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Design Reference DER-286

Posted by: sejfodedic on Mon, 06/05/2017

 

Hi,

My led driver is based on DER-286 and it works fine. I did not like latched over-voltage (load disconnect) shut-down and I made some changes: Q3 is removed and R18 is shorted. It looks good and when the load is disconnected it shuts-down and tries to restart about every 100ms. I was happy as I could reconnect the load any time again without switching the mains. But I noticed that it goes into latched shut-down after several minutes(sometimes many minutes) without load and it will not try to start up even if the load is reconnected again.  I measured the voltages:  Bypass BP pin (5.9V), Feedback FB pin (2.4V), Voltage Monitor V pin (3V), Reference R pin (1.25V), Vb=4V, Vs=6V. Drain Voltage is basically high. It will start again if the mains is switched off/on. It is interesting that it will start up (from the latched condition) by shorting the Voltage Monitor V pin or Bypass BP pin to ground.

Is there any reason for unexpected latched shut down? Any suggestion would be appreciated.

Regards

 

Comments

Submitted by PI-Crumb on Thu, 06/08/2017

Q2 needs to be connected to FB pin instead of BP. Please check DER-278 for reference.