Current sampling circuit
By designing a current sampling circuit using a two-stage current follower and a BAT54SLT1G diode, the problems of insufficient accuracy, significant environmental impact, high power consumption, and narrow applicability of existing current sampling circuits are solved. This design achieves high-precision, low-interference current measurement, suitable for a variety of applications.
Patent Information
- Application Number
- CN202423248522.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-12-19
- Estimated Expiration
- 2034-12-27
AI Technical Summary
Existing current sampling circuits suffer from insufficient accuracy, significant environmental impact, high power consumption, cost and size limitations, and narrow applicability, making it difficult to meet the requirements for high accuracy and energy saving.
The current sampling circuit design employs a two-stage current follower and a BAT54SLT1G diode. It utilizes a low-voltage operational amplifier and a bidirectional bispindle Schottky diode for electrical isolation and signal stabilization, reducing interference and improving signal accuracy and isolation effect.
It achieves high-precision current measurement, reduces power consumption, enhances circuit stability and isolation, reduces noise interference, protects subsequent circuits, and is suitable for a variety of application scenarios.
Smart Images
Figure CN223692442U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to inductance current sampling, concretely relates to a current sampling circuit. BACKGROUND
[0002] Current sampling circuit is an important component in the field of electronic technology, and is mainly used for measuring current in a circuit so as to monitor and control. The existing forms mainly include a circuit built by a traditional sampling resistor and a linear optocoupler and a circuit realized by using a high-voltage linear current sensor.
[0003] The existing forms of current sampling circuit have various defects and disadvantages, mainly including:
[0004] Precision problem: when using MOSFET to detect current, although the signal precision is about 10% to 20%, this range may not be ideal for applications requiring high-precision measurement. Especially for current control applications requiring 1% precision or higher, this method is usually not suitable. The double-resistor sampling method has great limitations when the sampling window is small, because it cannot use the formula I U +I V +I W = 0.
[0005] Environmental impact: linear Hall effect sensor has poor measurement effect when the current is low or the distance between the sensor and the current is large. Changes in the environmental magnetic field and other current lines near the sensor will change the magnetic field at the sensor location, affecting the measurement precision. The TRACE resistance measurement method does not introduce additional resistance and does not produce additional power loss, but the voltage signal generated is very small, and a high-gain amplifier is needed to amplify the voltage signal, but the bandwidth performance of the amplifier has always been a bottleneck.
[0006] Power consumption: when using shunt resistance to measure current, connecting resistance to the circuit to be measured will cause power consumption, which is a problem that cannot be ignored in high-precision measurement or energy-saving applications.
[0007] Cost and volume: although the shunt resistance method has low cost and small volume, it has large temperature drift, it is difficult to select precision resistors, and it has no isolation effect, which limits its use in some applications.
[0008] Limited application range: the inductance DC resistance measurement circuit needs to be accurately debugged before sampling, and is usually only suitable for switch power supply lossless current measurement and low voltage (less than 1.5V) current measurement occasions, and has a narrow application range.
[0009] In summary, the current sampling circuit of the prior art has various defects and drawbacks, including precision problems, environmental influences, power consumption, cost and volume, and application range limitations. Therefore, it is desirable to reduce unnecessary power consumption of the current sampling circuit, improve precision, increase electrical isolation, and enhance stability. Summary of the utility model
[0010] The utility model discloses a current sampling circuit, which is used to solve the above problems.
[0011] In order to realize the above object, the utility model provides the following technical scheme:
[0012] A current sampling circuit, comprising a plug-in terminal U601, a first-stage current follower, a second-stage current follower and a BAT54SLT1G diode, wherein:
[0013] The pin 7 of the plug-in terminal U601 is connected with the input end of the first-stage current follower;
[0014] The output end of the first-stage current follower is connected with the input end of the second-stage current follower;
[0015] The output end of the second-stage current follower is connected with the No. 3 pin of the BAT54SLT1G diode.
[0016] Preferably, the No. 1 pin of the BAT54SLT1G diode is grounded, and the No. 2 pin is connected with 3.3V.
[0017] Preferably, the first-stage current follower comprises a low-voltage operational amplifier, and a fixed resistor R604 and a capacitor C626 are connected in parallel on the circuit between the input end of the low-voltage operational amplifier and the pin 7 of the plug-in terminal U601, the pin of the fixed resistor R604 is connected with the pin of the capacitor C626, and the pin of the capacitor C626 is grounded.
[0018] Preferably, a resistor R605 and a resistor R610 are connected in series on the circuit between the output end of the first-stage current follower and the input end of the second-stage current follower, and a capacitor C628 is connected in parallel on the circuit where the pins of the resistor R605 and the resistor R610 are connected, and the pin of the capacitor C628 is grounded.
