Opto-couplers in smps part 2

Feb 03, 2007 2 Replies

Hi again, I like to continue the discussion regarding opto-couplers as isolating element between secondary sided error amp and primary side pwm control. Some people mention it's possible to use kind off pwm-style to interface the error signal. I realize how this may be done on the secondary side, but how is the pwm signal actually integrated to become an analouge voltage for pwm control. This should require a pwm carrier frequency many times above the main converter operating freq.



Any advice is appreciated.



Stefan



just pass the primary side pulse from the OpTo to a T network of a R and CAP. use a unity gain Transistor to buffer it. make sure PWM to this network has a common sink to discharge the reference as well.. Or am i not in the same ball park as you are?

"I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5

The most common arrangement is the opto-LED in series with an adjustable zener such as a TL431 across one of the rectified and smoothed secondary supplies.

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