SMPS Current-Limit Circuit With Temporary Overcurrent Boost
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing switched-mode power supplies lack a simple and reliable hardware structure to effectively set a comparison voltage for limiting output current to either a maximum current value or an overcurrent value.
Innovation Solution
A method and circuit arrangement using a voltage divider with a constant reference voltage and bypass switches to set the comparison voltage to either a nominal or boost value, allowing for reliable current limitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional current limiting control is used to limit output current to a predetermined maximum current value, then overcurrent protection is provided, but the control structure becomes complex and unreliable when current boosting functionality is added
Solution Approach 1:
The control structure is segmented into distinct functional units: a current limiting control unit that limits output current to a maximum current value, and a current boost control unit that temporarily increases the maximum current value to an overcurrent value. This segmentation allows each unit to perform its function independently, improving reliability while managing complexity through functional decomposition.
Solution Approach 2:
The maximum current value is made dynamic rather than fixed. The current boost control unit can temporarily adjust the maximum current value upward for a predetermined boost time when needed, allowing the system to adapt current limiting behavior based on operational requirements. This dynamic adjustment resolves the contradiction by providing flexible current control without requiring a completely complex control structure.
2Adaptability or versatility
If the maximum current value is increased to an overcurrent value for a predetermined boost time, then current boosting capability is achieved, but the control structure becomes more complex
Solution Approach 1:
The control units are pre-configured with predetermined current values (maximum current value and overcurrent value) and a predetermined boost time. This preliminary setup allows the system to quickly switch between current limiting modes without complex real-time calculations, achieving current boosting capability while keeping the control structure relatively simple through pre-programmed parameters.
Solution Approach 2:
The control units receive feedback signals from the output current to determine when to activate current limiting or current boost modes. This feedback mechanism allows automatic adjustment of the maximum current value based on actual operating conditions, providing adaptability without requiring complex manual control structures.
3Adaptability or versatility
If a complex control structure is implemented to provide both current limiting and current boost control, then functional versatility is improved, but reliability decreases
Solution Approach 1:
By segmenting the control system into separate current limiting and current boost control units, each with dedicated functionality, the system achieves functional versatility while maintaining reliability. Each unit operates independently with clear defined parameters, reducing the risk of control errors that would arise from a monolithic complex control structure.
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
Enables simple, reliable, and cost-effective control for limiting output current to either the maximum current value or the overcurrent value, preventing overloading and excessive heating.
Implementation Method 1
The output current is passed through a measuring resistor and the measuring voltage dropping across the measuring resistor is compared with a first comparison voltage
Data Source
AI summary
A method for controlling a switched-mode power supply having a current limiting control for limiting output current of the switched-mode power supply to a predetermined maximum limiting current value, and having a current boost control for setting the predetermined maximum limiting current value to a predetermined overcurrent value for a predetermined boost time. The output current is passed through a measuring resistor and the measuring voltage, dropping across the measuring resistor, is compared with a first comparison voltage as a measured value proportional to the output current. The first comparison voltage is set to a nominal comparison voltage, correlating with the maximum current value, or to a boost comparison voltage, higher than the nominal comparison voltage and correlating with the higher overcurrent value and the comparison result serves as a control signal limiting the output current to the maximum current value or the overcurrent value.