Estimator-Based Step-Load Transient Improvements in a Digitally Controlled Synchronous Buck Converter

The paper proposes a digital estimator based control method in point-of-load (PoL) DC-DC converters to achieve fast response times and low voltage deviation under frequent load transients. Using the proposed method, a fast digital controller can be designed even in the presence of significant delays in the control loop. The method is particularly effective at high switching frequencies when the delays can be comparable to or even greater than the switching period. Moreover, an estimator based response can significantly reduce the output voltage deviation for load transients, which can further reduce the size of the output filter capacitor. The approach is experimentally verified on a GaN-based 1 MHz synchronous buck converter prototype. Experimental results are shown for load transients from 1 A to 7 A and back at
$\boldsymbol{V}_{o}$
= 30 V output voltage and
$\boldsymbol{V}_{g}$
= 80 V input voltage, with output voltage deviation less than 1.5 V and response times in the range of 5 - 6
$\mu\mathrm{s}$
.