Dimming DC–DC LED Drivers: Luminous Efficiency, Power Losses, & Best-in-Class

AbstractFor the modern smart lighting systems one of the most attractive LED advantages is the dimming possibility. Many researchers and engineers from the field of lighting engineering are trying to find compromise between the efficiency of LED dimming process and the ease of its implementation. This paper also presents an attempt to improve LED dimmer parameters. Comparative investigation of the operation of buck LED drivers in continuous conduction mode and discontinuous conduction mode are discussed here. The first section of paper briefly describes the controllability parameters of the converter in both of these modes. The positive impact of discontinuous conduction mode on the controllability parameters as well as the results of the analytical estimation and the results of associated experiments are summarized at the end of the first section. The second section describes the impact of discontinuous conduction mode on the losses of LED dimmer. The analytical estimation of power losses in the main converter components for both operation modes as well as the summary of the experiments to identify distribution of power losses between these components are presented in this section. Finally, the conclusions about using discontinuous conduction mode for dimmable LED lamps as well as guidelines for the choosing of the components with the most appropriate parameters are drawn

Download Full-text

Spectroscopic Diagnostics of Tokamaks

International Astronomical Union Colloquium ◽

10.1017/s0252921100107638 ◽

1988 ◽

Vol 102 ◽

pp. 165-174

Author(s):

C. de Michelis

Keyword(s):

Transport Properties ◽

Power Losses ◽

Spectroscopic Diagnostics ◽

Important Concern

AbstractImpurities being an important concern in tokamaks, spectroscopy plays a key role in their understanding. Techniques for the evaluation of concentrations, power losses and transport properties are surveyed, and a few developments are outlined.

Download Full-text

Flaring of the Vessels at the Total Cavopulmonary Connection (TCPC) Site Further Reduces Power Losses

Journal of the American College of Cardiology ◽

10.1016/s0735-1097(97)84196-4 ◽

1998 ◽

Vol 31 (2) ◽

pp. 113A

Author(s):

A Ensley

Keyword(s):

Total Cavopulmonary Connection ◽

Power Losses ◽

Cavopulmonary Connection

Download Full-text

Power Losses in RF Inductor of Ferrite-Free Closed-Loop Inductively-Coupled Low Pressure Mercury Lamps

Light & Engineering ◽

10.33383/2019-040 ◽

2020 ◽

pp. 89-94 ◽

Cited By ~ 1

Author(s):

Ekaterina V. Lovlya ◽

Oleg A. Popov

Keyword(s):

Closed Loop ◽

Low Pressure ◽

Mercury Vapour ◽

Plasma Power ◽

Power Losses ◽

Inductive Discharge ◽

Inductively Coupled ◽

Radial Inhomogeneity ◽

Transformer Model ◽

Rf Inductor

RF inductor power losses of ferrite-free electrode-less low pressure mercury inductively-coupled discharges excited in closed-loop dielectric tube were studied. The modelling was made within the framework of low pressure inductive discharge transformer model for discharge lamps with tubes of 16, 25 and 38 mm inner diam. filled with the mixture of mercury vapour (7.5×10–3 mm Hg) and argon (0.1, 0.3 and 1.0 mm Hg) at RF frequencies of 1, 7; 3.4 and 5.1 MHz and plasma power of (25–500) W. Discharges were excited with the help of the induction coil of 3, 4 and 6 turns placed along the inner perimeter of the closed-loop tube. It was found that the dependence of coil power losses, Pcoil, on the discharge plasma power, Ppl, had the minimum while Pcoil decreased with RF frequency, tube diameter and coil number of turns. The modelling results were found in good qualitative agreement with the experimental data; quantitative discrepancies are believed to be due skin-effect and RF electric field radial inhomogeneity that were not included in discharge modelling.

Download Full-text

Dependence of Current Harmonics of Greenhouse Irradiators on Supply Voltage

Light & Engineering ◽

10.33383/2019-024 ◽

2020 ◽

pp. 85-88 ◽

Cited By ~ 1

Author(s):

Nadezhda P. Kondratieva

Keyword(s):

Mathematical Models ◽

Supply Voltage ◽

Harmonic Distortion ◽

Feasibility Studies ◽

Power Losses ◽

Voltage Level ◽

Supply Networks ◽

Current Harmonics ◽

Cable Lines ◽

Harmonic Composition

The article describes the results of the study concerning the effect of the voltage level on current harmonic composition in greenhouses irradiators. It is found that its change affects the level of current harmonics of all types of the studied greenhouse irradiators. With decrease of nominal supply voltage by 10 %, the total harmonic distortion THDi decreases by 9 % for emitters equipped with high pressure sodium lamps (HPSL), by 10 % for emitters with electrode-less lamps and by 3 % for LED based emitters. With increase of nominal supply voltage by 10 %, THDi increases by 23 % for lighting devices equipped with HPSL, by 10 % for irradiators with electrode-less lamps and by 3 % for LED based emitters. Therefore, changes of supply voltage cause the least effect on the level of current harmonics of LED based emitters and then the emitters with electrode-less lamps. Change of the level of supply voltage causes the greatest effect on the level of current harmonics of HPSL based irradiators. Mathematical models of dependence of THDi on the level of supply voltage for greenhouse emitters equipped with LED, electrode-less lamps and HPSL lamps were formulated. These mathematical models may be used for calculations of total current when selecting transformers and supply cable lines for greenhouse lighting devices, for design of new or reconstruction of existing irradiation systems of greenhouse facilities, and for calculation of power losses in power supply networks of greenhouse facilities during feasibility studies for energy saving and energy efficiency increasing projects.

Download Full-text

Comparison of Dc-Dc SEPIC, CUK and Flyback Converters Based LED Drivers

Light & Engineering ◽

10.33383/2018-70 ◽

2020 ◽

pp. 99-107

Author(s):

Erdal Sehirli

Keyword(s):

Integrated Circuit ◽

Closed Loop ◽

Input Voltage ◽

Open Loop ◽

Current Sensor ◽

Switching Frequency ◽

Led Driver ◽

Advantages And Disadvantages ◽

Led Drivers ◽

Conduction Mode

This paper presents the comparison of LED driver topologies that include SEPIC, CUK and FLYBACK DC-DC converters. Both topologies are designed for 8W power and operated in discontinuous conduction mode (DCM) with 88 kHz switching frequency. Furthermore, inductors of SEPIC and CUK converters are wounded as coupled. Applications are realized by using SG3524 integrated circuit for open loop and PIC16F877 microcontroller for closed loop. Besides, ACS712 current sensor used to limit maximum LED current for closed loop applications. Finally, SEPIC, CUK and FLYBACK DC-DC LED drivers are compared with respect to LED current, LED voltage, input voltage and current. Also, advantages and disadvantages of all topologies are concluded.

Download Full-text