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Electronics => Beginners => Topic started by: Metatronic_Mods on March 08, 2018, 02:54:39 am

Title: How could I simulate noise injected on voltage rails caused by switching loads?
Post by: Metatronic_Mods on March 08, 2018, 02:54:39 am
On a system I'm working on there are numerous subsystems which share common VDC+ VDC- and GND buses. A few of the subsystems are injecting noise onto the supply buses. They all have a bunch of LEDs being driven by PWM at audio rate (WHY??) and they aren't very well bypassed internally -which can present as a problem for some of the other subsystems (sensors etc.). So my plan is to add passive inline T-filters between the noisy systems and the supply buses.

I'd like to be able to simulate a few different designs (different loads & prominent frequencies) but I'm not sure whether I'm on the right track with my model or not.
Starting with just one of the subsystems being powered, I was able to measure the DC average current draw, as well as the transient current draw.
Am I right to think that I could model the subsystems loading effect as an equivalent load resistance in parallel with an alternating current source?

Example: Vbus = +12V,   DC load current = ~200mA  Transient current = 50mA @ 1000Hz
Power supply is to the left, the subsystem being powered is to the right, and the boxed area contains the filter I want to add.