This study presents single-input double-output unidirectional and bidirectional dc-dc buck converters, for applications that demand two dc-controlled output voltages. The proposed converters present a component count reduction and it is considered as a monolithic device with two output voltages generated by the same power converter. The main advantages of the proposed converters are reduction of costs and better power losses distribution among the semiconductor devices. Besides the proposal of suitable power converters, this study presents their models, control strategies, modulation approaches and design specification. The selected simulated and experimental results are presented as well.
The measurement of subtle morphologic beat-to-beat variability in the electrocardiogram (ECG)/vectorcardiogram (VCG) is complicated by the presence of noise which is caused by, e.g., respiration and muscular activity. A method was recently presented which reduces the influence of such noise by performing spatial and temporal alignment of VCG loops. The alignment is performed in terms of scaling, rotation and time synchronization of the loops. Using an ECG simulation model based on propagation of action potentials in cardiac tissue, the ability of the method to separate morphologic variability of physiological origin from respiratory activity was studied. Morphologic variability was created by introducing a random variation in action potential propagation between different compartments. The results indicate that the separation of these two activities can be done accurately at low to moderate noise levels (less than 10 microV). At high noise levels, the estimation of the rotation angles was found to break down in an abrupt manner. It was also shown that the breakdown noise level is strongly dependent on loop morphology; a planar loop corresponds to a lower breakdown noise level than does a nonplanar loop.
This paper proposes multilevel topologies based on the concept of nested arrangement. Such topologies are called nested multilevel converters since the central point of the legs are connected at the same point, with the external legs involving the internal ones. Nested configurations present advantages as compared to the equivalent NPC topologies in terms of reduced number of diodes and consequently higher efficiency. In addition to proposing a new family of power electronics converters, this paper presents an optimized PWM strategy that allows synthesizing voltage waveforms with higher quality, a losses comparison with the NPC topology, and a general comparison with other topologies proposed in the technical literature. Simulated and experimental results are presented to validate the theoretical expectations. 0885-8993 (c)
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