Well, I know there are PWM buck-boost converters that can supply a constant voltage from a supply that may swing either above or below the target output (in this case, 13 volts.) They run significantly more money, of course, as they have to handle high current if Vin is low, and high voltage if Vin is high. However, I’m fairly sure these are made in big quantities for a limited input range, say, 8-18 volts (cutting out beyond either way) for automotive use. ??
Yes, DC-DC Buck Converters for automotive, heavy equipment, and aircraft systems. I don’t know how tight of a package you are trying to end up with or if room is an issue but did you see those I listed in #15? They are pretty cheap nowdays and other companies make similar with similar spec parameters.
We have been running two 150 watts each 38 volt 7 amp solar panels through just one of those Buck Converters extremely reliable so far. We set these panels up in pairs through one BC on it’s way to the charge controllers. We can input either 14 volts or 28 to the charge controller depending on if the system is a 12v or 24v system. And the heat sinks barely get warm in full charge conditions.
But the range capabilities of these and being adjustable is great. They can be used for just about anything you need them for and are extremely efficient.