Sense Switch Parallel Load Switch Over-Current Protection
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Solution Overview
Problem
Existing electronic systems with switches face damage due to over-current conditions, which can occur from short circuits, leading to overheating and potential damage to components connected through the switch.
Innovation Solution
A circuit and method involving a sense switch in parallel with the load switch, allowing the sense switch to remain on during fault conditions to monitor and allow a 'bleed current' while the load switch is turned off, enabling rapid detection of when the fault has passed and safe reactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a load switch is used to conduct current in electronic systems, then the system can operate normally, but the switch is vulnerable to damage from over-current conditions
Solution Approach 1:
A sense switch is introduced as an intermediary component in parallel with the load switch. The sense switch has different characteristics (smaller size, different current handling) than the load switch, allowing it to safely conduct bleed current during fault conditions without suffering the same damage risks as the load switch. This intermediary component enables fault detection and system protection while the load switch remains protected from direct exposure to harmful over-current conditions.
2Reliability
If the load switch is turned off during fault conditions, then the switch is protected from damage, but the system cannot rapidly detect when the fault has passed
Solution Approach 1:
The switching function is segmented into two separate switches: the load switch and the sense switch. The load switch handles the main current and can be turned off to protect against faults, while the sense switch remains in parallel and continues to conduct bleed current. This segmentation allows the sense switch to remain active and detect fault conditions without the load switch being exposed to damaging currents, enabling rapid fault detection while maintaining switch protection.
Solution Approach 2:
The sense switch provides continuous feedback about the fault condition by conducting bleed current through the fault path. A comparison circuit monitors the voltage across the sense switch and compares it to a reference value, providing real-time feedback about the presence or absence of faults. This feedback mechanism enables rapid detection of when faults have passed without requiring the load switch to remain in a blind off state, reducing the loss of time while maintaining protection.
3Difficulty of detecting and measuring
If a sense switch is added in parallel with the load switch, then fault detection capability is improved, but the device complexity increases
Solution Approach 1:
The sense switch acts as a simplified copy or model of the load switch, placed in parallel to replicate the fault detection function. Rather than adding complex monitoring circuits or sensors, a simpler switch structure is copied and used specifically for sensing purposes. The sense switch has smaller size and different characteristics optimized for detection rather than current handling, providing fault detection capability while adding minimal complexity compared to the main load switch.
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
This solution effectively protects the load switch and connected components by allowing safe current passage during faults, enabling rapid determination of when the fault has been addressed and safe reactivation of the load switch.
Implementation Method 1
a sense switch in parallel with the load switch and configured to switchably conduct current between the first and second terminals of the load switch
Data Source
AI summary
Circuits and methods for protecting against over-current conditions of switches are described. Over-current conditions can damage switches and the circuits they connect. Some embodiments of the present application provide a sense switch in parallel with the load switch. The sense switch is smaller than the load switch, and is used to sense an over-current condition of the load switch. The sense switch can remain on even when the load switch is turned off in response to detection of an over-current condition.