Active Input Current Shaper Research Articles

Active Input Current Shaper Without an Electrolytic Capacitor for Retrofit Lamps Applications

The evolution of solid-state lighting technology has transformed traditional solutions in lighting. High-brightness light-emitting diodes (HB-LEDs) have become very attractive light sources due to their excellent characteristics, namely high efficiency, a long lifetime, and low maintenance. It is evident that HB-LED drivers must be durable and efficient in order to enjoy these advantages. Moreover, to replace incandescent bulbs, the ac-to-dc HB-LED driver must be simple and have low size and comply with international regulations (i.e., injecting low-frequency harmonics into the mains supply). With the last modifications regarding low-power lighting equipment (i.e., <; 25 W), the authors have traditionally focused their efforts on increasing efficiency by sacrificing sinusoidal input current, yet all their solutions obviate the suppression of the traditional electrolytic capacitor of ac-to-dc converters, highlighting that this is the price to pay for a simple and low-size solution. This paper, however, puts forward the design of a simple and low-size ac-to-dc HB-LED driver for retrofit lamps without an electrolytic capacitor in order to extend its lifetime. The solution proposed here derives from a well-known technique used in the past, the active input current shaper (AICS), but without an electrolytic capacitor in this case. If the electrolytic capacitor of an AICS is removed, then low-frequency ripple arises at its intermediate dc bus, adding some distortion in the line input current over the proper natural one of an AICS. However, this addition is slight in comparison to the proper natural distortion of AICSs. Moreover, the low-frequency ripple at the intermediate bus is not transferred to the output with the help of the rapid output dynamic response of the AICS, which prevents flicker. This paper presents a theoretical analysis that guarantees a compromise between compliance with international regulations and the use of capacitor technologies other than the electrolytic design. Finally, a 24-W experimental prototype has been built and tested to validate the theoretical results presented in this paper.

Modeling of an AC-to-DC Converter With a Single-Stage Power Factor Corrector

For years, many authors have done new proposals about the use of single-stage solutions to meet IEC 61000-3-2 regulations. These kinds of topologies can reduce the harmonic content without excessively penalizing the efficiency of the converter. Furthermore, although they are called single-stage topologies, actually, they are not exactly single-stage converters because a part of the energy is processed twice. As a consequence, the small-signal model is not evident at all because the energy flow in the converter is quite complex. This paper deals with the dynamic model of a half-bridge converter with an active input current shaper. Both a small-signal model and a large-signal model have been obtained, and the results were compared with those of a real prototype. The experimental results of the dynamic behavior are also presented.

A Different Approach to Implement an Active Input Current Shaper

In recent years, several AC/DC converters have been presented in order to meet the power quality regulations, while maintaining the lowest number of components with the purpose of minimizing the cost and complexity; for this purpose the active input current shaping technique was proposed. A new active input current shaper (AICS) is presented. Differently from the traditional series AICS, the proposed scheme connects the auxiliary output of the main converter in parallel with the rectified AC mains instead of the series connection. The proposed parallel scheme demands a current with a low harmonic content where the standard specifications are fulfilled. The operation, simulation, and experimental results of the proposed scheme are presented.

Low-power flyback converter with synchronous rectification for a system with AC power distribution

IEC 1000-3-2 regulations impose a reduced harmonic content on any converter with an input power higher than 75 W. However, if the power architecture of the system is based on small on-board converters, and the total power is higher than 75 W, IEC regulations must be fulfilled although each individual converter need not comply with the regulations. In this paper, one of the different possible solutions is presented. Each on-board converter has an active input current shaper (AICS) in order to reduce the input current harmonic content of each converter and, hence, to comply with IEC 1000-3-2 regulations. Moreover, two different types of AICSs were compared: the conventional one and a new type of AICS based on a full-wave rectifier.

Improved active input current shapers for converters with symmetrically driven transformer

This paper deals with the analysis of new implementations of the recently proposed active input current shaper (AICS). Using these implementations, the size of the AICS inductors used in AC-to-DC converters based on "symmetrically driven" DC-to-DC topologies (e.g., half bridge, push-pull, or full bridge) can be reduced and even integrated in only one magnetic core. As in the case of other converters with the AICS, the new implementations allow us to reduce the line current harmonics in order to comply with the IEC 1000-3-2 specifications, maintaining all the features of the standard DC-to-DC converters (e.g., fast transient response). Finally, the four proposed implementations of the AICS have been experimentally tested.