Shunt charger systems harvest power and protect battery packs

November 25, 2011 // By Steve Knoth, Linear Technology Corporation
Energy harvesting ICs can convert an appropriate transducer's output into an electric current for a battery charger device. The article describes in detail application options for Linear Technology's LTC4070 charger IC which, among other, has been designed for embedded automotive applications.

can convert an appropriate transducer's output into an electric current for a battery charger device. Recent technology developments have pushed energy harvesting to the point of commercial viability, even though it has been emerging since early 2000. The opportunities in energy harvesting applications are widespread and include the following:


  • Replace or recharge battery powered systems in situations where battery replacement is inconvenient, impractical or dangerous
  • Eliminate the need for wires to carry power or to transmit data
  • Smart wireless sensor networks to monitor and optimize complex Industrial processes, remote field installations and building heating & cooling systems
  • Harvesting otherwise wasted heat from industrial processes, solar panels, internal combustion engines
  • Various consumer electronic accessory chargers.

Many of these applications inherently have intermittent or low-power sources. And, so many implementations will want to charge a battery for a backup power source.

Shunt voltage references are simple to use; they have been around for many years and are in a myriad of products. However, they cannot effectively charge a battery. To configure one to do such a task is extremely cumbersome. Moreover, the ability to accurately and safely charge a Lithium-Ion/Polymer, coin cell or a thin film battery from a low-current source or an intermittent harvested energy source has been difficult to attain.

On the battery side, although technology has improved, portable electronic device battery cells or battery packs still require protection and conditioning to keep them running optimally. Lithium-Ion/Polymer batteries are a mature technology and a popular choice to power many electronic devices due to their high energy density, low self-discharge, low maintenance, and wide voltage range, among other features. Coin cells offer high energy density, stable discharge characteristics and low weight in a small form factor. Thin film batteries are an emerging technology with such benefits as a high number of charge cycles and physical flexibility, i.e. they may be formed to fit in almost any shape depending on the

Design category: