What kind of efficiency rating does this power supply have, and does it include any protective features like over-voltage or short-circuit protection?

The power supply module has over-current protection and short circuit protection, ensuring safety during use.

Does this power supply module support dual voltage input, or is it strictly DC 12V input?

The power supply module is strictly DC 12V input.

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300W Power Supply Module, PC PSU DC 12V Input 300W Computer Power Supply Module with 24Pin Connect/AUX/SATA Cable for Mini-itx and 1u Cases.

Suitable ForProfessional power supply module, the power supply module is suitable for the mini-ITX and 1U cases.
FeaturesThe industrial solid capacitor allows super performance and high-temperature proof, stable and reliability. Quietly work without noise, do not disturb you.
Plug and Play300W Output and 12V DC Input and it must be accompanied by the power adapter. 24Pin ATX connector for perfect connection and suitability, plug directly and play.
FeaturesPC power supply is processed by professional manufacturing, It adopts a portable and compact design, saves space, durable to use.
Full ProtectionPower supply module 12V has Over-current protection and short circuit protection, safe to use.