Computer Power Supply (RELIABLE × 2025)

is used when referring to any non-specific unit or introducing the concept for the first time (e.g., "A computer power supply converts AC to DC").

is used when referring to a specific unit already mentioned or the unique one inside a particular machine (e.g., "The computer power supply is found in the corner of the case"). What is a Computer Power Supply? COMPUTER POWER SUPPLY

The proper article for the phrase depends on the context of your sentence. In general English usage: is used when referring to any non-specific unit