[0019] Preferably, the second-stage current follower comprises a low-voltage operational amplifier, a resistor R606 is connected in series on the circuit between the output end of the low-voltage operational amplifier and the No. 3 pin of the BAT54SLT1G diode, and a capacitor C629 is connected in parallel on the output end of the resistor R606, and the pin of the capacitor C629 is grounded.
[0020] As preferred, the BAT54SLT1G diode is a bidirectional bipolar transistor Schottky diode.
[0021] In the above technical solution, the current sampling circuit provided by the utility model has the following beneficial effects: two-stage current followers are used, the purpose is to provide stronger electrical isolation, make the coupling between the sampling circuit and the subsequent circuit weaker, reduce mutual interference, further stabilize the current signal, and reduce signal fluctuation caused by circuit parameter change or external interference.
[0022] And it can also prevent damage to the subsequent circuit caused by current mutation or overload, reduce noise in the signal, and improve the signal-to-noise ratio of the signal. BRIEF DESCRIPTION OF DRAWINGS
[0023] In order to more clearly illustrate the technical solutions in the embodiments or prior art, the drawings needed in the embodiments will be briefly introduced below, and obviously, the drawings in the following description are only some embodiments described in the utility model, and other drawings can also be obtained by those skilled in the art according to these drawings.
[0024] Figure 1 The circuit structure schematic diagram provided by the utility model embodiment. DETAILED DESCRIPTION
[0025] In order to make those skilled in the art better understand the technical solutions of the utility model, the utility model will be further described in detail below in combination with the drawings.
[0026] As Figure 1 shown, a current sampling circuit, comprising a plug-in terminal U601, a first-stage current follower, a second-stage current follower and a BAT54SLT1G diode, in detail: 7-pin current signal collection, RC in parallel and then grounded, filter the collected current signal, connected to the non-inverting input terminal of the first-stage current follower, while the output terminal of the first-stage current follower is connected to the input terminal of the reverse first-stage current follower through a feedback resistor, forming a high-gain negative feedback system. Therefore, the voltage through the first-stage current follower will not amplify the input signal, and the voltage gain is 1. The first-stage current follower only provides buffering. It has very high input impedance and very low output impedance, so it can effectively maintain the accuracy and stability of the signal. After filtering the output signal, it is connected to a second-stage current follower, and the output terminal of the second-stage current follower is filtered by an RC circuit. The output signal is voltage clamped by the BAT54SLT1G diode, limited to 3.3V.
[0027] 3. The current sampling circuit according to any one of the preceding claims, characterized in that the first-stage current follower comprises a low-voltage operational amplifier, and a fixed resistor R604 and a capacitor C626 are connected in parallel on the circuit between the input terminal of the low-voltage operational amplifier and the pin 7 of the plug-in terminal U601, the pin of the fixed resistor R604 is connected to the pin of the capacitor C626, and the pin of the capacitor C626 is grounded.
[0028] It should be noted that the clamping function is crucial to prevent the circuit from being damaged due to excessively high voltage. These analog signals then need to be converted into digital signals for processing by a digital control system.
[0029] Further, in combination with Figure 1 It can be seen that the resistor R605 and the resistor R610 are connected in series on the circuit between the output terminal of the first-stage current follower and the input terminal of the second-stage current follower, and the capacitor C628 is connected in parallel on the circuit between the pins of the resistor R605 and the resistor R610, and the pin of the capacitor C628 is grounded.
[0030] Still further, in combination with Figure 1 It can be seen that the second-stage current follower comprises a low-voltage operational amplifier, and the resistor R606 is connected in series on the circuit between the output terminal of the low-voltage operational amplifier and the pin 3 of the BAT54SLT1G diode, and the capacitor C629 is connected in parallel on the output terminal of the resistor R606, and the pin of the capacitor C629 is grounded.
[0031] Secondly, the BAT54SLT1G diode provided by the embodiment is a bidirectional bipolar double-tube Schottky diode. It has high-speed switching characteristics, low forward voltage drop, and bidirectional conduction capability. This diode is designed for high-speed switching applications, circuit protection, and voltage clamping, and its extremely low forward voltage helps to reduce conduction losses. Its miniature surface-mount package is ideal for space-constrained handheld and portable applications. Moreover, the BAT54SLT1G diode has three pins. The functions of these three pins are as follows:
[0032] 1. Anode 1 (A1): The anode of the first Schottky diode. In the circuit, current flows into the first diode through this pin.
[0033] 2. Cathode (K): The cathode shared by both Schottky diodes. Current flows out of the diodes from this pin. In voltage clamping or other circuit configurations, this pin is usually connected to ground (GND) or other reference potential.
[0034] 3. Anode 2 (A2): The anode of the second Schottky diode. Similar to the anode of the first diode, current flows into the second diode through this pin.
