I am having a slight confusion regarding the selection compensation pin of the UC3842 IC and the current mode control system given in the datasheet.
- Why is there an RC combination at the feedback of the error amplifer? Can I simply use a resistor at that pin?
- Secondly as far as I have seen, the optocoupler will allow a current to flow in the right side only if the voltage gets below the threshold. But this will only give either a high or a low voltage at that pin. It wount give the amount by which the voltage got decreased or the real reference as is done in the TL494 IC where the IC gets a propper reference from the voltage divider as shown below. But here from getting either a high or a low how can we figure the measure of change of pwm duty cycle??
UC3842:
Kindly help me out in understanding these two concepts and the working of this IC with optocoupler. Considering I am using the voltage mode of the UC3842 IC. Here is a scehmatic of the changes made in the current and voltage mode control:
