The ornamental design for the power adapter, as shown and described.
FIG. 1 is a perspective view of the power adapter showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is another perspective view;
FIG. 9 is an enlarged partial view thereof taken from the top of FIG. 2;
FIG. 10 is an enlarged partial view thereof taken from the bottom of FIG. 2;
FIG. 11 is an enlarged partial view thereof taken from the top of FIG. 3; and,
FIG. 12 is an enlarged partial view thereof taken from the bottom of FIG. 3.
The Dash-Dash broken line in the drawings illustrate features of the power adapter that form no part of the claimed design. The Dash-Dot-Dash broken line edge of the enlarged view and forms no part of the claimed design.