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Design >> Analog Design >> Circuit causes feedback oscillation in power supply....
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Message started by Gibson486 on Aug 26^th, 2013, 8:23am

Title: Circuit causes feedback oscillation in power supply....
Post by Gibson486 on Aug 26^th, 2013, 8:23am

I have a circuit with a, IC darlington chip that is used to bring approx 1 Amp of current to an LED. It is controlled by a (4%?) PWM pulse that goes at about 800hz. Every time the circuit provides current to the LED, I get this ringing on my power supply. I tried numerous things such as using an inductor in series to try and suppress it, using big caps, to even using external regulators. I cannot seem to get rid of it. The only thing that really helped was the bypass caps (big and small) and putting a Schottky diode between the base and collector. However, I still get some ringing that effects other parts of my circuit. Any one else have any ideas I can try? Maybe I am going about this wrong?

Title: Re: Circuit causes feedback oscillation in power supply....
Post by aaron_do on Aug 26^th, 2013, 10:27pm

Hi,

you could try adding some series resistance to your supply cap at the IC. Or maybe you could use an LC filter on the supply to the IC. The corner frequency needs to be well below 800 Hz though.

Aaron