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Analog IC makes small engines green

Posted: 28 Aug 2009 ?? ?Print Version ?Bookmark and Share

Keywords:engine control unit? analog IC? ECU? microcontroller?

Freescale Semiconductor has introduced a new analog chip that could reduce emissions from small gasoline engines.

Using an engine control unit (ECU) with fuel injectors, instead of a carburetor, the analog MC33812 IC is said to cut emissions on one- and two-cylinder engines used for lawn mowers and scooters. "Small engines can produce as much pollution as 50 modern cars," said Kevin Anderson, Freescale's automotive analog product manager. "New regulations are designed to make a cleaner burn, like modern car engines, consuming as much of the fuel as possible in order to keep emissions down."

To help small engine makers meet stringent new emission regulations while also increasing fuel economy, Freescale designers created a chip to control all analog functions. The chip is said to bring small engine control on a par with auto engines. The MC33812 also allows small engine manufacturers to eliminate spark plugs, carburetor and distributors for spark coils, fuel injectors and the crank-position sensor.

Freescale estimates that electronic engine controllers can cut carbon monoxide emissions by up to 65 percent, hydrocarbons by up to 35 percent and nitrogen oxide by up to 35 percent compared to carburator systems. They also increase horsepower and improve gas mileage.

To meet these goals, Freescale used its SmartMOS analog process technology to eliminate a dozen discrete components and reduce ECU circuit board area. The MC33812 chip also combines a voltage regulator, fuel injector driver, ignition pre-driver along with a relay, lamp driver, watchdog timer and a reset generator.

"We have also designed both an evaluation board and a full-reference design board," said Jesse Beeker, a Freescale field applications engineer.

By adding an ECU to one- and two-cylinder engines, and switching to fuel injectors instead of a carburator, Freescale's analog chip is said to provide a 50-fold reduction in emissions. (Click on image to enlarge.)

The new analog IC, combined with a microcontroller to form an ECU, would allow small engine makers to replace mechanical carburetors with cleaner, more efficient electronic fuel injection for a wide range of outdoor power equipment.

In the U.S., these small engines account for an estimated 5 percent of air pollution. In emerging countries like China, which have a larger proportion of scooters plus motorized rickshaws, small engines generate large volumes of air pollution. According to the Union of Concerned Scientists, China generates the most carbon emissions in the world, followed by the United States.

Tougher regulations designed to cut emissions from outdoor equipment are being adopted around the world, including the U.S. Environmental Protection Agency. EPA Phase 3 standards are to be fully implemented for small engines in the U.S. by 2015. The new standard is expected reduce carbon and other emissions from small gasoline engines by 95 percent over 1997 totals.

- R. Colin Johnson
EE Times

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