Thermal or energy harvesting battery charger w/ additional buck converter

The device is designed to efficiently extract microwatts (µW) to milliwatts (mW) of power generated from a variety of high output impedance DC sources like photovoltaic (solar) or thermal electric generators (TEG) without collapsing those sources. The battery management features ensure that a rechargeable battery is not overcharged by this extracted power, or depleted beyond safe limits by a system load.

In addition to the highly efficient boosting charger, the bq25570 integrates a highly efficient, nano- power buck converter for providing a second power rail to systems such as wireless sensor networks. Output voltage from this converter is set at 3.3V.

Ultra Low Power DC-DC Boost Charger

  • Cold-start Voltage: VIN ≥ 330 mV
  • Continuous Energy Harvesting From VIN as low as 100 mV
  • Input Voltage Regulation Prevents Collapsing High Impedance Input Sources
  • Full Operating Quiescent Current of 488 nA

Energy Storage

  • Energy can be Stored to Re-chargeable Li-ion Battery, Super- capacitors or Conventional Capacitors
  • Battery Charging and Protection
  • Internally Set Undervoltage Level
  • User Programmable Overvoltage Levels
  • Battery Good Output Flag
  • Programmable Threshold and Hysteresis
  • Warn Attached Microcontrollers of Pending Loss of Power
  • Can be Used to Enable or Disable System Loads
  • Programmable Step Down Regulated Output (Buck)
  • High Efficiency up to 93%
  • Peak Output Current up to 110 mA
  • Programmable Maximum Power Point Tracking (MPPT)
  • Provides Optimal Energy Extraction From a Variety of Energy Harvesters including Solar Panels, Thermal and Piezo Electric Generators

Settings calculator and schematic can be found on my Github.

Mode selection

BQ25570_jumpers.png 

With the first solder jumper solar or thermal inputs are selected. Secondary buck converter can be turned off with the second solder jumper. Vout turns off with this selection.


Storage

BQ25570_storage.png


On the board there is a LiR2450 socket. There are also two sockets for optional 2.7V super capacitors.

Dimensions of the board are: 38mm x 44mm