Power Supply Selector Transistor Inrush Current Protection
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Solution Overview
Problem
Existing power supply selectors have a large footprint due to the use of multiple comparators for inrush current protection, which increases space requirements and power losses, while also consuming static current during normal operation.
Innovation Solution
A power supply selector design that replaces comparators with a pair of transistors, where each power input node is coupled to a switch with different on-resistances, allowing for inrush current protection through voltage comparison using the gate-source characteristic of transistors, reducing footprint and power losses, and eliminating static current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If window comparators are used for inrush current protection, then overcurrent protection is provided, but footprint and power losses increase
Solution Approach 1:
The patent combines the functions of voltage comparison and inrush current protection into a single integrated circuit block, merging the window comparator functionality with the power supply selector to reduce footprint while maintaining protection capabilities
Solution Approach 2:
The integrated circuit performs multiple functions simultaneously: voltage comparison, inrush current limiting, and power source selection, allowing a single component to replace what would traditionally require separate comparators and protection circuits
2Reliability
If window comparators are used for inrush current protection, then overcurrent protection is provided, but power losses increase
Solution Approach 1:
The circuit uses periodic sampling of voltage differences through the transistor pair, rather than continuous operation of comparators, reducing power consumption while maintaining effective protection during inrush events
Solution Approach 2:
The transistor-based voltage comparison mechanism uses the inherent electrical characteristics of the transistors themselves to perform the comparison function without requiring external power-intensive comparator circuits
3Loss of energy
If first switch with low on-resistance is closed to minimize losses, then power efficiency is improved, but inrush current increases
Solution Approach 1:
The circuit performs preliminary voltage comparison before closing the low-resistance switch, detecting potential inrush conditions in advance and preventing switch closure when inrush current would occur
Solution Approach 2:
The transistor pair continuously monitors the voltage difference between input and output, providing feedback control that dynamically manages switch operation to balance power efficiency and inrush current protection
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 solution significantly reduces the footprint of inrush current protection circuits, minimizes power losses, and ensures zero static power consumption by using transistors to sense voltage differences, providing fast and reliable overcurrent protection.
Implementation Method 1
voltage comparison using the gate-source characteristic of transistors
Data Source
AI summary
A method for minimizing an inrush current in a power supply selector and a power supply selector system is provided. The power supply selector includes a plurality of power input nodes, a power output node, a first transistor and a second transistor. Each of the power input nodes may be coupled to a first switch having a first on-resistance and to a second switch having a second on-resistance. The second on-resistance is greater than the first on-resistance. The first switch and the second switch are preferably coupled in parallel. The power supply selector may be configured to couple a selected one of the power input nodes to the source of the first transistor and to the gate of the second transistor so as to sense a sense voltage at the selected power input node.