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Thread: 7805 pin compatible switching regulator ?
www.piclist.com/techref/power/priswitch.htm?key=switching
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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.
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