Many autonomous sensor nodes use small photovoltaic (PV) panels oriented towards the direction that provides the highest energy yield in the worst-case scenario. Since all those panels operate at similar irradiance and temperature conditions, they can be properly biased at the same bias point by using a single maximum power point tracker (MPPT). But in those applications involving several PV panels with dissimilar orientations, using an MPPT tailored to each panel would increase system cost. A better design option is to implement the MPPT with a single multiple-input converter (MIC) shared through time-division multiplexing (TDM) control. However, existing TDM controls are usually based on pulse width modulation (PWM) converters wherein the high switching frequency of transistors results in power losses that are excessive for low-power systems. Consequently, low-power MPPTs are usually based instead on pulse frequency modulation (PFM) converters. This paper proposes a novel TDM control method for MPPTs based on PFM converters.

Peer Reviewed