Circuit　topologies　of　single-stage,　single-stage　combined,　single-stage　paralled　uninterruptible　AC-DC　converters　with　high　power　factor　are　proposed　based　on　presenting　research　present　states　of　the　single-stage　uninterruptible　AC-DC　converters.　This　kind　of　AC-DC　converters,　which　is　constituted　of　full-bridge　rectifier　and　multifunctional　integrated　flyback　converter,　can　realize　uninterruptible　power　supply,　power　factor　correction,　and　dc　output　voltage＇s　regulation.　Three　operating　modes　of　this　kind　of　AC-DC　converters　are　investigated,　and　principle　experimental　results　are　given.　This　kind　of　AC-DC　converters　have　the　advantages,　such　as　simple　topology,　high　power　density,　high　conversion　efficiency,　and　high　power　factor,　uninterruptible　power　supply,　electrical　isolation　between　battery　and　AC　line,　and　can　be　used　application　field　in　the　telecom,　computer　and　medical　industry.　The　properties　of　the　DC　switching　power　supplies　can　be　greatly　improved　by　using　the　circuit　configuration　of　single-stage　uninterruptible　AC-DC　converters　instead　of　that　of　traditional　multi-stage　cascade　uninterruptible　AC-DC　converters.