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2 watt power supply with minimum quiescent current

I'm starting design a supply to run from 75 - 150 Vdc line input.

The outputs are 3.3V +/-2.5% @ 250mA max and 24V +/- 15% @ 50mA max.

Min is 3.3V at 50mA and 24V at 1mA.

I'm looking a DCM flyback but was wondering if there are things to look design in to keep the efficency high (input current to a minimum) when the supply is lightly loaded.

Already doing the following.

1) Bootstrap startup circuit is 100-200uA directly fron the line them the 24V is fed back to power the control sircuits

2) Shottky diodes used.

3) switcing frequecy kept to 100Khz to control swithing losses while keepign the design small

Any thoughts or different topology suggestions for this type of supply?

Reply to
mook Johnson
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With DCM flyback, you can run frequency-modulated, which is the best way to keep power train losses down at light load. Fixed frequency devices have to assume an intermittent burst operation to do the same thing. Both are 'audible'.

RL

Reply to
legg

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