The use of solar photovoltaic (PV) energy sources is increasing due to global warming concerns on the one hand, and cost effectiveness on the other. Many engineers involved in power electronics find solar power tempting and then addictive due to the ‘green’ energy concept. The circuit discussed here handles up to 4 amps of current from a solar panel, which equates to about 75 watts of power. A charging algorithm called ‘pulse time modulation’ is introduced in this design. The current flow from the solar panel to the battery is controlled by an N-channel MOSFET, T1. This MOSFET does not require any heat sink to get rid of its heat, as its RD-S(on) rating is just 0.024 Ω. Schottky diode D1 prevents the battery discharging into the solar panel at night, and also provides reverse polarity protection to the battery. In the schematic, the lines with a sort-of-red highlight indicate potentially higher current paths. The charge controller never draws current from the battery—it is fully powere...