Circuit for realizing high-precision weak current acquisition by using low-precision ADC (Analog to Digital Converter)

Abstract

The utility model discloses a circuit for realizing high-precision weak current acquisition by using a low-precision ADC (Analog to Digital Converter), which comprises a signal amplification module for amplifying an input weak current signal, and the signal amplification module comprises the following steps: the circuit firstly performs primary amplification on a pA-level weak current signal by using a high-input-impedance cross-group amplifier, and then performs secondary amplification on the pA-level weak current signal by using a high-input-impedance cross-group amplifier; a current signal is amplified to a 10uV-10mV level by selecting a proper amplification resistor R1, balancing noise and a signal amplification factor, so that an ADC (Analog to Digital Converter) of a single-chip microcomputer can effectively acquire the signal, then the amplified signal is transmitted to an alternating-current in-phase amplifier through an alternating-current coupling capacitor C3, the amplification of about 100 times is realized by adjusting a feedback resistor and a gain resistor, and the current signal is amplified to the level of 10uV-10mV. The voltage of 10 uV is further amplified to 1 mV, so that the low-precision ADC can effectively collect weak signals, and the measurement precision is improved.

Description

Technical Field

[0001] This invention belongs to the field of weak signal detection technology, specifically relating to a circuit that uses a low-precision ADC to achieve high-precision weak current acquisition. Background Technology

[0002] With the continuous development of technology, the acquisition of weak current signals is being used more and more widely in various fields, such as biomedical signal detection, environmental monitoring, and energy management. In the process of acquiring weak current signals, high-precision analog-to-digital converters (ADCs) play a crucial role. Currently, although many high-precision ADCs are available on the market, capable of providing 16-bit high-precision measurements, these ADCs often come with problems such as high cost, complex system design, and difficulty in driver development.

[0003] While high-precision ADCs offer significant advantages in acquiring weak current signals, they also present several challenges: First, their high cost makes them unaffordable for many cost-sensitive applications; second, complex system design increases development difficulty and prolongs the research and development cycle; and finally, complex driver development requires specialized technical personnel for configuration and debugging, further increasing project costs. Therefore, reducing system cost and design complexity while maintaining the accuracy of weak current signal acquisition has become a pressing issue. Utility Model Content

[0004] The technical problem to be solved by this utility model is to overcome the existing defects and provide a circuit that uses a low-precision ADC to achieve high-precision weak current acquisition, so as to solve the problems mentioned in the background art, such as high cost, complex system design, high development difficulty, and the need for professional technicians for configuration and debugging.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a circuit for high-precision weak current acquisition using a low-precision ADC, comprising:

[0006] Signal amplification module: used to amplify the weak input current signal, the signal amplification module includes:

[0007] Cross-group amplifier: with high input impedance, used to amplify weak current signals in the pA level to the uA level, wherein the cross-group amplifier includes an amplification resistor R1 for setting the amplification factor;

[0008] AC in-phase amplifier: used to amplify the amplified AC signal, wherein the AC in-phase amplifier includes a feedback resistor R5 and a gain resistor R6, used to set the amplification factor to 100 times;

[0009] Voltage acquisition module: used to divide the amplified signal into DC and AC components, and send them to the microcontroller's AD channel 1 and AD channel 2 respectively. The DC component signal is output by a cross-group amplifier, and the AC component signal is output by an AC in-phase amplifier.

[0010] Data processing module: This module processes the DC and AC signals acquired by the microcontroller to obtain high-precision current signal values. The data processing module includes a microcontroller with a 12-bit ADC, which samples the two data streams and calculates them according to a preset algorithm formula to obtain high-precision current signal values.

[0011] Preferably, the signal amplification module further includes:

[0012] Capacitor C1: Connected to the input terminal of the cross-group amplifier to prevent amplifier oscillation;

[0013] Capacitor C2: Connected to the power supply terminal for power supply filtering;

[0014] Capacitor C3: Connected between the cross-group amplifier and the AC non-inverting amplifier for AC coupling.

[0015] Preferably, the microcontroller is a 32-bit general-purpose microcontroller with a built-in 12-bit ADC.

[0016] Preferably, the algorithm formula is as follows:

[0017]

[0018] Among them, I pd The current signal value, V dc V is a DC voltage. ac For alternating current voltage, V bais R is the DC bias voltage. f R is the feedback resistor for the cross-group amplifier. g This is the gain resistor for an AC in-phase amplifier.

[0019] Preferably, the signal amplification module further includes a photodiode PD1 for converting the optical signal into a current signal. The photodiode PD1 has a dark current at the pA level, and the current increases to the uA level when illuminated by light.

[0020] Preferably, the circuit further includes a resistor R4 connected to the input terminal of the AC in-phase amplifier to provide a DC bias voltage to improve the sampling accuracy of the ADC.

[0021] Preferably, the circuit further includes a resistor R5 connected to the output terminal of the AC non-inverting amplifier, used to set the gain of the AC non-inverting amplifier.

