LED Driver by TOP250YN

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I want to design 25V and 3.5A LED driver by TOP250YN.

I know how PI get feedback from voltage and hw pi do this by TL431, but how could I limit the current to 3.5A and constant the current on 3.5A?

I read DER136 but I couldnt understand how you get feedback from the output current and give it to led of optocoupler to constant the current to a value.

I also dont know what kind of feedback I should give to control pin (C) to have constant current?

Do you have any suggested circuite for make constant current for TOP250YN ?

PI Expert design is in attachment

Thanks in advansed

Dr. Al Sam

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For LED Drivers that requires PF, we recommend using the products design for LED drivers.

You can check the link below for a reference design which is way much simpler than DER-136.


 Please answer.
Why is a diode in the circuit flow key? How can a reverse current to flow through the key
- Show circuit and explain the conditions.

Please rephrase your question and use reference to which circuit you are refering to.

 The article of http://www.powerint.com/sites/default/files/PDFFiles/rdr290.pdf
consistent with the key turned on diode D4.

Similarly done in the scheme in DER-136 to protect against reverse current flow through the key, if the power
less reflected voltage. .

  I do not understand why there might be a reverse current - because the polarity of the reflected voltage is always the same.


  Flybаck  topology is the same as Boost and there is nowhere reverse current through the switch.
  So why is it may appear.

The reverse voltage can come from the resonant rIng of the flyback converter especially when the input is close to the zero crossing of the rectified input.

When these schemes make the controller and discrete switch, you never put a diode - the switch is integrated bypass diode.
  In the top is also a bypass diode.
  So why put more diodes - explain below. if you can.

If I'm wrong and protective diode in key Top No, it is best not to put it
consistently on direct current switch and parallel to switch
the reverse inclusion.

If your refering to D4, PI recommends to put it in series with the drain pin. Btw, you always mention key, can you explain what are you refering with the word key.

 I am Russian. In the Russian language, electronic key and switch for power
schemes have the same meaning.
  Meaning - to protect against reverse voltage supply in parallel
diode as a powerful CMOS.

  Then the current through it will be much less. only at times at low supply voltages and this will reduce the power loss.

Thanks for the info.

Design Idea DI-113 is a design with CC function.   This is under tNY-lll parametric search but will work for TOPSwitch as well.