Power Source Protection Circuit with Automatic Short-Circuit Recovery
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Solution Overview
Problem
Existing DC power sources face damage from overheating due to excessive current during short-circuits, and current protection methods often fail to provide continuous protection, leading to component damage and require power cycling for recovery.
Innovation Solution
A power-source protection circuit with a control switch and pass switch arrangement that actively controls current output by turning off in response to short-circuits, using a thermistor and resistors to manage voltage and current, allowing for automatic recovery without latching and minimizing power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PTC circuit element is used to limit current during short-circuit, then the power source is protected from damage, but the protection is not continuous and requires power cycling for recovery
Solution Approach 1:
The patent implements a feedback mechanism where the control switch continuously monitors the output terminals for short-circuit conditions and automatically adjusts the pass switch state accordingly. When a short-circuit is detected, the control switch turns off the pass switch to limit current, and when the short-circuit is removed, the pass switch automatically turns on again, providing continuous protection without requiring power cycling.
2Difficulty of detecting and measuring
If current sensing with a low-value resistor is used to detect short-circuits, then short-circuit detection is achieved, but the protection is not continuous and does not provide automatic recovery
Solution Approach 1:
The patent ensures continuous protection by maintaining an active control switch that continuously monitors the output terminals for short-circuit conditions. Unlike passive detection methods, the control switch remains engaged throughout operation, providing uninterrupted surveillance and immediate response to short-circuit events, enabling continuous protection with automatic recovery capability.
3Temperature
If thermal tripping is used to respond to short-circuits, then component overheating is prevented, but the protection mechanism latches and requires power cycling to reset
Solution Approach 1:
The patent inverts the conventional thermal tripping approach by using a control switch that actively responds to short-circuit conditions rather than passively reacting to temperature rise. Instead of thermal expansion triggering a mechanical trip that latches, the control switch electronically detects short-circuits and automatically controls the pass switch to turn off, providing overheating prevention with automatic recovery without latching.
4Power
If driving transistors are operated close to maximum collector current to meet short-circuit demand, then current capability is improved, but overheating and component damage risk increases
Solution Approach 1:
The patent applies preliminary anti-action by proactively detecting short-circuit conditions through the control switch before excessive current can cause overheating or component damage. Rather than relying on transistors to handle maximum current during short-circuits, the control switch preemptively turns off the pass switch when a short-circuit is detected, preventing the harmful current surge before it occurs and eliminating the need to operate transistors near their maximum ratings.
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 provides continuous short-circuit protection with current fold-back, preventing overheating and allowing for automatic recovery without power cycling, ensuring the DC power source operates safely and efficiently.
Implementation Method 1
Inline positive temperature coefficient (PTC) circuit elements have been used to limit currents in known power sources. The PTC circuit element, typically a thermistor, can be placed in series with the output of a power source. A PTC thermistor increases in resistance as temperature increases
Implementation Method 2
The control switch is arranged to switch on when the power source is started and the control switch is arranged to switch off when the output terminals are short-circuited
Data Source
AI summary
A power-source protection circuit includes a power source including a first voltage rail and a second voltage rail, a pass switch connected across the first voltage rail and a third voltage rail, a control switch connected to the second voltage rail and a control terminal of the pass switch, such that the pass switch turns on in response to the control switch turning on and the pass switch turns off in response to the control switch turning off, and output terminals connected to the third voltage rail and the second voltage rail. The control switch is arranged to switch on when the power source is started and the control switch is arranged to switch off when the output terminals are short-circuited and to switch on when the short-circuit is removed.