Average Current Control with Symmetrical Sawtooth or Peak and Valley Current Control

Abstract

Conductance control within SMPS (Switch Mode Power Supply) for space power systems is typically implemented relying on ACC (Average Current Control). Such technique is driven by a comparison between the electrical current and a sawtooth signal being either asymmetrical or symmetrical. An in-depth analysis of the associated dynamics has been published for the asymmetrical sawtooth case only. The present paper consists in the dynamic analysis of ACC using symmetrical sawtooth, resulting in a Laplace transform block diagram properly modelling the limited switching frequency effect. The bandwidth and phase margin of that closed-loop control technique are in particular investigated, highlighting that a symmetrical sawtooth allows to reach a bandwidth twice the one achievable with an asymmetrical sawtooth at given phase margin performance. In the same way that ACC with asymmetrical sawtooth is known to extend to classical PCC (Peak Current Control), the paper also shows that ACC with symmetrical sawtooth extends to an innovative PVCC (Peak and Valley Current Control) technique, using double compensation ramp, which increases the conductance control bandwidth capability to beyond half the switching frequency. Finally, time domain simulations are reported that prove to be consistent with the frequency domain theoretical predictions. Practical measurements have been performed on a breadboard as well and are reported in a separate paper.