CN218037070U

CN218037070U - Capacitance measurement chip, universal meter and capacitance measurement circuit

Info

Publication number: CN218037070U
Application number: CN202221209534.1U
Authority: CN
Inventors: 黄海; 杨宏; 吕尧明; 程飞; 吴清源
Original assignee: Hangzhou Mixin Microelectronic Co ltd
Current assignee: Hangzhou Mixin Microelectronic Co ltd
Priority date: 2022-05-19
Filing date: 2022-05-19
Publication date: 2022-12-13
Anticipated expiration: 2032-05-19

Abstract

The utility model relates to an electric capacity detects technical field, discloses an electric capacity measuring chip and universal meter, electric capacity measuring circuit, include: the device comprises a small capacitance measuring unit and a large capacitance measuring unit, wherein in the process of measuring the capacitance to be measured, the large capacitance measuring unit is used for detecting the capacitance to be measured and judging whether the capacitance to be measured is large capacitance or small capacitance; and when the capacitor to be detected is a small capacitor, the small capacitor measuring unit is adopted to detect the capacitance of the capacitor to be detected. The utility model discloses can guarantee the electric capacity that awaits measuring in the small scale and the electric capacity that awaits measuring in very big scope simultaneously, all obtain accurate, quick test.

Description

Capacitance measurement chip, universal meter and capacitance measurement circuit

Technical Field

The utility model relates to a capacitance detection technical field specifically is a capacitance measurement chip and universal meter, capacitance measurement circuit.

Background

Capacitance measurement is a typical application of a multimeter, and in the current multimeter chip, a bridge method or a charge-discharge method is generally adopted for capacitance measurement. The bridge method has the advantages of high test speed, insensitivity to parasitic capacitance in a test circuit and capability of testing very small capacitance. However, if the capacitance to be measured is too large, the equivalent impedance of the capacitance to be measured is reduced, and the result error of the test is very large due to the parasitic resistance of the capacitance to be measured. Therefore, the bridge method is only suitable for small capacitance test. The charging and discharging method can test a large capacitor by calculating the time required by charging and discharging through ceaseless charging and discharging of the capacitor, but the method is obviously influenced by the parasitic capacitance, and an accurate test result can be obtained only when the capacitance to be tested is far more than the parasitic capacitance. Therefore, the charge-discharge method is generally only suitable for testing large capacitors. Therefore, a measuring chip capable of simultaneously applying a large capacitance and a small capacitance is required.

Disclosure of Invention

An object of the utility model is to overcome the problem that current universal meter chip can not be used for detecting big electric capacity and little electric capacity simultaneously, provide an electric capacity measuring chip and universal meter, electric capacity measuring circuit.

In order to achieve the above object, the present invention provides a method comprising: the device comprises a first pin A0, a second pin A1, an analog ground pin AGND, a small capacitance measuring unit and a large capacitance measuring unit, wherein the first pin is respectively connected with a first end of the small capacitance measuring unit and a first end of the large capacitance measuring unit, the second pin is respectively connected with a second end of the small capacitance measuring unit and a second end of the large capacitance measuring unit, and the analog ground pin is connected with a third end of the small capacitance measuring unit;

the first pin A0 is connected with one end of an external first reference resistor Rref1, the second pin A1 is connected with one end of an external second reference resistor Rref2, the analog ground pin AGND is connected with one end of an external capacitor to be tested through a black pen, and the other end of the capacitor to be tested is respectively connected with the other end of the first reference resistor Rref1 and the other end of the second reference resistor Rref2 through a red pen;

in the process of measuring the capacitor to be measured, firstly, the large capacitor measuring unit is adopted to detect the capacitor to be measured, and the capacitor to be measured is judged to be a large capacitor or a small capacitor; and when the capacitor to be detected is a small capacitor, the small capacitor measuring unit is adopted to detect the capacitance of the capacitor to be detected.

