David Gacio

Normagrup Technology SA · R&D

This paper presents a light-emitting-diode (LED) model based on the four-parameter Taylor series to describe the – characteristic of the LED at different junction temperatures. Therefore, in order to precisely model the LED nonlinear characteristics at different junction temperatures, an improved Taylor series-based LED model is proposed according...

There is currently a trend in power electronics to avoiding the use of electrolytic capacitors in LED drivers, provided that their expected life span is much lower than that of the LEDs, thus reducing the reliability of the entire LED fixture. This paper presents an optimization study about the determination of the minimal bus capacitance needed fo...

In this paper the integrated double buck-boost converter (IDBBC) operating with both stages in discontinuous conduction mode (DCM) is analyzed. The converter is intended to supply high-voltage LED lamps from the mains, typically in street lighting applications. A high input power factor is assured by operating the first stage in DCM, thus complying...

Parallel connection of several LED strings is a practical way to reduce the overall lamp voltage when a large number of emitters is needed. However, this connection might lead to high current mismatches between strings due to the dispersion of characteristics that even binned devices feature. Several techniques have been proposed in order to elimin...

A low-cost 18W intelligent LED driver for energy savings is presented. The intelligent LED driver has a DALI interface that allows it to be included in an upper lighting smart grid. So, it must provide galvanic isolation. The proposed LED driver is based on a two stage scheme with 24V safety voltage. The first stage is based on a PFC Flyback conver...

In this paper, a straightforward methodology to modeling high power factor (HPF) ac-dc converters is presented. The proposed methodology is based on the averaging technique directly applied to the converter under modeling. An averaged large-signal equivalent circuit is thus generated, which is useful to perform extremely fast simulations. From the...

In this paper a methodology to modeling high-power-factor (HPF) ac-dc converters in LED driving applications is presented. The proposed methodology is based on the averaging methodology applied to the converter under modeling. An averaged large-signal equivalent circuit is generated in this manner, which will be useful to perform extremely fast com...

A long-life high-power-factor integrated converter able to supply light-emitting diode (LED) lamps in high-pressure-sodium lamp retrofitting applications is presented. The proposed converter is the integration of a buck-boost converter with a buck converter, thus providing the necessary high input power factor and voltage transformation ratio to su...

This paper proposes an electronic driver for public lighting systems. The input stage is based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage. The output stage is a boost converter with an output current control. The proposed circuit is introduced and anal...

In the prior literature, the small-signal incremental impedance of fluorescent lamps has been characterized using a single-pole single-zero transfer function. This transfer function provides a good estimation of the lamp dynamics at rated power. However, when this model is used at low power levels, the accuracy is severely reduced, particularly at...

In this paper a new technique to reduce the LED current ripple and storage capacitance in high power factor (PF) off-line LED power supplies is investigated. The proposed methodology is based on the use of integrated power converters (IPC) to implement the power supply. Thus, the first stage operates in discontinuous conduction mode (DCM) to provid...

This paper deals with a topology for an off-line LED electronic driver. The use of electrolytic capacitors in the DC link is avoided, therefore extending lifespan and reliability. Given that the resulting output capacitance of the PFC stage is relatively small, a high LF ripple appears at the DC-link. This work proposes the use of a current-fed bid...

In this paper, a study on LED retrofit solutions for low-voltage halogen cycle lamps is conducted. In the first part of this paper, a lamp based on a LED array is designed to operate in substitution of a 12-V/50-W halogen lamp, for lighting fixtures in which these lamps are supplied using a line transformer. The design includes the selection of an...

Nowadays, different power generation strategies for grid-connected systems can be found, ranging from single high power plants (tens and hundreds of MW), to thousands of small wattage (below 1 kW) micro-generators. This paper studies a new power topology for the latter, based on a bidirectional Flyback converter. The comparison with the standard to...

