SSPC Control Circuit for Parallel Current Sharing
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Solution Overview
Problem
The implementation of solid state power controllers (SSPCs) in parallel configurations for high voltage applications in aircraft primary distribution systems faces challenges due to imperfect current sharing among SSPCs, caused by manufacturing tolerances and varying PCB resistances, resulting in lower than expected current ratings.
Innovation Solution
A control circuit that adjusts the drive voltage for a solid state switching device based on load current and current between terminals, incorporating an ON-Resistance control mechanism to regulate the ON-Resistance of each SSPC to a predetermined value, ensuring synchronized operation and improved current sharing among parallel SSPCs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple SSPCs are connected in parallel to achieve higher current ratings, then the current carrying capacity is improved, but the current sharing between SSPCs deteriorates due to manufacturing tolerances and PCB resistance variations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gate drive voltage of each solid state switching device based on its individual ON-resistance characteristics and the shared resistor value. This allows the system to compensate for manufacturing tolerances and achieve balanced current sharing among parallel SSPCs, resolving the contradiction between achieving high current ratings and maintaining precise current distribution.
2Device complexity
If SSPCs are used with fixed drive voltage, then the device complexity is reduced, but the current sharing and power dissipation performance deteriorates
Solution Approach 1:
The patent implements feedback control by measuring the voltage across a shared resistor connected to the second terminal of the solid state switching device and using this information to dynamically adjust the drive voltage. This feedback mechanism optimizes current sharing and reduces power dissipation without significantly increasing device complexity, as the control circuit uses simple voltage sensing and adjustment.
Data Source
AI summary
A control circuit is configured to apply a drive voltage to a solid state switching device comprising a first terminal (D), a second terminal (S) and a control terminal (G), the solid state switching device configured to switch, according to the drive voltage applied to the control terminal (G), between an OFF operation mode in which the second terminal (S) is electrically disconnected from an electrical supply voltage applied to the first terminal (D), and an ON operation mode in which the second terminal (S) is electrically connected to the electrical supply voltage applied to the first terminal (D) such as to connect a load circuit to the electrical supply voltage.