Switching mode power supply for Power Line Communication

Question

For a Powerline Communication device that uses the frequency band 42 to 89 kHz. I need to choose a power supply that will not add noise in the powerline and kill my communication band. There are two devices with certain current requirements; the first needs 1 A and the second needs 4 A.

I have looked at the available power supplies and tried adding a mains filter to suppress the EMC noise out of it (see figure below).

This will attenuate the communication signal as well, due to the Cx cap on the line (see figure below). So my best option at this point is to choose a better PSU to solve the problem.

I am looking for two designs or models of a switching mode power supply that will output 1 A or 3 A that has a high enough frequency that it harmonics will not interfere with the communication band between 42 to 89 kHz.

Answer 1

If you are using a SOC PLC device from STM you could maybe have a look at the ALTAIR04- 900 device as it was a recommended power supply in a datasheet for one of their devices. Page 56 of this document. They also have an example of the power supply input EMI filter- designed for the CENELEC A Band which is the frequency band your are interested in (page 57).

Answer 2

First, just assume the power line is noisy and design your protocol accordingly. A competent switching power supply by the device shouldn't make this substantially worse because you already assume there are switching power supplies hanging off the power line in various places.

Second, a line filter doesn't have to apply both to the power supply and the signal connection to the power line. This really should have been obvious. Put the line filter between the power line and whatever power supply you use, but tap the line for the purposes of the signal connection on the line side of the filter.