Digital control law using a novel load current estimator principle for improved transient response

Abstract

A method for the early detection of load transients using a current estimator for VR applications is presented. This technique combined with a new charge-balanced digital control law can improve the dynamic response to fast load transients. The key advantage of this new approach is the early detection of load transients which is independent of ADC sampling, where most existing solutions incorporate relatively expensive, complex and energy consuming high-speed ADCs. The presented method significantly reduces the inherent delay associated with fixed sampling detection in the control loop. The load current estimation during transient is critical for improved transient performance and allows the possibility of using a charge-balanced control law. Unlike existing algorithms, the presented control law is capable of implementing non-zero load lines required for VRMs. A full description of this control law is detailed. The current estimator technique and the charge-balanced digital control law are critically assessed using Matlab/Simulink. The resulting transient behaviour gives a significant improvement over conventional control schemes.