Design Reference DER-286

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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

 

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