CN211209675U - Differential amplifying circuit for measuring internal resistance - Google Patents
Differential amplifying circuit for measuring internal resistance Download PDFInfo
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- CN211209675U CN211209675U CN202020014675.2U CN202020014675U CN211209675U CN 211209675 U CN211209675 U CN 211209675U CN 202020014675 U CN202020014675 U CN 202020014675U CN 211209675 U CN211209675 U CN 211209675U
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Abstract
The utility model relates to an internal resistance is differential amplifier circuit for measurement, include first time constant filtering link, second time constant filtering link, differential amplifier and be used for connecting positive terminal, the negative terminal of the positive negative pole of the battery that awaits measuring. The first time constant filtering link comprises at least one stage of filtering unit, and the filtering unit comprises a resistor and a capacitor which are sequentially connected in series between a positive terminal and a negative terminal. The second time constant filtering link comprises a third resistor and a third capacitor which are sequentially connected in series between the positive terminal and the ground wire, and a line between the third resistor and the third capacitor is connected with the negative electrode of the differential amplifier. The filtering unit is a long-time constant RC filtering link, the differential amplifying circuit for measuring the internal resistance is provided with at least one stage of long-time constant RC filtering link and a short-time constant RC link, and the differential amplifier is matched to use proper parameters to obtain an ideal, simple and cheap internal resistance measuring signal processing circuit.
Description
Technical Field
The utility model relates to a battery internal resistance measurement field, more specifically say, relate to an internal resistance measurement is with differential amplifier circuit.
Background
In the measurement of the internal resistance of the secondary battery, the injected current or the discharged current generates a positive or negative voltage drop on the internal resistance, and in order to obtain the highest measurement resolution, a differential circuit is used in a general internal resistance measurement scheme to process a battery terminal voltage signal.
In the scheme, the effective voltage range of the battery is wider, so that the measuring range of the internal resistance is forced to be narrowed, or only a larger internal resistance can be measured, or the injection current or the discharge current needs to be increased greatly, and the two contradictions of the measuring range and the measuring resolution of the internal resistance are difficult to be considered.
In some schemes, the battery voltage before the measurement current is input is kept, an analog circuit, an electronic switch or a digital circuit is used for carrying out difference with the battery voltage after the measurement current is input, the voltage drop on the internal resistance is remained, and the difference amplification is carried out, so that a wider internal resistance measurement range can be obtained, the measurement resolution can be better considered, but the circuit is relatively complex, the debugging is difficult, the cost is higher, and the anti-interference capability is lower.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model lies in that, a differential amplification circuit for internal resistance measurement is provided.
The utility model provides a technical scheme that its technical problem adopted is: constructing a differential amplification circuit for measuring internal resistance, which comprises a first time constant filtering link, a second time constant filtering link, a differential amplifier, a positive terminal and a negative terminal, wherein the positive terminal and the negative terminal are used for connecting the positive electrode and the negative electrode of a battery to be measured;
the first time constant filtering link comprises at least one stage of filtering unit, and the filtering unit comprises a resistor and a capacitor which are sequentially connected in series between a positive terminal and a negative terminal;
a circuit between the capacitor and the resistor is connected with the anode of the differential amplifier, and one end of the capacitor connected with the cathode terminal is also grounded;
the second time constant filtering link comprises a third resistor and a third capacitor which are sequentially connected in series between the positive terminal and the ground wire, and a line between the third resistor and the third capacitor is connected with the negative electrode of the differential amplifier;
the sum of the resistance values from the resistor to the anode of the differential amplifier is equal to the sum of the resistance values from the third resistor to the cathode of the differential amplifier;
and a fourth resistor is arranged between the anode of the differential amplifier and the ground wire, a fifth resistor is connected between the cathode of the differential amplifier and the output end of the differential amplifier, and the resistance value of the fourth resistor is equal to that of the fifth resistor.
Preferably, the first time constant filtering link includes a first filtering unit and a second filtering unit, and the first filtering unit includes a first resistor and a first capacitor sequentially connected in series between a positive terminal and a negative terminal; the second filtering unit comprises a second resistor and a second capacitor which are connected in series, the second resistor is connected with a line between the first resistor and the first capacitor, and the second capacitor is connected with a line between the first capacitor and the negative terminal;
a line between the second resistor and the second capacitor is connected with the anode of the differential amplifier, and one end of the second capacitor, which is connected with the cathode terminal, is also grounded;
the sum of the resistance values from the first resistor, the second resistor to the anode of the differential amplifier is equal to the sum of the resistance values from the third resistor to the cathode of the differential amplifier.
