| dc.description.abstract | This work presents several contributions to the modeling, analysis, design, and control of the LLC
resonant LED driver. Initially, the LLC resonant LED driver dynamic model accuracy is improved by
taking into account under the modeling the LED non-linear electrical behavior instead of its equivalent
load resistance. The extended describing function approach is employed. Simulation results show the
feasibility of the proposed model, which predicts the real dynamic behavior of the LLC resonant LED
driver when it operates around the main resonance. For the operation beyond the main resonance, the
predicted behavior deviates from the real response. Afterward, the contribution to the LLC analysis is
given by the proposed time-domain (TD) analysis, where the direct TD solution from the state-space
representation is employed. The TD solution overcomes the classical first harmonic approximation
(FHA) problem, which presents errors when the switching frequency ( fsw) is beyond the LLC series
resonance. Compared to the TD procedure reported in the literature, the developed methodology
presents a reduced number of assumptions, ensuring leading accuracy. Experimental results show an
outstanding accuracy of the proposed method regardless of the operating condition (filter, load, input,
etc.). Following, employing the proposed TD solution, a new design procedure for the LLC resonant
LED driver is derived. This design procedure relies on the weighted-average-efficiency concept.
Besides, different constraints are assessed to ensure zero voltage switching (ZVS), zero current
switching (ZCS), enough power gain, and a practical fsw range over a wide operating window.
Experimental results show the feasibility of the proposed design procedure, achieving high efficiency,
ZVS, ZCS, and feasible fsw range over the whole operating range. The peak efficiency of 96.44% is
achieved. In comparison to the classical design, the efficiency is improved up to 4.3%. Regarding the
control system, the contribution is given by the proposal of a new hybrid dual-loop controller for the
LLC resonant converter implementing the downstream DC/DC stage in an offline two-stage
electrolytic-capacitor-free and flicker-free LED driver. The proposed controller is given by a PI
subsystem and an adaptive periodic disturbance rejection subsystem, comprehending the proposed
PI&APDR controller. Experimental results and simulation analysis show the outstanding performance
of the proposed controller in comparison to conventional counterpart resonant-based controllers.
Employing the PI&APDR controller the LED current DC reference is tracked over a wide operating
range, even under parametric variations such as average bus voltage, resonant tank elements, and LED
module. Besides, enhanced performance is achieved in reducing the output current ripple raised from
the bus voltage ripple, where different bus voltage ripple frequencies are also considered. Furthermore,
even employing non-linear adaptive controllers, the PI&APDR preserves the feature of having a simple
design and implementation. | |
