Sitting idle my pwm from my dsPIC works fine but when I try to drive my SMPS it looks like the attached image.
I dont want to suggest anything because I dont want to bias anything anyone says. I am also trying to learn as well.

Thank you!

 

We are going to need a schematic unless you want only guesses.

 

Looks like some stray inductance and capacitance in the circuit causing ringing.
Need a schematic if you want further responses.

 

Hello,

Next to the schematic, a picture of how the circuit is build might give more info.

Bertus

 

We are going to need a schematic unless you want only guesses.

True its just a half bridge converter sorry, but even the stray inductance and capacitance was great insight.

 

Scope probe ground wire too long.

 

Sitting idle my pwm from my dsPIC works fine but when I try to drive my SMPS it looks like the attached image.
I dont want to suggest anything because I dont want to bias anything anyone says. I am also trying to learn as well.

Thank you!

@Electronics117
In the schematic you posted, C3 is redundant and not needed. C1 & C2 block any DC current.

 

C3 is redundant and not needed

Agree. But … There is not enough information to know what type of power supply this is.
If C3 is only used to block DC then I agree.
C1 and C2 are often large Ele. Caps right after the rectifiers for a off line power supply. Then C3 is the cap used to resonate. Then we really don't know if this is a resonate power supply.

 

I'm not an expert but I'm guessing it's a stability issue due to a lack of phase compensation.
Here's a man who knows what he's talking about. He has a 3 video series on the basics of PWM converter design.

.

 

I'm not an expert but I'm guessing it's a stability issue due to a lack of phase compensation.
Here's a man who knows what he's talking about. He has a 3 video series on the basics of PWM converter design.

.

How and why would you apply phase compensation to a circuit that has no feedback? (That is, no feedback as far as we know, since we have not been provided a complete schematic.)

 

Sitting idle my pwm from my dsPIC works fine but when I try to drive my SMPS it looks like the attached image.
I dont want to suggest anything because I dont want to bias anything anyone says. I am also trying to learn as well.

Thank you!

@Electronics117
You posted colorful scope traces image, but so far as I can see, there is no way for us to know where your scope was connected for each trace. Since operation of a half-bridge drive is highly dependent on the gate drive signals, it would really be nice to have the rest of the schematic showing how the gates are driven, and how the dsPIC is connected to the gate drivers.