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From: "John Jardine"
Subject: Re: 2.5kW-3kW-SMPS-(cheap)-suggestions?
Date: Tue, 17 Dec 2002 23:29:36 -0000
NNTP-Posting-Date: 17 Dec 2002 23:16:48 GMT
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
fred bartoli wrote in message
> John Jardine a écrit dans le message :
> > Help!
> > Thanks
> > john
> your load is resistive. Take advantage of it... Does your output voltage
> have to be regulated ? As it's heating element I guess the answer is no.
> Right ?
> The last question is do you need isolation ?
> In case yes I'll go for a simple push-pull, fixed near 50% duty cycle,
> supplied by a bridge with a *low* value bypass cap (only HF decoupling)
> nothing other than the load resitor on secondary side. Doing this you'll
> have the PFC for absolutely free.
> Just wind the transformer to have the right stepdown ratio.
> Set the duty cycle a bit under 50% so that you could use a current feed
> scheme to equilibrate peak current in each half primary, avoiding core
> If you need some regulation, do it on a (mains) cycle by cycle basis and
> leave the heating element thermal inertia do the job for you.
> Simple, rudge, efficient and hard to beat the cost.
Thanks Fred. Yes ... the output does need some kind of regulation (only to
about a volt) but I do need the isolation. Pleased you mentioned the 'no
input storage capacitor idea', it's something we got a 'patent applied' on a
few years ago (never pursued) and It's worth looking at again, (spice
nowadays works nicely with switchers) . As you mention, it is -just- a
heating element and it doesn't give a damn as to the 'shape' of the power
applied. It simply integrates everyhing it comes across. I only need take a
(true) RMS measurement.
Knowing my luck, I've a strong suspicion there will be some aspect of the
equipment spec' limits that forces me to move to the PF pre-reg that Gibbo
suggested. The devil is always lurking in the detail!.
(Most probably the EMC police would come to lock me away :-)
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