[0035] In voltage clamping applications, these two Schottky diodes can be used in parallel to provide bidirectional voltage protection. For example, if you need to clamp voltage spikes on a signal line, you can connect the anode of the first diode to the signal line and the cathode to ground, and the second diode in reverse, with its anode connected to ground and its cathode connected to the signal line. In this way, whether the voltage spike is positive or negative, the corresponding diode will conduct and clamp the voltage below its forward voltage drop, thus protecting the circuit from damage.
[0036] Furthermore, it should be noted that the LMV358IDR low voltage operational amplifier has a rail-to-rail output swing. This operational amplifier is designed for low voltage (2.7V to 5V) operation, and its performance specifications meet or exceed those of the LM358 and LM324 devices operating at 5V to 30V, and can be configured as a current follower.
[0037] And in the follower configuration, the inverting input (-) of the operational amplifier is connected to the output, forming a voltage follower. This configuration has several characteristics:
[0038] 1. High input impedance: Since the input impedance of the operational amplifier is very high, the follower provides a high impedance input, which helps prevent load effects on the circuit connected to it
[0039] 2. Low output impedance: The output impedance of the follower is very low because it is directly connected to the output of the operational amplifier, which allows it to drive low impedance loads.
[0040] 3. Gain close to 1: In ideal conditions, the voltage gain of the follower is close to 1, i.e. the output voltage is almost equal to the input voltage. This means that the amplitude of the input signal remains unchanged at the output.
[0041] 4. Phase preservation: The follower does not change the phase of the input signal, i.e. the input and output signals maintain the same phase.
[0042] 5. Signal buffering: The follower can be used for signal buffering to reduce signal loss during transmission, especially in long cables or complex circuits.
[0043] 6. Isolation: In some applications, the follower can act as an isolation between the input and output, reducing noise and interference on the signal path.
[0044] 7. Non-inverting amplification: Although the gain of the follower is close to 1, the operational amplifier can also achieve non-inverting amplification by adding resistors in the feedback path or using other configurations.
[0045] 8. Stability: Since the open-loop gain of the follower is very high, it is usually very stable and not susceptible to oscillation.
[0046] In summary, the above-mentioned circuit has the characteristics of high input impedance and low output impedance, so that it can minimize the interference to the original circuit when sampling current, because it consumes very little current and does not affect the original circuit. At the same time, due to the low output impedance, the follower can effectively drive the subsequent circuit or load, providing stable current sampling output.
[0047] Secondly, the current follower acts as an isolation buffer, which can isolate the circuit and reduce power interference. During the process of sampling current, this isolation helps to protect the original circuit from external interference and ensures the accuracy of the sampled data.
[0048] In addition, the voltage gain of the current follower is close to 1, which means that the output voltage can almost follow the input voltage without loss, providing extremely high signal retention capability. This feature makes the follower particularly important in applications that require signal integrity and reduce signal loss.
[0049] In summary, the application of the follower in the current sampling circuit can provide high input impedance, low output impedance, low interference and signal retention capability, etc. It is an ideal choice for current sampling circuit.
[0050] The above only describes some exemplary embodiments of the present application by way of illustration, without doubt, for those skilled in the art, without departing from the spirit and scope of the present application, the described embodiments can be modified in various ways. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present application.
Claims
1. A current sampling circuit, characterized by, The plug-in terminal U601, a first-stage current follower, a second-stage current follower and a BAT54SLT1G diode are included, wherein: Pin 7 of the plug-in terminal U601 is connected to an input terminal of the first-stage current follower; An output terminal of the first-stage current follower is connected to an input terminal of the second-stage current follower; An output terminal of the second-stage current follower is connected to pin 3 of the BAT54SLT1G diode.
2. The current sampling circuit of claim 1, wherein, Pin 1 of the BAT54SLT1G diode is grounded, and pin 2 is connected to 3.3V.
3. The current sampling circuit of claim 1, wherein, The first-stage current follower includes a low-voltage operational amplifier, and a fixed resistor R604 and a capacitor C626 are connected in parallel between an input terminal of the low-voltage operational amplifier and pin 7 of the plug-in terminal U601, a pin of the fixed resistor R604 is connected to a pin of the capacitor C626, and a pin of the capacitor C626 is grounded.
4. The current sampling circuit of claim 1, wherein, A resistor R605 and a resistor R610 are connected in series between an output terminal of the first-stage current follower and an input terminal of the second-stage current follower, and a capacitor C628 is connected in parallel between pins of the resistor R605 and the resistor R610, and a pin of the capacitor C628 is grounded.
5. The current sampling circuit of claim 1, wherein, The second-stage current follower includes a low-voltage operational amplifier, a resistor R606 is connected in series between an output terminal of the low-voltage operational amplifier and pin 3 of the BAT54SLT1G diode, and a capacitor C629 is connected in parallel at an output terminal of the resistor R606, and a pin of the capacitor C629 is grounded.
6. The current sampling circuit of claim 1, wherein, The BAT54SLT1G diode is a bidirectional bipolar double-tube Schottky diode.