Online Efficiency Optimization Technique for Digitally Controlled Resonant DC/DC Converters

This paper proposes a digital online efficiency optimization technique for DC/DC Dual Half-Bridge Series Resonant Converters. The proposed technique implements an advanced modulation scheme which exploits the degrees of freedom inherently available in the converter modulation space in order to simultaneously regulate the output voltage and maintain the system in its maximum efficiency point. Furthermore, the proposed multivariable control technique robustly brings the converter back to maximum efficiency even in presence of abrupt load changes. The proposed efficiency optimization approach is first discussed theoretically, then via simulation and experimental tests. Experimental results on a 5 V, 1.2 A, 200 kHz series resonant converter prototype are in line with the theoretical predictions and confirm both the feasibility and the effectiveness of the approach. Experimental efficiency measurements indicate an efficiency improvement from eta = 30% to more than eta = 80% in light load conditions.