UCC3808-2: Fluctuating output issue

Correction:

RC pin waveforn :

Hi MIT, an expert will get back to you soon.——Teng

Hello Teng,

Yes please as i need to solve this issue quickly.

Hi MIT,

I am happy hear from you. I reviewed you output waveform. Do you find the wave resonance at 100HZ frequency. 

1, Do you check your bench is clearly?

2,can you sure no interference signal at the Q10? maybe you can check it.

3,Your FB waveform  oscillate up and down with 0 level. you have to find the cause of FB oscillate firstly. In additional, you can series one more cap( 100n)   with R84 in loop compensation as an integral.

Hi Bliss,

Thank you for your suggestions.

-->We are designing ultrasound therapy in which one crystal vibrates at 1 or 3 Mhz frequency,in amplification section schematic  it is connected at    connector J1.

-->We give PWM input of 100hz frequency to UCC3808.

1. I did not understand about the bench meaning please elaborate.

2. I will check the interference at Q10 and revert you back shortly.

3.FB waveform may be oscillating  as we implemented feedback from the amplification section.,If we need to design adjustable 40Vadj can we use feedback from 40Vadj NET directly instead of the feedback from amplification.

As you suggested to add one series cap(100n) with R84 ,is the connection shown below is correct?

I appreciate your time and attention into this.

Regards,

Mit

Hi Mit,

Do you means you inject 100Hz PWM signal to FB?  if so, the output should follow the FB frequency.

In additional, I can't see any circuit figure you said.

thanks

Hi Bliss,

Thank you for you prompt response.

I attached schematic pdf files in my first post attaching the same again.

In power supply schematic,i mentioned PWM applies here,at that point I injected 100hz pwm.6837.Power supply.pdf7658.Amplifier section.pdf

About the series capacitor i want to show you below image :

Hi Dear,

1,The series capacitor is correct.

2,I understand your PWM design means, but you have to keep the FB signal is stable waveform.

thanks

Dear Bliss,

Thank you for your inputs.

I am working on the FB signal to make it stable,Revert you after checking it.

Regards,

Mit