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We are making an offline 240VAC SMPS which after being installed, will firstly charge up a 24V battery at 5A for 3 hours. Then it will simply sit there for the next 10 years drawing about 2W of standby power, as the equipment continuously monitors some safety valves which should be actuated in...
Thanks, i must admit i'm stunned by the 93W offline flyback schematic of page 19 of the App note in post #1 above.
There is no primary clamp whatsoever.
That design would surely be classed a gross designer irresponsibility?
The internal fet in FSCQ1565 is only 650V rated.
I have been sent a flyback power supply by a customer to check out.
VAC input = 187-264VAC.
They have used a single 220k, MMB0207 resistor to act as the start-up resistor, which feeds the Vcc pin of the FSCQ1565 Flyback controller IC (as attached).
When VAC input is 264VAC, this means that...
Why do all the datasheet and app note schematics of high power offline flybacks with FSCQ1565 cotroller show no primary clamp whatsoever?
They only show a small Drain source capacitor, which they call the "resonant capacitor".
(which is true but it hardly seems big enough to quench leakage...