Adaptive hybrid primary/secondary-side digital control for series resonant DC-DC converters in 48V VR applications

In this paper, a current sensorless adaptive secondary-side control is proposed for the series resonant converter, making it a good candidate for MHz 48 VRs. By means of varying AC equivalent resistance, the output voltage regulation is achieved by controlling the duty cycle of the synchronous MOSFET. A current sensorless adaptive digital control is proposed to control the current-type synchronous MOSFETs, which automatically compensates the delay caused by the current-sensor circuit and the gate driver, and also eliminates the current sensor in the power path. A hybrid control strategy is introduced to overcome the efficiency degradation caused by the secondary-side control.