Resistance and capacitance measuring circuit and method

Abstract

The invention provides a resistor and capacitor measuring circuit and method, and relates to the technical field of resistor and capacitor measurement, and the resistor and capacitor measuring circuit comprises a switch S1, a switch S2, a switch S3, a switch S4, a switch S5, a switch S6, a reference capacitor CREF, a capacitor CTEST to be measured, a reference resistor RREF, a resistor RTEST to be measured, a Schmitt trigger u1, a time-to-digital converter TDC and a microprocessor muC. And the Schmitt trigger u1, the time-to-digital converter TDC and the microprocessor muC are sequentially connected in series. According to the resistor-capacitor measuring circuit and method, the discharge time of the reference resistor-capacitor and the discharge time of the resistor-capacitor to be measured are respectively measured through the time-to-digital converter, the time proportion is calculated, and the parameters of the resistor-capacitor to be measured and the resistor-capacitor to be measured are calculated and reversely deduced by combining the known reference capacitor and the resistor. The correction compensation amount is obtained through an additional measurement state, and then the measurement result is corrected, so that the influence of the conduction loss of the switch on the measurement result is greatly reduced.

Description

Technical Field

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

[0002] With the development of the electronics industry, the application of resistor and capacitor components has increased dramatically, and the scope of application has become wider and wider. Their parameters need to be tested in many applications.

[0003] At present, the main method for measuring resistance is the bridge method. The basic idea is to convert the resistance value into a voltage value or a frequency value. As long as the AD converter measures the voltage across the measured resistance and then performs corresponding operations, this measurement method has a simple structure, but is affected by the input voltage, conversion accuracy and output frequency range of the AD converter. This method has a small measurement range and low accuracy. When the voltage amplification factor is large, the offset voltage error caused by the imbalance of the bias current is large. At the same time, the amplification factor increases, which reduces the measurement range. Using a pure analog circuit method to measure resistance and capacitance can avoid the trouble of programming, but the circuit is complex, the flexibility is poor, and the measurement accuracy is low.

[0004] The existing solution does not take into account the on-state parasitic impedance of the switch. When the resistance to be measured is greater than the reference resistance, it will lead to a large deviation in the measurement calculation result, especially when the resistance value is small, the on-state parasitic impedance cannot be ignored. Summary of the invention

[0005] The invention aims to provide a resistance and capacitance measurement circuit and method. The discharge time of the reference resistance and capacitance and the discharge time of the resistance and capacitance to be measured are measured respectively by a time-to-digital converter, the time ratio is calculated, and then the parameter size of the resistance and capacitance to be measured is calculated and inverted in combination with the known reference capacitance and resistance, and the correction compensation amount is obtained through an additional measurement state, and then the measurement result is corrected, which greatly reduces the influence of the conduction loss of the switch on the measurement result.

[0006] In order to achieve the above-mentioned effect, the present invention provides the following technical solution: a resistance and capacitance measurement circuit, comprising a switch S1, a switch S2, a switch S3, a switch S4, a switch S5, a switch S6, a reference capacitor C REF 、Capacitor to be tested C TEST , reference resistance R REF 、Resistance to be measured R TEST, Schmitt trigger u1, time digital converter TDC and microprocessor μC, the Schmitt trigger u1, time digital converter TDC and microprocessor μC are connected in series in sequence, one end of the switch S1 is electrically connected to the input voltage VIN, and the other end of the switch S1 is electrically connected to the input end of the Schmitt trigger u1, one end of the switch S2, the switch S3, the switch S4, the switch S5 and the switch S6 are all electrically connected to the input end of the Schmitt trigger u1, and the other end of the switch S2 is electrically connected to the reference capacitor C REF One end of the reference capacitor C REF The other end of the switch S3 is connected to the capacitor C TEST One end of the capacitor to be measured is electrically connected to TEST The other end of the switch S4 is connected to the reference resistor R REF One end of the reference resistor R REF The other end of the switch S5 is connected to the resistance to be measured R TEST One end of the resistor to be measured is electrically connected to TEST The other end of the switch S6 is grounded.

[0007] A resistance and capacitance measurement method is provided, which uses a resistance and capacitance measurement circuit and comprises the following steps:

[0008] Step 1: Build a resistance and capacitance measurement circuit;

[0009] Step 2, setting the working state of the measurement circuit: adjusting the conduction path of the resistance and capacitance measurement circuit to obtain six working states of the measurement circuit, and setting the six working states of the measurement circuit;

[0010] Step 3, obtaining measurement data: using the six working states of the measurement circuit respectively, and obtaining corresponding data under the six working states of the measurement circuit;

[0011] Step 4: Calculate the capacitance C to be measured based on the corresponding data under the six working states of the measuring circuit. TEST And the resistance to be measured R TEST Perform the calculations and then complete the measurement.

