This paper addresses the performance of the bidirectional dual active bridge (DAB) converter. One of the advantages of the DAB is the possibility to achieve the zero-voltage switching (ZVS) operation in all the switches of this converter. However, the ZVS operation range can be lost for light loads, especially if high voltage is required in at least one of the DAB ports and the phase-shift control is used to regulate the power processed by the converter. Theoretically simple averaged and small-signal models are presented for the DAB converter. Using the study presented in this paper, the boundaries of the ZVS operation can be easily evaluated. The proposed models and analysis of the ZVS boundaries allow the proposal and evaluation of two different design strategies with different purposes: on the one hand, increasing the ZVS operation range and, on the other, improving efficiency at full load. Moreover, some techniques are presented for increasing the ZVS operation range and improving the efficiency of the DAB at full load (both using phase-shift control) employing the aforementioned analysis to obtain certain design criteria and conclusions. Finally, the proposed models, design strategies, and techniques to improve the performance of the DAB are experimentally tested using a 1-kW prototype with input and output voltages of 48 and 400 V, respectively.

The increase demand of an intermediate storage of electrical energy in battery systems, in particular due to the use of renewable energy, has resulted in the need of bidirectional DC/DC power converters with galvanic isolation. Uninterruptible Power Supplies (UPS), battery charging systems, photovoltaic equipment and auxiliary power supplies in traction applications are examples of some fields of application of this kind of converters. A Dual Active Bridge (DAB) bidirectional DC/DC converter is a topology with the advantages of decreased number of devices, soft-switching commutations, low cost, and high efficiency. The use of this topology is proposed for applications where the power density, cost, weight, and reliability are critical factors. In the present paper the steady-state analysis of the converter has been carried out, giving some guidelines for the design (considering soft switching limits and the amount of reactive current) and a small-signal model of the topology. Simulations and experimental results are also presented.

This paper describes a modular architecture based on the dual-active bridge (DAB) converter in input-series-output-parallel (ISOP) connection. This work is focused on the input voltage sharing to ensure a proper operation of each module by means of an active control of input and output voltages. A small-signal model of the modular architecture is proposed and a decoupled control loops' scheme is used to implement the control strategy. An experimental setup has been built in order to validate the model of the DAB converter in ISOP connection and the proposed control strategy, taking different operating conditions and constructive parameter values into account.

This paper presents a new control strategy for power factor correctors (PFCs) that are used to drive high-brightness LEDs. This control strategy is extremely simple and is based on the use of a conventional peak-current-mode controller with a suitable selection of the compensation ramp waveform. Neither an analog multiplier nor an input voltage sensor is needed to achieve quasi-sinusoidal line waveforms at nominal conditions and full load. If the converter belongs to the flyback family (flyback, buck-boost, SEPIC, Cuk and Zeta), the line waveform appears notably distorted if the compensation function is a linear ramp, but becomes almost sinusoidal if the linear ramp is substituted by a properly chosen exponential function. The line waveform is slightly distorted when the load varies or when the converter works under either overvoltage or undervoltage conditions. However, the waveform maintains a very high power factor (PF) even under these conditions. Moreover, the line current is cycle-by-cycle-controlled due to the peak-current-mode control, and hence, the input-current feedback loop is extremely fast, thereby allowing this type of control to be used with high-frequency lines (above 400 Hz).

Light-Emitting Diodes (LEDs) are coming strongly into the lighting market due to their advantages over conventional lighting solutions: energy efficient, controllable in both light and color, long lifetime, lack of a warm-up period and high power density. Some of these advantages will make LED light sources to be more than just a lightbulb, being able to transmit data, control light color, hue and intensity or even detect people in indoor environments. Nevertheless, these advantages attributed to LED capabilities are, in reality, achieved thanks to the LED driver. The present work reviews the current state-of-the-art strategies to drive LEDs from ac power grids with special emphasis into removing the most limiting component from the point of view of the lifetime, which is the electrolytic capacitor, while achieving a flicker-free performance of the light output of the LED driver. Moreover, it focuses on analyzing the required regulations, challenges and applicability of LED drivers in both single-phase and three-phase ac power grids.