A photovoltaic power management system using a luminance-controlled oscillator for USN applications

This paper presents a power management system of the dye-sensitized solar cell (DSSC) for ubiquitous sensor network (USN) applications. The charge pump with a luminance-controlled oscillator regulates the load impedance of the DSSC to track the maximum power point (MPP) under various light intensities. The low drop-out regulator with a hysteresis comparator supplies intermittent power pulses that are wide enough for USN to communicate with a host transponder even under dim light conditions. With MPP tracking, approximately 50% more power is harvested over a wide range of light intensity. The power management system fabricated using 0.13 μm CMOS technology works with DSSC to provide power pulses of 36 μA. The duration of pulses is almost constant around 80 μs (6.5 nJ/pulse), while the pulse spacing is inversely proportional to the light intensity.