Power electronics are evolving at a rapid rate into automotive-grade applications with robust AEC-Q100 and AEC-Q101 qualifications. In analyzing several components, including ones recently announced at APEC, three major concurrent phases seem clear in automotive power design.
One phase is already well on the way. Mechanical control mechanisms, such as hydraulics, are being replaced with electronic control. A second phase is AI and autonomous driving. 5G will support point-to-point communication, enabling vehicles to communicate with each other and with traffic signals without the latency imposed by 4G’s need to communicate directly via the cloud.
Automotive Voltage Conversion
The requirements for these two phases span many voltages, with different current capacities, and must be available at locations all across the vehicles. To meet this wide array of needs, designers have developed voltage conversion devices that can be powered directly from the vehicle’s battery, or from DC sources derived from the battery.
Buck converters are highly efficient devices designed to provide a lower voltage power source from a higher voltage input, and are a common choice for automotive applications.
Texas Instrument’s LM5164 is designed to work from inputs ranging from 6.0 V to 100.0 V and to provide outputs ranging from 1.2 V to 50 V.
Murata's MYMGA1R86RELC2RA buck regulator. Image courtesy Murata.
In this competitive area of device development, Murata designed its highly efficient MYMGA1R86RELC2RA buck regulator for automotive applications, which features an input voltage range of 5.5V–14.4V and a programmable output of 0.7V–1.8V at up to 6 amps.
But, the most challenging phase, from the standpoint of the power engineer, is charging the battery of the all-electric vehicle.
Electric Vehicle Charging
According to a recent whitepaper by Infineon, a power source that can deliver 22kW can charge an electric vehicle (EV) to the point that it can travel 200 km in 120 minutes. That time can be reduced to about 16 minutes by providing 150 kW, and to about seven minutes with a 350 kW charge.
Seen below is a basic diagram for the charging system. The EV and the charger exchange information about the specifics of the battery, and the dc-dc converter supplies the correct voltage and current profile. Of course, lithium-ion batteries require very careful monitoring, so onboard battery management, as illustrated in the lower portion of the diagram, are mandatory.
EV charging diagram, courtesy Infineon.
Most users won’t be willing to wait 120 minutes for a charge at a “gas” station, but seven minutes is within the realm of toleration. However, the 350 kW required for that short delay is an enormous amount of electricity, bringing up the intertwined issues of efficiency and waste heat.
Automotive-Grade Silicon Carbide MOSFETs
The Inner Circuit of all members of the SCT3xxxxxHR Series. Image courtesy ROHM.
For a 650-volt device, the resistance between the gate and the source is as little as 17 milliohms, which means that here, only about 11 watts is wasted and turned into destructive heat.
SiC MOSFETs are a very competitive field, and aside from the devices mentioned at the end of the above article, there is also the NVHL080N120SC1 from ON Semiconductor, a 1200 V SC MOSFET that features a 80 mΩ minimal resistance between drain and source. As with all electronic devices, there are caveats galore, so power engineers will definitely have to do their homework before setting on a device for their particular application.
The 350kW Elephant in the Room
350 kilowatts times two hundred million EVs? That would require an unimaginable increase in the nation’s power grid capacity. And, a new grid of power distribution lines crisscrossing North America would be needed, not to mention the funding to install tens of thousands of charging stations.
The infrastructure problems inherent in conversion to EVs might well be more daunting then developing the vehicles themselves.
Have you noticed any other trends in automotive power applications? What's your take on the relationship of infrastructure to vehicle advancements? Share your knowledge in the comments below.
Featured image courtesy Infineon.