Hi,
I have a simple question about the input undervoltage protection (page-3 of schematic). Can anyone please advise.
http://www.ti.com/tool/PMP8911
Schematic: http://www.ti.com/lit/df/slura79/slura79.pdf
B+ is around 400V (output of PFC). If you see the opamp U9B on page-3 , it will disable the VSNS pin of the PFC IC : UCC28051D which is good. LLC IC is disabled by monitoring the B+ voltage and once pfc is disabled, the LLC IC will be disabled as well. But, lets say the input voltage is around 70Vac or 60Vac, the PFC+LLC stages are both disabled, but the auxiliary supply is still ON, the reason is whatever the Vac input is, it appears right at the B+ output even though pfc, LLC are disabled ( rectified voltage at B+ = 70Vac * 1.414), this means the auxiliary power supply will still be working ( drawing few mW). Shouldn't the complete power supply be turned OFF under brownout condition? Please advise.
Best Regards,
Venkat