Subharmonic Behavior In Current Mode Control (Part 2): The Causes And Cures At Low Duty Cycles

Focus:

Part 1 discussed the subharmonic behavior that occurs in power converters operating under current-mode control at high duty cycles and how this problem can be remedied with slope compensation. At low duty cycles we often do not expect to see subharmonic behavior. So when it arises we may take the step of designing in slope compensation after the fact, which often resolves the problem, but not always. So now what do we do? This second and final part of the article answers that question. The causes of subharmonic behavior at low duty cycles are explained along with techniques to counteract them. This discussion culminates in the description of circuits that generate a precise analog of the inductor current, which is then combined with slope compensation to eliminate the subharmonic behavior.

What you’ll learn:

• How to understand the causes of subharmonic behavior at sub 50% duty cycles in current-mode controlled power converters
• How to understand the causes of subharmonic behavior at sub 50% duty cycles in current-mode controlled power converters

View the Source

Author & Publication:

Ernie Wittenbreder, Technical Witts, Flagstaff, Ariz., How2Power Today, Jul 15 2016

This article summary appears
in the HOW2POWER Design Guide.

The Design Guide offers
organized access to
hundreds of articles
on dozens of power conversion
and power management topics.

The Design Guide search results
include exclusive summaries
and accurate "how to" analysis
to help you make faster,
more informed decisions.

Search
for more articles