5 kW Isolated Bidirectional DC-DC Converter Reference Design

The 5 kW Isolated Bidirectional DC-DC Converter reference design from Toshiba shows how to improve a power supply design's efficiency using SiC MOSFETs. The design uses the dual active bridge (DAB) method, one of the most popular topologies for such high-power converters. The DAB topology has full bridges on both sides, allowing the direction and amount of power to be controlled by adjusting the phase difference between the left and right bridge circuits.  This highly versatile reference design forms a starting point for developing and prototyping high-power conversion applications, such as electric vehicle charging stations and inverters in solar power generators. 

• Bidirectional high-power conversion by DAB method
• High power conversion efficiency using SiC MOSFETs on the high voltage side
• Total solution including low voltage side MOSFET (TK49N65W5) and gate driver (TLP5214A)

Specifications

• High Voltage Side :  DC 732 V to 768 V
• Low Voltage Side :  DC 396 V to 404 V
• Rated Power :  5.0 kW

The diagram  shows a system that combines two reference designs available from Toshiba. The “5 kW Isolated Bidirectional DC-DC Converter” reference design (introduced in the following article) is matched with a high-efficiency “3-phase AC 400 V Input PFC Converter” reference design. The two reference designs can be used together for quick and easy system development and are both available from Toshiba. 

3-Phase AC 400 V Input PFC Converter Reference Design

Inverters for photovoltaic power generation (hereinafter referred to as PV inverters) require highly efficient bi-directional DC-DC converters with low loss. They are used to adjust the DC voltage level supplied by the solar panels and transfer it to the inverter and storage battery charging circuit.

PV inverters are used to convert DC voltages generated by PV panels into commercial AC voltages for use in houses and factories, or to feed them to the power system (Grid) (reverse power flow). However, the power generation capacity of solar panels depends on the time of day and the weather, and it is impossible for the PV panel to supply enough power at night or during cloudy weather.  By adding a battery that stores surplus power during favorable weather, we can build a system that can provide a stable supply of electricity whenever it’s needed.

Bi-directional DC-DC converters are indispensable in providing power from storage batteries to the power system, and vice versa, providing power from the power system to the storage battery.  Highly efficient and bidirectional operation uses isolated DC-DC converters to create a PV-inverter system that utilizes limited power with low-loss performance.