LNK623DG design that is not stable on 14.2V output
We use a LNK623DG as a switcher in a flyback controller to produce 14.2V DC
This voltage is used to power a DALI bus, where an current limiter makes sures that no more than 120mA_peak is drawn.
The DALI bus have power and 1.2kHz communication on the same 2 wires.
We experience a voltage instability on the 14.2V in operation.
We use a LNK623DG as a switcher in a flyback controller to produce 14.2V DC
This voltage is used to power a DALI bus, where an current limiter makes sures that no more than 120mA_peak is drawn.
The DALI bus have power and 1.2kHz communication on the same 2 wires.
We experience a voltage instability on the 14.2V in operation, see attached file.
- Is it poor cross regulation ?
- Is it pulse grouping ?
- Is it a light load problem …. ?
- Why does it climb a little and then drop approximately 1 volt ?
o Can we count on this behavior to be consistent ?
Hi kwa,
I could not open the video by the way but I think you pretty much covered everything i.e., the PSU is working well when on its own but has issues when connected to the DALI bus via a current limiter. Maybe this could be one of the limitations with primary-side regulation as output voltage perturbations are not directly/immediately 'visible' to the control.
I could not really suggest anything much since step-load tests seems OK. Also from your data, DALI bus voltage variations were always in response to a load change. Maybe we could try reducing the values of L3 or R200 and see what happens?
Also as you have stated, adding a 2k2 on the DALI bus helps. Maybe we can also try putting it on the 14.2V DC bus to work as preload. We can also increase its value if standby power becomes an issue.
Regardless, I have looked at the DALI physical electrical specifications and it seems fairly robust. Are we experiencing communication timeouts with the voltage levels that we have right now?
Best Regards,