I had a device that was failing with the conducted emissions test of the FCC part 15b.
It was failing in the 800khz-1.2MHz range. I do not have a clock source of that frequency on my board, nor was I able to trace where it is coming from.
My question is this what can I add to my power supply circuit to reduce noise in the 1MHz region.
I have attached my power supply schematic below. It is a 3.3 V regulator with VIN being a 6volt wall wart.
Just place C6 100nF (X2 type) before D1. Or add new one (better)
difflvl said:
Hi,
I had a device that was failing with the conducted emissions test of the FCC part 15b.
It was failing in the 800khz-1.2MHz range. I do not have a clock source of that frequency on my board, nor was I able to trace where it is coming from.
My question is this what can I add to my power supply circuit to reduce noise in the 1MHz region.
I have attached my power supply schematic below. It is a 3.3 V regulator with VIN being a 6volt wall wart.
Just place C6 100nF (X2 type) before D1. Or add new one (better)
difflvl said:
Hi,
I had a device that was failing with the conducted emissions test of the FCC part 15b.
It was failing in the 800khz-1.2MHz range. I do not have a clock source of that frequency on my board, nor was I able to trace where it is coming from.
My question is this what can I add to my power supply circuit to reduce noise in the 1MHz region.
I have attached my power supply schematic below. It is a 3.3 V regulator with VIN being a 6volt wall wart.
6 100nf caps will help with the 1mhz frequency range? I thought those values are good for higher frequencies. At the lab I tried adding more 100nfs and it didn't really do anything.
Hi, reading the hole topic it seems like the wall wart power supply is causing problems. I might be wrong here. Are you are testing with the wall wart power supply to get a compliance certificate for the complete system. Perhaps you can try an other power supply if the one you are using is a switching power supply. It might be market CE and all the rest but most of them are not. I'm currently evaluating power supplies from china for a product. Some of them even fail on the input voltage requirement of 85 volt...
Hi, reading the hole topic it seems like the wall wart power supply is causing problems. I might be wrong here. Are you are testing with the wall wart power supply to get a compliance certificate for the complete system. Perhaps you can try an other power supply if the one you are using is a switching power supply. It might be market CE and all the rest but most of them are not. I'm currently evaluating power supplies from china for a product. Some of them even fail on the input voltage requirement of 85 volt...
difflvl, at the moment I have tried three different brands. But I can't test radiated emission. I don't have the equipment to do this. Here my customer is a bit upset about the price he has to pay to get a certificate...
Anyway, a good working and very low cost power supply can be found on: cnhitong.com