A　circuit　structure　and　circuit　topologies　family　of　single　stage　combined　uninterruptible　AC-DC　converters　with　high　power　factor　based　on　Boost-Flyback　converter　are　proposed.　The　converter　which　is　constituted　of　a　full　bridge　rectifier　and　a　Boost-Flyback　converter　with　power　factor　correction,　uninterruptible　power　supply　and　fast　output　voltage　regulation,　can　transfer　one　AC　voltage　into　desired　output　DC　voltage.　The　three　operational　modes　(normal　operating　mode,　back-up　operating　mode,　charging　operating　mode),　steady　principle,　control　strategy,and　design　criterion　of　key　circuit　parameters　are　investigated.　The　test　results　are　given.　The　converter　has　the　advantages　of　single　stage　power　conversion,　uninterruptible　power　supply,　high　line　power　factor,　high　frequency　electrical　isolation　between　battery　and　line　or　load,　fast　regulation　speed　of　the　output　voltage,　small　size,　lower　weight,low　cost.　The　converter　can　be　used　application　field　in　the　telecom,　computer　industry　and　so