This is a followup of my previous question.

Boost IC = NCV3063

Vin = 8V

Vout = 23V

Iout(max) = 250mA - (Load is a constant current circuit which is enabled at 200Hz)


Circuit Schematic

Mentioned the points where I have probed

Waveforms (Same waveform, only varying the timescale) :




Why is there a dip in output current and increase in output ripple voltage at the marked areas?


And which waveform describes the right Peak to Peak ripple voltage measurement?

This :






  • 1
    \$\begingroup\$ I would not consider the transient excesses of switching in the load as part of the ripple voltage measurement but really, it's up to you. \$\endgroup\$
    – Andy aka
    Oct 29, 2019 at 8:05
  • \$\begingroup\$ What do you mean when you say "transient excesses" ? And please provide an answer in simple terms answering my questions, please \$\endgroup\$
    – user220456
    Oct 29, 2019 at 8:18

1 Answer 1


What do you mean when you say "transient excesses" ? And please provide an answer in simple terms answering my questions, please

Ripple voltage for a switching regulator circuit is usually (normally if you prefer) made under static load conditions and this means that you might only be interested in the part of the waveform shown in red below: -

enter image description here

In other words, the load effects are unchanging in the red area.

However, in purple is the change in output voltage when you change the load conditions. You apply this transient load change every 5 milli seconds but, it doesn't settle down to constant waveform and so this cannot (in my book) be regarded as a full picture of ripple voltage; you can see that the waveform is exponentially rising over the 1 milli second that you apply the load change but you don't apply the load change for long-enough of a period of time to let it settle.

This means you cannot accurately deduce the ripple voltage because the load change effect hasn't settled. If you allowed the load change to settle (maybe for 5 milliseconds) then switched back to the default loading scenario for 5 milliseconds you will likely be in a better position to deduce ripple voltage because, the waveforms will have stabilized.

Paramount is the effect of poor regulation (causing a long-term shift in the average value of the waveform following a transient load change) AND actual ripple superimposed on that average waveform change. You have to distinguish between the two and, at the moment, your waveform pictures (and testing method) don't allow that differentiation.

If, at the end of the day you tell me that you cannot change the load envelope (1 ms every 5 ms) then YOU have to make your mind up what is important to you. I can only advise what I feel is the right condition to determine ripple voltage and differentiate this from regulation quality effects.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.