Flyback with Parallel diodes or parallel secondary_and_diodes?

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cupoftea

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Hi,

there are documents discussing the "paralleling diodes" problem.
It is well known that thermal runaway reduces the benefit of "paralleling".

Also: what benefit do you see in paralleling diodes?
* reduced power loss?
* reduced forward voltage?
* increase current rating (mind both diodes are in one case)

*****

two coils, two diodes:
The current sharing here works way better. Not only because of the series "static" coil resistance that provide a better sharing,
but also the thermal runaway is - at least partly - compensated by the coil. The coil is copper with a rather high PTC behaviour, while the diodes have (bad) NTC behaviour.

One can not give general numbers ... they need to be calculated individually.

Klaus
 
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Thanks, to be honest it looks gimmicky to me now....i mean, why dont they just use one coil and one diode, or one coil one diode and a heatsink....or one coil, and a sync rect on the diode.
They have the hassle of 2 coils and each to be equally coupled to the pri.
 

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Hi,

maybe because of skin effect.
Or they want the option to connect both coils in series.

Klaus
 
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