El Segundo, Calif. - The relentless drive for greater fuel efficiency will come into play again in 2003, as automakers and their suppliers lay the groundwork for the automotive industry's next great challenge: the introduction of the integrated starter-alternator (ISA).
At least one company, International Rectifier here, has begun blazing the trail toward the ISA, and more are expected to follow in 2003 and 2004. International Rectifier recently rolled out its Active Integrated Rectifier Regulator, which boosts power by using active, rather than passive, rectification. The device is already being incorporated in the recently introduced Maybach, an ultraluxury vehicle produced by DaimlerChrysler.
General Motors Corp. will also give the trend a boost when it rolls out a parallel-hybrid truck in 2004 that will employ an integrated starter-generator to provide 20-amp ac power for use with power tools and other electrical appliances.
Engineers say that the ISA has huge implications for the future of the automotive industry. It's expected to serve as an enabler for the inevitable move to 42-volt electrical architectures, which will take place over the next decade. It's also the key to generating more electrical power for future drive-by-wire systems, such as steer-by-wire and brake-by-wire.
Most of all, though, integrated starter-alternators are viewed as an important step forward in automotive fuel efficiency. The ISA allows engineers to endow future vehicles with a so-called "start-stop" feature, which quietly shuts down the engine while vehicles wait at traffic lights, and then quickly restarts it when the light changes.
"Car companies want to adopt these new systems, but there's a 'catch-22,' " said Alex Lidow, chief executive officer of International Rectifier. "They can't put in the new systems to save the gas until there's enough electricity to run the systems."
International Rectifier, however, is starting down the road to the ISA by launching its Active Integrated Rectifier Regulator. The AIRR is said to reduce power losses and increase overall efficiency by replacing traditional, passive diodes with active field-effect transistors.
The unit combines the active rectifier with a voltage regulator in a single module that controls the output voltage of a car's alternator. In converting the alternating current from the alternator to direct current for use by a vehicle's battery, it is said to provide about 25 percent more efficiency at idle. "The old-style claw-pole generator and diode alternator is a fairly inefficient way to generate electricity," Lidow said. "By using the Active Integrated Rectifier Regulator, vehicles all of a sudden get a big increase in efficiency at idle."
Initial production units of the AIRR will work in tandem with very large alternators. The large alternators typically have 350-amp output at 6,000 crankshaft revolutions per minute, and above 200-A output at idle. The module is capable of handling 525 A for 20 seconds, IR engineers said.
The company's executives pointed out that the AIRR doesn't provide the same advantages as an integrated starter-alternator; it merely provides an efficiency boost over conventional alternators. The ISA, they said, is still several years away.
Future steps along the path to the ISA include the development of ASICs and digital signal processors for communications features that will enable "smart" electrical systems to shed unnecessary loads. Eventually, engineers will have to develop bidirectional motors and controllers for the integration of alternators with vehicle starters.
"We've got to solve the auto industry's efficiency problems one step at a time," Lidow remarked.
Industry engineers also point out that starter-alternators and starter-generators will require a new set of power MOSFETs to handle the higher voltages associated with them. Power semiconductors such as Infineon Technologies' OptiMOS, a MOSFET family of components that is designed for motor control, provide a solution for starter-alternators.
Infineon engineers said that OptiMOS devices with 75-volt breakdown voltages will be needed for use with the bidirectional motors employed by starter-alternators. The OptiMOS products are priced at $2.20 in volumes of 10,000.
A number of other semiconductor suppliers, including Analog Devices (Norwood, Mass.), Fujitsu Microelectronics (San Jose, Calif.) and Motorola Semiconductor Products Sector (Phoenix) are also producing devices aimed at 42-V architectures, which will eventually go hand in hand with integrated starter-alternators.
"This is all part of the 42-volt platform," said Shawn Slusser, senior manager of marketing for power semiconductors at Infineon Technologies Corp. (San Jose, Calif.). "We see the starter-generator as a catalyst for the introduction of 42-volt systems."
Engineers said that even as ISA-equipped vehicles from GM, DaimlerChrysler and Toyota begin to hit the streets in 2003, they will continue to push the technological envelope during the next decade. The changeover to ISA, they said, will not occur quickly. "It's a pretty big leap for a car company to go from what they have been doing for the past 50 years to an integrated starter-alternator," Lidow said. "For this to happen, we're going to have to create a smooth path of incremental solutions."