[0022] Preferably, the circuit further includes a resistor R6 connected to the feedback loop of the AC non-inverting amplifier, used to set the feedback coefficient of the AC non-inverting amplifier.

[0023] Compared with the prior art, this utility model provides a circuit for achieving high-precision weak current acquisition using a low-precision ADC, which has the following beneficial effects:

[0024] 1. This utility model amplifies weak current signals by setting up a cross-group amplifier and an AC in-phase amplifier: The circuit first uses a cross-group amplifier with high input impedance to perform primary amplification of the weak current signal at the pA level. By selecting an appropriate amplification resistor R1, the noise and signal amplification factor are balanced, and the current signal is amplified to the 10uV~10mV level, so that the ADC built into the microcontroller can effectively acquire the signal. Subsequently, the amplified signal is transmitted to the AC in-phase amplifier through the AC coupling capacitor C3. By adjusting the feedback resistor and the gain resistor, an amplification of about 100 times is achieved, further amplifying the 10uV voltage to 1mV, so that the low-precision ADC can effectively acquire the weak signal, thereby improving the measurement accuracy and effectively avoiding problems such as high cost, complex system design, high development difficulty, and the need for professional technicians for configuration and debugging.

[0025] 2. This utility model improves the accuracy of a low-precision ADC by setting an algorithm: The circuit uses the 12-bit ADC built into the microcontroller to sample the amplified DC and AC signals and processes them with an algorithm. First, the voltage of the DC and AC components is measured, and the AC signal is amplified by 100 times through an AC coupling amplifier. Since the amplification factor is 100, it is equivalent to improving the accuracy by log2(100)≈6.64 bits. Therefore, the accuracy of the 12-bit ADC is equivalent to the accuracy of 18 bits after processing. Without significantly increasing the cost, it achieves the effect of a near-high-precision ADC and reduces the overall cost of the system. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0027] Figure 1 This is a circuit diagram of the present invention. Detailed Implementation

[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0029] Please see Figure 1 This utility model provides a technical solution: a circuit for achieving high-precision weak current acquisition using a low-precision ADC, comprising:

[0030] Signal amplification module: Used to amplify weak input current signals. The signal amplification module includes:

[0031] Cross-group amplifier: It has high input impedance and is used to amplify weak current signals in the pA level to the uA level. The cross-group amplifier includes an amplification resistor R1 to set the amplification factor.

[0032] AC in-phase amplifier: used to amplify the amplified AC signal. The AC in-phase amplifier includes a feedback resistor R5 and a gain resistor R6, which are used to set the amplification factor to 100 times.

[0033] Voltage acquisition module: used to divide the amplified signal into DC and AC components, and send them to the microcontroller's AD channel 1 and AD channel 2 respectively. The DC component signal is output by the cross-group amplifier, and the AC component signal is output by the AC in-phase amplifier.

[0034] The data processing module processes the DC and AC signals acquired by the microcontroller to obtain high-precision current signal values. This module includes a microcontroller with a 12-bit ADC for sampling the two data streams and calculating the current signal values ​​according to a preset algorithm. Amplification of the weak current signal is achieved by using a cross-group amplifier and an AC in-phase amplifier. The circuit first uses a high-input-impedance cross-group amplifier to perform primary amplification of the pA-level weak current signal. By selecting an appropriate amplification resistor R1, the circuit achieves balanced amplification. The noise and signal amplification factor is increased to amplify the current signal to the 10uV~10mV level, enabling the microcontroller's built-in ADC to effectively acquire the signal. Subsequently, the amplified signal is transmitted to the AC non-inverting amplifier through the AC coupling capacitor C3. By adjusting the feedback resistor and gain resistor, an amplification of approximately 100 times is achieved, further amplifying the 10uV voltage to 1mV. This allows the low-precision ADC to effectively acquire weak signals, thereby improving measurement accuracy and effectively avoiding problems such as high cost, complex system design, high development difficulty, and the need for professional technicians for configuration and debugging.

[0035] In this invention, preferably, the signal amplification module further includes:

[0036] Capacitor C1: Connected to the input terminal of the cross-group amplifier to prevent amplifier oscillation;

[0037] Capacitor C2: Connected to the power supply terminal for power supply filtering;

[0038] Capacitor C3: Connected between the cross-group amplifier and the AC non-inverting amplifier for AC coupling.

[0039] In this invention, preferably, the microcontroller is a 32-bit general-purpose microcontroller with a built-in 12-bit ADC.

[0040] In this invention, the preferred algorithm formula is as follows:

[0041]

[0042] Among them, I pd The current signal value, V dc V is a DC voltage. ac For alternating current voltage, V bais R is the DC bias voltage. f R is the feedback resistor for the cross-group amplifier. g To improve the accuracy of a low-precision ADC by using an algorithm to enhance the gain resistor of an AC in-phase amplifier: The circuit uses the microcontroller's built-in 12-bit ADC to sample the amplified DC and AC signals and processes them using an algorithm. First, the voltage of the DC and AC components is measured, and the AC signal is amplified by 100 times through an AC coupling amplifier. Since the amplification factor is 100, it is equivalent to improving the accuracy by log2(100)≈6.64 bits. Therefore, the accuracy of the 12-bit ADC is equivalent to that of 18 bits after processing. This achieves the effect of a near-high-precision ADC without significantly increasing the cost, thus reducing the overall system cost.

