A　half-bridge　LLC　circuit　with　controllable　resonant　inductor　was　proposed,　which　adjusts　the　inductance　of　the　resonant　inductor　according　to　the　output　current　to　change　the　parameters　of　the　resonant　cavity,　so　that　the　switching　frequency　can　be　basically　kept　constant,　and　the　light-load　burst-mode　range　of　LLC　converter　was　reduced.　This　ensures　that　the　converter　has　no　noise　when　outputting　in　a　wide　power　range,　and　has　excellent　output　characteristics.　The　magnetic　circuit　of　the　variable　inductor,　the　control　method　of　the　variable　inductance,　and　the　operating　principle　and　operation　process　of　the　LLC　converter　were　analyzed　in　detail,　computer　simulations　were　carried　out　on　the　proposed　circuit　and　its　control,　and　a　prototype　with　an　input　of　740　V,　an　output　of　420　V,　a　full　load　power　of　1.8　kW,　and　an　output　power　range　of　10%~100%　was　designed　and　set　up.　Computer　simulation　and　experimental　results　show　that　by　adjusting　the　resonance　parameters,　the　switching　frequency　is　basically　constant　at　140　kHz,　the　converter　does　not　enter　the　burst-mode　in　the　entire　power　output　range,　and　the　output　voltage　characteristics　are　good.　Moreover,　compared　with　the　traditional　LLC　circuit,　the　proposed　circuit　has　a　higher　conversion　efficiency.　©　2021,　Harbin　University　of　Science　and　Technology　Publication.　All　right　reserved.