With　advances　in　science　and　technology，power　density　has　become　a　critical　key　benchmark　for　power　adapters　with　power　delivery(PD)　protocols.　Among　traditional　PD　power　adapters，input　electrolytic　capacitors　occupy　a　significant　proportion　of　total　volume，limiting　further　improvements　in　power　density.　To　address　this　issue，a　novel　PD　power　adapter　circuit　without　input　electrolytic　capacitors　is　proposed.　This　innovative　design　replaces　the　bulky　input　electrolytic　capacitors　found　in　traditional　flyback　converters　by　incorporating　an　energy　compensation　module.　This　energy　compensation　module　is　composed　of　an　energy　storage　circuit　and　a　Buck　circuit，　balancing　the　pulsating　power　between　input　and　output.　Furthermore，the　solution　effectively　suppresses　output　voltage　ripple.　This　article　provides　a　detailed　analysis　of　the　proposed　circuit　topology　and　its　working　principle.　A　feed-forward-based　single-cycle　control　mechanism　tailored　to　this　topology　is　introduced，supported　by　a　comprehensive　control　strategy　that　integrates　power　balance　control　and　output　constant-voltage　control.　Key　parameters　for　the　circuit　are　designed.　Finally，a　40　W　PD　power　adapter　experimental　platform　was　built　to　validate　the　effectiveness　of　the　proposed　scheme.　The　experimental　results　indicate　that　the　circuit　scheme　reduces　the　output　voltage　ripple　to　below　2%　and　eliminates　the　input　electrolytic　capacitors，effectively　enhancing　the　power　density.　©　2025,　Tianjin　University.　All　rights　reserved.