A DC converter includes a non-isolated conversion module and an isolated conversion module. The non-isolated conversion module is implemented based on a redundant structure and has a first power conversion loop, a second power conversion loop, and an energy storage element. The first and second power conversion loops are connected and share the energy storage element. The energy storage element is further connected to an input terminal of the isolated conversion module. The first and second conversion loops of the non-isolated conversion module convert DC power outputted from two battery sets and output the converted power to the isolated conversion module. The isolated conversion module further supplies DC power to a load. Accordingly, power supply systems using the foregoing DC converter can reduce the number of transformer therein and thus size reduction of the power supply system can be achieved.