Flying DC-DC Converter Thermal Protection via RMS Current Estimation
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Solution Overview
Problem
Conventional flying DC-to-DC converters face challenges in controlling the voltage of a flying capacitor, which deteriorates with increasing temperature, leading to potential failures like short-circuits and disconnections, and require additional cost for temperature sensor circuits to prevent overheating.
Innovation Solution
A DC-to-DC converter with a controller that estimates the temperature of the flying capacitor by calculating the root mean square (RMS) current based on the inductor current and switching duty, allowing for de-rating without the need for a temperature sensor, thereby preventing overheating and ensuring system reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature sensor is attached to the capacitor to prevent overheating, then the reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The controller utilizes existing internal resources (detection current and control duty) to estimate the capacitor temperature through RMS current calculation, eliminating the need for external temperature sensors and associated circuits while maintaining reliable overheating protection
Solution Approach 2:
The patent introduces an intermediary calculation method where the controller estimates temperature indirectly through RMS current derived from detection current and control duty, rather than directly measuring temperature with a sensor, thus avoiding additional hardware complexity
2Weight of moving object
If the inductance of the inductor is reduced to decrease size and weight, then the weight is improved, but the voltage applied to the inductor increases causing capacitor overheating
Solution Approach 1:
The controller continuously monitors detection current and control duty to calculate RMS current, which serves as feedback to estimate capacitor temperature and adjust operation accordingly, preventing overheating even when inductor inductance is reduced for weight savings
Solution Approach 2:
The patent changes the operational parameters (control duty and detection current) to maintain safe capacitor temperature levels, allowing the inductor to be designed with lower inductance for reduced weight while the controller adjusts parameters to prevent excessive voltage stress on the capacitor
Data Source
AI summary
A flying DC-to-DC converter has a capacitor protection function of preventing a flying capacitor from overheating. The flying DC-to-DC converter estimates the temperature of a capacitor on the basis of a switching duty and an inductor current determined according to a result of comparison between an output voltage and a voltage instruction value, and determines whether to perform de-rating.