buck quasi-resonant zvs converter with linear feedback control

s + 1506A v ( s)= 20750(11)s(s + 4150)In Fig. 7 we compare loop gains of the buck QR-ZVSconverter: (1) with CMC and (11); (2) with the LQR inTable III for ρ=0.01. Although CMC and LQR havedifferent feedback gains in Fig. 5, the LQR may presentsimilar closed-loop performances to those obtained byCMC, due to the similar dominant poles in closed-loop.This is illustrated by Fig. 8, where theoretical closed-loopresponses of the buck QR-LQR converter, with differentgains, are compared with that obtained by CMC, for thesame sudden change of the reference.R L =160mΩ and R C =80mΩ where measured at 100 kHz.The LQR was implemented for ρ=0.01.Fig. 10 shows some experimental waveforms for R=2.2Ω.Fig. 11 shows perturbations of the output voltage and theinductor current caused by a variation in the referencevoltage.Fig. 9: Experimental buck QR-ZVS converter with LQR.Fig. 7: Loop gains of the buck QR-ZVS converter.Fig. 10: Experimental waveforms (V I =15.5V; V O =5V).Fig. 8: Predicted closed-loop responses of v O .5. EXPERIMENTAL RESULTSA prototype of a 25W, 1 MHz, buck QR-ZVS converterwith LQR is shown in Fig. 9. The parameters are those inthe previous section. The equivalent resistencesThe closed-loop small-signal model with LQR can beobtained by replacing (7) in (8). The resulting equation,with v ˆI = 0 , was solved numerically (with MATLAB)for the experimental values of the reference voltage inFig. 11. The theoretical result is shown in Fig. 12 and itpresents a very good agreement with the experimentalvalue of the output voltage (Fig. 11).5