M
Mike Deblis
Guest
I'm trying to find a better NFET than an IRF740, preferably in a TO220 or
similar package, for a HV PSU. 250V 50mA from 12V 2A in.
What I'm trying to do is get a Qg around the 20nC mark, Vds > 250V, Id >2A
with as low an Rdson as possible in order to minimise losses. If I can get
Rdson really low (sub 0R100 if poss), the FET losses will drop but high Qg
(>60nC) is a problem for the driver... Currently I'm hitting 81% efficient -
I'd like to get closer to 90% if possible...
The drive chip is a MAX1771. The inductor is 47uH 0R045 and 2.6A. Current
limiting resistor is 0R050 which limits the max inductor current to 2A ATM.
Board is carefully laid out as per data sheet recommendations.
Thanks
--
Mike
similar package, for a HV PSU. 250V 50mA from 12V 2A in.
What I'm trying to do is get a Qg around the 20nC mark, Vds > 250V, Id >2A
with as low an Rdson as possible in order to minimise losses. If I can get
Rdson really low (sub 0R100 if poss), the FET losses will drop but high Qg
(>60nC) is a problem for the driver... Currently I'm hitting 81% efficient -
I'd like to get closer to 90% if possible...
The drive chip is a MAX1771. The inductor is 47uH 0R045 and 2.6A. Current
limiting resistor is 0R050 which limits the max inductor current to 2A ATM.
Board is carefully laid out as per data sheet recommendations.
Thanks
--
Mike