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Dc/Dc controller LT8316 power limit

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kappa_am

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Hi,
I am designing a wide-range input DC/DC converter. I came to LT8316. It is a controller and we should use an external switch, but in datasheet, it is stated that the power limit is 100W. My question is why? while we can use any switch on output and scale feedbacks. Why limits the output power?

Thank you
 

above ~ 100 watt, layout, RFI, and transformer construction issues tend to dominate and need an experienced power electronics designer - the RFI especially can upset the control, the leakage inductance causes extra losses and over volt spikes on the main switch ..... and more ...
 

100W is often considered the upper useful limit for a flyback.

Flybacks make relatively poor use of the transformer meaning its size increases quickly with power. Around 100W other topologies become more attractive (like forward, push-pull, half bridge). There is a general tradeoff where higher switch count topologies allow more efficient use of the transformer.
 

Why 100W max because this IC designed for 100W operation, Internal Gate Driver Bias Voltage of IC is about 12 V this voltage cant drive Power MOSFET, with use of a gate driver it is possible.
For Flyback application below 100W is reasonable because flyback topology required MOSFET current ratting 5.5times required current. For example 1000W offline flybac(200V input), input current will be 5A so we need to select 27.5A MOSFET at 400V or above, this mosfet will be cost high. So above 100W application other forward topologies are selecting.
 

To be clear I don't think there is a 100W limit. The 100W number is Analog/Linear trying to be realistic and helpful (and they sell controllers better suited for higher power).

12V is fine for high power gate drive but the internal gate driver probably isn't strong enough to drive a large fet.

Otherwise yes I think you answered it. You could use this controller, perhaps with an external gate driver and very large fet to make a 1kw flyback converter. But it would be more expensive and larger than other topologies.
 

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