Current detection circuit

Abstract

The utility model relates to the technical field of current detection, and discloses a current detection circuit, which comprises a reverse amplifier, a voltage follower, a buffer and a low-pass filter, the negative electrode end of the reverse amplifier is connected between a power supply and a resistor to be detected, the output end of the voltage follower is connected with the positive electrode end of the reverse amplifier, and the output end of the buffer is connected with the low-pass filter. The output end of the inverting amplifier is connected with the positive electrode end of the buffer, the negative electrode end of the buffer is connected to the output end of the buffer, the output end of the buffer is connected with the MCU, and the low-pass filter is arranged between the inverting amplifier and the buffer.

Description

Technical Field

[0001] This utility model relates to the field of current detection technology, and in particular to a current detection circuit. Background Technology

[0002] Current sensing circuits are an important type of circuit, playing a crucial role in various applications requiring current monitoring. By appropriately selecting the sensing resistor, measurement location and method, and paying attention to design details, stable and reliable current sensing circuits can be designed.

[0003] With the continuous development of electronic technology, current detection circuits are also constantly evolving. The development of high-side detection technology has promoted the widespread application of current detection ICs. These ICs integrate high-precision amplifiers and precision matching resistors, reducing the problems of excessive parameters and number of components caused by discrete components. However, such highly integrated ICs are also relatively expensive. Utility Model Content

[0004] In view of this, the present invention provides a current detection circuit to solve the problem of excessive discrete components in the prior art, which leads to circuit complexity and high cost.

[0005] To achieve the above objectives, this utility model proposes a current detection circuit, comprising: an inverting amplifier, a voltage follower, a buffer, and a low-pass filter;

[0006] The negative terminal of the inverting amplifier is connected between the power supply and the resistor under test. The output terminal of the voltage follower is connected to the positive terminal of the inverting amplifier. The output terminal of the inverting amplifier is connected to the positive terminal of the buffer. The negative terminal of the buffer is connected to the output terminal of the buffer. The output terminal of the buffer is connected to the MCU. A low-pass filter is provided between the inverting amplifier and the buffer.

[0007] Optionally, the inverting amplifier includes: a first resistor, a second resistor, and a first operational amplifier, wherein the negative terminal of the first operational amplifier is connected between the power supply and the resistor under test through the first resistor, and the negative terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the second resistor.

[0008] Optionally, the voltage follower includes: a first capacitor, a second capacitor, a third resistor, a fourth resistor, and a second operational amplifier. The first capacitor and the second capacitor are connected in series, the third resistor and the fourth resistor are connected in series, the positive terminal of the second operational amplifier is connected between the first capacitor and the second capacitor, the first capacitor and the third resistor are connected in parallel between a 3V power supply and the positive terminal of the second operational amplifier, the second capacitor and the fourth resistor are connected in parallel between ground and the positive terminal of the second operational amplifier, the negative terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the positive terminal of the inverting amplifier.

[0009] Optionally, the low-pass filter includes a fifth resistor and a third capacitor. The output terminal of the inverting amplifier is connected to the positive terminal of the buffer through the fifth resistor of the low-pass filter, and the fifth resistor and the positive terminal of the buffer are connected to the third capacitor.

[0010] Optionally, the current detection circuit further includes an LDO, and the output of the buffer is connected to the LDO via an MCU.

[0011] Implementing the embodiments of this utility model will have the following beneficial effects:

[0012] By combining an inverting amplifier with a voltage follower, the advantages of both can be combined to achieve more complex signal processing functions; a buffer in the output stage provides isolation between the inverting amplifier and the ADC of the subsequent MCU. Its high input impedance and low output impedance avoid any load effects within the circuit; the voltage follower raises the reference of the inverting amplifier, allowing the entire circuit to measure negative currents, eliminating the need for circuits that generate negative voltages. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or 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 only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] in:

[0015] Figure 1 This is a schematic diagram of a current detection circuit provided in an embodiment of this application. Detailed Implementation

[0016] 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.

[0017] like Figure 1 As shown, this application provides a current detection circuit, including: an inverting amplifier, a voltage follower, a buffer, and a low-pass filter;

[0018] The negative terminal of the inverting amplifier is connected between the power supply and the resistor under test. The output terminal of the voltage follower is connected to the positive terminal of the inverting amplifier. The output terminal of the inverting amplifier is connected to the positive terminal of the buffer. The negative terminal of the buffer is connected to the output terminal of the buffer. The output terminal of the buffer is connected to the MCU. A low-pass filter is provided between the inverting amplifier and the buffer.

[0019] Optionally, the inverting amplifier includes: a first resistor, a second resistor, and a first operational amplifier, wherein the negative terminal of the first operational amplifier is connected between the power supply and the resistor under test through the first resistor, and the negative terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the second resistor.

