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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 measurement. Robustness against temperature changes, which have significant impact on the behavior of the LEDs, is achieved through estimation of offsets in the forward voltages of the LED strings. The power converter and LEDs are modeled accurately to obtain a good estimation accuracy. The whole implementation is steered toward a low-cost solution.
Date of Publication: July 2011