This tiny 4-W flyback converter with additional three isolated-output windings generates four total outputs. By windings ratio 1:1 in between primary and auxiliary winding, the conventional RCD snubber can be replaced by an AC flying capacitor providing better efficiency and lower EMI This requires the lowest leakage inductance. The input automotive range is 7-V to 42-V surge. Three outputs are post regulated by an LDO to improve line and load regulation and power supply ripple rejection (PSRR).
A differential input filter has been added to attenuate conducted emissions and a Schottky rectifier acts as reverse-polarity protection. As for all multi-output primary-side regulated approaches using general purpose controllers, no load at the auxiliary windings is a limitation for cross regulation.
Features
- Three isolated outputs at 12 V, 5 V and 3.3 V and one single non-isolated output at 5 V
- Both 5-V and 3.3-V outputs are post regulated for the lowest possible noise
- Differential-input filter to prevent from reflected ripple
- Temperature rise less than +35 K at full load
- A table for all 16 load combinations with light load and full load is provided