Introduction to filter Work Principle I

There are several filter circuits used in power filter. Today we'll introduce the work principle of CLC П type filter

a.When input the positive pulse , the C1 is charged first. The charging current is ic1, it charged to the peak voltage of the pulse Vi rapidly, At the same time, there is a linear increase in the inductor L, and magnetic energy is stored in the L. With the increase of current, more and more magnetic energy is stored. The capacitor C2 is charged by inductance L. The charging current is basically equal to the voltage on the C1. The current IRL in the load RL is also supplied by the input pulse.

b.When input positive pulse disappears, the current of load RL is supplied by two channels, one is the current provided by the C2 discharge ic2,, the other is converted from the magnetic energy stored by the inductor to the electric energy, and the ic1. is provided after series with the voltage on the C1. The The current in the load RL is equal to the sum of the discharge current of two capacitors, that is, IL=-(ic2ic1)

c. For DC, the C1 and C2, in the CLC filter are equivalent to open circuit, while the inductance is equal to zero and short circuit, so the DC component can pass through the inductance L. smoothly

d. For AC: the capacitor has a large capacity, which is equivalent to short circuit, and the inductance has a large resistance to various sine waves, so the AC component can not pass, or just pass a little.

 Advantages: high output DC voltage, the highest peak voltage of rectangular wave, suitable for large load current, small output voltage pulsation.

Weakness: used in power supply without regulator voltage circuit, load capacity is poor.

CLC П filter is commonly used in pulse amplitude switching power supply. The larger the capacitance and inductance, the better the filtering effect.