Photovoltaic
Cell
Boost
Converter
Charge
Control
Connector
Power
Management
(2) EnerChip
CBC050
Control
Lines
V
OUT
Chapter 3
SLAU273C – January 2009 – Revised May 2010
Solar Energy Harvester Module (SEH-01)
3.1
Functional Description
The core technology behind the Solar Energy Harvesting module is the photovoltaic or solar cell that
converts ambient light into electrical energy. The energy from the solar cell must be converted, managed
and stored. This process is handled by the EnerChip EH CBC5300, the small DIP mounted board on the
Solar Energy Harvesting Module (SEH-01). A boost converter is used to increase the voltage from the
solar cell to a sufficient level to charge the thin-film battery and run the rest of the system.
The Charge Control block continuously monitors the output of the boost converter. If the output of the
boost converter falls below the voltage needed to charge the EnerChip, the charge controller disconnects
the boost converter from the system to prevent back powering the boost converter in low light conditions.
The Power Management block prevents the EnerChip from discharging too deeply in low-light conditions
or under abnormally high current loads. It also ensures that the load is powered up with a smooth
power-on transition. The Power Management block has a control line, CHARGE, which indicates to the
MSP430 that the solar energy harvester is actively charging the EnerChip. The control line input,
BATOFF, is available for the MSP430 to isolate itself from the EnerChip to conserve battery life in
prolonged low-light conditions.
The Solar Energy Harvesting Module features two EnerChip batteries mounted on the board with a
100-
m
Ahr capacity and a 1,000-
m
F capacitor for high-current pulses during wireless transmissions.
Using the power management status and control signals on the SEH-01, the firmware on the MSP430 has
been written to make the application 'Energy Aware' to maximize the overall lifetime of the system.
Figure 3-1. Solar Energy Harvester Module (SEH-01) Block Diagram
3.2
Solar Energy Harvester Module (SEH-01) Figure and Description
shows the connections to the Solar Energy Harvester module.
13
SLAU273C – January 2009 – Revised May 2010
Solar Energy Harvester Module (SEH-01)
Copyright © 2009–2010, Texas Instruments Incorporated
