High　power　density　is　the　key　to　power　adapter　miniaturization,　and　it　is　also　one　of　the　research　hotspots　of　the　power　adapters.　Aiming　at　the　problem　that　the　input　electrolytic　capacitor　affects　the　volume　of　the　power　adapter,　a　topological　structure　of　the　power　adapter　without　input　electrolytic　capacitor　is　proposed　in　this　paper.　This　topology　adds　an　energy　compensation　loop　based　on　the　flyback　converter.　The　balance　between　input　instantaneous　power　and　output　power　is　realized　by　controlling　the　charge　and　discharge　of　the　energy　storage　capacitor　in　the　energy　compensation　loop　to　reduce　the　low　output　voltage　ripple.　The　working　principle　and　switching　mode　of　the　topology　is　analyzed　in　detail,　the　key　parameters　of　the　circuit　are　designed　for　the　proposed　circuit　topology,　and　a　control　strategy　for　the　circuit　topology　based　on　one-cycle　control　is　proposed.　Finally,　the　circuit　topology　and　control　principle　is　verified　by　simulation　at　60W.　The　simulation　results　show　that　the　proposed　circuit　scheme　can　reduce　the　output　voltage　ripple　to　less　than　0.3%　at　60W,　and　eliminate　the　input　electrolytic　capacitor,　which　greatly　reduces　the　volume　of　the　power　adapter.　©　2022　IEEE.