A　circuit　configuration　and　circuit　topologies　family　of　single-stage　parallely　connected　DC　uninterruptible　power　supplies　with　high　power　factor　are　proposed　in　this　paper.　The　kind　of　converter　is　constituted　of　a　full　bridge　rectifier　and　a　parallel　converter　with　power　factor　correction,　uninterruptible　power　supply　and　fast　output　voltage　regulation,　is　also　regarded　as　constitution　of　the　main　DC-DC　converter,　auxiliary　DC-DC　converter,　and　charger.　Taking　Buck-Boost　topology　as　an　example,　the　operational　modes,　steady　principle,　and　control　strategy　are　deeply　investigated,　and　the　design　criterion　of　key　circuit　parameters　are　given.　The　theoretical　analysis　and　test　results　have　demonstrated　that　this　kind　of　converter　has　the　advantages　of　single　stage　power　conversion,　true　on-line　uninterruptible　power　supply　for　load,　high　line　power　factor,　high　frequency　electrical　isolation　between　battery　and　line,　fast　regulation　speed　of　the　output　voltage,　without　fault　detection　and　mode　conversion　circuit,　small　size,　lower　weight,　and　low　cost.