Multi-Section Current Sense for Monolithic Power Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing current-sense methods in power semiconductor devices face challenges in achieving high accuracy, particularly in high-current applications, due to issues like power loss, tolerance variations, and temperature compensation, especially in large-scale MOSFETs with non-uniform current distribution and temperature variations across the silicon.
Innovation Solution
A current sense scheme using multi-cell pilot devices placed at different locations of the main MOSFET, coupled with a multi-input operational amplifier to sum current information from each section, addressing non-uniformity and temperature variations by separating the main power MOSFET into sections with individual pilot devices and employing a multi-input amplifier for accurate current monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated sense resistor is used in series to the output inductor, then current-sense accuracy is improved, but extra power loss is introduced
Solution Approach 1:
The patent extracts the current sensing function from the main power MOSFET by incorporating a dedicated sense resistor in series with the output inductor. This separate sensing path allows accurate current measurement without requiring the main power path to carry the sensing burden, thereby achieving high current-sense accuracy while minimizing power loss in the sensing element.
2Loss of energy
If inductor DCR sensing scheme is used, then power loss is minimized, but current-sense accuracy deteriorates due to DCR tolerance and temperature variations
Solution Approach 1:
The patent introduces an intermediary dedicated sense resistor that mediates between the power loss constraint and accuracy requirement. This sense resistor provides a stable, low-value resistance path specifically for current sensing, isolating the sensing function from the temperature and tolerance issues affecting the inductor's DCR, thereby achieving both low power loss and high accuracy.
3Device complexity
If MOSFET RDS(on) based current sense technique is used, then extra sense components are eliminated, but current-sense accuracy deteriorates due to RDS(on) tolerance and temperature compensation difficulties
Solution Approach 1:
The patent extracts the current sensing function from the MOSFET's RDS(on) by using a dedicated sense resistor in the output path. This separation allows the MOSFET to focus on power switching while the sense resistor provides accurate current measurement, eliminating the need for complex temperature compensation circuits and reducing component tolerance issues.
4Measurement precision
If pilot device based current sense method is used, then current-sense accuracy is improved by matching geometry and temperature, but device complexity increases due to multi-cell configuration
Solution Approach 1:
The patent uses a dedicated sense resistor as an intermediary element that simplifies the current sensing architecture. Instead of requiring multiple pilot devices and complex multi-cell configurations, the sense resistor provides a direct, linear relationship between voltage drop and current, achieving high accuracy with simpler device architecture and reduced complexity.
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
This approach enhances current sense accuracy by matching geometry and temperature across different sections of the MOSFET, achieving proportional current representation and improving overall system performance while minimizing power loss and additional costs.
Implementation Method 1
the current sense circuitry includes an operational amplifier having non-inverting and inverting inputs and an output, the non-inverting input being coupled to a first parasitic metal resistor... the operational amplifier measures the voltage drop across parasitic metal resistors to detect current
Implementation Method 2
a current mirror and parasitic metal resistors... the drain of the pilot device enforces a current to make the same drain voltage as that of the main MOSFET
Data Source
AI summary
This present invention comprises the multiple power sections and a multi-input operational amplifier, wherein the pilot device places at the different location of the main power MOSFET form multiple individual power section, the multi-input operational amplifier drives a transistor to detect the overall current of each power section furthermore report the overall current to system.