AC-DC Boost Power Factor Correction Research Articles

Peak Current Control-Based Power Ripple Decoupling of AC–DC Multichannel LED Driver

AC–DC light-emitting diode (LED) drivers suffer from short lifetime because of the low-lifetime electrolytic capacitors used for dc bus decoupling. In this paper, a primary-side peak current control method applied for driving a two-stage multichannel LED driver is proposed. The LED driver consists of an ac–dc boost power factor correction stage and an isolated dc–dc nonresonant stage. A long-lifetime and small film capacitor is used for implementing the intermediate dc bus. The proposed method, which controls the peak value of the primary-side current of the transformers, is applied to the dc–dc stage to ensure constant dc current output of LEDs in spite of the widely varying dc bus voltage due to low bus capacitance. The proposed method compensates the effect of the large dc bus voltage ripple by varying the switching frequency of the primary-side switches. Detailed design procedure, theoretical analysis, and experimental results of the LED driver operating at 180 W with the proposed method are provided. The LED driver with the proposed control method is proved to have high overall efficiency.

Efficiency Improvement of Multichannel LED Driver With Selective Dimming

There is a widespread application of selective dimming of multichannel LED drivers. In this article, two new selective dimming methods to improve the efficiency of multichannel LED drivers are proposed. The proposed methods are based on a two-stage multichannel LED driver that consists of an ac–dc boost power factor correction converter at its front-end and a dc–dc non-resonant converter at its second stage. Primary side digital peak current control method is applied to the dc–dc converter to control the LED peak currents during selective dimming operation. The auxiliary back-to-back switches are connected across each transformer winding either at the primary side or secondary side to perform selective dimming. The duty ratios of these auxiliary back-to-back switches are varied at lower than switching frequency of dc–dc converter to control the brightness of LED loads. The proposed topologies offer high efficiencies in both full load and during selective dimming operations, and meet the IEEE 1789 recommendation with 3 kHz dimming frequency. The design of the proposed dc–dc converters, modes of operation as well as detailed theoretical analysis are presented in this article. A 150-W prototype of the proposed LED driver with a non-DSP microcontroller is implemented to verify the feasibility of such LED drivers. Comparisons between the proposed methods and the converters reported previously are presented in the article.

Inductive decoupling‐based multi‐channel LED driver without electrolytic capacitors

Light-emitting diode (LED) drivers in outdoor street lighting applications suffer from short-lifetime because of the prolonged exposure to harsh environmental conditions such as high operating temperature, high humidity etc. A long-lifetime multi-channel LED driver consisting of front-end AC–DC boost power factor correction (PFC) converter followed by a DC–DC power conversion stage with dimming capability for LED-based street light is proposed in this study. This LED driver uses an inductor-based auxiliary decoupling circuit at the output of the AC–DC converter for mitigating the double-line-frequency power ripple present in the DC bus. The inductive ripple power storage circuit has a longer lifetime than a conventional capacitive storage circuit which is usually implemented by electrolytic capacitors. A digital control method is proposed to realise the decoupling control along with PFC control by a single non-digital signal processor micro-controller ST STM32F103RBT6. The proposed LED driver for street lighting is analysed and validated on a 150 W test setup. A comparison of active decoupling AC–DC converters for eliminating secondary-harmonic power ripple is displayed.

Peak Current Control of Multichannel LED Driver With Selective Dimming

A novel selective dimming method of the output channels of a multichannel LED driver is proposed in this paper. This LED driver comprises a front-end ac-dc boost power factor correction converter followed by symmetric half-bridge isolated nonresonant dc-dc converter and symmetric voltage-multiplier rectifier with purely capacitive output filters. By controlling the duty ratios of the secondary side switches, which are strategically placed at the output voltage-multiplier-based rectifiers, the average LED current and hence the brightness of individual channels are controlled. Moreover, a unique primary side peak current control is implemented to control the peak currents of LEDs during pulsewidth modulation dimming, which prevents electromigration-related fast aging of the LEDs. This driver also has the advantages of high power (>120 W) operation capabilities, and high efficiency (>94%) with primary side switches zero voltage switching turning on and secondary side rectifier diodes zero current switching turning off. A detailed analysis and design procedure of the proposed converter is presented. To validate the analysis, an industry-standard 150 W prototype is developed, which is digitally controlled by a cost-effective non-DSP microcontroller. The experimental results are in perfect agreement with the claims. A comparison for universal ac input and isolated LED drivers with selective dimming is displayed.