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The authors compare and evaluate 1) the traditional frequency-control dimming method and 2) a recently-patented voltage-control dimming method in electronic ballasts for fluorescent lamps. The power factor, energy efficiency, electronic loss, efficacy (lumen/W), and crest factor of 2 x 36 W electronic ballasts based on these two dimming methods are recorded and compared over a wide dimming range. It is found that the voltage dimming control approach is much better than the frequency control method in most of the compared aspects as the lamp is dimmed. In particular, voltage dimming approach has much higher energy efficiency and lumen per watt than the frequency control one. Unlike the frequency dimming method, voltage dimming control has a distinctive feature in that its electronic loss decreases with decreasing lamp power. Index Terms--Dimmable electronic ballasts, dimming methods.

A novel technique for efficiently extracting maximum power from photovoltaic (PV) panels is presented. The power conversion stage, which is connected between a PV panel and a load or bus, is a SEPIC or Cuk converter or their derived circuits operating in discontinuous inductor--current or capacitor--voltage mode. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency and comparing the ac component and the average value of the panel terminal voltage. Apart from not requiring any sophisticated digital computation of the panel power, the proposed technique does not approximate the panel characteristics and can globally locate the MPP under wide insolation conditions. The tracking capability has been verified experimentally with a 10 W solar panel under a controlled experimental setup. Performances under the steady state and in the large-signal change of the insolation level will be given. Index Terms--DC-DC power conversion, maximum-power-point tracking, photovoltaic.

This paper presents a generalized technique for computation of cycle state-variable sensitivity matrix of pulse-width-modulated (PWM) dc/dc converters. It determines the sensitivity of the state variable variation, with the inclusion of the effects of changing the topology duration on the sensitivity matrix. A basic sensitivity graph for each circuit topology is derived. By cascading corresponding graphs, a sensitivity matrix of multiple topologies is formulated. The correctness of the proposed method is compared with other methods in the performance of the steady-state determination and stability analysis. Index Terms--Circuit sensitivity analysis, circuit simulation, power electronics, switching circuits.

This paper presents a technique for calculating the ac line-to-output and control-to-output transfer characteristics of dc/dc converters, in which the time instants switching from one topology to the next one are a priori unknown and are determined by threshold conditions (i.e., by the time evolution of the converter waveforms). Describing functions are defined for small perturbations in either the input voltage or the control signal. After injecting a sinusoidal perturbation at the frequency of interest into the converter, the fundamental component of the output spectrum is determined. The describing functions are thus evaluated and provide the required ac transfer characteristics. The proposed method is integrated with a previously developed time-domain simulation algorithm, which is based on monitoring the switches positions, allowing the simulator to find automatically the switching instants and topological sequence of operation. Different examples are illustrated, including a classical pulse-width-modulated (PWM) converter, a current-programmed PWM regulator, and a switched-capacitor converter. The simulated results are compared with the experimental measurements and the results in the available literature. Index Terms--Circuit simulation, power electronics, switching circuits.

This paper presents the design and analysis of a low-profile multistage current-controlled switched-capacitor (SC) step-down dc/dc converter. The converter not only exhibits all advantages of classical SC converters, but also features good regulation capability and continuous input current waveform, resulting in low conducted electromagnetic interference with the supply network. The concept of energy transfer is achieved by paralleling the input and output of two step-down converter cells and operating them in antiphase. The voltage conversion ratio is determined by controlling the charging trajectories of the capacitors in each cell. As the circuit is unnecessary to use any inductive elements, possibilities of integrated circuit fabrication and high power density are promising. By applying the state-space averaging technique, a third-order state-space model for an n-stage converter is derived. Static and small-signal dynamic behaviors of the converter are investigated. A 70-W 48-V/12 V converter is implemented. Analytical predictions are verified with experimental measurements. Index Terms--DC/DC power conversion, switched capacitor circuits, switched circuits, switched-mode power supplies.

