Abstract
KEYWORDS:
DC Servomotor, Brushless DC Motor (BLDC), Power ICs
ABSTRACT:
Modern cars are equipped with an increasing number of electric motors (more than 60 to upper classes), destined, both, for basic and vital functions of the car and for the driver's and passengers' comfort.
The paper presents, in its first part, a brief description of the types and principles of DC
motors used in automotive and the problems involved by their control. The classical DC servomotor, with mechanical commutation, is presented first. It remains still the most used DC motor in automotive. Some limitations of this motor include brush replacements, brush run-in after replacement, brush arc RFI (radio frequency
interference) and voltage/current limitations. The construction of the DC servomotor also requires the commutator to rotate. This means the armature windings must rotate as well which results in high inertia and poor thermal situation, because the heat from losses is primarily generated in the rotor. Higher dynamic performances are achieved using electronically commutated or brushless motors. The principles of such motors are briefly presented.
The main part of the paper is devoted to the description of some representative types of Integrated Circuits (ICs) used for control. All ICs presented in the paper are produced by ST-Microelectronics, and have been chosen, because they cover the whole range, from simple power ICs to super-smart power ICs.
The presentation starts with a power IC - TD340, a H-bridge power MOSFET driver for DC motor control. The circuit is suitable for automotive drives, because it withstands transients, as met in this field, without special protection devices thanks to its 60 V BCD technology. Another IC, briefly described in the paper, is L9904, a control circuit for power MOS bridge driver in automotive applications. It includes an ISO 9141
compatible interface.
The control of brushless DC motors implies smart and super smart ICs (8-32 bit microcontrollers), able to measure the Back-EMF voltages or use information from Hall sensors and current sensors in order to generate corresponding PWM signals. A smart power circuit able to control a BLDC, based on position sensor information is the L6229, a DMOS fully integrated three-phase motor driver with overcurrent protection. A circuit briefly presented in the paper, which controls a DC motor by measuring the Back-EMF voltages, is ST72141K, an 8-bit microcontoller with electric motor control, ADC, 16-bit timers and SPI interfaces.
Some final considerations refer to ICs equipped with CAN interfaces.
The paper is based on the author's experience in using stepper motors and DC motor drives in mechatronic systems.