[0012] Further, in step 2, the six measurement circuit working states are: a first measurement circuit working state, a second measurement circuit working state, a third measurement circuit working state, a fourth measurement circuit working state, a fifth measurement circuit working state and a sixth measurement circuit working state.

[0013] Furthermore, the working state of the first measurement circuit is:

[0014] Close switch S1 and switch S2;

[0015] Turn on switch S3, switch S4, switch S5 and switch S6;

[0016] The current output from the regulated voltage VIN terminal passes through switches S1 and S2 in turn, and then to the reference capacitor C REF to charge.

[0017] Furthermore, the working state of the second measurement circuit is:

[0018] Close switch S2 and switch S4;

[0019] Open switch S1, switch S3, switch S5 and switch S6;

[0020] Reference capacitor C REF The output current passes through switch S2, switch S4 and reference resistor R in sequence. REF , and then discharge to the ground.

[0021] Furthermore, the working state of the third measurement circuit is:

[0022] Close switch S2 and switch S5;

[0023] Open switch S1, switch S3, switch S4 and switch S6;

[0024] Reference capacitor C REF The output current passes through switch S2, switch S5 and the resistor to be measured R in turn. TEST , and then discharge to the ground.

[0025] Furthermore, the working state of the fourth measurement circuit is:

[0026] Close switch S1 and switch S3;

[0027] Open switch S2, switch S4, switch S5 and switch S6;

[0028] The current output from the stable voltage VIN terminal passes through switches S1 and S3 in turn, and then to the capacitor C to be tested. TEST to charge.

[0029] Furthermore, the working state of the fifth measurement circuit is:

[0030] Close switch S3 and switch S4;

[0031] Open switch S1, switch S2, switch S5 and switch S6;

[0032] Capacitor C to be tested TEST The output current passes through switch S3, switch S4 and reference resistor R in sequence. REF, and then discharge to the ground.

[0033] Furthermore, the working state of the sixth measurement circuit is:

[0034] Close switch S2 and switch S6;

[0035] Turn on switch S1, switch S3, switch S4 and switch S5;

[0036] Reference capacitor C REF The output current passes through switch S2 and switch S6 in sequence and then discharges to the ground.

[0037] Furthermore, the corresponding data obtained by the working state of the second measurement circuit is:

[0038] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 24 ;

[0039] The corresponding data obtained from the working state of the third measurement circuit is:

[0040] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 25 ;

[0041] The corresponding data obtained from the working state of the fifth measurement circuit is:

[0042] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 34 ;

[0043] The corresponding data obtained in the working state of the sixth measurement circuit is:

[0044] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 26 .

[0045] The present invention provides a resistance and capacitance measurement circuit and method, which have the following beneficial effects: the discharge time of a reference resistance and capacitance and the discharge time of a resistance and capacitance to be measured are respectively measured by a time-to-digital converter, the time ratio is calculated, and then the parameter sizes of the resistance and capacitance to be measured are calculated and inverted in combination with the known reference capacitance and resistance, a correction compensation amount is obtained through an additional measurement state, and then the measurement result is corrected, thereby greatly reducing the influence of the conduction loss of the switch on the measurement result. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A circuit diagram of a resistance and capacitance measurement circuit and method of the present invention;

[0047] Figure 2 A schematic diagram of the working state of a first measurement circuit of a resistance and capacitance measurement circuit and method of the present invention;

[0048] Figure 3 A schematic diagram of the working state of the second measurement circuit of a resistance and capacitance measurement circuit and method of the present invention;

[0049] Figure 4 A schematic diagram of the working state of a third measurement circuit of a resistance and capacitance measurement circuit and method of the present invention;

[0050] Figure 5 A schematic diagram of a fourth measurement circuit working state of a resistance and capacitance measurement circuit and method of the present invention;

[0051] Figure 6 A schematic diagram of a fifth measuring circuit working state of a resistance and capacitance measuring circuit and method of the present invention;

[0052] Figure 7 It is a schematic diagram of the working state of the sixth measurement circuit of a resistance and capacitance measurement circuit and method of the present invention;

