6
3.2.2 PF CIRCUIT
Power ON
When AC input turn ON, the level of U12-11 rise up to +4.3V.
When input voltage of U12-11 become 3.3V, the output of U12-12(nPF) turn “H”.
Then system goes to operation mode.
Power OFF
When AC input turn OFF, the level of U12-11 fall to 0V.
When input voltage of U12-11 become 2.2V, the output of U12-12(nPF) turn “L”.
Then system goes to standby mode.
+21.6V 24.4V
19.6V
PF
signal
+5V
PF signal timing chart