Susie Maestre

user Electronics Engineer

city Innovuze Solutions Inc.

  • Battery Charger Module for Energy Harvesting

  • Created: Apr 03, 2016

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Electrical power, nowadays, has been very vital need to everyday convenience of people. However, most of the processes that involve energy conversion have drawbacks and are not as efficient as you thought it would be. The best-known energy harvesting collectors are large solar panels and wind generators, which have become major alternative energy sources for the power grid. On the other hand, small-embedded devices rely usually on energy harvesting devices that can capture milliwatts of energy from light, vibration, or thermal sources. Devices, such as BQ25570 integrated energy harvesting Nano-Power management solution, are well suited for meeting the special needs of ultra-low power applications.

This circuit is designed to perform a stand-alone evaluation of BQ25570. The boost charger output is configured to deliver up to 4.2V maximum voltage to VSTOR. This voltage will be applied to the storage element as long as the storage element voltage at VBAT is above the internally programmed undervoltage of 2.0V. The integrated buck converter provides up to 1.8V and 100mA at VOUT. The VBAT_OK indicator toggles high when VSTOR ramps up to 3.0V and toggles low when VSTOR ramps down to 2.8V. The battery undervoltage, VBAT_UV is checked continuously to ensure that the internal battery FET, connecting VSTOR to VBAT, does not turn on until VSTOR is above the VBAT_UV threshold (2.0V). The overvoltage (VBAT_OV) setting initially is lower than the programmed value at startup and is updated after the first approximately 32ms. Subsequent updates are every approximately 64ms. The VBAT_OV threshold sets maximum voltage on VSTOR and the boost converter stops switching when the voltage on VSTOR reaches the VBAT_OV threshold. The open circuit input voltage (VIN_OC) is measured every approximately 16 seconds in order for the Maximum Power Point Tracking (MPPT) circuit to sample and hold the input regulation voltage. This periodic update continually optimizes maximum power delivery based on the harvesting conditions.

This design is applicable in a wide variety of applications especially in energy harvesting, solar chargers, thermal electric generator (TEG) harvesting, wireless sensor networks (WSN), low power wireless monitoring and environmental monitoring. This is also designed to efficiently acquire and manage the microwatts (µW) to miliwatts (mW) of power generated from a variety of high output impedance (HiZ) DC sources.