Researches on highly reliable and efficient LC LED drivers with novel Non-PWM switching techniques

Abstract

Several researches on novel passive LED driver which does not use pulse width modulation (PWM) switch-ing technique were presented in this paper. In chapter 1, A new type of passive LED driver that can reduce total harmonic distortion (THD) significant-ly by LC parallel resonance is presented. Using just one inductor and three capacitors called LC3 for LED driver, high efficiency and power factor (PF) are also achieved. The proposed LED driver has a temperature-robust characteristic because its power is a function of the number of LED ns and the operating point is so selected that the power variation is zero. This robustness is requisite for the long-time operation of the pro-posed LED driver, which has inherently very long lifetime because it is composed of passive elements only. For wide use of its LED driver in various countries that has different source voltage Vs or source frequency fs, it can be applicable to 110 V / 220 V condition or 50 Hz / 60 Hz condition. This compatibility can make it universal LED driver regardless of Vs and fs. For analyzing LED power and PF of the LED driver, phasor transformation technique is used. The proposed circuit for LED driver is the first application of it to non-linear switching case, which results in quite good agreement with simulation and experiment results. It is experimen-tally verified that the LED driver has achieved 94.8 % and 94.0 % of high efficiency in L1 = 1.0 H and 2.0 H, respectively. Furthermore, it meets PF and THD regulations when source voltage variation is applied to ± 6 % of 220 V, though using reasonably small filter size In chapter 2, static power regulation LED driver that can regulate LED power statically by using multi-stage switching circuit is newly proposed in this paper. Passive type LED driver using just passive components cannot regulate LED power since it doesn’t have active components to control. Static LED power regulation is realized by changing the number of LED, which concept is...