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Oring two flyback power supply with diode output.

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kudjung

kudjung

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Dear Power Expert,

I got a question.
What would happen when you oring and output of an isolated flyback power supply(with output diode) together? One of them has a higher voltage than the other around 0.2-0.25 volts.

TIA for any comments.

KJ
 

The higher voltage current will supply all the load current, until that load current exceeds that supply's capabilities and forces it to drop to a voltage where the other supply starts to provide current.

It works, but it is a very poor design practice.

For best results, you have to have an external circuit which monitors the percentage of the load current each supply is providing, and the adjusts the respective output voltages to achieve a close balance.

TI has an app note (formerly from Unitrode) discussing the technique
 

Suppose your flybacks send their output as brief pulses, which do not overlap. Therefore these arrive at the output (or reservoir) capacitor in interleaved fashion, similar to a flyback operating at twice the frequency.

Since your question is about 2 converters, it should be possible to combine it all into a full H-bridge and transformer. I suppose it's a question of whether is easier for you to construct 2 flybacks instead.
 

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