I'm testing a power supply prototype, that takes 110v ac input, 24V,10A output, using topswitch.
Initially the clamp resistor was getting hot(more than 115c), after reducing the resitance and increasing its wattage this stopped and the temperature stayed at 65c. But at 5A load, the damping resistor got burnt after 5 min . I increased its wattage also. It is not burning out now. But TOP261 shuts down, when i monitored its drain current, the leading edge spike starts after 3 mins, and it starts growing till topswitch shutsdown.
The measured clamp voltage and VOR are matching with the PIExpert s/w.
I measured the primary leakage inductance as 133uh and primary capacitance as110pf. The transformer spec says 116uh.
I have also attached the drain current and voltage waveform at 5A load.
Kindly suggest , how to proceed