Elimination of switching losses in the single active bridge over a wide voltage and load range at constant frequency

Switching losses occur in the single active bridge (SAB) with phase-shift control when it operates over a large voltage and load range at constant frequency. At high output current, the SAB operates in continuous conduction mode (CCM) where the anti-parallel diode of the switch conducts prior to the switch turning on, thus enabling ZVS. However at low output current, zero current switching (ZCS) turn-off occurs in discontinuous conduction mode (DCM) and ZVS turn-on is lost. With the dual current pulse control proposed in this paper where a non-zero turn-off current is maintained during DCM, switching losses can be mostly eliminated across large output current range with a simple auxiliary circuit, hence enabling large voltage and load variations at higher efficiency. Efficiency increase of up to 12 % at light-load can be achieved without sacrificing its full-load efficiency. The predicted results are validated with a 3 kW SAB hardware prototype.