LC filter has obvious suppression effect on noise ripple. Choosing appropriate inductance and capacitance to form a filter circuit according to the frequency of ripple to be removed can generally reduce ripple well. However, in this case it is necessary to consider the sampling point of the feedback comparison voltage.
The sampling point is selected before the LC filter (Pa), and the output voltage will decrease. Because any inductor has a DC resistance, when there is current output, there will be a voltage drop in the inductor, resulting in a decrease in the output voltage of the supply. And the voltage drop varies with the output current.
After the OUTPUT of LED drive power supply, it is connected with LDO filter
This is the most effective way to reduce ripple and noise. The output voltage is constant and the original feedback system does not need to be changed. However, it is also the method with the highest cost and power consumption. Any LDO has one indicator: a noise suppression ratio.
After LDO, the ripple is generally less than 10mV.

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