A direct current voltage ADC sampling circuit

Abstract

This invention discloses a DC voltage ADC sampling circuit, comprising a voltage divider resistor network and a three-terminal adjustable precision regulator. The two ends of the voltage divider resistor network are connected to the VCC input terminal and the positive terminal of the sampling resistor, respectively. The anode and cathode of the three-terminal adjustable precision regulator are also connected to the positive terminal of the sampling resistor and the VCC input terminal, respectively. The reference terminal of the three-terminal adjustable precision regulator is connected to a voltage divider node in the voltage divider resistor network. After constant voltage division by the voltage divider resistor network and the three-terminal adjustable precision regulator, the voltage at the positive terminal of the sampling resistor meets the input range of the ADC. This method can filter out a portion of the DC component in the DC voltage, retaining the variable part, thus achieving high sampling accuracy even with low ADC sampling resolution. The circuit is simple and inexpensive, making it very suitable for the increasingly compact PCBs and cost-sensitive electronic products, and has a wide range of applications and high application value.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, specifically to a DC voltage ADC sampling circuit. Background Technology

[0002] With the widespread use of electronic products, when measuring a DC voltage in electronic circuits, it's sometimes necessary to pay attention to the voltage variation, such as in lithium-ion batteries and lead-acid batteries. After a period of use, the battery voltage will decrease. In low-cost solutions, an analog-to-digital converter (ADC) is used to sample this voltage and determine the battery's current charge. However, because the varying voltage is relatively small compared to the original DC voltage, directly using a resistor divider will reduce the accuracy of the ADC sampling. Using a differential operational amplifier would significantly increase costs; and using a Zener diode would increase the sampling error. Summary of the Invention

[0003] Therefore, embodiments of the present invention provide a DC voltage ADC sampling circuit to solve the technical problem that it is difficult to achieve high sampling accuracy under low ADC sampling resolution conditions in the prior art.

[0004] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0005] According to a first aspect of the present invention, a DC voltage ADC sampling circuit is provided, comprising a VCC input terminal, a sampling resistor, and a power supply negative terminal GND connected in series. The positive terminal of the sampling resistor is connected to the input pin of the ADC. The circuit further includes a voltage divider resistor network and a three-terminal adjustable precision voltage regulator. The two ends of the voltage divider resistor network are respectively connected to the VCC input terminal and the positive terminal of the sampling resistor. The anode and cathode of the three-terminal adjustable precision voltage regulator are also respectively connected to the positive terminal of the sampling resistor and the VCC input terminal. The reference terminal of the three-terminal adjustable precision voltage regulator is connected to the voltage divider node in the voltage divider resistor network. After constant voltage division by the voltage divider resistor network and the three-terminal adjustable precision voltage regulator, the voltage at the positive terminal of the sampling resistor satisfies the input range of the ADC.

[0006] Furthermore, the three-terminal adjustable precision voltage regulator adopts TL431, TL432, LM431 or KA431.

[0007] Furthermore, the voltage divider resistor network includes a first voltage divider resistor R4 and a second voltage divider resistor R5 connected in series.

[0008] Furthermore, the resistance values ​​of the first voltage divider resistor R4 and the second voltage divider resistor R5 are equal.

[0009] Furthermore, the voltage value of the three-terminal adjustable precision voltage regulator is a fixed value, and the calculation expression for the fixed voltage value is as follows:

[0010] U1 = 2.5 × (1 + ).

[0011] Furthermore, the expression for the voltage across the sampling resistor is:

[0012] U2 = VCC - U1.

[0013] Furthermore, the TL431 is packaged in an SOT-23 package.

[0014] Furthermore, the resistance value of the sampling resistor is equal to the resistance values ​​of the first voltage divider resistor R4 and the second voltage divider resistor R5.

