Design and Engineering of a Low Cost AC-DC MIL Grade Power Supply Unit

This paper presents the design issues and challenges in the realization of a low cost military grade 250 W AC-DC power supply unit (PSU), used for ground applications. The Power supply is designed to operate on dual power source, viz. battery and single-phase 230VAC, 50 Hz nominal. PSU is intended to deliver a power of 250 W to various communication equipment. Output voltage is tightly regulated at 48 V over a very wide line voltage and load variations. It also continues to supply power during non-availability of AC input power or in case of AC-DC converter failure, by drawing input power from the battery source. Power supply provides protection against input under voltage, over voltage, Output over voltage, Output over current, short circuit, battery input reverse polarity. It also features auto-change over from AC input to Battery supply and vice versa. The product provides a user-friendly display features through LED indications for input AC voltage presence, Battery input presence, Fault indication and output Voltage presence. The PSU housing is made out of milled aluminum, modular in construction for ease of maintenance and repair. The module is conduction cooled, with IP55 environmental protection. Operating temperature is -20°C to +55 °C. The Power supply unit has been designed to meet environmental requirements as per JSS55555, EMI/EMC as per MIL-STD-461E. The paper also provides general guidelines for meeting the quality requirements as per Mil standards.