Are you still sensing current at the transformer CT? The datasheet shows it at the buck input. Do you actually see CS rise to 0.6V? If not then that means the controller is doing its job as described. If you want that upper threshold to trip when the output shorts, then the inductance in that path (including the buck inductor and the transformer leakage) must be low. And the bandwidth of the CS signal must be high.following up on this, I went a different route and changed the topology to cascaded current fed push-pull converter, which automatically solved secondary side rectifier ringing (no inductor there). The controller is LM5041 configured for current mode operation. While it's running nicely, I can't get it to trip the second comparator threshold of 600mv and go in hiccup when the output is shorted. The first threshold of 500mv is reached and the buck stage pulse terminated rendering the whole thing a current source. It then dissipates tons of watts in the buck switches. I can't think of any other easy solution except disabling the controller once the mosfets temp exceeds some level...
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