SLUSC60B December 2017 – October 2019 UCC28064A
Resistor RZ is sized to attenuate low-frequency ripple to less than 2% of the voltage amplifier output range. This value ensures good power factor and low harmonic distortion on the input current. The voltage on the COMP pin needs to stay above 250 mV to maintain normal operation. If COMP falls below this threshold switching will stop.
The transconductance amplifier small-signal gain is shown in Equation 55:
The voltage-divider feedback gain is shown in Equation 56:
The value of RZ is calculated as shown in Equation 57:
CZ is then set to add 45° phase margin at 1/5th of the line frequency, as shown in Equation 58:
CP is sized to attenuate high-frequency switching noise, as shown in Equation 59: