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Green hybrid cars drive change in IC landscape

Posted: 28 Aug 2008 ?? ?Print Version ?Bookmark and Share

Keywords:hybrid electric vehicle? HEV? electric car? automotive electronics?

The continuing price hike in gasoline was only the tip of the iceberg. For years automotive manufacturers have been working on drive technologies intended to reduce the dependency on oil and at improving emissions. That initiative has received a jolt but the question remains as to how these drive technologies will be adopted and how they will change the semiconductor landscape within vehicles.

Hybrid electric vehicles (HEVs) and all-electric cars continue to receive much of the attention. Indeed, market researchers expect the sales figures for HEVs and electric cars to climb steeply. Their forecasts predict unit figures tripling or quadruplicating within the next four to five years, from a number of less than 1 million units sold in 2008.

These alternative drives pose challenges to the semiconductor industry since the vehicles incorporate fundamentally different ways to generate, transform and store energy.

Depending on the technical approach of these drives, some electronic building blocks might become obsolete while other components and functional units will be required.

"Electrification will happen in the next few years and it will change the semiconductor landscape," said Marc Osajda, global automotive strategy manager for Freescale Semiconductor Inc.

Nevertheless, in terms of market-share, all-electric cars will play a minor role, the experts agree. Sales of HEVs of many different flavors will far outweigh those of electric cars, at least up until 2015. And sales of all the HEV types combined will make up less than 5 percent of the overall vehicle market, the experts predict.

Gartner, for instance, expects the hybrid penetration rate to stay below 3 percent of all vehicles until 2012. Nevertheless, the growth rate is impressive: during the same period, production will rise from about 650,000 units in 2008 to about 2.3 million units in 2012.

And for the semiconductor industry, the 'green' trend bodes well in automotive, as it does in many other sectors. "We view this trend with great pleasure," said Kurt Sievers, VP of strategy in NXP's automotive and identification business unit. "Anything that aims at reducing CO2 is beneficial for the electronics industry."

This statement applies particularly to HEVs. "The semiconductor content of these vehicles is significantly higher than in conventionally driven cars," said Nils Mnzer, product manager hybrid modules for Infineon Technologies AG.

From the perspective of semiconductor vendors, the common core element of an HEV as well as an all-electric car is the "electrified drive train". However, it is necessary differentiate between a diverse set of approaches and degrees of 'hybridness'.

Driving hybrid
The simplest form of hybrid drive is the 'micro hybrid'. Implemented in cars in volume production today such as BMW's 1 series, micro hybrids are equipped with a 'stop-start' system that automatically cuts off the internal combustion engine when the car stops for more than a few seconds and re-starts it when the driver kicks the clutch. A starter generator recovers kinetic energy lost during braking. In contrast to other hybrid approaches, the generator is used only to recharge the battery.

In 'mild' hybrid vehicles an electric motor is used to support the internal combustion engine during acceleration phases and to improve the overall efficiency. Mild hybrids are characterized by an electric motor power ranging somewhere between 6- and 14kW per metric ton of car weight. Vehicles with 'full' hybrid drive feature a similar architecture but with a stronger electric engine (more than 20kW per metric ton) can drive solely driven by the electric engine, albeit only over limited distances.

The term 'plug-in hybrid' refers to an approach that aims to expand the usage of electric energy in the vehicle and thus further reducing the fuel consumption. A plug-in hybrid offers the possibility to charge its batteries not only via the car's built-in generator but also via the power grid. Plug-in hybrid vehicles are characterized by a higher battery capacity and thus extended driving range in electric mode.

HEV power requirement
Mild and full hybrids as well as all-electric cars store the electric energy in batteries typically working at several hundred volts. With important factors such as capacity, weight and price, these batteries are a key component of alternative drives. Unlike standard cars with low-voltage supply, they require significant additional electronic content, in particular power components.