Preferably, a sixth resistor is further disposed between a line between the second resistor and the second capacitor and the anode of the differential amplifier, a seventh resistor is further disposed between a line between the third resistor and the third capacitor and the cathode of the differential amplifier, and a sum of resistance values between the first resistor, the second resistor, the sixth resistor and the anode of the differential amplifier is equal to a sum of resistance values between the third resistor and the cathode of the differential amplifier and a sum of resistance values between the seventh resistor and the cathode of the differential amplifier.
Preferably, the capacitance values of the first capacitor and the second capacitor are equal, and the capacitance value of the third capacitor is smaller than the capacitance values of the first capacitor and the second capacitor.
Preferably, the output of the differential amplifier is connected to the ADC input.
Preferably, the time constant of the first filtering unit is greater than twenty milliseconds, and the time constant of the second filtering unit is in the order of sub-milliseconds.
Preferably, the capacitor further comprises an anti-jamming circuit connected between the negative terminal and the first and second capacitors.
Preferably, the immunity circuit includes an inductance.
Implement the utility model discloses an internal resistance is differential amplifier circuit for measurement has following beneficial effect: the differential amplifying circuit for measuring the internal resistance can be provided with at least one stage of large time constant RC filtering link and a short time constant RC link, and an appropriate parameter is used in cooperation with a differential amplifier to obtain a relatively ideal internal resistance measuring signal processing circuit by a relatively simple and low-cost circuit.
Drawings
The invention will be further explained with reference to the drawings and examples, wherein:
fig. 1 is a schematic circuit diagram of a differential amplifier circuit for internal resistance measurement according to an embodiment of the present invention.
Detailed Description
In order to clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, the differential amplifier circuit for measuring internal resistance in a preferred embodiment of the present invention includes a first time constant filtering link 1, a second time constant filtering link 2, a differential amplifier 3, and a positive terminal 4 and a negative terminal 5 for connecting the positive and negative electrodes of the battery to be measured, and can be used for measuring the voltage drop generated by the internal resistance of the discharging current mode.
The first time constant filtering link 1 is a two-stage filtering unit, and comprises a first filtering unit 11 and a second filtering unit 12, wherein the first filtering unit 11 comprises a first resistor R1 and a first capacitor C1 which are sequentially connected in series between a positive terminal 4 and a negative terminal 5; the second filtering unit 12 includes a second resistor R2 and a second capacitor C2 connected in series, wherein the second resistor R2 is connected to a line between the first resistor R1 and the first capacitor C1, and the second capacitor C2 is connected to a line between the negative terminals 5 of the first capacitor C1.
A line between the second resistor R2 and the second capacitor C2 is connected to the positive electrode of the differential amplifier 3, and one end of the second capacitor C2 connected to the negative electrode terminal 5 is also grounded.
The second time constant filtering link 2 comprises a third resistor R3 and a third capacitor C3 which are sequentially connected in series between the positive terminal 4 and the ground wire, and a line between the third resistor R3 and the third capacitor C3 is connected with the negative electrode of the differential amplifier 3.
The sum of the resistances between the first resistor R1, the second resistor R2 and the positive electrode of the differential amplifier 3 is equal to the sum of the resistances between the third resistor R3 and the negative electrode of the differential amplifier 3.
A fourth resistor R4 is arranged between the positive pole of the differential amplifier 3 and the ground, a fifth resistor R5 is connected between the negative pole of the differential amplifier 3 and the output end of the differential amplifier 3, and the resistance value of the fourth resistor R4 is equal to the resistance value of the fifth resistor R5.
The first filtering unit 11 is a long time constant filtering section, and the time constant is set to be more than twenty milliseconds for battery terminal voltage maintenance. The second filtering unit 12 is a short time constant filtering unit, and the time constant is set to be in the order of sub-milliseconds, such as tens of microseconds, and is used for resisting disturbance.
In other embodiments, the number of the filter units may also be one or more than two, and when one filter unit is used, the filter unit includes a resistor and a capacitor sequentially connected in series between the positive terminal 4 and the negative terminal 5; the line between the capacitor and the resistor is connected with the anode of the differential amplifier 3, and one end of the capacitor connected with the cathode terminal 5 is also grounded. In addition, the sum of the resistances between the resistance of the filter unit and the anode of the differential amplifier 3 is equal to the sum of the resistances between the third resistance R3 and the cathode of the differential amplifier). When the filtering units are a plurality of filtering units, the filtering units are sequentially arranged according to the connection mode of the first filtering unit and the second filtering unit.
The differential amplifying circuit for measuring the internal resistance is provided with at least one stage of long-time constant RC filtering link and a short-time constant RC link, and is matched with the differential amplifier 3 to use proper parameters to obtain a relatively ideal internal resistance measuring signal processing circuit by a relatively simple and cheap circuit.
