PFC stage
Totem pole or interleaved boost, usually with SiC devices switching between 65 and 140 kHz.
The magnetic: Boost inductor, sized for ripple current and for saturation at the peak of the line cycle, not at the average.
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Magnetics for automotive and EV power conversion
On board chargers, DC-DC converters and traction auxiliaries. The magnetics in a vehicle are designed twice over: once for the operating point, and once for the vibration profile, the coolant temperature and the thermal cycling the car will actually see over fifteen years.
Where the magnetics sit
The stages, and what goes in each one.
Isolated DC-DC in the charger
LLC for unidirectional charging, CLLC when the vehicle has to export power back.
The magnetic: Main transformer plus resonant inductor. In both topologies the leakage inductance is a circuit element, so it is a design target and it gets measured.
High voltage to low voltage DC-DC
400 V or 800 V down to the 12 V or 48 V rail, phase shift full bridge or resonant.
The magnetic: Planar transformer where height is the constraint, plus an output choke carrying heavy DC bias.
EMI filtering
Conducted emissions to the limit line the vehicle programme sets.
The magnetic: Common mode chokes on the DC and AC lines, sized from a measured scan rather than from a catalog impedance curve.
What decides it
What actually drives the design here.
400 V and 800 V
An 800 V architecture changes creepage and clearance, the insulation system and the partial discharge behaviour. It is not the same part with a different turns ratio.
Vibration and shock
Potting in resin or in an aluminium housing, with the winding supported so that nothing moves against the core across the vehicle life.
Thermal cycling
The failure mode is rarely a single hot day. It is the expansion mismatch between copper, core and potting, cycled tens of thousands of times.
Coolant, not air
Many of these parts sit on a cold plate at 65 degrees C. The thermal path to that plate is part of the mechanical design, not an afterthought.
The shape of it
Standards, range and typical parts.
- Qualification path
- Designed toward AEC-Q200, with the material set and construction chosen for it
- Supply chain
- Built to the traceability an IATF 16949 customer has to demonstrate
- Temperature
- Minus 40 to plus 125 degrees C, depending on materials and insulation class
- Typical parts
- OBC transformers, resonant inductors, PFC boost chokes, DC-DC planar magnetics, EMI chokes
Questions
Automotive and EV, the usual questions.
Can you design an automotive magnetic to AEC-Q200?
We design toward the AEC-Q200 qualification path: the core material, the wire insulation system, the potting and the construction are chosen so the part can go through that testing. The qualification itself is run on the finished part, and we will tell you at proposal stage which requirements drive the design and which ones cost you volume or height.
Do you design for 800 V architectures?
Yes. Moving from 400 V to 800 V mostly changes the insulation system rather than the magnetic circuit. Creepage and clearance grow, the interlayer insulation has to hold off more, and partial discharge becomes something to design against rather than to check at the end. We tell you which of those is setting your size.
Can you hit a leakage inductance target for an LLC or CLLC charger?
Yes, and in a resonant charger it is not optional: the leakage is the resonant inductor, or part of it. Interleaving, winding order and the bobbin all move it. We give you the target value in the first proposal, and the measured value on the report that ships with the prototype.
What do you need from us to start?
A schematic and a switching waveform beat a finished drawing. Input and output voltage, current, switching frequency, the topology, the space you have and the temperature you can live with. If you have a CSV of the waveform, send that too.
How long does an automotive prototype take?
We aim to send an engineering answer with a first design proposal inside 24 hours, and 4 to 8 weeks from an agreed design to a prototype, when the raw materials are in stock. There is no minimum order quantity, so the first one can genuinely be one.
Start here
Send us your automotive and EV spec.
A schematic and a waveform are enough to start. You get a first design proposal with estimated losses, the inductances, the dimensions and the expected hotspot temperature, before you have spent anything.