Bidirectional DC/AC topologies


Recently, more and more power conversion applications, such as PV micro-inverters, battery storage systems, on-board EV chargers, etc., require isolated DC/AC power converters. The markets for these applications are rapidly growing. The conventional two-stage topology solutions have simple control, higher efficiency, and lower cost. However, they have low efficiency, high cost, low density, and complicated control.

This invention is proposed to combine both the benefits of the two-stage solutions and the single-stage solutions to significantly improve the performance and reduce the cost. In addition, the modular extended version of this topology solution dramatically reduces the cost for the systems containing multiple DC sources.

Technology description

Researchers at The University of Texas at Austin propose a topology solution which combines the pulse width modulator (PWM) converter and the resonant converter. The cost of this solution is as low as the state-of-the-art single-stage solution. However, the efficiency can be even higher than the single-stage solution. Due to the simple and reliable zero voltage switching (ZVS) control and synchronous rectification (SR) control, the control and sensing complexity is even lower than the state-of-the-art two-stage solution. Thus, the frequency can be up to MHz level, which dramatically improves the power density.

The bidirectional power flow capability makes this solution suitable for many bidirectional power conversion systems. In addition, the modular extended version of this solution which uses a novel parallel structure significantly reduces the cost for the systems containing multiple DC sources. A few of the features include:

  • Combination of PWM converter and resonant converter
  • High frequency, high efficiency, high density, and low cost
  • Simple and reliable control
  • Bidirectional power flow capability
  • Modular extension capability


  • High efficiency: The efficiency can be up to 98%.
  • High density: The frequency can be easily up to MHz level with soft-switching. The power density is dramatically improved.
  • Low cost: Since the volume and mass are significantly reduced, the cost is also reduced.
  • Simple and reliable control and sensing: There are no requirements for complicated sensing and control for MHz zero voltage switching (ZVS) and synchronous rectification (SR) control. The controller is quite simple and reliable.
  • Bidirectional power flow: the proposed solution can easily achieve bidirectional power flow. This feature makes this topology to be compatible with the bidirectional power conversion systems.
  • Modular extension capability: this proposed solution can be extended to a modular extended version. This modular version of the proposed DC/AC solution significantly reduces the cost of the systems which contain multiple DC sources. The efficiency and density are further improved.



Figure 1. Proposed isolated DC/AC topology solution.


Figure 2. Topology with minimized switch count for the proposed solution with unfolding bridge.


Figure 3. Topology with minimized switch count for the proposed solution with AC switches.