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Thread: 7805 pin compatible switching regulator ?
face BY : David VanHorn email (remove spam text)

At 04:10 PM 11/13/01 -0200, Marcelo Yamamoto wrote:
>If I remember correctly 78xx series have a thermal shutdown. They are rated
>for 1.5A. At this current and 24V supplying it, you will have:
>Power= 1.5x(24-5)= 28.5W
>Ensure you have a BIG heatsink or proper ventilation.
>Use a linear series regulator to drop the voltage to something around 8V and
>put the regulator after it. It will be more reliable than a simple
>transistor and a zener in a series regulator.

No matter how you slice it, it's still bologna.

If the output is 1A, then he has to get rid of 19W of heat.
Using a pre-reg just moves the heat to a different place.
This is why we use switchers. The waste will be more in the range of 0.5W.

Input power will drop from 24W to something like 5.5W.
Dave's Engineering Page: http://www.dvanhorn.org

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In reply to: <002b01c16c6e$8ceb0760$5400a8c0@ns.com.br>
See also: www.piclist.com/techref/power/priswitch.htm?key=switching
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Subject (change) 7805 pin compatible switching regulator ?

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