• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 39 subscribers
  • Views 438 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

PMP10783: Does this design works for low input voltage?

PMP10783: Measured Inductor current waveform is not proper

Francis_93
Prodigy 130 points

Part Number: PMP10783

Hi,

I have tested this design ( Rectifier section is not implemented ) and we found following observations.

 

 

These are the waveforms for input voltage of 150VDC & 250VDC. ( Rectifier section is not implemented ).

 

 

Blue color is the PWM at MOSFET gate.

Yellow color is output voltage.

And Pink color is the inductor current.

 

 

Observations

 

 

@ 150VDC input voltage : Duty cycle is fluctuating alternatively between two values  ( and inductor current also fluctuating alternatively )

/resized-image/__size/320x240/__key/communityserver-discussions-components-files/234/150V-input-_2D00_--120R--_2D002D00_00000.jpg

 

 

 

@ 250VDC input voltage : Duty cycle is fluctuating alternatively between two values  ( and inductor current also fluctuating alternatively ) . But in batches for some duration duty cycle is one value, after some time duty cycle is another value and this pattern is repeating and this repetition creates low frequency voltage ripple on the output voltage.

/resized-image/__size/320x240/__key/communityserver-discussions-components-files/234/250V-input-_2D00_--120R--_2D002D00_00000.jpg

 

When the inductor current is supposed to be zero it is not actually zero, some amount of ringing is happening.

 

Can you please check.

 

  • 0
    TI__Expert 6670 points

    Hi Anoop,

    I have asked the designer to take a look, give us a couple of days to get back to you.

    Thanks,

    Robert 

  • 0
    TI__Expert 4840 points

    Looks like there is some stability issue. The picture is quite small, I can't see the waveform clearly. Can you first check if there is any "skip cycle" happening? PMP10783 switches at 47kHz frequency, please make sure in your design you also see PWM pulses in 47kHz frequency. If not, there might be a noise coupling issue to the internal oscillator.

    There might be some component difference between your and PMP10783, you might want to adjust compensation values (R, C at pin 1). By reducing R and increasing C, you should be able to slow the response and allow the system to become more stable.