EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ocset on November 16, 2017, 11:17:43 am
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Hello, :blah:
In light load, BCM boosts go to high frequency. :scared: This should be limited by the controller.
Why does the L6562 datasheet not give the minimum off time?
(its a fixed off time controller)
L6562 datasheet
http://www.st.com/content/ccc/resour...CD00003316.pdf (http://www.st.com/content/ccc/resour...CD00003316.pdf)
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Page 16 of the L6562A BCM Boost PFC controller datasheet states that a bias winding is not necessary for the L6562A.....and a simple “RC method” can be used instead...........why does it say that the ‘RC method’ even works when the mains peak voltage is just below the output voltage?......why bother to state this?, i mean, why wouldn’t it work in that situation?......and even if vout was lower than mains peak, ...so what?.......would that mean that the "RC method" would not work?...and that a bias winding would be needed? :-//
L6562A
http://www.st.com/content/ccc/resour...CD00151385.pdf (http://www.st.com/content/ccc/resour...CD00151385.pdf)
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The following st.com application note shows an L6562A being operated in simple constant off time mode :clap: ..........This allows us to have a settable maximum operating frequency... :clap: ..so no matter how light the load goes, the operating frequency does not get ridiculously high. :clap: I cannot understand why they only offer this use of the L6562A as a sort of aside....i mean, its clearly better than the “usual” Critical conduction mode method of operation. Why is constant off time mode not the main method of control for the L6562A? :-// :scared:
L6562A in constant off time mode App note.
http://www.st.com/content/ccc/resource/technical/document/application_note/dd/ab/71/7a/f9/cc/43/c2/CD00195418.pdf/files/CD00195418.pdf/jcr:content/translations/en.CD00195418.pdf (http://www.st.com/content/ccc/resource/technical/document/application_note/dd/ab/71/7a/f9/cc/43/c2/CD00195418.pdf/files/CD00195418.pdf/jcr:content/translations/en.CD00195418.pdf)
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