Xiaofan Chen wrote:

>>> You can make a very simple flyback converter that can have several
>>> isolated outputs and run from 5 or 12v. It would be much cheaper than
>>> 4 separate converters.
>>
>> I didn't think of this because I don't like custom transformers :)
> 
> I think you can get ready-made transformers. 

With 4 isolated secondary windings? Where do you think I should look? I
checked at Coilcraft, but didn't find any off-the-shelf transformers with 4
secondaries. The ones they have with two windings cost ~$3. (This is about
the price of a MIP4081...)


> An auxilary flyback converter is a good suggestion for your application.

It may be, if I can find a suitable (and cheap enough) transformer. 

But so far, using two MIP4081 seems to be cheaper and more comfortable, and
creating one non-isolated auxiliary voltage and using a bit of circuitry to
keep it at the right level for each gate looks like being the cheapest
alternative.

Gerhard

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