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From: "Harry Dellamano"
Subject: Re: multiple flybacks in parallel
Date: Wed, 13 Nov 2002 17:05:05 -0800
Organization: Posted via Supernews, http://www.supernews.com
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"Roy McCammon" wrote in message
> Steve Denning wrote:
> > I am working on an application where I need 6 low power outputs(approx
> > each) but each output must be isolated from each other. I'm required to
> > existing magnetics to create the supplies. Rather than build 6 seperate
> > supplies I am wondering if I could use one PWM chip and MOSFET and put
> > flyback transformer primaries in parallel. I would get feedback from
> > supply to try to control the others. The load on all supplies is the
> > My gut tells me not to try this, but in theory I guess it could work.
> > anyone tried this? What would the risks be?
> The flyback stores energy in the primary during one part
> of the cycle and transfers it to the secondary during the
> other part of the cycle. You vary the total power
> by varying the energy stored in each cycle, or varying
> the number of cycles per second. Each of your transformers
> will see the same cycle time and frequency, so the energy
> transferred will be inversely proportional to the primary
> inductance. How well do the inductances match?
Hey Roy, that is only true in discontinuous mode of operation. In
continuous mode you must use a single transformer with multi output
windings. In continuous mode and multi transformers the delta Ip are equal
but the DC components will not balance.
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