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LCS708HG Switches OFF after Few Millisecond

Posted by: Shiv S on 03/13/2022

Hello Guys,

I am trying to run LCS08HG without transformer. I see that IC switches off after 5-7ms(timing seems random to me as off now). I have checked VCC, VCCH, IS and OV/UV remains fine (away from the bounds of protections) and does not shows any unexpected behavior. I see that Frequency starts from 800Khz and Drops to around 133Khz which is my stop frequency.

Please give any insight on what could be causing this issue.

Regards

 

Shiv

Comments

Submitted by PI-Wrench on 03/16/2022

It would be a good idea to post a schematic so that we can understand what you are trying to do. The frequency ramp you are seeing is due to the soft start circuitry inside the IC. Customarily, the operating frequency would be  defined by transformer leakage and the resonating capacitor.