Hi Team,
I am reading the SLUA560C appnote:UCC28950 600-W, Phase-Shifted, Full-Bridge. Here is the link:www.ti.com/.../litabsmultiplefilelist.tsp
Can you help me to understand the equation 13and 14 in page 5? how did you get these equations?
Regards,
Yangbo!
Hi Yangbo
The equations are derived from the normal calculation of the RMS value of a trapezoidal waveform - for example you can see the derivation in the example at https://masteringelectronicsdesign.com/the-rms-value-of-a-trapezoidal-waveform-part-2/ . This site gives the equation for a trapezoid as
This equation can be manipulated into the form used in the app note
I've replaced V by I . The duty cycle of the secondary current is half that seen on the primary because current flows alternately in the two halves of the secondary winding and this is the reason for the factor D/2 instead of D (ie we use t1/T_cycle rather than t1/T, Tcycle being 2*T of course)
The next thing step is to calculate the RMS of the currents during the three different parts of the secondary waveform (red, blue and green below) and then sum them as shown in eq 16 of the app note.
I hope this answers your question, please let me know if you need further information.
Regards
Colin