A sixth resistor R6 is further provided between the line between the second resistor R2 and the second capacitor C2 and the anode of the differential amplifier 3, and a seventh resistor R7 is further provided between the line between the third resistor R3 and the third capacitor C3 and the cathode of the differential amplifier 3. The sum of the resistances between the first resistor R1, the second resistor R2, and the sixth resistor R6 to the positive electrode of the differential amplifier 3 is equal to the sum of the resistances between the third resistor R3, the seventh resistor R7 to the negative electrode of the differential amplifier 3.
By setting a proper proportion, a satisfactory internal resistance measurement range and measurement resolution can be obtained, and the sixth resistor R6 can be short-circuited and not used when parameters are proper.
Preferably, the capacitance values of the first capacitor C1 and the second capacitor C2 are equal, and the capacitance value of the third capacitor C3 is smaller than the capacitance values of the first capacitor C1 and the second capacitor C2. Further, the output end of the differential amplifier 3 is connected with the audio ADC chip.
In some embodiments, the differential amplifying circuit for measuring internal resistance further includes a tamper-resistant circuit 6 connected between the negative terminal 5 and the first and second capacitors C1 and C2, and the tamper-resistant circuit 6 includes an inductor.
In some embodiments, assume that the parameters:
third resistor R3(110R) + seventh resistor R7(100K) ═ 100.11K;
the first resistor R1(47.5K) + the second resistor R2(47.5K) + the sixth resistor R6(5.11K) ═ 100.11K;
the first capacitor C1 ═ the second capacitor C2 ═ 10 uF;
third capacitance C3 ═ 0.1 uF;
the fourth resistor R4 is the fifth resistor R5 is 3M.
The voltage between the positive terminal 4 and the negative terminal 5 of the battery end can be 1.2V-4.5V (the voltage of an element is withstand voltage, the voltage of an operational amplifier power supply is determined, the parameters of the element are modified, the input range of the battery end voltage of 1.0V-20V or even larger can be covered, and the device is widely suitable for single-core batteries of nickel-cadmium/nickel-hydrogen, lead-acid, lithium titanate, lithium iron phosphate, ternary lithium and the like and internal resistance measuring circuits of various battery packs of lead, lithium and nickel systems); the discharge current 1A, 100 milliohms internal resistance produced 0.1V voltage drop.
Before the internal resistance measurement is started, the voltage between the positive terminal 4 and the negative terminal 5 of the battery end passes through a two-stage filtering link with a time constant of about 332mS (0.7RC), and internal resistance discharge is input into a sixth resistor R6 and a fourth resistor R4/operational amplifier, so that the battery end voltage can be kept unchanged in enough time.
And (3) calculating: assuming that a voltage drop ripple of 100mV occurs, a ripple current of 0.1V/47.5KR. ═ 2.1uA is generated on the first resistor R1, and this current generates a fluctuation of 0.475mV at most every millisecond on the first capacitor C1, and after the same calculation, only a fluctuation of about 0.226uV is left on the second capacitor C2 every millisecond, and if the software can ensure that the measurement is completed within one millisecond (which is easy to do), we can consider that the second capacitor C2 maintains the terminal voltage of the battery.
The time constants of the third resistor R3 and the third capacitor C3 are only about 7.7uS, most interference signals can be filtered, the software controls the audio ADC chip to sample and convert time delay and measure current such as 50uS, the difference input of the operational amplifier at the moment is basically considered to be voltage drop generated by internal resistance of 100mV, the voltage is amplified by about 30 times, the output of the operational amplifier is about 2.997V, and the voltage is sent to the audio ADC chip, so that internal resistance measurement amplified signals with good resolution can be obtained.
When the sixth resistor R6, the seventh resistor R7 and related resistor parameters are modified, the polarity of the operational amplifier is changed in a right-side cross mode, and the circuit can be used for measuring reverse voltage drop generated by the internal resistance in the current injection mode.
The beneficial effect of this product:
the circuit of the invention has simple structure, and the long-time constant filter circuit cascade composed of low-value resistance-capacitance elements replaces a complex sample-hold circuit and gives good consideration to the anti-interference performance of the circuit.
The differential amplification output meets the requirements of measurement resolution and measurement range well.
The method is suitable for measuring the internal resistance of the secondary battery with various voltage grades and materials.
The circuit is simple and stable, has high tolerance to element errors, high response speed, low cost and excellent anti-interference performance.
The invention is characterized in that:
a cascaded long-time constant RC filter circuit is adopted to replace a complex sample-hold circuit in combination with software.
And a short time constant RC link is adopted and matched with an inductor, so that good anti-interference performance is realized.
It is to be understood that the above-described respective technical features may be used in any combination without limitation.
The above only is the embodiment of the present invention, not limiting the patent scope of the present invention, all the equivalent structures or equivalent processes that are used in the specification and the attached drawings or directly or indirectly applied to other related technical fields are included in the patent protection scope of the present invention.
