suggestions for handling dissipated heat are summarized, below:

(1)

Ambient Air Cooling

For miniature and high power density converters, free air cooling is recommended, mainly due

to cost and space concerns.

♦ Heat dissipates to the ambient air through the converter case or exposed surfaces. Heat

may also dissipate to ambient air if there is a gap between the converter and the PCB.

♦ Heat dissipates from the converter case and exposed surfaces to PCB by radiation.

♦ Heat conducts through terminals (pins) to PCB.

In such applications, please pay particular attention to:

A. Air Flow - Because the heat dissipation is mainly through convection and radiation, the

converter needs an environment with good air flow.

It may be helpful to design heat

dissipation venting holes throughout the end product, near the converter

’s location. For

best convection cooling, ensure that air flow is not blocked by large components

B. Layout of Heat Generating Components - In most applications, the AC/DC converter is

usually not the only heat generating component.

It is recommended to keep a good

distance between each heat generating component to minimize heat dissipating clusters.

C. PCB Design - The PCB, which the power converter is assembled on, is not only a base to

mount the converter, but also acts as a heat sink for it, therefore heat dissipation should be

considered in PCB layout.

We recommend extended the area of the main copper loop

and decrease the component density on the PCB to improve the ambient environment.

(2) Heat Sinks

When free air convection is not sufficient enough, we recommend the use of a heat sink for

further cooling. As the converters are filled with heat conductive silicon or epoxy, the heat

distribution in converter is even and it radiates from the converter to the air.

The efficiency of

this convection is dependent on the size of the surface area of the converter.

The use of heat

sinks is a practical method to add surface area and improve the convection.

There are many

kinds of heat sinks available in the market.

MORNSUN recommends considering the following

factors in selecting a heat sink: