M. F. Menke

A Review on Variable Inductors and Variable Transformers: Applications to Lighting Drivers

This paper presents a literature review on magnetically-controlled devices, variable inductors and variable transformers, and their applications in lighting gear. It describes the fundamentals and basic operating principle of such devices. Then, it focus on the review of specific techniques and circuits taking advantage of the presence of a controlled inductance value, by covering recent applications regarding discharge and solidstate lamp drivers.

Comparison of self-oscillating electronic ballasts dimming methods with power factor correction for fluorescent lamps

This paper presents a comparative analysis of dimmable self-oscillating electronic ballast for fluorescent lamps. A review of general dimming methods presented in the literature is performed. A general analysis of each dimming method is made, and the operation with power factor correction was considered in order to evaluate the characteristic of each topology and to define other circuits more adequate for this purpose. A comparison based on literature review and experimental results of the implemented prototypes is carried out in order to establish the main conclusion from this analysis.

High power factor dimmable self-oscillating electronic ballast with variable inductor control

This paper presents a new high power factor dimmable self-oscillating electronic ballast (DSOEB), in which a variable inductor (VI) is used to control the fluorescent lamp (FL) power. Two different approaches are proposed to provide a wide dimming range using a self-oscillating electronic ballast, and a power factor correction (PFC) stage. In the first one, the VI is placed in the series resonant parallel-loaded filter (SRPLI), controlling the rms value of the lamp current with the dc bus voltage supplied by the PFC stage in a closed loop, and in the second one, the VI is placed in the PFC stage, controlling directly the power feeding the inverter. Experimental results for both topologies are presented to evaluate the preliminary performance of the circuit for a 32 W FL.

A review on variable inductors and variable transformers: Applications to lighting drivers

This paper presents a literature review on magnetically-controlled devices, variable inductors (VI), and variable transformers (VT), and their applications to lighting gears for discharge lamps and/or LED lamps. These current-controlled devices are mainly characterized by nonlinear and non-uniform saturation of the magnetic core. The paper describes the fundamentals and basic operating principle of such devices and provides an overview of existing patents. These patents refer the devices, VIs or VTs, as useful or industrially applicable. Some present one or more claims regarding the construction of the device and behavioral characteristic; others refer to specific applications, such as voltage regulation or universal ballast operation. Afterwards, the paper focuses on the review of specific techniques and circuits taking advantage of the presence of a controlled inductance value, by covering recent applications regarding discharge and solid-state lamp drivers. These applications will show how these multi-winding devices, typically not considered due to their low efficiency, may fulfill an important role and add features to state-of-the-art lamp drivers.

Automatic lamp detection technique for self-oscillating fluorescent lamp electronic ballasts

This paper presents a self-oscillating electronic ballast to operate T5 HO fluorescent lamps with power ratings of 24 W, 39 W and 49 W. The proposed circuit detects the lamp type by measuring the lamp voltage through a control circuit which changes the power factor correction circuit duty cycle to adequate the output power. Experimental results are shown to demonstrate the feasibility of the proposed solution.

Comparative Analysis of Self-Oscillating Electronic Ballast Dimming Methods With Power Factor Correction for Fluorescent Lamps

This paper presents a comparative analysis of the performance characteristics among different dimming methods for electronic ballasts using the self-oscillating half-bridge (HB) inverter with a power factor correction (PFC) stage. Initially, a review of common dimming methods presented in the literature is presented, and a general analysis of each dimming method is carried out. Furthermore, the operation of the dimmable self-oscillating electronic ballast with a PFC stage is analyzed in order to evaluate the performance of each different dimming methods used. Finally, a comparison among the different dimming methods implemented with the self-oscillating HB inverter and PFC stage is carried out.

Fluorescent lamp characterization automated data acquisition system

The data acquisition process is an important step in the development of device models, and usually requires large amounts of time. Besides, since it is a process controlled by a scientist, it is subject to human errors. The automation of this process by a configurable system removes the human error factor and does not require full time attention from the scientist. These drawbacks are more evident when a device has to be modeled under various conditions, has a slow thermal response or a large database of various models has to be built. In this scope, the objective of this paper is to present the structure and results of an automated data acquisition system for fluorescent lamps. The aim of this system is to generate a database, which will be used in further studies of universal electronic ballasts.

Iterative method for analysis of dimmable self-oscillating electronic ballast under bus voltage control

This paper presents a predictive method of the self-oscillating electronic ballast (SOEB) behavior under dimming conditions. This work is focused on the bus voltage variation dimming method, where a closed analysis is not possible to carry out without considering the interaction among inverter bus voltage, FL power/resistance nonlinear behavior, and frequency operation of the SOEB. Thus, an iterative method is proposed in order to predict the oscillating frequency related with the fluorescent lamp power under bus voltage variation. Experimental results for a T8 32 W fluorescent lamp are obtained in order to compare simulation results, and verify the feasibility of the proposed method.

Self-Oscillating electronic ballast with lighting intensity regulation

This paper presents electronic ballast with dimming capability supplying a 32 W fluorescent lamp. The electronic ballast is a self-oscillating driving circuit and an additional circuit responsible to dimming the fluorescent lamp using a lighting dependent resistor. This luminous sensor measures the luminous flux level and set the lamp power through the voltage gain variation of the resonant filter based on a feedforward control. Simulation and experimental results of the proposed electronic ballast are presented to demonstrate the feasibility of the system.

Two-stage digitally controlled led driver based on buck-boost and DC/DC LLC resonant converter

In this study a digitally controlled Light Emitting Diode (LED) driver operating with high power factor, dimming capability and reduced DC-link capacitance is proposed. The proposed LED driver circuit topology, designed to supply a 100 W LED module, is composed by two independent stages. The Power Factor Correction stage is implemented with the buck-boost DC/DC converter, operating in Discontinuous Conduction Mode. This stage provide a high power factor and maintain the average bus voltage controlled in 400 V. Besides, a reduce DC-link capacitance with 25 μF is used, thus allowing the use of log lifetime film capacitors. The second stage comprises the DC/DC Half-Bridge LLC resonant converter, which is in charge to keep controlled the averaged LED current as function of the required dimming level. To avoid output luminous intensity modulation, the control loop of the second stage is designed in order to reduce the LED current ripple, arising from the low frequency bus voltage ripple. Experimental results are presented with the topology operating under output dimming and reduced DC-link capacitance.