Regulator Current Limiting With Foldback for Low-Resistance Loads
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Solution Overview
Problem
Regulator circuitry faces damage due to the need to supply high currents when the resistance of the load is low, as it attempts to maintain a fixed output voltage, leading to potential component damage.
Innovation Solution
Incorporating current monitoring circuitry with current sense and current limit components that set first and second current limits based on the output voltage of the regulator circuitry, preventing excessive current flow by using parallel current paths and foldback mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If regulator circuitry supplies high current to maintain fixed output voltage when load resistance is low, then output voltage stability is improved, but risk of component damage increases
Solution Approach 1:
The current limit circuitry is configured to limit the output current before excessive current can reach levels that would damage components. By proactively monitoring and limiting current through the current sense circuitry and transistor control, the system prevents harmful current levels from occurring in the first place, rather than reacting after damage has occurred.
Solution Approach 2:
The current sense circuitry continuously monitors the output current and feeds this information back to the current limit circuitry. When the monitored current approaches the predetermined limit, the feedback mechanism triggers the transistor to reduce the output current, thereby maintaining voltage stability while preventing component damage through real-time current regulation.
2Stability of the object's composition
If regulator circuitry increases current supply to maintain fixed output voltage, then voltage regulation performance is improved, but current consumption increases
Solution Approach 1:
The system dynamically adjusts the output current based on actual load requirements through the interaction of the regulator circuitry and current limit circuitry. Rather than supplying maximum current continuously, the system modulates current supply to match the load's instantaneous needs while maintaining voltage stability, thereby reducing unnecessary current consumption and energy waste.
Solution Approach 2:
The current limit circuitry changes the current parameter dynamically by adjusting the transistor's conduction state based on feedback from the current sense circuitry. This parameter modulation allows the system to maintain voltage regulation performance while optimizing current consumption to match actual load demands rather than operating at fixed maximum current.
3Reliability
If current limit circuitry is added to prevent excessive current, then component protection is improved, but device complexity increases
Solution Approach 1:
The current limit circuitry is merged with the regulator circuitry by sharing common components such as the transistor and power supply connections. The current sense circuitry utilizes the existing output current path, and the transistor serves both regulation and current limiting functions. This merging approach provides component protection while minimizing the addition of separate discrete components, thereby reducing overall circuit complexity.
Data Source
AI summary
An example apparatus includes: regulator circuitry having a first terminal and a second terminal; current sense circuitry having a first terminal, a second terminal, and a third terminal; the first terminal of the current sense circuitry coupled to the first terminal of the regulator circuitry, the second terminal of the current sense circuitry coupled to the second terminal of the regulator circuitry; and current limit circuitry including: a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal coupled to the third terminal of the current sense circuitry, the control terminal coupled to the second terminal of the regulator circuitry; and current source circuitry having a terminal coupled to the second current terminal of the transistor.