Re: Bulletproof your WG6100!

On Wed, 14 Jan 1998 12:44:30 -0800, Clay Cowgill <clayc@diamondmm.com> wrote:

>Alright Anders!
>
>Count me in for 5-10 depending on what your "quantity" price break is. :-)
>
>On a related note... I'm still fascinated with the idea of trying to
>upgrade a WG6100 to WG6400 performance specs. Soooo...
>
>National Semiconductor sells the LM317HVH. That's a "high voltage" version
>of the 317 and as such can regulate from 1.2-57V. (enough to get into the
>48V band the WG6400's looking for. ;-) Question for Anders: How much
>current do the 317/337 on your replacement board need to source? (The
>reason I ask is that the LM337HVH is a TO-93 and can only source a few
>hundred mA.)

On Anders design the current sourced by the LM317's is dependent upon the gain
of the output pass transistors. Aren't they around 30 HFE? So that would mean
for 5 amps max current the LM317 would need to source 166.6 ma. And since this
only at peak max, the LM317s should be just fine.

One thing to be aware of is the voltage ratings on these things are only the
maximum input/output differential. If you plan on placing 57 volts on the input
of the LM317 and regulating it down to 1.2 volts, your going to need an
LM317HVH. But if you plan on an input voltage of 55 volts, and then regulating
it to 48v then you're only talking a 7v difference which can easily be handled
by a standard LM317. Of course an accidental short on the output would cause it
to exceed it's rating, and I suppose this could happen if the output transistor
were to short and the output of the power supply was also shorted.

-Zonn

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Received on Wed Jan 14 13:52:28 1998