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- SRAM performance sensorPublication . Semião, Jorge; Santos, Luis; Santos, Marcelino B.As technology advances and becomes increasingly smaller in scale, it makes performance and reliability a constant problem. Effects such as process variations (P), power-supply voltage variations (V), temperature variations (T) and aging (A) variations (PVTA - Process, Voltage, Temperature and Aging) are key parameters that affect circuit's performance and reliability. In today's SoC (System-on-Chip), the memory capacity is gaining importance, due to the need to store more and more data in the chips. The Complementary Metal Oxide Semiconductor (CMOS) memories are the most used in the integrated circuits, within the several types of memories. In this paper, a new performance sensor for SRAM memories is proposed. The purpose is to signalize when PVTA variations change performance above a certain threshold limit, jeopardizing memory operation and signal integrity. Sensor's sensibility to PVTA variations can be changed in run-time, which allows the sensor to be tuned during circuit's life time. Another important feature is that it can be applied locally in key locations, to monitor the online operation of the memory, or globally, by monitoring a dummy memory in pre-defined conditions.
- Multiple-output DC–DC converters: applications and solutionsPublication . Litrán, Salvador P.; Durán, Eladio; Semião, Jorge; Díaz-Martín, CristianMultiple-output DC–DC converters are essential in a multitude of applications where different DC output voltages are required. The interest and importance of this type of multiport configuration is also reflected in that many electronics manufacturers currently develop integrated solutions. Traditionally, the different output voltages required are obtained by means of a transformer with several windings, which are in addition to providing electrical isolation. However, the current trend in the development of multiple-output DC–DC converters follows general aspects, such as low losses, high-power density, and high efficiency, as well as the development of new architectures and control strategies. Certainly, simple structures with a reduced number of components and power switches will be one of the new trends, especially to reduce the size. In this sense, the incorporation of devices with a Wide Band Gap (WBG), particularly Gallium Nitride (GaN) and Silicon Carbide (SiC), will establish future trends, advantages, and disadvantages in the development and applications of multiple-output DC–DC converters. In this paper, we present a review of the most important topics related to multiple-output DC–DC converters based on their main topologies and configurations, applications, solutions, and trends. A wide variety of configurations and topologies of multiple-output DC–DC converters are shown (more than 30), isolated and non-isolated, single and multiple switches, and based on soft and hard switching techniques, which are used in many different applications and solutions.
- Multiple-output switched-capacitor DC-DC combination converters for IoT applicationsPublication . Semiao, J.; Duran, E.; Litran, S. P.; Ferrera, M. B.This paper presents and describes switched-capacitor DC-DC combination converters with a single input and multiple outputs, with step-down and step-up voltage ratios. The combination converters provide two or three different DC outputs (depending on the combination), with different conversion ratios. The main advantage of the proposed converters is the low number of components used in the combination (two-output configurations require two link capacitors, and three-output configurations require three link capacitors) and two complementary phase clocks, which may reduce size and manufacturing costs for many applications. The DC-DC combination converters are designed to be fully integrated, and were implemented in a 65nm CMOS technology. The analysis of the proposed configurations for different performance modes and load conditions is presented, and simulation results show that these combination converter topologies are suitable for multiple-output switched-capacitor DC-DC converters with multiple conversion ratios.
- Single-switch non-isolated resonant DC-DC converter for single-input dual-output applicationsPublication . Díaz-Martín, Cristian; Durán, Eladio; Litrán, Salvador P.; Álvarez, José Luis; Semião, JorgeThis paper describes a new configuration of Cuk and SEPIC (Single-Ended Primary Converter) ZVS-QR (zero-voltage switching quasi-resonant) combination DC-DC converter for bipolar output with a single switch. The proposed topology employs a single ground-referenced power switch, which simplifies the gate drive design with a single L-C resonant network and provides a bipolar output voltage with good regulation, acceptable efficiency and a step-down/up conversion ratio. This configuration provides dual-output voltage by switching the power switch to zero voltage, which is an interesting alternative for many applications where small size, light weight and high power density are very important aspects. In order to verify its performance, a SEPIC–Cuk Combination ZVS-QR prototype with a cost-effective commercial resonant controller was designed and tested. The experimental results show that the proposed combined topology is suitable for Single-Input Dual-Output (SIDO) applications.
- Autonomous temporal pseudo-labeling for fish detectionPublication . Veiga, Ricardo; Exposito Ochoa, Iñigo; Belackova, Adela; Bentes, Luis; Parente Silva, João; Semiao, J.; Rodrigues, JoãoThe first major step in training an object detection model to different classes from the available datasets is the gathering of meaningful and properly annotated data. This recurring task will determine the length of any project, and, more importantly, the quality of the resulting models. This obstacle is amplified when the data available for the new classes are scarce or incompatible, as in the case of fish detection in the open sea. This issue was tackled using a mixed and reversed approach: a network is initiated with a noisy dataset of the same species as our classes (fish), although in different scenarios and conditions (fish from Australian marine fauna), and we gathered the target footage (fish from Portuguese marine fauna; Atlantic Ocean) for the application without annotations. Using the temporal information of the detected objects and augmented techniques during later training, it was possible to generate highly accurate labels from our targeted footage. Furthermore, the data selection method retained the samples of each unique situation, filtering repetitive data, which would bias the training process. The obtained results validate the proposed method of automating the labeling processing, resorting directly to the final application as the source of training data. The presented method achieved a mean average precision of 93.11% on our own data, and 73.61% on unseen data, an increase of 24.65% and 25.53% over the baseline of the noisy dataset, respectively.