[0043] In this invention, preferably, the signal amplification module further includes a photodiode PD1, which is used to convert the optical signal into a current signal. The photodiode PD1 has a dark current at the pA level, and when there is light, the current will increase to the uA level.

[0044] In this invention, preferably, the circuit further includes a resistor R4 connected to the input terminal of the AC in-phase amplifier to provide a DC bias voltage to improve the sampling accuracy of the ADC.

[0045] In this invention, preferably, the circuit further includes a resistor R5 connected to the output terminal of the AC non-inverting amplifier, used to set the gain of the AC non-inverting amplifier.

[0046] In this invention, preferably, the circuit further includes a resistor R6 connected to the feedback loop of the AC non-inverting amplifier, used to set the feedback coefficient of the AC non-inverting amplifier.

[0047] The working principle and usage process of this utility model are as follows: First, a weak current signal at the pA level is amplified using a high-input-impedance multi-group amplifier. By selecting a suitable amplification resistor R1, noise and signal amplification are balanced, amplifying the current signal to the uA level, making it effectively acquireable by the microcontroller's 12-bit ADC. Subsequently, the amplified signal is divided into DC and AC components, which are sent to the microcontroller's AD channel 1 and AD channel 2 for sampling, respectively. The microcontroller, according to a preset algorithm formula, processes the acquired DC voltage value V... dc and AC voltage value V ac The circuit is processed to obtain a high-precision current signal value I. The circuit structure is simple and inexpensive. Through algorithmic processing, high-precision current measurement can be achieved, making it suitable for various weak current signal acquisition applications and possessing broad application prospects.

[0048] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A circuit for achieving high-precision weak current acquisition using a low-precision ADC, characterized in that: include: Signal amplification module: used to amplify the weak input current signal, the signal amplification module includes: Cross-group amplifier: with high input impedance, used to amplify weak current signals in the pA level to the uA level, wherein the cross-group amplifier includes an amplification resistor R1 for setting the amplification factor; AC in-phase amplifier: used to amplify the amplified AC signal, wherein the AC in-phase amplifier includes a feedback resistor R5 and a gain resistor R6, used to set the amplification factor to 100 times; Voltage acquisition module: used to divide the amplified signal into DC and AC components, and send them to the microcontroller's AD channel 1 and AD channel 2 respectively. The DC component signal is output by a cross-group amplifier, and the AC component signal is output by an AC in-phase amplifier. Data processing module: This module processes the DC and AC signals acquired by the microcontroller to obtain high-precision current signal values. The data processing module includes a microcontroller with a 12-bit ADC, which samples the two data streams and calculates them according to a preset algorithm formula to obtain high-precision current signal values.

2. The circuit for high-precision weak current acquisition using a low-precision ADC according to claim 1, characterized in that: The signal amplification module further includes: Capacitor C1: Connected to the input terminal of the cross-group amplifier to prevent amplifier oscillation; Capacitor C2: Connected to the power supply terminal for power supply filtering; Capacitor C3: Connected between the cross-group amplifier and the AC non-inverting amplifier for AC coupling.

3. The circuit for high-precision weak current acquisition using a low-precision ADC according to claim 1, characterized in that: The microcontroller is a 32-bit general-purpose microcontroller with a built-in 12-bit ADC.

4. The circuit for high-precision weak current acquisition using a low-precision ADC according to claim 1, characterized in that: The algorithm formula is as follows: Among them, I pd The current signal value, V dc V is a DC voltage. ac For alternating current voltage, V bais R is the DC bias voltage. f R is the feedback resistor for the cross-group amplifier. g This is the gain resistor for an AC in-phase amplifier.

5. The circuit for high-precision weak current acquisition using a low-precision ADC according to claim 1, characterized in that: The signal amplification module also includes a photodiode PD1, which is used to convert optical signals into current signals. The photodiode PD1 has a dark current at the pA level, and the current increases to the uA level when there is light.

6. The circuit for achieving high-precision weak current acquisition using a low-precision ADC according to claim 1, characterized in that: The circuit also includes a resistor R4, connected to the input of the AC in-phase amplifier, to provide a DC bias voltage to improve the sampling accuracy of the ADC.

7. The circuit for high-precision weak current acquisition using a low-precision ADC according to claim 1, characterized in that: The circuit also includes a resistor R5, which is connected to the output terminal of the AC non-inverting amplifier and is used to set the gain of the AC non-inverting amplifier.

8. The circuit for achieving high-precision weak current acquisition using a low-precision ADC according to claim 1, characterized in that: The circuit also includes a resistor R6, which is connected to the feedback loop of the AC non-inverting amplifier and is used to set the feedback coefficient of the AC non-inverting amplifier.

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