[0053] Figure 8 A schematic diagram of a Schmitt trigger threshold value of a resistance and capacitance measurement circuit and method of the present invention;

[0054] Fig. 9 The present invention is a flow chart of a resistance and capacitance measurement circuit and method. DETAILED DESCRIPTION

[0055] See also Figure 1-9 The present invention provides a technical solution: a resistance and capacitance measurement circuit, including a switch S1, a switch S2, a switch S3, a switch S4, a switch S5, a switch S6, a reference capacitor C REF 、Capacitor to be tested C TEST , reference resistance R REF 、Resistance to be measured R TEST , Schmitt trigger u1, time digital converter TDC and microprocessor μC, Schmitt trigger u1, time digital converter TDC and microprocessor μC are connected in series in sequence, one end of switch S1 is electrically connected to input voltage VIN, and the other end of switch S1 is electrically connected to the input end of Schmitt trigger u1, one end of switch S2, switch S3, switch S4, switch S5 and switch S6 are all electrically connected to the input end of Schmitt trigger u1, and the other end of switch S2 is electrically connected to reference capacitor C REF One end is electrically connected to the reference capacitor C REF The other end of the switch S3 is connected to the capacitor C TEST One end of the capacitor to be tested is electrically connected to TEST The other end of switch S4 is connected to the reference resistor R REF One end is electrically connected to the reference resistor R REFThe other end of the switch S5 is connected to the resistance R TEST One end of the resistor to be measured is electrically connected to TEST The other end of the switch S6 is grounded, and the other end of the switch S6 is grounded.

[0056] A resistance and capacitance measurement method is provided, which uses a resistance and capacitance measurement circuit and comprises the following steps:

[0057] Step 1: Build a resistance and capacitance measurement circuit;

[0058] Step 2, setting the working state of the measurement circuit: adjusting the conduction path of the resistance and capacitance measurement circuit, obtaining six working states of the measurement circuit, and setting the six working states of the measurement circuit;

[0059] Step 3, obtaining measurement data: using six measurement circuit working states respectively, obtaining corresponding data under the six measurement circuit working states;

[0060] Step 4: Calculate the capacitance C to be measured based on the corresponding data under the six measurement circuit working conditions. TEST And the resistance to be measured R TEST Perform the calculations and then complete the measurement.

[0061] Specifically, in step 2, the six measurement circuit working states are: a first measurement circuit working state, a second measurement circuit working state, a third measurement circuit working state, a fourth measurement circuit working state, a fifth measurement circuit working state and a sixth measurement circuit working state.

[0062] Specifically, the working state of the first measurement circuit is:

[0063] Close switch S1 and switch S2;

[0064] Turn on switch S3, switch S4, switch S5 and switch S6;

[0065] The current output from the regulated voltage VIN terminal passes through switches S1 and S2 in turn, and then to the reference capacitor C REF to charge.

[0066] Specifically, the working state of the second measurement circuit is:

[0067] Close switch S2 and switch S4;

[0068] Open switch S1, switch S3, switch S5 and switch S6;

[0069] Reference capacitor C REF The output current passes through switch S2, switch S4 and reference resistor R in sequence. REF , and then discharge to the ground.

[0070] Specifically, the working state of the third measurement circuit is:

[0071] Close switch S2 and switch S5;

[0072] Open switch S1, switch S3, switch S4 and switch S6;

[0073] Reference capacitor C REF The output current passes through switch S2, switch S5 and the resistor to be measured R in turn. TEST , and then discharge to the ground.

[0074] Specifically, the working state of the fourth measurement circuit is:

[0075] Close switch S1 and switch S3;

[0076] Open switch S2, switch S4, switch S5 and switch S6;

[0077] The current output from the stable voltage VIN terminal passes through switches S1 and S3 in turn, and then to the capacitor C to be tested. TEST to charge.

[0078] Specifically, the working state of the fifth measurement circuit is:

[0079] Close switch S3 and switch S4;

[0080] Open switch S1, switch S2, switch S5 and switch S6;

[0081] Capacitor C to be tested TEST The output current passes through switch S3, switch S4 and reference resistor R in sequence. REF , and then discharge to the ground.

[0082] Specifically, the working state of the sixth measurement circuit is:

[0083] Close switch S2 and switch S6;

[0084] Turn on switch S1, switch S3, switch S4 and switch S5;

[0085] Reference capacitor C REF The output current passes through switch S2 and switch S6 in sequence and then discharges to the ground.

