Pfc circuit design working

[Rujul Desai]

hi,

what is the meaning of PFC circuit?
what is the exactly meaning of PFC circuit and valley Fill circuit?


Thanks

 

[treez]

Valley fill is a form of pfc circuit...its just two caps and 3 diodes......you end up with a bit better pfc than a bridge followed by a smoothing cap with a valley fill..
PFC is just about making the current and voltage in phase with each other......or mostly, current sinusoidal and in phase with the voltage......preferably no harmonics in the current for unity power factor...unity power factor means less power is wasted in the electrical supply system.

Current is usually made in phase with voltage by having a controlled boost converter, with its current controlled to be in phase with the voltage.

 

[biswaIITH]

PFC means power factor correction using different techniques....u need to make the input voltage and input current(i.e. from the grid) in phase with minimum or almost zero current distortion(ofcrs there are some regulations)As far as power electronics is concerned, u can improve the power factor by using different dc-dc converters(buck,buck-boost,boost)...These days more research is going on integrated converters wherein two same or two different converters are integrated with a common shared switch...
If u r using basic dc-dc converters or above mentioned integrated converters ,u always need to operate atleast one of them(always the first one) in DCM(discontinuous conduction mode)....

U can choose to operate a basic dc-dc converter in CCM...Each method has its own advantages and disadvantages...when dc-dc converter is operated in DCM,it has the inherent capability to improve the power factor at the cost of peak semiconductor current and hence losses due to it ...when you operate a converter in CCM ,it looses its inherent capability.In that case u have to use different control algorithm for improving the power factor.....