Hello,

Please let me know if this is the wrong place to post this.

I have a power supply design I need to test the filters on. In order to do this I need to inject noise into its 30 VDC input.

The noise will need to look something like CH1 here:



That's approximately 6V pk-pk of noise.

I expect I'll need a signal generator of some kind but I'm not sure how I would go about doing this. Any help would be greatly appreciated.

Thanks

 

hi M,
This is one option.
https://www.maximintegrated.com/en/app-notes/index.mvp/id/3469

There are lots of circuits which use a zener diode as a noise source, Google... zener diode white noise generator
E

 

Then to inject the noise you can use a large inductor in series with the 30V supply to keep the noise signal from being filtered by the source.

 

That is not going to be easy. By definition, an ideal voltage source would have zero impedance. How are you going to overcome the low impedance of the power supply? You will have to isolate the power source from its output filter circuit and since the filter circuit is integral to the power supply that will be very difficult to do.

Edit: What you need is a load on the power supply that draws random current at various frequencies.

 

Thanks for all the input but I couldn't figure out a way to make anything work in my application. This looks like it might be the closest I can get:



It's a 6V pk-pk sine wave offset by 30V by putting the signal in series with the DC source. I might be getting my hands on a function generator soon. Any thoughts on using a function generator and a DC supply in series like this?

Thanks

 

You can use a pulse transformer in series with the power supply. Next, you need a noise amplifier with the necessary low output impedance. From the amplifier output through the capacitor, the voltage is applied to the primary winding. The outer diameter of the ferrite toroid is 50 millimeters.
See

 

You can use a V > I converter as a load and just pipe the
noise into the input. This results in a noise current injected
into output. You use it in addition to normal load.

Regards, Dana.

 

What is the highest noise frequency?