As an implementable manner, the large capacitance measuring unit includes a current source I, a first switch SW1, a second switch SW2, a third switch SW5, a first comparator, a second comparator, a first reference voltage VREF1, a second reference voltage VREF2, and a counter;

the current source I is respectively connected with a working voltage VDD and a ground end GND, the current source I is connected with the first end of the large capacitance measuring unit through the first switch SW1 and used for charging the capacitor to be measured, and the current source I is connected with the first end of the large capacitance measuring unit through the second switch SW2 and used for discharging the capacitor to be measured; a second end of the large capacitance measuring unit is connected with a first input end of the first comparator and a first input end of the second comparator through the third switch SW5, a second input end of the first comparator is connected with the first reference voltage VREF1, a second input end of the second comparator is connected with the second reference voltage VREF2, and an output end of the first comparator and an output end of the second comparator are connected with the counter respectively;

when the large capacitance measuring unit is used for detecting the capacitance of the capacitor to be detected, the first switch SW1 is firstly closed, the second switch SW2 is opened, the third switch SW5 is closed, the current source I charges the capacitor Cx to be detected, when the voltage value of the capacitor Cx exceeds the voltage value of the first reference voltage VREF1 input by the second input end of the first comparator, the charging is completed, the first switch SW1 is opened, the second switch SW2 is closed, the third switch SW5 is closed, the current source I discharges the capacitor Cx to be detected, and when the voltage value of the capacitor Cx is lower than the voltage value of the second reference voltage VREF2 input by the second input end of the second comparator, the discharging is completed; the counter is used for calculating the time of one-time charge and discharge in a circulating mode.

As an implementation manner, when the large capacitance measuring unit is used to detect the capacitance of the capacitor to be measured, the calculation formula is as follows: cx = T × I/(VREF 1 — VREF 2), where Cx denotes a capacitance of the capacitor to be measured, VREF1 denotes a voltage value of the first reference voltage VREF1, VREF2 denotes a voltage value of the second reference voltage VREF2, I denotes a current value output by the current source I, and T denotes a time of one charge and discharge cycle calculated by the counter.

As an implementation, the small capacitance measuring unit includes a first operational amplifier OP1, a second operational amplifier OP2, a fourth switch SW3, a fifth switch SW4, a sixth switch SW6, a seventh switch SW7, a sinusoidal signal source VSIN, and an ADC module;

the first end of the small capacitance measuring unit is connected with the output end of the second operational amplifier through the fourth switch SW3, and the first end of the small capacitance measuring unit is connected with the first pin of the ADC module; a second end of the small capacitance measuring unit is connected with a second pin of the ADC module, a second end of the small capacitance measuring unit is connected with a reverse input end of the second operational amplifier unit through the fifth switch SW4, a third end of the small capacitance measuring unit is respectively connected with a third pin of the ADC module, a reverse input end of the first operational amplifier, and an output end of the first operational amplifier, a forward input end of the first operational amplifier is connected with a ground terminal through the sixth switch SW6, and a forward input end of the first operational amplifier is connected with the ground terminal through the seventh switch SW7 and the sinusoidal signal source VSIN in sequence;

when the large-capacitance measuring unit is used for detecting the capacitance of the capacitor to be detected, the sixth switch SW6 is closed, and the fourth switch SW3, the fifth switch SW4 and the seventh switch SW7 are opened; when the small-capacitance measuring unit is used for detecting the capacitance of the capacitor to be detected, the sixth switch SW6 is turned off, the fourth switch SW3, the fifth switch SW4 and the seventh switch SW7 are turned on, the sinusoidal signal output by the sinusoidal signal source VSIN reaches one end of the capacitor to be detected Cx through the first operational amplifier OP1 and the black stylus, the current output by the other end of the capacitor to be detected Cx passes through the first reference resistor Rref1, and the ADC module is used for detecting the voltage values at the two ends of the first reference resistor Rref1 and detecting the amplitude value of the sinusoidal signal output by the sinusoidal signal source VSIN.

