Transconductance Current Monitoring AFE for Fast Overcurrent Sensing
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Solution Overview
Problem
Existing current monitoring circuits in electronic systems face challenges in achieving fast and accurate detection of overcurrent events, particularly due to limitations in response time and stability in high-speed applications such as motor drivers and LED drivers.
Innovation Solution
A high-speed analog front-end (AFE) circuit utilizing a first transconductance amplifier to convert voltage across a sense resistor into a monitoring current and a second transconductance amplifier to generate a reference current, both injected into a high impedance node coupled to an inverter, allowing for high-speed comparison and rapid indication of overcurrent events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a traditional amplifier and comparator circuit is used for current monitoring, then the circuit can detect overcurrent events, but the response time is slow and cannot meet high-speed application requirements
Solution Approach 1:
The patent replaces the traditional mechanical/electronic amplifier-comparator system with a transconductance amplifier-based current sensing system. The transconductance amplifier directly converts the sense voltage to a current signal that can be rapidly compared with the reference current, eliminating the bandwidth limitations of traditional voltage amplifiers and achieving nanosecond-level response times while maintaining protection reliability.
Solution Approach 2:
The patent changes the operating parameters by using transconductance amplifiers that operate in a linear region optimized for fast response. The circuit maintains the sense resistor in a low-value state to minimize power loss while the transconductance amplifier provides high gain for accurate threshold detection, achieving both fast response and reliable protection.
2Measurement precision
If the sense resistor value is increased to improve current detection accuracy, then measurement precision improves, but power loss increases
Solution Approach 1:
The patent introduces a transconductance amplifier as an intermediary device that takes the small voltage signal from a low-value sense resistor and converts it to a proportional current signal. This intermediary amplification stage enables accurate current measurement with minimal sense resistor values, thereby reducing power loss while maintaining measurement precision through the high gain of the transconductance amplifier.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables fast detection of current thresholds with response times in the order of nanoseconds, improving overcurrent protection and reducing delay, thereby enhancing the reliability of current monitoring in various electronic circuits.
Implementation Method 1
a first transconductance amplifier having first and second inputs configured to be coupled across a sense resistive element, and an output coupled to an input of the inverter
Implementation Method 2
a current generator having a second transconductance amplifier configured to generate a reference current at an output of the current generator based on a reference voltage
Implementation Method 3
the output of the inverter is configured to be in a first state when a load current flowing through the sense resistive element is higher than a predetermined threshold, and in a second state when the load current is lower than the predetermined threshold
Data Source
AI summary
A current monitoring circuit includes: an output terminal configured to be coupled to a controller; an inverter having an output coupled to the output terminal; a first transconductance amplifier having first and second inputs configured to be coupled across a sense resistive element, and an output coupled to an input of the inverter; and a current generator having a second transconductance amplifier configured to generate a reference current at an output of the current generator based on a reference voltage, the output of the current generator being coupled to the input of the inverter, where the output of the inverter is configured to be in a first state when a load current flowing through the sense resistive element is higher than a predetermined threshold, and in a second state when the load current is lower than the predetermined threshold, and where the predetermined threshold is based on the reference current.