The LED driver compatible with electronic ballasts by variable switched capacitor

An LED driver compatible with most electronic ballasts commercially used now is newly proposed, which adopts a variable switched capacitor by controlling switching duty cycle for the LED power regulation. The resonant frequency of the LC resonant tank of electronic ballasts can be appropriately controlled, which makes the proposed LED driver be versatile for electronic ballasts for various switching frequencies. In this way, the fluorescent lamp can be replaced with an LED lamp, where the electronic ballast in the lighting infrastructure remains unchanged. The zero voltage switching is applied for the variable switched capacitor in the electronic ballast, operating at the frequency of 30 ~ 60 kHz. Neither an inductor nor a transformer is introduced in the proposed LED driver, which leads to compact size and high efficiency. Furthermore, no electrolytic capacitor is used, which is beneficial for the long lifetime of LED drivers. A prototype LED driver of 16 W was implemented and verified for the three types of electronic ballasts that are most popular in markets. The LED power was well regulated for a wide range of the source voltage variation of 180 ~ 270 V, and the power efficiencies of the proposed LED driver were 95.8%, 96.1%, and 94.1% for the instant start, rapid start, and programmed start types of the electronic ballasts, respectively.