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This paper presents a unified second-stage LC filter applied in the three-state switching cell buck–boost converter, which provides current and voltage with low ripple and low noise. The unified second-stage filter promotes a reduction in the number of devices while maintaining the filtering performance of the converter, with second-stage LC filters at the input and at the output. Moreover, the unified filter, when associated with a three-state switching cell buck–boost converter, allows a size reduction of filter devices, especially for designs with duty cycle range around 1/2. Furthermore, the unified filter arrangement provides nondissipative clamping of switching devices and reduce the system order when compared to the converter with second-stage LC filters. In this paper, the static and dynamic characteristics of the proposed converter in continuous conduction mode (CCM) are reported. Experimental data were obtained from a laboratory prototype with an input range of 32 $\sim$ 72 V, constant output of 48 V, a load of 150 W, and switching frequency of 45 kHz. The measured efficiency for the rated load was 97% for maximum input voltage. A comparison of the size and performance of the proposed filter with the topology that uses second-stage LC filters at the input and at the output is also presented. [ABSTRACT FROM AUTHOR]

In this paper a step-up/step-down isolated dc–dc converter referred to as a three-phase flyback push–pull dc–dc converter is presented. The power circuit is constituted by a pair of coupled inductors, a three-phase transformer, a capacitor, three switching transistors and three power diodes. The proposed converter offers the advantages of compact passive devices, low conduction power losses, full duty cycle range (0–100%), and inherent protection against transformer saturation. Furthermore, filter sizes are minimized to duty cycles of around 1/3 and 2/3. These characteristics makes this converter suitable for many applications, especially in low-voltage high-power applications such as telecommunications power supply, battery chargers, and renewable power systems. The operating principle and the idealized mathematical analysis in continuous conduction mode are presented. Experimental data were obtained from a laboratory prototype with an input voltage of 125 V, output voltage of 100 V, load power of 1000 W, and switching frequency of 42 kHz. The measured prototype efficiency was 94% for full load and 96% for 400 W. [ABSTRACT FROM AUTHOR]