Modelagem e projeto de um conversor ressonante LLC para o acionamento de LEDs utilizando uma metodologia de elevada acurácia

Abstract

This work presents a high accuracy methodology for designing LLC resonant converter applied to LED driving. This technique has been considered for analyzing and designing a dc-dc LLC resonant converter used as a second stage in an o -line LED driver. The proposed accurate mathematical modeling (MMA) has been used to adjust the switching frequency of the resonant converter in order to compensate the errors caused by the First Harmonic Approximation (FHA) design approach. The proposed methodology is based on the mathematical analysis of the converter together with numerical algorithms to solve a set of equations that describe the driver behavior. In addition, an investigation regarding which design parameters in uence the LED low-frequency (LF) current ripple has been carried out. Based on this analysis, a novel design methodology that allows for the attenuation of the LF current ripple has been devised. The proposed model has been employed to determine the low-frequency current ripple transmission on the LLC resonant converter and to properly design the bus capacitance of the LED driver, which also has a rst stage based on the boost power factor pre-regulator. In order to perform the control of the converter, the small-signal modeling of the studied topology was developed. The proposed model was based on existing methodologies presented in the literature and also on the contributions of the accurate modeling, seeking a reliable description of the dynamic behavior of the converter. The validation of the accurate mathematical model, the proposed design methodology and the designed control system was carried out by means of computational simulations and experimental implementations in a 46-W prototype fed from a 127-V ac grid.