I have an MPPT charge controller that has recently started behaving strangely and upon investigation I found a very hot mosfet and a transformer (below) that has clearly seen more heat than it should have.
The manufacturer isn't particularly helpful in providing information about this. I've been able to figure out what's going on, but not why this happened in the first place nor what is required to repair it.
From what I could determine, the particular circuit is a step-up converter that generates 15V from the original 5V. I have no idea what values are used, it is hard to decipher. The final 15V regulator is a 78l15, so I know the voltage on that end is below 35V and the current will be below 0.1A.
The input signal is a 5V 40khz square wave generated by a PIC microcontroller.
I suspect, though I'm not 100% sure yet, that this 15V is used to drive the main mosfet. This particular controller switches in the positive line (as is the proper way to do it), so a higher-than-input voltage is required. I think this is it. That's why it needs to be isolated.
My question: What would be the simplest way to replace either the whole step-up converter with another -- with the proviso that it MUST be isolated -- or to somehow replace that transformer with something off the shelf?
I do not presently have the equipment to measure inductors. I do own an oscilloscope but lack a function generator. This makes it hard to really get into it further, which is why I would also strongly consider another off-the-shelf solution to just replace the whole converter, possibly with something that's even more efficient.