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From: firstname.lastname@example.org (Bob Wilson)
Subject: Re: multiple flybacks in parallel
Date: Thu, 14 Nov 2002 04:18:10 -0000
Organization: Your Organization
X-Newsreader: WinVN 0.99.9 (Released Version) (x86 32bit)
In article , email@example.com says...
>"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
>> > existing magnetics to create the supplies. Rather than build 6
>> > 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.
...but you have the fun of trying to compensate for the right half-plane
zero that is inherent with a continuous mode flyback. This can reduce tour
loop bandwidth so much that transient response may be unacceptable.
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