I initially designed a circuit that would take a 12V battery as its power supply and power up a comparator circuit that would turn on/off a 12V fan based on temperature. This 12V battery could have been anywhere between 11.58-14.4V due to dis/charge so I regulated it with an LM7812, no worries. Comparator circuit uses LM358, NTC thermistor and a BJT for turning fan on/off.
Now my requirements have changed: The circuit will be supplied from a 48V battery that will have a voltage range of 43.2-67.2V. The load is now 48V (x4 12V computer fans in series). I have no idea how to regulate the power supply that is this high. Everything I look at, e.g. LM2576HV only goes up to 63V and Vout possibility is only ~15V.
I'm thinking of powering the comparator circuit with a 9V battery so that I don't have to drastically change all my components.
My questions are: 1. Do you know of an IC that can take this kind of Vin (43.2-67.2V) to have a Vout of 48V? Is there a simple alternative solution to this? 2. Is the 9V to power the comparator circuit a good idea? Will have to adjust the resistors so the LM358 opamp can turn on/off at values I want and pretty sure it can be supplied by 9V. 3. With the increased supply and load, will my current BJT be able to handle the change. It's a BDX53C and the load will be 1.11A.