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flyback transformer matching

flyback transformer matching

flyback transformer matching

I'm working on a circuit where I want to be able to use flyback transformers from two different manufacturers. For reference, Halo TGSP-P028EFD20LF is one of them:


The two transformer pinouts are very similar, as both have dual secondary coils (S1 and S2) that get wired in parallel on the PCB. To get both transformers on the same footprint, one transformer I'll have a jumper in series with S1 but not with S2. I'm wondering if that is an issue.

Series resistance - increases by 10-20 mOhm (R_jumper), so about doubling the secondary ESR of S1, but negligible against series coil impedance of 18 jOhm)
Stray inductance - secondary leakage inductance increase is negligible

I could add a jumper in series with S2 to match the circuits. That seems like it just cost board space and doesn't improve anything.

Am I missing anything? Higher frequency effects? Is there anything else to watch out for?



RE: flyback transformer matching

Leakage inductance, parasitic capacitance, isolation voltage breakdown. Especially becomes an issue if you have emission approvals or important agency approvals on the end product.

Companies making products in high volumes where several vendors may make parts will sometimes use a network analyzer to plot the frequency response of the transformer as a means of knowing they are built the same. HP 3577, HP 4195, or AP instruments network analyzers are examples of instruments that might be used.

But lacking such resources, like me, measure the primary and secondary inductance, leakage inductance, primary to secondary capacitance, and make sure both give the same waveform operating in the same circuit.

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