48V systems: a good intersection between efficiency and cost in mild hybrids

Those involved in the automotive market are constantly hearing about the 48V system. Why 48V? 48V systems are being adopted in power-train electrification because they:

  • Are less expensive, as they don’t require large batteries.
  • Do not require a high level of isolation and safety, as the voltage is below 60V.
  • Offer improved efficiency (lesser wiring losses), lower weight (due to less copper) and improved mileage for high-power loads, as the wiring harnesses can be reduced.

This discussion of standardizing 48V systems is focused around mild hybrid vehicles. First off, let me start by defining a hybrid. A hybrid vehicle uses different forms of energy in the car to deliver propulsion: it uses the internal combustion engine, the electric motor and the battery. Most often you will see gasoline-driven hybrids that reuse energy to charge batteries in situations where energy would otherwise go wasted in a pure internal combustion engine. A mild hybrid is simply a hybrid that uses electric power in addition to engine propulsion in situations where that extra boost of energy is warranted.

So the key question is the industry trend to focus on mild hybrids for 48V systems. First off, there is a big regulatory push for stricter carbon dioxide (CO2) emission standards on several continents; one requirement being lower emission standards. Going to pure electric vehicles (EVs) would require larger batteries, where costs are still prohibitively high. On the other hand, a 48V battery stack is a much lower-cost solution, which also works in conjunction with traditional internal combustion engines.

A lot of power generation from batteries can be augmented in situations such as accelerating, driving high-power loads as well as recuperating from the electric motors back to the batteries, all of which result in lower CO2 emissions. Several high-power loads that were previously belt-driven systems – pumps for power steering, anti-lock brake systems, compressors for air conditioners, water pumps, etc. – can now be driven by auxiliary inverters (electric power) at a very high efficiency and can thus play a significant role in lowering CO2 emissions. Bottom line: with these functionalities, the goal of reaching CO2 emission targets with mild hybrids gets closer to cleaner energy.

Given these advantages, it is clear that the industry is coming closer toward developing the standards for the 48V systems. Such standards would further trigger the volumes of the rapidly growing mild hybrid space, combining high efficiency from 48V systems and lower cost (along with economy of scale) relative to pure EVs all around the world.

Texas Instruments plays a vital role in developing solutions for 48V systems. One of them is a compact, fast and highly integrated 120V high-voltage gate driver for auxiliary inverter systems that enables a high system-level efficiency, robust handling due to negative voltage capability at the switch node pin and lower bill of materials (BOM) cost.

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