[0015] The embodiments of the present invention have the following advantages:

[0016] This invention includes a voltage divider resistor network and a three-terminal adjustable precision voltage regulator. The two ends of the voltage divider resistor network are connected to the VCC input terminal and the positive terminal of the sampling resistor, respectively. The anode and cathode of the three-terminal adjustable precision voltage regulator are also connected to the positive terminal of the sampling resistor and the VCC input terminal, respectively. The reference terminal of the three-terminal adjustable precision voltage regulator is connected to a voltage divider node in the voltage divider resistor network. After constant voltage division by the voltage divider resistor network and the three-terminal adjustable precision voltage regulator, the voltage at the positive terminal of the sampling resistor meets the input range of the ADC. This allows for the filtering out of a portion of the DC component in the DC voltage, retaining the variable portion. Therefore, high sampling accuracy can be achieved even with low ADC sampling resolution. This method has a simple circuit, low cost, and is very suitable for the increasingly compact PCBs and cost-sensitive electronic products, possessing a wide range of applications and high application value. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0018] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0019] Figure 1 This is a schematic diagram of the logic structure of a DC voltage ADC sampling circuit provided in an embodiment of the present invention. Detailed Implementation

[0020] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To address the aforementioned technical challenge of achieving high sampling accuracy under conditions of low ADC sampling resolution.

[0022] refer to Figure 1 This invention discloses a DC voltage ADC sampling circuit, which consists of a VCC input terminal, a sampling resistor, and a power supply negative terminal GND connected in series. The positive terminal of the sampling resistor is connected to the input pin of the ADC. The circuit also includes a voltage divider resistor network and a three-terminal adjustable precision voltage regulator. The two ends of the voltage divider resistor network are connected to the VCC input terminal and the positive terminal of the sampling resistor, respectively. The anode and cathode of the three-terminal adjustable precision voltage regulator are also connected to the positive terminal of the sampling resistor and the VCC input terminal, respectively. The reference terminal of the three-terminal adjustable precision voltage regulator is connected to the voltage divider node in the voltage divider resistor network. After constant voltage division by the voltage divider resistor network and the three-terminal adjustable precision voltage regulator, the voltage at the positive terminal of the sampling resistor meets the input range of the ADC.

[0023] Furthermore, the three-terminal adjustable precision voltage regulator adopts TL431, TL432, LM431 or KA431.

[0024] Furthermore, the voltage divider resistor network includes a first voltage divider resistor R4 and a second voltage divider resistor R5 connected in series.

[0025] Furthermore, the resistance values ​​of the first voltage divider resistor R4 and the second voltage divider resistor R5 are equal.

[0026] Furthermore, the voltage value of the three-terminal adjustable precision voltage regulator is a fixed value, and the calculation expression for the fixed voltage value is as follows:

[0027] U1 = 2.5 × (1 + ).

[0028] Furthermore, the expression for the voltage across the sampling resistor is:

[0029] U2 = VCC - U1.

[0030] Furthermore, the TL431 is packaged in an SOT-23 package.

[0031] Furthermore, the resistance value of the sampling resistor is equal to the resistance values ​​of the first voltage divider resistor R4 and the second voltage divider resistor R5.

[0032] refer to Figure 1 U1 is the TL431 chip, R4 and R5 are voltage divider resistors used to determine the voltage across the TL431, and R6 is the data acquisition resistor. The voltage across the TL431 is: U1 = 2.5 × (1 + ... The voltage across R6 is U2 = VCC - U1. Since the voltage U1 is fixed after being set, the common-mode voltage on U2 will be greatly reduced, and the ADC sampling range will also increase, thus improving the sampling accuracy of DC voltage changes.

[0033] like Figure 1 The circuit shown includes a VCC input terminal, a TL431 chip U1, voltage divider resistors R4 and R5, a sampling resistor R6, and an ADC sampling point U2. The anode of U1 is grounded, the cathode is connected to the first terminal of R6, and the reference terminal is connected to the first terminal of R4. The second terminal of R4 and the first terminal of R5 are both connected to the cathode of U1, and the second terminal of R5 is grounded. The second terminal of R6 is connected to VCC, and U2 is located at the junction of R6 and the cathode of U1.

