Power Bus Foldback Circuit for Temperature-Compensated Short Protection
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Solution Overview
Problem
Existing foldback circuits in power supply buses fail to adequately reduce power dissipation and prevent thermal shutdown during short circuit conditions, particularly due to the lack of effective current limiting and temperature compensation, leading to potential overheating and equipment failure.
Innovation Solution
A foldback circuit design incorporating a current loop to bias a series pass element during idle conditions, a current limiter to provide constant current compensation for ambient temperature variations, and a resistor-capacitor-diode loop to limit current during short circuits, reducing power dissipation and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional linear regulator is used to maintain constant current during short circuit conditions, then the current remains stable, but power dissipation increases causing thermal shutdown
Solution Approach 1:
The patent implements dynamic current limiting where the current limit is adjusted based on temperature conditions. During cold start or low temperature operation, a higher current limit is permitted. As temperature increases, the current limit is dynamically reduced to prevent excessive power dissipation and thermal shutdown, allowing continuous operation across varying thermal conditions
Solution Approach 2:
The patent changes the current parameter dynamically based on temperature. The current limiter modifies the current limit parameter in response to temperature sensor feedback, transitioning from a fixed current limit to a temperature-dependent variable current limit, thereby optimizing power dissipation under different thermal conditions
2Loss of energy
If a foldback circuit reduces current during short circuits, then power dissipation decreases, but existing circuits lack adequate temperature compensation leading to insufficient protection
Solution Approach 1:
The patent incorporates temperature feedback through a temperature sensor that continuously monitors the thermal condition and feeds this information to the current limiter. This closed-loop feedback mechanism enables the current limit to be automatically adjusted based on real-time temperature measurements, ensuring effective thermal protection
Solution Approach 2:
The patent introduces a temperature sensor as an intermediary between the thermal condition and the current limiting mechanism. This intermediary component translates temperature into an electrical signal that the current limiter can process, enabling indirect but effective thermal compensation and protection
3Reliability
If larger components are used to handle power dissipation during short circuits, then thermal protection improves, but device footprint increases
Solution Approach 1:
The patent changes the operational parameters of existing components dynamically based on temperature conditions, rather than using oversized components designed for worst-case scenarios. By adjusting the current limit parameter in response to temperature, the system achieves adequate thermal protection with standard-sized components, reducing overall device footprint
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
The proposed foldback circuit effectively reduces power dissipation and heat during short circuits, preventing thermal shutdown and allowing continuous operation across a wide temperature range with a smaller component footprint compared to traditional linear regulators.
Implementation Method 1
a current limiter to provide a constant current through the series pass element and compensate for ambient temperature variation to limit the current through the series pass element
Implementation Method 2
The proposed foldback circuit effectively reduces power dissipation and heat during short circuits, preventing thermal shutdown
Data Source
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AI summary
A foldback circuit of a power supply bus is described herein. One device includes a current loop to bias a series pass element during a bus idle condition of the power supply bus, and a current limiter to provide a constant current through the series pass element and compensate for ambient temperature variation to limit the current through the series pass element, where the foldback circuit is to limit the current through the series pass element in response to a short circuit condition of the power supply bus.