- Single-switch bipolar output DC-DC converter for photovoltaic applicationPublication . Litrán, Salvador P.; Durán, Eladio; Semião, Jorge; Barroso, Rafael S.Bipolar DC grids have become an adequate solution for high-power microgrids. This is mainly due to the fact that this configuration has a greater power transmission capacity. In bipolar DC grids, any distributed generation system can be connected through DC-DC converters, which must have a monopolar input and a bipolar output. In this paper, a DC-DC converter based on the combination of single-ended primary-inductor converter (SEPIC) and C´ uk converters is proposed, to connect a photovoltaic (PV) system to a bipolar DC grid. This topology has, as main advantages, a reduced number of components and a high e ciency. Furthermore, it can contribute to regulate/balance voltage in bipolar DC grids. To control the proposed converter, any of the techniques described in the literature and applied to converters of a single input and single output can be used. An experimental prototype of a DC-DC converter with bipolar output based on the combination of SEPIC and C´ uk converters was developed. On the other hand, a perturb and observe method (P and O) has been applied to control the converter and has allowed maximum power point tracking (MPPT). The combined converter was connected in island mode and in parallel with a bipolar DC microgrid. The obtained results have allowed to verify the behavior of the combined converter with the applied strategy.
- An open hardware electronic controller for motorized rotary injection valves used in Flow Injection AnalysisPublication . Mozo, J. D.; Otero, J. I.; Durán, E.; Semião, JorgeThis work presents the design, development and the implementation of a motorized injection valve used in Flow Injection Analysis. The built prototype has been developed based on the open hardware emergent philosophy, software and firmware, thus helping the development of a free and independent science. This policy creates a platform of open projects that feed each other, contributing to scientific and technological development while sharing knowledge. The proposed design project can be modified to implant it in other devices or projects according to the needs of each one. Also, the open project can be a great help as teaching material in Universities, since open hardware projects are fully described and documented.
- A Zeta-CSC converter combination for single-input and bipolar outputPublication . Litran, S. P.; Duran, E.; Ferrera, M. B.; Semiao, J.; Barroso, R. S.This paper presents a DC-DC converter of one input and one bipolar output. The converter has been obtained from the combination of two basic converters of one input and one output. Thus, the proposed configuration is the result of the combination of a CSC (Canonical Switching Cell) converter and a Zeta converter. A common feature of these converters is they have the same conversion relation. The input stage formed by the switching device and an inductance is shared by both converters. On the other hand, the output of the CSC converter is inverted with respect to its input and the output of Zeta converter is non-inverted, so this combination results in a bipolar type output. With the proposed topology it is possible to reduce the number of components and eliminate the need for synchronization of several switching devices. The converter has been analyzed in a steady state and the most significant operating equations have been deduced. A simulation platform has been developed in the MATLAB-Simulink, which has allowed the behavior of the converter to be verified.
- A distributed load scheduling mechanism for micro gridsPublication . Monteiro, J. M.; Eduardo, J.; Cardoso, Pedro J. S.; Semiao, J.Several protocols have recently been defined for smart grids that enable the communication between electric devices and energy management systems. While these protocols and architectures can already be applied in different fields of micro grids, it is still not clear how the distributed resources and constraints of such electrical grids can be managed in an optimum way. In order to achieve a reduction in electricity costs and maximizing investments made in renewable sources, an optimization mechanism should be used to perform load scheduling, considering different variables such as forecasted power generation curve from renewable sources, different tariffs' rates, electric circuit constraints, user restrictions and correspondent comfort levels. Given these considerations, this work defines and evaluates a distributed micro grid resource management architecture and protocol which is able to optimize load scheduling while considering all the mentioned restrictions and parameters. The proposed architecture was implemented on a multi-agent simulator and the performed tests show that significant reductions in electricity cost can be achieved using this methodology. © 2014 IEEE.
- Analysis of converters with bipolar output for DC microgridPublication . Litran, S. P.; Duran, E.; Barroso, R. S.; Semiao, J.; Ferrera, M. B.Bipolar DC networks have been shown as a suitable solution for low voltage (LV) energy distribution. This paper presents the advantages and disadvantages that they have with respect to other topologies, from the point of view of their implementation, efficiency in the use of energy and its ability to connect large loads. On the other hand, for this type of networks the use of DC-DC converters is required to connect the different sources of distributed generation with guarantees so that the network as a whole can be managed automatically (Smartgrid), both in isolated mode and connected to the conventional AC network. In this line, three configurations of non-isolated DC-DC converters, of a bipolar input and output are presented. That allows connecting DC sources to the network in a controlled way. The behaviour of the converters is verified through a simulation platform based on MATLAB-Simulink and the experimental results will be presented.