Between low-voltage generator and battery, an AC/DC converter transforms the energy to the high voltage level the battery needs. And since all 'normal' electronic components for infotainment, comfort, body and so on still often work on a standard 12V supply, the system also requires a powerful DC/DC converter that brings the high battery voltage down to the level required by devices such as light, trip computer, radio, power windows, dashboard displays etc.

These AC/DC and DC/DC power converters typically contain a relatively simple MCU driver circuitry and power electronic elements, explained Mnzer. According to Gartner, IGBTs are the key component for these converters, which leads to the assumption that the demand for these components will climb strongly.

The concept of high-voltage batteries calls for further modifications within the in-vehicle electronic landscape. First of all, the battery itself contains circuitry balancing the energy streams between the battery's cells and monitors the operating conditions. This circuitry embraces a MCU as well as discrete transistors and power MOSFETs, explained Mnzer.

The availability of a high-voltage circuit has stimulated the car designers' appetite for more changes. Functional units typically driven by mechanical parts and belts now can be driven electrically. Under a 12V supply this was not possible since their high power consumption would require very thick and thus expensive and heavy copper wires.

Mnzer cited the air conditioning compressor as an example. "With a power demand of several kilowatts, this compressor is normally driven directly by the car's engine by means of a belt transmission. Now it can be connected to the high-voltage circuit, which leads to increased efficiency," Mnzer said.

The highest additional semiconductor content within the electrified power train and will be found in the DC/DC converter and the motor control circuits. Since the electrical and kinetic power flow has to be balanced constantly and HEVs support a wide variety of operating modes and this is not a trivial task requiring relatively powerful microprocessors. The controller for the electric engine determines the driving characteristics of the car and thus executes a strategic task. "The two drives need to switch over seamlessly. This is where OEMs and tier ones can create the added value for their respective brand," Mnzer said.

Demand for power ICs
Market watchers and industry insiders agree that the advent of these alternative drives will lead to a disproportionately high increase in demand for power electronic components such as high-voltage MOSFETS or IGBTs.

HEV pioneer Toyota has developed its own IGBTs; most of the other car vendors and tier ones will have to buy these components from the market, which would bring vendors who offer the entire range of automotive electronics components, such as Infineon, into an advantageous position. Freescale, which currently has no power semiconductors in its portfolio, refers to its power component cooperation with STMicroelectronics. But "we are looking effectively for additional options," Osajda said.

NXP, too, does not offer power components. "We are focusing more on the charge management and see a huge potential in the analog/mixed signal parts used in the DC/DC and AC/DC converters," explained NXP's Sievers. "There we see the best possibilities to innovate."

According to many market watchers, Europe lags Asia in the development of hybrid drives and all-electrical cars, having focused over the past years to the optimization of the conventional internal combustion engine and associated components such as exhaust gas purification. From the perspective of the semiconductor industry, this is not necessarily a disadvantage.

Despite the high growth for HEVs and all-electric cars, conventional cars will continue to dominate the market and tighter legislation on emission control as well as the exigency to squeeze more kilometers out of every liter of gasoline will force automotive engineers to rely on more electronic helpers and on more sophisticated motor controls. Since many of these requirements can only be achieved with more complex software, the call for lowering emissions and improving fuel efficiency is driving a shift to 32bit MCUs, Gartner has found in a recent study. Along with more powerful microprocessors, embedded memory content in the cars will climb.

Also the optimization of electric loads within the car can contribute to that end. Sievers pointed out that the replacement of conventional incandescent bulbs with solid-state lighting is one more step in the right direction. Even assistants such adaptive cruise control (ACC) can cover this aspect. "We know that suboptimal speed behavior leads to increased fuel consumption," said Sievers. "If this factor is considered in the program of the ACC, it can optimize the fuel efficiency."

Others regard traffic management systems of which car-to-x communication is a part as a means to reduce the fuel consumption. Many measures can be implemented to this end, and many of them are agnostic as to the drive architecture. But more or less all of them require more chips in cars.

- Christoph Hammerschmidt
EE Times Europe

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