J. Diaz

Power Supply for a High-Voltage Application

In this paper, the guidelines to design a high-voltage power converter based on the hybrid series parallel resonant topology, PRC-LCC, with a capacitor as output filter are established. As a consequence of the selection of this topology, transformer ratio, and therefore secondary volume, is reduced. The mathematical analysis provides an original equivalent circuit for the steady-state and dynamical behavior of the topology. A new way to construct high-voltage transformers is also proposed, pointing out the advantages and establishing an original method to evaluate the stray components of the transformer before construction. The way to make compatible the characteristics of both, topology and transformer is illustrated in the frame of a practical application. To demonstrate the feasibility of this solution, a high-voltage, high-power prototype is assembled and tested with good performance and similar behavior to the one predicted by the models. Experimental results are shown on this particular.

Dynamic and Steady-State Models for the PRC-LCC Resonant Topology With a Capacitor as Output Filter

In high-voltage DC power supplies (hundreds of kilovolts), avoiding the inductance in the output filter is an important asset. Thus, a capacitor as a unique component of that filter is preferable. On the other hand, a high-voltage step-up transformer shows a high capacitance in its secondary, which can be included in a resonant stage. Both capacitances, i.e., one from the filter and the other from the transformer, are separated by the output rectifier. When this rectifier is on, they are in parallel; when it is off, they are disconnected. A resonant stage where a very large capacitor appears and disappears several times in one period is not linear and has not been dynamically modeled before. This paper shows two simple models for the parallel-series (LCC-type parallel resonant converter) resonant topology with a capacitor as output filter. Its dynamics and steady state are studied and constitute an important help for any designer.

A microcontroller-based emergency ballast for fluorescent lamps

This paper presents a new emergency ballast for fluorescent lamps. The fundamental block is the microcontroller-based control circuit, which performs the supervision and control function. High-frequency electronics techniques are proposed for the high power factor battery charger and the lamp driver, which provides high luminous efficacy. In this way, size and weight have been minimized for the whole system. With the introduction of the microcontroller, the system has the capability of testing itself, checking its functional state, and displaying internal faults. Thus, the reliability of the system is improved and, concurrently, maintenance cost is decreased.

Intelligent and universal fast charger for Ni-Cd and Ni-MH batteries in portable applications

In this paper, a new fast charger is presented for Ni-Cd and Ni-MH batteries, which are the most frequently used in portable applications. In this charger, the control and supervision of the process has been entrusted to a microcontroller, which provides a powerful and intelligent tool to undertake complex tasks, and reduces the requested circuitry to the microcontroller itself and a few additional components. The resulting charger is able to work out the initial battery state (detecting deteriorated devices), decide the suitable way to charge it (ensuring a long cyclic life), and determine when the charge process must be finished. This way, the state of the battery is always controlled, preventing any damage to it and providing a fully protected operation mode. This paper summarizes the design and construction of the presented charger, as well as shows the experimental results obtained in the prototype tests.

A complete transformer electric model, including frequency and geometry effects

An electric model for transformers, including both frequency and geometry effects, is presented. From Maxwells equations an electric circuit which represents the transformer behavior is obtained. Expressions for calculating the circuit parameters from the winding layer geometry are given. The models inclusion in simulation programs and its limitations are discussed. Experimental results showing the accuracy of the model are provided.<<ETX>>

A new lossless power MOSFET driver based on simple DC/DC converters

A new kind of power-MOSFET driver has appeared: lossless or resonant drivers. Their main goals are the reduction of power consumption and protections against overvoltage in the gate terminal. In this paper, a new lossless driver is presented; its operation is based on the use of DC/DC converters to supply and to recover driving energy with a few components and easy design.<<ETX>>

Input current shaper based on the series connection of a voltage source and a loss-free resistor

A new input current shaper is proposed in this paper. The operating principle is based on the connection of a voltage source and a loss-free resistor (LFR) between the input rectifier and the bulk capacitor in a conventional switching mode power supply with no power-factor correction. Both the voltage source and the LFR are obtained as an additional output from the converters transformer. This additional output is a forward-type one with one extra inductor. With the final topology, a good tradeoff between capacitor voltage, recycling energy, and harmonic content can be established in order to comply with IEC 1000-3-2 specifications.

A new input current shaping technique using converters operating in continuous conduction mode

A new input current shaping technique has been proposed. Its operating principle is based on the connection of an additional DC output, obtained from the converters transformer, between the input rectifier and the bulk capacitor in a conventional switching-mode power supply with no power factor correction. This additional output is a forward-type one with one extra inductor, which provides an effective duty cycle modulated by the input current. Thus, the voltage-current characteristic of this output consists of a voltage source and a loss-free resistor, connected in such a way that they help the diodes of the line rectifier to conduct. The main difference with other input current waveshapers lies in the fact that the filter inductor of the additional output operates in continuous conduction mode. Thus, the current stress in the power transistor is minimized. With the final topology, a good trade-off between bulk capacitor voltage, re-cycling energy, power factor and harmonic content can be established in order to comply with the IEC 1000-3-2. Many aspects in the design and operation of this type of converter are analyzed in this paper.

A very simple DC/DC converter using piezoelectric transformer

Piezoelectric transformers (PTs) have lately been looked upon as an attractive solution to reduce size and weight in AC/DC converters. This paper presents a topology that includes such a device while minimizing the number of additional components required for an adequate performance. An 8-watt AC/DC adapter (110 V/sub AC/, 12 V/sub DC/) operating at frequencies around 500 kHz is obtained using this topology.

Development of a wireless sensor network for individual monitoring of panels in a photovoltaic plant.

With photovoltaic (PV) systems proliferating in the last few years due to the high prices of fossil fuels and pollution issues, among others, it is extremely important to monitor the efficiency of these plants and optimize the energy production process. This will also result in improvements related to the maintenance and security of the installation. In order to do so, the main parameters in the plant must be continuously monitored so that the appropriate actions can be carried out. This monitoring should not only be carried out at a global level, but also at panel-level, so that a better understanding of what is actually happening in the PV plant can be obtained. This paper presents a system based on a wireless sensor network (WSN) that includes all the components required for such monitoring as well as a power supply obtaining the energy required by the sensors from the photovoltaic panels. The system proposed succeeds in identifying all the nodes in the network and provides real-time monitoring while tracking efficiency, features, failures and weaknesses from a single cell up to the whole infrastructure. Thus, the decision-making process is simplified, which contributes to reducing failures, wastes and, consequently, costs.