Greetings all!
A question regarding power factor correction chips for switchmode power supplies (specifically, boost converters):
Many power factor ICs (example: L4981 from ST) include a pin for input voltage feedforward. The designer is supposed to apply a scaled version of the rectified AC input voltage to the feedforward pin.
I understand that the purpose of this feedfoward pin is to help keep the DC output voltage constant if any sudden change in the AC input waveform happens (I.E. a power surge, or brownout).
Question: Why does this feedforward voltage get squared?
For PFC, the duty cycle equation is something like:
Duty Cycle to comparator =
K * Iin(ac)*vout(dc) / (Vff(ac) ^ 2)
where K is a simple constant
A question regarding power factor correction chips for switchmode power supplies (specifically, boost converters):
Many power factor ICs (example: L4981 from ST) include a pin for input voltage feedforward. The designer is supposed to apply a scaled version of the rectified AC input voltage to the feedforward pin.
I understand that the purpose of this feedfoward pin is to help keep the DC output voltage constant if any sudden change in the AC input waveform happens (I.E. a power surge, or brownout).
Question: Why does this feedforward voltage get squared?
For PFC, the duty cycle equation is something like:
Duty Cycle to comparator =
K * Iin(ac)*vout(dc) / (Vff(ac) ^ 2)
where K is a simple constant