T
treez
Guest
Hello,
Why do the following application notes, both by fairchildsemi, contradict each other about the nearness of the SMPS crossover frequency to the corner frequency of the output LC filter (“post filter”)
The text just above fig22, page 12 of the following document by Choi , suggests that TL431/opto feedback can be undertaken with the crossover frequency of the SMPS close to the corner frequency of the post filter (LC filter). (as long as the opto diode path is connected upstream of the post filter)….
Choi document:
https://www.fairchildsemi.com/techn...erations-for-Switched-Mode-Power-Supplies.pdf
So why then does part (b), on the RHS of page 10 of AN-4137 (below) state that the crossover frequency should be at least three times higher then the post filter’s corner frequency?
AN-4137:
https://www.fairchildsemi.com/application-notes/AN/AN-4137.pdf
…after all, both documents are referring to exactly the same connection configuration of the TL431/opto feedback components.
Why do the following application notes, both by fairchildsemi, contradict each other about the nearness of the SMPS crossover frequency to the corner frequency of the output LC filter (“post filter”)
The text just above fig22, page 12 of the following document by Choi , suggests that TL431/opto feedback can be undertaken with the crossover frequency of the SMPS close to the corner frequency of the post filter (LC filter). (as long as the opto diode path is connected upstream of the post filter)….
Choi document:
https://www.fairchildsemi.com/techn...erations-for-Switched-Mode-Power-Supplies.pdf
So why then does part (b), on the RHS of page 10 of AN-4137 (below) state that the crossover frequency should be at least three times higher then the post filter’s corner frequency?
AN-4137:
https://www.fairchildsemi.com/application-notes/AN/AN-4137.pdf
…after all, both documents are referring to exactly the same connection configuration of the TL431/opto feedback components.