As an implementation manner, when the large capacitance measuring unit is used to detect the capacitance of the capacitor to be measured, the calculation formula is as follows: cx = VR/(VSIN Rref2 pi f), where Cx represents a capacitance of the capacitor under test, VR represents a voltage value across the first reference resistor Rref1, VSIN represents an amplitude value of the sinusoidal signal output by the sinusoidal signal source VSIN, and f represents a frequency value of the sinusoidal signal output by the sinusoidal signal source VSIN.

Correspondingly, the utility model also provides a universal meter, include like arbitrary any electric capacity measurement chip.

Correspondingly, the utility model also provides an electric capacity measuring circuit, include as arbitrary the electric capacity measuring chip. The utility model has the advantages of: the utility model provides a pair of electric capacity measuring chip and universal meter, electric capacity measuring circuit, include: the device comprises a small capacitance measuring unit and a large capacitance measuring unit, wherein in the process of measuring the capacitance to be measured, the large capacitance measuring unit is used for detecting the capacitance to be measured and judging whether the capacitance to be measured is large capacitance or small capacitance; when the capacitor to be detected is a large capacitor, the large capacitor measuring unit is continuously adopted to detect the capacitance of the capacitor to be detected, and when the capacitor to be detected is a small capacitor, the small capacitor measuring unit is adopted to detect the capacitance of the capacitor to be detected; the utility model discloses can guarantee the electric capacity that awaits measuring in the small scale and the electric capacity that awaits measuring in very big scope simultaneously, all obtain accurate, quick test.

Drawings

Fig. 1 is a schematic diagram of a capacitance measuring circuit according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

As shown in fig. 1, the present embodiment provides a technical solution: a capacitance measurement chip, the capacitance measurement chip 100 comprising: the device comprises a first pin A0, a second pin A1, an analog ground pin AGND, a small capacitance measuring unit and a large capacitance measuring unit, wherein the first pin is respectively connected with a first end of the small capacitance measuring unit and a first end of the large capacitance measuring unit, the second pin is respectively connected with a second end of the small capacitance measuring unit and a second end of the large capacitance measuring unit, and the analog ground pin is connected with a third end of the small capacitance measuring unit;

the first pin A0 is connected with one end of an external first reference resistor Rref1, the second pin A1 is connected with one end of an external second reference resistor Rref2, the analog ground pin AGND is connected with one end of an external capacitor to be tested through a black pen 2, and the other end of the capacitor to be tested is respectively connected with the other end of the first reference resistor Rref1 and the other end of the second reference resistor Rref2 through a red pen 1;

The large capacitance measuring unit comprises a current source I, a first switch SW1, a second switch SW2, a third switch SW5, a first comparator 10, a second comparator 20, a first reference voltage VREF1, a second reference voltage VREF2 and a counter 30;

the current source I is respectively connected with a working voltage VDD and a ground end GND, the current source I is connected with the first end of the large capacitance measuring unit through the first switch SW1 and used for charging the capacitor to be measured, and the current source I is connected with the first end of the large capacitance measuring unit through the second switch SW2 and used for discharging the capacitor to be measured; a second end of the large capacitance measuring unit is respectively connected with a first input end of the first comparator and a first input end of the second comparator through the third switch SW5, a second input end of the first comparator is connected with the first reference voltage VREF1, a second input end of the second comparator is connected with the second reference voltage VREF2, and an output end of the first comparator and an output end of the second comparator are respectively connected with the counter;

when the large-capacitance measuring unit is used for detecting the capacitance of the capacitor to be detected, the first switch SW1 is firstly closed, the second switch SW2 is opened, the third switch SW5 is closed, the current source I charges the capacitor Cx to be detected, when the voltage value of the capacitor Cx exceeds the voltage value of the first reference voltage VREF1 input by the second input end of the first comparator, the charging is completed, the first switch SW1 is opened, the second switch SW2 is closed, the third switch SW5 is closed, the current source I discharges the capacitor Cx to be detected, and when the voltage value of the capacitor Cx is lower than the voltage value of the second reference voltage VREF2 input by the second input end of the second comparator, the discharging is completed; the counter is used for calculating the time of one-time charge and discharge of the cycle.

