Push–pull mode digital control for LLC series resonant dc-to-dc converters

This study presents the design and performance evaluation of the digital control adapted to an LLC series resonant dc-to-dc converter operating with wide input and load variations. The proposed control design correctly incorporates the wide-varying power stage dynamics and variable small-signal gain of a digitally controlled oscillator, thereby offering satisfactory converter performance for all the operational conditions. The proposed digital controller adopts the push-pull mode control scheme, which executes the control action two times in one switching period, to minimise the time delay and enhance the performance. Using a 150 W experimental converter, the performance of the proposed push-pull mode digital control is demonstrated in comparison with that of the conventional complementary mode digital control, which performs the control action only once in one switching period.