Connecting Internal SATA HDD to eSATA

I have these 3 things:

(1) An internal 3.5 SATA HDD.
(2) An independent power supply that provides a Molex style connector (i.e. 5V and 12V power) and an adapter to convert it into SATA (except that it cannot provide the 3.3V found in a SATA power connector).
(3) My PC already provides an eSATA port.

My question now is instead of purchasing an external HDD enclosure, is it possible to use my existing internal SATA 3.5 HDD, powered by my independent power supply, on my PC's eSATA port directly?

I have the impression that the external HDD enclosure is nothing more than a power supply plus protection. Is there any extra circuit required to convert from SATA->eSATA apart from a cable?

Solution 1:

Yes, it's possible to use an internal SATA 3.5 HDD powered by your independent power supply. There is no extra circuitry as far as I know, and the only thing you need is the SATA to eSATA cable.

If you have an eSATAp port, you can just use a compatible cable and it will provide power directly from the port.

Here is a picture of an eSATAp to SATA cable which provides direct power from the port.