solve the above technical problem is: a capacitance measurement integrated circuit based on time parameters, characterized in that it includes a capacitance-to-time module, a time-to-voltage module, and a numerical conversion module; the capacitance-to-time module includes a voltage comparator module for providing a pulse signal according to the size of the capacitor to be measured; the time-to-voltage module includes a first integration module and a second integration module for obtaining an analog voltage value according to the pulse signal; the numerical conversion module includes a proportional conversion circuit for converting the analog voltage value into a measured capacitance value and outputting it.

[0005] According to the above solution, the first integration module includes a first operational amplifier D1, a first resistor R1, a tenth resistor R10, and a capacitor under test C; the inverting input end of the first operational amplifier D1 is connected to the pulse signal end through the series connection of the first resistor R1, so as to input a first time pulse signal U1, and the first time pulse signal U1 is used to control the time parameter and determine the length and measurement accuracy of the measurement time; the non-inverting input end of the first operational amplifier D1 is grounded through the series connection of the tenth resistor R10; the capacitor under test C is connected in parallel between the inverting input end and the output end of the first operational amplifier D1; assuming the integration time is t, the output voltage U2 of the output end of the first operational amplifier D1 is:

[0006]

[0007] Further, the voltage comparator module includes a second operational amplifier D2, a second resistor R2, and a third resistor R3; the inverting input terminal of the second operational amplifier D2 is connected to the output terminal of the first operational amplifier D1 through the series connection of the third resistor R3, thereby inputting the voltage U2; at the same time, the inverting input terminal of the second operational amplifier D2 inputs the reference voltage U-ref through the series connection of the second resistor R2; the non-inverting input terminal of the second operational amplifier D2 is grounded; the output terminal of the second operational amplifier D2 outputs the voltage U3.

[0008] Further, it further includes a switch module; the switch module includes a MOS transistor M1, a ninth resistor R9, and a multiplexer D3; the gate of the MOS transistor M1 is connected to the output terminal of the second operational amplifier D2, thereby inputting the voltage U3, which is used to control the working time of the second integration module; the drain of the MOS transistor M1 is connected to the power supply terminal through the series connection of the ninth resistor R9, thereby inputting the voltage Vcc; the drain of the MOS transistor M1 is also connected to the data channel selection terminal of the multiplexer D3; the source of the MOS transistor M1 is grounded and the data input terminal 0 of the multiplexer D3; the data input terminal 1 of the multiplexer D3 is connected to the pulse signal terminal, thereby inputting the first time pulse signal U1; the output terminal of the multiplexer D3 outputs the voltage U4.

[0009] Further, the second integration module includes a fourth operational amplifier D4, a fourth resistor R4, an eighth resistor R8, and a first capacitor C1; the inverting input terminal of the fourth operational amplifier D4 is connected to the output terminal of the multiplexer D3 through the series connection of the fourth resistor R4, thereby inputting the voltage U4; the non-inverting input terminal of the fourth operational amplifier D4 is grounded through the series connection of the eighth resistor R8; the first capacitor C1 is connected in parallel between the inverting input terminal and the output terminal of the fourth operational amplifier D4; the output terminal of the fourth operational amplifier D4 outputs the voltage U5;

[0010] When the circuit is powered on, U3 = -Vcc, the MOS transistor M1 is cut off, U4 = U1, and the second integration module starts to work;

[0011] Let the threshold voltage be Ut, and the relationship between the threshold voltage Ut and the reference voltage U-ref is:

[0012]

[0013] When the output voltage U2 of the first integration module is greater than the threshold voltage Ut, U3 = Vcc, the MOS transistor M1 is turned on, U4 = 0, the second integration module stops working, and U5 maintains the voltage value before stopping;

[0014] According to Formula (1) and Formula (2), the relationship between the capacitance C to be measured and the integration time t is obtained as:

[0015]

[0016] The output voltage U5 at the output terminal of the fourth operational amplifier D4 is obtained from the integration time t as:

[0017]

[0018] Further, the ratio conversion circuit includes a fifth operational amplifier D5, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; the inverting input terminal of the fifth operational amplifier D5 is connected to the output terminal of the fourth operational amplifier D4 through the series connection of the fifth resistor R5, thereby inputting a voltage U5; the non-inverting input terminal of the fifth operational amplifier D5 is grounded through the series connection of the seventh resistor R7; the sixth resistor R6 is connected in parallel between the inverting input terminal and the output terminal of the fifth operational amplifier D5; the output terminal of the fifth operational amplifier D5 outputs a voltage U0;

[0019] As can be seen from formula (4), U5 and the capacitance to be measured C have a linear proportional relationship. According to the ratio conversion circuit, the capacitance value can be directly read out through the voltage, that is, the value of the capacitance to be measured C is the same as the value of U0; the parameters set by the ratio conversion circuit satisfy the following conditions:

[0020]

[0021] A capacitance measurement method based on time parameters includes the following steps:

[0022] S1: The first integration module and the second integration module start working from the starting time of the measurement;

[0023] S2: When the output voltage value of the first integration module is greater than the reference voltage, the voltage comparator module generates a first time pulse signal;

[0024] S3: The first time pulse signal is used as the stop signal of the second integration module. At this time, the voltage value of the second integration module remains unchanged;

[0025] S4: The ratio conversion circuit directly converts the voltage value output by the second integration module into a capacitance value that can be read and has only equal numerical values through a functional relationship;

[0026] S5: Read the voltage value at the output terminal and directly use it as the capacitance value of the capacitance to be measured.

