EPR-00011 - 70 W Adapter 22-Jan-01
Page 20 of 46
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9 Thermal Performance
The EP11 printed circuit board was designed to allow testing within the enclosure of a
commercial laptop computer adapter. This adapter has an enclosure made of plastic and
incorporates copper heat spreaders with a plastic shroud to insulate them from the board
components. See Figure 12.
Thermal testing was done in still air. This was achieved by placing the board into a
sealed cardboard box which is 11” long, 8.5” wide and 7” high. The adapter was placed
on a 6” × 4” piece of single sided copper clad board (copper side down) which was taped
to the bottom center of the box. The box had small openings for the thermal couple wires
and the input and output cables. It was taped shut and placed in an environmental
chamber. The measurements were made by attaching “T” type thermocouples to the
following components using a thermally conductive glue (Loctite 384) with the wires
dressed out of the enclosure in alignment with the output cable.
1 TOP249 tab: The metal tab of the TO-220 package of the TOP249Y.
2
Bridge: The junction of the plastic input rectifier bridge’s package (BR1) and the
copper heat sink HS1.
3CMChoke: The coil of the input choke L3.
4Bulk/ X cap: The narrow space between C5 and C7.
5 Opto: The top of the package of U2.
6Enc.Top: The outside of the enclosure centered on the top surface.
7Enc.Side: The outside of the enclosure on its side (near the fuse F1).
8 Snubber: The package of the zener diode D2.
9 Transformer: The top of the windings nearest the center.
10 Output Diode 1: The metal tab of the rectifier D5.
11 Output Diode 2: The metal tab of the rectifier D1.
12
Ambient 1: This is suspended in the air approximately 3.5” above the center of the
enclosure within the cardboard box.
13
Ambient 2: This is suspended in the air approximately 1” above and 0.5” to the side of
the enclosure about 1” from the input cable end.
