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Instability on PWM Current Mode Controller

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Draytek

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Hi,

I am trying to design a boost converter using the UCC28 part and im getting some suboscillation on the inductor current and FET Gate. I tried to compensate the slope by following the guidelines from the datasheet but I cant get rid of it completely. The intention is to run this converter in continuous mode for at least 20% or 30% of the full load (80V@300mA).

I dont see yet how to get rid of the suboscillation or if Im doing something wrong. I am actually thinking in setting it up for voltage control instead, to make it unconditionally unstable.

I attached the schematic in LTSPICE. The converter has been laid out with discrete components. The output cap has been reduced in order to speed up the simulation.
 

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FvM

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As a first step, review your UC2843 model. Using a comparator with several 10 µs of response time in it looks like a joke.
 

Draytek

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Spot on mate!

I changed the comparator for a faster one and now is all clean and smooth.
 

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