[0027] A computer storage medium stores a computer program executable by a computer processor, and the computer program executes a capacitance measurement method based on time parameters.

[0028] The beneficial effects of the present invention are as follows:

[0029] 1. The capacitance measurement integrated circuit and measurement method based on time parameters of the present invention realize the function of measuring the capacitance value by setting simple parameters through a simple analog-to-digital circuit module according to the time characteristics of the capacitance.

[0030] 2. The present invention provides a method and a circuit for simply measuring the capacitance value, which greatly reduces the test cost.

[0031] 3. The circuit module of the present invention is simple and concise, with clear logic and convenient implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the principle block diagram of an embodiment of the present invention.

[0033] Figure 2 is the flowchart of an embodiment of the present invention.

[0034] Figure 3 is the circuit diagram of an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0036] Refer to Figure 1 , the embodiments of the present invention include a capacitance-to-time module, a time-to-voltage module, and a numerical conversion module;

[0037] The capacitance-to-time module is used to provide a first time pulse signal according to the size of the capacitance to be measured;

[0038] The time-to-voltage module is used to obtain an analog voltage value according to the pulse signal;

[0039] The numerical conversion module is used to convert the analog voltage value into a measured capacitance value.

[0040] Refer to Figure 3 , U1 is a pulse voltage for time parameter control, and the magnitude of U1 determines the measurement time length and measurement accuracy.

[0041] U2 is the output voltage of the first part of the integration module, and the capacitance to be measured is included in the first integration module.

[0042]

[0043] U3 is the output voltage of the voltage comparator module. U3 is used as the input of the switching MOS transistor to control the working time of the second part of the integration circuit. When the circuit is turned on, the output voltage of U3 is -Vcc, and the MOS transistor is in the cut-off state. The output of U4 is U1. When the output voltage U2 of the first part of the integration circuit exceeds the threshold voltage Ut, the output voltage of U3 is Vcc, the MOS transistor is turned on, the output voltage of U4 is 0, the second part of the integration circuit stops working, and U5 maintains the voltage value before stopping.

[0044]

[0045] According to Formula (1) and Formula (2), the relationship between the measured capacitance C and the integration end time t can be obtained:

[0046]

[0047] From the integration time t, the final voltage value U5 of the second part can be obtained:

[0048]

[0049] As can be seen from Formula Four, U5 and the capacitance C are in a linear proportional relationship. According to the final part of the proportional conversion circuit, the capacitance value can be directly read out through the voltage, that is, the value of C is the value of U0. The parameters set by the proportional conversion circuit must meet the following conditions:

[0050]

[0051] See Figure 2 , the capacitance measurement method of the present invention includes the following steps:

[0052] S1: Two integration circuits start working from the starting time of the measurement;

[0053] S2: When the output voltage value of the integration circuit including the measured capacitance is greater than the reference voltage, the voltage comparator generates a first time pulse signal;

[0054] S3: Take this pulse signal as the stop signal of the integration circuit. At this time, the voltage value of the integration circuit remains unchanged;

[0055] S4: The numerical conversion circuit directly converts the voltage value output by the integration circuit into a readable capacitance value with only equal numerical values through a functional relationship;

[0056] S5: Directly take the voltage value read at the output end as the capacitance value.