Particle swarm optimization (PSO) is predominately used to find solutions for continuous optimization problems. As the operators of PSO are originally designed in an n-dimensional continuous space, the advancement of using PSO to find solutions in a discrete space is at a slow pace. In this paper, a novel setbased PSO (S-PSO) method for the solutions of some combinatorial optimization problems (COPs) in discrete space is presented. The proposed S-PSO features the following characteristics. First, it is based on using a set-based representation scheme that enables S-PSO to characterize the discrete search space of COPs. Second, the candidate solution and velocity are defined as a crisp set, and a set with possibilities, respectively. All arithmetic operators in the velocity and position updating rules used in the original PSO are replaced by the operators and procedures defined on crisp sets, and sets with possibilities in S-PSO. The S-PSO method can thus follow a similar structure to the original PSO for searching in a discrete space. Based on the proposed S-PSO method, most of the existing PSO variants, such as the global version PSO, the local version PSO with different topologies, and the comprehensive learning PSO (CLPSO), can be extended to their corresponding discrete versions. These discrete PSO versions based on S-PSO are tested on two famous COPs: the traveling salesman problem and the multidimensional knapsack problem. Experimental results show that the discrete version of the CLPSO algorithm based on S-PSO is promising. [ABSTRACT FROM AUTHOR]

The authors compare and evaluate 1) the traditional frequency-control dimming method and 2) a recently-patented voltage-control dimming method in electronic ballasts for fluorescent lamps. The power factor, energy efficiency, electronic loss, efficacy (lumen/W), and crest factor of 2 × 36 W electronic ballasts based on these two dimming methods are recorded and compared over a wide dimming range. It is found that the voltage dimming control approach is much better than the frequency control method in most of the compared aspects as the lamp is dimmed. In particular, voltage dimming approach has much higher energy efficiency and lumen per watt than the frequency control one. Unlike the frequency dimming method, voltage dimming control has a distinctive feature in that its electronic loss decreases with decreasing lamp power. [ABSTRACT FROM AUTHOR]

The article focuses on the pseudocoevolutionary genetic algorithms (GA) for power electronic circuits optimization. Circuit parameters are optimized through two parallel coadapted GA-based optimization processes for the power conversion stage and feedback network, respectively. Each process has tunable and untunable parametric vectors. The best candidate of the tunable vector in one process is migrated into the other process as an untunable vector through a migration controller.

This paper presents a low-cost solution of converting the popularly adopted nondimmable electronic ballast circuit for fluorescent lamps with self-oscillating series resonant inverter into a dimmable one. The dimming function is achieved by increasing the switching frequency of the inverter from the natural frequency of the resonant tank, so that less energy is coupled to the lamp. Control of the switching frequency is based on deriving an adjustable dc current source from the resonant inductor in the resonant tank to control the operating point of the saturable transformers for driving the switches in the inverter. The overall implementation does not require any integrated circuit. A 17-W prototype has been built and studied. Theoretical predictions have been verified with experimental results. The lamp can be dimmed down to 10% of the full power. [ABSTRACT FROM AUTHOR]

Deals with a study which presented a generalized technique for computation of cycle state-variable sensitivity matrix of pulse-width-modulated direct current/direct current converters. Derivations of the sensitivity matrix; Comparisons with some available methods; Illustrative examples of the study; Conclusion.

A novel electrode power control scheme for dimmable ballasts is proposed. Dimming of the fluorescent lamp and control of electrode power are achieved by simultaneously adjusting the dc-link voltage and the switching frequency of the output inverter. The electrode power is derived by considering the near-orthogonal property of the lamp current and the resonant tank circuit current. [ABSTRACT FROM AUTHOR]

The realization of line and load regulation in switched-capacitor (SC)-based converters is discussed. A duty-cycle control is based on partial charging of the capacitors in the circuit. The influence on the efficiency is pointed out. The use of inductors in SC-based converters is discussed. [ABSTRACT FROM AUTHOR]

Coil-misalignment is one of the major hurdles for inductively coupled wireless power transfer in applications like retinal prosthesis. Weak magnetic flux linkage due to coil misalignments would significantly impair the power efficiency. A novel receiver configuration with high misalignment tolerance is presented in this paper. The proposed receiver is composed of two receiver coils placed orthogonally, so as to reduce the variation of mutual inductance between transmitting and receiving coils under misalignment conditions. Three different receiver coil structures are analyzed and compared using the same length of wire. Theoretical predictions have been confirmed with measurement results.