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eem2am
Joined: 22 Jun 2008
Posts: 753
Helped: 13
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 02 Jan 2009 19:06 smps isolated feedback |
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hello
Page 8 , Figure 1 of LM2587 PWM controller datasheet
http://www.national.com/ds/LM/LM2587.pdf
...shows the comp pin (pin 1)
If i do this isolated, using opto feedback (4N35 & TL431 error amp on secondary side) then how can i connect the opto transistor....can i just put the collactor to pin 1 and the emitter to ground...?
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FvM
Joined: 22 Jan 2008
Posts: 5154
Helped: 767
Location: Bochum, Germany
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02 Jan 2009 20:29 how to get isolated feedback with SMPS |
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| Why do you think that pin 1 should be used for feedback purpose? This operation isn't suggested by National in any application circuit, as far as I see. Pin 2 is intended for feedback.
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eem2am
Joined: 22 Jun 2008
Posts: 753
Helped: 13
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03 Jan 2009 18:34 how to get isolated feedback with SMPS |
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hello,
thankyou for your interest, in non-isolated form, pin 2 is for feedback, but when isolated, please see this app note.....(Figure 5, page 4)
http://www.national.com/an/AN/AN-1095.pdf
It is of great mystery to me when it is, and when it isnt possible to go stright to the output of the error amplifier like in this app note.
Any help greatly appreciated....
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FvM
Joined: 22 Jan 2008
Posts: 5154
Helped: 767
Location: Bochum, Germany
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03 Jan 2009 20:35 how to get isolated feedback with SMPS |
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| As the National AN answers your previous questions to my opion, also from your other thread, e. g. regarding typical OC pole, which are still left open?
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03 Jan 2009 20:35 Ads |
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ranggaperdana_06114
Joined: 12 May 2008
Posts: 64
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09 May 2009 3:26 how to get isolated feedback with SMPS |
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how to make the isolated power supply with voltage +- 12 v ?
tanx
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