T
treez
Guest
Hi,
I am not sure why feedback optocouplers in SMPS are deemed as being wear-out components?
Do you know?
After all, if (as attached) one uses a low value of RLED resistor, then there is plenty of room for the opto CTR to degrade massively and yet still the SMPS will be in control.
For example, the attached offline flyback could suffer reduction of opto CTR down to just 4% and it would still be able to control itself.
However, Unfortunately the opto datasheets don’t depict age related CTR depreciation.
Maybe the attached would suffer opto CTR degrading down to less than 4% within a few years of 12 hours a day operation in 85degc ambient?
Opto datasheet (CNY17)
https://www.mouser.co.uk/datasheet/2/427/cny17-1767437.pdf
(pdf and LTspice sim attached...plus the TL431 model files for the sim if you wish)
I am not sure why feedback optocouplers in SMPS are deemed as being wear-out components?
Do you know?
After all, if (as attached) one uses a low value of RLED resistor, then there is plenty of room for the opto CTR to degrade massively and yet still the SMPS will be in control.
For example, the attached offline flyback could suffer reduction of opto CTR down to just 4% and it would still be able to control itself.
However, Unfortunately the opto datasheets don’t depict age related CTR depreciation.
Maybe the attached would suffer opto CTR degrading down to less than 4% within a few years of 12 hours a day operation in 85degc ambient?
Opto datasheet (CNY17)
https://www.mouser.co.uk/datasheet/2/427/cny17-1767437.pdf
(pdf and LTspice sim attached...plus the TL431 model files for the sim if you wish)