Bode PLOT - What things make this?

[ljy4468]

Hi all

I made voltage regulator, and simulated it using stb analysis.

and bode plot is as below.

There is peak curve at phase graph and because of that, phase margin is below 0 degree. circuit oscillates.

What things make peak curve at phase graph?

I don't know how to fix that. please advise.

Thanks.

 

[biff44]

What makes it happen? Trying to divide by zero.

 

[sutapanaki]

looks like you have a nice resonance. Probably no one can tell you why it is happening without looking at the circuit. But you can reduce your DC loop gain to bring this dip below 0dB line and then it will be stable.

 

[LvW]

looks like you have a nice resonance. Probably no one can tell you why it is happening without looking at the circuit. But you can reduce your DC loop gain to bring this dip below 0dB line and then it will be stable.

Yes, there is a parasitic resonance around 1 MHz which can be observed also on the gain plot. Try to improve the frequency compensation.