Showing papers by "J.M. Alonso published in 2010"

High frequency PWM dimming technique for high power factor converters in LED lighting

Abstract: This paper deals with the capability of dimming operation added to the Integrated Buck-Flyback Converter (IBFC) topology developed in previous works. Firstly, the three main dimming methods that have been identified by the authors such as enable dimming, shunt dimming and series dimming will be briefly commented. Afterwards, the IBFC topology will be tested performing enable dimming at 100 Hz and 200 Hz. Secondly, besides the main dimming methods, a new proposal is introduced: high frequency series PWM dimming, which overcomes the main issues faced when developing series PWM dimming in constant-current fixed-frequency controlled converters. The dimming control loop of this technique will be presented, as well as the laboratory tests performed, obtaining good results in terms of dimming ratio, harmonic content of the input current and power factor.

Magnetic control of DC-DC resonant converters provides constant frequency operation

Abstract: A solution to operate DC-DC resonant converters at constant frequency is proposed. A variable inductor is used to achieve output voltage control and regulation without changing the switching frequency of the converter. The output voltage characteristic of the parallel resonant converter operating under this so-called magnetic control is briefly analysed. A 48 V input, 5 V output, 500 kHz, 25 W prototype is presented to prove the feasibility of the proposed control method.

HID Lamps Fed With Square Waveforms: Dimming and Frequency Effects on Stability, Current Crest Factor, and Power Factor

Abstract: In this paper, the dimming and frequency effects on stability, current crest factor (CCF), and power factor (PF) of high-intensity discharge lamps fed with square waveforms are experimentally evaluated. For this evaluation, the lamp was stabilized using resistances. The resistances were varied in function of the impedance of the lamp. The effects of dimming and frequency variation were observed for two types of lamps of different nominal powers. The results indicate the ranges in which the lamp is stable and the frontier values in which the lamp becomes unstable. The CCF and PF remain close to unity, and no acoustic resonances were observed during the applied tests.

Magnetic regulator topologies for dimmable electronic ballasts

Abstract: The T5 fluorescent lamp is the first linear lamp type to be controlled only by electronic ballasts, due to its high lamp voltage and the requirement of an end-of-life detection circuit. Its efficient behavior and compactness has pushed it into the leading edge of new fluorescent lighting projects. This paper investigates the response of the T5 lamps to magnetically-controlled electronic ballasts, also exploring new magnetic regulator topologies. Experimental results for the Master TL5 HE 14W and 21W from Philips are reported.

On the use of magnetic regulators in electronic ballasts

Abstract: This work proposes an analysis on a specific topic regarding ballast design and lamp operation in dimming conditions, in compliance with current regulations Particular issues regarding electrode operating conditions are referred The SoS definition, currently adopted in IEC standards, is analysed and applied to T5 commercial ballasts, in order to verify reference results Similar SoS lines are then obtained for two different TL5 fluorescent lamps (HE 21W and HO 39W), using a developed dimmable electronic ballast, based on a magnetic control technique The analysis and discussion of these results represents a necessary step for the optimization of magnetically-controlled electronic ballasts