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Tool/software:
Hi,
I am Having issue with the controller that the output is going to some protection but as soon as i turn off AC input, after i second like that the output comes before discharging to zero. I am getting Square wave kind of pulses in NTC pin. What might be the reasons.
It would be very helpful if you help me solve it.
Thanking You.
Hi Cs power,
Thank you for reaching out.
Please probe if there is any output overvoltage is occuring. Page 12 of the datasheet shows potential reasons for shutdown. For OVP I would recommend checking AUX winding instead of the Vs pin.
Regards,
Harish
Thank you for the response
At AUX waveform I observed that there is a negative spike of 70 V. The transformer turns are Primary 18 ,secondary 5, aux 4 turns. and the output is 24V . Does this effect the VS pin because after some time the Vs pin impedance become 106 Ohms and the R1 of divider of Vs is 110K ohms.
Hi cs power,
Definitely if the spike on Vs pin is above the abs max rating then it will damage the IC. Since OVP is also being triggered, I would suspect if the transformer has excessive leakage potentially leading to this effect.
Regards,
Harish