Electric Vehicle (EV) – Resonant Power Converter Topologies for DC-DC power converter stage

DC-DC converter is an important stage of any EV charger. Resonant converters are most preferred DC-DC converter in EV chargers segment because of in-built features like below other than the isolation

• High-frequency operation is possible due to soft-switching
• High efficiency due to soft-switching
• High power density due to soft-switching
• Less size inform of magnetics size due to high-frequency

The block diagrammatic representation of any resonant power converter is shown below. It consist of

1. High-frequency DC-AC converter (Inverter)
2. Resonant circuit (L/LC/LCL)
3. High-frequency transformer which provides isolation
4. High-frequency AC-DC converter (Rectifier)

The most common resonant converter topologies have been using in the on-board or off-board chargers are:

1. Phase-shift full bridge (PSFB) resonant converter
2. LLC resonant converter
3. Dual active bridge (DAB) resonant converter

Fig. PSFB resonant converter

Fig. LLC resonant converter

Fig. DAB resonant converter

Based on application requirement, these power modules can be used with slight changes in the standard topology. The most common application requirements are:

• Bi-directional capability
• Output voltage range
• Load range
• ZVS range
• Rated power
• Efficiency
• Output current capability