Patent ID: 7218537

Claim:
An in-rush current limiter for limiting in-rush current from a power supply bus to an avionics unit during system startup, the in-rush current limiter comprising: a switching circuit, the switching circuit interrupting a main current path from the power supply bus to the avionics unit during system startup, the switching circuit comprising a switching transistor in the main current path, the switching transistor controlled by a clamping integrated circuit to limit voltage at the avionics unit; a charging circuit, the charging circuit connecting an alternative current path from the power supply bus to the avionics unit during system startup, the charging circuit including a resistive element to limit current in the power supply bus to an acceptable level during system startup; and a limiter controller, the limiter controller sensing system startup and controlling the charging circuit and the switching circuit such that the charging circuit interrupts the alternative current path to prevent current flow through the alternative current path and the switching circuit connects the main current path through the switching transistor when the avionics unit has been charged to a defined level.