I have used ACSNS pin for sensing the secondary side voltage for making decision on turn-on / off of synchronous rectifier.
Which pin can i use for sensing the input voltage. Please advice me.
Input Voltage range: 350Vdc to 450Vdc
For resonant mode the ACSNS pin is used to drive the synchronous rectifiers. Hence, ACSNS cannot be used to sense the input voltage anymore.
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Based on the input voltage, the gain will change accordingly. So any other pin can be used for sensing the input voltage.
Am not sure, how the system behaves without sensing the input voltage. As per our design the input range would be 350Vdc to 450Vdc.
For resonant mode a change in input voltage will change the switching frequency to maintain regulation. However, if you see the gain curves they are very non linear so performing a linear feedforward function is not suitable.
Anyway, ADP1046A does not support sensing of input voltage in resonant mode. This is not a problem though as the L, L, and C of the LLC stage i.e. the transformer should be designed such that it will be able to handle a wide range from 350Vdc to 450Vdc. Sensing the input voltage has nothing to do with the operation of the part.
What did you want to use the input voltage for? If you needed to sense the input voltage to turn on the supply, then you need to use an external window comparator from 350-450Vdc feeding into the PSON pin. Alternately you can use the PGOOD signal from the previous PFC stage to send a signal to the ADP1046A to turn on.
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