Analysis and design for self-oscillating LED driver with high frequency pulsating output current

Vázquez

Arias

et al. 2019

Light-Emitting Diodes (LEDs) are coming strongly into the lighting market due to their advantages over conventional lighting solutions: energy efficient, controllable in both light and color, long lifetime, lack of a warm-up period and high power density. Some of these advantages will make LED light sources to be more than just a lightbulb, being able to transmit data, control light color, hue and intensity or even detect people in indoor environments. Nevertheless, these advantages attributed to LED capabilities are, in reality, achieved thanks to the LED driver. The present work reviews the current stateof-the-art strategies to drive LEDs from ac power grids with special emphasis into removing the most limiting component from the point of view of the lifetime, which is the electrolytic capacitor, while achieving a flicker-free performance of the light output of the LED driver. Moreover, it focuses on analyzing the required regulations, challenges and applicability of LED drivers in both single-phase and three-phase ac power grids.Note: This only applies for certified dimmable luminaires. Audible noiseLuminaire shall not emit noise above 24 dBA at 1 meter or less at the minimum output.0885-8993 (c)

Section: ) Multi-stage Solutionsmentioning

confidence: 99%

“…Active: single-stage -> 25 W [47]- [50], [53], [60], [73]- [75], [77], [108], [110]- [114], [136], [138], [196]…”

Section: Three-phase Ac-dc Led Driversmentioning

confidence: 99%

A Review on Flicker-Free AC–DC LED Drivers for Single-Phase and Three-Phase AC Power Grids

Vázquez

Arias

et al. 2019

“…considering that � ( 1 ) − � is negligible when compared to the other terms in (15) and where α can be defined as, …”

Section: Resonant Stage [T1 T2] Fig 2 (B)mentioning

confidence: 99%

“…The operation of HB-LEDs at high frequencies (i.e. > 100 kHz) acting as the regular diodes of a power converter, also referred in literature as high-frequency AC-LED driving, has been studied by means of resonant dual half bridges applying a sinusoidal high frequency current waveform to the HB-LEDs [11]- [13], a flyback converter working in Discontinuous Conduction Mode (DCM) [14] and self-oscillating topologies [15]. However, there is no factual evidence on how will the HBLEDs perform under a high frequency sinusoid or triangular current waveform in terms of light quality, reliability or Correlated Color Temperature (CCT).…”

Section: Introductionmentioning

confidence: 99%

A Family of High Frequency AC-LED Drivers Based on ZCS-QRCs

Lamar

López

et al. 2018

Abstract-A family of dimmable AC-LED drivers fed from dc voltages, is presented in this paper based on Zero Current S witching Quasi-Resonant Converters (ZCS -QRCs). The proposed family of drivers is based on replacing the diode in conventional converter topologies (i.e. buck, boost or buck-boost) by a string of High-Brightness Light-Emitting Diodes (HB-LED). Hence, the HB-LED string will be working as the rectifier diode and the load, switching at the same frequency of the main switch. In this case, the output current, which is experimentally validated, shows a negative current peak due to the reverse-recovery effect of the HB-LEDs. In order to reduce the reverse-recovery effect on the HB-LEDs, the main switch of the proposed topologies is replaced with a full-wave resonant switch, which makes possible to reduce the di/dt during the turn-off of the HB-LED string, therefore the reverse recovery effect is eliminated. Moreover, the dimming of the HB-LEDs is done by means of changing the switching frequency of the converter, by varying the turn-off while keeping a constant turn-on time. The proposed converters are suggested to be used in a post-regulator stage of an ac-dc converter or as the interface between the low voltage bus and the HB-LED string in a dc nanogrid. In order to validate the analysis, the proposed topologies have been experimentally tested on a constructed prototype with an output power of 7.5 W, that is able to achieve an electrical efficiency of 94.5% and a luminous efficacy of 110 lm/W at full load. Moreover, the analysis has been extended to a comparison in terms of reliability with the conventional topologies on a 700 h test.

“…It should be noted, that while in conventional dc-dc converters the LEDs are supplied with a constant current, in the DL//S and DL//L AC-LED drivers, the LED is supplied with a pulsed current, pulsing at the same frequency at which the main switch (i.e., S) is operating. The operation of the LED at high frequencies (i.e., > 100 kHz) acting as the regular diode of a power converter, also referred in literature as high-frequency AC-LED driving, has been studied by means of resonant dual half bridges [6]- [8], a flyback converter working in Discontinuous Conduction Mode (DCM) [9], self-oscillating topologies [10] or quasi-resonant converters [11], [12]. All these works conclude that LEDs are able to switch at high frequencies under different current waveforms.…”

Section: Introductionmentioning

confidence: 99%

On Supplying LEDs From Very Low DC Voltages With High-Frequency AC-LED Drivers

Vázquez

Aller

et al. 2019

Abstract-This work studies the driving of white Light Emitting Diodes (LEDs) from very low voltages in the range of 1.2 to 2 V. The proposed idea is based on replacing the standard Schottky diode used in conventional converter topologies (i.e., buck, buck-boost and boost) with an LED, while shortcutting the output of the converter. In this configuration, the LED works both as the load and as the rectifier diode of the converter, hence, switching the LED at high frequencies (i.e. > 100 kHz). Moreover, a thorough analytical study is carried out for the two topologies rendered in this work. Particularly emphasizing their static analysis and the obtaining of the boundaries between the different conduction modes. Finally, the idea is validated experimentally by means of the boost converter variation (i.e., DL//S AC-LED driver). The DL//S AC-LED driver has also been compared with a dc-dc boost converter showing a better luminous efficacy while disposing of the Schottky diode and the output capacitor. This analysis is carried out when connected to a Li-Ion battery using a simple control and integrated circuit for its development.