Investigation and Implementation of Backup Supply Power Lines

This thesis aims to determine the most suitable topology by comparing the advantages of input power redundancy architectures used in avionics units for military aircraft (HA). Redundancy architectures for input power of avionics units were investigated, analyzed using LTSpice and the PCB design was optimized according to the analysis results. Then, based on the experimental and simulation results, the most suitable redundancy architectures were determined according to the criticality levels of avionics units and model validation studies were conducted. Both passive (e.g., resistors and diodes) and active redundancy structures (e.g., Switching Mode Power Supplies (SMPS), Low Dropout Regulators (LDOs) and MOSFETs) were investigated. Integrated components were selected for circuit design and analysis by complying with the standard test procedures outlined in MIL-STD-810, MIL-STD-461 and MIL-STD-704. Circuit diagrams were designed using LTSpice and Ansys SIWave Simulation software and thermal, direct current (DC) and frequency analyses were performed. Efficiency and output voltage fluctuations were evaluated to compare different redundancy architectures. The layout design was optimized using Altium software, which included current and power density evaluations. After the PCB (Printed Circuit Board) design was completed, production documentation was prepared, manufacturers were contacted and PCBs were manufactured. The manufactured PCBs went through typesetting and quality control procedures. A special test setup was created for the initial power test and a test procedure was developed to perform functionality, thermal and power tests using appropriate test equipment including oscilloscopes, multimeters, environmental test chambers and load banks. Environmental-mental tests were conducted in accordance with MIL-STD-810 standards to simulate operating conditions at varying altitudes and temperatures, including thermal shock, cold start performance, minimum-maximum operating conditions and long-term operational stability evaluations.