schematics:
formatting link
this LED current driver comes from LM3433 by NSC. I am new to the power electronics. I made a same circuits as this evaluation board (NSC application notes AN-1736), my circuits failed after 20 mins without any signs. I used a hot air gun (~700 F) to solder this QFN and I wonder I damaged this part. Is it possible?
- The Mosfet got hot but the waveform was clean, the edge is ~100 ns and it must be fully-on or off. Why it failed without any sign? The waveform at Q1 and Q2 "S" likes this: _________ __ ___________ this is not a single toggle up and down switching signal? |_| |_|
2.How does the current flow in sync. mosfets? It looks the load is different from conventional sync. buck converter.
- Why the designer put so many bead and capacitors in parallel? to minimize the ESR and suppress the ringing from switching?
- D3 is to protect the LED from the reversed voltage from the main inductor?