In this paper, an integrated double buck-boost (IDBB) converter is proposed as a high-power-factor offline power supply for power-LED lamps. The IDBB 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 this paper, the IDBB conver...

The analysis, design, and implementation of a microcontroller-based electronic ballast to supply metal halide (MH) lamps are presented. The proposed topology is based on the integration of the buck and flyback converters, the former providing power factor correction and the latter controlling lamp power. The lamp is supplied by a low-frequency squa...

This paper deals with the capability of pulse width modulation (PWM) dimming operation added to the high-power factor-integrated buck-flyback converter (IBFC), which was developed in previous works for LED lighting applications. First, the two main dimming techniques will be introduced, namely, analog dimming and PWM dimming. Then, the three main P...

In this paper, a new technique for controlling dc-dc resonant converters is investigated. A variable inductance is used to control and regulate the dc output voltage maintaining constant switching frequency for the half-bridge transistors. The output voltage characteristics of the series resonant and parallel resonant converters under the proposed...

This paper deals with the thermal characteristics of the I-V curve of GaN-based white LEDs, focused on the variations of the dynamic resistance. The final goal of this study is to improve the static and dynamic operation of the LED driver within a wide range of temperature. Four LEDs from different manufacturers were chosen for this study. The firs...

This paper presents the analysis, design, and experimentation of a closed-loop metal halide (MH) lamp ballast, which supplies the lamp with a low-frequency square waveform. First, a discussion related to the lamp parameter that should be regulated (power or current) is presented, since this issue has not been well addressed in the previous literatu...

In this paper the integrated double buck-boost (IDBB) converter operating with both stages in discontinuous conduction mode (DCM) is analyzed. The converter is intended to supply high voltage LED lamps from the mains, typically in street lighting applications. A high input power factor is assured by operating the first stage in DCM, thus verifying...

One important aspect for the design of dimming ballasts for fluorescent lamps is the output power range that can be obtained. Some applications require that the output power can be reduced below 10%. However, in some ballast designs, there is no easy way to reduce the output power to the required minimum level without finding instabilities that cou...

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 sup...

In this paper, the variable transformer solution is presented as a step forward in magnetically controlled electronic ballasts. The proposed technique takes advantage of the device's equivalent series inductance to provide a new flexible way for lamp's luminous flux regulation. Output electrical isolation and constant frequency operation are also g...

The goal of this paper is the evaluation of the interleaved buck converter as a high-brightness (HB) LEDs electronic driver, comparing its performance with the standard buck converter. The main drawbacks of the standard converter come from the high inductor value necessary to guarantee low output current ripple, which result in high inductor losses...

In this paper, a digitally controlled electronic ballast is presented. The ballast corresponds to the so-called universal or multiwatt ballasts, which are intended to operate different lamps with different power ratings without performing any change in the hardware. Thus, the ballast must incorporate some kind of circuitry so that the rated power o...

Due to the high rise in luminous efficiency that high-brightness light-emitting diodes (HB-LEDs) have experienced in recent years, many new applications have been researched. This paper covers a streetlight LED application using the offline integrated buck-flyback converter (IBFC) developed in previous works. In this application, the converter is u...

This paper presents an off-line integrated full ballast to supply a 35 W assembly of Power LEDs. The proposed solution integrates an input PFC stage (a flyback converter operating in DCM) and a DC-DC output converter (a buck converter) into a single switch power stage, operating with peak current control. As it will be shown, this control scheme ma...

This paper proposes a novel complete electronic ballast for low-wattage metal halide (LWMH) lamps. The lamp driver is based on the integration of a flyback power factor correction (PFC) input stage and a buck-boost inverter stage. The resulting circuit supplies the lamps with a high-frequency (HF) square current waveform, operating from the mains f...

In this work, an interleaved inverter with peak current control is investigated to supply low wattage metal halide lamps. The proposed topology provides a low frequency square current waveform that theoretically has no high frequency ripple, thus allowing acoustic resonances free operation of these lamps. The series igniter stage equivalent is chos...

