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Is phase margin poor in this SMPS?

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T

treez

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Hello,
This Flyback power supply's vout rings at 1.2KHz when its starting up. However, the ringing ceases totally when it gets into regulation (30V =Vout). Also, there is no overshoot on start-up.
Would you say that this SMPS has poor phase margin, due to the ringing that occurs during start-up, whilst Vout is rising?

LTspice simulation and schematic attached, as well as waveform shot of vout, COMP pin (control input to PWM comparator), and the 30V line
 

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  • START UP WAVEFORMS.jpg
    START UP WAVEFORMS.jpg
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  • Flyback _TL431_FLSL_type2.pdf
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  • Flyback _TL431_FLSL_type2.txt
    8.3 KB · Views: 67

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