For a power semiconductor manufacturer like International Rectifier
with a focus on power management devices, this competition between HEV and diesel is a neutral situation—because the common denominator between HEVs and diesel cars is high voltage. The hybrid powertrain as well as the direct fuel injection system need very rugged and robust high voltage power switches and driver ICs. So developing technology, capabilities and power management solutions to address the high voltage range >>100V is beneficial to both HEV and diesel applications.
Figures below show a simplified direct fuel injection system and the corresponding typical circuit diagram, respectively. High voltage is required to drive the piezo elements inside of the very precisely tailored fuel injectors. Those high tech injectors inject fuel often up to seven times per second in order to precisely tailor the fuel charge inside of the engine cylinders to an optimized gas phase. Distribution and gas density play an important role by optimizing the combustion process to the various power requirements in the driving cycle of the car.
New activities of various car manufacturers target introducing this high pressure direct fuel injection concept into gasoline engines as well, simultaneously boosting fuel efficiency and reducing emissions. Power switches like so called IGBTs play a key role in such an application. They provide efficient power management and precise control over the piezo actuators in conjunction with optimized high voltage driver ICs, which need to be capable of driving the high voltage switches in a safe and reliable way.
An additional benefit
One important benefit of diesel engines has not yet been mentioned. It should be noted that the high fuel efficiency of HEVs is more or less a theoretical value that significantly depends on driving style. Unless the driver is adjusting his driving behavior to a very moderate use of the gas pedal in order to avoid the use of the inefficient gasoline engine, the HEV fuel performance can be much worse than stated and become closer to a less efficient gasoline combustion engine.
On the other hand a diesel engine is always very efficient by itself, what one could call a more “passive fuel efficiency concept” then the HEV philosophy, which relies on the driver maximizing the usage of the electric powertrain versus the gasoline motor. The performance data of the newest diesel generations suggest a much smaller dependency on the driver’s style. The motor control unit optimizes the fuel consumption to the current driving situation, which helps to achieve a high mileage independent of driver or driving conditions.
Diesel engines in well-developed countries can provide some threat to the penetration and growth of the hybrid-electric vehicle market. With diesel fuel supply infrastructure in place, attractive price, and excellent performance and efficiency, diesel cars can become a major game changer in countries where diesel is not yet very well established—like the U.S.
Henning Hauenstein is VP and general manager of the Automotive Products Business Unit at International Rectifier.