RS is the sensing resistor of the PFC boost converter. During
the steady state, line input current x RS = IGAINMOD x 3.5K.
Since the maximum output voltage of the gain modulator is
IGAINMOD max x 3.5K= 0.8V during the steady state, RS x line
input current will be limited below 0.8V as well. Therefore, to
choose RS, we use the following equation:
RS =0.8V x Vinpeak/(2x Line Input power)
For example, if the minimum input voltage is 80VAC, and the
maximum input rms power is 200Watt, RS = (0.8V x 80V x
1.414)/(2 x 200) = 0.226 ?.