J. Marcos Alonso

Low cost electronic ballast for a 36-W fluorescent lamp based on a current-mode-controlled boost inverter for a 120-V DC bus power distribution

A non-resonant electronic ballast based on one power switch and on one reactive element-one inductance-is described in this paper. The special current mode control implementation provides an intrinsic short-circuit protection and a very simple control circuitry. Filament heating time, current during the heating period, and protection against broken tube can be easily implemented with the proposed circuitry. A greenhouse application with a 120-V dc bus power distribution is presented in this paper. The dc bus voltage is easily obtained (in this particular application) from a classical series-connected 12-pulse rectifier in combination with a transformer with two secondary windings (one in Wye connection and other one in Delta connection). An additional advantage of this configuration is the high power factor obtained at the input stage.

Solid-State Lighting: A System Review

T his article presents the background on the development of solid-state lighting technology, which is gaining popularity as a light source application. This review focuses on the main characteristics of solid-state lighting devices as well as their supply requirements and the effect of temperature on light-emitting diode (LED) performance. LED drivers are designed to achieve the best operation conditions without degrading the longer lifetime that this technology achieves in comparison to other popular light sources. Offline LED drivers include active power factor correction while current control with low ripple is required to supply the LED units or string arrangements. Methods to achieve balanced current sharing on paralleled LED strings and some of the latest contributions on LED drivers are also explained.

Capacitance Reduction With An Optimized Converter Connection Applied to LED Drivers

This paper presents a new control method and a detailed project methodology for the optimized connection method of two converters, aiming to reduce the redundant power processing, in order to supply high-power light-emitting diodes (LEDs) with reduced capacitance and high efficiency, directly from the ac line. This connection method allows dealing with two major issues related to the LED driver: capacitance reduction and efficiency increasing. The first converter provides power factor correction, whereas the second converter controls the current through the LED. The basic idea consists in making the second converter to process only the low-frequency ripple (LFR) of the first converter, thus smoothing the LED current. In this way, the LFR is managed by the second stage, so that the capacitance of the first stage can be significantly reduced. The proposed control method can achieve better results for the low-frequency compensation. In addition to that, a high power factor and a low harmonic content are obtained, fulfilling the IEC 61000-3-2 Class C requirements. A laboratory prototype with a rated power of 75 W and an input voltage of 220 Vrms/60 Hz was built in order to show the feasibility of the idea. The measured overall efficiency of the converter was 91%, and electrolytic capacitors were avoided.

Matching LED and Driver Life Spans: A Review of Different Techniques

A review of various proposed schemes to increase the reliability and life span of solid-state lighting (SSL) systems is presented in this article. Since the mainstream devices employed for such lighting systems are inorganic, high-power light-emitting diodes (LEDs), which are devices characterized by their very long life, most of the questions in reliability and endurability arise from the electronic offline circuit driving the LEDs. Issues regarding the limited reliability of specific components, such as electrolytic capacitors, are introduced. Several power-?conversion configurations aimed to capacitance reduction and capacitor technology exchange are put forward as alternative solutions for implementing long-life drivers, with remarks on both their benefits and drawbacks. An extensive literature review on the topic is carried out, and some practical outcomes from recent research on offline LED driving are highlighted.

Offline Soft-Switched LED Driver Based on an Integrated Bridgeless Boost–Asymmetrical Half-Bridge Converter

This paper proposes an offline single-stage light-emitting diode (LED) driver based on a novel approach to reduce low-frequency ripple in LED arrays supplied from mains, while assuring high input power factor (PF). The proposal employs a series resonant dc-dc converter integrated into a bridgeless boost power factor correction (PFC) stage. The resonant stage works to reduce the low-frequency ripple transmitted from the output of the PFC stage to the LEDs with only small power losses. This solution achieves three main goals: 1) reduction of the bulk capacitance used at the dc bus, allowing for the use of long-life film capacitors; 2) increase in the overall efficiency of the LED driver owing to the low switching and conduction losses in the shared switching network; and 3) assuring high input PF. Experimental results of a driver without electrolytic capacitors for a 100-W street lighting LED luminaire are presented, showing overall efficiency in excess of 92%, input PF greater than 0.97, and line current harmonic content in compliance with the IEC 61000-3-2 standard.

