Three-Leg Active Bridge-Based Bidirectional Resonant Converter Using Hybrid Si/SiC Switches

This article proposes a bidirectional resonant converter that uses a three-leg active bridge and hybrid Si/SiC switches. The use of a three-leg active bridge on the secondary side of the transformer transfers twice as much power compared with the use of a single active bridge; one of the three legs is shared, which reduces the number of active power devices in the development process. The phase-shift modulation has been adopted for both power flow directions, which enables zero-voltage switching turn-
on
for all the switches. On the secondary side, the shared leg only requires the use of two SiC
mosfet
s, because these particular switches undergo high conduction loss and high turn-
off
loss during both forward and backward operations. This trait reduces the implementation cost of the circuit further. The primary-side windings of the transformer are connected in series and each secondary-side winding has wound in the opposite direction. The resulting symmetric architecture of the dual transformer connected to a three-leg active bridge and the corresponding pulsewidth modulation (PWM) naturally balance the currents flowing through the middle leg and right leg on the secondary side. A 1-kW rated prototype that converts 150–200 V input to a 400 V output is designed and tested to validate the concept for cost-effective battery charging and discharging.