While it is theoretically true about stupid questions, there is no doubt about stupid answers.
Back to post #1, Is Fosc the clock frequency of a stand-alone PWM, or the clock frequency of a microcontroller that has an internal PWM? If the latter, then there probably is a pre-divider that can bring the PWM clock back down to its original value with the lower speed clock. And as mentioned above, there probably will be issues with a 48 MHz PWM carrier that were not present at 1 MHz, including radiated and conducted noise.
ak