Abstract: To meet the high reliability requirement of power supply system for C919 airplane flight test equipment, a multiple protection scheme for the system is proposed basing on three-channel hierarchical power supply and redundant power supply. The multi-protection circuits have been designed and developed including over temperature protection circuit, input over-voltage and under-voltage protection circuit, output over-voltage and under-voltage protection circuit, output ripple voltage protection circuit, output overcurrent protection circuit and cooling fan stall protection circuit. The ripple protection circuit basing on infinite gain multiple negative feedback second-order high-pass filter and the cooling fan stall protection circuit basing on presettable synchronous/asynchronous down counters CD40103 are analyzed in details. Simulation and experimental tests prove that once the input voltage, output voltage and overload capacity exceed the design limits, the current scheme is capable to protect the power supply system, which is consistent to its designed performance indices.

Key words: C919 power supply system, multi-protection technique, ripple voltage protection, cooling fan stall protection