Light-emitting diodes (LEDs), as an emerging lighting source with several supreme benefits, are edging out their conventional counterparts throughout the world. In order to take advantages of the benefits offered by LEDs, the driver circuits with high power conversion efficiency, sufficient lifetime, and minimized system size and cost are required. Among a variety of AC input LED drivers, the inductor-less linear driver emerges as a promising solution because it not only shows great potential to achieve system miniaturization with low cost but also is free from the substantial switching losses. However, there are remaining issues for the existing inductor-less drivers, such as the harmful optical flicker and the poor energy utilization for powering the low voltage controller.

The first...[ Read more ]

Light-emitting diodes (LEDs), as an emerging lighting source with several supreme benefits, are edging out their conventional counterparts throughout the world. In order to take advantages of the benefits offered by LEDs, the driver circuits with high power conversion efficiency, sufficient lifetime, and minimized system size and cost are required. Among a variety of AC input LED drivers, the inductor-less linear driver emerges as a promising solution because it not only shows great potential to achieve system miniaturization with low cost but also is free from the substantial switching losses. However, there are remaining issues for the existing inductor-less drivers, such as the harmful optical flicker and the poor energy utilization for powering the low voltage controller.

The first part of this research work, including two developed inductor-less LED driver prototypes, is to overcome the above issues for efficient lighting. In the first design, a quasi-constant power control scheme is proposed to mitigate over 80% of the harmful optical flicker at the double-line frequency while the 87.3% efficiency and an over 0.9 power factor are maintained. In the second design, a multi-source power supply scheme is proposed for improving the power conversion efficiency from the high voltage nodes to the low voltage controller IC. The proposed approach effectively utilizes the jointed nodes on the LED string, which are naturally provided by the topology of the inductor-less driver, so it does not introduce extra expensive and bulky components. The measured results verify the effectiveness of the proposed scheme, showing that the system efficiency is improved 2.1% and 3.8% for low flicker mode and high PF mode, respectively, at around 5-W output power.

In the second part of this research work, the lighting technology beyond efficient general lighting is also investigated. An inductor-less driver prototype is developed with the integration of a visible light communication (VLC) technique for simultaneously providing illumination and data transmission. The proposed driver has less power conversion stages and does not have passive components speed limitation. Besides this, the harmful flicker is further mitigated below 10% with an accurate 1/x circuit and the dimming compensation method. The keep-and-restore technique and auxiliary turn-on switch help to improve the VLC data rate. The driver supports up to 8-Mpbs on-off keying non-return-to-zero data transmission.

All prototypes in this thesis are implemented with a 0.35-μm 120-V high voltage CMOS process.