Derivation of modified buck boost converter
I am reading this IEEE paper which explains the modified buck boost mode operation . I am failing to understand the current paths and equations given by the author for buck mode.
based on these images of operation my questions are
1.How come equation (5) for magnetizing current (Im) includes terms of VC2 , VLsec and VHV because VC1 is acting as only voltage source across LPrim which will discharge its energy in Lm connected across it ?
2.why equation of IS4 (6) does not include VLV which is actually part of the current path ?
3.why in the equation of IS2 numerators , units do not match ?
4.Induced current in Lsec (by dot convection) and direction of Is4 are opposite , does it mean the couple inductors are acting as two separate inductors without any flux linkage (is4 cancels induced current ) ?
5.waveform of IS4 shows rising current ramp but Voltage difference ( VHV-VLV) is applied to series LC circuit ( C2-Lsec) which should have parabolic shaped IS4 ?
1 answer
How come equation (5) for magnetizing current (Im) includes terms of VC2 , VLsec and VHV because VC1 is acting as only voltage source across LPrim which will discharge its energy in Lm connected across it ?
I'm not following this either. With S4 closed, VLV, Lsec, C2, and VHV are all in series in a loop. Therefore VHV - VC2 - VLsec should always be VLV.
I wonder if VLsec in equation 5 was really supposed to be VLV? Is so, the numerator would be the voltage across Lsec. That divided by an inductance would indeed result in the derivative of the inductor current. The constants "n" and "k" aren't defined, at least in the snippet you show. They seem to have something to do with the coupled inductor coupling and turns ratio.
There seems to be lots left out, at least in what is presented in the question. I'm not going to try to guess any further.
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