transformer ET specs

Feb 14, 2008 1 Replies
J

Hi,



For this gate drive transformer:



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It has a Volt-time spec of 221 V-us)



So the primary will saturate in 1us at 221 volts, or 20us at 11 volts I think.



This transformer is specced to work for gate driving from 20kHz to 250kHz, and it has a 1:1 turn ratio. So for a fet gate voltage of 11V, this transformer could pulse for a maximum of



20us? So the minimum switching frequency would be 50kHz? I think I may be misunderstanding gate drive transformers as this one is specified to operate from 20kHz to 250kHz.

cheers, Jamie


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L

Note also this is at 25deg - at higher temperatures Bsat reduces as would Et.

If the transformer is capacitively coupled, you get 2xBsat flux swing to play with in Et considerations.

Recall that at 20KHz, a square wave developes Et during half the period; at duty cycles varying from this, the actual flux stress reduces.

For the application circuits referenced in the data sheet, a full 10v gate ampliude is not required - it's a signal application. The 'can be used at 20-250KHz' is not a 'specified' operating range, as you interpret.

If in doubt, recheck your application, test some samples, deconstruct the part and query the mfr.

RL

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