It is an objective to provide a power supply cell of a power supply system and a power supply system using the same. The power supply cell includes a first power conversion circuit operative to output a first DC voltage across its first output positive terminal and first output negative terminal, a second power conversion circuit operative to output a second DC voltage across its second output positive terminal and second output negative terminal, a first controllable unidirectional semiconductor switch operative to generate a first conduction path from the first output positive terminal of the first power conversion circuit to the second output negative terminal of the second power conversion circuit, a first unidirectional semiconductor switch operative to generate a second conduction path from the first output positive terminal of the first power conversion circuit to the second output positive terminal of the second power conversion circuit, a second unidirectional semiconductor switch operative to generate a third conduction path from the first output negative terminal of the first power conversion circuit to the second output negative terminal of the second power conversion circuit, a first low-pass filter and a controlling unit operative to issue turn-on signal or turn-off signal to the first controllable unidirectional semiconductor switch so that the first power conversion circuit and the second power conversion circuit supply current to the low-pass filter via the first conduction path or both of the second conduction path and the third conduction path. The first low-pass filter can help smooth the power supply cell's output voltage and current in order to achieve a relatively wide linearly constant output power range. By controlling the ratio of series and parallel connection in a switching cycle of the switching frequency by the switching arrangement, both the output voltage and current range of the power supply cell can be enlarged smoothly and linearly with the help of the first low-pass filter.