When the large capacitance measuring unit is adopted to detect the capacitance of the capacitor to be detected, the calculation formula is as follows: cx = T ×/(VREF 1 — VREF 2), where Cx represents a capacitance of the capacitor to be measured, VREF1 represents a voltage value of the first reference voltage VREF1, VREF2 represents a voltage value of the second reference voltage VREF2, I represents a current value output by the current source I, and T represents a time of one charge and discharge cycle calculated by the counter.

The small capacitance measuring unit comprises a first operational amplifier OP1, a second operational amplifier OP2, a fourth switch SW3, a fifth switch SW4, a sixth switch SW6, a seventh switch SW7, a sinusoidal signal source VSIN and an ADC module;

When the large-capacitance measuring unit is adopted to detect the capacitance of the capacitor to be detected, the calculation formula is as follows: cx = VR/(VSIN × Rref × 2 × pi × f), where Cx represents a capacitance of the capacitor to be measured, VR represents a voltage value across the first reference resistor Rref1, VSIN represents an amplitude value of a sinusoidal signal output by the sinusoidal signal source VSIN, and f represents a frequency value of the sinusoidal signal output by the sinusoidal signal source VSIN, where the above formula is derived by transforming the voltage value VR = VSIN × Rref (2 × pi f Cx) across the first reference resistor Rref 1.

As shown in fig. 1, the embodiment of the present invention integrates both the large capacitance testing unit and the small capacitance testing unit into one capacitance measuring chip 100, and the user can select the most suitable testing method for different capacitances to be tested; specifically, firstly, a large capacitance measuring unit is used for carrying out one-time charging and discharging test on the capacitance Cx to be measured, whether the capacitance Cx to be measured belongs to a small capacitance or a large capacitance is judged, and a specific judgment standard can be set by a user according to needs; if the small capacitance range output by the capacitor is judged, the switch is switched according to the requirement, and the small capacitance measuring unit is used for retesting the specific capacitance once; if the capacitance is judged to belong to the large capacitance range, the large capacitance test unit is used for continuing the test; when the capacitor Cx to be detected is a small capacitor, the first switch SW1, the second switch SW2, the third switch SW5 and the sixth switch SW6 are all switched off, the fourth switch SW3, the fifth switch SW4 and the seventh switch SW7 are switched on, a sinusoidal signal output by a sinusoidal signal source in a chip is output to a black pen-type meter of a multimeter through the first operational amplifier OP1, the sinusoidal signal is added to one end of the capacitor Cx to be detected, the other end of the capacitor Cx to be detected is connected to a negative input port of the second operational amplifier OP2 through a red pen-type meter of the multimeter and is connected to an output end of the second operational amplifier OP2 through Rref, a circuit detected at the moment is a small capacitor measuring unit, and after an ADC tests the amplitude value of the sinusoidal signal output by the signal source VSIN and the voltage values at two ends of the first reference resistor Rref1, a formula is calculated to obtain the capacitance of the capacitor to be detected; when the capacitor Cx to be measured is a large capacitor, the fourth switch SW3, the fifth switch SW4 and the seventh switch SW7 are turned off, the third switch SW5 and the sixth switch SW6 are turned on, the current source I is connected to a red pen-shape meter through the first switch SW1 and the second switch SW2 to charge and discharge the capacitor Cx to be measured, the counter 30 is used for recording the time required by charge and discharge, and the circuit at the moment is a large capacitor measuring unit; finally, the chip of the embodiment can simultaneously ensure the capacitor to be tested in a small range and the capacitor to be tested in a large range, and the accurate and quick test can be realized.

