DC-DC Buck converter for EV vehicles: MOSFET or IGBT?

[alsabri_badr7]

Motor Specifications:

• Rated power: 50 kW
• Rated voltage: 200V DC
• Rated current: 250A

Battery Specifications:

• Nominal voltage: 400V DC
• Capacity: 50 kWh

Design Requirements of the DC-DC Converter

• Input Voltage Range: Specify the range (300V - 450V DC).
• Output Voltage and Current: Detail the required output voltage (200V DC) and current (250A).
• Efficiency and Ripple Voltage: State the efficiency (>95%) and ripple voltage (<2% of output voltage) requirements.

For these voltage value and efficiency; should I use IGBT or MOSFET? Because I have read that IGBT is excellent for > 100 V (high voltages) but it is not that much in efficiency. I have done the calculations needed and it is attached below:

 

[dick_freebird]

Look first to your planned switching frequency and the losses
of each. IGBT has a minimum Vds (the in-built PNP Vbe@load)
while FETs do not (just Ron*Iload). You probably won't chop
an IBGT faster than 50-100kHz). FETs can go faster, but should
you? Is iron mass the big deal or is it the copper?

At the bottom of it all there is a large "economics element" in
a real life architecture and component selection. The "right answer"
may not be, often is not the "best technical answer".

You have to boil down those requirements to the device(s) and
value choices responsible, draw a box around the viable options
for each, and downselect until either you find options for each
that work, or change some values (like, maybe fSW at 25kHz is
what it takes for IGBT switching losses to overtake MOSFETs as
the switch, because for some reason you can't do a 250A MOSFET
switch rack and there's an IGBT module good to go).

 

[BradtheRad]

Since power levels are huge, interleaving is a way to reduce stress on components. The wires can be thinner because current is reduced. The inductors can have reduced ratings in Henry value and saturation limit. You use less iron and less copper.

With 4 stages you may not need a smoothing capacitor. Simulation depicts 4 inductors merging to one 250A load. Ripple is surprisingly narrow.

With 4 interleaved clocks it's easy to arrange each duty cycle to be 50%. However a more sophisticated controller is needed if you wish to give each converter its own varying duty cycle.

 

[D.A.(Tony)Stewart]

EV's often use dual bi-directional Cuk converters to restore acceleration power during braking.
In 2015 a paper also used parallel IGBT and FET in parallel with 50 us early turn-off of IGBT's on the motor side.

Also it is important to include battery load regulation specs or ESR range. Full acceleration may drop a fully charged battery to 0.7 p.u.
Some vehicles use a hybrid HM & PM 32-pole rotor design 9-phase stator winding formed from concentrated coils with 3 phase drivers.

You may want to review your system design specs and include all in your question and search more on the state-of-the-art on any search engine and if on IEEE, look for ResearchGate site link which often has it.

 

[FvM]

If you are asking for EV state-of-the-art, the answer is simple. Recent vehicles are using SiCMOS.

 

[D.A.(Tony)Stewart]

SiC substrates are now used for both cheaper IGBT's and faster more efficient FETs. and switch off IGBT's early to avoid tail currents.

While FETs continue to become more cost effective, there is still room to evaluate costs of share the load with IGBT +FET in dual half bridges.

C3M0021120D WOLFSPEED, INC SICFET N-CH 1200V 100A $32ea (per 100)​

​

IKD15N60RATMA1 Infineon Technologies AG IGBT TRENCH 600V 100A $4 ea (per 100)​

Differences with IGBTs | What are SiC-MOSFETs? – SiC-MOSFET Features | TechWeb

The previous time, we explained two important points relating to driving of

techweb.rohm.com

more design info

Download Technical Documents | Technical Information Site to Learn the ABCs of Design TechWeb

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[cupoftea]

Are you sure of OP?....i never heard of an EV that uses a 50kW converter to supply the motor from the batt...they all supply the motor direct from the batt.
You get 50kW chargers...but they arent on board the car. And they deffo dont supply the motor direct.

 

[FvM]

Are you sure of OP?....i never heard of an EV that uses a 50kW converter to supply the motor from the batt...they all supply the motor direct from the batt.

Surely the motor isn't directly supplied from the battery. It's a synchronous AC motor in modern EV, the inverter is however directly supplied.

 

[cupoftea]

Thanks, sorry, thats what i meant...when i said "motor", i meant "drive and motor"....i am admittedly a bit over-casual with my terminology sometimes.

The point being, though, that you wouldnt likely get a dcdc converter in between a 50kw motor/drive and a battery.

 

[FvM]

There's simply no use of it, the motor inverter can be and is designed to match battery voltage.