grizedale
Advanced Member level 3
hello,
Does adding a resistor in parallel with an SMPS feedback opto diode reduce the gain in the feedback loop?
i mean like R33 in the following :
https://i55.tinypic.com/2zhin3p.jpg
...because if we think about it, when the TL431 trys to pull current through the opto, it ends up pulling it through the resistor too.....so not as much got pulled through the opto-diode....and thus the feedback gain will be reduced.?
i know that the resistor in parallel with the opto-diode is needed to provide bias current to the TL431, but wouldnt it be better to just connect a resistor directly from the TL431 cathode to the output voltage rail?....because then we would get better feedback loop response?
Basically , the transient response is reduced by adding the resistor in parallel with the opto-diode?
Does adding a resistor in parallel with an SMPS feedback opto diode reduce the gain in the feedback loop?
i mean like R33 in the following :
https://i55.tinypic.com/2zhin3p.jpg
...because if we think about it, when the TL431 trys to pull current through the opto, it ends up pulling it through the resistor too.....so not as much got pulled through the opto-diode....and thus the feedback gain will be reduced.?
i know that the resistor in parallel with the opto-diode is needed to provide bias current to the TL431, but wouldnt it be better to just connect a resistor directly from the TL431 cathode to the output voltage rail?....because then we would get better feedback loop response?
Basically , the transient response is reduced by adding the resistor in parallel with the opto-diode?
Last edited:
