[iyonix-support] Re: Iyonix hanging (was Re: EtherK not starting up reliably)
- From: Dave Higton <davehigton@xxxxxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Mon, 28 Aug 2006 14:14:22 +0100
In message <4e5d7395b3tim@xxxxxxxxx>
Tim Hill <tim@xxxxxxxxx> wrote:
> I can wire a plug, or for that matter an entire theatre, but I am no
> qualified electrician and these (potential) problems with an Iyonix PSU
> leave me puzzled. We have a machine whose processor supposedly gobbles up
> less power than a Plentyhum heater but whose PSU seems incapable of
> delivering its meagre requirements. Is it that there is too little load
> for tolerances to be met? Two hard drives here cause no problems, AFAICT.
>
> Or are the PSUs a bit on the shoddy side?
If you were to examine all aspects of a wide selection of commercial
off the shelf power supplies, you will find a lot of examples of how
they ought not to behave. For example: on start-up, the ideal is a
ramp of controlled dV/dt[1] up to the specified voltage, where it
remains unchanged from then on. You'd be surprised what crap is out
there. Some PSUs provide an exponential ramp up, so the rails may
not have reliably reached their correct voltage when reset is
released. I've also known of one /very/ respectable manufacturer
whose supplies /overshot/ the correct voltage, even into a purely
resistive test load.
Lots of people seem to assume that the design of power supplies is
easy. It damned well isn't.
Dave
[1] Controlled dV/dt is so that it goes slow enough to charge up all
the decoupling capacitors in the load without having to provide an
impossibly high current; yet fast enough so that the rails are at
their correct voltages by the time the reset line is released.
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