PFC stage with feedback loop crossover frequency = 200Hz?

Hello,

We are designing a Boundary Mode PFC stage for 330W, 90-265VAC.

The application is a guitar amplifier, so theres no actual need for PFC.

However, we wish to have PFC because otherwise the input electrolytics would get over-ripple current'ed........also, A high voltage PFC output makes the downstream SMPS easier to design.

Anyway, because we dont need PFC, we wish to just use the NCP1608 as a front end boost converter

https://www.onsemi.com/pub_link/Collateral/NCP1608-D.PDF

...The Boost FET current will thus have a lower RMS value, reducing FET losses.

Anyway, is their any reason why we would be advised not to do it like this?

I'm skipping the point if a guitar amplifier needs PFC to comply with EN61000-3-2, there have been sufficient previous discussions about it. If I remember right, you took part in it.

You missed however to explain the question title. A PFC needs in fact a voltage control crossover frequency considerably below 100 Hz, the Onsemi datasheet is e.g. suggesting 20 Hz. I guess, you mean to implement 200 Hz as a compromise between real PFC operation with current sine waveform and simple uncontrolled rectifier operation?

I'm not able to predict the exact behaviour with 200 Hz cut-off frequency, but the current waveform will be modified from sine towards a more rectangular shape, so the intended reduction of peak current can be probably achieved. By making the loop bandwidth too high, you'll get an unwanted high peak current around voltage zero instead.