Current Limit Detector with Segmented Resistive Paths
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Solution Overview
Problem
Current limit detectors in load switch devices face limitations in accuracy and resolution due to the use of a single resistor for setting current limits, which can lead to loss of granularity and precision, especially across a wide operating voltage range.
Innovation Solution
The implementation of a device with multiple current paths, a resistive device, and comparators that allow for step-wise detection of current limits by comparing voltage drops with high and low threshold voltages, enabling precise control of current conduction through current switches and using delay elements to maintain a sequence of states and prevent race conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single resistor is used to set the current limit, then the device complexity is reduced, but the measurement precision and manufacturing precision of current limit detection deteriorate
Solution Approach 1:
The current limit detection range is segmented into multiple discrete levels (e.g., 100mA, 200mA, 500mA, 1A, 2A, 5A, 10A) corresponding to different resistor values. Instead of using a single continuous adjustment mechanism, the patent divides the detection function into discrete segments, each handled by a specific resistor. This segmentation allows for precise detection at each level while keeping the overall structure simple.
Solution Approach 2:
The patent changes the resistive parameter values to correspond to specific current limit thresholds. By selecting resistors with predetermined values (R1, R2, R3, etc.) that map to specific current limits, the system achieves precise measurement at discrete points. This parameter change approach transforms the continuous measurement problem into a discrete parameter selection problem, improving precision without increasing complexity.
2Ease of manufacture
If a single resistor with fixed value is used, then the ease of manufacture is improved, but the adaptability to different current limit requirements deteriorates
Solution Approach 1:
The patent creates a universal current limit detection system that can handle multiple current limit settings (from 100mA to 10A) using a standardized array of resistors. Each resistor serves a specific function corresponding to a particular current threshold, but collectively they provide universal coverage for various application requirements. The system can be configured for different applications by simply selecting which resistors to include or activate.
Solution Approach 2:
The system provides dynamic adaptability through the ability to select different resistor combinations based on application requirements. While each resistor has a fixed value, the overall system can dynamically adapt to different current limit needs by activating appropriate resistor subsets. This dynamic configuration capability allows the same basic circuit structure to serve multiple purposes.
3Measurement precision
If the resistive value is decreased to improve current limit resolution, then the measurement precision is improved, but the operating voltage range is reduced
Solution Approach 1:
The patent segments the operating voltage and current range into multiple zones, each handled by a resistor with an optimized value for that zone. Instead of using a single low-value resistor that would provide high resolution but limited voltage range, the system divides the detection function across multiple resistors, each optimized for specific voltage/current conditions. This segmentation allows the system to maintain high resolution across a wide overall operating range.
Solution Approach 2:
The system uses a composite approach by combining multiple resistors with different values to create an effective detection network that spans a wide voltage range. Each resistor contributes its optimal performance characteristics to a specific portion of the overall operating range, and their combination creates a system that achieves both high resolution and wide voltage compatibility, similar to how composite materials combine properties of individual materials.
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 the accuracy and resolution of current limit detection, allowing for finer control of current limits and improved protection against overloads and short circuits in load switch devices, particularly in mobile devices.
Implementation Method 1
The resistive device is of a predetermined resistive value and is coupled to the plurality of current paths. It is adapted to conduct the sum of currents which produces a voltage drop across it.
Implementation Method 2
The high-level comparator produces at the output a signal responsive to a comparison between the voltage drop and the high threshold voltage.
Data Source
AI summary
Devices, such as mobile devices, may be exposed to short circuit and output overload events. To protect against such events, mobile devices typically include current limit circuits. Some current limit circuits may involve user programmable function. User programmable function may need accurate current limit detectors. One approach to improving resolution and accuracy of current limit detectors using a single resistive device is to magnify the operating current range. Various embodiments of the present invention include devices and methods for detecting pre-programmed current limits.