Half Wave Rectifier Circuits

Siddhanth

Joined Nov 18, 2007
1
what i wanted to know was when we use a capacitor as a filter in our rectifier circuit and we get the ripples in the voltage, why is the capacitor connected in parallel and not in series? what would be the effect of connecting the capacitor in series with the diode? any information would be appreciated.

Papabravo

Joined Feb 24, 2006
20,600
The capacitor in parallel provides a low impedance path to ground for AC signals. The higher the frequency of the AC siganl the lower the impedance. Conversely the capacitor in parallel provides a high impedance path to ground for DC signals.

If you placed the capacitor in series with the diode, then it would block the DC, and pass the high frequency AC. In fact this method is used to couple the stages of an amplifier when this is the precise behavior which is desired.

cheddy

Joined Oct 19, 2007
87
When a capacitor is connected in parallel to the rectifier unit, with no resistance the capacitor leads it will charge in close to an instant with the AC voltage as it is increasing. By the time the voltage is at the peak the capacitor is fully charged. As the voltage the AC source is providing begins to drop the AC voltage is less than the capacitor voltage so the capacitor begins to discharge and supplying the difference between the instantaneous AC voltage with it's own charge. Hopefully you're using a capacitor that can hold a large charge like 1000uF so that the AC voltage will be increasing once again to charge the capacitor up again before it runs out of charge.

cheddy

Joined Oct 19, 2007
87
The capacitor is not in series because you should know that when a capacitor is fully charged is wont pass any current, it will act like a really big resistor. So by the time the first AC cycle has passed the capacitor is full and will begin blocking current from getting to the rest of the circuit. By putting the capacitor in parallel, once the capacitor is full and stops allowing current to pass through it, it will just take the path of least resistance, around it.

surbhi

Joined Mar 26, 2008
5
actually, capacitive inductance, i.e. Xc= 1/2*pie*f*C
so, whenever, frequency increases Xc decreases, that occurs in A.C. signal. so capacitor allows the flow of A.C. into it. and in rectifier ckt. we don,t want any A.C. part in output. so A.C. signal should be grounded. thats why capacitor in filters connected in parallel to sink the A.C signal.