Based on the same inventive concept, the embodiment of the present invention further provides a universal meter, including the capacitance measurement chip 100, the first reference resistance Rref1 and the second reference resistance Rref2, the first pin A0 of the capacitance measurement chip 100 is connected with one end of the first reference resistance Rref1, the second pin A1 of the capacitance measurement chip 100 is connected with one end of the second reference resistance Rref2, the analog ground pin AGND of the capacitance measurement chip 100 is connected with one end of the external capacitance to be measured through the black pen of the universal meter, and the other end of the capacitance to be measured is connected with the other end of the first reference resistance Rref1 and the other end of the second reference resistance Rref2 through the red pen of the universal meter.

Based on the same inventive concept, the embodiment of the present invention further provides a capacitance measuring circuit, including the capacitance measuring chip 100, the first reference resistance Rref1, the second reference resistance Rref2, the capacitance to be measured, the black pen-type meter and the red pen-type meter, the first pin A0 of the capacitance measuring chip 100 is connected with one end of the first reference resistance Rref1, the second pin A1 of the capacitance measuring chip 100 is connected with one end of the second reference resistance Rref2, the analog ground pin AGND of the capacitance measuring chip 100 is connected with one end of the capacitance to be measured through the black pen-type meter, and the other end of the capacitance to be measured is connected with the other end of the first reference resistance Rref1 and the other end of the second reference resistance Rref2 through the red pen-type meter respectively.

Although the present invention has been disclosed in the preferred embodiments, it is not intended to limit the present invention, and any person skilled in the art can use the above-mentioned method and technical contents to make possible changes and modifications to the technical solution of the present invention without departing from the spirit and scope of the present invention, and therefore, any simple modification, equivalent changes and modifications made to the above embodiments by the technical substance of the present invention all belong to the protection scope of the technical solution of the present invention.

Claims

1. A capacitance measurement chip, comprising: the device comprises a first pin A0, a second pin A1, an analog ground pin AGND, a small capacitance measuring unit and a large capacitance measuring unit, wherein the first pin is respectively connected with a first end of the small capacitance measuring unit and a first end of the large capacitance measuring unit, the second pin is respectively connected with a second end of the small capacitance measuring unit and a second end of the large capacitance measuring unit, and the analog ground pin is connected with a third end of the small capacitance measuring unit;

the first pin A0 is connected with one end of an external first reference resistor Rref1, the second pin A1 is connected with one end of an external second reference resistor Rref2, the analog ground pin AGND is connected with one end of an external capacitor to be tested through a black stylus, and the other end of the capacitor to be tested is respectively connected with the other end of the first reference resistor Rref1 and the other end of the second reference resistor Rref2 through a red stylus;

in the process of measuring the capacitor to be measured, the large capacitor measuring unit is adopted to detect the capacitor to be measured, and the capacitor to be measured is judged to be a large capacitor or a small capacitor; and when the capacitor to be detected is a small capacitor, the small capacitor measuring unit is adopted to detect the capacitance of the capacitor to be detected.

2. The capacitance measurement chip according to claim 1, wherein the large capacitance measurement unit includes a current source I, a first switch SW1, a second switch SW2, a third switch SW5, a first comparator, a second comparator, a first reference voltage VREF1, a second reference voltage VREF2, and a counter;

the current source I is respectively connected with a working voltage VDD and a grounding end GND, the current source I is connected with the first end of the large capacitance measuring unit through the first switch SW1 and used for charging the capacitor to be measured, and the current source I is connected with the first end of the large capacitance measuring unit through the second switch SW2 and used for discharging the capacitor to be measured; a second end of the large capacitance measuring unit is respectively connected with a first input end of the first comparator and a first input end of the second comparator through the third switch SW5, a second input end of the first comparator is connected with the first reference voltage VREF1, a second input end of the second comparator is connected with the second reference voltage VREF2, and an output end of the first comparator and an output end of the second comparator are respectively connected with the counter;

