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3.3v,1W Zener doid Regulator, need help

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Hi
I have 12 V battery
and I want to use it to drive 3.3V 30mA micro I/O's

In my circuit i have 3.3v 1W Zener diod with series rsistance Rs,I am not getting stable output When i am varying my source voltage from 3.3 to 12v

And i am using these formula to calculate Rs

Imax = Watts / voltage = 1 / 3.3v = 303mA

Rs= ( Vs - Vz ) / Imax = (12 - 3.3) / 303mA = 28 ohm


can any body help me...
 
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The minimum discharge voltage for 12 V battery shoudln't be below about 10 V, otherwise it gots permanently degraded. With 10 to 14 V input coltage, a zener regulator should manage it.

Of course, you won't get perfect regulation with a zener diode even for a restricted voltage range. It's also not reasonable to apply 300 mA to the zener diode, I think. It would mean less than 10 % efficiency of your "regulator" circuit. In any case, an IC voltage regulator should be preferred, consuming nearly no excess power.
 
Thanks..! But i am using Variable source input(Vs) from 0-12v.
 

But i am using Variable source input(Vs) from 0-12v.
Click to expand...
Yes, obviously regulation can't be achieved over this input voltage range. :smile:
 

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