TIDM-1007: Current waveforms during soft-start

Manish,

We have read the doc for TIDM1007/TIDA-01604 about the soft-start you used before asking this post.

The user is trying to implement in the same method.

Our questions are:

1) Do you have any more zoom-in waveforms (PWM vs currents) at zero crossings, say light loads, middle loads? We are not very sure if Fig 13 (Figure 13. PWM Sequence With Soft Starting to Reduce Current Spike at Zero Crossing) is just a concept or a real implementation about the delays of Q2, Q3, Q4.

2) In Fig 13, is Q3 ON at the same time as Q2 ON? or Q3 ON after Q2 ON? Or this should be a tunable parameter?

3) After you implemented this soft-start, did you still see a little bit negative current right after the soft-start? or you completely suppressed the negative currents by this soft-start method? That is, we wonder by your implementation, the soft-start completely remove the spike/negative currents at zero crossings, or just reduce them on our TIDM-1007 board? Just want to know your experience.

Wayne Huang

Wayne,

1. None i can share, the image is real implementation the code is in the SDK for them to look at it

see

switch(pwm_SwState.enum_pwmSwState)
{
...


2. In my experiements it did not matter, they can modify the code and do the evaluation

3. Yes, at very light loads you still have. The soft start itself needs to be tuned. With the TID we wanted to show a method to solve this issue and the code is available to modify by the customer in the SDK for their application.

Wayne,

I will close this thread, please start a new thread if you have additional questions.

-Manish

Manish,

That’s OK.
thank you for your information.

Wayne