It's a My Passport model...
I have two, with different capacities.
I use other USB portable drives at work, and don't usually have problems with power. I use a couple of different LaCie, and another one that I have used for several years, something generic. That one needs external power.
My point is, there's other portable drive cases out there that work without needing the extra power, but some do need that. My experience may not be shared by others here.