Current Sensing Circuit Eliminates RC Effect With Feedback
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Solution Overview
Problem
Conventional current sensing circuits face challenges due to the RC effect caused by input resistance and capacitance, leading to increased circuit complexity and difficulty in matching amplifiers operating in different power domains.
Innovation Solution
A current sensing circuit design that includes an amplifier, input resistor, sensing resistor, and feedback circuit, where the feedback circuit outputs a sensing voltage equal to the voltage across the sensing resistor, effectively eliminating the RC effect and simplifying circuit matching by using feedback transistors and resistors to balance the input current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional resistance is added to balance the RC effect, then the RC effect is compensated, but the circuit complexity increases and additional resistor element matching is required
Solution Approach 1:
The patent merges the RC effect compensation function into the existing input resistor by configuring the amplifier's input terminals such that the input resistor is coupled between the first and second input terminals. The amplifier's differential input structure inherently balances the RC effect caused by input resistance and capacitance, eliminating the need for separate compensation resistors while maintaining measurement accuracy.
2Reliability
If multiple amplifiers are used to overcome the RC effect, then the RC effect is compensated, but the circuit complexity increases and matching becomes difficult due to different power domains
Solution Approach 1:
The patent combines multiple amplifier functions into a single amplifier by utilizing its differential input terminals. The first input terminal receives the signal through the input resistor, while the second input terminal is connected to a reference voltage, allowing the amplifier to inherently compensate for RC effects through its differential architecture without requiring multiple separate amplifier components.
Solution Approach 2:
The single amplifier is designed to perform multiple functions: signal amplification, RC effect compensation, and differential voltage output. By coupling the input resistor between the first and second input terminals and utilizing the amplifier's differential input stage, the circuit achieves balanced operation across different power domains without requiring multiple amplifiers.
3Productivity
If a conventional current sensing circuit is used with input resistor coupled to amplifier input terminal, then current sensing is achieved, but the RC effect degrades measurement precision
Solution Approach 1:
The patent merges the current sensing function with RC effect compensation by configuring the input resistor between the amplifier's first and second input terminals. The amplifier's differential input structure simultaneously performs current-to-voltage conversion and RC effect balancing, maintaining measurement precision while enabling current sensing functionality.
Data Source
AI summary
A current sensing circuit is provided. The current sensing circuit includes an amplifier, an input resistor, a sensing resistor, and a feedback circuit. The amplifier has a first input terminal, a second input terminal, a third input terminal, and an output terminal. The input resistor is coupled between the first input terminal and the second input terminal of the amplifier. The sensing resistor is coupled between the second input terminal and the third input terminal of the amplifier. The feedback circuit is coupled between the first input terminal and the output terminal. When an input current flows through the sensing resistor, a voltage across the sensing resistor is equal to a voltage across the input resistor, and the feedback circuit correspondingly outputs a sensing voltage according to the input current.