Capacitor in DC circuits

[djc]

Hi,

A capacitor allows only AC current through it. It may be a silly question, but can somebody please tell me why to use capacitor in bridge rectifier circuit. How capacitor operates in rectifier circuits.

 

[adi0803199]

Check out this website:

http://en.wikipedia.org/wiki/Diode_bridge

,Check out the Output Smoothing section.Here they have explained the use of capacitor to smoothen the ripple produced at the output.

 

[djc]

Means in rectifier circuit how capacitor allows to pass a DC current through it after rectification through the diode.

 

[kappa_am]

As you know the capacitor is utilized to reduce voltage ripple ( just reduce). so the voltage over the capacitor is not pure DC; it has some ripple. how this ripple is generated?
when we attach a load to capacitor, it uses of stored energy in capacitor (draw a current from capacitor) when the output voltage of rectifier is smaller than capacitor voltage (suppose capacitor and rectifier detached). this causes to voltage of capacitor drop.
rectifier provide load current and charging current needed to charge capacitor back to it primary voltage, when output voltage of rectifier is higher than capacitor voltage.

 

[godfreyl]

Means in rectifier circuit how capacitor allows to pass a DC current through it after rectification through the diode.

In rectifier circuit, capacitor does not pass DC current. AC current flows through capacitor in rectifier circuit.

 

[adi0803199]

Capacitor has a rise time and a fall time which is dependent on the value of the load as well as the value of the capacitance that is connected as the load(load resistance).The aim of a rectifier is to convert ac voltage into dc voltage.The presence of capacitance assuming fairly high capacitance value, is used when the ac signal having a negative slope (i.e. for θ>90^. and θ<180^. assuming the ac signal to be sinωt,where θ=ωt).Here the capacitor delays the effect of the change in the slope of the signal at the output because of the presence of discharge time associated with it thereby making the output to remain nearly the same value till the signal reaches the value of θ=180^..Now during the period from ωt=180^. to ωt=270^.,the capacitor has to charge and here again the presence of this capacitor delays the process thereby trying to maintain the voltage level at approximately the same level.
Hope this clarifies your doubt.