[0034] In a 12V lead-acid battery monitoring scenario, resistors R4, R5, and R6 are configured with a resistance of 10 kΩ, R5, and R6 respectively. U1 outputs a fixed voltage of 5.0V, and the voltage at U2 is VCC minus 5.0V. When VCC drops from 12.0V to 11.9V, U2 drops from 7.0V to 6.9V, achieving lossless conversion of ±0.1V variations.

[0035] To enhance anti-interference capability, a 10 nanofarad ceramic capacitor C1 is connected in parallel between the reference and cathode of U1, and the resistance of R4 is adjusted to 40 kΩ. At this time, U1 outputs 12.5V, which is suitable for a 15V DC system, and the voltage at the U2 terminal is VCC minus 12.5V.

[0036] For accurate acquisition of a 12V battery system, U1 is set to 11.5V (achieved through R4 with a resistance of 36 kΩ and R5 with a resistance of 10 kΩ), and a 1 kΩ resistor and a 100 nanofarad capacitor are connected in series at the ADC input to form a low-pass filter. When VCC fluctuates between 11.9V and 12.1V, U2 outputs 0.4V to 0.6V, amplifying the voltage change range by 5 times.

[0037] When using the SOT-23 packaged TL431, with R4 valued at 2 kΩ and R5 valued at 10 kΩ, U1 equals 3.0V. Discharge monitoring of a 3.7V lithium battery shows that when U2 voltage drops from 0.7V to 0.6V, the corresponding battery voltage drops to 3.6V, improving the detection resolution by 3.6 times.

[0038] This invention can filter out a portion of the DC component in a DC voltage, retaining only the variable part. Therefore, it can achieve high sampling accuracy even with low ADC sampling resolution. The circuit structure proposed in this invention is simple and inexpensive, making it highly suitable for the increasingly compact PCBs and cost-sensitive demands of modern electronic products, thus possessing a wide range of applications and significant value.

[0039] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A DC voltage ADC sampling circuit, comprising a VCC input terminal, a sampling resistor, and a power supply negative terminal GND connected in series, wherein the positive terminal of the sampling resistor is connected to the input pin of the ADC, characterized in that, It also includes a voltage divider resistor network and a three-terminal adjustable precision regulator. The two ends of the voltage divider resistor network are connected to the VCC input terminal and the positive terminal of the sampling resistor, respectively. The anode and cathode of the three-terminal adjustable precision regulator are also connected to the positive terminal of the sampling resistor and the VCC input terminal, respectively. The reference terminal of the three-terminal adjustable precision regulator is connected to the voltage divider node in the voltage divider resistor network. After constant voltage division by the voltage divider resistor network and the three-terminal adjustable precision regulator, the voltage at the positive terminal of the sampling resistor meets the input range of the ADC.

2. The DC voltage ADC sampling circuit as described in claim 1, characterized in that, The three-terminal adjustable precision voltage regulator uses TL431, TL432, LM431 or KA431.

3. The DC voltage ADC sampling circuit as described in claim 1, characterized in that, The voltage divider resistor network includes a first voltage divider resistor R4 and a second voltage divider resistor R5 connected in series.

4. The DC voltage ADC sampling circuit as described in claim 1, characterized in that, The resistance values ​​of the first voltage divider resistor R4 and the second voltage divider resistor R5 are equal.

5. The DC voltage ADC sampling circuit as described in claim 1, characterized in that, The voltage value of the three-terminal adjustable precision voltage regulator is a fixed value, and the formula for calculating the fixed voltage value is: U1=2.5×（1+ ）。 6. The DC voltage ADC sampling circuit as described in claim 5, characterized in that, The expression for the voltage across the sampling resistor is: U2 = VCC - U1.

7. The DC voltage ADC sampling circuit as described in claim 2, characterized in that, The TL431 is packaged in an SOT-23 package.

8. The DC voltage ADC sampling circuit as described in claim 1, characterized in that, The resistance value of the sampling resistor is equal to the resistance values ​​of the first voltage divider resistor R4 and the second voltage divider resistor R5.

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