Targeting　the　problem　of　low　output　voltage　of　renewable　energy　sources　such　as　photovoltaic　and　fuel　cells,　a　novel　extendable　high　boost　quadratic　dc-dc　converter　based　on　Cockcroft-Walton　voltage　multiplier　is　proposed　in　this　article.　An　inductor　is　designed　in　the　converter　to　be　connected　to　the　input　power　supply,　which　effectively　suppresses　the　input　current　ripple　and　thus　reduces　the　damage　to　the　input　dc　source.　In　addition,　a　three-winding　coupled　inductor　is　integrated　in　the　converter,　which　allows　the　boost　capability　to　be　improved.　However,　the　use　of　the　coupled　inductor　destroys　the　voltage　clamp　loop　of　the　switch,　and　the　voltage　spikes　generated　by　the　leakage　inductance　seriously　threaten　the　reliability　of　the　converter　operation.　To　solve　this　problem,　the　Cockcroft-Walton　voltage　multiplier　is　creatively　introduced,　which　not　only　perfectly　solves　the　problem　caused　by　the　leakage　inductance,　but　also　makes　the　converter　extendable　and　the　voltage　gain　adjustment　more　flexible.　The　topological　derivation　and　steady-state　operation　have　been　carried　out.　A　detailed　small-signal　analysis　and　design　considerations　have　been　presented.　Comparisons　with　converters　of　the　same　type　have　been　studied.　Finally,　the　effectiveness　of　the　proposed　converter　was　verified　with　a　200　W　prototype.