Buck (or boost) converter with very fast output current transitions and low ripple voltage

摘要

In a multiphase buck converter running at precise duty cycles which have an inverse integer relationship with the number of phases and a precise synchronized phase relationship, it is possible to have zero output ripple. If the output inductors are replaced with coupled inductors having nominally the same inductance, and the second windings of the inductors are wired in a loop with correct phasing, under steady state conditions the voltage drop around the loop will be zero. A small voltage injected into the loop can cause very fast transitions in current in the loop, and those currents will be reflected to the first windings of the inductors as a very rapid transition in the output current. This converter has no dc voltage control capability, so it is preferably used with a pre-regulation stage as the control of the dc output voltage. Dynamic voltage control is very fast, as the current into the output capacitor can change very rapidly.