Implicit current DC-DC Digital Voltage-Mode Control

Abstract

Analog circuits have been dominating the switching power supplies control due to simplicity and low implementation cost. However, digital control presents important advantages to meet the increasingly stringent future processors power requirements. This study focuses in the fact that, sensing only a buck converter output voltage, a digital control can be built to implicitly implement a Current Mode Control (CMC), without sensing the inductor current while maintaining a fast response to load variations. A solution that consist on a Digital Linear-Quadratic Regulator with a Kalman Estimator (DLQRwKE) is compared with two new digital control laws: Digital Voltage-Mode Current Control (DVMCC), based on the last cycle output voltage change, and Digital Voltage-Mode Averaged Current Control (DVMACC) that also takes into account the previous duty-cycle. This last original control solution is proven to present state-of-art load and line transients and robust stability, even in the presence of changes in the operation conditions. The propose DVMACC is shown to be a promising alternative to current analog and digital control methods.