LAUSR

In order to meet the full load range operation requirement for a semi-dual active bridge (semi-DAB) dc–dc converter working as a battery charger, a multimode control strategy was presented. Under heavy load, it works with single phase-shifted control. Under light load, it works with pulsewidth modulation (PWM) and variable switching frequency. Under very light load conditions, it works with PWM and constant switching frequency mode. Light load conversion efficiency can be improved significantly by using the proposed multimode control strategy. Detailed loss breakdown is analyzed and compared with different switching frequencies under light load conditions. The implementation of the control strategy was given and a seamless transition can be obtained among three operating modes according to the load power. The effectiveness of the control strategy was validated by the experimental results of a 1.6-kW hardware prototype.