DAB

10kW Dual Active Bridge DC-DC Converter

Hardware files for a high-power, high-frequency DC-DC converter PCB, developed as a prototype module for a modular 500kW off-grid EV DC fast charger. The board implements a Dual Active Bridge (DAB) topology with a planar transformer, isolated gate drivers and sensing, and on-board water/air cooling provisions for the power stage.

This board is a single prototype module. Multiple modules are intended to be run in parallel and/or series to scale up to the full 500kW system.

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Key specifications

Board design notes

• All components are placed on the top side only for simpler, cheaper assembly; the transformer sits in the middle and physically supports the board (and the cooling plate, when fitted).
• Six copper layers at 70µm are used (instead of the reference design's 4 layers) to reduce conduction losses at higher secondary currents.
• HV secondary components are rated to 1700V to handle voltage spikes at the 1000V output target, with 1.7x derating.
• DC blocking capacitors are 2280-package, 1700V rated, double-stacked to reach the required capacitance. A future revision should move to the 3640 package, which has more capacitance per area but does not fit the current footprint.
• Contactors are not on the PCB — HV switching is handled externally via XT30 connectors, allowing higher-voltage contactors to be selected independently of the board.
• Isolated 5V and gate-drive supplies are derived on-board; see "Known issues" below for a wiring correction needed for the secondary-side isolated 5V rail.
• Designed and manufactured through JLCPCB (6-layer, double-thick copper, 2mm FR4).

Design rule summary

These rules were applied during layout and should be followed in any revision:

• High current: ~1 via per amp for stitching/heat spreading, no 90° corner traces, 70µm copper minimum, 6-layer stack-up. Trace rise kept to ≤10°C above ambient at 30A (verified with KiCad's trace-width calculator).
• High frequency: Ferrite-core planar transformer, short/direct high-frequency traces, minimized loop areas to limit EMI and parasitic inductance.
• High voltage: Clearance/creepage per IPC-2221 and IEC-60664 (3.5mm creepage at 1000V), 2x voltage derating where practical, Plastik 70 conformal coating (>85kV/mm dielectric strength) on the assembled board.
• Thermal: Copper-filled vias, water-cooled or finned aluminum heatsinks on SiCFETs and transformer core.

## Known issues / errata (first prototype build)

These were found during assembly/bring-up of the first board and are not yet fixed on this design unless noted — see schematics for full details:

• eFuse (TPS26400): Pins 3 and 5 were swapped in the footprint, preventing power-up. Fixed on the physical board with bodge wires; needs a schematic/footprint fix in the next revision.
• controlCARD connector: The standard KiCad/Digikey footprint for TI's connector has reversed pin numbering vs. TI's own controlCARD. A separate flip-adapter PCB is required as a workaround (included in this repo). The adapter should be ordered in 1mm board thickness, not 1.7mm, to avoid breaking the socket pins on connector insertion.
• Isolated PSU current limit (Rlim): Original 1k current-limit resistor caused overcurrent-protection faults on startup due to 5V rail capacitance. Change to 270R.
• Primary-side sensing pinout: DS modulator interface pins to the controlCARD were routed to pins that don't support DS modulators; rerouted with magnet wire on the prototype and needs correcting in the footprint/routing.
• Secondary isolated 5V supply: Originally derived from the "top" isolated supply of H2, whose ground floats to 1000V half the switching cycle. Must be re-derived from the "bottom" isolated supply of H2 instead.
• Cooling clearance: Backside DC capacitors interfere with the aluminum cooling plate; stack capacitors on the top side instead. The transformer cutout also needs enlarging — it's currently a tight fit.

⚠️ Due to the eFuse/pinout bodges above, this specific assembled prototype should only be tested at low voltage (LV), not at its rated HV, until a corrected revision is built.

Repository contents

• Schematics and PCB layout (KiCad)
• Fabrication outputs (Gerbers / stencil) as ordered from JLCPCB
• controlCARD adapter PCB (flips connector pinout, 90° mount)
• Renders of the assembled board and cooling solutions

Background

This board was developed as part of an internship thesis evaluating the feasibility of in-house production of a 500kW off-grid EV DC fast charger, based on and enhanced from a Texas Instruments DAB reference design. Full design rationale, simulation results (LTspice/PLECS), and test results are documented in the accompanying thesis — this README covers only the PCB/hardware side.