After several countless nights without REM sleep and tons of downloads from the net, I finally managed to get my SMPS to work as intended. Final board shown below. Few learning points for me on SMPS.
- The rectifier diode recovery time is a critical parameter. Consider the switching frequency in diode selection. Slow diode will result in short circuit like behaviour on the secondary.
- Use of snubber circuit on the mosfet help to reduce the voltage spikes.
- Filtering and emi protection for sensitive digital circuit.
- Capacitor explodes with big bang... :-)