SMPS Fold-Back Circuit for Thermal Runaway Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switched mode power supplies face challenges in maintaining accurate current sensing due to increased parasitic body diode current at high temperatures, leading to thermal run-away and potential device failure, as the ability to regulate inductor current is compromised.
Innovation Solution
A fold-back circuit and controller system that monitors the low-side transistor voltage to detect significant parasitic body diode current, generating a fold-back signal to adjust the switching frequency of the transistors, thereby preventing thermal run-away by ensuring the inductor current reaches the valley current limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power converter operates at high temperatures, then the power output can be maintained, but parasitic body diode current increases causing thermal run-away
Solution Approach 1:
The patent implements a feedback mechanism that monitors the low-side transistor voltage to detect significant parasitic body diode current. When thermal run-away is detected, the system generates a fold-back signal that adjusts the switching frequency of the transistors, creating a closed-loop control system that maintains thermal stability while preserving power output capability.
Solution Approach 2:
The system dynamically adjusts the switching frequency of the transistors based on real-time detection of parasitic body diode current. By varying the switching frequency in response to temperature conditions, the system adapts its operation to prevent thermal run-away while maintaining optimal power conversion efficiency across different operating conditions.
2Productivity
If the switching frequency is increased to maintain power output, then power delivery improves, but parasitic body diode current increases leading to thermal run-away
Solution Approach 1:
The feedback mechanism continuously monitors the low-side transistor voltage to detect significant parasitic body diode current. When thermal run-away is detected, the system generates a fold-back signal that adjusts the switching frequency of the transistors, creating a closed-loop control system that maintains thermal stability while preserving power output capability.
Solution Approach 2:
The system takes preliminary anti-action by detecting the onset of significant parasitic body diode current before thermal run-away fully develops. By generating a fold-back signal that adjusts switching frequency in advance, the system prevents the harmful effect from escalating while maintaining normal power delivery operation.
3Power
If the inductor current regulation is relaxed to allow higher current flow, then power output increases, but the ability to prevent thermal run-away is compromised
Solution Approach 1:
The feedback mechanism continuously monitors the low-side transistor voltage to detect significant parasitic body diode current. When thermal run-away is detected, the system generates a fold-back signal that adjusts the switching frequency of the transistors, creating a closed-loop control system that maintains thermal stability while preserving power output capability.
Data Source
AI summary
A system includes a current mirror coupled to a first transistor, the first transistor includes a first gate, a first current terminal, and a second current terminal, a controller coupled to the current mirror and a converter, the controller is to output a delayed signal for a second transistor, the second transistor being a part of the converter, and a source voltage coupled to the current mirror.