Patent EP-3857695-A1 (EP)
Title: Power supply cell and power supply system using the same
Inventor: YUEN KUENFAAT
IPC: H02M3/145
Filed: 2018-09-27
Abstract: It is therefore an objective of the invention 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 positive terminal and first negative terminal, a second power conversion circuit operative to output a second DC voltage across its second positive terminal and second negative terminal, a first controllable unidirectional semiconductor switch operative to generate a first conduction path from the first positive terminal of the first power conversion circuit to the second negative terminal of the second power conversion circuit, a first unidirectional semiconductor switch operative to generate a second conduction path from the first positive terminal of the first power conversion circuit to the second positive terminal of the second power conversion circuit, a second unidirectional semiconductor switch operative to generate a third conduction path from the first negative terminal of the first power conversion circuit to the second negative terminal of the second power conversion circuit, a first low-pass filter, a second low-pass filter, a third low-pass filter and a controlling unit. The controlling unit is operative to: issue turn-on 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 first low-pass filter via the first conduction path, the second low-pass filter and the third low-pass filter; or issue turn-off signal to the first controllable unidirectional semiconductor switch so that the first power conversion circuit and the second power conversion circuit supply currents to the first low-pass filter in parallel via the second conduction path and the second low-pass filter together with the third conduction path and the third low-pass filter. The first low-pass filter can help smooth an 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 output voltage across the first low-pass filter and current range of the power supply cell can be enlarged smoothly and linearly with the help of the first low-pass filter. In addition, when the first controllable unidirectional semiconductor switch is turned on, the second low-pass filter and the third low-pass filter are electrically coupled in series by the first controllable unidirectional semiconductor switch. Then, the circuit loop impedance is increased to the sum of the second low-pass filter and the third low-pass filter. It follows that the filtering power of the filter circuit which formed by the second low-pass filter and the third low-pass filter is enhanced. In the other word, to achieve the same filtering power as the normal LC filter (no series or parallel connection of the inductors), the proposed solution require less inductance of the inductors. It can reduce the size and cost of the required inductor in the circuit