Wide Range Current Sensing Circuit with Dynamic Mirror Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current current sensing circuits face challenges in maintaining high accuracy over a wide range of currents, such as 100 μA-1 A, due to difficulties in scalability and high offset requirements, leading to impedance and voltage jumps.
Innovation Solution
A circuit with a pass device and a sense device forming a current mirror, where the mirror ratio is adjustable based on the load current, using feedback loops and measurement circuitry to regulate voltage drops and set the mirror ratio, allowing for accurate current sensing across multiple orders of magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed mirror ratio is used in the current sensing circuit, then the circuit structure is simple, but the measurement precision deteriorates over a wide current range
Solution Approach 1:
The patent implements a dynamic mirror ratio adjustment mechanism where the sense device includes multiple transistor devices that can be selectively switched between active and inactive states. This allows the mirror ratio to be dynamically changed based on the load current magnitude, enabling accurate current sensing across a wide range from 100 μA to 1 A while maintaining reasonable circuit complexity through systematic switching control.
2Measurement precision
If the mirror ratio is adjusted to maintain accuracy over wide current range, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The sense device is segmented into multiple transistor devices (first, second, third transistor devices) that can be independently controlled. This segmentation allows the circuit to achieve variable mirror ratios by switching specific segments on or off, thereby improving measurement precision across different current ranges while managing complexity through modular design.
Solution Approach 2:
The patent employs feedback loops including a first feedback loop that regulates the voltage drop across the pass device and a second feedback loop (voltage drop equalizer) that equalizes voltage drops across the pass and sense devices. This feedback mechanism automatically adjusts the operating conditions to maintain accuracy across wide current ranges, reducing the need for complex manual calibration and offset compensation circuits.
3Device complexity
If conventional current sensing is used, then the circuit is simple, but offset requirements are high leading to impedance and voltage jumps
Solution Approach 1:
The patent implements a voltage drop equalizer (second feedback loop) that actively equalizes the voltage drops across the pass device and sense device. This feedback mechanism significantly reduces offset requirements and prevents impedance and voltage jumps during current transitions, thereby improving sensing stability and reliability while maintaining relatively simple circuit structure.
Solution Approach 2:
The patent dynamically changes the mirror ratio parameter by switching transistor devices between active and inactive states based on the load current magnitude. This parameter adjustment allows the circuit to adapt to different operating conditions, maintaining stable and accurate sensing across wide current ranges without requiring high offset compensation circuits.
Data Source
AI summary
A circuit and a method using a pass device that is coupled between a supply voltage level and a load-connectable node of the circuit for providing a load current. A sense device forms a current mirror with the pass device. The sense device has transistor devices that can be switched to an active state, to adjust a mirror ratio of the current mirror. A first feedback loop regulates a voltage drop across the pass device to a predetermined value. A second feedback loop regulates a voltage drop across the sense device to the voltage drop across the pass device. Measurement circuitry sets a mirror ratio of the current mirror based on an indication of a current flowing through the sense device and generates an indication of current flowing through the pass device based on the set mirror ratio and the indication of the current flowing through the sense device.