auxiliary power supply for pfs 714
Posted by: Frederic Schlitter
on
im designing the PFC with a pfs714, the problem i have is you require an auxiliary power supply of 12v on vcc, do you have a circuit, or i just add a resistor and a cap between the diode bridge BR1 and the inductor L5 and what is the current required
Comments
When we supply the Vaux to both circuits (PFC and the LLC) shall we use the same auxiliary ground for both circuits or it has to be individual with separate supplies.
Since both PFC and LLC are based on the same primary return, the same auxiliary ground can be used.
The bootstrap will work for initial startup then an aux. Supply is needed (running from resistor, diode, cap would result in high dissipation in the resistor (~4mA x VAC . We usually add a LinkSwitch-CV or TinySwitch-III flyback supply for this. You may also consider adding a bias to the boost inductor (few turns as a separate winding with ultrafast diode and capacitor plus linear regulator to limit maximum voltage into the PFS supply pin). I'll ask a collegue to post info on this approach.
Cheers PI-Chekov