48V for car electrification

From an engineering point of view, the intention is to streamline the electric/electronic architecture, which will optimize the power network and decrease fuel consumption. This has a positive effect on greenhouse emissions and will comply with future government regulations. It also facilitates the real start-up of the car electrification.

The 48V battery system would be packed in a similar way to a higher voltage battery used in hybrid electric vehicle (HEV). Basically, there are elementary cells staggered in clusters to reach the required voltage.

Interfaced with an inverter driving an electrical motor up to 10kW, the current energy is not sufficient to insure the traction of the car. Therefore, the overall weight for powertrain is lighter than for HEV and it could be combined with the internal combustion engine (ICE) during the start-up phase to significantly reduce fuel consumption by bringing an additional torque to the engine.

The cost of such system would remain reasonable versus a full hybrid system; it requires an inverter stage with a controller in addition to a DC/DC converter to recharge the usual 12V battery.
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The compressor for the heating, ventilating and air conditioning (HVAC) systems would significantly improve with an electrically driven system. Current vehicles may have insufficient electrical power available with the low voltage battery used. The secondary 48V energy network will easily address the compression drive question.

In addition, the electrical motor for the electric power steering (EPS) would also benefit by extending the power range especially for premium cars with even more electronic loads.

If you consider power ICs, MOSFET transistor technology is a good fit for the inverter. The breakdown voltage capability is determined by the system partitioning, likely between 80 to 100V, and the RdsOn level is tuned to mitigate the power dissipated. Therefore, tight collaboration between our technologist team, system engineers and our customers is important to optimize the technology specification in order to fulfill the application cost-efficiency. The inverter delivers the 3-phase alternative current (AC) directly connected to the electrical motor. Thanks to a dedicated 32-bit MCU, it can perform a motor control command supporting various algorithms and software libraries. More information is available here.
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The cost of the battery is an important consideration in the HEV market. Many analyst reports agree the price of Li-ion technology battery should fall dramatically by 2020, by a factor of three to four. The battery is not a commodity product and must address a few technical challenges. The main ones to highlight include properly handling the chemistry because of the safety risk in case of damage, management of the charge/discharge cycles and sustainable lifetime operating. Electronic components are available today to monitor through these physical measures and to work out the challenges. Check out my previous blog: “What makes a battery sensor an Xtrinsic solution is a car?”

The car electrification path is on-going with multiple directions that are possible. The 48V falls in the mild hybrid segment which will represent more than 50% share of the HEV/plug-in HEV and EV market by 2020 according to Strategy Analytics study. One of the reasons is that high voltage isolation is not required with ##IMAGE_4_C##
These upcoming events at Paris Motor Show or SAE Convergence 2012 in Detroit will give us the opportunity to uncover a bit more of the intention of industry stakeholders. We look forward to news that will be shared on this topic!

We welcome your thoughts about embedded solutions for a second battery network.