Multi-string AC-powered LED driver with current regulation reduction based on simple circuitry

Abstract

In this letter, a new simple circuitry LED driver with current reduction is proposed, realized and experimentally validated. The proposed circuit comprises with very few components intended for making a costeffective and compact design while still shows a high performance. The circuit reduces non-conducting time of LEDs to enhance power factor (PF) and total harmonic distortion (THD). The flicker can also be relatively reduced. By using current limiter cells, lighting variation is eliminated with respect of the variation of AC input voltage. A worst case of a 4 W with only two LED-strings driver is implemented and tested by using a 1 um 650 V-BCDMOS high voltage process to verify advantageous characteristics of the suggested scheme. Experimental results demonstrate a PF of 0.97 with a THD of 24.62% and an efficiency of 87.1% at a 220 V AC supply.

A novel on-chip step-dimmer for low cost AC-powered HV-LED driver

“…Secondly, the power (in Watts) of the works can be customized in the design process without changing the performance of the circuits. For instance, to increase the power in this work, either the dimming voltage can be Table I, the proposed design can gain a very high PF and a low THD as compared with the non-dimmable designs in [1,2,3]. In comparison with the dimmable AC LED driver reported in [4], the proposed design owns the similar performance with a more simple circuit structure.…”

“…Recently, various non-isolated AC-powered LED drivers with multiple LED strings have been introduced, enabling a high power factor (PF), a low total harmonic distortion (THD) as well as lows crest factor [1,2,3]. However, the dimming function which is important for a light source that the luminance can be adjusted is not available on these AC LED drivers.…”

Low Cost, High Power Factor, Dimmable, Monolithic AC-Direct LED Driver with on-Chip Step-Dimmer for Outdoor Lighting Applications

“…The LCRs are turned on in a sequence and this process repeats in the next cycles. Additionally, it is noticeable that the power processing core owns a self-adaptive mechanism; hence, there is no need of any additional controller as in the designs reported in [4,5]. Furthermore, since only one LCR turns on at a certain period, the loss power is minimized in order to increase the power efficiency.…”

“…Recently, there have been studies of high PF, low THD AC-directly-powered LED drivers reported in the literature [4]- [6]. Although these AC LED drivers can achieve a very high performance, they also have several shortcomings.…”

“…Although these AC LED drivers can achieve a very high performance, they also have several shortcomings. With the design proposed in [4], it is a simplest and most cost-effective scheme since the design is constructed with a lowest number of components; however, as the number of LED strings increases, the design shows a difficulty of realizing the switching function. Another design reported in [5] shows a high PF with a dimming feature; however it is very complicated in implementing the design with expensive blocks which degrades its robustness.…”