Abstract: A four-switch buck-boost converter configured to couple to a source battery and a target battery includes an inductor and switches S1, S2, S3, and S4 connected so as to define (i) a buck mode in which the switch S3 is always ON, and the switches S1 and S2 control charging and discharging of the inductor, (ii) a boost mode in which the switch S1 is always ON, and the switches S3 and S4 control the charging and the discharging of the inductor, and (iii) a buck-boost mode in which all of the switches S1, S2, S3, and S4 control the charging and the discharging of the inductor. A controller operates the converter in the buck mode, the boost mode, and the buck-boost mode, when it turns the switch S1 ON at a beginning of a switching cycle, and turns the switch S4 ON at an end of the switching cycle.

Abstract: A system for controlling a charging current while transferring energy from a source battery to a target battery in an electric vehicle (EV) comprises a four-switch buck-boost converter configured to couple to the source battery and the target battery and configured to operate in (i) a buck mode, in which voltage Vg across the source battery is higher than voltage VEV across the target battery, (ii) a boost mode, in which the voltage Vg is lower than the voltage VEV, and (iii) a buck-boost mode, in which the buck-boost converter operates between the buck mode and the boost mode, and in which the voltages VEV and Vg differ less by a predetermined amount, and a controller configured to, when transitioning to or from the buck-boost mode, instantaneously adjust at least one a buck duty cycle dbuck or a boost duty cycle dboost according to a predefined value.