LNK3294G 5V 80mA Buck-boost topology support

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In new design I'm using LNK3294G IC (165V to 400V AC application). Design will be running on either 240VAC or 400VAC continously, required output voltage is 5V, current draw will be switching between 20mA and 80mA every ten or so minutes.

Can such low power output be achieved with LNK3294G? While design is based on PIXI, design guide (used 725V, could not find 900V version, assume most of guidelines apply) and reference designs, resulting design is working sufficiently well but there are some points I would like assistance with.

1. Inductor selection for such low output is a bit problematic. PIXI suggested value is 570uH (very low), at the moment two boards with 820uH and 1000uH are running, PIXI suggests to "Verify SOA limit is not violated or increase L". Can you explain a bit on what parameters to check?
Also are 820uH and 1000uH inductance values suitable? Going higher than 1000uH results in clearly audible acoustic noise (magnetic resin SMT inductors are used).

2. Is reduced current limit or standard current limit better (provided this application is feasible)? And can R2 be disconnected since voltage from output voltage after diode is going to be lower than bypass pin voltage?

LNK3294G_5V_80mA_165-400VAC.png155.47 KB

Hi Darius,

Thank you for the question.

I need more information in order to get myself familiar with your design. Could you please post here
- the design PIXLS spreadsheet.
- some inductor waveforms (2-5 switching cycle interval and 100+ switching cycle interval)
- Switch voltage waveforms as above
for the 820uH inductor case.

Best Regards,