Adaptive Overcurrent Protection in DC-DC Power Converters
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Solution Overview
Problem
Existing power converter circuits face challenges in effectively addressing overcurrent conditions, particularly during startup and low-impedance faults, leading to runaway current conditions due to their inability to adaptively respond to a wide range of fault conditions and requiring complex analysis for implementation in integrated circuits.
Innovation Solution
A controller-based overcurrent protection scheme that counts consecutive overcurrent events and inhibits power switch conduction for an increasing number of cycles, using a function such as 2N−1, to prevent runaway currents, and can be implemented in a compact digital logic integrated circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional overcurrent protection schemes are used, then simple fault conditions can be handled, but adaptive response to wide range of fault conditions including startup and low-impedance faults is lost, leading to runaway current
Solution Approach 1:
The patent implements dynamic overcurrent protection by making the shutdown duration variable based on the number of consecutive overcurrent events detected. The controller adapts the protection response by increasing the number of shutdown cycles proportionally to the frequency of overcurrent occurrences, enabling the system to dynamically adjust its protection strategy according to actual fault conditions rather than using a fixed response.
Solution Approach 2:
The patent employs feedback mechanisms where the controller continuously monitors inductor current and detects overcurrent conditions. The detection results feed back into the control logic, which then determines the appropriate shutdown duration based on the number of consecutive overcurrent events. This closed-loop feedback enables adaptive protection that responds to the actual system state and fault patterns.
2Manufacturing precision
If complex analysis is performed for integrated circuit implementation, then precise overcurrent protection can be achieved, but design complexity and implementation difficulty increase
Solution Approach 1:
The patent segments the overcurrent protection function into distinct modular components: an overcurrent detector that monitors inductor current, a counter that tracks consecutive overcurrent events, and a controller that determines shutdown duration based on the count. This segmentation allows each component to be implemented independently with simple logic, reducing overall design complexity while maintaining precise protection functionality through coordinated operation of the segments.
Solution Approach 2:
The patent changes the parameter of shutdown duration from a fixed value to a variable that depends on the number of consecutive overcurrent events. By making this parameter adaptive rather than static, the system achieves precise protection across varying fault conditions without requiring complex analysis or multiple fixed thresholds, simplifying the controller design while improving protection accuracy.
3Productivity
If startup current is increased to ensure sufficient power, then load startup is improved, but risk of overcurrent damage increases
Solution Approach 1:
The patent implements preliminary protective action by detecting overcurrent conditions during the startup phase and immediately initiating shutdown sequences when overcurrent events are detected. The counter starts tracking from the beginning of operation, and the controller is prepared to execute shutdowns before damage can occur. This preliminary protection mechanism allows the system to deliver high startup current when needed while being ready to immediately protect against overcurrent damage if faults occur during startup.
Data Source
AI summary
A controller and method for a switched-mode power converter adaptively provides overcurrent protection by detecting a current in the power converter exceeding a current limit during substantially a minimum on time of a power switch. A count N is computed for the number of consecutive active switching cycles that a current exceeds a current limit during substantially the minimum on time of the power switch. Conduction of the power switch is inhibited for a number of cycles that is a function of the count N, which is an increasing function of N. The function of the count N is preferably the function 2N−1. The count N is reset to zero if the current in the power converter does not exceed the current limit substantially during the minimum on time of the power switch. The controller can be easily implemented with a digital integrated circuit for a wide range of applications.