INN3677 Current Overload protection

2 posts / 0 new

Hi
I am driving a PCB with 14.5V which requires 30mA of power for 99% of the time. When requested to I activate a 12V 43W solenoid which at 14,5V is 63W. This is too much for the INN3677. To work around this problem I implement a fold back current scheme so the voltage drops to 11,5V at 3.3A. All I do is add a 56milli Ohm resistor in the IS leg going to the load and the voltage feedback resistor GND connection I take back to the load ground. The voltage drop across the resistor then increases the voltage to the FB pin reducing the output voltage.

Problem is the FWD drive dies causing the 47 Ohm resistor to burn up. I think the voltage on that pin is going to high. Would a 150V zener diode work or is there a more elegant way for solving this problem.

Best Regards

Dave Lea

Hi Dave,
Please share the schematic, layout, transformer design and construction for this design so that we can understand the problem properly.If you could also capture the primary drain voltage waveform and the FWD pin waveform at the moment of death then that would help to understand better.
PI-AP