AN4123 Datasheet, PDF (1/17 Pages) STMicroelectronics – The STEVAL-ISV015V1 is a demonstration board mounting

AN4123
Application note
STEVAL-ISV015V1 up to 2.5 W solar USB charger
By Domenico Ragonese
Introduction
The STEVAL-ISV015V1 is a demonstration board mounting the SPV1040 device (solar
energy harvester) as input stage and the LD39050PUR device (low noise and low quiescent
current voltage regulator) as output stage. It targets any portable application powered by
USB supply and merges the capability of the SPV1040 device to maximize the power
extraction from solar modules with the high precision voltage regulation of the LD39050
device. It is shown in Figure 1.
Figure 1. STEVAL-ISV015V1 demonstration board
The board has been designed to harvest power from PV panels and to supply loads
requiring up to 2.5 W (5 V, 500 mA) through a mini-USB (B type) connector. Between the
two stages, a 440 mF super capacitor stores the harvested energy even when load is not
connected or, if connected, it needs less power than that available from the source.
The application components at the input stage have been selected to optimize the energy
harvesting from polycrystalline PV panels composed of 2, 3 and 4 PV cells in series and
able to supply up to 900 mA. The trimmer VR3 is connected between the PV panel and the
MPP-SET pin of the SPV1040 device and allows the maximum power extraction from the
selected PV panel to be fine tuned. Setting the VR3 = 1 kΩ is recommended to cover most
application cases. So, other PV panels can also be used but it may be necessary to replace
some of the application components in order to make the system work in the most efficient
way. The PV panel and main application components can be replaced, but the following
guidelines must be carefully considered:
• The PV panel can be selected as long as V_OC < 5.5 V and I_SC < 1.65 A
• The inductor L1 can be replaced by considering that it affects the maximum peak current
and that an input overcurrent limit (1.65 A) does not have to be triggered
• The maximum output current can be limited by inserting the current sensing resistor RS1
(0 Ω by default)
For further details on component selection, please refer to Section 6 “External component
selection” of the AN3319 application note. For details on the SPV1040 device and the
LD39050 device features, please refer to the related datasheets.
March 2013
DocID023264 Rev 2
1/17
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