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 analy...

This paper presents an off-line integrated full ballast to supply a 35W assembly of Power LEDs. The proposed solution is based in an input PFC stage and a DC to DC converter which provides a constant current through the assembly independently from the DC link voltage. The full ballast has full dimming capability, and all the analysis and design ste...

In this paper a new solution to operate dc-dc resonant converters at constant frequency is investigated. The proposed converter is based on the use of a variable inductor to achieve output voltage control and regulation at constant switching frequency. The output voltage characteristics for two typical dc-dc resonant converters operating under this...

This work proposes a new interleaved converter to supply Power LEDs. As an interleaved scheme, the converter provides a very low output current ripple, which makes it suitable for this application. The low inductor values used in the device allow the ability of attaining PWM dimming of the Power LEDs at high frequencies (20 kHz and higher). The mai...

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 ana...

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...

This paper presents a full ballast for driving an assembly of high brightness LEDs, based on a new dc to dc converter. The converter provides a constant current waveform to the load parting from a DC bus voltage. The converter, operating with a peak current control, keeps the current through the LEDs constant independently of the bus voltage. This...

In pattern recognition systems the lighting method is critical to determine the success or failure of an algorithm. The goal of this work is to design a lighting workbench able to control the color and luminous flux allowing the vision systems programmers to verify the robustness of their algorithms. This paper describes the methodology to control...

In this paper the design, implementation and experimental results of a high-voltage power supply for ozone generation are presented. The power stage is formed by a buck converter plus a current-fed parallel-resonant push-pull inverter. The buck converter is used to both regulate the output power against the line voltage variation, and to control th...

This paper proposes a novel complete electronic ballast for Low Wattage Metal Halide lamps. The lamp driver is based on the integration of a flyback PFC input stage and a buck-boost inverter stage. The resulting circuit supplies the lamps properly, operating from the mains facility. The main feature of the proposed ballast is that through an adequa...

One of the most important advantages in using piezoelectric transformers (PT) is that they operate at high frequencies with a very good efficiency [1], tipically higher than 95%. This paper presents a DC/DC converter based on two piezoelectric transformers which duplicates the output voltage frequency ripple, maintaining the switching frequency. Al...

New advances on magnetically-controlled electronic ballasts can grant the ability to dim the lamp and simultaneously guarantee output electrical isolation. By means of a variable transformer, whose model is presented, this new technique is developed and experimentally verified. In addition, a simple method for the large signal characterization of t...

In this paper a digitally controlled electronic ballast is presented. The ballast corresponds to the so-called universal ballasts, which are intended to operate different lamps with different power ratings without performing any change in the hardware. Thus, the ballast must incorporate some kind of circuitry so that the rated power of the connecte...

Due to the high rise in luminous efficiency that HB-LEDs have experienced in the last recent years, many new applications have been researched. In this paper, a streetlight LED application will be covered, using the integrated buck-flyback converter developed in previous works, which performs power factor correction (PFC) from a universal AC source...

One of the most important advantages in using piezoelectric transformers (PT) is that they operate at high frequencies with a very good efficiency, tipically higher than 95%. This paper presents a DC/DC converter based on two piezoelectric transformers which duplicates the output voltage frequency ripple, maintaining the switching frequency. Also,...

Since the high rise in luminous flux power LEDs have experienced in the last years, they have become an overcoming alternative to incandescent bulbs for automotive signal lamps, and even an interesting choice for automotive headlamps, as most recent prototypes has shown, since the performance is near to that of HID lamps. This rise in luminous flux...

The first LED diode was created in 1969. Since then, they have been experiencing a continuous improvement in luminous efficiency and power dissipation, achieving current AIInGaP and InGaN devices for yellow to red, and blue to green, including white, colours respectively. The improvement experienced in both luminous efficiency and power dissipation...