cupoftea
Advanced Member level 5
Hi,
Why is not every single offline flyback today a Quasi Resonant flyback?
The fact is that a QR flyback will always be just inside DCM.......so the turn ON of the MOSFET is not too critical....since its got zero current at turn on.......your range of values for the gate series resistor can be extremely wide.....so you can change the MOSFET at the drop of a hat, and need little "series gate resistor tuning" session time.
This is ideal, because these days, MOSFETs (and other components) go obselete every 5 minutes....but with a QR flyback, this is no problem, because you can quickly shovel in the next cheapest FET alternative offering and quickly do the series gate resistor tuning for the new FET.
So why is anyone in their right mind using constant frequency flybacks now?......(since in low mains, they may traverse into CCM.)
Why is not every single offline flyback today a Quasi Resonant flyback?
The fact is that a QR flyback will always be just inside DCM.......so the turn ON of the MOSFET is not too critical....since its got zero current at turn on.......your range of values for the gate series resistor can be extremely wide.....so you can change the MOSFET at the drop of a hat, and need little "series gate resistor tuning" session time.
This is ideal, because these days, MOSFETs (and other components) go obselete every 5 minutes....but with a QR flyback, this is no problem, because you can quickly shovel in the next cheapest FET alternative offering and quickly do the series gate resistor tuning for the new FET.
So why is anyone in their right mind using constant frequency flybacks now?......(since in low mains, they may traverse into CCM.)
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