when the large-capacitance measuring unit is used for detecting the capacitance of the capacitor to be detected, the first switch SW1 is firstly closed, the second switch SW2 is opened, the third switch SW5 is closed, the current source I charges the capacitor to be detected, when the voltage value of the capacitor to be detected exceeds the voltage value of a first reference voltage VREF1 input by the second input end of the first comparator, the charging is completed, the first switch SW1 is opened, the second switch SW2 is closed, the third switch SW5 is closed, the current source I discharges the capacitor to be detected, and when the voltage value of the capacitor to be detected is lower than the voltage value of a second reference voltage VREF2 input by the second input end of the second comparator, the discharging is completed; the counter is used for calculating the time of one-time charge and discharge in a circulating mode.

3. The capacitance measuring chip according to claim 2, wherein a calculation formula when the large capacitance measuring unit is used to detect the capacitance of the capacitor to be measured is as follows: cx = T × I/(VREF 1 — VREF 2), where Cx denotes a capacitance of the capacitor to be measured, VREF1 denotes a voltage value of the first reference voltage VREF1, VREF2 denotes a voltage value of the second reference voltage VREF2, I denotes a current value output by the current source I, and T denotes a time of one charge and discharge cycle calculated by the counter.

4. The capacitance measuring chip according to claim 1, wherein the small capacitance measuring unit comprises a first operational amplifier OP1, a second operational amplifier OP2, a fourth switch SW3, a fifth switch SW4, a sixth switch SW6, a seventh switch SW7, a sinusoidal signal source VSIN, and an ADC module;

the first end of the small capacitance measuring unit is connected with the output end of the second operational amplifier OP2 through the fourth switch SW3, and the first end of the small capacitance measuring unit is connected with the first pin of the ADC module; a second end of the small capacitance measuring unit is connected with a second pin of the ADC module, a second end of the small capacitance measuring unit is connected with a reverse input end of a second operational amplifier OP2 through a fifth switch SW4, a third end of the small capacitance measuring unit is respectively connected with a third pin of the ADC module, a reverse input end of the first operational amplifier, and an output end of the first operational amplifier, a forward input end of the first operational amplifier is connected with a ground terminal through a sixth switch SW6, and the forward input end of the first operational amplifier is connected with the ground terminal through a seventh switch SW7 and the sinusoidal signal source VSIN in sequence;

when the large-capacitance measuring unit is used for detecting the capacitance of the capacitor to be detected, the sixth switch SW6 is closed, and the fourth switch SW3, the fifth switch SW4 and the seventh switch SW7 are opened; when adopting the small capacitance measuring unit is right when the electric capacity of awaiting measuring detects, sixth switch SW6 disconnection, fourth switch SW3 fifth switch SW4 seventh switch SW7 is closed, sinusoidal signal that sinusoidal signal source VSIN output passes through first operational amplifier OP1 black pen-shape metre reaches the one end of electric capacity of awaiting measuring, the other end output current of electric capacity of awaiting measuring passes through first reference resistance Rref1, the ADC module is used for right the voltage value at first reference resistance Rref1 both ends detects and detects the amplitude value of sinusoidal signal that sinusoidal signal source VSIN output.

5. The capacitance measuring chip according to claim 4, wherein the calculation formula when the large capacitance measuring unit is used to detect the capacitance of the capacitor to be measured is as follows: cx = VR/(VSIN Rref2 pi f), where Cx denotes a capacitance of the capacitor to be measured, VR denotes a voltage value across the first reference resistor Rref1, VSIN denotes an amplitude value of the sinusoidal signal output by the sinusoidal signal source VSIN, and f denotes a frequency value of the sinusoidal signal output by the sinusoidal signal source VSIN.

6. A multimeter comprising the capacitance measurement chip of any of claims 1-5.

7. A capacitance measuring circuit comprising the capacitance measuring chip according to any one of claims 1 to 5.