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I am working on designing a CCM Boost PFC rectifier circuit, supplying up to 2.8kW at 400Vdc nominal, while taking 230Vac, 50Hz controlled via negative feedback in the average current control mode. I am an Aerospace Engineer and very recently started working on an EE project so my questions might sound dumb but here goes:

  1. What does it mean when someone say loop bandwidth? Is it the bandwidth of T/(1+T), where T is the Open loop transfer function? Are the terms crossover frequency and bandwidth used interchangeably? What is the difference between 3dB frequency (I know its generally used for filters) and bandwidth?

  2. Why do we maintain a low bandwidth for the outer voltage loop compared to the inner current loop in said circuit? Is it so in all switching converters that use both loops? If so, what is the idea behind this?

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  • \$\begingroup\$ As for 2, think about what the boost would do if you gave it say 1 kHz bandwidth and requested 400 V out at all times while feeding it with rectified AC. \$\endgroup\$ – winny Dec 18 '18 at 12:07

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