Alfonso Conesa

Modeling of linear-assisted DC-DC converters

This paper shows the modeling of a linear-assisted or hybrid (linear & switching) DC-DC converters. In this kind of converters, an auxiliary linear regulator is used, which objective is to cancel the ripple at the output voltage and provide fast responses for load variations. On the other hand, a switching converter, connected in parallel with the linear regulator, allows to supply almost the whole output current demanded by the load. The objective of this topology is to take advantage of the suitable regulation characteristics that series linear voltage regulators have, but almost achieving the high efficiency that switching DC-DC converters provide. Linear-assisted DC-DC converters are feedback systems with potential instability. Therefore, their modeling is mandatory in order to obtain design guidelines and assure stability of the implemented power supply system.

Linear-assisted DC-DC converter based on CMOS technology

This article shows the design of an on-chip CMOS implementation for an alternative topology to classic switching DC-DC power converters. In the presented technique, an auxiliary linear regulator is used to cancel the output voltage ripple and provides fast responses for load and line variations. On the other hand, a switching converter, connected in parallel, allows supplying almost the whole output current demanded by the load. The objective of this linear-assisted converter or hybrid topology is to achieve a high efficiency of switching converters, with suitable load and line regulation features, typical of linear regulators. In order to implement on-chip power supply systems and on-chip power management systems with low- to-medium current consumption, this structure has good features. In this kind of on-chip applications, CMOS is the current prevailing technology. Thus, the article shows a possible implementation of a linear-assisted converter based on a 0.8-mum CMOS technology.

Inverter power sizing considerations in grid-connected PV systems

This work is devoted to establish preliminary criteria helping in the choice of a central inverter power sizing in grid-connected PV systems in order to maximize the yearly energy injected to the grid. These criteria come from an estimation of the injected energy by means of a set of Matlabreg-based simulations involving a simulation-oriented model of the PV conversion chain, the environmental data of several PV Spanish sites as well as the PV installation mounting type characteristics. The simulation results show that the current practice of under-sizing the inverter maximum power with respect to the PV generator nominal power may not be the best choice in terms of yearly produced energy and also evidence the strong impact of the PV generator operating temperature in the choice of the optimal inverter power sizing.

Dynamic analysis of hybrid DC-DC converters

This paper shows the analysis and implementation of a hybrid DC-DC power converter. The proposed topology consists of a series linear voltage regulator in parallel with a switching step-down converter. This topology can provide small ripple at the output voltage, fast responses for load variations and high efficiency for high load current conditions. In the hybrid structures there is not a classical feedback loop as in DC-DC converters, but they are feedback systems too. Therefore, their small- signal analysis is important to assure stability of the implemented power supply system. From the analysis proposed we deduce the critical components that induce instability to the converter and how to improve the final design.

The serial resonant converter with controlled rectifier stage

This paper introduces and analyzes a new serial resonant converter derived from the classical SRC, with controlled switches at the rectifier stage. The output current is controlled and regulated by the above mentioned stage, allowing to keep the resonant magnitudes bounded. We perform the first harmonic approximation analysis to the structure and obtain the state space model solution. Experimental results from a prototype are also presented to support the developed analysis

Low consumption Flux-gate transducer for AC and DC high-current measurement

This work presents the design and implementation of a transducer system for the measurement of AC and DC high-current using the flux compensation technique in the measurement transformer, also called Flux- gate technology. The system can measure currents greater than 700 A (peak value) with a 100 kHz bandwidth measured at -3 dB. This equipment has been developed under the agreement of collaboration subscribed between the EUETIB-CEIB of the Technical University of Catalonia (UPC) and Group PREMO S.A. The Group PREMO S.A. is a Spanish company specialized in high-quality inductive components and leader in this sector.

Linear-assisted converter with constant switching frequency

This article shows the proposal of a linear-assisted converter or linear-&-switching hybrid converter with a constant switching frequency. The control loop of the system is based on the current-mode technique. The main disadvantage of a converter with current-mode control is the inherent instability of the loop when switch duty ratios are greater than 0.5. In order to make stable the proposed linear-assisted converter, the article shows the technique based on a slope compensation.