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Current compensator of PFC controller in CCM

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simbaliya

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Below is what I have read from book:

"There is a common issue in CCM shaping technique, i.e. when the line voltage increases, the line voltage sensor provides an increased sinusoidal reference for the feedforward loop. Since the response of feedback loop is much slow than the feedforward loop, both the line voltage and the line current increase, i.e. the line current is heading to wrong changing direction (with the line voltage increasing, the line current should decrease)."

As my understanding is that the line current should be propotional to the line voltage, therefore when line voltage increases, line current should also increase, this has contradictory with the case metioned above. Can someone tell me how to undertand the sentences above?
 

simbaliya said:
Below is what I have read from book:

"There is a common issue in CCM shaping technique, i.e. when the line voltage increases, the line voltage sensor provides an increased sinusoidal reference for the feedforward loop. Since the response of feedback loop is much slow than the feedforward loop, both the line voltage and the line current increase, i.e. the line current is heading to wrong changing direction (with the line voltage increasing, the line current should decrease)."

As my understanding is that the line current should be propotional to the line voltage, therefore when line voltage increases, line current should also increase, this has contradictory with the case metioned above. Can someone tell me how to undertand the sentences above?
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Yeah that's kind of a word salad... what I think they mean by that last phrase is that the line current should decrease as line voltage increases in a normal non PFC converter. So from the perspective of normal DC-DC converters (which regulate power over a wide bandwidth), a PFC converter operates at the line frequency.
 

For a resistive load (which is what you are trying to emulate) if the mains goes up briefly then the current to that load goes up briefly too. so it is a good thing if a PFC booster emulates this. It also adds to the stability of the mains network, if the input current went down instantaneously (constant power load) as the mains voltage went up - it would lead to instabilities in the mains network if a lot of these types of loads were connected, Regards, Orson Cart.
 

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