[0086] Specifically, the corresponding data obtained from the working state of the second measurement circuit is:

[0087] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 24 ;

[0088] The corresponding data obtained from the working state of the third measurement circuit is:

[0089] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 25 ;

[0090] The corresponding data obtained in the working state of the fifth measurement circuit is:

[0091] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 34 ;

[0092] The corresponding data obtained in the working state of the sixth measurement circuit is:

[0093] Record the time t from the start of discharge to the reversal of Schmitt trigger u1 26 .

[0094] A resistance and capacitance measurement circuit and method:

[0095] The circuit consists of three parts. The first part is the resistance and capacitance to be measured, the second part is the reference capacitance and resistance, and the third part is the Schmitt trigger and TDC time-to-digital converter. The principle is to obtain the different RC charge and discharge time ratios through TDC measurement, and then combine the known reference capacitance and resistance to infer the resistance and capacitance to be measured.

[0096] In the circuit, C REF Represents the reference capacitance; R REF Indicates reference resistance; C TEST Represents the capacitance to be measured; R TEST represents the resistance to be measured; u1 represents a Schmitt trigger; TDC represents a time-to-digital converter; μC represents a microprocessor that processes the result output by TDC.

[0097] Workflow:

[0098] The first measurement circuit working state: open S1, S2, close S3, S4, S5, S6. At this time, the current flows from VIN through S1, S2 to the capacitor C REF Charge until fully charged before proceeding to the subsequent state.

[0099] The second measurement circuit working state: open S2, S4, close S1, S3, S5, S6. At this time, the current flows from CREF through S2, S4, R REF The time from the start of discharge to the reversal of the Schmitt trigger is t 24 .

[0100] The third measurement circuit working state: open S2, S5, close S1, S3, S4, S6. At this time, the current flows from CREF through S2, S5, R TEST The time from the start of discharge to the reversal of the Schmitt trigger is t 25 .

[0101] The fourth measurement circuit working state: open S1, S3, close S2, S4, S5, S6. At this time, the current flows from VIN through S1, S3 to capacitor C TEST Charge until fully charged before proceeding to the subsequent state.

[0102] The fifth measurement circuit working state: open S3, S4, close S1, S2, S5, S6. At this time, the current flows from CTEST through S3, S4, R REF The time from the start of discharge to the reversal of the Schmitt trigger is t 34 .

[0103] The sixth measurement circuit working state: open S2, S6, close S1, S3, S4, S5. At this time, the current discharges from CREF through S2, S6 to the ground. The time from the start of discharge to the reversal of the Schmitt trigger is t 26 .

[0104] Status description:

[0105] 1. Run the "first measurement circuit working state" and let C REF The capacitor is fully charged.

[0106] 2. Run the "second measurement circuit working state" and get the time t 24 .

[0107] 3. Run the "first measurement circuit working state" and let C REF The capacitor is fully charged

[0108] 4. Run the "third measurement circuit working state" and get the time t 25 .

[0109] 5. Run the "fourth measurement circuit working state" and let C TEST The capacitor is fully charged.

[0110] 6. Run the "fifth measurement circuit working state" and get the time t 34 .

[0111] 7. Run the "first measurement circuit working state" and let C REF The capacitor is fully charged.

[0112] 8. Run the "sixth measurement circuit working state" and get the time t 26 .

[0113] The parasitic on-resistance of switches S1, S2, S3, and S4 is R S1 , R S2 , R S3 , R S4, the Schmitt trigger is ideal, and the upper threshold of the Schmitt trigger is V THH , the lower threshold is V THL .

[0114]

[0115] For capacitance measurements:

[0116]

[0117] For resistance measurements:

[0118]

[0119] The design makes S2, S3, S4, S5, and S6 equal in size and as closely matched as possible, with:

[0120] (R S2 +R S3 )-(R S3 +R S4 )≈0

[0121] (R S3 +R S4 )-(R S2 +R S5 )≈0

[0122] err≈0

[0123] Even if t 25 >>t 23 , that is, R TEST >>R REF It can also ensure that err is smaller.

