Hi all,
I’m updating an existing half-bridge design that uses the LM5033 in order to implement the CS pin (which was previously unused and grounded). I’m using the CS pin short-circuit protection, and I’ve set the CS pin so that it trips when current through a sense resistor is ~3.85A. Our design is for 160V minimum Vin, and up to 200W out at 27V out; our normal operating conditions should not draw more than 1.4A rms input current.
The problem I’m having is that while short-circuit protection works great, the downside is that current limit also trips during turn-on, when the output capacitors of the converter charge up. (Our output capacitance is 5x 6.8uF, but we spec up to 250uF external capacitance as well.) I see the CS current limit cycle at least 20 times before Vout slowly charges up enough not to trip current limit; then Vout rises as expected.
Does anyone know how to implement current limit on this controller, while preventing it from also tripping during turn-on? Is my current limit set too low? My concern is that if I set current limit higher, my half-bridge will become unbalanced during short-circuit before the current limit kicks in.
Any help or feedback is appreciated!