Claims (8)
1. A differential amplification circuit for measuring internal resistance is characterized by comprising a first time constant filtering link (1), a second time constant filtering link (2), a differential amplifier (3), a positive terminal (4) and a negative terminal (5), wherein the positive terminal and the negative terminal are used for connecting the positive electrode and the negative electrode of a battery to be measured;
the first time constant filtering link (1) comprises at least one stage of filtering unit, and the filtering unit comprises a resistor and a capacitor which are sequentially connected in series between a positive terminal (4) and a negative terminal (5);
a line between the capacitor and the resistor is connected with the anode of the differential amplifier (3), and one end of the capacitor connected with the cathode terminal (5) is also grounded;
the second time constant filtering link (2) comprises a third resistor (R3) and a third capacitor (C3) which are sequentially connected in series between a positive terminal (4) and a ground wire, and a line between the third resistor (R3) and the third capacitor (C3) is connected with the negative electrode of the differential amplifier (3);
the sum of the resistances between the resistor and the anode of the differential amplifier (3) is equal to the sum of the resistances between the third resistor (R3) and the cathode of the differential amplifier (3);
a fourth resistor (R4) is arranged between the positive electrode of the differential amplifier (3) and the ground wire, a fifth resistor (R5) is connected between the negative electrode of the differential amplifier (3) and the output end of the differential amplifier (3), and the resistance value of the fourth resistor (R4) is equal to that of the fifth resistor (R5).
2. The differential amplifier circuit for measuring internal resistance according to claim 1, wherein the first time constant filter element (1) comprises a first filter unit (11) and a second filter unit (12), the first filter unit (11) comprises a first resistor (R1) and a first capacitor (C1) which are connected in series between a positive terminal (4) and a negative terminal (5); the second filtering unit (12) comprises a second resistor (R2) and a second capacitor (C2) which are connected in series, the second resistor (R2) is connected with a line between the first resistor (R1) and the first capacitor (C1), and the second capacitor (C2) is connected with a line between the first capacitor (C1) and the negative terminal (5);
a line between the second resistor (R2) and a second capacitor (C2) is connected with the anode of the differential amplifier (3), and one end of the second capacitor (C2) connected with the cathode terminal (5) is also grounded;
the sum of the resistances between the first resistor (R1), the second resistor (R2) and the anode of the differential amplifier (3) is equal to the sum of the resistances between the third resistor (R3) and the cathode of the differential amplifier (3).
3. The differential amplifier circuit for measuring internal resistance according to claim 2, wherein a sixth resistor (R6) is further provided between a line between the second resistor (R2) and the second capacitor (C2) and the positive electrode of the differential amplifier (3), a seventh resistor (R7) is further provided between a line between the third resistor (R3) and the third capacitor (C3) and the negative electrode of the differential amplifier (3), and the sum of the resistances between the first resistor (R1), the second resistor (R2), the sixth resistor (R6) and the positive electrode of the differential amplifier (3) is equal to the sum of the resistances between the third resistor (R3) and the seventh resistor (R7) and the negative electrode of the differential amplifier (3).
4. The differential amplifier circuit for measuring internal resistance according to claim 2, wherein the capacitance values of the first capacitor (C1) and the second capacitor (C2) are equal, and the capacitance value of the third capacitor (C3) is smaller than the capacitance values of the first capacitor (C1) and the second capacitor (C2).
5. The differential amplification circuit for internal resistance measurement according to any one of claims 1 to 4, wherein an output terminal of the differential amplifier (3) is connected to an ADC input.
6. The differential amplifier circuit for measuring internal resistance according to any one of claims 2 to 4, wherein the time constant of the first filter unit (11) is greater than twenty milliseconds, and the time constant of the second filter unit (12) is in the order of sub-milliseconds.
7. The differential amplifier circuit for measuring internal resistance according to any one of claims 2 to 4, further comprising an interference rejection circuit (6) connected between the negative terminal (5) and the first and second capacitors (C1, C2).
8. The differential amplifier circuit for measuring internal resistance according to claim 7, wherein the interference rejection circuit (6) includes an inductor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020014675.2U CN211209675U (en) | 2020-01-03 | 2020-01-03 | Differential amplifying circuit for measuring internal resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020014675.2U CN211209675U (en) | 2020-01-03 | 2020-01-03 | Differential amplifying circuit for measuring internal resistance |
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| Publication Number | Publication Date |
|---|---|
| CN211209675U true CN211209675U (en) | 2020-08-07 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202020014675.2U Active CN211209675U (en) | 2020-01-03 | 2020-01-03 | Differential amplifying circuit for measuring internal resistance |
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| CN (1) | CN211209675U (en) |
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- 2020-01-03 CN CN202020014675.2U patent/CN211209675U/en active Active
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