[0124] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A resistance and capacitance measurement circuit, comprising a switch S1, a switch S2, a switch S3, a switch S4, a switch S5, a switch S6, a reference capacitor C REF 、Capacitor to be tested C TEST , reference resistance R REF 、Resistance to be measured R TEST , Schmitt trigger u1, time digital converter TDC and microprocessor μC, characterized in that, The Schmitt trigger u1, the time digital converter TDC and the microprocessor μC are connected in series in sequence, one end of the switch S1 is electrically connected to the input voltage VIN, and the other end of the switch S1 is electrically connected to the input end of the Schmitt trigger u1, one end of the switch S2, the switch S3, the switch S4, the switch S5 and the switch S6 are all electrically connected to the input end of the Schmitt trigger u1, and the other end of the switch S2 is electrically connected to the reference capacitor C REF One end of the reference capacitor C REF The other end of the switch S3 is connected to the capacitor C TEST One end of the capacitor to be measured is electrically connected to TEST The other end of the switch S4 is connected to the reference resistor R REF One end of the reference resistor R REF The other end of the switch S5 is connected to the resistance to be measured R TEST One end of the resistor to be measured is electrically connected to TEST The other end of the switch S6 is grounded.

2. A method for measuring resistance and capacitance, characterized in that: A resistance and capacitance measuring circuit as claimed in claim 1 is applied, comprising the following steps: S1. Build the resistance and capacitance measurement circuit as claimed in claim 1; S2, setting the working state of the measurement circuit: adjusting the conduction path of the resistance and capacitance measurement circuit to obtain six working states of the measurement circuit, and setting the six working states of the measurement circuit; S3, obtaining measurement data: using the six measurement circuit working states respectively to obtain corresponding data under the six measurement circuit working states; S4. Calculation: Based on the corresponding data of the six measuring circuit working states, the capacitance C to be measured TEST And the resistance to be measured R TEST Perform the calculations and then complete the measurement.

3. A resistance and capacitance measurement method according to claim 2, characterized in that: In step S2, the six measurement circuit working states are: a first measurement circuit working state, a second measurement circuit working state, a third measurement circuit working state, a fourth measurement circuit working state, a fifth measurement circuit working state and a sixth measurement circuit working state.

4. A resistance and capacitance measurement method according to claim 3, characterized in that: The working state of the first measurement circuit is: Close switch S1 and switch S2; Turn on switch S3, switch S4, switch S5 and switch S6; The current output from the regulated voltage VIN terminal passes through switches S1 and S2 in turn, and then to the reference capacitor C REF to charge.

5. A resistance and capacitance measurement method according to claim 3, characterized in that: The working state of the second measurement circuit is: Close switch S2 and switch S4; Open switch S1, switch S3, switch S5 and switch S6; Reference capacitor C REF The output current passes through switch S2, switch S4 and reference resistor R in sequence. REF , and then discharge to the ground.

6. A resistance and capacitance measurement method according to claim 3, characterized in that: The working state of the third measurement circuit is: Close switch S2 and switch S5; Open switch S1, switch S3, switch S4 and switch S6; Reference capacitor C REF The output current passes through switch S2, switch S5 and the resistor to be measured R in turn. TEST , and then discharge to the ground.

7. A resistance and capacitance measurement method according to claim 3, characterized in that: The working state of the fourth measurement circuit is: Close switch S1 and switch S3; Open switch S2, switch S4, switch S5 and switch S6; The current output from the stable voltage VIN terminal passes through switches S1 and S3 in turn, and then to the capacitor C to be tested. TEST to charge.

8. The method for measuring resistance and capacitance according to claim 3, characterized in that: The working state of the fifth measurement circuit is: Close switch S3 and switch S4; Open switch S1, switch S2, switch S5 and switch S6; Capacitor C to be tested TEST The output current passes through switch S3, switch S4 and reference resistor R in sequence. REF , and then discharge to the ground.

9. The method for measuring resistance and capacitance according to claim 3, characterized in that: The working state of the sixth measurement circuit is: Close switch S2 and switch S6; Turn on switch S1, switch S3, switch S4 and switch S5; Reference capacitor C REF The output current passes through switch S2 and switch S6 in sequence and then discharges to the ground.

10. The method for measuring resistance and capacitance according to claim 2, characterized in that: In step S3, the corresponding data obtained by the working state of the second measurement circuit is: Record the time t from the start of discharge to the reversal of Schmitt trigger u1 24 ; The corresponding data obtained from the working state of the third measurement circuit is: Record the time t from the start of discharge to the reversal of Schmitt trigger u1 25 ; The corresponding data obtained from the working state of the fifth measurement circuit is: Record the time t from the start of discharge to the reversal of Schmitt trigger u1 34 ; The corresponding data obtained in the working state of the sixth measurement circuit is: Record the time t from the start of discharge to the reversal of Schmitt trigger u1 26 .

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