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  Battery Charger's Unique Input Regulation Loop Simplifies Solar Panel Maximum Power Point Tracking &mdash LT Journal
  PDF, 854 Kb, File published: Jan 18, 2011
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  Battery Charger’s Unique Input Regulation Loop Simplifies
  Solar Panel Maximum Power Point Tracking
  Jay Celani Solar panels have great potential as
  energy harvesting power sources—they
  just need batteries to store the harvested
  power and to provide carry-though during dark periods. Solar panels are relatively expensive, so extracting maximum
  power from the panels is paramount to
  minimizing the panel size. The tricky part
  is a balancing of solar panel size with
  required power. The characteristics of
  solar panels require careful management
  of the panel’s output power versus load
  to effectively optimize the panel’s output
  power for various lighting conditions. (see FigureВ 1). Maintaining this peakpower point during operation as lighting
  conditions change is called maximum
  peak power tracking (MPPT). Complex
  algorithms are often used to perform this
  function, such as varying the panel’s load
  periodically while directly measuring panel
  output voltage and output current, calculating panel output power, then forcing
  the point of operation that provides the
  peak output power as illumination and/or
  temperature conditions change. This type …

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  Designing a Solar Cell Battery Charger &mdash LT Journal
  PDF, 306 Kb, File published: Dec 1, 2009
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  L DESIGN FEATURES Designing a Solar Cell Battery Charger
  by Jim Drew LT3652 Input Voltage
  Regulation Loop The input voltage regulation loop of the
  LT3652 acts over a specific input voltage range. When VIN, as measured via a
  resistor divider at the VIN_REG pin, falls
  12 2.4 24 2.2 IPANEL (A) 22 1000W/m2 2 20 1.8 18 1.6 16 1.4 14 1.2 12 1 10 0.8 8 0.6 6 0.4 4 0.2
  0 100W/m
  0 2 4 2 2 6
  8
  10
  VPANEL (V) 12 14 16 0 Figure 1. A solar cell produces current in proportion to the amount of sunlight falling on it, while
  the cell’s open-circuit voltage remains relatively constant. Maximum power output occurs at
  the knee of each curve, where the cell transitions from a constant voltage device to a constant
  current device, as shown by the power curves. below a certain set point, the charge
  current is reduced. The charging current is adjusted via a control voltage
  across a current sensing resistor in
  series with the inductor of the buck
  regulator charging circuit. Decreased
  illumination (and/or increased charge
  current demands) can both cause the
  input voltage (panel voltage) to fall,
  pushing the panel away from its point
  of maximum power output. With the …

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  Solar Battery Charger Maintains High Efficiency in Low Light &mdash LT Journal
  PDF, 3.0 Mb, File published: Oct 9, 2013
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  Solar Battery Charger Maintains High Efficiency in Low Light
  J. Celani An important characteristic of any solar panel is that
  it achieves peak power output at a relatively constant
  operating voltage (VMP) regardless of illumination level (see
  FigureВ 1). The LT3652 2A battery charger exploits this
  characteristic to maintain a solar panel at peak operating
  efficiency by implementing input voltage regulation (patent
  pending). When available solar power is inadequate
  to meet the power requirements of an LT3652 battery
  charger, input voltage regulation reduces the battery
  charge current. This reduces the load on the solar panel
  to maintain the panel voltage at VMP, maximizing the
  panel output power. This method of achieving peak panel
  efficiency is called maximum power point control (MPPC).
  While MPPC optimizes solar panel efficiency during periods of low illumination, the power conversion efficiency of
  the battery charger suffers when power
  levels are low, degrading the overall power
  transfer efficiency from the panel to the
  battery. This article shows how to improve
  battery charger efficiency by applying
  a simple PWM charging technique that
  forces the battery charger to release energy
  in bursts when power levels are low. …

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Manufacturer's Classification

• Power Management > Battery Management > Battery Charger IC > Switching Battery Chargers
• Power Management > Energy Harvesting