Re: Dell E172fpb
Regarding my previous post... The attached schematic (from model DV172) does not completely reflect the E172fpb's circuitry. In comparison the F172fpb is similar to that of the DV model schematic referenced; however the short circuit protection, as well as the feedback loop, are VERY different (much more complex). I believe this is where the design flaw is at. When designing any switch mode power supply feedback and short circuit protection (SCP) are critical. If any components in this region are not optimized, changes due to temp, fault... may cause failures (i.e. shorted components).
Switch mode power supplies are nothing like linear power supplies... they are very efficient, but dumb! They need constant feedback in order to maintain proper voltages on the secondary side. If a lamp shorts out, the primary needs to adjust for that, otherwise poof transistors blow... I am in the process of creating a PSPICE circuit identical to that in the dell monitor.
However, I may just alter my circuit board to reflect the posted circuit (DV model) eliminating such a complex SCP and feedback circuit. As far as I can tell, there haven't been too many complaints on that model. I'll keep you posted.
Regarding my previous post... The attached schematic (from model DV172) does not completely reflect the E172fpb's circuitry. In comparison the F172fpb is similar to that of the DV model schematic referenced; however the short circuit protection, as well as the feedback loop, are VERY different (much more complex). I believe this is where the design flaw is at. When designing any switch mode power supply feedback and short circuit protection (SCP) are critical. If any components in this region are not optimized, changes due to temp, fault... may cause failures (i.e. shorted components).
Switch mode power supplies are nothing like linear power supplies... they are very efficient, but dumb! They need constant feedback in order to maintain proper voltages on the secondary side. If a lamp shorts out, the primary needs to adjust for that, otherwise poof transistors blow... I am in the process of creating a PSPICE circuit identical to that in the dell monitor.
However, I may just alter my circuit board to reflect the posted circuit (DV model) eliminating such a complex SCP and feedback circuit. As far as I can tell, there haven't been too many complaints on that model. I'll keep you posted.
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