Which device is used to supply clean DC power to avionics from the 28V DC bus, typically with filtering?

Which device is used to supply clean DC power to avionics from the 28V DC bus, typically with filtering?

• A. A battery-powered regulator that feeds avionics directly.
• B. An inverter.
• C. A DC-DC converter without filtering.
• D. A transformer rectifier unit (TRU) or DC-DC converter with filtering to provide clean DC power.

Answer: (D)

Delivering clean, stable DC to avionics requires removing ripple and smoothing transients from the power system. The device that does this is a transformer rectifier unit (TRU) or a DC-DC converter configured with filtering and regulation. The TRU converts incoming power to DC and, with filtering, provides a smooth voltage suitable for sensitive avionics. A DC-DC converter can likewise regulate the voltage and include filtering to reduce noise. This combination ensures the avionics see a low-noise, well-regulated DC supply from the 28V DC bus. The other options don’t meet that requirement: a battery-powered regulator feeding avionics directly wouldn’t consistently filter or regulate the bus and could struggle with load changes; an inverter produces AC rather than the required DC; and a DC-DC converter without filtering would still allow ripple and noise to pass to the avionics.

Delivering clean, stable DC to avionics requires removing ripple and smoothing transients from the power system. The device that does this is a transformer rectifier unit (TRU) or a DC-DC converter configured with filtering and regulation. The TRU converts incoming power to DC and, with filtering, provides a smooth voltage suitable for sensitive avionics. A DC-DC converter can likewise regulate the voltage and include filtering to reduce noise. This combination ensures the avionics see a low-noise, well-regulated DC supply from the 28V DC bus.

The other options don’t meet that requirement: a battery-powered regulator feeding avionics directly wouldn’t consistently filter or regulate the bus and could struggle with load changes; an inverter produces AC rather than the required DC; and a DC-DC converter without filtering would still allow ripple and noise to pass to the avionics.