DIY SolarThe dc to dc step down converter also known as a buck converter can efficiently bring down voltage. But in the case of solar panels there is a big difference which it cannot control. That is the panels output voltage. MPPT charge controllers can keep the panel voltage at its maximum power point and extract the maximum amps. But unfortunately buck converters can’t hold the panel voltage at its maximum power point. This causes the panel voltage to drop. Once the panel voltage drops the buck converter cannot increase the amps. Even if it rises it is only slightly better than a pwm controller. But again it depends on your solar panel combination. If you have a higher power and voltage panel then you can get visibly better amps from the system.
Credit DIY Sustainable Living