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Introduction Bipolar disorder is a severe mental disorder that has a significant negative impact on psychosocial functioning and quality of life; it is associated with high rates of suicide. There [...], Background: Multiple lines of evidence suggest that the onset and course of bipolar disorder is influenced by environmental light conditions. Increased suppression of melatonin by light (supersensitivity) in patients with bipolar disorder has been postulated as an endopheno-type by several studies. However, due to methodological shortcomings, the results of these studies remain inconclusive. This study investigated melatonin suppression in euthymic patients with bipolar I disorder using evening blue light specifically targeting the melanopsin system. Methods: Melatonin suppression was assessed in euthymic patients with bipolar I disorder and healthy controls by exposure to monochromatic blue light ([[lambda].sub.max] = 475 nm; photon density = 1.6 * [10.sup.13] photons/[cm.sup.2]/s) for 30 minutes at 2300 h, administered via a ganzfeld dome for highly uniform light exposure. Serum melatonin concentrations were determined from serial blood sampling via radioimmunoassay. All participants received mydriatic eye drops and were genotyped for the PER3 VNTR polymorphism to avoid or adjust for potential confounding. As secondary outcomes, serum melatonin concentrations during dark conditions and after monochromatic red light exposure ([[lambda].sub.max] = 624 nm; photon density = 1.6 * [10.sup.13] photons/[cm.sup.2]/s) were also investigated. Changes in subjective alertness were investigated for all 3 lighting conditions. Results: A total of 90 participants (57 controls, 33 bipolar I disorder) completed the study. Melatonin suppression by monochromatic blue light did not differ between groups ([F.sub.1,80] = 0.56; p = 0.46). Moreover, there were no differences in melatonin suppression by monochromatic red light ([F.sub.1,82] = 1.80; p = 0.18) or differences in melatonin concentrations during dark conditions ([F.sub.1,74] = 1.16; p = 0.29). Healthy controls displayed a stronger increase in subjective alertness during exposure to blue light than patients with bipolar I disorder ([t.sub.85] = 2.28; p = 0.027). Limitations: Large interindividual differences in melatonin kinetics may have masked a true difference. Conclusion: Despite using a large cohort and highly controlled laboratory conditions, we found no differences in melatonin suppression between euthymic patients with bipolar I disorder and healthy controls. These findings do not support the notion that supersensitivity is a valid endophenotype in bipolar I disorder.

Several flatness-based current controllers for three-phase three-wire boost rectifiers are compared. For this purpose, the flatness of a rectifier model is shown, and a trajectory planning algorithm that nominally achieves voltage regulation in finite time is given. The main focus lies on the inner loop current controllers. On one hand, linearization-based controllers using exact feedback linearization, exact feedforward linearization, and input-output linearization are discussed. On the other hand, two passivity-based approaches are compared. The first one is the energy shaping and damping injection method, and the other one uses exact tracking error dynamics passive output feedback. Furthermore, a reduced-order load observer is given, and a method that allows the prevention of invalid switching patterns is presented. The presented control algorithms are tested by simulations on a switched model. Index Terms--Exact feedforward linearization, flatness-based control, input-output linearization, observers, passivity-based control.

A comparison between an algebraic parameter identification algorithm for the load of a boost converter and classical asymptotic observers for the same purpose is provided. Two asymptotic observers are presented, and an algebraic identification algorithm is derived. For the latter, two implementations in the software for a digital signal processor are discussed, and experimental results are given which highlight the properties of both approaches. Index Terms--Algebraic identification, boost converter, nonlinear observers.

The paper presents a new configuration of electronic ballast for large dielectric barrier discharge lamps used in backlighting applications. The new ballast is developed for PLANON lamps, manufactured by Osram. This lamp features environmental friendliness, a long lifetime and no startup time due to external electrodes and a mercury-free Xenon gas mixture. The mainly used ballast topology is the Class-E converter. Two novel ballast topologies--the half-bridge and the full-bridge choke converter concepts--are demonstrated. Measurement results of the proposed topologies under variation of input parameters are presented. An isolated metal oxide semiconductor field effect transistor drive concept which fulfills the requirements of the ballast is developed and implemented. An equivalent circuit diagram for the lamp is determined and compared with measurement results. The proposed topologies can significantly increase the lamp's luminous efficacy compared to Class-E topology. Index Terms--Class-E converter, dielectric barrier discharge lamp, high side gate drive, metal oxide semiconductor field effect transistor (MOSFET) series connection.

Differential flatness of buck, buck-boost, and boost converter models is shown. Its benefits if used for controlling the output voltage of these converters are revealed by comparing the flatness-based control with passivity-based and linear control. Two observers for the boost converter are suggested one of which requires only the measurement of the converters output voltage. Both observers can be used with minor changes for the buck-boost converter. Two flatness-based online trajectory planning algorithms are suggested. They exploit the parametrization of the trajectories in the energy. One of them is designed to achieve fast setpoint transitions during converter start-up or despite sudden load steps while simultaneously respecting the converters physical constraints. The other one is considered for applications in power factor correction. Different stabilization strategies are compared. The viability of the observers, the algorithm, and the stabilization strategies are verified by simulations of switched nonideal converter models. Index Terms--DC-DC converters, flatness-based control, observers, passivity-based control (PBC), trajectory planning.

The three-level neutral-point-clamped voltage-source converter (NPC VSC) is widely used in high-power medium-voltage applications. The unequal loss distribution among the semiconductors is one major disadvantage of this popular topology. This paper studies the loss distribution problem of the NPC VSC and proposes the active NPC VSC to overcome this drawback. The switch states and commutations of the converter are analyzed. A loss-balancing scheme is introduced, enabling a substantially increased output power and an improved performance at zero speed, compared to the conventional NPC VSC. Index Terms--Medium voltage, power losses, three-level converter, voltage-source converter (VSC).

The paper presents a design-oriented analysis of dc-dc converters valid for both periodic and aperiodic operation. Bifurcation and statistical analysis are applied to a peak current mode controlled boost converter. The main benefit of aperiodic (chaotic) converter operation--reduction of electromagnetic interference--is discussed. Periodic and aperiodic behavior are compared. Periodic converter operation exhibits the smallest ripple waveform but the worst (purely discrete) spectrum. Aperiodic converter operation yields a broader spectrum but a larger ripple. Tradeoffs between ripple and spectrum for the practical use of chaotic dc-dc converters are suggested. The paper discusses the choice of the converter's bifurcation parameter from the ripple and spectrum points of view. Index Terms--Bifurcation analysis, chaos, dc-dc converters, electromagnetic compatibility (EMC), electromagnetic interference (EMI), statistical analysis.