Other Parts Discussed in Thread: LM51770
Tool/software:
I have been tasked with evaluating a SM72445 based 3,000W charge controller (3kW).
Output voltage is 48V nominal (52V max) and input ranges from 12 to 90VDC.
Maximum design current is 62amps.
I have reviewed the 3kW schematic as well as the SM72445EVM reference design. Both are similar circuit topology with the 3kW design using much larger FETs, Inductor, and higher current half-bridge (high and low side) gate drivers.
The SM72445 is operating with A2 set to 3.44V (Low freq, H-bridge for PM), A6 set to 2.14V (slew = 10V/1.2s, starting mode panel time not applicable, etc.), and A4 and A0 set appropriately for the circuit design.
I have followed the paths through the H bridge and confirmed there is surplus (more than enough) dead time for all FETs. There is no shoot-through.
The load is locked in at 48V with an impedance of about 50milliohms - it is always at 48V, even when the SM72445 reset pin is deactivated. In other words, the output voltage slew rate is near zero.
I began testing with my power source at 60V and 12A (the voltage will drop if more than 12A is drawn).
The MPPT drives the H bridge and the input stabilizes at 11V at 12A - moved past the peak power point of 60V and 12A. In this stable state, the SM72445 was boosting the 11V input to the 48V output. Power out was similar to the power input (no issues with excess power loss).
I tried different current levels and the SM72445 always draws down the input voltage down to 11-12 volts - always missing the peak power point.
Where do you suggest I start looking?
Follow-on question, how does the SM72445 detect inductor saturation?