[0020] Optionally, the voltage follower includes: a first capacitor, a second capacitor, a third resistor, a fourth resistor, and a second operational amplifier. The first capacitor and the second capacitor are connected in series, the third resistor and the fourth resistor are connected in series, the positive terminal of the second operational amplifier is connected between the first capacitor and the second capacitor, the first capacitor and the third resistor are connected in parallel between a 3V power supply and the positive terminal of the second operational amplifier, the second capacitor and the fourth resistor are connected in parallel between ground and the positive terminal of the second operational amplifier, the negative terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the positive terminal of the inverting amplifier.

[0021] Optionally, the low-pass filter includes a fifth resistor and a third capacitor. The output terminal of the inverting amplifier is connected to the positive terminal of the buffer through the fifth resistor of the low-pass filter, and the fifth resistor and the positive terminal of the buffer are connected to the third capacitor.

[0022] Optionally, the current detection circuit further includes an LDO, and the output of the buffer is connected to the LDO via an MCU.

[0023] For example, such as Figure 1 As shown, current flows through resistor R28, and a relatively small voltage signal Vr (usually in the mV range, depending on the current being measured and the value of the test resistor R28) is measured across R28. Vr is amplified by an inverting amplifier composed of U5B and external circuitry. U5A, along with resistors R29 and R33, forms a voltage follower, the purpose of which is to generate a relatively stable voltage V. REF V REF The purpose of using the reference voltage of the inverting amplifier constructed with U5B is to raise the output reference of the directional amplifier to V. REF This allows us to measure the current flowing through R28, whether the battery is charging or discharging; R24 and C11 together form a low-pass filter, the purpose of which is to filter out high-frequency interference and noise; U4A acts as a buffer, its function is to buffer and perform impedance matching with the ADC input of the subsequent MCU.

[0024] For example, the specific calculation process includes:

[0025] The output voltage V of the voltage follower REF :

[0026]

[0027] Amplifier output voltage V O :

[0028] V O =-G×V r +V REF

[0029] The gain G of the inverting amplifier:

[0030]

[0031] The amplification factor G of the inverting amplifier can be obtained by algebraism. O :

[0032]

[0033] The reference voltage V REF Substituting into the above equation, we get V O :

[0034]

[0035] Transforming the above equation, we get Vr:

[0036]

[0037] In the above formula, V OIt can be read directly through the MCU's ADC. (U4A does not change the output of the inverting amplifier; it only serves as a buffer and impedance matching mechanism, so V...) OUT =V O ).

[0038] Substituting the resistance value of R28 into the above formula, we can calculate the current I flowing through R28. R28 :

[0039]

[0040] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

[0041] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Therefore, any equivalent variations made in accordance with the claims of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A current detection circuit, characterized in that, include: Inverting amplifier, voltage follower, buffer, and low-pass filter; The negative terminal of the inverting amplifier is connected between the power supply and the resistor under test. The output terminal of the voltage follower is connected to the positive terminal of the inverting amplifier. The output terminal of the inverting amplifier is connected to the positive terminal of the buffer. The negative terminal of the buffer is connected to the output terminal of the buffer. The output terminal of the buffer is connected to the MCU. A low-pass filter is provided between the inverting amplifier and the buffer.

2. The current detection circuit as described in claim 1, characterized in that, The inverting amplifier includes a first resistor, a second resistor, and a first operational amplifier, wherein the negative terminal of the first operational amplifier is connected between the power supply and the resistor under test through the first resistor, and the negative terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the second resistor.

3. The current detection circuit as described in claim 1, characterized in that, The voltage follower includes: a first capacitor, a second capacitor, a third resistor, a fourth resistor, and a second operational amplifier. The first capacitor and the second capacitor are connected in series, the third resistor and the fourth resistor are connected in series, the positive terminal of the second operational amplifier is connected between the first capacitor and the second capacitor, the first capacitor and the third resistor are connected in parallel between a 3V power supply and the positive terminal of the second operational amplifier, the second capacitor and the fourth resistor are connected in parallel between ground and the positive terminal of the second operational amplifier, the negative terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the positive terminal of the inverting amplifier.

4. The current detection circuit as described in claim 1, characterized in that, The low-pass filter includes a fifth resistor and a third capacitor. The output terminal of the inverting amplifier is connected to the positive terminal of the buffer through the fifth resistor of the low-pass filter, and the fifth resistor and the positive terminal of the buffer are connected to the third capacitor.

5. The current detection circuit as described in claim 1, characterized in that, It also includes an LDO, the output of which is connected to the MCU.

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