Which Control Topology to Choose? Does it Matter?


Control topologies: voltage-mode, current-mode, average current-mode, hysteretic, D-CAP, DCS-Control, etc.

Well, yes and no.  When choosing a power supply for any system, the choices for just the control topology may seem endless: voltage-mode, current-mode, average current-mode, hysteretic, D-CAPTM, DCS-ControlTM to name a few.  On top of choosing which control topology, then you need to determine which features are required.  Do I need adjustable soft start?  How about a power good output?  Is thermal shutdown required or do I need an indication of an over-temperature event?  So many questions and so little time!

As power supply control technologies advance, hopefully the first question can be removed for the equation.  It seems as though every new power supply device uses a slightly improved version of the previous device’s control method.  Just the other day, TI released a D-CAP3TM device, the TPS53513, which improves upon the very successful D-CAP2TM topology.  And just a month earlier, the DCS-Control topology brought IQ to a whole new level at 360 nA in the TPS62740.

A key thing to note about these developments is that both D-CAP3 and DCS-Control are not your ‘textbook’ control topologies.  Voltage-mode control has been around forever, it seems, and has been pretty much optimized.  There’s simply no performance left to squeeze out of it.  While it’s still useful for some specific applications, hysteretic-based topologies (like those mentioned here) are very quickly improving to outperform voltage-mode control in all areas.  Just think of how far D-CAP and DCS-Control have come in a just a few short years.  They weren’t even around before that!

So, does your choice of control topology matter?  Of course it does!  Each topology has its drawbacks, but with more and more hysteretic-based converters around these days, and their corresponding greater and greater performance, it’s getting more and more difficult to pick a topology that won’t work for your application.  That should leave more time available for optimizing the feature set of the power supply for your application, while removing the sometimes worrying choice of power supply topology.

Want to read more?  Check out my control topology article here.