Well not really - regulation is not needed.  The additional diode
supplies the reverse polarity protection, and since it is not a shunt
regulator, there is NO power loss if you put the micro into sleep mode -
just what the micro would draw.  This method is much more efficient and
will handle varying loads without trouble.  To do so with a shunt
regulator, you will waste most of your power heating up a series
resistor.  If you want that, you can use the shunt circuit as a hand
warmer too!

- Mike


David VanHorn wrote:

>At 08:01 AM 6/30/2004 -0400, Mr MCU wrote:
>
>
>
>>Seem like everyone forgets that zener diodes actually subtract their
>>voltage if placed in series.  e.g. I would use a 1N4730A in series with
>>the 9V.  That would give you 9V - 3.9V = 5.1V ... perfect supply up to
>>1W!  Although it does not regulate, you really don't need regulation in
>>your example as I see it.  I would also use a 1N400x series diode for
>>reverse polarity protection - if so just use a 1N4728A to make up the
>>additional voltage drop.
>>
>>
>
>So you've removed both regulation, and reverse polarity protection as features of this design?
>
>I like the parallel version better.
>
>--
>http://www.piclist.com hint: PICList Posts must start with ONE topic:
>[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads
>
>
>
>

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads