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LYTSwitch-1 delayed turn-on

Posted by: Lance Johnstone on Mon, 10/25/2021

Hi there...

I'm using a LYT1604 in a low-side buck 20W 60V integrated LED PCB driver.  Some of the units are experiencing a turn-on delay of between 1 to 5 seconds.  Once they start they run at the correct power level.

The circuit is as per Fig.1b in LYTSwitch-1 datasheet.  Values used for the various components are as per recommendations from PIXIs 10.  I have tried replacing the LYT1604, but the problem persists.  The circuit seems to perform the same on both working and non-working boards - power on BP pin ramps up uniformly to VCC in ~7ms, etc. but FET switching is delayed on the 'faulty' units.

Can you please shed some light on what might be the cause?

Thank you, regards

Lance

 

 

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Submitted by PI-Bombadil on Thu, 11/04/2021

Hello Lance,

 

Thank you for using Power Integrations product. It seems there is some fault being detected leading to the turn-on delay. Do you mind sharing the schematic with the actual values/component part numbers you have used? Also, if you have some waveforms gathered, like the current or voltage of FET, it would also help if you can share them.

Thanks.