Disturbance observer-based control of a dual output LLC converter for solid state lighting applications

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Disturbance observer-based control of a dual output LLC converter for solid state lighting applications

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Disturbance Observer-Based Control of a Dual Output LLC Converter for Solid State Lighting Applications Maurice G. L. Roes, Jorge L. Duarte and Marcel A. M. Hendrix Eindhoven University of Technology Electromechanics and Power Electronics group P.O. Box 513, 5600MB Eindhoven, The Netherlands Abstract—Feedback sensor isolation is often an expensive necessity in power converters, for reasons of safety and electromagnetic compatibility. A disturbance observer-based control strategy for a dual-output resonant converter is proposed to overcome this problem. Current control of two LED loads is achieved through estimation rather than mea- surement. Robustness against temperature changes, which have significant impact on the behaviour of the LEDs, is achieved through estimation of offsets in the forward voltages of the LED-strings. The power converter and LEDs are modelled accurately to obtain a good estimation accuracy. The whole implementation is steered towards a low cost solution. Index Terms—Disturbance observer, Light-emitting diodes, Linear-quadratic-Gaussian control, Modelling. I. INTRODUCTION Multi-coloured LED lighting applications are rapidly gaining in popularity. One solution to driving these mul- tiple LED-strings can be found in the use of a multi-output power converter. Unfortunately though, most of these con- verter topologies have a large number of components and often suffer from cross-regulation effects. The resonant dual-output LLC converter [1] (figure 1), that is used in this project does not have these problems. It has a minimal component count and has two independently controllable outputs, able to supply power to asymmetric loads. The reader is directed to the aforementioned paper for more information on the principle of operation of the converter. In a traditional current control strategy the output currents are measured and controlled via a feedback loop. This method has the disadvantage of requiring a form of isolation in the feedback path to provide an acc

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