Which topology is better for Bi-directional DC-DC converter? CLLC or DAB?

TBhatia

CLLC

DAB

CLLC and DAB are two popular topologies in the industry for fast charging, on board chargers and other power applications. Both them have their own pros and cons:

From the topology point of view, both have a full bridge in primary side and a full bridge on the secondary side. The difference is that CLLC has one extra resonant capacitor. However, it doesn’t influence the system cost and volume for 10-20kW system power level.

The control scheme for these converters are different. CLLC usually uses frequency modulation control to adjust the output voltage. While the switching frequency of DAB is fixed, we can get different output voltage by adjusting the duty cycle between primary and secondary side bridge. In order to get a wide voltage gain range, CLLC is hard to optimize with the transformer turns ratio, Lm (magnetic inductance) of transformer and resonant inductance Lr. DAB is easier to realize by using single or multiple phase shift control.

Power loss and efficiency. For CLLC, zero turn on can be realized in all working conditions. For most part of the voltage range, CLLC MOSFETs experience lower turn-off current and therefore lower turn-off loss. In case of DAB, it has high turn off current, so the switching loss is higher for most part of the voltage range. Therefore, DAB will have more power loss and lower efficiency for the same voltage range and power rating.

Depending on the use case and specific application a detailed calculation and analysis can be performed to understand which topology performs better and is more cost-effective.