A long-life high-power-factor HPS-lamp LED retrofit converter based on the integrated buck-boost buck topology

In this paper a long-life high-power-factor integrated converter able to supply LED lamps in high-pressure-sodium (HPS) lamp retrofit applications is presented. The converter is made up by the integration of a buck-boost converter with a buck converter, which provides the necessary high input power factor and low voltage transformation ratio to supply the low-voltage LED array from the mains. The analysis of the converter is carried out and a design procedure is proposed. Also, the design is performed so that low capacitances are needed at the output of each semistage. This allows for the use of long-life film capacitors, thus matching the converter lifetime to that of the LED lamp. A laboratory prototype supplied from 230V/50Hz mains used to drive two LED arrays in series with a total output power of 100W is presented.

Static and Dynamic Photoelectrothermal Modeling of LED Lamps Including Low-Frequency Current Ripple Effects

In this paper, a static and dynamic photoelectrothermal model including the impact of low-frequency current ripple on light-emitting diodes (LEDs) performance is proposed. The objective of this study is to evaluate the dynamical interaction among thermal, photometrical, and electrical properties of the LEDs when they are supplied by a dc constant current with a superposed low frequency sinusoidal ripple, which is the common case in offline LED drivers. Therefore, this paper presents both a model and experimental data for analyzing the LED photometrical behavior in terms of luminous flux, efficacy, flicker, and chromaticity. Three laboratory prototypes with different heat sinks and LED models have been tested. Experimental results are presented to evaluate the LED photometrical behavior under the aforementioned operating conditions and to validate the proposed modeling methodology.

Solid-State Lighting: A Concise Review of the State of the Art on LED and OLED Modeling

This article presents an overview of technologies for solid-state lighting (SSL). In recent years, light-emitting diodes (LEDs) have developed characteristics desirable for lighting applications. The success of these light sources for general lighting depends on the system design, which comprises an understanding of electrical and photometrical characteristics under the temperature effect on device performance. This review focuses on the main theoretical models for the characterization of SSL devices, regarding the electrical and thermal aspects to reach the desired photometrical characteristic for a lighting system. An approach about inorganic LEDs and organic LEDs (OLEDs) will be presented along with the application of these devices in SSL systems.

Analysis and design of the quadratic buck-boost converter as a high-power-factor driver for power-LED lamps

In this paper the quadratic buck-boost (QBB) converter is proposed as a high-power-factor off-line power supply for power-LED lamps. The QBB converter features just one controlled switch and two inductors and is able to supply a solid-state lamp from the mains providing high power factor and good efficiency. In the paper, the QBB converter is analyzed and a design methodology is proposed. It is demonstrated that with a careful design of the converter, the filter capacitances can be made small enough so that film capacitors may be used. In this way, the converter mean time between failures (MTBF) can be made as high as that of the solid-state lamp. A design example for a 70W converter supplied from a 230V/50Hz mains for street lighting applications is shown. Finally, experimental results from a laboratory prototype are also presented.

Two Flyback-Based Integrated Converters for the Implementation of LFSW Electronic Ballasts

In this paper a new configuration of the two-flyback-based high-power-factor electronic ballast is proposed. The ballast is aimed to supply high intensity discharge (HID) lamps with a low frequency square waveform (LFSW), so that acoustic resonance (AR) phenomenon can be avoided. The proposed topology is compared to a previously presented one, which integrated the two flyback converters in a different manner. Therefore, this paper is focused on the comparison of both configurations by analyzing voltage and current waveforms and components stress. The proposed electronic ballast presents a high efficiency with a reduced number of components and no over current stress in the shared switch, which improves its efficiency. Experimental results validate both integrated configurations, but demonstrate a higher efficiency for the new arrangement proposed in this paper.