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EETE MAY 2014 High-Performance, high reliable Power Supplies 15 W to 12 kW+ adapted to your challenging projects l AC/DC Power Supplies l Rectifiers and Battery Chargers l DC/DC Converters l Sine-Wave Inverters l Phase and Frequency Converters l AC- Input, DC-output UPS systems l Open Frame l Wall mount l 19” Cassettes l DC-input dimmable back-light inverters for LCD displays l Complete Power Systems in 19" and 23" Racks ABSOPULSE Marketing Europe GmbH PoBox 1501 8620 Wetzikon CH Tel. +41 78 896 50 49 Fax +41 44 944 38 44 Write us: See us: Printed Electronics—We Build the Market Exhibition: May 27 – 28, 2014 Conference: May 26 – 28, 2014 Messe München, Germany Neale Cousland / Heliatek GmbH (middle), Karl Knauer KG (below) ©: Organic solar cell: Fraunhofer ISE Holst Centre (above), Top trends. Key innovations. Expert speakers. Register now! 6th International Exhibition and Conference for the Printed Electronics Industry Fig. 3: With Partial Shading, More Complex Power Curves Exist for a Solar Panel Electronic Engineering Times Europe May 2014 27 LOP14 Anzeige_91x136_EETimes_E.indd 1 01.04.14 11:04 There are also other design problems encountered with solar charging systems. For any given solar-powered system, firmware development and debug can take a huge amount of time. A more complex buck-boost topology is needed if the panel’s optimal power delivery point can be below, equal to, or above the battery voltage (this is a very common scenario). A buckboost topology allows true isolation in both directions (when compared to a step-down or “buck” topology only, if the panel is dark it might drain the battery through the body diode of the NMOS through the inductor). Proper voltage termination is needed to protect the battery. Finally, since the panel is not a reliable source of power, in-situ charging of the battery (where the charger feeds the battery, and a load is connected to battery) is needed—the battery is the power source but also acts as a “buffer” in this case. What is maximum power point tracking (MPPT) and why is it needed? Maximum Power Point Tracking is a technique that helps extract the highest amount of power from the panel under all operating conditions. Some of these non-ideal operating conditions include: - Panel is partially shaded (leaves, bird droppings, shadows, snow, etc) - Panel’s temperature variation - Panel’s ageing For example, in off-grid solar panel systems, failure of the power system is costly. Customers want to extract the most power they can from the panel. Further, they want to maximize the time interval needed between maintenance visits to the solar installation. Fig. 4: LT8490 typical application circuit

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