# Why is the capacitor filter in parallel with the load and the choke in series in a choke input filter?

What will happen if we interchange them?

In a capacitor filter, the capacitor discharges through the load, it was connected in parallel to load. From what I have concluded, if the capacitor is in series with the load then there will be a voltage drop across it, then the voltage at the load will be the voltage of the rectifier output minus the voltage of the capacitor, which will be no good as we don't need a reduced voltage.

In an LC filter (choke input filter) the inductor is in series with the rectifier output. Having it in series should affect the load voltage at load, too.

• Have you tried to simulate the two circuits to build your understanding? Commented Jan 25, 2022 at 20:27

## 1 Answer

From what I have concluded, if the capacitor is in series with the load then there will be a voltage drop across it, then the voltage at the load will be the voltage of the rectifier output minus the voltage of the capacitor, which will be no good as we don't need a reduced voltage.

Well yeah... but the point of a rectifier is to convert an AC signal to a DC signal, and putting a capacitor in series will not just cause a voltage drop, but will completely block any DC signals... which means it would no longer be a rectifier at all.

The typical LC filter when connected to a load works as an RLC low-pass filter to smooth the output of the rectifier. If you swap the capacitor and the inductor, you are now making a high-pass filter which is not what you want your rectifier to do.