  This paper presents design of a Maximum Power Point Tracking (MPPT) circuit
and its functionality for tuning the maximum power transfer from an energy
harvester (EH) unit. Simple and practical Perturb and Observe algorithm is
investigated and implemented. We describe the circuit functionality and the
improvements that have been introduced to the original algorithm. The proposed
MPPT design is divided into three main blocks. The output signal is being
generated by the PWM or PFM block. The tracking speed has been enhanced by
implementing a variable step size in the Tracking Block. Finally, the overall
power consumption of the MPPT circuit itself is controlled by the Power
Management Block, which manages delivering the clock signal to the rest of the
circuit. The RTL code of the proposed MPPT has been described in Verilog, then
has been synthesized and placed-and-routed in a general purpose 130nm CMOS
technology.
