Capacitor Filter Working Principle


A half-wave rectifier with a capacitor-input filter is shown in Below Figure. The filter is simply a capacitor connected from the rectifier output to ground. RL represents the equivalent resistance of a load. We will use the half-wave rectifier to illustrate the basic principle and then expand the concept to full-wave rectification.

During the positive first quarter-cycle of the input, the diode is forward-biased, allowing the capacitor to charge to within 0.7 V of the input peak, as illustrated in Figure (a). When the input begins to decrease below its peak, as shown in part (b), the capacitor retains its charge and the diode becomes reverse-biased because the cathode is more positive than the anode. During the remaining part of the cycle, the capacitor can discharge only through the load resistance at a rate determined by the RLC time constant, which is normally long compared to the period of the input. The larger the time constant, the less the capacitor will discharge. During the first quarter of the next cycle, as illustrated in part (c), the diode will again become forward-biased when the input voltage exceeds the capacitor voltage by approximately 0.7 V.

Capacitor Filter

(a) Initial charging of the capacitor (diode is forward-biased) happens only once when power is turned on.

Capacitor Filter Charging

(b) The capacitor discharges through RL after peak of positive alternation when the diode is reverse-biased. This discharging occurs during the portion of the input voltage indicated by the solid dark blue curve.

Capacitor Filter Working Principle

(c) The capacitor charges back to peak of input when the diode becomes forward-biased. This charging occurs  during the portion of the input voltage indicated by the solid dark blue curve.

Fig : Operation of a half-wave rectifier with a capacitor-input filter. The current indicates charging or discharging of the capacitor.


Engineering Tutorial Keywords:

  • capacitor filter working
  • working principal of capacitor
  • working of capacitor filter
  • explain the working of capacitor filter
  • capacitor filter workinf
  • principal or capacitor input fillter
  • operating principle of filter in electronics
  • how work capacitive filter
  • how is capacitor filtering work
  • Half-Wave Rectifier diode 0 7

No comments

You May Also Like :

Comparison of MOSFET and BJT

Comparison of MOSFET and BJT

When we are studying about Power semiconductor devices, we will start from Diode then Bipolar Junction Transistor and then MOSFET and so on… It is ...