A Gallium Nitride (GaN)-based DC-DC converter has received large research attention for automotive applications since it can support a wide range of input voltage, e.g., from 3V to 40V, to cover car battery voltage fluctuations at higher efficiency [1]–[3]. However, the reliability of GaN switches is a serious concern, especially in the harsh environment commonly found in such applications. The intrinsic failure mechanisms, where elevated junction temperatures (Tj) and excessive gate-to-source (Vgs) and drain-to-source voltage (Vds) cause the degradations in the on-state resistance (R0∩) and threshold voltage (Vth)ofaGaNdevice[4].Recentworkshaveproposedvariousreliabilitymanagementtechniques[5]–[15].Howevertheyarestilllimitedinthemultipleways.Firstofall,allofthepriorworkssolelyfocusonreliabilitybutitiscriticaltomanagebothreliabilityandefficiency.Also,someoftheworksemployedanopen−loopcontrol,whoseeffectivenessislowerthantheclosed−loopcontrol[9]–[15].Also,noneoftheworksmonitorallfourcriticalparameters,R_0,V_{th},T_j,andinductorcurrent(I_s),norutilizealltwocriticalcontrolknobs,switchingfrequency(F_{sw})andgatedriveswing(V_{drv}$), to maximize reliability and efficiency via a closed-loop control.