Power Modules for Dual Active Bridge DC-DC Converters

Dual active bridge (DAB) converters have become a standard choice wherever a design needs galvanic isolation and power flow in both directions: DC fast chargers, battery energy storage, and solid-state transformer stages. The topology is simple on paper, but its efficiency, switching frequency, and thermal margin are set almost entirely by the power modules in the two bridges.

At HIITIO, we design and manufacture IGBT modules, SiC modules and gate drivers for these applications. This article walks through how a DAB loads its modules, what published reference designs show, and how to match a module and driver to your own converter.

How a DAB Converter Loads Its Power Modules

A DAB connects two full bridges through a high-frequency transformer and a series inductance, often supplied by the transformer’s leakage inductance. According to Texas Instruments’ application note on the topology, the direction and amount of power are set by the phase angle between the two bridges, and one bridge’s lagging current helps achieve zero-voltage turn-on (ZVS). That gives the modules three practical requirements:

• Both bridges are working bridges. Because power can reverse, the modules on each side must be rated for full current and loss, not only the load side.
• Soft switching is not guaranteed. A study in IEEE Transactions on Power Electronics shows that ZVS range can be lost at light load under phase-shift control, especially when one port runs at high voltage. Switching losses at light load therefore still matter.
• Modulation affects the stress. Extended, dual and triple phase-shift schemes can widen the ZVS range, but they change the RMS current and turn-off current the modules see.

Why SiC Modules Suit DAB Designs

SiC MOSFET modules are widely used in DAB stages for several reasons:

• Higher switching frequency. Lower switching loss allows higher frequency, which shrinks the transformer and inductor. ST’s 25 kW reference design cites passive-component size and weight reduction as a direct benefit of high-frequency SiC operation.
• No tail current. MOSFET turn-off is faster and cleaner than IGBT turn-off, which helps when ZVS is partially lost.
• Thermal headroom. Junction temperatures up to 175 °C, as listed on HIITIO’s SiC module pages, widen the design margin.

IGBT modules remain reasonable at lower frequencies and cost-sensitive high-power designs. For the broader device trade-offs, see HIITIO’s guide to SiC vs IGBT vs MOSFET for solid-state circuit breakers.

Table 1. Published DAB Designs and the Modules They Use

The spread is useful: 25 to 60 kW designs run at 100 kHz to shrink magnetics, while the 500 kW prototype runs at 20 kHz, where module current capability matters more than frequency.

Selecting the Module: What to Check

• Voltage class. ST’s design pairs an 800 V nominal bus with 1200 V modules. Higher bus voltages or stricter derating point toward 1700 V devices.
• Switching energy and output capacitance. Compare datasheet values at your bus voltage, current and gate resistance, not headline figures. Output capacitance also sets how much current is needed to achieve ZVS.
• Stray inductance and package. Low loop inductance limits voltage overshoot at fast di/dt. Package choice (62mm, Econo Dual) also decides how simple parallel and busbar layout will be.
• Conduction loss and current. Transformer RMS current is higher than average DC current and depends on modulation, so size the modules from simulation rather than P/V.
• Thermal path. Check thermal resistance, substrate material, maximum junction temperature and an integrated NTC for monitoring.
• Gate drive power. Per-channel gate power scales as gate charge × gate voltage swing × switching frequency, so it rises quickly at 100 kHz.

HIITIO SiC Modules for DAB Power Stages

HIITIO was founded in 2018 as a spin-off from Hecheng Electric and is based in Zhejiang, China. Our SiC module range spans 1200 V to 2300 V, and the half-bridge versions below are the ones most relevant to DAB legs.

Table 2. HIITIO 1200 V and 1700 V SiC Half-Bridge Modules

Values are taken from HIITIO’s SiC module listing; confirm test conditions in the datasheets.

Two details are worth noting. The HCS900FH120D3C1 pairs 2.0 mΩ RDS(on) with a Si₃N₄ AMB substrate, a 175 °C maximum junction temperature and an internal thermistor. The 62mm HCS360FH120A2C1 integrates a SiC diode and offers the same 175 °C rating in a widely used package.

HIITIO lists these Econo Dual SiC modules for OBC and charging-station AC/DC and DC/DC stages, including bidirectional designs, on its Charging Station Solution page. Energy storage designers can also review the Power Conversion System Solution page.

A DAB full bridge needs two half-bridge modules, so a single-phase DAB uses four across both sides. The product pages we reviewed do not publish a DAB-specific reference design, so validate switching energy and thermal data against the datasheet and with our engineers.

Gate Drive: Match the Driver to Your Frequency

HIITIO’s IGBT & SiC Driver range includes gate driver cores, plug-and-play drivers and application-specific drivers, with desaturation detection, soft shutdown and undervoltage lockout. The Gate Driver Cores (1 to 6 W per channel) and Plug-and-Play drivers are specified for applications up to 30 kHz. That fits lower-frequency, high-power DAB stages such as the 20 kHz class, but a 70 to 100 kHz SiC design needs a driver confirmed for that frequency and gate power. Our team can discuss application-specific driver options for those cases.

Build Your DAB Power Stage with HIITIO

Choosing a module for a DAB converter comes down to matching voltage class, switching loss, thermal path and gate drive to your frequency and power target. HIITIO supplies SiC modules in 62mm and Econo Dual packages, together with gate drivers developed in-house, and our engineers can review your bus voltage, power level, switching frequency and cooling method before you commit to a design. Browse the SiC module range, check the gate driver options, or contact the HIITIO team to request datasheets and a recommended module and driver pairing.

FAQ

Why use SiC instead of IGBT modules in a DAB converter?

SiC modules switch with lower loss and without tail current, which allows higher frequency and smaller magnetics. IGBT modules can still be a sound choice at lower frequencies where cost dominates.

What voltage class should I choose for an 800 V DAB?

ST’s 25 kW reference design uses 1200 V SiC modules with an 800 V nominal input. If your bus is higher or you need more margin, evaluate 1700 V devices such as the HCS400FH170A2C1.

How many power modules does a DAB need?

Each full bridge needs four switches. With half-bridge modules, that means two modules per bridge and four for a single-phase DAB, unless a full-bridge module is used.

Can a DAB lose soft switching?

Yes. Under phase-shift control, ZVS can be lost at light load or large voltage mismatch. Advanced modulation can extend the range, and module switching characteristics still matter in those conditions.

Which gate driver should I use with HIITIO SiC modules?

It depends on your switching frequency and gate power. HIITIO’s standard core and plug-and-play drivers are specified up to 30 kHz, so higher-frequency designs should be reviewed with our engineering team.