Solid State Power Controller Lightning Protection via Current Path Selection
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Solution Overview
Problem
Solid state power controllers in vehicles lack effective lightning protection, as composite materials used in aircraft do not attenuate lightning currents like aluminum, leading to increased voltage surges that can damage FETs, and existing solutions are costly, bulky, and reduce reliability.
Innovation Solution
A solid state power controller system with a microcontroller and modules that selectively allow transient currents through a switch based on thresholds, automatically resetting the switch and using voltage clamp circuitry to protect against lightning-induced over-voltages, thereby reducing damage from transient currents without significant cost or packaging penalties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If composite materials are used instead of aluminum for weight and strength benefits, then weight and strength are improved, but lightning attenuation capability deteriorates
Solution Approach 1:
The patent introduces a current path selector as an intermediary device that mediates between the lightning strike and the FET. This selector directs transient currents away from the FET through alternative paths, protecting the FET from voltage damage while allowing the aircraft to use lightweight composite materials. The intermediary component resolves the contradiction by adding protection functionality without requiring heavy aluminum skin.
Solution Approach 2:
The patent replaces the mechanical/physical lightning protection mechanism (aluminum skin attenuation) with an electronic control system. Instead of relying on the physical properties of aluminum to attenuate lightning, the system uses electronic detection and control circuitry to identify transient currents and redirect them through a current path selector, substituting electronic intelligence for mechanical protection.
2Reliability
If an over-voltage clamp is used to protect the FET from exceeding its maximum voltage capability, then FET voltage protection is improved, but power dissipation increases
Solution Approach 1:
The patent extracts the voltage clamping function from the main current path and creates a separate transient current path. Instead of forcing all current through the FET and relying on the FET's inherent voltage clamping (which causes power dissipation), the system extracts transient currents and directs them through an alternative path that bypasses the FET, eliminating the need for continuous voltage clamping and reducing power dissipation.
Solution Approach 2:
The system performs preliminary detection of transient currents and activates the current path selector before the voltage surge can damage the FET. By detecting the transient condition early and preemptively redirecting the current through an alternative path, the system prevents the need for reactive over-voltage clamping, thereby avoiding the associated power dissipation penalties.
3Object-affected harmful factors
If high voltage FETs are used to block the voltage in the off state, then voltage blocking capability is improved, but cost and packaging size increase
Solution Approach 1:
Instead of making the FET itself capable of blocking high voltages (which would require larger, more expensive high-voltage FETs), the patent inverts the approach by making the current path selectable. The system uses standard-voltage FETs combined with a controllable current path selector that redirects transient currents away from the FET, achieving high-voltage protection through path selection rather than through FET voltage rating.
4Reliability
If transient suppression devices are placed across the FETs or more parallel FETs are added, then lightning protection is improved, but cost and packaging density worsen
Solution Approach 1:
The current path selector serves multiple functions: it protects against lightning-induced transients, enables normal FET operation during non-transient conditions, and provides a controllable alternative path for transient currents. This multi-functional component achieves lightning protection without requiring additional dedicated suppression devices or parallel FETs, maintaining packaging density while improving reliability.
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 system effectively protects the SSPC from lightning-induced damage by managing transient currents, maintaining reliability and low cost, and reducing packaging density, allowing it to handle higher lightning energy without the need for expensive high-voltage FETs or additional hardware.
Implementation Method 1
An over-voltage clamp can be used to protect the FET from exceeding its maximum voltage capability by placing the FET into a linear region.
Implementation Method 2
to protect the loads, a transient voltage suppression is often used by the load to shunt or divert the lightning current.
Data Source
AI summary
A method of controlling a solid state power controller includes selectively allowing a transient current through a solid state power control switch in response to the transient current exceeding at least one threshold.