The voltage drop across choke coil and capacitor C 2 is quite small. The high voltage is obtained at the output of Pi filter, the reason behind this high voltage output is that the entire input voltage appears across the input capacitor C 1. The residual AC ripples are filtered by inductor coil L and capacitor C 2. In pi-filters, the major filtering action is accomplished by the capacitor at input C 1. The Pi filter has the characteristics to generate a high output voltage at low current drains. Thus, Pi filter is considered more efficient. In the case of L-section filter, one inductor and capacitor were present so if some AC ripples say 1% is left after filtering that can be removed in Pi-filter. In this way, the efficiency of filtering increases multiple times. The residual AC components which are still present in filtered DC signal gets filtered when they pass through the inductor coil and through the capacitor connected parallel across the load. Therefore, most of the AC ripples get bypassed through the capacitor in input stage only. The capacitor provides a low impedance to AC ripples present in the output voltage and high resistance to DC voltage. The output from the rectifier is directly applied to the input capacitor. Thus it is a crucial need to remove these AC ripples to improve the performance of the device. The output voltage coming from rectifier also consist of AC components. The filters we have discussed in our previous articles are also efficient in removing AC ripples from the output voltage of rectifier, but Pi filter is more efficient in removing ripples as it consists of one more capacitor at the input side. The ultimate aim of a filter is to achieve ripple free DC voltage. Significance of Capacitor input filter or Pi filter (π- filter)
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