To reduce vehicle power consumption and increase efficiency, start at the charging system

October 28, 2011 // By Jean-Philippe Meunier and David Lopez, Freescale Semiconductor
One of today's major challenges for carmakers is improving the fuel efficiency to reduce the vehicle's fuel consumption and its carbon footprint. The efforts to achieve greater efficiency need to start at the charging system, our authors say - key element is a new alternator regulator IC.

One of today's major challenges for carmakers is improving the fuel efficiency to reduce the vehicle’s fuel consumption and its carbon footprint. Among the reasons for placing a high priority on improved fuel consumption are (1) taking advantage of tax incentives offered by regional governments for low emission vehicles and/or (2) avoiding increased taxes and fines for inefficiency and high fuel consumption vehicles. To meet the goals being established by governments in many regions of the world, all the stops must be pulled out. As a result, every vehicle system is expected to contribute towards improved efficiency. A recently released alternator regulator integrated circuit (IC) provides improved control allowing the charging system to do its part towards achieving greater efficiency. With its Local Interconnect Network (LIN ) 1.3 interface, the IC enables simplified, standardized and robust communications with the engine control unit (ECU).

The alternator provides the source of power for vehicle loads and charging the vehicle’s battery. With diode rectification, a typical belt-driven claw-pole automotive alternator has limited efficiencies. Improved slot fill techniques for the stator windings can improve some production alternators from +15% up to +20% efficiency ranges. In addition, the synchronous rectifier, brushless dc machines used in starter-alternators in stop-go systems can add efficiencies of +10%, according to automotive market. Both of these improvements come at increased cost and are not typical of the vast majority of automotive alternators. Still, improving the charging system’s efficiency is a highly desirable goal.

From a systems perspective, one means of improving the efficiency and reducing the energy consumption involves improved control. Typically, a conventional analog voltage regulator simply increases or decreases the amount of rotor current and provides a voltage to an indicator lamp if there is a problem as well as a signal to a microcontroller (MCU). Using the low-cost LIN protocol, the alternator regulator can be interfaced to an ECU that manages the charging system to improve operation

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