Re: [CAD_CAM_EDM_DRO] Re: Question on Power Supply - regulated notes

caudlet wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Codesuidae <codesuidae@c...>
>wrote:
>
>
>>The only thing I want to point out is the use of the zener diode, as
>>I've done in my supply.
>>
>>
>A zener is an interesting device. I conducts virtually no current
>until it reaches it's designed voltage than rapidly (over less than a
>few millivolts goes into full conduction (infinite current). A Zener
>placed across a DC level will absorb ALL of the current the source can
>supply as long as the voltage remains above the turn-off voltage of
>the device. The bad part of this is most zeners (you can afford) are
>rated at either 1W or 5W. They could easily see 10 times that amount
>of dissipation in a short period of time. In the case of a line surge
>or back EMF the zener will last in the microsecond time frame.
>

I did neglect to mention that I have a low value resistor in series with
the DC supply before the zener to limit the current the zener must pass
when the transformer is unloaded. This page describes and explains the
configuration i'm using:

http://tinyurl.com/8kvds

Dave