Ultra-Low Percentage Flicker High-Efficiency Direct AC LED Driver Using Constant Power Technology

Abstract

According to California's 2016 Building Energy Efficiency Standards, the percentage flicker of light-emitting diode (LED) lighting fixtures should be below 30 %. However, the percentage flicker of commercially available linear power supplies is generally between 25 % and 99.9 %; thus, some LED lighting fixtures that use linear power supplies have been unable to enter the European or American markets. The traditional method of effectively reducing flicker involves increasing the capacitance of the electrolytic capacitor of the power supply, which causes an increase in the height of the lamp board components as well as shadowing and dark band phenomena. This paper presents a power supply circuit that uses only electrolytic capacitors with low capacitance and exhibits constant power, constant light output, and a lamp board thickness of only 8 mm; it can achieve a percentage flicker of less than 10 %, which exceeds international standards. Power efficiency is a crucial performance indicator of linear power supplies. Because linear power supplies are mostly integrated circuits (ICs) with extremely small package volumes, higher power efficiency results in lower heat loss. The international standard for the power efficiency of linear power supplies is approximately 75 %. A multistage switching mechanism is used in the proposed power supply to achieve an overall efficiency of > 88 %. Under an input power of 12 W, a 10 % increase in efficiency reduces the heat by 1.2 W, which can considerably reduce the difficulty and cost of heat dissipation in IC packages. By combining the aforementioned technologies, the proposed power supply can achieve high efficiency and low percentage flicker, thereby improving the shortcomings of traditional linear power supplies. Currently, the driver-on-board (DOB) module of the proposed power supply is in the trial production phase, and its market entry will be accelerated to expand the market share of linear power supplies.INDEX TERMS High efficiency, linear converter, percentage flicker, constant power, DOB.