I have build the AC/DC flyback converter according to TI's reference design but ist is not working and I am wondering why. By the way: I have build the 5 V version, so everything connected to T1:9,7 I have not populated. It seems to me that the controller is not working at all. So far I have measured:
- Rectified high voltage: 328 V
- 5V Low voltage: 0 V
- U1:4: 0 V (after power up)
- U1:4: spikes to 40 V and decays (in approx. 100 ms) to 0 V (during power up)
What I plan to do yet:
- Verify polarity of the transformer`s secondary windings. (after confirmation from TI about the pin out this is obsolete now)
Do you have any advice what else to look for?
- Why the reference design is using an external current source, though the controller's datasheet suggests using the internal one (have a look at the block diagram)
Another thing to mention is: In TI's reference design they seem to have messed up the pinning for the transformer (WE 750316908). The primary side is ok but on the secondary the schematic symbol (pinning) does not correspond to the footprint pinout (would be glad if you could double check that).
What else to add? If some information is missing please let me know. Thanks in advance for your help.
edit: Link to transformer