Excellent power supply low-pass filter circuit

The filter can greatly attenuate noise components higher than the power supply frequency, while allowing frequency components near the power supply frequency to pass through
. It especially has a strong suppression effect on spike pulses.
    Commonly used low-pass filter parameters are shown in Table 15-1. In the table, Cl and Cz can use paper capacitors, and C3 can use
high-frequency capacitors such as mica and porcelain. A good AC filter should have a noise suppression greater than 60dB ( excellent product) or 40dB (qualified product)
    in the frequency range of 20kHz-30MHz . For purified power supply, power supply filters
are installed at the input and output ends of the power circuit . A power supply low-pass filter circuit     with excellent performance is shown in Figure 15-6. The filter component parameters are selected as follows: Li, Lz - several to tens of millihenries; L3, L4 - several hundred microhenries to several millihenries; Ci～C4-0. 047～lvF;     Rv - nominal voltage UlmA is the power supply 1.3 to 1.5 times the rated voltage, and the current capacity can be selected from 1 to 3kA.