Line filters

[tomchr]

I could simulate it. I have LTSPICE, what do I use as source noise? Is it just an AC sweep?

If you want to look at the filter transfer function (attenuation), an AC sim would be useful. I'd run one for differential mode and one for common mode signals. See posts #29 and #30.

~Tom

 

[avincenty]

I hope I did it correctly. There does not seem to be a huge difference between them except for the one with 4 inductors that shows a spike on the Ground Loop simulation.

 

[Wavebourn]

I have noise being generated by my HPNA network. I am in the process of building solid state preamp with a toroidal transformer and regulators.

Which one of these will perform better?

None of them. I would use an isolation transformer in your case.

 

[avincenty]

None of them. I would use an isolation transformer in your case.

You mean the toroidal transformer in the power supply? The one I have has a shield connection as well.

 

[Wavebourn]

You mean the toroidal transformer in the power supply? The one I have has a shield connection as well.

No, I mean to power through an isolation transformer that single thingy that creates noise on the ground lop for the rest of equipment.

 

[avincenty]

Oh I see. And oops, I meant to say that I have a Powerline Ehternet network, not HPNA (phoneline). The only other item that gives me problems is the microwave oven, it is used just a few times a day so it is OK.

 

[Wavebourn]

Oh I see. And oops, I meant to say that I have a Powerline Ehternet network, not HPNA (phoneline). The only other item that gives me problems is the microwave oven, it is used just a few times a day so it is OK.

I don't see how a microwave can be connected to the ground loop.

 

[avincenty]

I don't know anything about microwaves, if it is not coming back from the microwave then it must be one of the many things plugged in the vicinity that picks the interference up and sends it back. My shop is the the garage far from the kitchen. I dont hear the noise in my audio devices, but I do see it in the oscilloscope. I realized I had noise coming in when I built a curve tracer.

 

[Wavebourn]

You may see any garbage in the mains, and as soon as it provide needed power why you should be bothered? I remember in Back to the Future movie the car run on garbage, including cola cans and banana peels. But it run quite well!

Back to the futurs, folks! 🙂

 

[tomchr]

I hope I did it correctly. There does not seem to be a huge difference between them except for the one with 4 inductors that shows a spike on the Ground Loop simulation.

There's a huge difference between the Corcom and the rest at high frequency. The Corcom has much higher attenuation for ground loop currents at 100 MHz.

As I noted in previous posts, I suspect the resonance peak is tamed quite a bit in the real filter.

~Tom

 

[TheGimp]

Why not go to the manufacturers web site and look at the data sheets?

Power Entry Modules

The biggest issue with line filters is knowing what you are trying to filter out.

I've got 15KHz-25KHz EMI from the switch mode ballast in florescent lights in the den. There are no practical filters that will quell it.

On the other hand, if you are dealing with 100KHz and above, then the line filters may be a solution.