EP11 datasheet(38/46 Pages) POWERINT

38 / 46 page

EPR-00011 - 70 W Adapter

22-Jan-01

Page 38 of 46

Power Integrations Inc

Tel: +1 408 414 9200 Fax: +1 408 414 9201

www: http://www.powerint.com

13.1 Efficiency:

Items to consider for maximising efficiency:

• Transformer:

Minimise leakage inductance and conduction losses

Use highest possible duty factor and operate in continuous mode for reduced

peak currents (the copper window of the transformer bobbin may limit this)

• Output Diodes:

Use low forward drop, higher current rated diodes

Use Schottky-barrier diodes when possible

Parallel diodes to reduce forward drop. Take care to make sure that paralleled

diodes share current equally (the EP11 uses dual secondary windings and a

common heat sink to achieve this).

Allow diodes to run as hot as possible (consistent with maximum board

temperature and component life constraints). This will minimize the forward

drop.

• Power Switch (TOPSwitch-GX):

Use a lower RDS(ON) part (the TOP249 used in the EP11 is capable of over

250 Watts in an open frame design)

Use the highest possible maximum operating duty cycle to reduce conduction

losses (this must be balanced against increased leakage and transformer

losses).

• Line Filter:

-Use as few turns as possible for inductor windings

Increase capacitor value (rather than inductor value) where practical, to

minimize differential choke size down.

13.2 Heat Sinking:

Heat sinking power devices such as the TOPSwitch-GX, input diodes, and output diodes

will be more critical in an adapter application than in open frame designs. This is largely

because all of the generated heat must be CONDUCTED through the enclosure walls.

The heat sinks used in EP11 are made of copper. Copper has high thermal conductivity

(~3.94 W/cm

oC), but it is heavy. Aluminum may be used instead. It is lighter, but it has

somewhat lower thermal conductivity (~2.18 W/cm

oC). The net thermal conductivity

from the heat generating components to the outside air of the adapter’s enclosure

together with the overall efficiency of the supply determines the maximum continuous

power output for a given environment.

EP11 Datasheet(PDF) 38 Page - Power Integrations, Inc.

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