[0057] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made according to the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A capacitance measurement integrated circuit based on time parameters, characterized in that: it includes a capacitance-to-time module, a time-to-voltage module, and a numerical conversion module; The capacitance-to-time module includes a voltage comparator module for providing a pulse signal according to the size of the capacitance to be measured; The time-to-voltage module includes a first integration module and a second integration module for obtaining an analog voltage value according to the pulse signal; The numerical conversion module includes a proportional conversion circuit for converting the analog voltage value into a measured capacitance value and outputting it; The first integration module includes a first operational amplifier D1, a first resistor R1, a tenth resistor R10, and a capacitance to be measured C; the inverting input terminal of the first operational amplifier D1 is connected to the pulse signal terminal after being serially connected with the first resistor R1, thereby inputting a first time pulse signal U1, and the first time pulse signal U1 is used to control the time parameter and determine the length and measurement accuracy of the measurement time; the non-inverting input terminal of the first operational amplifier D1 is grounded after being serially connected with the tenth resistor R10; the capacitance to be measured C is connected in parallel between the inverting input terminal and the output terminal of the first operational amplifier D1; assuming the integration time is t, the output voltage U2 at the output terminal of the first operational amplifier D1 is: U2 = - U1 * t(1); The voltage comparator module includes a second operational amplifier D2, a second resistor R2, and a third resistor R3; the inverting input terminal of the second operational amplifier D2 is connected to the output terminal of the first operational amplifier D1 after being serially connected with the third resistor R3, thereby inputting the voltage U2; at the same time, the inverting input terminal of the second operational amplifier D2 inputs a reference voltage U-ref after being serially connected with the second resistor R2; the non-inverting input terminal of the second operational amplifier D2 is grounded; the output terminal of the second operational amplifier D2 outputs a voltage U3; It further includes a switch module; the switch module includes a MOS transistor M1, a ninth resistor R9, and a multiplexer D3; the gate of the MOS transistor M1 is connected to the output terminal of the second operational amplifier D2, thereby inputting the voltage U3, which is used to control the working time of the second integration module; the drain of the MOS transistor M1 is connected to the power supply terminal after being serially connected with the ninth resistor R9, thereby inputting the voltage Vcc; the drain of the MOS transistor M1 is also connected to the data channel selection terminal of the multiplexer D3; the source of the MOS transistor M1 is grounded and the data input terminal 0 of the multiplexer D3; the data input terminal 1 of the multiplexer D3 is connected to the pulse signal terminal, thereby inputting the first time pulse signal U1; The output terminal of the multiplexer D3 outputs a voltage U4.

2. A capacitance measurement integrated circuit based on time parameters according to claim 1, characterized in that: The second integration module includes a fourth operational amplifier D4, a fourth resistor R4, an eighth resistor R8, and a first capacitor C1; the inverting input terminal of the fourth operational amplifier D4 is connected to the output terminal of the multiplexer D3 after being serially connected with the fourth resistor R4, thereby inputting the voltage U4; the non-inverting input terminal of the fourth operational amplifier D4 is grounded after being serially connected with the eighth resistor R8; the first capacitor C1 is connected in parallel between the inverting input terminal and the output terminal of the fourth operational amplifier D4; the output terminal of the fourth operational amplifier D4 outputs a voltage U5; When the circuit is powered on, U3 = -Vcc, the MOS transistor M1 is cut off, U4 = U1, and the second integration module starts to work; Assuming the threshold voltage is Ut, the relationship between the threshold voltage Ut and the reference voltage U-ref is: Ut = - U-ref(2), When the output voltage U2 of the first integration module is greater than the threshold voltage Ut, U3 = Vcc, the MOS transistor M1 is turned on, U4 = 0, the second integration module stops working, and U5 maintains the voltage value before stopping; According to formulas (1) and (2), the relationship between the capacitance C to be measured and the integration time t is obtained as: t = （3）， From the integration time t, the output voltage U5 at the output terminal of the fourth operational amplifier D4 is obtained as: U5 = - （4）。 3. A capacitance measurement integrated circuit based on time parameters according to claim 2, characterized in that: The proportional conversion circuit includes a fifth operational amplifier D5, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7; the inverting input terminal of the fifth operational amplifier D5 is connected to the output terminal of the fourth operational amplifier D4 through the series connection of the fifth resistor R5, thereby inputting the voltage U5; the non-inverting input terminal of the fifth operational amplifier D5 is grounded through the series connection of the seventh resistor R7; The sixth resistor R6 is connected in parallel between the inverting input terminal and the output terminal of the fifth operational amplifier D5; the output terminal of the fifth operational amplifier D5 outputs the voltage U0; It can be seen from formula (4) that U5 and the capacitance C to be measured are in a linear proportional relationship. According to the proportional conversion circuit, the capacitance value can be directly read out through the voltage, that is, the value of the capacitance C to be measured is the same as the value of U0; the parameters set by the proportional conversion circuit satisfy the following conditions: = （5）。 4. A measurement method for a capacitance measurement integrated circuit based on time parameters according to any one of claims 1 to 3, characterized in that: It includes the following steps: S1: The first integration module and the second integration module start working from the starting time of the measurement; S2: When the output voltage value of the first integration module is greater than the reference voltage, the voltage comparator module generates a first time pulse signal; S3: The first time pulse signal is used as the stop signal of the second integration module. At this time, the voltage value of the second integration module remains unchanged; S4: The proportional conversion circuit directly converts the voltage value output by the second integration module into a readable capacitance value with only equal numerical values through a functional relationship; S5: Read the voltage value at the output terminal and directly use it as the capacitance value of the capacitance to be measured.

5. A computer storage medium, characterized in that: It stores a computer program executable by a computer processor, and this computer program executes a capacitance measurement method based on time parameters as described in claim 4.

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