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Need for automotive power feels the squeeze

08 Apr 2016  | Mark De Clercq

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These days, automobiles are evolving from being almost exclusively mechanical to becoming self-propelled embedded systems. Consequently, the amount of computing power inside the car is steadily rising, with some of the biggest improvements to processor horsepower moving into the dashboard and the infotainment systems it contains.

In addition to supporting virtual controls and dials, interactive maps and multimedia replay, the instrument cluster is becoming the home to the high-end multicore processors needed to implement the next generation of advanced driver assistance systems (ADAS). But with all that performance there comes a responsibility: to manage power effectively. And that is not easy.

The automotive power environment is harsh. Although a traditional power delivery system is designed to provide between 12V to 14.5V, transients can cause the voltage to surge to 100V or more and drop severely when the engine is started. It is vital that the power converters within the dashboard electronics handle both under-voltage and over-voltage conditions to prevent the software-controlled systems from needing to reboot.

Car computing power

Figure 1: The volume of computing power inside the car is steadily rising, with some of the biggest improvements to processor horsepower moving into the dashboard and the infotainment systems it has.

As well as protecting the delicate CMOS electronics from sudden swings in voltage and power drops, the power-management controllers need to ensure high efficiency. There is comparatively little airflow behind the dashboard. The top of the dashboard also receives intense sunlight whether moving or stationary, making it even harder to keep the area cool. And the electronics themselves generate a lot of heat.

As a result, it is vital that the power converters do not themselves generate additional heat, which means operating at high efficiency. For this reason, automotive designers are moving away from linear power converters, such as LDOs, towards more efficient switched-mode DC/DC topologies.

The move towards switching architectures can result in issues around electro-magnetic compatibility (EMC). There is insufficient space within the dashboard area to segregate electronics with shielding, and component placement options are often restricted. So smart design techniques are now being used to keep electromagnetic emissions under control through improved conversion algorithms and higher integration, which limits the number of high current paths on the PCB that often lead to significant emissions.

Then there is the issue of cost, which can potentially cause problems for designers who are faced with the need to deliver multiple voltages to the sophisticated multicore processors that now drive the infotainment systems. Traditional approaches to power management have relied on the use of multiple power converters to support each rail. All points made above demand a change in strategy, to use high-integration power management ICs that are able to support multiple rails, and the sudden changes in demand as the cores switch on and off as different functions in the infotainment software are activated.

The result is that the power management ICs are becoming as highly integrated as many of the devices they support, but with the added complexity of having to deal with the harsh electrical conditions of the automotive environment.

- Mark De Clercq

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