How to isolate the main circuit from the noise of the EPS auxiliary power supply?

The auxiliary power supply (such as flyback or reverse flyback) within the EPS is itself a source of switching noise, and it is necessary to prevent it from interfering with the main power circuit and control circuit. Isolation measures include:

1. Power isolation: Use an isolated DC-DC module to power the auxiliary power supply, cutting off the path of noise conduction through the input power line.

2. Space and layout isolation: Place the auxiliary power supply module in a relatively independent area on the PCB, away from the main power circuit and sensitive sampling circuits, separated by ground lines or isolation strips.

3. Filter isolation: Place filters at both the input and output terminals of the auxiliary power supply, using a π-type filter on the input side and an LC filter on the output side. For example, a CLC filter or integrated filter module can be used at the output terminal.

4. Grounding isolation: The secondary "cold ground" of the auxiliary power supply is connected to the motherboard "hot ground" through a single point, and the connection point is selected at a clean ground reference point to avoid noise ground current contamination of the main ground.