A super-efficient boost charger for nano (ultra-low) power energy harvesting targets power sources such as solar, thermal electric, electromagnetic and vibration. Besides managing power these devices generate, the chip also stores the extracted energy in various storage elements, including Li-ion batteries and super capacitors.
Dubbed the bq25504, the chip includes circuitry to protect the energy storage element from over voltage and under voltage conditions and to kick-start the system when the battery is deeply discharged. Among the most notable features of the device is its quiescent current, a mere 330 nA typical, claims its supplier Texas Instruments Inc. It can harvest energy from sources providing input voltages of just 80 mV, claims TI. Its cold-start voltage is typically 330 mV.
TI says that in a solar panel powering a handheld device picking up indoor light, for example, the new boost charger increases the usable harvested energy by 30 to 70% compared to a linear regulator. The device should be particularly helpful in wireless sensor networks (WSN) for area, industrial, water/waste and structural monitoring, along with consumer, high reliability and medical applications, says TI.
“Wireless sensor networks have been limited in their execution due to the cost associated with maintaining and replacing the batteries within sensor nodes,” said Sami Kiriaki, senior vice president over TI’s Power Management business. “With the bq25504 boost charger, the nodes can power autonomously, which can reduce the operating cost and thereby make ultra low-power wireless sensor networks cost-effective in more applications, such as industrial monitoring of hazardous or restricted areas.”
Conversion efficiency of the device is greater than 80%. Built-in maximum power point tracking (MPPT) optimizes energy extracted from dc harvesters, such as solar panels under varying light conditions and thermo electric generators (TEG) under varying thermal conditions.
User-programmable settings allow the boost charger IC to be used with a variety of energy sources and energy storage elements, such as different battery chemistries or super capacitors. Low cold-start voltage, typically 330 mV, lets the bq25504 start up from single-cell solar panels under low light, as well as from TEGs with low temperature differences and other low-voltage sources.
More information or to order samples of the bq25504: www.ti.com/bq25504-pr
bq25504 Evaluation Module: www.ti.com/bq25504evm-pr
bq25504 EVM User’s Guide: www.ti.com/bq25504evmuser-pr